Dose effect of human growth hormone-releasing factor and thyrotropin-releasing factor on hormone concentrations in lactating dairy cows

Domestic Animal Endocrinology
H LapierreP Brazeau

Abstract

Two experiments were conducted to study the effects of growth hormone-releasing factor (GRF) and thyrotropin-releasing factor (TRF) administration on hormone concentrations in dairy cows. In the first trial, 12 cows were used on 5 consecutive days to determine the effect of four sc doses of GRF (0, 1.1, 3.3 and 10 micrograms.kg-1 BW) and three sc doses of TRF (0, 1.1 and 3.3 micrograms.kg-1 BW) combined in a factorial arrangement. GRF and TRF acted in synergy (P = .02) on serum growth hormone (GH) concentration even at the lowest dose tested and GH response to the two releasing factors was higher than the maximal response observed with each factor alone. TRF increased (P less than .01) prolactin (Prl), thyrotropin (TSH), triiodothyronine (T3) and thyroxine (T4) concentrations similarly at the 1.1 and 3.3 micrograms.kg-1 doses and GRF did not interact (P greater than .40) with TRF on the release of these hormones. In the second trial, the effect of GRF (3.3 micrograms.kg-1 BW, sc) and TRF (1.1 micrograms.kg-1 BW, sc) was tested at three stages (18, 72 and 210 days) of lactation on serum Prl and TSH concentrations. Eighteen cows (n = 6 per stage of lactation) were used in two replicates of a 3 X 3 latin square. The TRF and GRF-TR...Continue Reading

References

Oct 1, 1977·The Journal of Endocrinology·A B Slebodziński, A L Wallace
Apr 1, 1987·Proceedings of the Society for Experimental Biology and Medicine·W J EnrightH A Tucker
Jan 1, 1987·Reproduction, Nutrition, Development·C WrutniakB Barenton

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Citations

Oct 1, 1989·Domestic Animal Endocrinology·P PastoureauB Barenton

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