Abstract:
The productivity of heavy-, medium- and light-weight White Leghorn x Australorp pullets (216 of each strain) was established on three feed restriction regimes. The pullets were either restricted from 6 to 21 weeks of age to 80% of feed intake of pullets fed ad libitum, restricted in feeding time to 6 hours in every 48 from 6 to 21 weeks, or fed a diet containing 10% protein from day-old to 16 weeks of age. All restricted pullets ate between 19 and 37% less feed during rearing, were between 11 and 34% lighter at 21 weeks of age, and attained 50% production by 10 to 32 days later than pullets fed ad libitum. Strains differed in their responses to feed restriction as measured by mean body weight at 21 weeks, feed intake during lay, and feed per dozen eggs. Strain x rearing interactions were not observed for rate of lay, mean egg weight, total egg mass or rate of mortality. The biological responses were analyzed in economic terms using a computer simulation model. Restricting the feed intake of the heavy strain by any of these methods was more profitable, at ruling 1976 prices, than ad libitum feeding, because of the saving in feed cost and marked improvement in productivity. Performances were not improved by restriction in the light strain pullets, but feed cost was reduced by all three methods. With the medium strain, limiting the quantity of feed was more profitable than the other two methods.