Supplementation of crossbred boer goats with cottonseed meal and/or urea enhances estimated metabolizable protein intake, crude protein digestibility and nitrogen retention

Abstract

This study aimed to determine feed intake, apparent digestibility, and nitrogen retention of crossbred Boer bucks supplemented with urea or cottonseed meal (CSM)when fed tropical Rhodes (Chloris gayana) grass hay (RGH) as a basal diet. Twelve eightmonth-old bucks (23.9±1.1 kg live weight) were allocated to one of the four dietary treatments in a randomised block design. The treatments were 1) maize supplement (Control); or maize plus 2) urea supplement (M+U), 3) urea and CSM (M+UCSM); and (4) CSM (M+CSM). All bucks were held in individual metabolism crates for 21 days (11 days of adaptation and 10 days collection period) with ad libitum access to RGH and fresh drinking water in addition to the supplements. A one-way ANOVA and Duncan’s multiple range tests were used to test for differences between means at a significance level of P < 0.05. Results indicated higher feed intake, apparent digestibility of crude protein and digestible nutrient intake in goats supplemented with M+CSM and M+UCSM, but not M+U alone. Supplementation with M+CSM increased nitrogen retention by 300%. Supplementation with M+UCSM and M+CSM increased the total feed intake of Boer goats on tropical grass hay by 13 and 20%, respectively. Supplementation with M+U, M+UCSM, and M+CSM improved the apparent digestibility of crude protein by 9.7, 15.7 and 15.1%, respectively. It can be concluded that total feed intake and nutrient digestibility was increased on growing Boer goats fed RGH as a basal diet supplemented with true protein from CSM or a mixture of true protein and rumen degradable protein from urea.