Effects of time of commencement and duration of protein restriction on egg-type pullets reared in summer and winter

Abstract

A diet containing 10 per cent protein and 11.31 MJ M.E. kg-1 was fed to six groups of eggtype pullets from either day old or four weeks for 8, 12 and 16 weeks in both summer and winter. The same diet was also fed to another group from 8 to 20 weeks of age in both seasons. During the rest of the rearing period of each treatment a diet containing 16 per cent protein was fed to 20 weeks of age. The control group was fed a diet containing 20,16 and 12 per cent protein and 12.1 5 MJ M.E. kg-1 from day old, 6 and 14 weeks of age respectively. In both seasons, feeding the restrictive diet resulted in a reduction in the cost of feeding and in body weight gain to 20 weeks of age; and a delay in maturity compared with the control without adversely affecting egg production traits or increasing food consumption during the laying phase. Pullets fed the restrictive diet from day old ate less food during rearing, matured later and tended to lay smaller eggs throughout the laying period than their counterparts which were restricted from four to eight weeks of age in both experiments. Food consumption was not affected by the duration of restriction in either rearing season. However, feeding costs and body weight of pullets at the end of both rearing seasons were reduced progressively by increasing the duration of restriction. Rate of mortality was not affected by the rearing treatments when the birds were reared in summer, whereas in winter pullets restricted from day old for 12 to 16 weeks had the higher rate of mortality. Mortality during laying was not affected by the rearing treatments in either season. The results of both experiments suggest that for maximum return the optimum age for feeding the low protein diet is from 4 to 20 weeks of age in either season.

Modified Step-Up Protein Feeding Regimens for Egg-Type Chickens

“…Reduced feed consumption during the juvenile period resulting from the MSUPRP treatments agrees with previous reports (Abu-Serewa, 1977;Leeson and Summers, 1979;1982;Doran et al, 1983;Robinson, 1983). Although the control birds (Treatment 4) consumed significantly more feed per bird than the MSUPRP treatment birds, they ingested the least protein per bird.…”

“…Significantly reduced average egg weight was reported by Leeson and Summers (1979) and Doran et al (1983) for white egg stocks and Maurice et al (1982) for brown egg stocks when subjected to step-up feeding programs. The current study, along with those of Abu-Serewa (1977) and Robinson (1983), resulted in comparable average egg weights for step-up and conventionally reared pullets. Commercial egg size may be of more economic importance than average egg weight, thus, comparisons were made between percentages of each size.…”

“…Thus, this MSUPRP treatment produced a body weight restriction at 20 weeks of age, although the degree of restriction was not as severe as the step-up program used by Leeson and Summers (1979). Other step-up programs have also produced pullets with significantly lighter 20-week body weights than those reared on conventional programs (Abu-Serewa, 1977;Leeson and Summers, 1980;Doran et al, 1983;Robinson, 1983). Body weights of brown egg stocks, however, did not differ at 20 weeks of age as reported by Maurice et al (1982).…”

“…Reports that step-up feeding programs had no influence on livability during the growing period have also been made by Abu-Serewa (1977), Summers (1979, 1982), and Robinson (1983). Doran et al (1983), however, reported a decreased livability during the rearing period from step-up protein feeding.…”

“…Reports by Abu-Serewa (1977), Summers (1979, 1982), Maurice et al (1982), and Robinson (1983) indicated that livability during the laying year was not affected by step-up rearing, but Doran et al (1983) reported a 2.65% (P<.05) significantly higher livability for step-up reared birds. Although treatments did not differ significantly, the percentages of survival for the laying year in our study were 80.7, 78.5, 72.4, and 70.8 for Treatments 1, 2, 3, and 4, respectively.…”