Factors limiting the intake of feed by sheep. 13. Voluntary roughage consumption in late pregnancy and early lactation in relation to protein nutrition

Abstract

Studies were made of (i) the effect of protein nutrition on voluntary roughage consumption in late pregnancy and early lactation, and (ii) the effect of pregnancy on the voluntary consumption of a high protein ground mixture of roughages and concentrates. The three roughage diets used were based on wheaten hay, a mixture of wheaten and lucerne hays and wheaten straw. In late pregnancy, voluntary consumption varied with roughage quality being highest with the wheaten hay diet and lowest with the straw diet. The provision of protein supplements decreased the consumption of wheaten hay diet (-6%), increased the consumption of mixed hay diet during days 31-18 pre-partum (+ 5%), but not at other times, and increased straw diet consumption (+ 17%). The intake of the high protein ground diet was not affected by pregnancy until about day 21 pre-partum, after which it declined at c. 0.9% per day. In early lactation, protein supplement decreased the consumption of wheaten hay diet (-6%), but had no effect on the consumption of mixed hay diet. It was concluded that (i) roughages of comparatively low protein value may provide adequate protein for the expression of maximum voluntary roughage consumption in late pregnancy and early lactation, (ii) feed intake regulation in late pregnancy could not be based solely on physical limitations, on energy metabolism considerations or on hormonal responses, and (iii) changes in the metabolism of maternal adipose tissue in late pregnancy could play a role in the intake regulation.