2000, Number 3
Vet Mex 2000; 31 (3)
Comparison of the conception rate and luteal function in first service cows, repeat-breeder cows, and Holstein heifers
Morales RS, Hernández CJ, Rodríguez TG, Peña FR
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ABSTRACTThe present study compared the conception rate between mature Holstein cattle and Holstein heifers, and the relationship between fertility and luteal function evaluated by progesterone profiles during 15 days after insemination. The first part of the study evaluated the conception rate in 4 102 first service mature cows, 1 818 repeat breeders and 900 first service heifers. There were no differences (P › 0.05) in the conception rate of mature Holstein first service cattle (34.4%) and repeat breeders (34.6%). However, conception rate in Holstein heifers (59%) differed significantly from that of the former groups (P‹0.05). In the second part of the study, the progesterone profile from day of insemination (day 0) to day 15 postinsemination, and the area under the progesterone curve were compared by ANOVA in first service cows (n = 10), repeat breeders (n = 17) and heifers (n = 10). Progesterone concentrations during the 15 days postinsemination were similar (P › 0.05) among the three groups. The area under the progesterone curve was not different (P›0.05) between first service cows (50.1±4.2 ng/ml), repeat breeders (48.2±3.2 ng/ml), and heifers (49.6±4.2 ng/ml). There were no differences in progesterone profiles between the animals that got pregnant and those that remained open in each group. This study shows that the conception rate of first service Holstein cows and repeat breeder cows does not differ. Secondly, the difference regarding fertility seen between mature cows (first service and repeat breeders) and heifers, could not be explained by differences in luteal function as the concentrations of progesterone did not differ between groups.