Ovarian response to gonadotropin-releasing hormone in postpartum dairy cows.

Laparotomies were performed on 17 lactating dairy cows, milked twice daily, 12 or 13 days after parturition to observe gross ovarian structures. Five cows were randomly given an IM injection of saline solution and 12 cows were given 100 micrograms of gonadotropin releasing hormone (GnRH). A 2nd laparotomy was performed 3 days later to observe changes in ovarian structures. In addition, the genital tract was palpated per rectum 5 to 8 days after the 2nd laparotomy, and blood samples for hormonal analysis were obtained prior to each laparotomy and palpation per rectum. Eight of 12 cows given GnRH and 2 of 5 cows given saline solution had developing corpora lutea with prominent ovulation papilla at the time of the 2nd laparotomy. Luteinized follicles were not observed. In GnRH-treated cows, 7 of 7 cows with follicles greater than or equal to 15 mm ovulated after GnRH treatment compared (P less than 0.01) with 1 of 5 cows with follicles less than or equal to 10 mm. Increase in plasma progesterone was not observed in GnRH-treated cows not ovulating. Thus, GnRH induced ovulation in postpartum dairy cows that had large follicles at the time of GnRH treatment.

Comparison of a leukocyte esterase test with endometrial cytology for diagnosis of subclinical endometritis in postpartum dairy cows.

The objective was to compare a leukocyte esterase (LE) test with endometrial cytology (EC) for diagnosis of subclinical endometritis in dairy cows. The relationship between subsequent fertility and the uterine (Ut) and cervical (Cx) leukocyte esterase activity was determined by the odds of pregnancy by 90 days in milk (DIM). Holstein cows (N = 218) without clinical endometritis and between 21 and 47 DIM from five commercial dairy herds were sampled for uterine and cervical leukocyte esterase activity and EC by cytobrush. To test the effect of time, cows were grouped into early (21-31 DIM) and late (32-47 DIM) animals. There was a slight agreement between UtLE and CxLE (weighted κ = 0.37). The percentage of neutrophils was correlated with esterase score either from the uterus (UtLE; P = 0.0001) or cervix (CxLE; P = 0.002). The percentage of neutrophils on EC (P < 0.001), the UtLE score (P < 0.0001), and the CxLE (P = 0.0009) diminished as DIM increased. Neither CxLE nor UtLE were statistically associated with pregnancy at 90 DIM. However, between 32 and 47 DIM, the percentage of neutrophils on EC and odds of pregnancy at 90 DIM were associated (P = 0.04). For the same interval, based on receiver/response operating characteristics analysis, the optimal cutoff was >6.7% neutrophils to classify cows with subclinical endometritis. In conclusion, uterine LE activity was correlated with percentage of neutrophils as determined by EC, but not with odds of pregnancy. Subclinical endometritis (>6.70% neutrophils) diagnosed by EC between 32 and 47 DIM was associated with reduced odds of pregnancy.