Vol. 43, No. 4, 1999
THE INFLUENCE OF BODY CONDITION AND GnRH INJECTION ON THE FIRST POSTPARTUM OVULATION IN DAIRY COWS
Hajurka, J., Macák, V., Valocký, I.
University of Veterinary Medicine
Komenskeho 73
041 81 Kosice
The Slovak Republic
Summary
We observed the time to first postpartum ovulation of dairy cows in correlation with their nutritional status, as well as evaluated the influence of the injection of the gonadotrophin releasing hormone agonist (GnRH) on the first postpartum ovulation under defined nutritional conditions.
In the first week postpartum, 171 cows were assessed on a 5-point scale of body condition scores (BCS). Between days 13 and 15 postpartum 200 µg GnRH agonist (Ferring-Léčiva, Prague) was injected (i.m.) to randomly selected 120 cows. The ovarian response to the treatment was assessed retrospectively according to the rectal examination of ovaries at two-to-three day intervals (Monday, Wednesday, Friday) and radioimmunoassay of progesteron (RIA-test-PROG vet. HUMA-LAB, Košice) in parallel samples of milk. We did not found significant correlation between the body condition and the induction of the first postpartum ovulation. Fifty-one cows served as an untreated group. The first ovulation after parturition in the untreated group was determined in the same way as that in the treated group. A gradual dependence of the first postpartum ovulation on the body condition was observed. The emaciated cows (BCS-1) ovulated on day 63.8 ± 10.7 on average. In the cows with body condition scores 2, 2.5, 3, and 3.5 resp. the first ovulation was recorded on days 38.8 ± 9.1, 24.6 ± 13.2, 17.1 ± 5.8 and 15.7 ± 4.9, respectively (P < 0.001). The untreated cows (n = 51) had BCS 2.4 ± 0.7, and the spontaneous ovulation occurred on day 28.3 ± 17.2.
The interval from parturition to the first spontaneous ovulation was significantly influenced by the body condition, but no correlation was found between the body condition status and induction of the first ovulation by a single treatment with the GnRH agonist.
Key words: dairy cows; body condition status; the first postpartum ovulation; GnRH agonist; induction of ovulation
References
Folia Veterinaria / 1999