Effects of maize silage supplementation before lucerne grazing on the occurrence of bloat in cattle
The effects of maize silage supplementation, before lucerne grazing, on the occurrence of pasture bloat were studied under the hypothesis that this treatment could reduce the severity of this digestive disorder. The experiment was divided into two trials. Six ruminally fistulated heifers were used f...
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| Autores principales: | , , , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00288233_v44_n4_p241_Bretschneider |
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| Sumario: | The effects of maize silage supplementation, before lucerne grazing, on the occurrence of pasture bloat were studied under the hypothesis that this treatment could reduce the severity of this digestive disorder. The experiment was divided into two trials. Six ruminally fistulated heifers were used for the study of ruminal parameters, and in vitro measurements and 36 heifers were used for the study of bloat score. Treatments were: T1, no supplement; T2, 0.5% body weight of maize silage dry matter animal-1 day-1; and T3, 1.0% of the same supplement. Lucerne was grazed ad libitum in the vegetative to pre-bloom stage using a daily rotational grazing system. Visual bloat score in non-supplemented animals was higher (P < 0.01) than in the treated groups but it did not differ (P > 0.01) between the different supplementation levels. When lucerne leaflets were mixed in vitro with inoculum from T1, T2, and T3 animals, differences in microbial gas production were detected (P < 0.01) between T1 and T3 from the fourth hour of incubation, and between T1 and T2 from the twelfth hour of incubation. Soluble protein concentrations in the liquid phase of these in vitro incubates were lower (P < 0.05) for T1 than for T2 and T3, but soluble carbohydrate concentrations did not differ. In the ruminal fluid from the fistulated heifers, proteolytic activity, pH, and total N-NH3 and N-NH4 + concentrations did not differ (P > 0.05) among treatments. When sampled at the first (0800 h) and second (1200 h) sampling times, N-NH3 concentrations were higher (P < 0.05) for T1 at both sampling times. Thus, maize silage supplementation at 0.5% and 1.0% of body weight before lucerne grazing reduced bloat occurrence and severity. Although the mechanisms involved in the control of this digestive disorder could not be clearly demonstrated, it is suggested that the lower fermentative capacity of the ruminal fluid from supplemented animals would reflect a reduction of the rumen-free microbial population, which is the one available to attack bloating legumes immediately after the legumes reach the rumen. A reduced free rumen microbial population would lead to a slower release of soluble nutrients from lucerne leaflets and, consequently, to a reduction in bloat development. |
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