P. Vázquez

Effects of monensin and yeast supplementation on blood acid-base balance in finishing feedlot steers fed a high-grain, high-protein diet

The aim of this study was to evaluate the effects of two dietary supplements (monensin and a live yeast culture) on acid-base balance in steers maintained in a commercial feedlot system, considering effects over the finishing productive cycle. Steers (no. =42) were allotted randomly to one of the three study groups: (1) control group (no supplementation, C), (2) monensin supplementation (MON), and (3) live Saccharomyces cerevisiae strain 47 supplementation (SACC). Venous blood samples were collected for the measurement of acid-base parameters and l-lactate. Production parameters were also used as a complementary tool for understanding the internal changes associated with supplementation. During the finishing period, MON steers tended to gain more efficiently than C and SACC steers. In the C group, the finishing-period diet caused a progressive decline in blood bases, in line with the high-grain diet consumption. In contrast, supplemented animals did not show this trend, although lower HCO 3 − and base excess values were registered in SACC steers than in MON, indicating that ionophore supplementation is less effective for reducing blood base consumption than yeast supplementation. In our study, the lack of the expected response to yeast supplementation may be attributable to the high crude protein content of the ration, a common feature of commercial feedlot industries.

Effects of malate supplementation on acid-base balance and productive performance in growing/finishing bull calves fed a high-grain diet

This study investigated the effects of malate supplementation on blood acid-base balance and serum lactate levels in a 137-day feedlot experiment with bull calves. Animals were allotted to one of two experimental groups: (1) A control group (no supplementation), and (2) a group receiving a salt of DL-malic acid. Blood pH, pCO2, HCO3 −, base excess, serum L-lactate and productivity parameters were evaluated. Our data reveal that under the conditions of the present experiment malate supplementation did not have any significant effect on productivity parameters by comparison with non-supplemented animals. As regards acid-base balance, no significant effects attributable only to malate were observed. In conclusion, the time-course and the overall means of serum L-lactate for both groups in both growing and finishing periods (0.44 ± 0.04 mmol/l and 0.39 ± 0.02 mmol/l, respectively, for control animal; and 0.54 ± 0.03 mmol/l and 0.49 ± 0.01 mmol/l, respectively, for supplemented animals) suggests that malate does not have any beneficial effects in animals fed a diet of similar characteristics to that given in this study.