Effects of different feeding regimes during lay of egg-type pullets fed either high or low-protein diet during rearing

Abstract

The performance of two groups of pullets reared on either high or low-protein diets was compared under six feeding regimes from 20 to 68 weeks of age. Pullets fed the low-protein (10 per cent) diet from 4 to 20 weeks ate about 20 per cent less food during rearing, were significantly lighter at 20 weeks and were delayed in attaining maturity compared with pullets reared on the high-protein diet. In the period from 20 to 36 weeks of age, pullets reared on the high protein diet laid at a higher rate when fed a laying diet containing 17 per cent protein than with a diet containing 15 per cent protein supplemented with methionine, or 13 per cent protein supplemented with methionine and lysine to the N.R.C. (1971) levels. In contrast, pullets reared on the low-protein diet laid fewer eggs on the 17 per cent protein diet than on the other two diets during the same period. However, no significant rearing x laying interaction was observed in average rate of lay during the whole laying year. The low-protein group laid fewer eggs from 20 to 68 weeks than the other group of birds, but the difference in production was not significant when calculated from maturity. Average rate of lay was not affected by the level of protein in the laying diet, but egg size tended to increase with increasing the level of protein. Increasing the level of protein gradually with the advance in lay had no effect on performance relative to birds fed the 15 or 17 per cent protein diet throughout lay. Restricting the feed intake during lay to 94 per cent of that consumed by full-fed controls, or restricting the time of feeding to four hours daily, reduced egg production by 7 and 6 per cent respectively, regardless of the rearing treatment. Rate of mortality throughout the experiment was not affected by any of the rearing or laying treatments. The results of this experiment indicate that the requirement during lay of pullets reared on a low-protein diet is between 51 and 53 g protein and 900 and 1000 mg of methionine per 4.1 9 MJ (1000 Kcal) ME. This protein concentration should be increased to between 58 and 60 g protein per 4.19 MJ ME if the pullets were reared on conventional diets. Restricting feeding during lay by either of the methods used in this experiment is detrimental to egg production.