@conference {40308,
	title = {Lactational Physiology Contract},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {51},
	year = {1991},
	month = {Jan},
	pages = {189},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Friesian cows (25 per group) were treated with excipient or  recombinantly-derived bovine somatotropin (bST, 25 mg/day) by two-  weekly injection of a controlled release formulation for 26 weeks  commencing 7 to 11 weeks after calving. Responses in fat yield were  significant during weeks 1 to 13 of treatment (spring/early summer) and  weeks 21 to 25 (autumn) but not during the intervening dry summer period  when pasture allowance was low. Ten randomly-selected cows per group  were blood sampled (tail vein, 2 hours off pasture) in weeks 5, 9, 13,  17, 21 and 25 of treatment. Treatment of cows with bST significantly  elevated plasma concentrations of immunoreactive bST (12.4 vs 18.5  ng/ml,Pooled se = 0.8 ng/ml, P<0.001) and insulin-like growth factor-1  (IGF-1) (178.5 vs 246.1 ng/ml, Pse = 7.5 ng/ml, P<0.001). Treatment x  sampling date interactions were non-significant for plasma levels of both  bST and IGF-1, reflecting parallel changes in the concentrations of  these hormones across the treatment period. It is concluded that the  inability of cows to respond to exogenous bST during periods of low  pasture availability does not reflect a diminished IGF-1 response to  bST at this time.  },
	issn = {1176-5283},
	author = {Davis SR}
}
