Evaluation of nitrogen supplements in Yankasa sheep on natural Sudan savanna vegetation during early rainy season

Abstract

An experiment was conducted to investigate growth performance and production of rumen metabolites in growing Yankasa sheep grazing the natural vegetation during the early wet season in the sudan savanna. The animals were fed supplements containing different nitrogen sources (cotton seed cake, CSC, sundried broiler litter, SDBL and urea) as follows: 1(CSC; control), 2(CSC/SDBL), 3(urea/SDBL), 4(CSC/urea) and 5(urea). The animals were randomly divided into 5 groups of 4 animals each, balanced for weight and age, then allocated to one of the supplements in a completely randomised design for 84 days. The trial was divided into 3 periods, each spanning 28 days, based on progression to the late wet season.Concentrate dry matter intake (CDMI) was much higher during the first period compared to the others. Sheep on CSC/urea (250.27g/day), CSC/SDBL (245.87g/day) and urea alone (242.49g/day) had higher CDMI compared to those on SDBL only (209.47g/day). Mean daily weight gains were higher (P<0.001) for animals fed CSC/urea (42.69g/day), followed by those on CSC/SDBL (39.51g/day) and lowest for those on SDBL (30.54g/day). Animals fed CSC (control) and urea had similar ADG values of 37.59 and 35.30g/day respectively. pH of rumen fluid increased with time for all treatments (higher at 4 hrs after feeding (AF)). At 1 hr AF, the pH was highest for CSC and SDBL supplements (6.20 and 6.30) and lowest for CSC/Urea (5.84). At 4 hrs AF, pH was highest for CSC and SDBL (6.34 and 6.29) and lowest for Urea based supplements (6.10). Concentration of rumen ammonia nitrogen (RAN) 1hr AF was significantly higher for animals fed CSC/urea (14.20mg/100ml) and urea (14.21mg/100ml), while those on SDBL recorded the least (9.86mg/100ml). However, the concentration of volatile fatty acids (VFAs) during the same period was higher for animals fed SDBL (12.70mmol/100ml) and CSC (11.84mmol/ 100ml) and lowest for those on urea (9.70mmol/100ml). In general, there was a gradual decrease in the concentrations of both RAN and VFAs of rumen fluid with time across the treatments, indicating their absorption through the rumen wall and / or utilization by rumen microbes. Animals supplemented with SDBL had the lowest feed cost of N126.62 (US$1.01) per kg gain, while those on the control supplement (CSC) the highest (N150.70) (US$1.21). It was concluded that supplements containing CSC/urea, urea and CSC/SDBL fed to Yankasa sheep grazing natural vegetation during early wet season gave results comparable to those supplemented with CSC (control) in terms of CDMI, growth performance and production of RAN. However, performance of animals fed SDBL supplement was inferior compared to the others, but feed cost per kg gain was lowest for animals on SDBL supplement.

Keywords: Supplementation, nitrogen sources, sheep, grazing, wet season, performance