542 Rethinking/reexamining Grand Challenges Within Teaching for Workforce Readiness – a Scorecard and Recalibration

The ASAS Public Policy Committee (PPC) provides updates of Grand Challenges (GCs; www.asas.org/about/public-policy/asas-grand-challenges) which clearly articulate research priorities while providing science-based information for shaping public policy, and to enhance future funding for research and education programs in animal sciences (AS). In this nexus symposium for 2021, PPC examines previous stated priorities and provides a progress report card and offers additional perspectives and recommendations for research needed to address some of the GCs continuing to face animal agriculture. Among the GCs is teaching for workforce readiness (WR) as the preparation of graduates for diverse roles in the modern workforce has provoked substantial research in recent years. Ensuring new and returning workplace entrants are prepared to enter the workforce with requisite knowledge, skills, abilities, and experiential attributes required in a diverse array of occupations is a GC. Through an examination of the past, present and future instructional landscape, we will examine a gap which exists between WR and expectations of future employers. Expected employee competencies will include critical thinking and problem solving, mastery of human relationship skills and leadership mindsets, diverse and effective communication abilities, influence skills and workplace emotional intelligence. Instructive to meeting the GC are principles identified in ASAS Accreditation Standards for Animal Science Programs. Those standards strive to ensure graduates can communicate the importance of animal agriculture and STEM biology to an increasingly non-ag world. Among the GC of providing experiences are increased emphasis on high-impact programming around internships, externships and apprenticeships layered onto a knowledge, scaffolded curriculum. Use of research methodology to develop and incorporate into practice varied instructional modalities, technologies and practices within a dynamic higher education landscape requires intentional, systematic, and iterative scholarly approaches; which will enable creation of adaptive learning experiences and learning outcomes needed for an ever-changing workplace with its unique challenges and opportunities.

Changes in Cytochrome P450 in Katahdin Ewes Fed Endophyte-infected Tall Fescue Seed Diets in Spring and Fall

Objective was to examine the activity of cytochrome P450 (CYP), a liver enzyme that metabolizes ergot alkaloids which is hindered by this fescue toxin, as an indicator of fescue toxicosis in sheep. In spring and fall, ewes were blocked by age and BW, and randomly assigned to 1 kg/ewe/d of endophyte-infected (E+; 61% of diet in fall, 13% of diet in spring; 0.8 µg/g of ergovaline; and soy hulls, alfalfa pellets, cottonseed hulls, molasses) or non-infected (E-; same proportion of E+/season and same feeds) tall fescue seed supplement (n = 10/diet in each season) for 28 d, plus hay, mineral and water. Ewes were exposed to teaser, d -21 to 0, and intact rams, d 0 (first day of diet) to 30. Rectal temperature (RT), serum concentration of prolactin (using RIA), and CYP were determined every 7–14 d between d 0–28, and pregnancy status on d 56. PromegaTM P450-Glo assay was used to determine CYP from serum. Data were analyzed by using PROC MIXED with repeated measures (SAS). Rectal temperature of E+ compared with E- ewes was elevated on at least one day in fall and spring (diet × season × d, P < 0.001). Serum prolactin was lower in E+ compared with E- ewes (diet × d, P < 0.001) and lower in fall (P < 0.001). CYP was higher in E- ewes on d 28 in fall (diet × season × d, P = 0.008), but otherwise similar between diets, and higher in fall than spring (P < 0.001). There was an unexpected negative correlation between CYP and prolactin (R = -0.24; P < 0.009), but there appears to be a subpopulation of ewes with low prolactin and lower CYP. CYP activity in sera may not be a marker for fescue toxicosis in ewes.

Relationships among ergot alkaloids, cytochrome P450 activity, and beef steer growth

Determining a grazing animal's susceptibility to ergot alkaloids has been a research topic for decades. Our objective was to determine if the Promega™ P450-Glo assay could be used to indirectly detect ergot alkaloids or their metabolites in urine of steers. The first experiment validated the effects of ergot alkaloids [0, 20, and 40 μM of ergotamine (ET), dihydroergotamine (DHET), and ergonovine (EN)] on human CYP3A4 using the P450-Glo assay (Promega™ V9800). With this assay, luminescence is directly proportional to CYP450 activity. Relative inhibition of in vitro cytochrome P450 activity was affected (P < 0.001) by an interaction between alkaloids and concentration. That interaction resulted in no concentration effect of EN, but within ET and DHET 20 and 40 μM concentrations inhibited CYP450 activity when compared with controls. In experiment 2, urine was collected from Angus-sired crossbred steers (n = 39; 216 ± 2.6 days of age; 203 ± 1.7 kg) after grazing tall fescue pastures for 105 days. Non-diluted urine was added to the Promega™ P450-Glo assay, and observed inhibition (3.7 % ± 2.7 of control). Urine content of total ergot alkaloids (331.1 ng/mg of creatinine ± 325.7) was determined using enzyme linked immunosorbent assay. Urine inhibition of CYP450 activity and total alkaloids were correlated (r = −0.31; P < 0.05). Steers were genotyped at CYP450 single nucleotide polymorphism, C994G. Steer genotype affected (P < 0.03) inhibition of CYP450 activity by urine; heterozygous steers had the least amount of CYP450 inhibition suggesting that genotyping cattle may be a method of identifying animals that are susceptible to ergot alkaloids. Although, additional research is needed, we demonstrate that the Promega™ P450-Glo assay is sensitive to ergot alkaloids and urine from steers grazing tall fescue. With some refinement the P450-Glo assay has potential as a tool for screening cattle for their exposure to fescue toxins.

Forage and breed effects on behavior and temperament of pregnant beef heifers

BACKGROUND

Integration of behavioral observations with traditional selection schemes may lead to enhanced animal well-being and more profitable forage-based cattle production systems. Brahman-influenced (BR; n = 64) and Gelbvieh × Angus (GA; n = 64) heifers consumed either toxic endophyte-infected tall fescue (E+) or one of two nontoxic endophyte-infected tall fescue (NT) cultivars during two yr. Heifers were weighed at midpoint and termination of grazing. Grazing behavior (grazing, resting in the shade, lying, or standing without grazing) was recorded (n = 13 visual observations per yr in June and July) for each pasture. During yr 2, exit velocity (EV) and serum prolactin (PRL) were determined.

RESULTS

Grazing behavior was influenced (P < 0.05) by an interaction between fescue cultivar and breed type. Gelbvieh × Angus heifers assigned to E+ pastures had the lowest percentage of animals grazing and the largest percentage of animals resting in the shade. Brahman-influenced heifers had faster EV (P < 0.001) than GA heifers (0.52 vs. 0.74 ± 0.04 s/m, respectively). Body weight (BW) was affected (P < 0.01) by an interaction of tall fescue cultivar and d, and an interaction of tall fescue cultivar and breed type. Heifers grazing NT pastures were heavier (P < 0.01) than heifers grazing E+ pastures at midpoint and termination. Gelbvieh × Angus heifers grazing NT pastures were heavier (P < 0.01) than GA and BR heifers grazing E+ and BR heifers grazing NT pastures. An interaction of forage cultivar and breed type occurred on serum PRL (P < 0.01).

CONCLUSION

Collectively fescue cultivar, EV, and concentrations of serum PRL were associated with grazing behavior. Heifers grazing NT pastures were observed to be grazing more than heifers assigned to E+ pastures, regardless of breed type, which may have contributed to changes in BW and average daily gain (ADG) in heifers. Integration of behavioral observations along with traditional selection schemes may lead to enhanced animal well-being and more profitable forage-based cattle production systems.

Performance by spring and fall-calving cows grazing with full, limited, or no access to toxic Neotyphodium coenophialum-infected tall fescue

Replacing toxic, wild-type Neotyphodium coenophialum-infected tall fescue (E+) with nontoxic, N. coenophialum-infected tall fescue (NE+) has improved cow performance, but producer acceptance of NE+ has been slow. The objective was to compare performance by spring- and fall-calving cows grazing either E+ or NE+ at different percentages of the total pasture area. Gelbvieh×Angus crossbred cows (n=178) were stratified by BW and age within calving season and allocated randomly to 1 of 14 groups representing 5 treatments for a 3-yr study: i) Fall-calving on 100% E+ (F100); ii) Spring-calving on 100% E+ (S100); iii) Fall-calving on 75% E+ and 25% NE+ (F75); iv) Spring-calving on 75% E+ and 25% NE+ (S75); and v) Spring-calving on 100% NE+ (SNE100). Groups allocated to F75 and S75 grazed E+ until approximately 28 d before breeding and weaning, then were then moved to their respective NE+ pasture area for 4 to 6 wk; those allocated to F100, S100, and SNE100 grazed their pastures throughout the entire year. Samples of tall fescue were gathered from specific cells within each pasture at the time cows were moved into that particular cell (∼1 sample/mo). Blood samples were collected from the cows at the start and end of the breeding season. Stocking rate for each treatment was 1 cow/ha. Forage IVDMD, CP, and total ergot alkaloid concentrations were affected (P<0.05) by the treatment×sampling date interaction. Hay offered, cow BW, and BCS at breeding, end of breeding, and at weaning were greater (P<0.05) from fall-calving vs. spring-calving. Cow BW at weaning was greater (P<0.05) from F75 and S75 vs. F100 and S100. The calving season×NE+ % interaction affected (P<0.05) calving rates. Preweaning calf BW gain, actual and adjusted weaning BW, ADG, sale price, and calf value at weaning were greater (P<0.05) from fall-calving vs. spring-calving and from SNE100 vs. S75 except for sale price which was greater (P<0.05) from S75 vs. SNE100. Cow concentrations of serum prolactin at breeding and serum NEFA at the end of breeding were affected (P<0.05) by the calving season×NE+ % interaction. Serum Zn and Cu concentrations from cows were affected (P<0.05) by calving season. A fall-calving season may be more desirable for cows grazing E+, resulting in greater calving rates, cow performance, and calf BW at weaning, whereas limited access to NE+ may increase calving rates, serum prolactin, and NEFA concentrations during certain times in the production cycle, particularly in spring-calving cows.

Effects of forage type, body condition and single-nucleotide polymorphisms in the bovine cytochrome P450 regulatory region on cow productivity

Single-nucleotide polymorphisms (SNP) in the coding sequence of cytochrome p450 (CYP3A28) have been associated with milk yield and composition, and calving traits in cows. In this study, we aimed to determine whether (i) the CYP3A28 regulatory region was polymorphic and (ii) SNP genotype, forage type, body condition and their interactions affect cow productivity. Primers for CYP3A28 promoter were designed to amplify a 483-bp segment by PCR. Amplicon sequences revealed seven SNP (T-318C, T-113A, C-189T, T-78G, A6G, G17A and T21C) in Brahman (38 cows), Brahman x Angus reciprocal crosses (47 cows) and crossbreds (98 cows). Angus cows (n = 41) appeared to be fixed at those SNP locations. Genotype and forage {endophyte-infected tall fescue [KY+; Lolium arundinaceum (Schreb.) S. J. Darbyshire] vs. bermudagrass [Cynodon dactylon (L.) Pers.]} effects on lifetime (8-years) calving rate, and calf weaning weights and heights were determined in Herd 1 (126 cows); genotype and BC (low vs. moderate) effects on calving date and calving percent were determined in Herd 2 (98 cows). Four SNP (T-318C, T-113A, A06G and T21C) appeared to be related to cattle productivity, CC cows at T-318C having a lower (p < 0.05) lifetime calving rate than TC or TT cows (65%, 85% and 81% respectively). Cows that grazed KY+ and were TT at T-318C produced calves that tended (p < 0.07) to weigh less than their contemporaries. Moreover, calves of TT cows were shorter (p < 0.05) at weaning than calves of CC or TC cows. In Herd 2, moderate-BC cows that were TT or AA at T-318C, T-113A, T-78G, A6G and T21C had greater (p < 0.05) calving rates (74-80%) than heterozygous cows (46-60%), and low-BC cows that were AA at G17A calved at least 6 days earlier (p < 0.05) than heterozygous cows. Our findings suggest that SNP in the CYP3A28 regulatory region of Brahman-influenced cows are associated with cattle productivity.

Effects of bovine cytochrome P450 single-nucleotide polymorphism, forage type and body condition on production traits in cattle

Relating single-nucleotide polymorphisms (SNP) to cows with acceptable productivity could benefit cattle breeders in areas where tall fescue is the predominant forage. This study aimed to (i) identify SNPs in bovine cytochrome P450 3A28 (CYP3A28) and (ii) determine the associations between SNP genotype, forage and cow body condition (BC). Genotype (CC, CG or GG) and forage [Kentucky-31 wild-type endophyte-infected tall fescue (KY+) vs. bermudagrass] effects on milk volume and quality were determined in Herd 1 cows (123 cows); in Herd 2 (99 cows), genotype and BC (low vs. moderate) effects on ovarian follicle size, calving date and calving per cent were determined; and in Herd 3 (114 cows), effects of genotype and fescue cultivar [KY+ vs. non-toxic endophyte-infected tall fescue (HiMag4)] were related to calving per cent, calving date and weaning weights of both cow and her calf. A cytosine (C) to guanine (G) transversion at base 994 (C994G) in CYP3A28 was identified. There was a genotype × forage type interaction (p < 0.05) on milk protein in Herd 1 cows; CC cows grazing bermudagrass had greater milk protein percentage in relation to other cows in the herd. In Herd 2, BC and genotype × BC tended (p < 0.10) to influence follicle size and Julian calving date respectively. Diameter of the largest follicle tended to be larger in moderate BC than in low-BC cows; whereas, CC and CG cows in moderate BC and homozygous (CC and GG) cows in low BC tended to calve 14 days earlier in relation to CG cows in low BC. In Herd 3, there was a genotype × forage type interaction (p < 0.05) on calving per cent, Julian calving date and calf weaning weight. In this study, genetic alterations (G allele at C994G) coupled with nutritional factors (low BC and toxic tall fescue) resulted in overall lower productivity in cows.

Effects of body condition on measures of intramuscular and rump fat, endocrine factors, and calving rate of beef cows grazing common bermudagrass or endophyte-infected tall fescue

Multiparous beef cows were managed to achieve marginal (BCS = 4.7 ± 0.07; n = 106) or good (BCS = 6.6 ± 0.06; n = 121) body condition (BC) to determine the influence of forage environment on BW and BC changes, intramuscular fat percentage (IMF), rump fat (RF), and serum hormones during 2 yr. Cows within each BC were randomly assigned to graze either common bermudagrass (CB; n = 3 pastures/yr) or toxic endophyte-infected tall fescue (EI; n = 3 pastures/yr) during a 60-d breeding season. Blood samples were collected at d 0, 30, and 60 of the breeding season, and serum concentrations of prolactin (PRL), IGF-I, and cortisol (CORT) were quantified; PRL and progesterone (P(4)) also were quantified 10 d before the breeding season (d -10). Body weight and BCS were recorded during the breeding season (d 0, 30, and 60). Cow IMF and RF were measured via ultrasonography at the start and end of the breeding season. Cows with increased (>1 ng/mL) P(4) at the beginning of the breeding season (cyclic) had greater (P < 0.02) concentrations of PRL on d 30 and 60 compared with anestrous cows. A forage environment × BC interaction tended (P = 0.07) to influence PRL. Cows grazing CB independent of BC had increased PRL compared with cows grazing EI. Prolactin was decreased in good-BC cows grazing EI compared with cows grazing CB, and cows in marginal BC grazing EI had the least concentrations of PRL. Concentrations of IGF-I were similar (P > 0.10) among good- and marginal-BC cows grazing CB, as well as good-BC cows grazing EI; however, marginal-BC cows grazing EI had reduced (P < 0.04) concentrations of IGF-I compared with all other groups. Cows in marginal BC grazing CB gained (P = 0.02) the most BW during the breeding season, whereas good-BC cows grazing EI gained the least amount of BW. Marginal-BC cows grazing CB tended (P = 0.06) to increase BC during the breeding season, whereas good-BC cows grazing either CB or EI lost BC. Rump fat tended (P = 0.07) to increase during the breeding season in marginal-BC cows compared with cows in good BC. Calving rates were similar (P > 0.10) among good- (82%) and marginal- (84%) BC cows grazing CB, and good-BC cows grazing EI (79%); however, marginal-BC cows grazing EI had a reduced (P = 0.04) calving rate (61%). Cattle grazing EI during the breeding season lost BC. That reduction in BC may be communicated to the pituitary via hormones that include IGF-I or PRL or both, resulting in decreased calving rates.

Influence of body condition and forage type on prevalence of Escherichia coli O157:H7 and Salmonella in grazing beef cows

AIM

To determine the influence of body condition (BC) and forage type on the prevalence of faecal shedding of Escherichia coli O157:H7 and Salmonella from beef cows.

METHODS AND RESULTS

Thin or moderately conditioned cows (n = 115) were randomly assigned to graze either common bermudagrass (n = 3 pastures) or toxic endophyte-infected tall fescue (n = 3 pastures) for 62 days. Faecal samples were collected on day 0, 30 and 62. Overall percentage of faecal samples positive for E. coli O157:H7 was 2.6% and 2.0% for Salmonella. Percentage of cows positive for both E. coli O157:H7 and Salmonella on at least one occasion was 6.1%. BC, forage type or the interaction did not influence the prevalence of E. coli O157:H7 or Salmonella in the faeces of cows.

CONCLUSIONS

BC at initiation of the grazing period or loss of BC in moderate conditioned cows during the grazing period did not influence faecal shedding of E. coli O157:H7 or Salmonella. Consumption of either forage type did not influence faecal shedding of either E. coli O157:H7 or Salmonella in beef cows of thin or moderate BC.

SIGNIFICANCE AND IMPACT OF THE STUDY

Change in BC that typically occurs during the normal production cycle in grazing cows did not influence faecal shedding of pathogenic bacteria regardless of forage type.

Involvement of signaling pathways in bovine sperm motility, and effect of ergot alkaloids

There is evidence that ergot alkaloids can directly interact with mammalian spermatozoa affecting sperm functions. Ergot alkaloids exert their toxic or pharmaceutical effects through membrane receptor-mediated activities. This study investigated the signaling pathways involved in the in vitro inhibitory effects of both ergotamine (ET) and dihydroergotamine (DEHT) on the relative motility of bovine spermatozoa using specific inhibitors. Motile bovine spermatozoa were prepared using a Percoll gradient and incubated with ergot alkaloids with and without signaling pathway inhibitors. Co-incubation of ET or DHET with 100 microM prazosin (alpha 1-adrenergic receptor inhibitor) decreased (p < 0.05) relative motility of spermatozoa when compared with controls. In addition, preincubation of spermatozoa with 10 or 20 microM prazosin and DHET also reduced (p < 0.05) the number of motile spermatozoa. Relative sperm motility (motility of treated spermatozoa normalized to control sperm motility) was increased (p < 0.05) when co-incubations included ET and yohimbine (alpha 2-adrenergic receptor inhibitor); conversely, co-incubation of yohimbine (100 microM) and DHET decreased (p < 0.05) the percentage of motile spermatozoa when compared with controls. Pertussis toxin and cholera toxin (effectors of inhibitory and stimulatory G-proteins, respectively) altered (p < 0.05) relative sperm motility in a concentration dependent manner; however, co-incubation of pertussis or cholera toxin with ergot alkaloids had no interactive (p = 0.83) effects on the relative motility of spermatozoa. Co-incubation of Rp-cAMP (a membrane-permeable cAMP inhibitor) with 50 microM DHET had no effect (p > 0.05) on relative sperm motility; whereas, the co-incubation of 22.4 or 44.8 microM Rp-cAMP with 50 microM ET increased (p < 0.05) the percentage of motile spermatozoa when compared with 0 or 224 microM Rp-cAMP (49%, 65%, 59%, and 54%, respectively, for 0, 22.4, 44.8, and 224 microM of Rp-cAMP. An interaction between BAPTA-AM (a chelator of intracellular calcium) and alkaloids also impacted (p < 0.05) relative sperm motility. Generally, co-incubating spermatozoa with BAPTA-AM and ET increased the percentage of motile spermatozoa; however, co-incubation with DHET decreased relative sperm motility except with 41 microM BAPTA-AM. Collectively, these observations suggest that ET and DHET decreased the percentage of motile bovine spermatozoa via alpha adrenergic receptors. However, the second messenger systems involved with ergot alkaloid inhibition of relative motility of bovine spermatozoa remain to be elucidated.

Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls

Sixteen (mean age = 1.1 +/- 0.1 yr; mean BW = 478 +/- 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P < 0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 +/- 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P < 0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P < 0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P < 0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P < 0.06) in August than July. Concentrations of cortisol and testosterone were not (P > 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.

Effects of fescue type and sampling date on the nitrogen disappearance kinetics of autumn-stockpiled tall fescue

Two tall fescue [Lolium arundinaceum (Schreb.) Darbysh] forages, one an experimental host plant/endophyte association containing a novel endophyte that produces low or nil concentrations of ergot alkaloids (HM4) and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56 kg/ha of N to assess N partitioning and ruminal disappearance kinetics of N for these autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361 +/- 56.4-kg replacement dairy heifers were stratified by weight and breeding, and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh pasture strip (December 26, January 15, and February 4), and when the study was terminated (February 26). Generally, fescue type and the fescue type x sampling date interaction exhibited only minor effects on total forage N, or partitioning of N within the cell solubles or the cell wall. For pregrazed forages, concentrations of N and N partitioned within the cell solubles both declined in a strongly linear relationship with sampling dates. In contrast, concentrations of cell-wall-associated N changed in erratic and often higher-ordered relationships with time, but the magnitude of these responses generally was limited. Unlike the partitioning of N within cell-wall and cell-soluble fractions, kinetic characteristics of ruminal N disappearance frequently exhibited interactions of fescue type and sampling date. For pregrazed forages, these included interactions for all response variables, and for postgrazed forages, fractions B and C, as well as rumen degradable protein. Ruminal disappearance rate for pregrazed E+ and HM4 exhibited quadratic (range = 0.057 to 0.082/h) and cubic (range = 0.057 to 0.075/h) relationships with time, respectively. For postgrazed E+ and HM4 forages, ruminal disappearance rate was unaffected (mean = 0.066/h) or only tended to be affected by sampling date (mean = 0.065/h), respectively. Concentrations of rumen degradable protein exhibited various curvilinear relationships with sampling dates, but disappearance was consistently extensive, and the overall range was relatively narrow (71.3 to 78.9% of N). These findings suggest that ruminal disappearance of N for autumn-stockpiled tall fescue forages remains extensive throughout the winter months and is only affected minimally by fescue type, sampling date, and grazing status.

Effects of Fescue Type and Sampling Date on the Ruminal Disappearance Kinetics of Autumn-Stockpiled Tall Fescue

Two tall fescue (Festuca arundinacea Schreb.) forages, one an experimental host plant/endophyte association containing a novel endophyte (HM4) that produces low or nil concentrations of ergot alkaloids, and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56 kg/ha of N to assess the nutritive value and ruminal disappearance kinetics of autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361 +/- 56.4-kg replacement dairy heifers were stratified by weight and breeding and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh strip (December 26, January 15, and February 4), and when the study was terminated (February 26). For fiber components, there were no interactions between fescue type and sampling date for either pregrazed or postgrazed forages. Over sampling dates, neutral detergent fiber (NDF; 56.5 to 67.8%), acid detergent fiber (27.7 to 34.9%), hemicellulose (28.8 to 34.0%), cellulose (25.0 to 28.1%), and lignin (3.61 to 10.05%) varied with sampling date, but patterns were almost exclusively curvilinear with time. Ruminal disappearance rate of dry matter (DM) was not affected by any treatment factor (overall mean for both pregrazed and postgrazed forages = 0.050 h(- 1)); similar responses were observed for NDF disappearance (overall mean = 0.048 h(- 1)). Interactions of fescue type and sampling date were observed for both pregrazed and postgrazed forages with respect to effective ruminal disappearance of DM; however, estimates were relatively high for all forages (overall mean = 64.0%). Effective disappearance of NDF was relatively extensive for all forages (overall mean = 55.4% of NDF). Based on the results of this trial, the endophyte status of stockpiled tall fescue forages had little practical effect on forage nutritive value and kinetics of ruminal DM or NDF disappearance. Overall, autumn-stockpiled tall fescue forages would appear to be a legitimate and lower cost alternative to harvested forages, and appear to possess suitable nutritional characteristics for developing dairy heifers in the Ozark Highlands.

Influence of body condition and bovine somatotropin on estrous behavior, reproductive performance, and concentrations of serum somatotropin and plasma fatty acids in postpartum Brahman-influenced cows1,2

Ninety-nine multiparous Brahman-influenced (1/4 to 3/8 Brahman) cows were managed to achieve low (BCS = 4.3 +/- 0.1; n = 50) or moderate (BCS = 6.1 +/- 0.1; n = 49) body condition (BC) to determine the influence of bovine somatotropin (bST) on estrous characteristics, reproductive performance, and concentrations of serum GH and plasma NEFA. Beginning 32 d postpartum, cows within each BC were assigned randomly to treatment with or without bST. Non-bST-treated cows received no treatment, and treated cows were administered bST (Posilac, 500 mg s.c.) on d -35, -21, and -7 before initiation of the breeding season. On d -7, all cows received an intravaginal, controlled internal drug-releasing (CIDR) device. On d 0 (initiation of the 70-d breeding season), the CIDR were removed and cows received prostaglandin F2alpha (PGF2alpha). Blood samples were collected from the median caudal vein of the cows at each bST treatment and at d -28 and 0. Estrous behavior was monitored by radiotelemetry during the first 30 d of the breeding season. Growth hormone was increased (P < 0.05) in low and moderate BC cows treated with bST. The percentage of cows detected in estrus during the first 30 d of the breeding season was decreased (P = 0.05) for low BC (64%) compared with moderate BC (82%) cows. The interval to first estrus tended (P = 0.07) to be shorter in low BC-bST-treated cows (3.7 +/- 1.9 d) than in moderate BC-bST-treated cows (9.6 +/- 1.8 d). During the first 30 d of the breeding season, cows in low BC had a decreased (P = 0.02) number of mounts received and increased (P = 0.001) quiescence between mounts compared with cows in moderate BC. The number of mounts received was reduced (P = 0.04) in bST-treated cows. More (P = 0.02) cows treated with bST became pregnant during the first 3 d of the breeding season compared with non-bST-treated cows. The cumulative first-service conception rate tended (P = 0.07) to be greater for bST-low BC cows than non-bST-treated cows in low or moderate BC. On d 0, NEFA were greater (P < 0.05) in bST-treated vs. non-bST-treated cows. Low BC and bST reduced the intensity of behavioral estrus in postpartum Brahman-influenced cows. However, bST increased the first-service conception rate during the first 30 d of breeding and pregnancy rates during the first 3 d of breeding in postpartum Brahman-influenced cows.

Influence of dietary endophyte (Neotyphodium coenophialum)-infected tall fescue (Festuca arundinacea) seed on fecal shedding of antibiotic resistance-selected Escherichia coli O157:H7 in ewes

The objectives were to determine the effects of short-term feeding of a toxic endophyte (Neotyphodium coenophialum)-infected tall fescue seed (Festuca arundinacea, cultivar 'Kentucky 31') on fecal shedding and intestinal concentrations of Escherichia coli O157:H7 and the concentrations of prolactin, cortisol, and NEFA in experimentally inoculated ewes. Twelve ewes (mean BW = 46 +/- 2 kg) were fed a diet containing either high endophyte-infected (HI-E) or low endophyte-infected (LO-E) tall fescue seed for 7 d. Each diet consisted of 50% (as-fed basis) tall fescue seed. Ewes were experimentally inoculated with antibiotic resistance-selected E. coli O157:H7 on d 1 of the feeding treatment, and fecal shedding of inoculated pathogens was monitored daily on d 2 to 6. On d 7, ewes were weighed and euthanized, and tissues and contents were sampled from the ileum, cecum, and rectum for quantitative enumeration of E. coli O157:H7. Urine was collected at euthanization to determine total ergot alkaloid concentrations. Ewes fed HI-E had lower (P < 0.001) DMI than did ewes fed LO-E (0.8 and 1.6 +/- 0.1 kg/d of DMI for HI-E and LO-E ewes, respectively); consequently, there was a tendency (P = 0.06) for HI-E ewes to lose 0.3 +/- 0.4 kg of BW/d and LO-E ewes to gain 0.2 +/- 0.4 kg of BW/d during the 7 d. Urinary ergot alkaloids were increased (P < 0.001) in ewes fed HI-E (47.8 +/- 9.4 ng/mg of creatinine) compared with those fed LO-E (6.2 +/- 9.4 ng/mg of creatinine). Prolactin tended (P = 0.06) to be decreased in ewes fed HI-E (7.2 +/- 7.0 ng/mL) compared with those fed LO-E (27.7 +/- 7.0 ng/mL). Fecal shedding of E. coli O157:H7 tended (P = 0.06) to be increased in HI-E ewes [5.4 cfu (log10)/g of feces] compared with LO-E ewes [4.5 cfu (log10)/g of feces]. The population of E. coli O157:H7 in luminal contents from the ileum, cecum, and rectum did not differ (P > 0.36) between treatments. Treatment did not influence (P = 0.30) the occurrence of E. coli O157:H7 in cecal or rectal tissues; however, ileal tissues from HI-E ewes tended (P = 0.12) to have an increased incidence of E. coli O157:H7. Concentrations of NEFA tended (P = 0.12) to be greater in HI-E ewes than in LO-E ewes, whereas cortisol was similar (P = 0.49) for HI-E and LO-E ewes. We conclude that short-term feeding of HI-E tall fescue seed may alter the concentrations of prolactin and NEFA, and may increase fecal shedding of E. coli O157:H7 in experimentally inoculated ewes.

Prevalence of Escherichia coli O157:H7 and Salmonella in beef steers consuming different forage diets

AIMS

To compare the prevalence of faecal shedding of Escherichia coli O157:H7 and Salmonella in growing beef cattle consuming various forages.

METHODS AND RESULTS

In Experiment I, faecal samples were collected from steers grazing either endophyte-infected (E+) tall fescue or common bermudagrass (CB). Steers grazing E+ tall fescue were confined to a dry-lot pen and fed CB hay ad libitum for 10 days. In Exp. II, faecal samples were collected from steers grazing either E+ or novel endophyte-infected (NE) tall fescue and treated with one of two anthelmintics: ivermectin (I) or fenbendazole (F). In Exp. I, prevalence of E. coli O157:H7 was less in E+ tall fescue steers fed CB hay than steers grazing CB. More I-treated steers shed Salmonella than F-treated steers at 42-day postanthelmintic treatment but shedding of Salmonella was similar between anthelmintics at day 63 in Exp. II.

CONCLUSIONS

Faecal shedding of pathogenic bacteria was not affected by grazing E+ tall fescue. Alterations of forage diets may influence the prevalence of E. coli O157:H7, and anthelmintic treatment could affect faecal shedding of Salmonella.

SIGNIFICANCE AND IMPACT OF THE STUDY

Knowledge of factors that influence shedding of pathogenic bacteria in cattle is necessary to develop on-farm intervention strategies aimed at reducing pathogen shedding.

Estrous behavior and initiation of estrous cycles in postpartum Brahman-influenced cows after treatment with progesterone and prostaglandin F2α1,2

Spring-calving, crossbred (1/4 to 3/8 Brahman) primiparous (n = 56) and multiparous (n = 102) beef cows were used to evaluate the effects of progesterone, delivered via a controlled internal drug-releasing (CIDR) device, and prostaglandin F(2alpha) (PGF(2alpha)) on estrous behavior, synchronization rate, initiation of estrous cycles, and pregnancy rate during a 2-yr period. To determine luteal activity, weekly blood samples were collected 3 wk before initiation of a 75-d breeding season. Treated cows received a CIDR for 7 d beginning on d -7 of the breeding season. On d 0, CIDR were removed, and cows receiving CIDR were administered PGF(2alpha); control cows received no treatment. Cows were exposed to bulls, and estrous activity was monitored using a radiotelemetry system for the first 30 d of the breeding season. Treatment with CIDR-PGF(2alpha) increased (P < 0.05) the number of mounts received (22.5 +/- 3.0 vs. 13.7 +/- 3.9 for CIDR-PGF(2alpha) vs. untreated control cows, respectively) but did not influence duration of estrus or quiescence between mounts. Number of mounts received and duration of estrus were greater (P < 0.05) in multiparous compared with primiparous cows. Synchronization of estrus was greater (P < 0.05) in cows treated with CIDR-PGF(2alpha) (56%) compared with control cows (13%) during the first 3 d of the breeding season. More (P < 0.05) anestrous cows treated with CIDR-PGF(2alpha) than anestrous control cows were in estrus during the first 3 d (59 vs. 12%) and 30 d (82 vs. 63%) of the breeding season. Treatment with CIDR-PGF(2alpha) decreased (P < 0.05) the interval to first estrus after treatment during the first 30 d of the breeding season compared with control cows (5.5 +/- 1.1 vs. 9.0 +/- 1.4 d). First service conception rate was greater (P < 0.05) in CIDR-PGF(2alpha)-treated cows compared with control cows. Cyclic cows at initiation of the breeding season had an increased (P < 0.05) 75-d pregnancy rate compared with anestrous cows, and the pregnancy rate tended (P = 0.10) to be greater in multiparous compared with primiparous cows. We conclude that treatment of Brahman-influenced cows with progesterone via a CIDR for 7 d, along with administration of PGF(2alpha) at CIDR removal, increases the number of mounts received, improves synchronization and first service conception rates, decreases the interval to first estrus after treatment, and may be effective at inducing estrous cycles in anestrous cows.

Escherichia coliO157:H7 andSalmonellain Water and Soil from Tall Fescue Paddocks

Six 1-ha paddocks of tall fescue (Festuca arundinacea) grazed by Gelbvieh x Angus heifers from 1 March to 21 June 2005 were used to determine the prevalence of Escherichia coli O157:H7 and Salmonella in water tanks, and standing water and surface soil surrounding water tanks in tall fescue paddocks grazed by cattle. Paddocks included two each of Kentucky-31 endophyte-infected tall fescue (E+), Jesup tall fescue with the AR542 endophyte strain (MaxQ), and HiMag tall fescue with strain 4 endophyte (HiMag4). Samples were collected weekly (6 June to 5 July) from water tanks (n = 30), and standing water (n = 18) and surface soil (n = 30) surrounding the water tanks in each paddock commencing 3 weeks prior to termination of grazing until 2 weeks after cattle removal. Prevalence of E. coli O157:H7 tended (p = 0.07) to be increased in standing water and surface soil surrounding water tanks when cattle were present. Presence of cattle resulted in muddy conditions surrounding water tanks. Consumption of E+ tall fescue did not influence (p > 0.10) the prevalence of E. coli O157:H7 or Salmonella in or around water tanks. Neither E. coli O157:H7 or Salmonella were detected in water tanks. Total percentage of standing water samples positive for E. coli O157:H7 was 27.8% and 5.6% for Salmonella. Escherichia coli O157:H7 (6.7%) and Salmonella (10%) also were detected in the surface soil surrounding the water tanks. We conclude that areas surrounding water tanks in tall fescue paddocks can be reservoirs of pathogenic bacteria.

Effect of rotation frequency and weaning date on forage measurements and growth performance by cows and calves grazing endophyte-infected tall fescue pastures overseeded with crabgrass and legumes1

A grazing study was initiated in April 2000 and continued through three calving and weaning cycles (ending July 2003) to investigate the effects of rotational grazing management (twice monthly [2M] vs. twice weekly [2W]) and weaning date (mid-April [EARLY] vs. early June [LATE]) on production of fall-calving cow-calf pairs (495 +/- 9.6 kg initial BW) grazing Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.) overseeded with legumes and crabgrass. Secondary objectives of the experiment were to monitor differences in quantity and quality of available forage and to evaluate changes in forage species composition. Pastures were dominated by tall fescue throughout the study, and the proportion of basal cover was greater (P < 0.05) in 2M than in 2W pastures. The percentage of legumes was very low across all treatment combinations, but the percentage of crabgrass continued to increase (P < 0.05) linearly and quadratically across years for both summer and fall sampling periods, regardless of rotation or weaning program. In vitro DM disappearance and mineral concentrations varied minimally because of rotation frequency or weaning date. Rotation frequency did not substantially affect (P = 0.11 to 0.97) cow BW, hay offered, milk production, calving interval, calf birth weight, or actual or adjusted weaning weights; however, 2M cows had 0.3 units higher (P < 0.05) BCS at the time of breeding than 2W cows. Calves weaned late had greater (P < 0.05) actual weaning weight and weighed more (P < 0.05) on the LATE weaning date than on the EARLY weaning date, but 205-d adjusted weaning weights did not differ (P = 0.74) across weaning dates. Therefore, rotation frequency and/or weaning date had little effect on forage species composition or forage quality. In addition, the rapid rotation program offered little advantage with respect to animal performance, and weaning fall-born calves grazing endophyte-infected tall fescue pastures at approximately 189 d of age seemed to be detrimental to calf performance compared with delaying weaning until 243 d of age.

Aerobic stability of wheat and orchardgrass round-bale silages during winter

Using recently developed technology, balage is often stored in large (1.2 x 1.2 m) round bales that are wrapped in plastic film with an in-line wrapper. The aerobic stability of this fermented forage is important, particularly during winter months when it is fed to livestock or sold as a cash crop. Two types of forage, orchardgrass [Dactylis glomerata L.; 54.4% dry matter (DM)] and wheat (Triticum aestivum L.; 62.4% DM), were packaged in large round bales and wrapped with an in-line wrapper during May 2002. Twenty-one bales of each balage type were unwrapped and exposed to air on Dec. 10, 2002 for 0, 2, 4, 8, 16, 24, or 32 d (ambient temperature range = 0.6 to 19.4 degrees C) to evaluate aerobic stability. For both orchardgrass and wheat balage, final bale weight, concentration of DM, and pH were not affected by exposure time. Across both balage types, DM recoveries were > or = 97% for all bales, indicating that both balage types were very stable when exposed to air. For orchardgrass balage, exposure time had no effect on concentrations of NDF, ADF, hemicellulose, cellulose, or lignin, thereby indicating that little deterioration occurred. Similarly, no contrast relating any fiber component with exposure time was significant for wheat balage. Concentrations of crude protein (CP) were not affected by exposure time for wheat balage, but there was a tendency for exposed orchardgrass bales to have greater concentrations of CP than bales sampled on d 0. Exposure time had no effect on 48-h in situ digestibility of DM for wheat balage, but there was a tendency for a linear increase with exposure time for orchardgrass balage. However, the overall range (78.2 to 80.5%) over the 32-d exposure period was very narrow, and this response is probably of limited biological significance. Generally, concentrations of fermentation acids were low, primarily because of the high concentration of DM within these balages, and only minimal changes in these acids were observed over the exposure interval. These results suggest that the balage evaluated in this trial during winter conditions was very stable after exposure to air for up to 32 d. This should allow for considerable flexibility with respect to feeding, transport, and marketing of balage during winter months without significant aerobic deterioration.

Growth rate and physiology of steers grazing tall fescue inoculated with novel endophytes

Cattle grazing tall fescue (Festuca arundinacea Schreb.) often develop fescue toxicosis. This condition is thought to be caused by ergot alkaloids produced by the endophyte Neotyphodium coenophialum. Endophytes from wild tall fescue plants, which do not produce ergot alkaloids, were transferred into the endophyte-free tall fescue germplasm, HiMag. The novel associations also lacked the ability to produce ergot alkaloids. Our objective was to determine whether cattle grazing these novel endophyte associations showed signs of fescue toxicosis. At the Fayetteville, Arkansas location, tester steers (n = 72) were assigned to one of four pasture treatments: endophyte-free HiMag tall fescue (HiMag-); 'Kentucky-31' tall fescue infected with its native, toxic endophyte (KY+); and two novel endophyte-infected tall fescue associations, HiMag4 and HiMag9. At the Mount Vernon, Missouri location, steers (n = 54) were used to test three of the four cultivars (HiMag9 was not tested). Ergot alkaloid concentrations in the forage of HiMag4 and HiMag9 were low or undetectable. Respiration rate, rectal temperature, ADG, and hair scores were measured during the grazing period. Blood was collected via jugular venipuncture and used for prolactin, aspartate aminotransferase, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cholesterol, triglyceride, and creatinine analysis. Weight gains by steers grazing HiMag4 and HiMag9 did not differ from those of steers grazing HiMag-, but were greater than gains (P < 0.05) by steers on the KY+ treatment. Steers grazing KY+ had higher (P < 0.05) respiration rates, rectal temperatures, and hair scores than did steers grazing novel endophyte and HiMag- pastures. Prolactin, ALP, cholesterol, LDH, and triglycerides all were suppressed (P < 0.05) in steers grazing KY+ compared with steers grazing novel endophyte and HiMag- pastures. Steers grazing the novel endophyte tall fescues did not suffer from the decreased weight gains and toxicities associated with fescue toxicosis, resulting in enhanced animal production.

Evaluation of alternative tactics for management of insecticide-resistant horn flies (Diptera: Muscidae)

A 3-yr study was conducted to determine the efficacy of tactics that could be used to manage populations of insecticide-resistant horn flies, Hematobia irritans irritans (L.). Insecticide spray, spot-on or pour-on formulations and two IGRs in bolus formulation, 1.3- and 3.2-ha pasture rotations on different rotation schedules, 0-50% Brahman breeding, selected fly-resistant cows, and a mechanical trap were evaluated singly and in combination. Concentration-mortality tests indicated that horn flies collected from cows used in the current study were significantly less susceptible to diazinon, coumaphos, and methoxychlor than horn flies from cows at the same locations previously used to determine baseline susceptibility. During the 3-yr study at the Southeast Research and Extension Center (SEREC), the IGR-bolus significantly reduced (P < 0.05) horn fly numbers on both the continuous and rotational graze regimens, resulting in significantly (P < 0.05) greater calf weaning weights (average of 24 kg). Horn fly numbers were significantly greater on untreated cows during the 3-yr study at the Southwest Research and Extension Center (SWREC) compared with the mean fly numbers on cows that received fly-management treatments. All tactics and tactic-combinations used at SWREC on cattle having no Brahman breeding failed to significantly reduce insecticide-resistant horn fly numbers. However, the combination of Brahman breeding with the IGR-Bolus and mechanical trap significantly reduced horn fly numbers and resulted in significant increases in calf weaning weight. In addition, mean horn fly numbers decreased significantly as the percentage Brahman breeding increased with 50% Brahman breeding reducing horn fly numbers by 140 flies per cow. No significant difference was found between the mean fly numbers on the fly-resistant purebred group and the cows that had no Brahman breeding but received the IGR-Bolus or used the mechanical trap. The use of synergized zeta-cypermethrin pour-on treatment successfully complimented the use of IGR-bolus and mechanical traps in reducing insecticide-resistant horn fly numbers. Neither 1.3- nor 3.2-ha size paddocks and stocking rates used in the rotation graze regimens at SEREC and SWREC, respectively, significantly reduced horn fly numbers when compared with continuously grazed paddocks. Data indicated the importance of using tactics that reduce horn fly numbers to approximately 150 horn flies per cow. These data demonstrated the efficacy of using tactic combinations to manage insecticide-resistant horn fly populations.

Modulation of cytochrome P450 metabolism by ergonovine and dihydroergotamine

This study investigated modulation of the cytochrome P450 3A (CYP3A4)-mediated metabolism of ergotamine (ET) by ergonovine and dihydroergotamine. Liver microsomes were prepared from rats treated i.p. for 4 d with: low (10 mM) or high (100 mM) levels of dexamethasone (DM10 and DM100), dihydroergotamine, ergonovine, or control. Cytochrome P450 activity was evaluated using ET and its isomers as substrate. Ergotamine was converted to its metabolites at rates of 0.385 or 0.535 (SE = 0.040) nM/microg protein/min when incubated with liver microsomes from DM10 or DM100 treated rats, respectively. These rates were higher than for rats on other treatments. Induction of CYP34A activity was not greater for ergonovine or dihydroergotamine treatments than for controls. Both ergonovine and dihydroergotamine treatments inhibited in vitro CYP3A4 activity in a dose dependent manner producing quadratic inhibition curves.

ANTAGONISTIC EFFECTS OF SIMULTANEOUS EXPOSURE OF ERGOT ALKALOIDS ON KIDNEY ADENOSINE TRIPHOSPHATASE SYSTEM

Much of the research on fescue toxicosis has concentrated on evaluating animal response to grazing endophyte-infected (E+) versus endophyte-free tall fescue or the effects of single toxins such as ergonovine (EN), ergovaline (EV), or ergotamine (ET) on animal performance. Such approaches have eliminated the opportunity to test the possible additive, synergistic, or antagonistic interactions of one or more ergot alkaloids with the other ergot alkaloids found in E+ tall fescue. This study was conducted to determine the effects of simultaneous exposure of pairs of EN, EV, and ET on the kidney adenosine triphosphatase (ATPase) system in vitro. Tests were performed using three separate rat kidney homogenates and were repeated four times at concentrations of 0, 75, and 200 microM. Individually, EN, EV, and ET induced dose-dependent inhibitions of kidney Na(+)/K(+) ATPase, with EN being most potent, followed by purified EV, and then by ET. The ergot alkaloids inhibited Mg(2+) ATPase to a lesser degree than Na(+)/K(+) ATPase, with EN again being the most potent toxin. Simultaneous exposure to any combination of the ergot alkaloid pairs tested (EV + ET, EV + EN, and ET + EN) resulted in significant interactions (P < 0.05), indicating antagonistic effects on the inhibition of Na(+)/K(+) ATPase and Mg(2+) ATPase for most concentration combinations. These interactions suggest that in studies of the effects of any ergot alkaloid on animal performance, effects of other ergot alkaloids may also be present. Effects may not be additive, as was the case in this study, and the presence of one toxin may enhance or hinder the effectiveness of others.

Growth performance of stocker calves backgrounded on sod-seeded winter annuals or hay and grain

Economically viable options for retaining ownership of spring-born calves through a winter backgrounding program are somewhat limited in the southeastern United States. Although sod-seeded winter annual forages produce less forage than those same forages planted using conventional tillage practices, sod-seeded winter annual forages have the potential to provide a low-cost, rapid-gain, ecologically and economically viable option for retaining ownership of fall-weaned calves. A study was conducted during the winters of 1998, 1999, and 2000 using 180 crossbred calves (261 +/- 2.8 kg initial BW; n = 60 each year) to compare sod-seeded winter annual forages with conventional hay and supplement backgrounding programs in southeast Arkansas. Calves were provided bermudagrass hay (ad libitum) and a grain sorghum-based supplement (2.7 kg/d) on 1-ha dormant bermudagrass pastures or were grazed on 2-ha pastures of bermudagrass/dallisgrass overseeded with 1) annual ryegrass, 2) wheat plus annual ryegrass, or 3) rye plus annual ryegrass at a set stocking rate of 2.5 calves/ha. Calves grazed from mid-December until mid-April but were fed bermudagrass hay during times of low forage mass. Mean CP and IVDMD concentrations were 19.0 and 71.1%, respectively, across sampling dates and winter annual forages, but three-way interactions among forage treatments, year, and sampling date were detected (P < 0.01) for forage mass, concentrations of CP, and IVDMD. The IVDMD of rye plus ryegrass was greater (P < 0.05) than that of ryegrass in yr 2. A forage treatment x sampling date interaction was detected for forage CP in yr 1 (P < 0.05) and 2 (P = 0.05) but not in yr 3 (P = 0.40). Forage mass did not differ (P > or = 0.22) among winter annual treatments on any sampling date. During the first 2 yr, calves fed hay plus supplement gained less (P < 0.05) BW than calves that grazed winter annual forages; gains did not differ (P > or = 0.23) among winter annual treatments. During the 3rd yr, undesirable environmental conditions limited growth of the winter annual forages; total gain did not differ (P = 0.66) among the four treatments. Winter annual forages offer potential to provide high-quality forage for calves retained until spring, but consistent forage production and quality are a concern when sod-seeding techniques are used.

Effects of fescue and clover forage on serum lactate dehydrogenase and glucose 6-phosphate dehydrogenase isoenzymic profiles in steers

We determined the effects of forage type on isoenzymes of lactate dehydrogenase (LDH) and glucose 6-phosphate dehydrogenase (G6PDH). Forty-eight crossbred steers were randomly allotted to replicated pastures consisting of fungus-infected (Neotyphodium coenophialum) fescue or fungus-free fescue each with or without ladino clover overseeding. At the end of the 180-d grazing period, serum was harvested from the steers. Steers were finished in a feedlot and slaughtered after approximately 150 d in the feedlot. Isoenzymes for LDH and G6PDH were separated using PAGE. Five LDH isoenzymes (L1-15) were typically detected. Isoenzyme L1 (most anodic) had the greatest area percent as detected by laser densitometry (72, 12, 10, 5, and 7%, respectively, for L1, L2, L3, L4, and L5). Four proteins had G6PDH activity (G1-G4) with G2 having the greatest area percent (15, 52, 27, and 14, respectively, for G1, G2, G3, and G4). Isoenzymes within a dehydrogenase were correlated (P < .05). In addition, area percentage of L1 was correlated (P < .05; r = .34) with area percentage of G2, and area percentage of L4 was correlated (P < .07; r = .73) with area percentage of G1. Area percentages of L1, L2, and L3 were affected by an interaction (P < .09) of forage types. Body weight gains for steers grazing endophyte-infected fescue were depressed (P < .05); however, steers compensated with increased (P < .05) weight gains during the finishing phase. Fungal toxins produced by Neotyphodium coenophialum may alter an animal's metabolism, growth, and development via shifts in reducing equivalents (NADH).

Effect of maturity on degradation kinetics of sod-seeded cereal grain forage grown in northern Arkansas

Wheat (Triticum aestivum L.), oat (Avena sativa L.), and rye (Secale cereale L.) were overseeded into a dormant bermudagrass (Cynodon dactylon (L.) Pers.) sod and harvested at 3-wk intervals throughout March, April, May, and early June. Plant growth stage was documented for each forage on each harvest date, and harvested forages were evaluated for forage quality characteristics. Degradation kinetics of DM and NDF for these forages were evaluated by the in situ method. Fractional degradation rates for DM and NDF in all three species were relatively rapid for vegetative forage (> or =0.086 h(-1)) but declined rapidly by the heading stage of development and stabilized thereafter. Forage quality declined and forages were more resistant to ruminal degradation as plants entered the reproductive stages of growth. Based on these findings, growth stage is an effective predictor of most characteristics of in situ DM and NDF disappearance. The relationships between these degradation parameters and growth stage were typically explained with quadratic or cubic models. Clearly, forage quality characteristics of overseeded rye deteriorated more rapidly with phenological development and growth stage than quality characteristics of overseeded wheat and oat grown in the same environment. For rye, this problem is further complicated by its accelerated phenological development. These factors combine to permit a very narrow harvest window in early spring, relative to the other cereal grains evaluated. Acceptable forage quality may persist for an extended period in wheat and oat; this suggests that producers wishing to utilize these forages may lengthen the harvest window by planting more than one species, either as a mixture or preferably in independent stands.

Hepatic metabolism of ergot alkaloids in beef cattle by cytochrome P450

This study was conducted to investigate the involvement of cytochrome P450 3A (CYP3A) in the metabolism of ergotamine in beef liver microsomes. When incubated with liver microsomes, ergotamine was hydroxylated to metabolites M1 and M2. Similarly, its isomer was hydroxylated to M1-Iso and M2-Iso (8-hydroxy-derivatives). Further incubation resulted in a second hydroxylation of M1 and M2 to metabolites M3 and M4 (8,9-dihydroxy derivatives). Maximum formation of metabolites was reached after 20 min, and ergotamine and its isomer were almost totally metabolized after 60 min of incubation. The formation of these metabolites was completely dependent on the presence of NADPH or the NADPH generating system and was also dependent on microsome concentration. Ergotamine was converted at a rate of 2 nM/microgram microsome/min when incubated with bovine liver microsomes to produce a metabolite profile (M1, M2, M1-Iso and M2-Iso) similar to the metabolites produced (2.2 nM/microgram/min) when ergotamine was incubated with liver microsomes of dexamethasone treated rats. This work provides information on the modification of ergotamine in bovine liver microsomes by CYP3A, which is of importance in understanding the detoxification and the clearance of ergotamine and other ergot alkaloids by bovine.

Effects of 6-N-propyl-2-thiouracil on growth, hormonal profiles, carcass and reproductive traits of boars

Neonatal 6-N-propyl-2-thiouracil (PTU)-induced hypothyroidism reduces body weight but increases testicular size in adult male rodents. The objective of this study was to determine the effect of prepubertal PTU treatment on boars. For Experiment I, boars (n = 28) were randomly allotted to eight pens. Each pen received one of four PTU doses (0, 0.01, 0.03 and 0.1% in a basal diet) between 28 and 56 days of age (DOA). Due to a lack of difference among three PTU treatments, PTU-treated boars were pooled. Boars treated with PTU had lower (P < 0.05) ADG during treatment, lighter (P < 0.05) BW after 56 DOA and less (P < 0.05) developed epididymides at 154 DOA. For Experiment II, boars (n = 19) were randomly allotted to six pens. Each pen received one of three PTU treatments orally as: control (carrier), PTU-I (0.002% BW of PTU daily between 7 and 70 DOA), or PTU-II (0.002% BW of PTU daily between 28 and 91 DOA). During treatment, PTU-treated boars had lower (P < 0.05) serum T4 levels, rectal temperature, feed intake and ADG. Boars treated with PTU had lower (P < 0.05) BW between 63 and 154 DOA but higher (P < 0.05) gain/feed between 105 and 133 DOA. Boars treated with PTU had less (P < 0.05) developed epididymides and sperm count per gram testis at 238 DOA. These results suggest that prepubertal PTU-induced hypothyroidism had significant effects on growth, hormonal profiles, and reproductive traits of boars; however, it does not appear to be an effective method for increasing testis size and sperm production of commercial boars.

Functional enucleation of bovine oocytes: Effects of centrifugation and ultraviolet light

Functional enucleation is removal or denaturation of an oocytes DNA without piercing the zona pellucida. Two experiments were conducted in this study to determine the effects of centrifugation, and ultraviolet (UV) light on metaphase II bovine oocytes. Experiment 1 evaluated the effects of centrifugation (12,000 x g for 4 min) on the cleavage rate of in vitro matured oocytes. Centrifugation decreased (P < 0.05) the cleavage rate of oocytes (79.5 vs 70.4%). In addition, it was noted that there were two types of ooplasm after centrifugation, stratified and granular. Developmental potential, as represented by cleavage percent, of the two types of ooplasm was not significantly different. Experiment 2 was conducted to determine the interactive effects of centrifugation (as above) and UV light (254 nm) on cleavage rate of oocytes exposed as metaphase II oocytes. The UV light decreased (P < 0.07) oocyte cleavage rates (35.4 vs 25.2%). Centrifuging metaphase II oocytes also decreased (P < 0.07) cleavage rates (34.1 vs 26.5%). In addition, we determined the fate of chromosomes of oocytes centrifuged and(or) exposed to UV light. Both centrifugation and UV light alone affected (P < 0.05) chromosome placement at 42 +/- 3 h after fertilization. Furthermore, centrifugation and UV light interactively increased (P < 0.05) the percentage of non-cleaved oocytes with their DNA located in the perivitelline space (17.4, 15.5, 13.1, and 49.2, respectively, for control, UV exposed, centrifuged, and UV *centrifuged). Collectively, these data indicate that bovine oocytes at the metaphase II stage can be functionally enucleated with centrifugation and exposure to UV light; however, developmental potential may be diminished by those techniques.

Effects of media, serum, oviductal cells, and hormones during maturation on bovine embryo development in vitro

Our objective was to optimize in vitro maturation conditions of bovine oocytes as assessed by embryo development. In Experiment 1, cumulus-oocyte complexes were matured in either M-199 or RPMI-1640. Each medium was supplemented with an antibiotic-antimycotic solution (1%) and estrous cow serum (20%). Cumulus cell expansion after 24 h was greatest for cumulus-oocyte complexes matured in RPMI-1640. Morulae development on d 7 was greater (21.1%) for oocytes matured in M-199 than for oocytes that matured in RPMI-1640 (9.6%). In Experiment 2, cumulus-oocyte complexes were matured in M-199 supplemented with antibiotic-antimycotic solution (1%). Main effects were serum type (20%; estrous cow serum vs. superstimulated estrous cow serum) and coculture (with or without bovine oviductal epithelial cells). The percentage of oocytes developing into blastocysts (d 9) was higher for oocytes matured in estrous cow serum regardless of coculture. In Experiment 3, effects of estradiol-17 beta (0, 1, and 2 micrograms/ml) and equine LH (0, 10, 20, and 30 micrograms/ml) on cumulus cell expansion and development after fertilization were determined. Cumulus cell expansion and blastocyst development decreased with estradiol-17 beta in the maturation medium, but LH in the medium enhanced expansion of cumulus cells and blastocyst development.

Effects of oocyte maturation length, sperm capacitation time, and heparin on bovine embryo development

This study examined the effects of extending oocyte maturation 4 h beyond current methods and capacitating sperm with or without heparin 4 h before oocyte introduction to determine whether embryo development would increase after in vitro fertilization. Oocytes were aspirated from ovaries that were collected at slaughter. Cumulus-enclosed oocytes were matured in M-199 supplemented with serum from cows in standing estrus (20%), antibiotic-antimycotic solution (1%), HEPES (10 mM), and equine LH (30 micrograms/ml) in a humidified 5% CO2 atmosphere. Oocytes were matured for either 24 or 28 h and subsequently fertilized with sperm that had been capacitated 0 or 4 h (before oocyte contact) with or without heparin (0.2 microgram/ml). Data were analyzed as a 2 x 2 x 2 factorial design. Percentages of cleavage and development were transformed by the arcsin square root method before analysis of variance. An interaction of maturation length and sperm capacitation resulted because cleavage rate decreased with precapacitated sperm, but only within the 24-h maturation period. Heparin increased cleavage rate at 48 h after fertilization but did not affect further development. More oocytes developed to morulae when they matured for 24 h than when they matured for 28 h. In conclusion, a 24-h maturation length without precapacitated sperm was optimal for the subsequent development of cumulus-oocyte complexes.

Maintenance of bovine oocytes in prophase of meiosis I by high [cAMP]i

The effects of high intracellular cAMP concentrations ([cAMP]i) on germinal vesicle maintenance of bovine cumulus-oocyte complexes were investigated, using 8-bromo-3',5'-cAMP (8-Br-cAMP) or an invasive adenylate cyclase from Bordetella pertussis to increase the [cAMP]i. The effects of interactions of these agents with macromolecular supplements in culture medium (fetal calf serum, FCS; polyvinylpyrrolidone, PVP; BSA), and different methods of processing complexes before culture, on subsequent germinal vesicle maintenance by invasive adenylate cyclase were studied. While 8-Br-cAMP was unable to maintain germinal vesicle arrest in the majority of oocytes for 20 h (36% with FCS, 24% with BSA, 18% with PVP), it maintained germinal vesicle arrest in a high proportion of cumulus-enclosed oocytes when BSA or PVP was used (37% with FCS, 52% with BSA, 53% with PVP). The difference in frequency of germinal vesicle maintenance between macromolecular supplements was not related to [cAMP]i when assayed after culture for 2 h with invasive adenylate cyclase. Complexes processed in whole follicular fluid were not maintained in meiotic arrest (26%) when cultured with invasive adenylate cyclase and PVP. Complexes processed in follicular fluid with 3-isobutyl 1-methylxanthine (IBMX) plus invasive adenylate cyclase were arrested at the germinal vesicle stage at high frequencies (65%), while those processed in IBMX or IBMX plus 8-Br-cAMP-supplemented follicular fluid had intermediate (43% and 49%, respectively) frequencies of intact germinal vesicles. Oocyte complexes processed in follicular fluid supplemented with IBMX and invasive adenylate cyclase formed morulae and blastocysts (27.2%), as did oocytes processed in follicular fluid alone (26%). Phosphoprotein profiles showed that control oocytes and 8-Br-cAMP-treated oocytes share a profile that is different from that of oocytes treated with invasive adenylate cyclase. These results show that increased [cAMP]i reversibly maintains bovine oocytes in meiotic arrest for an extended period without the occurrence of the post-translational protein modifications observed during meiotic resumption or transient arrest.

Relationship of horn fly to face fly infestation in beef cattle

Horn fly and face fly counts (n = 394) taken on 194 beef cows representing seven breed groups were used to determine the effects of horn fly and face fly counts. Breed groups included were Angus (ANI and ANII), Chianina (CA), Charolais (CH), Hereford (HH), Polled Hereford (PH), and Red Poll (RP). The breed group designated ANI consisted of small-framed cows. Total horn fly and total face fly counts were determined weekly on each cow beginning in May and ending in late October or early November in a 3-yr (1988-90) study. Face flies were not counted on the ANI and ANII breed groups in 1988. All fly counts were taken when cows were grazing Ozark upland native grass pastures with only containment fences separating breeding groups. No insecticides were used in the study. Data for analysis were the mean annual horn fly and face fly counts (averaged across weeks), spring weight and fall weights, gain/day between spring and fall weights, and skin surface area in the spring (SSAS) and fall (SSAF) for each cow. Relationships among measurements were examined by correlation and regression procedures. Horn fly count was correlated (P < .05) with face fly count, spring weight, gain/day, and SSAS (.23, .11, -.25, and .12, respectively). Correlations of horn fly count with fall weight and SSAF were non-significant. Horn fly count, breed, and the breed x horn fly count interaction were significant (P < .05) for the face fly regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma characteristics of beef cattle classified as resistant or susceptible to horn flies

Horn flies inflict economic losses on cattle producers. Therefore, the objective of this study was to identify a serological marker for cows that are innately resistant to horn flies. Plasma characteristics (optical density, cortisol, and protein pattern) were studied in beef cattle classified (cow-type) as horn fly resistant or susceptible. Cows (n = 30) of five breed groups were used in this study. Cows were bled via jugular venipuncture in May (the beginning of the horn fly season). Plasma optical density at wavelengths 200 and 464 nm was different (P < .05) between resistant and susceptible cattle. Cow-type also affected (P < .05) area percentage for proteins with running molecular weights (M(r)) of 74,000 and 54,000 daltons. Breed group affected (P < .05) optical density at wavelengths 200, 280, 320, and 464 nm and concentration of cortisol in plasma. When the ratio of area percentage for protein bands 7 and 9 (M(r) 74,000 and 54,000, respectively) was determined, cows could be categorized as horn fly resistant or susceptible. These data suggest that a serological marker for horn fly resistant cattle has been identified; however, the marker will need to be tested on a larger population of cattle.

Effect of free amino acids and vitamins on cleavage and developmental rate of bovine zygotes in vitro

Due to the complicated media used for culturing bovine embryos, most of the nutrient requirements are unknown. Recently, we developed a simple, serum-free medium (CR1) that allows bovine embryos to develop in vitro. Therefore, our objective was to determine whether development of bovine embryos would be improved by the addition of free amino acids and vitamins to CR1. Oocytes were recovered from slaughterhouse ovaries and matured 22 +/- 2 h, following which the oocytes were randomly allotted to treatment. The experiment was a randomized block design with a 2 x 5 factorial treatment structure. The oocytes were fertilized with or without cumulus cells intact. The five fertilization media were 1) Control (CR1 +/- 10 micrograms/mL of phenol red); 2) control + basal medium Eagle (BME) essential amino acids (EAA) + minimum essential medium (MEM) nonessential amino acids (NEA) + MEM vitamins (VIT); 3) control + EAA + NEA; 4) control + EAA + VIT; and 5) control + NEA + VIT. Cleavage rate was greater (P < .001) when cumulus cells remained on the oocytes during fertilization (51.7 vs 73.2% without and with cumulus cells, respectively). The frequency of blastocysts was increased (P < .001) when EAA or NEA were added to CR1; however, adding VIT had no effect or tended (P = .12) to decrease the frequency of embryos attaining the blastocyst stage. This experiment demonstrates that development of bovine embryos in vitro can be improved by the addition of free amino acids to a simple medium. Contrary to work in rodents, the mixture of vitamins in MEM was not beneficial for bovine embryos.

Development of bovine embryos in vitro as affected by energy substrates

Simple media were developed to study the metabolic requirements of bovine embryos up to Day 7 (Day 0 = day of oocyte aspiration) in vitro. Embryos were derived from oocytes matured and fertilized in vitro. At 45 +/- 2 h post insemination, embryos (> or = 2 cells) were randomly allotted to treatments. Examined in experiments 1 and 3 was the effect of pyruvate concentration in the presence of lactate. In the presence of lactate, pyruvate (0.2-5.0 mM) had no effect (p > 0.05) on the percentage of morulae or blastocysts. However, increasing the concentration of hemicalcium L-lactate from 5 mM to 10 mM decreased (p < 0.001) the percentage of embryos reaching the morula or blastocyst stage (experiment 3). Neither magnesium sulfate (0.5 mM) nor EDTA (10 mM) improved embryo development when added to the medium CR1 (experiment 2). Increasing the calcium level to 5 mM or the lactate level to 10 mM had no effect (p > 0.05) on embryo development (experiment 4). However, the interaction of adding calcium and lactate resulted in a decreased (p < 0.05) percentage of morulae. Determined in experiment 6 were the independent effects of pyruvate, lactate, and glucose on embryo development in vitro. As pyruvate or lactate level was increased from 1 to 10 mM, the percentage of blastocysts was decreased (p < 0.05). These experiments indicate that adding pyruvate to a medium containing lactate is not necessary for development of bovine embryos in vitro.

Estimates of repeatability and heritability of horn fly resistance in beef cattle

Horn fly population density on 215 beef cows representing seven breed groups and 51 sires was used to obtain estimates of repeatability (rXX) and heritability (h2) for resistance to the horn fly (Haematobia irritans [L.] Diptera: Muscidae). Total horn fly densities were determined weekly on each cow beginning in May and ending in late October or early November of 1988, 1989, and 1990. No insecticides were used on cattle in this study. Estimates of h2 for horn fly resistance (low horn fly number per cow) were obtained by the paternal half-sib method (4 sigma 2S) and as twice the intrasire regression of offspring on dam (2bDD/S). Variance component estimates were obtained using a completely nested ANOVA that included overall mean, breed, sire/breed, cow/sire, and residual error. One hundred twenty-six daughter-dam pairs were available for regression analysis. In a preliminary analysis, the within-breed regression was nonsignificant (P greater than .05), implying that the regression was the same for all breeds; therefore, breed was deleted from the model. The regression model included an overall mean, year, and the intrasire regression of daughter on dam (bDD/S). The estimate of rXX was .47 +/- .02. Estimates of h2 were .78 +/- .16 and .59 +/- .10 from the 4 sigma 2S and 2bDD/S methods, respectively. Similar estimates of rXX and h2 were obtained when each observation of horn fly number per cow (x) was transformed to both log10 (x) and square root of x. These estimates suggest the possibility of selection procedures as an environmentally safe alternative to the use of chemical control.

Synthesis of prostaglandins by pig blastocysts cultured in medium containing estradiol or catechol estrogen

Two experiments were conducted to determine the effects of 2-hydroxy-estradiol-17 beta (2-OH-E2; 0, 50 and 100 microM) and estradiol-17 beta (E2; 0, 25 and 50 microM) on prostaglandin (PG) E and PGF2 alpha synthesis by day-10 pig blastocysts (day 0 is first day of estrus). Blastocysts were incubated in a modified Krebs-Ringer bicarbonate medium, supplemented with bovine serum albumin (4 mg/ml) and the vitamins and amino acids (essential and nonessential) in Minimum Essential Medium (without phenol red or antibiotics). The incubations were conducted at 39 degrees C for three 2-h periods; the second and third periods included an E2 or catechol estrogen treatment. Release of PGF2 alpha into the culture medium decreased (p less than 0.001) linearly with increasing concentrations of 2-OH-E2 in both periods. Release of PGE was not affected by 2-OH-E2, therefore 2-OH-E2 increased (p less than 0.06) the PGE:PGF2 alpha. When E2 was added to the medium, release of PGE was decreased (p less than 0.01) during the second and third periods. Release of PGF2 alpha also was decreased (p less than 0.05) by E2 during period 2, but E2 did not alter the PGE:PGF2 alpha. Content of PGs in blastocysts at recovery was less than 10% of the PGs released in vitro. Therefore, these studies demonstrate effects of both the primary and catechol forms of E2 on the synthesis of PGE and PGF2 alpha. Catechol estrogens and E2 may inhibit PG synthesis and modify the PGE:PGF2 alpha during the establishment of pregnancy in pigs.

Macrophage binding of cells resistant and sensitive to contact-dependent cytotoxicity

We compared macrophage binding and killing of F5b cells to the binding and killing of P815 mastocytoma cells and to several other nontransformed and transformed cell lines. Formalin fixation of elicited or activated macrophages did not affect binding of F5b or 3T3 cells but did abrogate binding of P815 cells. However, formalin fixation abrogated resident macrophage binding of F5b and 3T3 cells. Therefore, depending on the type of macrophage or target cell, formalin fixation may affect binding. Only the binding of P815 cells was dependent upon activation; macrophage binding of target cells F5b and 3T3 was not. Even though macrophages bound F5b and 3T3 cells, macrophages only mediated contact-dependent cytotoxicity against F5b cells. Macrophages did not kill 3T3 cells. Experiments also compared macrophage binding and killing of the uv-light-induced tumor cell lines 1422, 2237, and 2237a46. Only the cell line 2237a46 was susceptible to contact-dependent killing. Both 1422 and 2237 cells were resistant. In contrast, cell lines 2237a46 and 1422 were bound by activated macrophages while 2237 cells were bound poorly.

Test of the antiorthostatic suspension model on mice: effects on the inflammatory cell response

We tested the antiorthostatic suspension model for use as a 1G model to study the effects of factors that will be encountered during space travel on inflammation. We found no differences in inflammatory cells induced in antiorthostatically suspended mice. However, the superoxide response (used for oxidative killing of bacteria such as S. aureus) was impaired in antiorthostatically oriented mice compared to control mice. Elevated corticosterone levels were found in antiorthostatically suspended mice and indicate that stress may be a factor in the model. If the stress factor of the model correlates with the physiological stress of space flight, antiorthostatic suspension may be an acceptable model for studying inflammatory responses in mice.

In vitro synthesis of prostaglandin E and F2 alpha by pig endometrium in the presence of estradiol, catechol estrogen and ascorbic acid

These experiments were undertaken to determine the potential for estradiol-17 beta (E2), 2-hydroxyestradiol-17 beta (2-OH-E2) and 4-hydroxyestradiol-17 beta (4-OH-E2) to regulate prostaglandin (PG) E and F2 alpha synthesis by pig endometrium. Endometrium was collected from pigs on d 10 of pregnancy and incubated (15 to 20 mg/well) for three 2-h periods in 2 ml of medium in 24-well culture plates. At the end of each period, the medium was removed and frozen. Later media were thawed and assayed for PGE and PGF2 alpha. During Periods 2 and 3, the medium contained 0, 25, 50, 100 or 150 microM 2-OH-E2 (Exp. 1); 0, 25 or 50 microM 4-OH-E2 (Exp. 2); or 0, 25 or 50 microM E2 (Exp. 3). Each experiment was a factorial with 2-OH-E2, 4-OH-E2 or E2 as one main effect and 0 or 1 mM ascorbate as a second main effect. Ascorbate decreased (P less than .01) PGE and PGF2 alpha release in all experiments. Two-hydroxyestradiol-17 beta decreased (P less than .01) PGE and PGF2 alpha release into the medium during Periods 2 and 3 in a dose-dependent manner (Exp. 1). In Exp. 2, 4-OH-E2 decreased (P less than .07) endometrial release of PGE and PGF2 alpha in Periods 2 and 3 and increased (P less than .01) the PGE:PGF2 alpha in Period 3. In Exp. 3, E2 decreased release of PGE during Period 3 and PGF2 alpha release during Period 2. The PGE:PGF2 alpha was not altered by E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Pig blastocyst development in vitro is affected by amino acids

Pig embryos were removed 5 d after onset of estrus and cultured in modified Krebs-Ringer bicarbonate (mKRB) medium containing bovine serum albumin (BSA; 1 mg/ml). Media in Exp. 1 and 2, but not in Exp. 3, contained 10% heat-inactivated lamb serum (LS). In Exp. 1, embryos were cultured in 1) mKRB + LS or mKRB + LS supplemented with 2) glutamine (2 mM); 3) phenylalanine (.1 mM), methionine (.05 mM) and isoleucine (.2 mM); or 4) phenylalanine, methionine, isoleucine and glutamine. Embryos cultured in media with supplemental phenylalanine, methionine and isoleucine attained larger (P less than .05) volumes during culture and initiated hatching at an increased (P less than .05) frequency compared with embryos cultured without additional amino acids. In contrast, adding glutamine depressed (P less than .05) the maximum volumes observed during culture. In Exp. 2 mKRB + LS was compared with mKRB + LS plus phenylalanine (.1 mM), methionine (.05 mM) and isoleucine (.2 mM); methionine and isoleucine; phenylalanine and isoleucine, or phenylalanine and methionine. Embryos cultured in media supplemented with phenylalanine and methionine attained larger (P less than .05) volumes than embryos cultured in either media without added methionine. Fewer (P less than .05) embryos cultured without methionine initiated hatching (56%) compared with embryos provided methionine (89%). In Exp. 3, we evaluated the addition of glutamine (1 mM) with or without phenylalanine (.1 mM), methionine (.05 mM) and isoleucine (.2 mM) to serum-free mKRB. Adding glutamine alone, but not in combination, increased (P less than .05) blastocyst volumes on d 3 and maximum volume attained during culture compared with embryos cultured in mKRB alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of pig blastocysts in vitro is altered by serum, bovine serum albumin and amino acids and vitamins

We tested the effects of the amino acids and vitamins in minimum essential medium (MEM) and Eagle's medium (BME) on pig blastocyst development and nuclei number. Embryos were recovered either 5 or 6 d after first detected estrus and were cultured for 96 h in U-bottomed wells (0.2 ml). In Experiment 1, addition of MEM amino acids and vitamins to modified Krebs-Ringer bicarbonate (MKRB) medium containing either bovine serum albumin (BSA, 4 mg/ml) or lamb serum (10%, v/v) resulted in fewer (P<0.001) nuclei and smaller (P<0.05) embryo volumes at the end of culture as compared to embryos cultured in MKRB without MEM-supplements. Addition of MEM-amino acids without glutamine (Experiment II) depressed blastocyst volume and rate of hatching, but glutamine (2 mM) had no effect on embryo development. Dialysis (molecular weight > 12,000 retained) of fetal bovine serum (Experiment III) did not affect blastocyst expansion but reduced (P<0.05) the number of nuclei/blastocyst at the end of the culture. Embryos cultured in MKRB with dialyzed serum and the amino acids and vitamins in BME were smaller (P<0.05) and had fewer (P<0.05) nuclei than embryos cultured in MKRB with dialyzed serum but without the BME-supplements. We conclude that, under our culture conditions, MEM and BME amino acids and vitamins are detrimental to the development of early pig blastocysts and that this effect is not due to glutamine. Also, dialysis of fetal bovine serum removes some component(s) that are important for cell division by pig embryos, but it does not affect blastocyst expansion.