Diets rich in energy concentrates improve feed efficiency, although they require precise
nutritional management care. Replacing protein pellets with soybeans can be an
economically viable alternative, maintaining the production of short-chain fatty acids
without affecting metabolism. Therefore, the objective was to evaluate whole soybeans
as a substitute for protein pellets in high-concentrate diets, with or without roughage,
for cattle, and its effects on short-chain fatty acids. Four (04) crossbreed male dairy
cattle cannulated in the rumen were used, distributed in four treatments: 1. Pelletized
nucleus + whole grain corn (proportion 15 and 85%, respectively), 100% concentrate
diet; 2. Pelleted kernel + whole grain corn (proportion 15 and 85%, respectively) +
Mombaça grass silage, diet with 85% concentrate and 15% roughage; 3. Whole grain
soy + whole grain corn (proportion 15 and 85%, respectively), 100% concentrated diet;
and 4. Whole grain soy + whole grain corn (proportion 15 and 85%, respectively) +
Mombaça grass silage, diet with 85% concentrate and 15% roughage. The
experimental design was a 4 x 4 Latin square (four animals with four diets) with a 2 x
2 factorial arrangement (two sources of protein, pelleted nucleus or raw whole soybean
grain, and with or without roughage). The proportion of short-chain fatty acids, acetic,
propionic, butyric acids and the acetate/propionate ratio in the rumen fluid were
evaluated by treatment and at collection times (0; 2; 4 and 8 hours after feeding).
Analyzing the production of short-chain fatty acids, it was observed that there was no
interaction in the production of acetate. The production of SCFA in relation to pellet
and soybean protein sources with the inclusion or not of roughage, a significant effect
(p<0.05) was observed for the variable of protein source and inclusion or not of
roughage in the diet on acid production acetic acid, however, there was no interaction
between these evaluated factors. An interaction effect (p<0.05) was observed between
the protein source (FP) and the inclusion of roughage (Vol) for the short-chain fatty
acids propionate and butyrate, as well as for the acetate: propionate ratio. In the
ruminal fluid collection times and their respective SCFA production, it was observed
that there was no interaction effect of ruminal fluid collection time versus treatment
(P>0.05) on the SCFAs studied, with no effect of time for any of the FAs. studied. Diets
with protein pellets had a higher proportion of acetate than diets with soybeans. The
inclusion of 15% roughage in high-concentrate diets increased the proportion of
propionate and the inclusion of soy in the diet decreased the acetate-propionate ratio.
No interaction was observed between collection time and treatments on SCFA
concentrations, which suggests stability in these parameters over time.
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