Feeding Agroindustrial Byproducts to Light Lambs: Influence on Growth Performance, Diet Digestibility, Nitrogen Balance, Ruminal Fermentation, and Plasma Metabolites

SIMPLE SUMMARY: Feeding agroindustrial byproducts to ruminants can have multiple benefits, such as lowering feeding costs, reducing competition with human food, decreasing environmental impact associated with byproducts disposal, and improving the quality of animal products. In order to use these byproducts in practical feeding, their effects on animal performance and health should be assessed. In this study, we evaluated the effect of replacing 44% of conventional feeds in a high-cereal concentrate for light lambs with three byproducts: Corn distiller’s dried grains with solubles (18%), dried citrus pulp (18%), and exhausted olive cake (8%), all of which are highly produced in the Mediterranean area. We observed that the inclusion of these byproducts did not affect feed intake, growth performance, ruminal fermentation (with exception of NH(3)-N concentrations), or plasma metabolites in growing lambs. Compared with the high-cereal concentrate, feeding the concentrate including the byproducts resulted in a reduction of potentially human-edible ingredients from 64.4% to 38.7%. In conclusion, 44% of cereal grains and protein feeds in the concentrate for light lambs can be replaced with a mixture of corn distiller’s dried grains with solubles, dried citrus pulp, and exhausted olive cake without negatively affecting growing performance and animal health. ABSTRACT: The objective of this study was to evaluate the effect of replacing cereals and protein concentrates in a high-cereal concentrate (control) for light lambs with corn distiller’s dried grains with solubles (DDGS; 18%), dried citrus pulp (DCP; 18%), and exhausted olive cake (EOC; 8%) in a byproduct (BYP) concentrate on growth performance, digestibility, ruminal fermentation, and plasma metabolites. Two homogeneous groups of Lacaune lambs (13.8 kg ± 0.25 kg) were fed one of each concentrates and barley straw ad libitum until reaching about 26 kg body weight. There were no differences between groups on feed intake, average daily gain, or feed conversion ratio, but the control diet had greater (p < 0.001) dry matter digestibility. Diet had no effect on post-mortem ruminal pH and total volatile fatty acid concentrations and profile, but NH(3)-N concentrations were lower (p = 0.003) for the BYP-fed group compared with the control one. However, plasma concentrations of amino acids, total proteins, urea, and hepatic enzymes were not affected by the diet. In conclusion, 44% of feed ingredients in the concentrate for light lambs can be replaced with a mixture of corn DDGS, DCP, and EOC without negatively affecting growing performance and animal health.