Heat-treated whole cottonseed versus maize gluten meal as a rumen undegradable protein supplement for lactating dairy cows

Abstract

The effect of heat treatment on the nutritive value of rumen undegradable protein (UDP) fraction of whole cottonseed (WCS) was studied in this experiment. Forty two multiparous Israeli Holstein cows were used in a multiple double 3×3 Latin square design. Milk production averaged 38±4.1 kg at the beginning of the experiment. Three different diets were formulated to contain 160 g/kg crude protein (CP), 365 g/kg neutral-detergent fibre (NDF) on a dry matter (DM) basis, 7.24 MJ net energy for lactation (NE L)/kg DM and 170 g/kg WCS. 30% of dietary CP was of cotton origin. Diets were (1) whole cottonseed (WCS), (2) heated whole cottonseed (HWCS) and (3) whole cotton seeds plus 3.1% maize gluten meal (WCS+MG). Diets with HWCS and WCS+MG contained 60 g UDP/kg DM compared with 54 g UDP/kg DM in the WCS treatment. Heat treatment decreased ruminal CP degradability of WCS by 22% and ruminal organic matter (OM) degradability by 5%. Intakes of DM, OM and CP were similar across diets. Higher apparent total tract digestibilities of DM and OM were determined in HWCS and WCS+MG diets (0.62 and 0.64 and 0.63 and 0.65, respectively) compared to WCS diet (0.59 and 0.62, respectively). Higher ruminal propionate proportion was determined in diets containing WCS and WCS+MG over the sampling hours. A higher ruminal ratio of acetate:propionate was measured in the diet containing HWCS. Ammonia N concentration was similar in all treatments, however, blood urea N concentration was the lowest at 3 and 6 h after feeding in the HWCS diet compared to the other diets. Milk yield and composition were similar for all treatments and averaged 34.2±0.45 kg/d with 34.2 g fat/kg, 30.1 g CP/kg and 47 g lactose/kg. It was suggested that inclusion of HWCS in diets for high-yielding dairy cows decreased the endogenous catabolism of amino acids. In this study the effect of heat treatment on WCS on the performance of cows was not apparent because the cows consumed surplus of dietary CP.