Soybean meal or cotton by-products associated with urea as source of nitrogen in the diet of lactating goats

Abstract

The objective of this study was to evaluate the influence of sources of nitrogen on the intake and digestibility of nutrients and production and chemical composition of goat milk. Soybean meal (SBM), soybean meal + urea (SBM+U), cottonseed meal + urea (CM+U), cottonseed cake + urea (CC+U) and whole cottonseed + urea (WC+U) were used, representing the different sources of nitrogen in the diet. Ten crossbred goats were used (Alpine + Saanen), weighing on average 47.90±1.94 kg of body weight at 30 days of lactation, distributed in a double Latin square (5 × 5) with five treatments and five periods. There was influence of the different sources of nitrogen on the intakes of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and non-fiber carbohydrates (NFC) of animals, with the lowest values found in most of the variables studied for animals that received CC+U and WC+U. There was an effect of diets on the DM, OM, CP and NFC digestibility coefficients. The diet with sole addition of SBM presented the best result regarding the amount of milk produced, followed by animals fed SBM+U and CM+U and values of 2.05 kg/day; 1.92 kg/day; 1.73 kg/day; 1.47 kg/day; and 1.24 kg/day of milk for diets with SBM, SBM+U, CM+U, CC+U and WC+U, respectively. Milk composition was also changed, and the diet with WC+U showed higher percentages: 0.1208 and 0.0041 percent, for total solids and fat, respectively. There was no difference in nitrogen balance between treatments. The use of SBM+U and CM+U did not compromise the milk performance and characteristics, but the use of CC+U and WC+U is indicated in periods of low milk production. © 2013 Sociedade Brasileira de Zootecnia.