Effects of alternative energy and protein sources on performance, carcass characteristics, and meat quality of feedlot lambs

Abstract

The aim of this study was to evaluate the effects of replacing ground corn with crude glycerin and soybean meal by cottonseed cake, in association or not, on digestibility and intake of dietary nutrients, performance, carcass characteristics and meat quality of feedlot lambs. Thirty-two non-castrated crossbred 1/2 Santa Inês x 1/2 Dorper lambs, with an average body weight of 18.52 ± 3.24 kg (mean ± standard deviation) and with 3 months of age were distributed in a randomized complete block design, into four treatments and eight replicates per treatment, in a 2 × 2 factorial scheme. Four experimental diets were tested with different sources or combinations of energy and protein ingredients, respectively, in the concentrate: 1) ground corn + soybean meal; 2) ground corn and cottonseed cake; 3) crude glycerin and soybean meal; 4) crude glycerin and cottonseed cake. There was an interaction between the energy and protein sources in ether extract intake and total digestible nutrients digestibility (P < 0.01). There was an interaction between the energy and protein sources in the total weight gain (P = 0.03), hot (P = 0.03) and cold (P = 0.04) carcass weights, and shear force (P = 0.29). The inclusion of crude glycerin decreased (P = 0.01) the dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and non-fibrous carbohydrates (NFC) intakes, and the apparent digestibilitis of OM, NDF, and NFC (P < 0.05). Crude glycerin decreased the amount of retained nitrogen (P = 0.02), lower final weight (P < 0.01), average daily gain and cold carcass yield. An increase ocurred in the NDF intake (P < 0.05) when lambs were fed diet with cottonseed cake and a decrease (P < 0.01) in the digestibilities of DM, OM, CP and NDF. The replacement of 100% of ground corn by crude glycerin, with low purity, is not recommended in diets for feedlot lambs, because it decreases animal performance. In contrast, the total replacement of soybean meal by cottonseed cake can be used in diet for lambs, without causing damage to the performance and meat quality.