Puberty attainment and reproductive performance of yearling Bos indicus-influenced heifers after two sequential treatments with progesterone.

ABSTRACT

Number of pubertal heifers at time of breeding season initiation is a primary determinant to pregnancy success during the breeding season. It was hypothesized that pre-breeding progesterone (P4) supplementation (induction) would increase the number of heifers pubertal at the time of imposing estrous synchronization treatment regimens and P/AI. Yearling, Bos indicus-influenced (n = 577) or Bos indicus (n = 174) heifers were or were not treated with P4 (CIDR and Non-CIDR, respectively) for 10 d starting on D-23 (D0 = TAI). Presence of a CL on D-33 or D-23 was considered to indicate heifers were pubertal. On D-13, there was a PGF analogue administered. On D-9, there was treatment with GnRH analogue, 6d-CIDR and PGF. There were inseminations based on estrus (D-2 to D0) or TAI on D0 for non-estrous animals. There were 5.2 % and 62.9 % purebred and crossbred heifers pubertal, respectively. Proportion of prepubertal crossbred than purebred heifers with CL on D-3 was greater as a result of imposing the pubertal induction regimen (P < 0.05 and P> 0.10, respectively). Regardless of puberty status, proportion of heifers in estrus prior to AI in the CIDR group was similar to the heifers of the Non-CIDR group for crossbreds and purebreds. Similarly, P/AI of CIDR group was similar to the Non-CIDR group for crossbreds and purebreds. In summary, imposing the pubertal induction regimen hastened attainment of puberty in yearling crossbred, but not purebred heifers. Puberty induction did not affect estrous response, neither fertility after imposing an estrous synchronization treatment regimen.