|Yen, Jong Tseng|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/1999
Publication Date: N/A
Interpretive Summary: The development and introduction of superior strains of pigs and the increased emphasis on the need to produce a lean carcass has led pork producers to re-evaluate their feeding programs frequently to optimize lean production. In recent years, interest in feeding finishing pigs high-protein diets to increase leanness has risen. However, little attention has been given to the effects of protein concentrations in excess of the requirement on growth performance and metabolism in pigs. The results of the present study showed that increasing dietary protein from 13 to 25% improved carcass traits but reduced feed intake, weight gain and protein accretion in finishing barrows and gilts. High-protein diets also increased liver, kidney and pancreas weights as well as urea-cycle enzymes and plasma urea concentrations. Therefore, protein concentrations that exceed the requirements of finishing pigs not only are wasted through elevated synthesis and excretion of urea, they also raise maintenance energy requirement of the liver and thus, lower the portion of absorbed energy available for body growth.
Technical Abstract: Two experiments were conducted to evaluate the effect of excess protein on growth performance, carcass characteristics, organ weights, plasma urea concentration, and liver arginase activity of finishing barrows and gilts. In Experiment 1, feed intake decreased with increasing protein concentration, and the reduction was greater in gilts than in barrows. There was a trend toward a linear negative effect of dietary protein on ADG and also a quadratic effect of protein on protein accretion. Fat accretion decreased linearly as protein level increased. Increased protein concentrations resulted in increased liver, kidney, and pancreas weights. Plasma urea concentration increased with each protein concentration. In Experiment 2, average daily feed intake was greater in barrows than in gilts. Average daily gain was reduced by 18% in gilts when dietary protein was increased from 16 to 25% but was only reduced 3% in barrows. Barrows had lighter liver weights, greater arginase activities, and greater plasma urea concentration than did gilts. Increasing dietary protein concentration from 16 to 25% resulted in increased liver weight, arginase activity, and plasma urea concentration. These data suggest that gilts are more sensitive than barrows to excessive intakes of protein. The more negative effects in gilts may be related to liver metabolic capacity and activity of urea cycle enzymes. The increases in organ weights indicate that maintenance energy requirements may be increased as dietary protein concentration is increased.