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Supplementation of grass hay with molasses in crossbred (Bos taurus × Bos indicus) non-lactating cows: effect of level of molasses on feed intake, digestion, rumen fermentation and rumen digesta pool size

1993; Elsevier BV; Volume: 41; Issue: 1 Linguagem: Inglês

10.1016/0377-8401(93)90092-x

1873-2216

Hannele Khalili,

Genetic and phenotypic traits in livestock

This 5 × 5 Latin square experiment evaluated the effects of the level of sugar-cane molasses on feed intake, diet digestibility, dry matter (DM) degradation of grass hay, rumen pool sizes and rumen fermentation. Five ruminally fistulated crossbred (Bos taurus × Bos indicus) cows were given a basal diet of grass hay ad libitum and 2.0 kg DM of cottonseed cake day−1 (Diet M0). The other four diets were supplemented with 1.5 (Diet ML), 3.0 (Diet MM) or 4.5 kg DM of molasses (Diet MH), or the MH diet supplemented with 0.6 kg of sodium bicarbonate (Diet MHB). The voluntary intake of hay decreased from 8.2 to 5.6 kg DM (linear effect, P < 0.001) with the level of molasses. The apparent digestibility of DM increased from 0.66 to 0.73 (linear effect, P < 0.01) but that of neutral detergent fibre (NDF) decreased from 0.68 to 0.60 (linear effect, P < 0.01) with the level of molasses. Sodium bicarbonate did not affect the intake of hay or the digestibilities of different dietary constituents (P > 0.05). The disappearance of hay DM from nylon bags decreased (linear effect, P < 0.001) with the level of molasses, so that for Diet MM depression was less than for Diet MH (quadratic effect, P < 0.05). The rumen pool sizes of total ingesta (90 vs. 80 kg, linear effect, P < 0.05) and DM were smaller (10.4 vs 8.3 kg DM, P < 0.01) with molasses diets. The rumen pool size of NDF was not affected (P > 0.05) by the treatments. Molasses reduced the mean value of rumen pH from 6.6 to 6.2 (linear, P < 0.001, and quadratic effects, P < 0.05) and concentration of ammonia from 9.5 to 5.8 mmol l−1 (linear effect, P < 0.001). The molar proportion of acetate decreased from 726 to 573 mmol mol−1 (linear effect, P < 0.001), and those of propionate and butyrate increased (from 160 to 205 mmol mol−1, P < 0.01, and from 106 to 205 mmol mol−1, P < 0.001) with the level of molasses.