This study aimed to evaluate the whole soybeans as a substitute for protein pellets in highgrain diets, with or without roughage, for cattle and its effects on dry matter (DM) and
nutrients intake and digestibility, as well determine the ruminal and blood parameters. Four
crossbred males cannulated in the rumen were used and distributed in a 4 x 4 Latin Square
Design (four animals and four diets) in a 2 x 2 factorial arrangement, two sources of protein
(protein pellet vs. whole raw soybean), with or without roughage (Mombasa grass silage
corresponding at 15% of the dry matter of the diet). The trial lasted 80 days. There was a
higher dry matter intake (DMI) for the diet with the pellet compared to the diet with soybeans
(P = 0.04, 13.57 vs. 9.91 animal-1 day-1). The inclusion of roughage in the diet increased
DMI (P = 0.05). Crude protein intake was not affected by protein sources or inclusion of
roughage (P> 0.10). The inclusion of roughage in the diet allowed an increase in the neutral
detergent fiber intake (P <0.01), while the use of soybeans did not change the ether extract
intake (P> 0.10). The use of the soybean replacing the pellet and the inclusion of 15%
roughage in the diet promoted a similar diets total digestible nutrients intake (TDN) (p> 0.10)
with an average of 8.71 kg day -1. There was no influence of diets on the digestibility of DM,
CP or TDN of the diets (P> 0.10), 0.57; 0.49 and 74.47%, respectively. Greater total
carbohydrates digestibility was observed for diets without roughage (0.73 vs. 0.56). The diets
with roughage had a ruminal pH mean higher than those without roughage (P = 0.10), 6.13
vs. 5.77. The use of soybeans in the diet allowed a similar concentration of ruminal
ammoniacal nitrogen (P> 0.10), 5.26 mg, when it was compared to the use of the protein
pellet. There was also no influence of diets on plasma levels of urea, total proteins, albumin,
triglycerides, creatinine, AST and ALT (P> 0.10). Higher amounts of cholesterol and glucose
were found in the plasma of animals fed soybeans as a protein source (P = 0.05). The use of
whole raw soybean as a protein source in high-grain diets for cattle reduces the intake of dry
matter, however, it allows to keep the intake of nutrients and NDT without changing the
ammonia nitrogen levels and rumen pH, in addition to maintaining blood parameters within
normal concentrations. The supply of 15% silage in a high-grain diet for feedlot cattle
increases the dry matter intake and maintains the energy intake of the diet, in addition to
maintaining the average ruminal pH above 6.0.
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