title: Reproductive performance and reconception of Nellore cows according to their pure- or cross-bred calves.
abstract: The objective of the present research was to evaluate the effect of a calf's genetic group on the productive and reproductive efficiency of its Nellore dam. Fixed-time artificial insemination was applied to 800 cows using semen extracted from Nellore, Simmental and Angus Red bulls. Four hundred eleven cows calved, producing 119 Nellore, 103 ½Simmental-½Nellore and 189 ½Nellore-½Angus Red calves. The second mating period, which paired Nellore cows with Simmental bulls, was initiated 10 days after parturitions began and lasted for 5 months. Based on the two successive parturitions, the cumulative parturition rate for calving periods of 3, 4 and 5 months was calculated. Although no significant difference was observed for birth weight among the genetic groups, cross-bred calves weighed, on average, 10% more than did pure-bred calves at the age of 205 days. Nellore dams experienced a gestation period that was 7 days longer than did the cross-bred dams, and the former showed a higher parturition rate at 90 and 120 days of the calving season, but not at 150 days (calving rates of 80.6, 76.4 and 76.2% for mothers of Nellore, ½Nellore-½Angus Red and ½Nellore-½Simmental, respectively, p > 0.05). At 90 and 120 days, Nellore dams produced more kg of calf per mated dam. In conclusion, in a short breeding season, Nellore dams nursing pure-bred Nellore calves were found to have a higher biological efficiency compared with Nellore dams nursing cross-bred calves.
authors.affiliation: Department of Animal Production, UNESP, Botucatu, SP, Brazil.
authors.forename: W B
authors.initials: WB
authors.lastname: Rodrigues
authors.forename: F S
authors.initials: FS
authors.lastname: Wechsler
authors.forename: E
authors.initials: E
authors.lastname: Nogueira
mesh_terms: D000818:Animals; D001724:Birth Weight; D002417:Cattle / Q000235:genetics* / Q000502:physiology*; D003433:Crosses, Genetic; D005260:Female; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate