Effect of dietary protein and rumen degradable organic matter on milk production and efficiency in heat-stressed goats

Abstract Four Israeli mix-breed Saanen dairy goats were used in a 2×2 factorial design to evaluate the effect of the level of dietary crude protein (CP) and ruminally degradable OM (RDOM) concentration on the production, composition and efficiency of milk production under hot ambient conditions. Daily ration comprised of 30% hay and 70% concentrates was divided into 12 equal meals. Treatment factors were 18% (HCP) or 15% (LCP) of CP in the diet DM, and 56% (HRDOM) or 50% (LRDOM) of RDOM. Goats were housed in metabolic crates in air-conditioned room. Air temperature ranged between 25 °C and 36 °C, and the thermal humidity index (THI) between 74 and 90 units. Daily amplitude of goat's body temperature was 1.2 °C and was unaffected by treatments. The DM intake, milk yield, and concentrations of protein, fat, and lactose, as well as total tract apparent digestibility of DM and OM were similar among treatments ( P >0.1). Digestibility of CP was higher in the HCP diets ( P P P P >0.1), while NEFA level was higher in LRDOM ( P P P P