Nitrogen metabolism in meatmaster sheep fed brewers grain as a supplementary source of protein
This study aimed to examine how nitrogen metabolism in sheep is affected when brewers’ grains are added to diet as a supplementary protein source. Eight Meatmaster rams (average live weight 30 ± 3.2 kg; approximately 6 months old) were randomly allocated to four iso-energetic and iso-nitrogenous diets, which contained 0%, 10%, 20%, and 30% BSG, denoted BSG0, BSG10, BSG20, and BSG30, respectively. The experiment was conducted using a 4 × 4 Latin square design in duplicate. The sheep were housed in metabolic cages for 19 days, consisting of 14 days adaptation and 5 days for data collection. During this period, feed intake, faecal and urinary outputs, and excreta were measured. Feed and excreta samples were analysed for chemical composition, including dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), ash, neutral detergent fibre (NDF), acid detergent fibre (ADF), and condensed tannins (CT) as a percentage of dry matter. These data were used to calculate nutrient intake (g/day); apparent digestibility coefficients (%) for DM, OM, CP, EE, NDF, and ADF; nitrogen metabolism parameters (nitrogen intake (NI), faecal nitrogen (FN), urinary nitrogen (UN), total nitrogen excretion (TNE), and nitrogen retention (NR) in g/day, rumen fermentation and microbial parameters (allantoin concentration (mmol/L), microbial nitrogen yield (g/day), microbial true protein (MTP, g/day), digestible organic matter in the rumen (DOMR, g/day), nitrogen utilisation efficiency (Emns, g N/kg DOMR) and the metabolizable energy (ME, MJ/day) intake. The CT content (as a percentage of dry matter) in the BSG10 diet was significantly higher (P<0.05) than in the other dietary treatments. No significant differences (P>0.05) in the intake of DM, OM, DOMI, and ME were observed. However, CP, EE, acid detergent fibre (ADF), and neutral detergent fibre (NDF) intakes varied significantly (P < 0.05) across treatments. The apparent digestibility coefficient (ADC) of EE showed no notable difference (P>0.05) among BSG0, BSG10, and BSG20. There were no significant differences (P>0.05) in the digestibility coefficients of DM, OM, NDF, ADF, and CP across all treatments. The results showed differences in NI, FN, UN, TNE, and NR(P<0.05) among the treatments. Allantoin concentrations, microbial N yield, MTP, DOMR, and Emns across all treatments were not significantly different (P>0.05). The study confirmed that brewers’ grain is an effective protein source for sheep diets, without negatively affecting rumen function or nitrogen metabolism. The crude protein content of 22.6% in the BSG makes it a suitable partial substitute for traditional protein feeds. The presence of CT in the supplemented diets appears to enhance protein retention by slowing ruminal proteolysis and reducing nitrogen loss through urine. Trends in nitrogen use and allantoin excretion indicate increased rumen microbial activity and microbial protein synthesis with the inclusion of BSG. Thus, BSG can be a suitable supplementary protein source.
Brewer's grains, Condensed tannin, Nitrogen metabolism, Nitrogen utilisation efficiency, UCTD
Networked Digital Library of Theses and Dissertations