Effect of Weaning Weight and Dietary Protein Level on the Performance of Pigs Weaned at 7 days

Abstract

The effects of initial weight (IW) and of dietary protein level (21, 23, 25, 27, 29 and 31%) on the performance of piglets weaned at 7 d were studied in two trials. Each trial involved 48 Yorkshire piglets and was divided into three 5-d periods. Increases in the crude protein (CP) content of the diet caused linear (P<.05) increases in average daily gains (ADG) and in gains adjusted to equal feed intake by covariance (AADG), but had no effect on average daily feed consumption (ADF). Initially heavier pigs ate more feed (P<.05) and gained more weight (P<.05) than those that were initially lighter in weight. However, more efficient (P<.05) gains due to a higher IW were observed only in period 2. Surface response techniques were used to study the relationships among ADG, IW and CP. The equation ADG = 4.3 × IW × CP−.018 × IW2 × CP2−6.5 described these relationships satisfactorily (r2 = .52; SE = 29.9; P<.01). According to this equation, ADG increased with increases in IW or CP but only up to a certain level beyond which the gains became smaller. At each IW there was a CP content at which gains would become maximal and vice versa. The combination of IW and CP at which maximum gains would be obtained, however, was outside the range of values investigated. Increases in dietary protein level caused linear increases in plasma urea N concentration (P<.01) and in CP digestibility (P<.05).