Reduced protein intake during the weaner period has variable effects on subsequent growth and carcass composition of pigs

Abstract

In total, 960 pigs (480 castrated males and 480 gilts), selected at ~28 days of age, were used to investigate the effect of restricting protein intake for a short period between 4 and 14 weeks of age. Pigs were selected over an 8-week period in groups of 120 pigs (three pens of 20 castrated males and three pens of 20 gilts per week). Pigs were given ad libitum access to commercial diets from weaning to slaughter. Pens of 20 pigs of each sex were allocated to one of six treatments: control (no restriction), restriction from 4 to 7 weeks of age, restriction from 7 to 10 weeks of age, restriction from 10 to 14 weeks of age, restriction from 4 to 10 weeks of age or a restriction from 4 to 14 weeks of age. During the period of restriction, pigs were offered ad libitum commercial diets that had been reduced in dietary lysine to digestible energy ratio by ~15%. Restricting protein intake between 7 and 10, 4 and 10 and 4 and 14 weeks of age reduced daily gain during the period of restriction. Pigs restricted from 7 to 10 weeks of age had reduced average daily feed intake (5.6%) from 7 to 10 weeks, followed by a reduction in average daily feed intake (5.5%) and improved feed efficiency (6.1%) in the subsequent period from 10 to 17 weeks of age. Daily gain for the entire experimental period was similar for all treatment groups, except those restricted from 7 to 10 weeks of age (3.9% lower than the controls), although there was no treatment effect on carcass weight. Interestingly, backfat was reduced by 10% in these animals compared with the controls, which may be economically beneficial in markets where producers are paid on backfat and carcass weight, such as those selling domestically in the Australian market. Economic benefits of reduced feed costs during both the restriction and realimentation periods were also observed when pigs were restricted from 10 to 14 weeks of age. Any economic benefits from short periods of protein restriction will vary depending on the specific market conditions and the local cost of feed protein sources.