Ovulatory follicle dysfunction in lactating dairy cows after treatment with Folltropin-V at the onset of luteolysis.

The objective was to examine growth of the ovulatory follicle after FSH (Folltropin-V; Bioniche Animal Health, Belleville, Ontario, Canada) was given at the onset of induced luteolysis during a synchronization of ovulation protocol. Using GnRH or hCG for inducing ovulation enabled assessing ovulatory follicle responsiveness to an endogenous versus exogenous surge of LH activity. At 8 to 10 days after estrus (synchronized estrus = Day 0), lactating dairy cows received an Eazi-Breed CIDR (Pfizer Animal Health) plus 100 µg GnRH. After 7 days, controlled internal drug release devices (CIDRs) were removed, cows were given 500 µg cloprostenol, and then randomly allocated to receive 80 mg Folltropin-V (FSH; N = 19) or 4 mL sterile saline (SAL; N = 16). After 49 hours, FSH and SAL cows were randomly allocated to receive 100 µg GnRH or 3000 IU hCG. Five cows ovulated 30 to 42 hours (38.4 ± 1.2 hours) after FSH treatment. In the remaining FSH (N = 14) or SAL (N = 16) cows, ovulatory follicle size was similar at CIDR removal (14.5 ± 0.6 and 14.7 ± 0.6 mm, respectively; P = 0.85) and when GnRH/hCG was given (16.6 ± 0.6 and 17.7 ± 0.6 mm, respectively; P = 0.23). Estradiol-17ß concentrations were lower in FSH cows at 36 and 49 hours after CIDR removal (FSH by time interaction, P < 0.005). After GnRH or hCG treatment, four FSH cows failed to ovulate. In cows exhibiting ovulation, the last recorded size of the ovulatory follicle was not influenced by FSH (18.1 ± 0.9 and 17.5 ± 0.6 mm for FSH and SAL, respectively; P = 0.59) or hormonal induction approach (18.4 ± 0.9 and 17.2 ± 0.7 mm for GnRH and hCG, respectively; P = 0.29). The interval from onset of luteolysis to ovulation and pharmaceutical induction to ovulation was shorter in FSH cows given GnRH (FSH by pharmaceutical inducer [GnRH vs. hCG] interaction; P = 0.01). Cows receiving GnRH had an LH surge; hCG-treated cows did not. Maximum LH concentrations were greater (P < 0.04) in SAL versus FSH cows after GnRH treatment (10.9 ± 1.2 vs. 6.7 ± 1.4 ng/mL, respectively). In three FSH cows failing to ovulate after GnRH treatment, the maximum LH concentration was <4 ng/mL. When analyzed from GnRH treatment, average time to LH maximum concentration was similar (P = 0.50) to values obtained in cows receiving FSH and GnRH and SAL and GnRH (1.7 ± 0.2 vs. 1.9 ± 0.1 hours, respectively). Interval to maximum hCG concentrations was shorter (P = 0.02) for cows receiving SAL versus FSH (8.0 ± 0.8 and 10.0 ± 0.8 hours for SAL and FSH, respectively). Ovulatory dysfunction of this magnitude highlighted the lack of suitability of Folltropin-V at a dose of 80 mg at the time of induction of luteolysis in fixed timed AI protocols.

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.

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.

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.