Does macauba cake alter nutrient digestibility and microorganism population in the rumen of sheep?

Twenty Santa Inês male sheep were used in a randomized block design to evaluate the effects of different levels of macauba cake (MC) on nutrient digestibility and the population of microorganism in the rumen. The animals were divided into four groups according to MC levels (0, 10, 20, and 30% of DM) and initial body weight ranging from 32.75 to 52.17 kg. Diets were isonitrogenous and formulated to attend metabolizable energy requirements, and feed intake was regulated with 10% allowance for leftovers. Each experimental period lasted 20 days, with the final 5 days reserved for sample collection. Macauba cake inclusion did not affect the dry matter, organic matter, or crude protein intake but increased the ether extract, neutral detergent fiber, and acid detergent fiber intake, mainly because of changes in the concentrations of these components in diets with a higher level of MC. With MC inclusion, a linear decreasing effect was observed for the dry matter and organic matter digestibility, and a quadratic effect with a maximum point of 21.5% was observed for the acid detergent fiber digestibility. A relative reduction of 73% in anaerobic fungal populations was observed with the lowest level of MC inclusion, and a relative increase of 162% in methanogenic populations was observed with the highest level of MC inclusion. The increasing level of macauba cake up to 30% of the diet of lambs reduced the dry matter digestibility and reduced anaerobic fungi but increased methanogenic population.