The use of follicle-stimulating hormone (FSH-P) for the induction of superovulation in cattle]

The clinical effectiveness of FSH-P for initiating superovulation in cattle was examined in 948 animals of the breed Deutsche Schwarzbunte and Deutsche Rotbunte of RPN Verden during 1988 and 1989. In the group of the FSH-P treated animals the number of transferable embryos was 4.4 +/- 4 per animal. The 25% percentile was 1 and the 75% percentile was 7 transferable embryos per donor. In 88 animals no embryos were found. In animals with a large number of embryos there was a changed quotient between transferable embryos and non transferable embryos per animal. A seasonal dependence in the number of transferable embryos was not found. Repeated treatment with FSH-P seemed to have no influence on the number of transferable embryos per animal. In the dose range between 6.6-9.4 mg FSH-P no differences in the number of transferable embryos per animal were found.     

Studies on the suitability of alpha-hybrid interferon application in cattle

Twelve cattle with body wts ranging from 100 to 250 kg were treated using various doses and routes for four days with an E. coli derived alpha-hybrid interferon. The lowest parenteral doses (10⁴ units per kg body wt) and the orally administered interferon did not lead to any disturbances, whereas the higher dosages led to marked changes in body temperature, pulse and respiration rates. Animals with the highest dose (10⁸ units per kg body wt) became extremely distressed. The blood picture showed distinct changes, with very low leukocyte counts during treatment, which took weeks to recover. It is suggested that the dosages that did not lead to clinical symptoms are best suited for prophylactic or therapeutic purposes.     

Clinical evaluation of growth hormone secretion in cattle using insulin tolerance test

Growth hormone secretion was evaluated in cattle. Clinically healthy bovine growth hormone (bGH) concentrations were 10.7 +/- 1.6 ng/ml in Holstein and 7.8 +/- 3.9 ng/ml in Japanese black cattle. The bGH concentration alternated at three-hour intervals, and tended to be higher at midnight and lower in the morning and before feeding. Insulin tolerance test (ITT) at an insulin dosage of 0.25 U/kg showed a significant increase of bGH concentration to 331 +/- 153% at 60 to 90 min after injection. In ITT applied to five under-growth calves of Japanese black cattle, the basal bGH concentrations were lower and peak values after insulin injection were shown to be significantly low. The ITT is useful for the clinical examination of bGH secretion in cattle.     

Methodology for the study of the hypothalamic-pituitary hormone secretion in cattle

Studies on the neuroregulatory mechanisms on the secretion of anterior pituitary (AP) hormones in domestic animals are important because nearly all complex physiological and metabolic processes are regulated by the AP hormones. To examine them, this article considers in vivo approaches such as the techniques of intrahypothalamic injection, intracerebroventricular injection, push-pull perfusion, and microdialysis, which have been employed in our own research group for the study in cattle. Also, in vitro approaches such as bovine AP cell culture and the AP explants superfusion system are described. This article clarifies the potential of neuroendocrine study techniques in cattle.     

Influence of premature induction of a luteinizing hormone surge with gonadotropin-releasing hormone on ovulation, luteal function, and fertility in cattle

We tested the hypothesis that luteal function and fertility would be reduced in cattle induced to ovulate prematurely compared with those ovulating spontaneously. Estrus was synchronized in 56 beef cows (24 that were nonlactating and 32 that were nursing calves). At 6.4 +/- 0.1 d after estrus, all follicles > or = 5 mm were aspirated (day of aspiration = d 0) with a 17-gauge needle using the ultrasound-guided transvaginal approach. On d 1.5 and 2, cows were administered 2 luteolytic doses of PGF2alpha. Ovarian structures were monitored by transrectal ultrasonography from d -2 to 12, or ovulation. Emergence of a new follicular wave occurred on d 1.7 +/- 0.1. When the largest follicle of the newly emerged wave was 10 mm in diameter (d 4.8 +/- 0.1), cows were assigned on an alternating basis to receive 100 microg of GnRH (GnRH-10; n = 29) to induce ovulation or, upon detection of spontaneous estrus, to the spontaneous (SPON) treatment (n = 24). Cows were bred by AI at 12 h after GnRH (GnRH-10) or 12 h after the onset of estrus (SPON) as detected using an electronic surveillance system. Blood samples were collected every other day beginning 2 d after ovulation until pregnancy diagnosis 30 d after AI. Ovulation and AI occurred in 29/29 cows in the GnRH-10 and in 24/24 cows in the SPON treatment. Ovulation occurred later (P < 0.05) in the SPON (d 7.7 +/- 0.1) than GnRH-10 (d 6.8 +/- 0.1) treatment. Double ovulations were detected in 47% of cows, resulting in 1.5 +/- 0.1 ovulations per cow. Diameters of the ovulatory and the second ovulatory (in cows with 2 ovulations) follicles were greater (P < 0.05) in the SPON (12.0 +/- 0.3 mm and 10.5 +/- 0.4 mm, respectively) than in the GnRH-10 (10.7 +/- 0.1 mm and 9.2 +/- 0.3 mm) treatment. Cross-sectional areas of luteal tissue and plasma concentrations of progesterone during the midluteal phase were greater (P < 0.05) in the SPON (3.62 +/- 0.2 cm2 and 6.4 +/- 0.3 ng/mL) than in the GnRH-10 (3.0 +/- 0.2 cm2 and 5.4 +/- 0.2 ng/mL) treatment. The conception rate to AI in the SPON (100%) treatment was greater (P < 0.05) than in the GnRH-10 (76%) treatment. The animal model used in this study resulted in unusually high conception rates and double ovulations. In conclusion, premature induction of the LH surge reduced the diameter of ovulatory follicle(s), the luteal function, and the conception rate to AI.     

Clinical examination of cattle for BSE in a cattle facility and slaughterhouse

Detection of a case of BSE in slaughtered cattle causes considerable expenses. It seems therefore desirable to screen cattle before slaughtering and exclude suspect animals from slaughter. The object of this study was to determine the practicability of such screening under realistic conditions in a large slaughterhouse and to evaluate the specificity of the tests proposed by BRAUN et al. (1997). 949 cattle over 24 months old were examined in the Munich slaughterhouse. Spontaneous behaviour and the reaction to tactile, acoustic, and optical stimuli only could be tested. The evaluation of locomotion was not possible without interference with the routine processing of cattle before slaughter. The examination took about three minutes per animal. The results were evaluated using a modification of the scheme of BRAUN et al. (1997). The specificity of the classification "BSE very likely" was 97.8%. If all animals that exhibit any signs suggestive of BSE were to be excluded, the specificity would drop to 63.7%. This pre-slaughter clinical screening is not useful.     

Vaccination studies for the control of campylobacteriosis in Jamaican cattle

Following the first diagnosis of campylobacteriosis in Jamaican cattle a field study was undertaken to determine the pathogenicity of Campylobacter fetus subspecies venerealis Jam (Jamaican strain) and to evaluate the effectiveness of vaccination in controlling the disease. A total of 46 nonpregnant yearling heifers and four two-year-old bulls were used in two separate experiments. The results showed that C fetus subspecies venerealis Jam readily colonised the reproductive tract of susceptible heifers and persisted in some animals (68 per cent of unvaccinated and 33 per cent of vaccinated animals) for the duration of the experiment. Pregnancy was confirmed in 13 of 18 (72 per cent) culture-negative heifers but in only eight of 28 (29 per cent) of the heifers with two or more positive cultures. Vaccination appeared to be curative because 44 per cent of vaccinated heifers were cleared of infection whereas 85 per cent of unvaccinated, inoculated heifers remained infected for at least 17 weeks. Vaccination improved the fertility level of the infected heifers threefold. Infection was not established in vaccinated bulls used for breeding infected heifers.