Nutritional strategies with different energy and protein sources for buffaloes: digestibility and ruminal fermentation

Context The stimulus for biodiesel production has intensified due to growing environmental concerns. However, its extraction results in a high number of by-products and co-products, which, without proper disposal, can accumulate in the environment. Many of these products can be used as feed for ruminants. Aims This study evaluated the effects of replacing ground corn with crude glycerin and soybean meal with cottonseed cake and the association this had on intake, apparent digestibility, nitrogen balance, blood metabolites, and ruminal fermentation in buffalo diets. Methods Four ruminally-cannulated, castrated Murrah buffaloes (average age: 2.5 years and initial body weight: 637 ± 66 kg) were randomly assigned to a 4 × 4 Latin square design and a 2 × 2 factorial arrangement. The experimental diets consisted of different sources or combinations of energy and protein ingredients. All diets contained 70% Transvala grass hay and 30% concentrate, with the concentrate composed of the following ingredients: Diet 1 (corn + soybean meal): ground corn, soybean meal, urea, common salt, and mineral; Diet 2 (corn + cottonseed cake): ground corn, cottonseed cake, urea, common salt, and mineral; Diet 3 (crude glycerin + soybean meal): crude glycerin, soybean meal, urea, common salt, and mineral; Diet 4 (crude glycerin + cottonseed cake): crude glycerin, cottonseed cake, urea, common salt, and mineral. Key results An interaction effect between energy and protein sources was observed for neutral detergent fiber intake (P = 0.014). Buffaloes fed crude glycerin showed a higher ether extract (EE) intake (P < 0.001) and EE apparent digestibility (P = 0.011) than those fed ground corn. Higher ruminal pH (P < 0.001), propionate (P = 0.002) and butyrate (P = 0.013) concentrations were observed in buffaloes fed diets with crude glycerin compared to those fed with ground corn. Conclusions Under the conditions of this study, crude glycerin proved to be an efficient and safe alternative energy source to replace ground corn in buffalo diets, promoting favorable ruminal fermentation without impairing feed intake or nutrient digestibility. In addition, cottonseed meal used as a protein source was able to completely replace soybean meal without negative effects on ruminal, metabolic, or nitrogen balance parameters, confirming its nutritional feasibility for buffalo feeding. Implications The use of crude glycerin and cottonseed meal as alternative feed ingredients in buffalo diets represents a viable strategy to reduce feeding costs and increase the sustainability of production systems by valorizing agro-industrial co-products, with potential environmental benefits due to improved ruminal fermentation efficiency.