Beef production from grass and silage with autumn-born calves. 2. The effects on the performance of cattle fed on silage of barley supplementation and of previous grazing intensity

Abstract

SUMMARY1. Two experiments are described in which the consequences of variation in grazing intensity were studied during the subsequent period of winter feeding from 12 months of age to slaughter at 18 months. The cattle were loose-housed and fed on silage ad libitum, together with allowances of rolled barley. Individual organic-matter intake was measured periodically, chromic oxide being used to estimate faecal output. The digestibility of the diet was estimated with stall-fed steers.2. Groups of 12 steers were grazed at different intensities over five-month periods, so that those grazed at the higher intensity were 38 and 16 kg lighter at the start of the 1966 and 1967 winter feeding periods respectively. They did not make significant compensatory growth over the subsequent winter feeding periods, although they had a significantly higher intake of feed organic matter per 100 kg live weight than the control steers.3. With supplements of 3·63 and 1·81 kg/head per day of barley, live-weight gains were 0·77 and 0·50 kg/head per dayin the first half of the winter, but in the second half, when barley allowances were raised to 4.54 and 2·72 kg/head per day, both groups gained weight at the same rate (0·94 kg/head per day).4. The higher level of barley feeding reduced silage intake by 0·4 kg OM/kg barley OM at all stages of the winter, and the additional 306 kg of barley was associated with the production of 21 kg more carcass weight at slaughter. This higher yield of carcass was reflected in a higher weight of fat in a three-rib sample joint.