Supplementation of grass hay with molasses in crossbred ( Bos taurus × Bos indicus) non-lactating cows: effect of timing of molasses supplements on feed intake, digestion, DM degradation and rumen fermentation

Abstract

An experiment was carried out to evaluate the effects of timing of molasses supplementation on feed intake, diet digestibility, degradation of hay dry matter (DM), rumen pool size of total ingesta and neutral detergent fibre, and rumen fermentation. Four ruminally fistulated Friesian ( Bos taurus) × Boran ( Bos indicus) crossbred non-lactating cows, in a balanced 4 × 4 Latin square experiment, were given a basal diet (Diet C) of grass hay ad libitum and 2.0 kg DM of noug ( Guizotia abyssinica) cake per day. The other three diets were supplemented with 2.0 kg DM day −1 of sugar-cane molasses given at the same time as a meal of the basal diet (Diet M0), or 1 h after (Diet M1) or 2 h after (Diet M2) a meal of the basal diet. The DM intake of hay was highest (8 vs. 7 kg) when molasses was given at the same time as the basal diet. The effect of molasses on total DM intake was additive, so that the intake of total DM increased ( P < 0.001) the molasses supplement. The apparent digestibility of DM was increased from 0.57 to 0.61 by including molasses in the diets ( P < 0.01). The molasses diets had no significant effect ( P > 0.05) on the degradation parameters of DM of grass hay. Molasses supplements decreased ( P < 0.001) the mean concentration of ammonia from 14.6 to 9.9 mmol l −1. The molar proportion of acetate was lower in molasses-containing diets (714 vs. 659 mmol mol l −1, P < 0.001), and those of propionate (171 vs. 206 mmol mol l −1, P < 0.001) and butyrate (94 vs. 117 mmol mol l −1, P < 0.01) were higher.