Premium
Calving rates of Brahman and Brahman‐cross cows to fixed‐time insemination after treatment with pregnant mare serum gonadotrophin and intravaginal progesterone
Author(s) -
MUNRO R K
Publication year - 1988
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.1988.tb14924.x
Subject(s) - brahman , ice calving , insemination , zoology , estrous cycle , breed , pregnancy rate , artificial insemination , lactation , pregnancy , biology , medicine , genetics
Summary: In 2 experiments involving 151 non‐lactating and 107 lactating Brahman or Brahman‐cross cows, the effects of progesterone treatments (PRID) of 2 durations (7 ⊻ 14 days) and injections of pregnant mare serum gonadotrophin (PMSG) at 3 doses (O ⊻ 375 ⊻ 750 IU) were examined. All cows were inseminated with frozen/thawed semen 54 to 58 and 70 to 74 hours after PRID removal. Calving rates of non‐lactating cows (38%) were unaffected by breed or treatment but were higher in previously cyclic than acyclic cows (44%⊻ 19%, P < 0.025) and in cows which exhibited oestrus after treatment (52%⊻ 23%, P < 0.001). Calving rates of lactating cows were not affected by these factors but were affected by treatment; PMSG produced no significant effect after a 7‐day PRID treatment (33% overall) but increased calving rates after 14‐day PRID treatments (22%⊻ 46%⊻ 37% for 0, 375 and 750 IU respectively, P < 0.10). Comparisons of calving rates of lactating cows treated with 14‐day PRID and PMSG and artificially inseminated, and untreated naturally mated cows, showed that treatment significantly increased the proportion of cows conceiving in the first 35 days of the mating period (50%⊻ 23%, P < 0.025). The results show that treatment with PRID for 14 days and PMSG can overcome post‐partum anoestrus in lactating Brahman and Brahman‐cross cows leading to significant reductions in the calving to conception interval.