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The effects of duration and concentration of plasma progesterone on the fertility of post‐partum cows treated with pregnant mare serum gonadotrophin and intravaginal progesterone
Author(s) -
MUNRO RK
Publication year - 1989
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.1751-0813.1989.tb03013.x
Subject(s) - estrous cycle , fertility , ice calving , post partum , zoology , endocrinology , medicine , plasma concentration , postpartum period , pregnancy , andrology , biology , lactation , population , environmental health , genetics
SUMMARY The effects of duration of insertion of progesterone releasing devices (PRIDs) on the concentrations of plasma progesterone (plasma P 4 ) and the relationship of these with fertility were examined respectively in ovariectomised and intact Bos taurus cattle. In experiment 1, ovariectomised cows (n = 14) were treated with PRIDs to produce high and low plasma P 4 for 7 or 14 days giving 4 treatment groups designated H7, H14, L7 or L14. Mean plasma P 4 in the H14 and L14 groups were 6.6 and 6.0 ng/ml respectively, during the first week and 5.4 and 3.8 ng/ml respectively, during the second. Mean plasma P 4 of 6.3 and 4.2 ng/ml were observed in H7 and L7. In experiment 2, suckled cows (n = 171) received the same PRID treatments as cows in experiment 1, plus either 375 or 750 iu pregnant mare serum gonadotrophin, and subsequent calving rates were recorded. These were significantly lower after L7 than the other treatments (12%⊻ 38%, P < 0.025). These results showed that fertility after oestrus was closely related to plasma P 4 observed before oestrus and indicated that treatment with progesterone for as little as 1 week can produce normal fertility providing plasma P 4 attain a critical threshold during treatment.