Supplementation of monensin and Optimase to beef cows consuming low-quality forage during late gestation and early lactation

Abstract

Two experiments were designed to investigate the effects of feeding monensin and/or slow release urea with a fibrolytic feed enzyme (Optimase; Alltech, Inc., Nicholasville, KY) on performance, milk production, calf growth performance, and blood metabolites in beef cows. Spring-calving cows and heifers were used in a completely randomized design in Exp. 1 (N = 84; 534 ± 68 kg initial BW) and Exp. 2 (N = 107; 508 ± 72 kg initial BW). Exp. 1 supplements were formulated to meet cow protein requirements and fed daily and included 1) cottonseed meal with no monensin (control); or 2) monensin added to control to supply 200 mg per head per d (MON). In Exp. 2, experimental supplements included 1) cottonseed meal/wheat middlings (CS) fed at a rate to provide adequate DIP and CP according to , 2) the CS plus soybean hulls and 61 g per cow per d Optimase (OPT), 3) the CS plus monensin to supply 200 mg per cow per d (MON2), and 4) OPT plus MON2 (Combo). Cows were fed in last trimester through early lactation in Exp. 1 and during 2nd trimester in Exp. 2. Data were analyzed using the Mixed procedure in SAS with animal as the experimental unit. In Exp. 1, treatment did not affect cow BW or BCS change (P > 0.19). Calf birth BW was not affected by dam treatment (P = 0.24); however, calves from dams consuming MON weighed more (P < 0.04) at d 45 and at trial end. Calves also had greater (P = 0.04) ADG from birth to trial end. Milk production did not significantly differ among treatments (P > 0.41). In Exp. 2, mean cow BW and BCS were similar (P > 0.35) among treatments on d 90. However, from d 0 to 54, cows assigned to the OPT supplement gained less BCS (P = 0.02) compared with cows assigned to the CS supplement. Cumulative BCS gain was greater (P < 0.01) for CS-fed cows than for cows fed the OPT and MON2 supplements, although it was not significantly different for cows fed the Combo supplement. These studies indicate that the influence of monensin on cow BW and BCS change is inconsistent. The potential for monensin supplementation to positively impact calf performance during early lactation seems to be clearer. Replacing a portion of oilseed N in the supplement with Optimase may marginally reduce cow performance. Further research is needed to determine both the effects of monensin and the implications of combining monensin with Optimase on forage intake and cow performance at various stages of production.

Effects of monensin inclusion and level of intake in limit-feeding strategies for beef cows1

“…However, these effects were not observed in the current study; inclusion of monensin did not affect cow BW change over the 56-d trial, nor did it affect measures of fat deposition or RE. Linneen et al (2015) did not observe changes in cow BW or condition score due to monensin supplementation in beef cows, while Walker et al (1980) reported 3.4% to 11.7% decreases in feed required for BW stasis in pregnant cows fed monensin, suggesting improved diet utilization or energy yield.…”

Stocking method and monensin supplementation effects on cow and calf performance and pasture productivity

“…Conversely, BW and BCS change was positively influenced by monensin supplementation to gestating cows in the second experiment in Linneen et al. (2015).…”

“…Experiment one in Linneen et al. (2015) showed no influence of monensin on BW or BCS change of lactating cows. In more dated research, the first experiment in Lemenager, Owens, and Totusek (1978) and Turner et al.…”

“…These studies suggest an improvement in feed efficiency among grazing cattle consuming monensin may translate to benefits to both the pasture and animal. Furthermore, improvement to calf productivity when dams consume monensin has also been documented (Clanton et al., 1981; Lemenager, Owens, Lusby, & Totusek (1978); Linneen et al., 2015).…”

Hormones and monensin use to improve pregnancy rates in grazing lactating beef cows in the semiarid region of Argentina

“…Feeding monensin to grazing beef cows did not affect BCS change in experiment 1, however differences between days were observed, and founding higher scores on day 80 of the experiment. In previous literature, cows consuming monensin during gestation had decreased forage intake, accompanied by either an improvement (Sexten, 2011) or no change in cow gain (Linneen et al, 2015). Bretschneider et al (2008) reported an increase in average daily gain of 12.1% for growing cattle consuming monensin when comparing 46 experiments in a review on the effects of feeding grazing cattle monensin.…”