Calcium absorption during lactation in sheep with demineralized skeletons

Abstract

SUMMARY: Of a group of 24 pregnant Scottish Blackface sheep 12 were killed at the outset and the remainder offered,ad libitum, a poor quality hay. At the end of pregnancy seven more were killed and the remainder offered, during lactation, 3 kg/head/day of a semipurified diet of 64% dry-matter (D.M.) digestibility, and containing 18% crude protein (CP), 1·17% Ca and 0·82% P in the D.M. Milk production was determined at weekly intervals and milk samples obtained at these times for estimation of Ca and P concentrations. These sheep were killed 42 dayspost-partum. The shorn empty bodies were analysed for fat, protein, Ca and P contents.The feeding of the poor quality hay caused losses of 76, 37, 15 and 15% of the body contents of fat, protein, Ca and P, respectively, during pregnancy. Despite maintaining a moderate milk yield (1·5 kg/day) the ewes were in positive Ca and P balance during early lactation and had restored the skeleton to its initial mineral content by 42 dayspost-partum. The rate of absorption of Ca was calculated to have been at least 115 mg/ kg body weight (BW) which is double other estimates in the literature for sheep at this stage of lactation.These differences are discussed in relation to mechanisms for adaptation of Ca metabolism which have been proposed for other species.