Study on puberty and sex hormone levels in Korean native and charolais x native crossbred heifers
1983
Chung, Y.C. | Kim, C.K. (Chung Ang Univ., Seoul (Korea R.). Dept. of Animal Science)
The day at first estrus was earlier for F1 crossbred than for purebreds (326.7 plus or minus 56.1 days vs. 372.5 plus or minus 31.9 days), but difference in days at first estrus was not significant. The liveweight at first estrus was heavier (P0.01) for F1 crossbred than for purebreds (223.0 plus or minus 16.6 kg vs. 175.3 plus or minus 10.3 kg). Serum LH and FSH levels were lower than the detectable limits of the assay, which were 1.5 m IU/ml for LH and 1.2 m IU/ml for FSH at all ages of heifers except 1 crossbred heifer which showed higher level at birth and 3 months of age. Serum prolactin levels tend to be higher at 5-8 months than at any other months and the levels at 11 and 12 months of age were more variable among individuals. Serum progesterone levels were low at birth and were high at11186y and 18 months of age. After 8 months progesterone levels tended to decrease to 0.1-0.2 ng/ml. Serum estradio levels were lower than the detectable limits (10 pg/ml) of the assay at all ages up to 12 months in all heifers. It was speculated that the lowered serum LH, FSH and estradial levels during puberty in all heifers may have been caused by too long interval in serum sampling to detect episodic pea
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