13 MOTILITY CHARACTERISTICS OF SPERMATOZOA FROM BULLS GRAZING TALL FESCUE PASTURES

Fertilisation is less than expected with spermatozoa from bulls consuming toxic endophyte-infected (E+) tall fescue. The objective of this study was to evaluate motility characteristics of spermatozoa from bulls grazing tall fescue pastures using computer-assisted sperm analysis (CASA). Semen was collected from six Angus bulls (average age = 15.1 ± 0.04 months) during a three-month grazing study. Bulls grazed Kentucky 31 tall fescue (Festuca arundinacea Schreb.) infected with Neotyphodium coenophialum, an ergot alkaloid-producing endophyte (n = 3), or Jesup tall fescue with Max-Q™ (NTE), a non-ergot alkaloid producing endophyte (n = 3), and grouped by body weight and scrotal circumference to graze pastures from April 18 to June 26. Semen was collected once per week between 0600–0800 h beginning in mid-May and ending the last week of June. Gross motility and morphology was evaluated before extending with Bioxcell® animal protein-free formula (IMV, Aigle, France) and antibiotics (CSS 100, 2% of total volume). Extended semen was then evaluated using CASA to determine final dilution and packaged into straws (20 million sperm/straw), where equilibration occurred over 3 h in a cold room at 4°C. Straws were frozen for 7 min in static vapor of liquid nitrogen and plunged into goblets filled with liquid nitrogen. Semen was thawed and assessed using CASA at 0 and 3 h post-thaw. Data were analysed as a randomised block design with the fixed effects of treatment, blocking on semen collection date, utilising the mixed models procedure of SAS 9.2 (SAS Institute Inc., Cary, NC, USA). Data were tested for normality (Shapiro-Wilk W ≥ 0.90), and treatment differences were determined using F-protected least significant differences. Path velocity (P = 0.001) and progressive velocity (P = 0.003) were lower in spermatozoa from bulls grazing E+ during the last 2 weeks of collection in June independent of time of assessment post-thaw. Sperm head area decreased in size in spermatozoa from E+ grazing bulls at 3 h post-thaw (P = 0.04) compared with NTE grazing bulls. Percent of rapid (progressive % with path velocity >50 μm s–1) and medium (progressive % with path velocity <50 μm s–1 but > 30μm s–1) velocity spermatozoa was decreased for E+ grazing bulls compared to NTE grazing bulls (P < 0.0001 and P = 0.004, respectively) and was accompanied by an increase in static (immobile) spermatozoa from E+ bulls (P < 0.0001). These findings indicate that spermatozoa movement and velocity are impaired in bulls grazing E+ tall fescue pastures compared to bulls grazing NTE tall fescue pastures after the freeze and thaw process, which may explain decreased fertilisation and cleavage rates of oocytes co-incubated with these spermatozoa.

Evaluation of a modification of the McKinnon technique to correct urine pooling in mares

The urethral fold of 30 mares was split transversely into dorsal and ventral shelves, and the ventral shelf was used to help create a urethral extension. The dorsal shelf was stretched caudally and sutured to the roof of the extension so that it covered at least the cranial half of the extension. For 20 mares, a relaxing, vaginal incision was created cranial to the external urethral orifice to enable the dorsal shelf to be retracted further caudally. Ten of the 30 mares (33.3 per cent) developed a defect, but none developed a defect in that portion covered by the dorsal shelf of the urethral fold. Two of the 30 mares (6.7 per cent) developed a defect so small that the defect could be detected only by inserting a dye, under pressure, into the tunnel. The total number of mares that developed only a grossly visible and palpable defect was eight of 30 (26.6 per cent). Four of the 10 mares that did not receive the relief incision and six of 20 mares that did receive the relief incision developed a defect in the extension. Modifying the McKinnon technique by transversely splitting the urethral fold and retracting the dorsal half helps prevent a defect from forming in the cranial portion of the extension. The dorsal shelf can be retracted further caudally by creating a relief incision on the floor of the vagina.

181 FERTILIZATION CHARACTERISTICS OF SPERMATOZOA FROM BULLS GRAZING TALL FESCUE PASTURES

Fertilization with spermatozoa from bulls ingesting elevated concentrations of ergovaline [i.e. consumption of toxic endophyte-infected (E+) tall fescue] results in reduced cleavage rates. Thus, the objectives of the current study were to evaluate motility and penetration rates of spermatozoa from bulls grazing tall fescue pastures and intracellular calcium (Ca2+) parameters of presumptive zygotes (PZ). During a 3-month study, 6 Angus bulls (average age = 15.1 ± 0.04 months) were appointed to graze Kentucky 31 tall fescue (Festuca arundinacea Schreb.) infected with Neotyphodium coenophialum, an ergot alkaloid-producing endophyte (n = 3), or Jesup tall fescue infected with non-ergot alkaloid-producing endophyte (NTE) MaxQ™ (n = 3). Bulls were grouped by bodyweight (BW) and scrotal circumference (SC) to graze pastures from April 18 to June 26. Blood samples, BW, SC, semen and rectal temperatures (RT) were collected every 7 days. Semen was evaluated for gross motility, morphology and computer assisted semen analysis (CASA) parameters. Semen from a subset of bulls (n = 2 per treatment; acceptable motility after 3-h stress test) was used to assess spermatozoa function using in vitro assays; that is, in vitro production of embryos, penetration rates obtained 6.5 to 7.5 h post-insemination (hpi) and intracellular Ca2+ measured 8.0 to 10.0 hpi. Data were analyzed using a mixed models procedure (semen data), generalized linear mixed models (in vitro data) and nonlinear regression (intracellular Ca2+ data) of SAS 9.2 (SAS Institute Inc., Cary, NC, USA). Concentrations of serum prolactin were higher in bulls grazing NTE compared with those of the bulls grazing E+ tall fescue pastures (123.43 ± 9.23 ng mL–1 vs 97.13 ± 9.23 ng mL–1, respectively; P = 0.05). Gross motility of spermatozoa (90.95 ± 2.67% vs 85.62 ± 2.67%, NTE and E+ respectively; P = 0.17) and percent normal morphology (77.14 ± 1.93% vs 77.61 ± 1.93%, NTE and E+ respectively; P = 0.87) before cryopreservation did not differ. However, motility immediately post-thaw (58.27 ± 2.81% vs 43.84 ± 5.30%, NTE and E+, respectively; P = 0.02) and following a 3-h stress test (51.13 ± 3.88% vs 23.33 ± 3.23%, NTE and E+, respectively; P < 0.0001) were decreased for spermatozoa from bulls grazing E+ tall fescue. The percentage of PZ that cleaved was higher for oocytes fertilized with spermatozoa from bulls grazing NTE (76.30 ± 3.93%) compared with that of the bulls grazing E+ tall fescue pastures (58.92 ± 3.9%; P = 0.007; n = 1539 PZ, n = 10 replicates). Penetration rates were higher in oocytes fertilized with spermatozoa from NTE bulls (87.42 ± 1.63%) compared with that of E+ bulls (64.54 ± 3.28%; P < 0.0001; n = 2547 oocytes, n = 33 replicates). Meiotic progression of maternal chromatin was hastened in oocytes penetrated by spermatozoa from bulls grazing E+ compared to that from bulls grazing NTE tall fescue. Intracellular Ca2+ parameters (baseline, P = 0.01; amplitude, P = 0.0002; and area under the curve, P = 0.006) were reduced in PZ fertilized with spermatozoa from E+ bulls (n = 192 oocytes, n = 4 replicates). These findings indicate impaired spermatozoa function in bulls grazing E+ tall fescue pastures that extends beyond gross semen characteristics and may provide direction for future studies.

Alteration in testicular cell components following transiently induced ischaemia in prepubertal bulls

The aim of the present study was to evaluate transient testicular ischaemia (induced using elastrator bands) in Jersey calves on testicular morphology and development. Treatments (at 27 +/- 5 days of age) consisted of control (0 h banding) and banding for 2, 4 or 8 h (n = 4 in each group). After castration (at 60 +/- 5 days of age), the right testis was used for calculation of cell components per testis according to the point-counting method. Bodyweight (59.8 +/- 6.2 kg) and scrotal circumference (SC) at banding (9.1 +/- 0.2 cm) did not differ between groups. Fresh testis weight, scrotal temperature immediately before band removal and daily SC growth were decreased in ischaemic (4 and 8 h) testes compared with controls (P < 0.05). In addition, the number of Sertoli and Leydig cells was significantly reduced in the 8 h ischaemic treatment group (P < 0.05). Transiently induced ischaemia significantly decreased the number of germ cells in the 8 h ischaemic treatment group (13 +/- 5 x 10(6) cells) compared with the 0, 2 and 4 h ischaemic treatment groups (38 +/- 6, 32 +/- 6 and 33 +/- 5 x 10(6) cells, respectively; P < 0.05). These results suggest that transiently induced ischaemia for 8 h significantly decreases the number of germ, Sertoli and Leydig cells in prepubertal testis.

228 RECIPIENT PREPARATION FOR SPERMATOGONIAL STEM CELL TRANSPLANTATION: ALTERATION IN TESTICULAR CELL COMPONENTS FOLLOWING TRANSIENTLY INDUCED ISCHEMIA

Depletion of endogenous spermatogonial stem cells using busulfan (Brinster et al. 2003 Biol. Reprod. 69, 412–420) or irradiation (Izadyar et al. 2003 Reproduction 126, 765–774) have been used in preparation of recipient animals prior to transplantation; however, both techniques are not without compromises (severe bone marrow depression or specialized radiotherapy equipment required). Induced testicular ischemia in rams altered spermatic epithelium with germ cell-depleted seminiferous tubules (Markey et al. 1994 Reprod. Fertil. 101, 643–650). The objective was to evaluate testicular transiently induced ischemia (using elastrator bands) in Jersey calves on testicular morphology and development. Treatments (at 27 ± 5 days of age) consisted of control (0, n = 4), banding for periods of 2 h (2, n = 4), 4 h (4, n = 4), and 8 h (8, n = 4). After castration (age: 60 ± 5 days), the right testis of each animal was used for calculation of cell components per testis according to the point counting method. Data were analyzed using the MIXED procedure of SAS (SAS Institute, Inc., Cary, NC, USA). Body weight (59.8 ± 6.2 kg) and scrotal circumference (SC) at banding (9.1 ± 0.2 cm) did not differ between treatments. Fresh testis weight (TW), scrotal temperature immediately before banding removal (ST), and daily scrotal circumference growth (SC) were decreased (4 and 8 h) in ischemic testes compared to controls (Table 1: P < 0.05). In addition, Sertoli and Leydig cells were severely reduced in the 8-h ischemic treatment (Table 1: P < 0.05). Transiently induced ischemia significantly decreased the number of germ cells in the 8-h group, compared to the 0-, 2-, and 4-h groups (Table 1: P < 0.05). These results suggest that transiently induced ischemia significantly decreases the number of germ, Sertoli, and Leydig cells in the testis. Therefore, these present findings could be applicable for preparation of recipient animals through depletion of endogenous germ cells within the seminiferous tubules. This procedure may provide a suitable environment for transplanted donor germ cell colonization in prepubertal recipient bulls. Table 1. Parameters evaluated under transient-induced ischemia treatments

Evaluation of a modified surgical technique to correct urine pooling in cows

Various surgical techniques to correct urovagina in cows describe creating a mucosal extension from the urethral orifice to the labia; however, a fistula often forms in the mucosal extension. The objective of the present study was to determine if the incidence of fistula formation could be decreased by covering transposed submucosal tissue on the dorsal aspect of the urethral extension with a mucosal graft. Cows in both the control group (19) and the experimental group (19) received a modified McKinnon technique of urethral extension; cows in the experimental group also had a sheet of mucosa, obtained from the dorsal aspect of the vestibule, grafted to submucosa exposed during creation of the urethral extension. During histological examination of the biopsy of the graft and its recipient site (harvested 1 week after surgery), neither inosculation nor revascularization of the graft was evident in any sample. Fourteen of 19 (74%) cows in the control group and 10 of 19 (53%) cows in the experimental group developed a fistula in the extension (P=0.18). We concluded that application of a mucosal graft to the subcutaneous tissue exposed to the vestibule using the McKinnon technique of creating a urethral extension was of little or no benefit in preventing the formation of a fistula in the extension. Furthermore, during evaluation of the extensions, digital palpation alone was often insufficient for detection of a fistula.

Maternally and naturally acquired antibodies to Mannheimia haemolytica and Pasteurella multocida in beef calves

The dynamics and duration of maternally derived antibodies as well as the onset of acquired immunity against Mannheimia haemolytica and Pasteurella multocida in range-pastured beef calves were investigated. Two groups of unvaccinated cattle were used in this study. Serum antibody responses were measured by enzyme-linked immunoassay for antibodies of the IgG1, IgG2 and IgM isotypes binding M. haemolytica whole cells (WC) or leukotoxin (LKT) and P. multocida outer membrane proteins (OMPs). Comparisons of mean antibody responses to M. haemolytica LKT and WC and P. multocida OMPs were made within each group. Maternally derived antibodies against M. haemolytica and P. multocida reached lowest levels at 30-90 days after birth. Calves began production of antibodies against M. haemolytica and P. multocida between 60 and 90 days of age in both groups. Based on the results of this study, in beef herds vaccinated against M. haemolytica and/or P. multocida, it may be best to vaccinate calves around 3 months of age. In contrast, beef calves from unvaccinated herds might benefit from vaccination at 4 months of age.

Seasonal effects on estrous behavior and time of ovulation in nonlactating beef cows

Estrous behavior and time of ovulation relative to the onset of estrus were determined in mature Angus x Hereford cows (n = 17 to 21 each season) during summer, winter, and spring for 2 yr. Estrous behavior was evaluated during the first of two consecutive estrous periods, and time of ovulation was determined during the second estrus. Concentrations of progesterone were quantified in twice weekly blood samples to ensure all cows had normal estrous cycles. The HeatWatch system was used to measure the duration of estrus, number of mounts received per estrus, and duration of the longest interval between mounts received. Commencing 16 h after the onset of the second estrus, transrectal ultrasonography was performed every 4 h until the dominant follicle was no longer present on the ovary, and time of ovulation was defined as 2 h preceding the absence of the dominant follicle. There was a seasonal effect on the duration of estrus; cows were estrus longer in summer (17.6 +/- 0.8 h) than in winter (15.5 +/- 0.8 h; P = 0.07) or spring (13.9 +/- 0.9 h; P < 0.05). Cows were mounted more times per estrus (P < 0.05) in winter (59.0 +/- 5.3) than in summer (43.6 +/- 5.3) or spring (38.2 +/- 5.8). Intervals between mounts of estrous cows were longer (P < 0.05) in summer (4.1 +/- 0.4 h) than in spring or winter (2.7 +/- 0.4 h). During all seasons, cows were mounted more times (P < 0.01) between 0600 to 1200 (3.2 +/- 0.2 mounts received/h of estrus) than during other times of the day (2.1 +/- 0.2 mounts received/h of estrus). Cows ovulated 31.1 +/- 0.6 h after the onset of estrus, and time of ovulation was not influenced by season. We conclude that season influences estrous behavior of beef cows; cows are mounted more times per estrus in winter than in summer or spring. Time of ovulation relative to the onset of estrus is constant during all seasons and averages 31.1 h.

Influence of exogenous gonadotropin-releasing hormone on ovarian function in beef cows after short- and long-term nutritionally induced anovulation

The effect of pulsatile infusion of gonadotropin-releasing hormone (GnRH) on follicular function was evaluated in nutritionally induced anovulatory beef cows. After 4 (short; n = 12) or 18 wk (long; n = 12) of anovulation, cows were randomly assigned within anovulatory group to either 2 microg of GnRH treatment or saline (control; i.v.) every hour for 5 d. Ovarian structures were monitored by daily ultrasonography. Growth rate of the largest follicle (P < 0.01) and maximal size of the largest follicle during treatment were greater (P < 0.01) for GnRH vs control cows. At exsanguination after 5 d of GnRH treatment, the size of the second-largest follicle was greater (P < 0.05) in short (i.e., 4 wk) anovulatory cows than in long (i.e., 18 wk) anovulatory cows and the largest follicle tended (P < 0.10) to be larger in long vs short anovulatory cows. Short anovulatory GnRH-treated cows had more small follicles than short anovulatory control cows or long anovulatory GnRH-treated or control cows (anovulation x GnRH; P < 0.10). Follicular fluid (FFL) concentrations of estradiol (P < 0.01) and androstenedione (P < 0.05) were greater in GnRH vs control cows. Concentrations of insulin-like growth factor-I were greater (P < 0.10) in large vs small follicles in cows that were anovulatory for 4 wk, but not in cows that were anovulatory for 18 wk. The amount of insulin-like growth factor-binding protein (IGFBP)-3 in FFL was greater (P < 0.05) in 4- vs 18-wk anovulatory cows. Amounts of IGFBP-2, -4, and -5 were greater (P < 0.001) in FFL of small (< 5 mm) vs large (> or = 5 mm) follicles regardless of treatment. We conclude that pulsatile treatment with GnRH for 5 d stimulates similar growth of the largest follicles in short- and long-term anovulatory beef cows, and that the duration of anovulation is not a major factor that limits follicular growth w hen anovulatory cowsare treated with GnRH. The primary intrafollicular factors associated with increased follicular size were increased concentrations of estradiol, progesterone, and insulin-like growth factor-I,and decreased concentrations of IGFBP-2, -4, and -5. Increased duration of anovulation was associated with decreased concentrations of IGF-I and IGFBP-3 in FFL.

Effects of intraovarian infusion of insulin-like growth factor-I on ovarian follicular function in cattle

The objective of this study was to determine if increased secretion of intraovarian insulin-like growth factor-I (IGF-I), experimentally induced via minipumps, affects follicular function in cattle. Fourteen cycling Holstein cows were divided equally into two groups: Control, osmotic minipumps (containing vehicle) surgically inserted into each ovary, or IGF-I treated, osmotic minipumps as in Controls but pumping 2.0 microg of recombinant human IGF-I per hr for 7 days. All cows were synchronized with prostaglandin F(2alpha) 0.10) between Control and IGF-I-treated cows during Days 2 to 6 of treatment. IGF-I treatment increased (P<0.05) estradiol concentrations in follicular fluid of small follicles, but had no effect (P<0.10) on estradiol concentrations in follicular fluid of large follicles, or on progesterone, androstenedione, or IGF binding protein concentrations in small or large follicles. We conclude that a 7-day infusion of IGF-I directly into the stroma of the ovary altered follicular growth and follicular fluid estradiol concentrations.