Evaluation of the effects of sire and dam calving group on age at first calving in Brahman heifers

This study evaluated the possible effects of sire and dam calving groups on age at first calving in Brahman heifers. A total of 570 heifers born between the years 2004 and 2017 were exposed as yearlings to fertile bulls through time of pregnancy determination. A calving group was determined by calculating the mean (993 d) and standard deviation (187 d) of heifer age at first calving. Heifers considered to calve early (≤899 d; calving group = 1) or late (≥1087 d; calving group = 3) were at least half a standard deviation (94 d) away from the mean. All other heifers were considered to have an intermediate age at first calving (900-1086 d; calving group = 2). Of the 570 heifers, only heifers from a dam (n = 182) with a known age at first calving and from a sire (n = 35) with 5 or more daughters were kept to determine the effect of dam calving group and the effect of sire calving group on age at first calving and calving group in daughters, resulting in a total of 284 heifers available for analysis. Variables included were dam and sire calving groups of the heifer, heifer age at first calving, heifer calving group, heifer season of birth, and heifer year of birth. Data were analyzed using the GLM procedures of SAS and proportions were tested using Chi-square. Sire calving group did affect (P < 0.01) age at first calving and calving group in heifers, but dam calving group did not affect (P > 0.10) daughter age at first calving or calving group. Analysis of dam calving group and sire calving group effects identified a year of birth effect (P < 0.01) on daughter age at first calving and calving group, whereas there was no significant season of birth effect. The proportion of daughters calving early for sire calving groups differed significantly from the expected proportion (P < 0.01), whereas the proportion of daughters calving early for dam calving groups did not differ. An effort to produce a greater proportion of Brahman heifers capable of calving early will not be effective from the dam side but may be effective from the sire side.

Relationships between numbers of antral follicles and postpartum interval in Brahman females

To determine relationships of ovarian antral follicle count (AFC) on d 28 postpartum with postpartum interval (PPI) and AFC on d 8 post-estrus, three-dimensional ultrasonography was performed on multiparous (n = 47) and primiparous (n = 20) Brahman cows on d 28 postpartum and on d 8 post-estrus. Follicles were evaluated to determine numbers of total, small (≤17 mm³), medium (17 mm³-67 mm³), and large follicles (≥67 mm³) on each ovary. Estrus was detected using vasectomized, penile-deviated bulls fitted with chin-ball markers during the AI period and with tail paint during the natural service period. Cows with AFC ≥ ½ SD above the mean were classified as high, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as low. Classes of AFC for total follicles included low (L ≤ 73), intermediate (74 ≤ I ≤ 112), and high (H ≥ 113). Classes of AFC for small follicles included low (L ≤ 55), intermediate (56 ≤ I ≤ 87), and high (H ≥ 88). Classes of AFC for medium follicles included low (L ≤ 13), intermediate (14 ≤ I ≤ 23), and high (H ≥ 24). Classes of AFC for large follicles included low (L ≤ 2), intermediate (3 ≤ I ≤ 4), and high (H ≥ 5). Cows with PPI ≥ ½ SD above the mean were classified as long, those within ½ SD of the mean were classified as intermediate, and those ≥ ½ SD below the mean were classified as short. Classes of PPI included short (S ≤ 47 d), intermediate (48 d ≤ I ≤ 75 d), and long (L ≥ 76 d). The PROC MIXED procedure of SAS was used to analyze potential differences among classes of AFC and PPI. The PROC REG procedure of SAS was used to analyze relationships between AFC and PPI and between AFC on d 28 postpartum and on d 8 post-estrus. The PPI differed among classes of total (P < 0.01; L = 76.2 ± 6.0, I = 61.7 ± 4.5, H = 43.8 ± 6.5), small (P < 0.01; L = 74.3 ± 5.6, I = 64.6 ± 4.8, H = 42.9 ± 5.9), and medium AFC (P = 0.04; L = 72.3 ± 5.9, I = 59.3 ± 5.8, H = 52.1 ± 5.8). The PPI did not differ among classes of large AFC (P = 0.81). As total AFC on d 28 postpartum increased, PPI decreased (P < 0.01, Adj.R² = 0.13). Total AFC on d 8 post-estrus was positively associated with total AFC on d 28 postpartum (P < 0.01, Adj.R² = 0.66). These results suggest that: a) populations of total, small, and medium follicles in the postpartum period predict PPI in Brahman females and b) total AFC in Brahman females are consistent.

Evaluation of the influence of prenatal transportation stress on GnRH-stimulated luteinizing hormone and testosterone secretion in sexually mature Brahman bulls

This study examined the relationship of prenatal transportation stress (PNS) with exogenous GnRH-induced LH and testosterone secretion in sexually mature Brahman bulls. Brahman cows (n = 96; 48 were stressed by transportation at 5 stages of gestation and 48 were controls) produced a calf crop of 85 calves. All bulls (n = 46) from this calf crop were electroejaculated every 2 wk beginning at a scrotal circumference of 24 cm until sexual maturity (SM; i.e., 500 million sperm/ejaculate). The initial 11 control and 12 PNS bulls to reach SM were selected for the experiment. Within 7-21 d after reaching SM, bulls were fitted with jugular cannulas, from which blood samples were collected at 15-min intervals for 6 h prior to exogenous GnRH administration (10 ng/kg BW; i.v.) and for 6 h after GnRH. Serum concentrations of LH, testosterone, and cortisol were determined by RIA. Age and body weight did not differ ( > 0.1) between PNS and control bulls at the time of the experiment. All bulls responded similarly to exogenous GnRH, indicating no influence of PNS on LH or testosterone response to GnRH. More ( < 0.01) PNS (9 of 11) than control (3 of 12) bulls exhibited an endogenous pre-GnRH LH pulse, and more ( = 0.02) PNS (9 of 11) than control bulls (4 of 12) exhibited a pre-GnRH testosterone response to LH. The average concentration of testosterone during the 60 min (time -60, -45, -30, -15, and 0 min relative to GnRH) immediately preceding GnRH, tended to be greater ( = 0.07) in PNS (1.46 ± 0.30 ng/mL) than control (0.68 ± 0.28 ng/mL) bulls. During that time span serum cortisol was lower ( < 0.01) in PNS (4.00 ± 0.91 ng/mL) than control (7.8 ± 0.87 ng/mL) bulls. A treatment by time interaction ( = 0.03) affected testosterone concentrations from time -240 to 360 min relative to GnRH. Results from this study indicate that PNS did not affect pituitary responsiveness to GnRH or testicular responsiveness to GnRH-induced LH secretion.

Prenatal transportation stress alters temperament and serum cortisol concentrations in suckling Brahman calves

This experiment examined the relationship between prenatal stress and subsequent calf temperament through weaning. The prenatal stressor used was repeated transportation of pregnant Brahman cows for 2 h at 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 d of gestation. Prenatally stressed calves ( = 41) were compared with controls ( = 44; dams did not undergo transportation during pregnancy) from 2 wk of age until weaning (average age at weaning = 174.8 ± 1.3 d). Temperament was defined by pen score (PS; 1 = calm and 5 = excitable), exit velocity (EV; m/sec), and temperament score (TS; (PS + EV)/2) and was recorded for each calf on d -168, -140, -112, -84, -56, -28, and 0 relative to weaning (d 0 = weaning). Cortisol concentrations were determined in serum samples obtained on d -168, -140, -28, and 0 relative to weaning. Birth weight and weaning weight were not different between treatment groups ( > 0.1). Pen score was greater ( = 0.03) in prenatally stressed calves (2.84 ± 0.21) relative to controls (2.31 ± 0.21). Exit velocity was greater ( < 0.01) in prenatally stressed calves (2.1 ± 0.14 m/sec) than in controls (1.61 ± 0.14 m/sec). Exit velocity was affected by a treatment × calf sex interaction ( = 0.04) and was greater in prenatally stressed females. Exit velocity was also affected by day ( < 0.0001). Temperament score was greater ( = 0.01) in prenatally stressed calves (2.45 ± 0.16) than in controls (1.95 ± 0.16). Temperament score was affected by day ( < 0.01). Basal cortisol concentrations were greater ( = 0.04) in prenatally stressed calves (15.87 ± 1.04 ng/mL) than in controls (13.42 ± 1.03 ng/mL). Basal cortisol concentrations were greater ( < 0.01) in females (16.61 ± 1.06 ng/mL) than in males (12.68 ± 1.02 ng/mL). Cortisol concentrations were positively correlated ( < 0.01) with PS ( = 0.55, < 0.01), EV ( = 0.4, < 0.01), and TS ( = 0.55, < 0.01). Overall, suckling Brahman calves that were prenatally stressed were more temperamental and had greater circulating serum concentrations of cortisol than control calves.

Physiological and metabolic responses of gestating Brahman cows to repeated transportation

This study characterized physiological responses to repeated transportation (TRANS) of gestating cows of differing temperaments. Cows were classified as Calm (C; = 10), Intermediate (I; = 28), or Temperamental (T; = 10). Based on artificial insemination date and pregnancy confirmation, cows were TRANS for 2 h on d 60 (TRANS1), 80 (TRANS2), 100 (TRANS3), 120 (TRANS4), and 140 (TRANS5) ± 5 d of gestation. Indwelling vaginal temperature (VT) monitoring devices were inserted 24 h before each TRANS with VT recorded from 2 h before TRANS and averaged into 5-min intervals through 30 min after TRANS. Serum samples were collected before loading and on unloading from the trailer to determine concentrations of cortisol, glucose, and nonesterified fatty acids (NEFA). Data were analyzed by repeated measures analysis in SAS. Serum cortisol concentrations were affected by temperament ( < 0.001), with T cows having the greater concentrations of cortisol before each TRANS event. All cows (100%) regardless of temperament exhibited elevations in cortisol following each TRANS event. Peak VT was greater ( < 0.001) at TRANS1 relative to all other TRANS events regardless of cow temperament. During TRANS, the T cows tended ( < 0.09) to have greater peak VT (39.86 ± 0.15°C) compared to C (39.41 ± 0.16°C) and I cows (39.55 ± 0.08°C). Area under the VT curve decreased ( = 0.002) from TRANS1 through TRANS5. Pre-TRANS serum glucose concentration at TRANS1 was greater ( < 0.03) for T (68.13 ± 4.31mg/dL) compared to I (53.42 ± 2.78 mg/dL) and C cows (52.76 ± 4.60 mg/dL). The C and I cows had greater changes in NEFA concentration between pre- and post-transport, and T cows showed the least change ( < 0.001). Cow VT and serum glucose concentration decreased in all temperaments ( < 0.01) with repeated TRANS; however, serum NEFA concentration post-TRANS did not vary ( > 0.10) with repeated TRANS events. Serum glucose concentrations were affected ( < 0.02) by a TRANS event by temperament interaction with T cows taking more TRANS events to decrease their change in glucose concentration compared to C and I cows. These results demonstrate that temperament influences physiological responses to stress in gestating Brahman cows. Although repeated transport in our study is confounded with day of gestation, seasonal changes, and learning from repeated handling and transport, repeated transport is a useful model of repeated stress in studying the effects of temperament.

Interrelationships among growth, endocrine, immune, and temperament variables in neonatal Brahman calves

Interrelationships among growth, endocrine, immune, and temperament variables were assessed in neonatal Brahman calves. The velocity upon exiting a working chute (exit velocity) of an animal was measured and used as an objective indicator of temperament to classify calves as calm, intermediate, or temperamental. Calves (n = 116) were weighed weekly between d 0 and 21 to 24, and blood samples were collected for plasma and serum on d 0, 1, 2, 7, 14, and 21 to 24 after birth to measure concentrations of immunoglobulins, cortisol, and epinephrine (EPI). Body weight increased from d 0 through d 21 to 24 (P < 0.001) with bulls (n = 60) having greater BW than heifers (n = 56; P = 0.02). Serum concentrations of cortisol were greatest on d 0 before declining (P < 0.001) over the ensuing 21 to 24 d and were not related to temperament (P = 0.89) or sex (P = 0.97). Concentrations of EPI were affected by time, with an increase in EPI concentrations in temperamental bulls between 2 and 14 d of age (P < 0.008). Concentrations of EPI were not affected by temperament (P = 0.44) or sex (P = 0.68). Serum immunoglobulin concentrations peaked on d 1 before declining (P < 0.01) but were not related to temperament (P = 0.40 to 0.68). Of the stress hormones measured (cortisol and EPI), only cortisol was associated with the early performance of the calf. Calf BW at d 21 to 24 and BW gain were positively associated with serum immunoglobulin concentrations, yet negatively associated with concentrations of cortisol. Serum immunoglobulin concentrations were negatively correlated with cortisol concentrations (r = -0.28; P = 0.003), yet positively associated with EPI concentrations (r = 0.51; P = 0.003). During the neonatal period in this study, there was no relationship of temperament with passive immunity or stress hormone concentrations; however, growth was positively associated with passive immunity and negatively associated with stress hormones. Measuring exit velocity as early in life as d 21 to 24 fails to accurately predict temperament at weaning in over 40% of Brahman calves. Our conclusion is that measurement of exit velocity should be done nearer to the time of weaning than to birth. These data can be beneficial in developing best management practices for young calves.

Plasma progesterone response following ACTH administration during mid-gestation in the pregnant Brahman heifer

Previous reports of adrenal progesterone (P4) contributions during late gestation in cattle, and ACTH-induced P4 responses in the non-pregnant heifer, prompted a retrospective investigation to evaluate the plasma P4 response and the relative ratio of plasma cortisol (CT) to P4 following ACTH administration during mid-gestation in pregnant Brahman heifers. Twenty-three pregnant (139.0 +/- 5.0 days of gestation) Brahman heifers received one of the following treatments: 0 (saline; n = 5), 0.125 (n = 4), 0.25 (n = 5), 0.5 (n = 4), or 1.0 (n = 5)IU of ACTH per kg BW. Blood samples were collected at -15 and -0.5 (time 0), 15, 30, 45, 60, 75, 105, 135, 165, 195, and 255-min post-ACTH challenge. Plasma P4 and CT were quantified by RIA. Pre-ACTH P4 did not differ (P > 0.10) among ACTH treatment groups (pooled, 12.1 +/- 0.6 ng/mL). Among peak P4 values at 15-min post-ACTH infusion, control P4 (9.6 +/- 1.2 ng/mL) tended to be lower (P < 0.07) than 0.5 IU ACTH-treated heifers (13.3 +/- 1.1 ng/mL); and were lower (P < 0.02) than 0.25 and 1.0 IU ACTH-treated heifers (14.7 +/- 1.1 and 22.2 +/- 3.7 ng/mL, respectively). During the primary P4 response period (0 to 75-min post-ACTH), the area under the curve (AUC) was greater (P < 0.05) for 1.0 IU ACTH-treated heifers than all other groups. The CT:P4 ratios were lower (time x treatment, P < 0.01) for control heifers than all ACTH-treated heifers. Among ACTH-treated heifers, CT:P4 ratio response and CT:P4 ratio AUC were similar (P > 0.10) following ACTH challenge. In conclusion, acute increases in ACTH elevated plasma P4, likely of adrenal origin, in mid-gestation pregnant heifers, while the CT:P4 ratio (relative output) remained constant irrespective of ACTH dose (0.125-1.0 IU). Whether ACTH-induced increases in P4 in pregnant animals are of physiological significance (e.g., an accessory role in the maintenance of pregnancy during periods of acute stress) remains to be determined.

Effects of estrous synchronization on response to nitric oxide donors, nitric oxide synthase inhibitors, and endothelin-1 in vitro

Two experiments were conducted to determine the effects of nitric oxide (NO) donors, endothelin-(ET-1), and NO synthase (NOS) inhibitors on bovine luteal function in vitro. In experiment 1, estrus in Brahman cows was synchronized with Synchro-Mate-B (SMB) and day-13-14 corpora luteal slices were weighed, diced and incubated in vitro. Treatments (100 ng/ml) were: vehicle, N[see symbol in text]-nitro-L-arginine-L-methyl ester (L-NAME), N(G)-monomethyl-L-arginine acetate (L-NMMA), diethylenetriamine (DETA), DETA-NONOate, sodium nitroprusside (SNP), or ET-1. In experiment 2, estrus was synchronized with Lutalyse, a Controlled Intravaginal Progesterone Releasing Device (CIDR), or cows were not synchronized. Corpora lutea were collected, weighed, and luteal slices were weighed, diced and incubated in vitro with treatments. Treatments (100ng/ml) were: vehicle, L- NAME, L-NMMA, DETA, DETA-NONOate, sodium nitroprusside, S-nitroso-N-acetylpenicillamine (SNAP) or endothelin-1. Tissues were incubated in M- 199 for 1 h without treatments and for 4 and 8 h in both experiments with treatments in both experiments. Media were analyzed for progesterone, prostaglandins E2 and F2alpha (PGE2, PGF2alpha) by radioimmunoassay (RIA). Hormone data in experiments 1 and 2 were analyzed by 2 x 7 and 3 x 2 x 8 factorial design for analysis of variance (ANOVA), respectively. Luteal weights in experiment 2 were analyzed by a one-way ANOVA. Concentrations of progesterone in media were similar (P > or = 0.05) among treatments within experiments. Concentrations of PGE2 in media in experiment 1 were undetectable in 90 and 57% of the samples at 4 and 8 h, respectively. PGF2alpha increased (P < or = 0.05) with time, but did not differ (P > or = 0.05) among treatments. Secretion of PGF2alpha was not affected by treatments (P > or = 0.05). In experiment 2, luteal weights of the induced estrous cycle were decreased (P < or = 0.05) by Lutalyse. Concentrations of PGE2 and PGF2alpha increased (P < or = 0.05) with time in control of all three synchronization regimens. DETA-NONOate, SNAP, sodium nitroprusside (NO donors) and ET-1 increased (P < or = 0.05) PGE2 except in the CIDR synchronized group (P > or = 0.05). No treatment increased (P > or = 0.05) PGF2alpha in any synchronization regimen. It is concluded that either SMB containing norgestomet or a CIDR containing progesterone alters luteal secretion of PGE2, Lutalyse lowers luteal weights in the induced estrous cycle, and NO or ET-1 given alone are not luteolytic agents. It is suggested that NO and ET-1 could have indirect antiluteolytic/luteotropic effects via increasing PGE2 secretion by luteal tissue rather than being luteolytic.

Artificial insemination following observational versus electronic methods of estrus detection in red deer hinds (Cervus elephus)

The objectives were to determine the efficacy of the HeatWatch (HW) electronic estrus detection system for monitoring behavioral estrus (including duration and intensity) in red deer hinds and to evaluate pregnancy rate to AI after detected estrus. Red deer hinds (Cervus elephus; n = 50) were allocated into two treatment groups: AI following synchronization (CIDR/PMSG) and observed estrus (induced estrus group: IE; n = 25) or AI following the detection of natural estrus (NE; n = 25) without hormonal treatment. Hinds were fitted with two HeatWatch (HW) electronic estrus detection transmitters, one above the tail (bottom) and one between the tuber coxae of the pelvic girdle (top), and visual observations for mounting activity began with the aid of young sterile red deer stags (18 months old) fitted with marking harnesses. Hinds in both groups were inseminated (10-12h after observed estrus) with frozen-thawed red deer semen using a transvaginal/cervical AI approach. Following a 26-day period of AI, hinds were placed with a mature fertile stag for an additional 30-day natural breeding period. Pregnancy diagnosis was performed 57 and 86 days after the start of AI. While the hinds were housed with the young stags, 82% were detected in estrus by visual appraisal of stag crayon marks, but only 32% of these were detected by HW. In contrast, in the hinds housed with the mature stag, 93% detected in estrus by crayon marks were also detected by HW. The top HW transmitter consistently recorded more mounts (P < 0.05) than the bottom transmitter. The pregnancy rate was numerically better in IE versus NE hinds (42% versus 29%, P > 0.10). In summary, there were no differences (P > 0.10) in the intensity (number) or duration of mounts (detected by HW) during estrus in IE versus NE hinds, and HW was most effective in detecting estrus in the presence of a heavier, mature stag versus a younger stag. When used in combination with transvaginal AI, an overall first-service pregnancy rate of 36.6% was achieved with AI of frozen-thawed semen in red deer hinds following detected estrus.

Effects of lasalocid on circulating concentrations of leptin and insulin-like growth factor-I and reproductive performance of postpartum Brahman cows

Objectives were to determine effects of lasalocid on reproductive performance and serum concentrations of leptin and IGF-I, and to correlate concentrations of leptin and IGF-I with reproductive performance of beef cows. Forty-one purebred, multiparous Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments by BW, BCS, and predicted calving date. Treatment began 21 d before expected calving. Cows were each fed 1.4 kg daily of an 11:1 corn:soybean meal supplement, with the L group receiving 200 mg of lasalocid/cow daily. Cows and calves were weighed, and cow BCS was assessed at calving and at 28-d intervals thereafter. Blood samples were collected weekly precalving, at parturition, and twice weekly thereafter. Sterile marker bulls were maintained with cows for estrous detection. Six days after estrus, ovaries were evaluated for corpus luteum formation, and blood samples from d 6, 7, and 8 after estrus were collected. Serum samples were assayed for progesterone (P4), IGF-I, and leptin concentration. Progesterone concentrations > 1 ng/mL were considered indicative of a functional corpus luteum. Treatment ended after completion of a normal estrous cycle, and cows removed from treatment were placed with a fertile bull equipped with a chinball marker. There were no treatment differences in calving date, calf sex, cow BW, BCS, calf BW, calf ADG, or in serum concentrations of P4, IGF-I, or leptin. Prepartum cow ADG was increased (P < 0.01) in L cows and tended (P < 0.011) to be increased from calving to d 56 after calving in L cows. Postpartum interval (PPI) was not affected by treatment; however, a greater percentage (P < 0.05) of L cows conceived by 90 d after calving (43% L vs. 15% C). First-service conception rate tended (P < 0.08) to be greater in L vs. C cows (68 vs. 40%), but pregnancy rate was not different (P < 0.12; 86% for L vs. 65% for C). There were no treatment differences (P > 0.18) for serum IGF-I concentrations. At calving, leptin was positively correlated with IGF-I (P < 0.04; r = 0.32), BCS (P < 0.06; r = 0.29), and cow BW (P < 0.02; r = 0.36), and was negatively correlated with PPI (P < 0.06; r = -0.29). These results provide evidence that feeding an ionophore before calving and during the postpartum period may increase the number of cows that rebreed to maintain a yearly calving interval. Cows with higher concentrations of leptin postpartum may exhibit shorter PPI.

Effect of zeranol or melengestrol acetate (MGA) on testicular and antler development and aggression in farmed fallow bucks

Fifteen yearling fallow bucks were randomly assigned by BW to one of three treatment groups: control (C; n = 5), melengestrol acetate (MGA; n = 5), and zeranol (Z; n = 5), to evaluate effects on testicular development, aggressive behavior, antler growth, sexual activity, ADG, and BW. Zeranol-treated bucks received zeranol ear implants (36 mg) at 90-d intervals, and MGA-treated bucks received MGA in the ration (100 microg x animal(-1) x d(-1)). Bucks grazed ryegrass/Coastal bermudagrass pasture and were supplemented with 3:1 corn/soybean meal at 0.45 kg x animal(-1) x d(-1). Body weights, body condition scores (BCS), blood samples, and testis measurements were obtained at d 0 and at 14-d intervals for 229 d. As bucks reached hard antler (7/15 to 8/25), antlers were harvested and weighed, and ejaculates were collected at 14-d intervals. Aggression was evaluated using 10-min video sessions scoring body blows, avoidance, head pushes, and head bunts. Scrotal circumference (SC) and paired testis volume were affected by a day x treatment interaction (P < 0.01); testes of zeranol-treated bucks were smaller than those of control or MGA-treated bucks. First sperm in the ejaculate tended to be delayed (P < 0.10) in zeranol-treated bucks compared with control and MGA-treated bucks. Melengestrol acetate-treated bucks had a maximum sperm concentration in the ejaculate that was three times (P < 0.05) that of control bucks and nine times (P < 0.05) that of zeranol-treated bucks. Antler weight was the least (P < 0.01) for bucks receiving zeranol and greatest (P < 0.10) for MGA-treated bucks; intermediate values were recorded for the control bucks. Aggressive behavior was delayed (P < 0.05) for zeranol-treated bucks until treatment effects were overcome. Melengestrol acetate-treated bucks had decreased (P < 0.01) aggressive behavior compared with control bucks. Melengestrol acetate-treated bucks had increased (P < 0.05) serum testosterone concentrations compared with control and zeranol-treated bucks. Human chorionic gonadotropin-stimulated peak serum testosterone concentrations for zeranol-treated bucks were delayed (P < 0.01) compared with control and MGA-treated bucks. Although zeranol-treated bucks overcame treatment effects, they were never able to reach testicular measurements or sperm concentrations equal to those of the control or MGA-treated bucks. Zeranol and MGA treatments may have both positive and negative effects that can be utilized when producing slaughter bucks.

Effects of dietary rice bran, lasalocid, and sex of calf on postpartum reproduction in Brahman cows

To determine the effects of dietary lasalocid and increased dietary fat on reproduction, multiparous Brahman cows (n = 68), body condition score (BCS) of 6.2 +/- 0.7 and BW of 500.9 +/- 42.6 kg, were randomly assigned within sex of calf to receive one of four rations. All treatment groups grazed Coastal bermudagrass overseeded with rye-ryegrass and were given ad libitum access to hay and water. The control (n = 17) group received 4.17 kg x d(-1) x cow(-1) of 4:1 corn:soybean meal. The rice bran (n = 17) group received 4.35 kg x d(-1) x cow(-1) of 3:1:1 corn:soybean meal:rice bran (5.2% dietary fat). The lasalocid (n = 17) group received the Control diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). The rice bran-lasalocid (n = 17) group received the rice bran diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). Diets were fed once daily from d 1 after parturition through the detection of first estrus. Weight and BCS of cows and BW of calves were recorded at 14-d intervals from d 1 after parturition through detection of first estrus and at weaning. Cows were bled on d 1, 3, 5, 7, and 14 and at weekly intervals until estrus and on d 7 and d 10 after estrus. Ovarian follicular populations were monitored by transrectal ultrasonography weekly from d 14 after parturition through detection of first estrus. Plasma 13-14-dihydro-15-ketoprostaglandin-F2alpha (PGFM) and progesterone (P4) concentrations were quantified using RIA. Concentrations of PGFM from d 1 to 7 and P4 concentrations on d 7 and 10 after estrus were not influenced (P > 0.10) by diet or sex of calf. Changes in BW and BCS were not affected (P > 0.10) by diet. The number of medium-sized follicles tended to be greater (P < 0.06) in Controls than in cows on lasalocid or rice bran + lasalocid treatments on d 21. Cumulative return to estrus with a functional corpus luteum by d 60 postpartum was greater (P < 0.02) in the rice bran (70.6%) and lasalocid groups (76.5%) than in Controls (52.9%) or the group given rice bran + lasalocid (25.0%). Normal first estrous cycles were less likely (P < 0.07) to be exhibited in cows given rice bran + lasalocid than in other groups. Intervals from calving to corpus luteum formation, functional corpus luteum, and first P4 > or = 1 ng/mL were longer (P < 0.02) in cows given rice bran + lasalocid than in other cows. Combining increased dietary fat (5.2%) with lasalocid lengthened the time to reproductively important events.

The effect of aspirin administration and parity on plasma salicylate concentrations and postpartum reproductive parameters in Brahman cows

Forty pluriparous (M) and 20 primiparous (P) suckled Brahman cows were used to evaluate the effect of aspirin and parity on plasma 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM) and progesterone (P4) concentrations and some reproductive parameters. On Day 7 after calving (PP), the cows were allocated within parity into 2 groups: the aspirin group received concentrate containing aspirin at a rate of 100 mg/kg of body weight every 12 h until Day 13 PP; and the control received concentrate every 12 h for the same interval. Blood samples were collected after first and last aspirin feeding and daily from Day 1 PP to Day 6 PP and from Day 14 PP to Day 21 PP, twice daily from Day 7 PP to Day 13 PP, and weekly until first non-return to estrus. Plasma salicylate concentrations in the aspirin group cows were affected by parity (P < 0.01) and time after feeding (P < 0.0001). P cows showed higher plasma salicylate concentrations with a later peak and slower decrease than M cows. Aspirin-treated P cows had longer PP intervals than either control P, control M, or aspirin-treated M cows. Cows receiving aspirin had a lower pregnancy rate, an increased incidence of abnormal estrous cycles, and a decline in the presence of corpora lutea after estrus. Cows that formed a corpora lutea and had received aspirin had higher P4 release between Day 6 and 14 after estrus. Aspirin-treated cows that did not form corpora lutea had lower P4 release between Days 9 and 14 after estrus. A treatment by parity interaction affected mean PGFM proportions (P < 0.01) during the treatment period. Aspirin-fed P cows increased PGFM release as measured by mean proportion of Day 6 PP values. Aspirin-fed M cows showed a decrease in mean PGFM proportions. Aspirin feeding during the early PP showed different effects on some reproductive parameters in P and M Brahman cows, indicating differences in PP physiology between parities.

Effects of induced hypothyroidism on weight gains, lactation, and reproductive performance of primiparous Brahman cows

Primiparous, spring-calving Brahman cows (BW = 425.0 +/- 13.8 kg, body condition score [BCS] = 5.0 +/- .2 units; SEM) were used to study the effects of thyroid manipulation on weight gain, milk production, and reproduction. Nine cows served as controls. Nine cows were induced to become hypothyroid by daily ingestion of 4 mg/kg BW of 6-n-propyl-2-thiouracil (PTU). Cows were stratified to treatment 1 d after calving based on season of birth, BW, BCS, calf sex, and calf sire. The treatment period lasted for 84 d and was followed by a 56-d posttreatment period. Cow BW, BCS, and calf weight were recorded twice weekly. Milk production was estimated at 14, 28, 56, 84, 98, 112, and 140 d after calving. Weekly blood samples were obtained for analysis of triiodothyronine (T3), thyroxine (T4), and progesterone (P4). Estrus was monitored twice daily with the aid of a fertile bull equipped with a chin ball marker. Hypothyroidism was effectively induced in all PTU cows during the treatment period. The PTU cows gained more (P = .002) weight (54.6 +/- 7.6 kg) and tended (P = .06) to increase body condition (.61 +/- .17 units) more than control cows (15.7 +/- 7.6 kg; .11 +/- .17 units) during the treatment period. Control calves gained at a faster rate (.85 +/- .04 kg/d; P < .01) than PTU calves (.70 +/- .04 kg/d) during the treatment period. Milk production was lower (P < .05) in PTU cows on d 56 and 84. During posttreatment all trends were reversed, and BW, BCS, calf weight, and milk production were similar between the two groups by d 140. Reproductive performance was not affected by induction of hypothyroidism. In conclusion, induction of hypothyroidism was successful in increasing cow weight and BCS gains and suppressing milk production during the treatment period, but these changes were not successful in improving reproductive performance of primiparous Brahman cows.

Effects of induced hypothyroidism or hyperthyroidism on growth and reproductive performance of Brahman heifers

Prepubertal Brahman heifers (BW = 302 +/- 7.5 kg, body condition score [BCS] = 5.4 +/- .2, age = 498 +/- 3.4 d: SEM) were used to study the effects of thyroid function on growth and reproduction. Seven heifers were controls (C). Seven heifers were induced to become hypothyroid by ingestion of 4 mg/kg BW of 6-n-propyl-2-thiouracil (PTU). Seven heifers were induced to become hyperthyroid (T) by daily s.c. injections of triiodothyronine (T3, 1 mg/d). Treatments were administered for 84 d followed by an 84 d posttreatment period. Blood samples were obtained twice weekly via tail venipuncture for analysis of T3, thyroxine, and progesterone. The BW, BCS, and rectal temperature (RT) were recorded weekly. Estrus was monitored twice daily with the aid of a fertile bull equipped with a chin ball marker. Hyperthyroidism and hypothyroidism were successfully induced in T- and PTU- treated heifers, respectively. During the treatment period, PTU heifers gained the most BW and BCS (72.4 +/- 5.4 kg; .93 +/- .15 units), C heifers were intermediate (41.7 +/- 5.4 kg; .43 +/- .15 units), and T heifers gained the least (13.3 +/- 5.4 kg; -.36 +/- .15 units; P < .05). The RT also decreased (P < .05) in PTU heifers (-1.9 +/- .2 degrees C) compared with C (-1.2 +/- .2 degrees C) or T heifers (-.8 +/- .2 degrees C). No heifers exhibited estrus during the treatment period. During the posttreatment period, T heifers gained the most BW and BCS (93.9 +/- 6.1 kg; 1.14 +/- .13 units), C heifers were intermediate (67.0 +/- 6.1 kg; .86 +/-. 13 units), and PTU heifers gained the least (22.2 +/- 6.1 kg; -.14 +/- .13 units; P < .05). The reversal in BW and BCS gains during the posttreatment period corresponded to periods of transient hypo- and hyperthyroidism in T and PTU heifers, respectively. Age and BW at puberty and pregnancy were similar among all treatment groups. The BCS for T heifers was lower (5.7 +/- .2 units; P < .05) at puberty and pregnancy than for PTU heifers (6.6 +/- .2 units). Induction of hypothyroidism resulted in significant increases in BW and BCS during the treatment period, but these increases were not sufficient to dramatically affect reproductive performance of Brahman heifers.

Hybridization between wapiti (Cervus elephus manitobensis) and sika deer (Cervus nippon): a comparison of two artificial insemination techniques

The present study compared pregnancy rates of sika deer (Cervus nippon) hinds artificially inseminated with frozen-thawed wapiti (Cervus elephus manitobensis) semen by laparoscopic intrauterine or transvaginal/cervical artificial insemination (AI) techniques. Estrous cycles of 59 sika hinds were synchronized with one-half of a norgestomet ear implant. Fourteen days after implant insertion, norgestomet ear implants were removed and hinds received 50 IU of PG-600 intramuscularly, a combination of 50 IU PMSG and 25 IU hCG. Hinds were then randomly allotted for laparoscopic (n = 25) or transvaginal/cervical (n = 34) AI. AI of the hinds with frozen-thawed wapiti semen (40 x 10(6) spermatozoa) was time-fixed to occur at 55 hr for transvaginal/cervical AI and 65 hr for laparoscopic AI postnorgestomet implant removal. Semen deposition for hinds inseminated by transvaginal/cervical AI occurred as follows: vagina. 8.8% (3/34); os cervix, 67.6% (23/34); intracervical, 20.5% (7/34); and uterus, 2.9% (1/34). On day 42 post-AI, transrectal ultrasonography was performed to determine pregnancy rates. Pregnancy rates were not significantly different (P > 0.10) between laparoscopic (8/25, 32.0%) and transvaginal/cervical AI (9/34, 26.4%), with an overall conception rate of 28.8% (17/59). These results indicate that transvaginal/cervical AI techniques can be as effective as laparoscopic AI under some circumstances. Further refinement of the transvaginal/cervical AI technique to improve pregnancy rates might lead to more widespread use of this technique when laparoscopic AI is not possible.

Early pregnancy detection and the hormonal characterization of embryonic-fetal mortality in fallow deer (Dama dama)

The objectives of this investigation were to 1) determine serum concentrations of progesterone (P4), estrone sulfate (E1S) and pregnancy-specific protein B (PSPB) from estrus synchronization through mid-gestation in the fallow doe (Dama dama) and 2) characterize the hormonal profiles of does whose embryos or fetuses died in utero. Ten fallow does were synchronized for 14 d with an intravaginal P4-releasing device (CIDR) and were naturally mated after CIDR removal. Blood samples were collected at CIDR insertion, CIDR removal and at intervals through Day 203 post-CIDR removal for analysis of P4, E1S and PSPB by radioimmunoassay (RIA). Ultrasonography was performed on Days 49 and 69 post-CIDR removal. Serum P4 at the time of CIDR insertion was 4.8 +/- 0.6 ng/ml, and at CIDR withdrawal it was 6.2 +/- 0.3 ng/ml. Concentrations of E1S and PSPB were nondetectable at CIDR insertion. Serum E1S was highest at Day 93, and PSPB was first detectable in pregnant does at Days 27 to 30 post-CIDR withdrawal. Ultrasonography on Day 49 revealed that 6 does were pregnant, 2 were not pregnant and 2 others were diagnosed originally as early pregnant. At Day 69, ultrasonography revealed that 6 does (60%) were pregnant and 4 (40%) were not. A comparison of the ultrasonographic and hormonal data indicated that the 2 does diagnosed as early pregnant on Day 49 had conceived but had lost the pregnancy. A third doe which was pregnant on Day 69 lost the fetus later in gestation. Hormonal profiles of does whose embryo or fetus had died were characterized by erratic P4 and E1S profiles, with PSPB becoming undetectable in the 3 does by Days 49, 65 and 80 post-CIDR removal. These data 1) demonstrate the timing for the collection of serum samples for determining early pregnancy in fallow does using 3 hormonal methods and 2) characterize the hormonal profiles of 3 fallow does with embryonic-fetal loss.

Fat supplementation influences postpartum reproductive performance in Brahman cows

Multiparous Brahman cows (n = 40) in excellent body condition (6.5+/-.1) were randomly assigned to receive either 5.2 (rice bran) or 3.7% (control) dietary fat after calving. The experimental diets were formulated to be isocaloric and isonitrogenous. The experimental diets were fed twice daily from d 1 after calving through the first normal estrous cycle. Cows were weighed, scored for body condition, and bled at weekly intervals from d 1 through 50 after calving. Weekly bleedings continued until the first detectable estrus. Blood samples were collected daily throughout the first normal estrous cycle. All cows were exposed to a fertile bull at the estrus following the first normal estrous cycle and for a 60-d breeding season. Ovarian follicular populations were recorded weekly by transrectal ultrasonography from d 15 to 50 after calving. Calf weights were recorded at 14-d intervals from d 1 to 43 after birth and at weaning (205 d). Cows receiving rice bran gained more body condition (P < .05) than cows receiving the control supplement. The numbers of small (< 4.0 mm, P < .05), medium (4.0 to 7.9 mm, P < .05) and total follicles (P < .05) were greater in the rice bran than in the control group from 15 to 29 d after calving, and large follicles ( > or = 8.0 mm) increased in number (P < .05) and the largest follicle increased in size (P < .001) over time regardless of the level of dietary fat. Fat supplementation increased the numbers of medium (P < .01), large (P < .05), and total (P < .01) follicles and size of the largest follicle (P < .05) during the 3 wk before the first normal estrous cycle. The intervals from parturition to reproductively important end points were similar (P > .10) between dietary treatments as well as the percentage of cows showing normal or abnormal estrous cyclic activity. Treatment did not affect (P > .10) daily serum progesterone (P4) concentrations. However, there was a tendency (P = .09) for more rice bran-supplemented cows to be pregnant (94.1 vs 71.4%) after being exposed to a fertile bull for 60 d. Calf weight gain tended to be higher (P = .08) in calves nursing rice bran-supplemented dams. In conclusion, using rice bran, with high concentrations of oleic and linoleic acids, as a fat supplement for postpartum cows enhanced ovarian follicular growth before normal estrous cycles resumed and increased body condition scores and pregnancy rates without altering postpartum interval or serum P4 concentrations.

Influence of hypo- or hyperthyroidism on ovarian function in Brahman cows

Multiparous Brahman cows (n = 21) were randomly assigned during late fall within BW and body condition score (BCS) to receive either 3.0 mL of corn oil (C; n = 7), 3.0 mg/(cow x d) triiodothyronine (T3) s.c. in 3.0 mL of corn oil (HYPER; n = 7), or 4.0 mg/(kg x d) 6-n-propyl-2-thiouracil (PTU; fed with concentrate) plus 3.0 mL/d corn oil (HYPO; n = 7). Water, minerals, and Coastal bermudagrass hay were available free choice, and all cows received 3.2 kg x cow(-1) x d(-1) of 5:1 corn:soybean meal concentrate. The feeding period extended through three normal estrous cycles. Blood samples were collected weekly during the first and second estrous cycle, or until d 42 for anestrous cows, and daily throughout the third cycle. Also, between d 9 and 14 of the third cycle, or after d 35 in anestrous cows, intensive samples were collected at 2-h intervals for 24 h. Serum T3, thyroxine (T4), and progesterone (P4) were measured in weekly and intensive samples, and cortisol, insulin, GH, and thyroid-stimulating hormone (TSH) were measured in intensive samples. The altered thyroid status of HYPER and HYPO cows was evident (P < .001) during the third estrous cycle in mean daily T3, T4, and intensive TSH (P < .001) concentrations. Changes in BW and BCS were influenced by treatment (P < .001). A greater (P < .001) proportion of HYPER cows exhibited abnormal cycle length, and three of seven cows became anestrous. For cows that continued normal cycles, treatment did not affect (P > .05) the number of follicular waves, diameter of the dominant follicle, diameter of the ovulatory follicle, or P4 profiles during the third cycle. Insulin and GH concentrations did not differ (P > .05) among treatments in intensive samples, but, mean cortisol was greatest (P < .02) in HYPER cows. For Brahman cows that maintained normal estrous cycles, induced hyper-or hypothyroid status did not influence ovarian function.

Effects of prenatal stress on suckling calves

Pregnant Brahman cows (n = 42), bred to either Brahman or Tuli bulls, were randomly assigned to one of three treatments: 1) transported in a stock trailer for 24.2 km, unloaded at a second farm and penned for 1 h, and then returned to the original farm (TRANS); 2) i.v. injection of ACTH, 1 IU/kg BW (ACTH); or 3) walked through the handling facilities (SHAM). Treatments were initiated on d 60 and repeated at 80, 100, 120, and 140 d of gestation. The calves from these cows were subjected to tests to measure their capacity to react to stress. In Test 1, Tuli-sired calves were restrained at 10 and 150 d of age for 3.5 h. In Test 2, Brahman-sired calves were restrained for 3.5 h and given an injection of ACTH (.125 IU ACTH/kg of BW). In Test 3, Test-2 calves were restrained at 180 d of age and hot-iron branded. In Test 4, Test-1 calves were restrained at 180 d of age and given an injection of cortisol (6.7 ng/kg BW) to estimate cortisol clearance rate. During all tests, calves were restrained for 3.5 h, and heart rates were recorded and blood samples were taken at -15, 0, 15, 30, 45, 60, 90, 120, and 180 min. The 10- and 150-d-old TRANS calves maintained greater plasma cortisol in Test 1 (restraint) than the ACTH and SHAM calves (P < .01). The ACTH challenge (Test 2) increased plasma cortisol and ACTH, but cow treatment did not alter the response (P > .4). In response to branding (Test 3), the TRANS, ACTH, and SHAM calves' overall mean plasma cortisol was not affected by treatment (52, 51, and 43 +/- 3 ng/mL, respectively; P > .1), nor was the calves' overall heart rate (91, 94, and 86 +/- 3 beats/min, respectively; P > . 1). In Test 4, TRANS calves cleared plasma of cortisol at a slower rate than did the SHAM calves (P < .01), but not the ACTH calves (261, 374, and 473 +/- 50 mL/min, respectively; P > .1). The TRANS calves had an overall greater heart rate than did the ACTH or the SHAM calves (91, 79, and 77 +/- 2 beats/min, respectively; P < .001). Exposing cows to repeated transportation stress during gestation altered their calf's physiological response to stress, and these alterations could have a profound influence on the calfs ability to adapt to stress, thereby influencing its welfare. Further research should examine the growth, immune function, and reproductive function of prenatally stressed calves to determine whether these changes in plasma cortisol are beneficial or deleterious.

Effects of prenatal stress on the fetal calf

Twelve pregnant Brahman cows were randomly assigned to one of two treatment groups: 1) transported in a stock trailer for 24.2 km, unloaded at a second farm and penned for 1 hr, and then returned to the original farm (TRANS, n = 6); or 2) walked through the handling facilities (SHAM, n = 6). Treatments were repeated at 60, 80, 100, 120, and 140 d of gestation. Calves were delivered by cesarean section on d 266 of gestation. The male:female ratio was 4:2 and 5:1 for the TRANS and SHAM treatment groups, respectively. Before calf removal and severance of the umbilical blood flow, a blood sample was collected from the calf to determine plasma concentrations of adrenocorticotropin (ACTH) and cortisol. The calf was then sedated and exsanguinated, after which pituitary and adrenal glands were collected. The adrenals were immediately weighed, and a cross-section from the left adrenal was stored in 4% paraformaldehyde until being embedded in paraffin. Eight sections from each adrenal were sliced (5 microns), fixed, and then stained with Harris' hematoxylin and eosin. Areas of the cortex and medulla were calculated with a computerized digitizing unit and tracing of the viewed section. The TRANS calves had heavier body weights (BW) (28.7 vs. 23.9 +/- 1.8 kg; P < 0.07), pituitary glands (12.63 vs. 8.24 +/- 1.10 g/kg BW; P < 0.008), and heart weights (5.58 vs. 5.17 +/- 0.58 g/kg BW; P < 0.05) than did the SHAM calves. Plasma concentrations of ACTH and cortisol did not differ between SHAM and TRANS calves (57 vs. 82 +/- 14 pg/ml and 7.0 vs. 6.7 +/- 0.9 ng/ml, respectively; P > 0.2). Adrenal gland weight and medulla-to-cortex ratio did not differ between SHAM and TRANS calves (0.61 and 0.73 +/- 0.03 g and 0.97 and 0.99 +/- 0.12 g, respectively; P > 0.2). These results suggest that the altered response to stress in prenatally stressed calves is not associated with morphological changes in the adrenal gland but may be due to effects of prenatal stress on the fetal pituitary.

Adrenocorticotropic hormone dose response and some physiological effects of transportation on pregnant Brahman cattle

The appropriate dose and the ability of exogenous ACTH to mimic the physiological effects of a real stressor need to be determined. In Exp. 1, 25 pregnant Brahman heifers were injected i.v. with either 0 (saline), .125, .25, .5, or 1 i.u. of ACTH/kg BW. Plasma cortisol was determined in blood samples collected during a 5-h period, and an integrated cortisol response was calculated for each cow. The greater the dose of ACTH, the greater was the integrated cortisol response (P < .001). However, peak plasma cortisol in response to the four doses of ACTH did not differ (P > .6). The plasma cortisol concentrations returned to baseline more slowly in those cows receiving the greater doses of ACTH, making their integrated areas of response greater. In Exp. 2, pregnant Brahman cows were either transported 48 km (n = 28), injected with 1 i.u. of ACTH/kg BW (n = 21), or served as shams (n = 28). Each treatment was repeated at 60, 80, 100, 120, and 140 d of gestation. Shrink was greater for the transported cows than for either the ACTH-treated or sham cows, 14.3, 6.0, and 5.2 kg (P < .001). Shrink also decreased in response to each subsequent application of treatment for all three treatment groups (P < .001). Transported cows had lower plasma cortisol concentrations after the first two applications of treatments (P < .006). The range of doses of ACTH caused a similar peak cortisol release; however, it took cortisol longer to return to baseline as ACTH dose increased. Repeated administration of exogenous ACTH did not cause the same amount of shrinkage as transportation, and the resultant cortisol concentrations remained consistent for each administration. There was no apparent carryover effect of repeated administration of ACTH at 20-d intervals. Maximal plasma cortisol concentrations in Brahman cattle can be obtained with doses of ACTH much smaller than those traditionally injected. However, larger doses of ACTH maintained plasma cortisol concentrations for a longer duration. Repeated transportation caused a decrease in cortisol release and shrinkage indicative of psychological habituation. Injections of ACTH did not cause the same physiological response as transportation.

Exogenous PGF2α enhanced GnRH-induced LH release in postpartum cows

This study evaluated the effect of exogenous PGF(2)alpha on circulating LH concentrations in postpartum multiparous (n = 32) and primiparous (n = 46) Brahman cows. The cows were randomly allotted within parity and calving date to receive 0, 1, 2 or 3 mg im PGF(2)alpha (alfaprostol)/100 kg body weight (BW), with or without GnRH on Day 30 after calving. Blood samples were collected at weekly intervals from calving through treatment. Serum progesterone concentrations were determined using RIA procedures to assure that only anestrous cows were treated. Sterile marker bulls were maintained with cows on Coastal bermudagrass pastures until the first estrus was detected. Multiparous cows had a shorter (P < 0.05) interval from calving to estrus than did primiparous cows. Serum LH was affected by time (P < 0.0001), PGF(2)alpha dose (P < 0.0002), GnRH (P < 0.0001), parity by PGF(2)alpha dose (P < 0.0003), PGF(2)alpha dose by GnRH (P < 0.0009), parity by GnRH (P < 0.0008), and by parity by PGF(2)alpha dose by GnRH (P < 0.0005). Multiparous cows not receiving GnRH had higher mean serum LH (P < 0.02), LH peak pulse height (P < 0.03), and area under the LH release curve (P < 0.03) compared with primiparous cows. The number of LH pulses/6 h was greater (P < 0.06) in multiparous than primiparous cows, and was greater (P < 0.02) in multiparous cows receiving 3 mg/100 kg BW than in cows receiving 2 mg/100 kg BW, but not in the controls or in cows receiving 1 mg/100 kg BW. Exogenous GnRH resulted in increased (P < 0.0001) serum LH concentrations in all cows, and LH was enhanced (P < 0.0009) by simultaneous treatment with PGF(2)alpha. Primiparous cows had a greater response (P < 0.0005) to PGF(2)alpha and GnRH compared with multiparous cows. Pituitary release of LH in response to GnRH was enhanced by simultaneous exposure to PGF(2)alpha in Day 30 postpartum cows.

Testicular and epididymal function during the peripuberal period in Brahman bulls receiving various amounts of protein degradable in the rumen

Thirty-nine Brahman bulls with an initial age and weight of 301.7 +/- 4.1 d and 202.7 +/- 4.7 kg, respectively, were randomly allocated to 1 of 2 dietary treatment groups within age, weight and sire in order to study the influence of source of protein and stage of peripuberal period on testicular and epididymal function. In the soybean meal treatment the amount of protein undegradable in the rumen averaged 47%, while it was 72% in the fish meal treatment. The supplements were isocaloric and isonitrogenous. Bulls were electroejaculated, and castrations were performed randomly in a predetermined order when the first ejaculate with the first motile sperm cells (Stage 1), 10 to 25 million (Stage 2), and 50 million or more sperm cells (Stage 3 - puberty) was obtained. Testicular and epididymal traits were analyzed for a single testicle and epididymis. Daily sperm production, daily sperm production per gram of testicular parenchyma, testicular weight and testicular parenchyma weight were not affected by treatment. Bulls receiving fish meal had heavier (P < 0.01) epididymis than soybean meal-fed bulls (6.6 +/- 1.0 vs 3.9 +/- 0.6 g) but similar (P > 0.05) epididymal sperm reserves. Daily sperm production (1 testicle) was 115.2 +/- 0.1, 447.4 +/- 0.1, 792.7 +/- 0.1 million sperm cells, and daily sperm production per gram of testicular parenchyma was 1.5 +/- 0.5, 3.2 +/- 0.6 and 6.4 +/- 0.6 million sperm cells for bulls at Stage 1, 2 and 3, respectively. Sire and amount of undegradable intake protein had significant (P < 0.05) affects on the distribution of epididymal sperm reserves, with soybean meal-fed bulls having the higher proportions of epididymal sperm reserves in the cauda epididymis.

Influence of undegraded intake protein supplementation on milk production, weight gain, and reproductive performance in postpartum Brahman cows

Eighty first-calf Brahman heifers and 51 mature Brahman cows were allotted to one of three diets based on parity, sex of calf, and breed of calf sire (Angus, Brahman, or Tuli) to evaluate rumen undegraded intake protein's (UIP) influence on production characteristics and reproductive performance. Supplements contained either 38.1% (low), 56.3% (medium), or 75.6% (high) UIP. Supplements were given from d 7 to 119 after calving to dams grazing rye-ryegrass overseeded Coastal bermudagrass pastures and with access to Coastal bermudagrass hay. Dam and calf BW and dam body condition score were recorded on d 7, 35, 63, 91, and 119 after calving. Four-hour milk production was recorded on the above days for low (n = 18), medium (n = 19), and high (n = 18) UIP animals and on d 7 and 35 for the entire group. Blood for progesterone RIA was drawn weekly and on d 6, 8, 10, and 12 after an observed estrus. Medium UIP heifers produced more (P < .02) milk (1.18 +/- .07 kg/4 h) than high UIP heifers (.94 +/- .07 kg/4 h), but milk production in mature cows was not influenced by diet. Low UIP dams had lower (P < .04) first-service conception rates (29.2%) than medium (57.6%) and tended (P < .10) to have lower rates than high UIP dams (54.6%). Overall pregnancy rates tended (P < .10) to be higher in medium (61.5%) and high (56.4%) UIP groups than in the low (43.2%) UIP group. Supplementing UIP at the medium rate improved first-service conception rates and tended to improve pregnancy rates.

Preweaning growth of Angus- (Bos taurus), Brahman- (Bos indicus), and Tuli- (Sanga) sired calves and reproductive performance of their Brahman dams

Calves born to Angus (A), Brahman (B), or Tuli (T) bulls and B cows were evaluated to determine sire breed of calf effects on preweaning calf growth and reproductive performance of their dams. Records from 242 cow-calf pairs over 2 yr were used to assess birth weight, calf ADG, weaning weight, gestation length, and postpartum interval to estrus (PPI). The sire breed x sex of calf interaction was important (P < .05) for birth weight, weaning weight, and gestation length. Birth weights of BB males (32.8 +/- .8 kg) were significantly heavier than for AB and TB males (30.1 +/- .9 and 28.6 +/- .7 kg, respectively) and BB females (29.4 +/- .7 kg). As a main effect, sire breed of calf affected (P < .05) calf ADG, weaning weight, gestation length, and PPI. Calf ADG and weaning weights were greater for AB (.90 +/- .01 kg/d; 220.9 +/- 3.5 kg) than for TB (.81 +/- .01 kg/d; 200.4 +/- 3.0 kg) and BB calves (.78 +/- .01 kg/d; 198.8 +/- 3.5 kg). Gestation lengths differed (P < .01) among all calf genotypes (284, 288, and 294 +/- 1 d for AB, TB, and BB, respectively). Postpartum intervals were shorter (P < .05) for cows nursing BB calves (83 +/- 4 d) than for cows nursing AB (95 +/- 5 d) and TB calves (97 +/- 4 d). Tuli-sired F1 calves were inferior to Angus-sired F1 calves and similar to straightbred Brahman calves in preweaning growth. Crossbred calves had shorter gestations but longer postpartum intervals than purebred calves.

Influence of maternal and service-sire breed on serum progesterone and estrogen before calving and plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha after calving

Effects of breed of service sire and cow on birth weight and prepartum and postpartum endocrine function were studied in multiparous Brahman (n = 20) and Angus (n = 20) cows bred to Brahman or Angus bulls. Before calving, blood samples were collected on d 34 to 28, 27 to 21, 20 to 14, and 13 to 7, and after calving, samples were collected from d 0 to 7. Progesterone (P4), estrogen (E2), and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were quantified with RIA. Calves born to Brahman were smaller (P < .05) than calves born to Angus cows. Prepartum concentrations of P4 were greater in Angus cows and decreased more rapidly near parturition than in Brahman cows (breed of dam x period; P < .03). Cows bearing bull calves had greater concentrations of P4 on d 20 to 14 before calving than cows bearing heifer calves (sex of calf x period; P < .04). Prepartum E2 was influenced (P < .05) by the breed of dam x breed of sire x period interaction. The ratio of P4:E2 tended to decrease more in Angus than in Brahman cows near parturition (breed of dam x period; P < .09). Postpartum PGFM tended to be influenced (P < .08) by breed of dam x breed of sire; from d 3 to 5, Brahman cows bred to Angus bulls tended (P < .08) to have greater PGFM than Brahman cows bred to Brahman bulls or than Angus cows bred to Brahman or Angus bulls.2+ f1p4

Effects of free gossypol in the diet of pregnant and postpartum Brahman cows on calf development and cow performance

Pregnant Brahman cows (n = 38) and heifers (n = 12) were assigned, 90 d before expected calving dates, to one of three treatment groups: 1) 0 g of free gossypol(FG).animal-1.d-1 (FGHD) from soybean meal (SBM), controls; 2) 2 g of FGHD from SBM and cottonseed meal (CSM), low FG; or 3) 4 g of FGHD from CSM, high FG, to determine the effects of dietary FG on prepartum and postpartum cow performance, calf development, and selected blood variables. Prepartum and postpartum cow BW, 4-h milk production, and calf BW were similar (P > .10) among treatments. Following 84 d of treatment, cows receiving 4 g of FGHD tended (P < .10) to have greater erythrocyte fragility (EF) than cows given 0 or 2 g of FGHD. Mean EF for the 112-d postpartum period were greater (P < .05) in cows given 4 than in those given 0 g of FGHD. Dietary FG consumption by the dam did not affect (P > .10) calf EF. Serum triiodothyronine (T3) and thyroxine (T4) in cows and T4:T3 ratio in calves were similar (P > .10) among treatments. After 84 d of treatment, cows receiving 4 g of FGHD had lower (P < .05) serum concentrations of alpha-tocopherol and beta-carotene than cows given 0 g of FGHD. At parturition, serum alpha-tocopherol and beta-carotene were similar (P > .10) for all cows and calves. On d 7 and 28 after calving, alpha-tocopherol tended to be lower (P < .10) and beta-carotene was lower (P < .05) in calves given 4 than in those given 0 g of FGHD. Calf metacarpal medial cortex tended to be greater (P < .10) in calves from cows given 0 than in those from cows given 2 or 4 g of FGHD, and the lateral cortex (treatment x sex; P < .05) was smaller in male calves from cows given 4 than in those from cows given 0 g of FGHD but was not affected in female calves. By 96 to 105 d after calving, a greater number of (P < .05) cows consuming 4 and 2 g of FGHD experienced luteal activity, and a greater (P < .10) number than of cows receiving 0 g of FGHD had conceived by 112 d after calving. In summary, pre- and postpartum consumption of FG may have impaired some aspects of calf skeletal development and vitamin metabolism, although long-term performance of cows and calves was not affected.

Effects of postpartum nutrition and once-daily suckling on reproductive efficiency and preweaning calf performance in fall-calving Brahman (Bos indicus) cows

Brahman cows were used to evaluate the effects of postpartum nutrition and suckling on reproductive and calf performance. Cows received high or low TDN and once-daily or unrestricted suckling. High TDN (H; 111% of NRC recommendation) cows received a 75% corn: 25% soybean meal diet. Low TDN (L; 93% of NRC recommendation) cows received no concentrates. Once-daily suckled (restricted, R) cows nursed calves for 30 min/d starting at d 21 after calving. In the unrestricted (U) suckling groups, calves had continuous access to cows. By 2 wk of suckling restriction, more (P < .01) R than U cows had progesterone concentrations of > or = .7 ng/mL (55 vs 0%) and more (P < .05) HR than LR cows had progesterone concentrations > or = .7 ng/mL (70 vs 40%). All groups had increases in progesterone and 13,14-dihydro-15-keto-prostaglandin F2 alpha before estrus. The interval to first estrus was shorter (P < .01) for R than for U cows (42 vs 65 d). By d 42 postpartum, more (P < .01) R than U cows exhibited estrus (67 vs 0%), and more (P < .05) HR than LR cows exhibited estrus (89 vs 44%). Calving interval was shorter (P < .01) for R than for U cows (361 vs 395 d). Initial ADG were lower (P < .01) for R than for U calves (.02 vs .69 kg), but weaning weights were similar. Once-daily suckling permitted ovarian activity, hastened return to estrus, and reduced calving interval without reducing weaning weights. Increased postpartum energy intake enhanced the response to restricted suckling.

Concentrations of 13, 14-dihydro-15-keto-prostaglandin F2α, estradiol-17β and progesterone during the peripubertal period in heifers

Twenty prepubertal Holstein heifers were utilized to assess plasma 13, 14-dihydro-15-keto-prostaglandin F(2)alpha (PGFM), serum progesterone (P(4)) and estradiol-17beta (E(2)) concentrations as well as the E(2):P(4) ratio during the onset of puberty in cattle. All animals were maintained as a group along with a sterile marker bull to assist in the detection of estrus. Upon detection of the first estrus (Day=O), daily blood samples were collected from a jugular vein until the heifers had completed 3 estrous cycles. The average body weight and age at first estrus were 247.6+/-4.8 kg and 304.0+/-7.5 days, respectively. Frequency of abnormal length estrous cycles was greater (P<0.02) during the first (40%) and second (35%) cycles than during the third estrous cycle (0%). All heifers had normal cycle lengths (18 to 24 days) by the third estrous cycle. Serum P(4) was greater during the third cycle (P<0.05) from Day 10 to Day 4 before the next estrus compared with the same period of the first estrous cycle. Serum E(2) did not peak until the day of estrus in the first cycle, whereas E(2) reached a maximal level 2 days before estrus in the third estrous cycle. Serum E(2) was higher (P<0.0001) 2 days before estrus in the third cycle than in the first estrous cycle. Plasma PGFM reached maximum concentrations 3 days before estrus in the third cycle compared with 1 day before estrus at the end of first estrous cycle. As estrus approached during the third cycle, PGFM rose 1 day before E(2) rose and P(4) declined, while the rise in PGFM and E(2) occurred simultaneously, with P(4) declining at the end of the first estrous cycle. During diestrus, the E(2):P(4) ratio was lower (P<0.07) in the third cycle than in the first, but it was higher (P<0.04) at estrus and 1 day before in the third estrous cycle. These data reveal a high incidence of abnormal length estrous cycles during the first two estrous cycles of the peripubertal period, and demonstrate anomalies in uterine and ovarian endocrine activity during the peripubertal period in cattle.

Plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha concentrations in prepubertal dairy heifers challenged with oxytocin

Twenty-nine prepubertal Holstein heifers were assigned by age to one of three age groups to determine if the prepubertal bovine uterus could respond to an oxytocin stimulus. Group 1 heifers were 6 to 7 months of age (AGE1; n = 11), group 2 heifers were 8 to 9 months of age (AGE2; n = 11) and group 3 heifers were 10 to 11 months of age (AGE3; n = 7). Blood samples were collected via an indwelling jugular catheter. Four samples were collected at 15-min intervals prior to oxytocin administration to determine basal 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations. Each heifer received 100 IU of oxytocin i.v., blood sampling continued at 5 min intervals for the next 30 min and for an additional 90 min at 15-min intervals. Heifers were considered responders to oxytocin if mean PGFM concentrations increased at least 1.5 times the SD of their basal PGFM concentration. Age of the heifer (P less than .0001) and responder status (P less than .05) affected plasma PGFM. Plasma PGFM was higher in AGE1 and AGE3 heifers than AGE2 (P less than .0001). The number of responders was greatest at AGE3 (P less than .03) with AGE1 and AGE2 being similar. Mean basal PGFM was lower (P less than .04) at AGE2 than AGE1 with AGE3 being intermediate. In addition, basal PGFM at AGE1 tended to be lower (P less than .08) in the responders than in the non-responders, while AGE2 basal PGFM did not differ between responders and non-responders (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of lasalocid on the GnRH-induced LH and testosterone release during puberal development in the Brahman bull

To determine the effect of lasalocid on endocrine patterns associated with puberty, 12 half-sib prepuberal Brahman bulls were allotted by age and weight (174 to 256 d of age; 141 to 243 kg) to control or lasalocid treatments. Bulls in the control treatment were fed a 4:1 corn:cottonseed meal concentrate plus Coastal bermudagrass hay to which the bulls were given ad libitum access. The lasalocid treatment was identical except for the addition of 200 mg of lasalocid.animal-1.d-1. Blood samples were collected frequently before and after GnRH (200 micrograms, i.m.) on d 7, at 28-d intervals thereafter, and within 14 d after puberty (defined as 50 x 10(6) sperm cells with 10% motility). By d 7, bulls fed lasalocid released more LH (P less than .05), but not testosterone (T;P greater than .10), in response to GnRH than controls. At the time that the first sperm cells were observed in an electroejaculate (FS), lasalocid-fed bulls released more (P less than .05) LH and T than controls. At puberty, there was no difference (P greater than .10) between treatments in amount of T released, although lasalocid-fed bulls released more LH (P less than .05). Before puberty, concentrations of LH were positively correlated with concentrations of T in samples collected 1 and 2 h later. Both groups of bulls exhibited a linear increase in T response with advancing age (P less than .005). Release of LH decreased with age in the control bulls (P less than .10) but was unaffected by age in lasalocid-fed bulls. Both groups showed a decreased (P less than .001) LH:T response ratio with advancing age. Results of this study with bulls confirm previous reports in heifers of the enhancing effect of an ionophore on reproductive function.

Physiological responses of newborn Bos indicus and Bos indicus x Bos taurus calves after exposure to cold

Brahman (n = 9) and 1/2 Simmental x 1/4 Brahman x 1/4 Hereford (n = 11) calves were utilized to determine the influence of exposure to cold on the physiology of the neonate. All calves were removed from their dams within 20 min of birth and prior to suckling. Calves were assigned randomly within breed to either a warm (W; 31 degrees C) or cold (C; 4 degrees C) environmental treatment group. Jugular blood samples were collected via indwelling catheters at 20-min intervals for 180 min. At 100 to 120 min of sampling, all calves were given 1.2 liters of colostrum from their dams via stomach tube. At 120 min, C calves were placed in the W environment. Calf vigor score (CVS) and rectal temperature were determined at each time blood was collected. Serum or plasma was analyzed for glucose (GLU), lactate (LAC), blood urea nitrogen (BUN), hemoglobin (HEM), triglyceride (TRG), triiodothyronine (T3), thyroxine (T4), insulin (INS), cortisol (CORT) and nonesterified fatty acid (NEFA) concentration. Rectal temperature was lower (P less than .01) in C Brahman than in W Brahman and C or W crossbred calves. Crossbred calves had higher (P less than .01) CVS than Brahman calves. Calves in W had lower (P less than .01) GLU than C calves. Brahman calves had higher GLU, LAC, BUN, TRG, T3, T4 and CORT (P less than .05) than crossbred calves. The C Brahman calves had the highest (P less than .05) TRG, CORT, T3 and T4 of all groups. Concentration of NEFA were higher (P less than .01) in C than in W calves.(ABSTRACT TRUNCATED AT 250 WORDS)