Skip to main content
ARS Home » Plains Area » El Reno, Oklahoma » Grazinglands Research Laboratory » Forage and Livestock Production Research » Research » Publications at this Location » Publication #169376


item Phillips, William
item Grings, Elaine

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2005
Publication Date: 4/15/2005
Citation: Phillips, W.A., Grings, E.E., Holloway, J.W. 2005. Effects of a single dose of direct-fed microbials on performance of stocker calves grazing annual cool season grasses. Professional Animal Scientist. 21(2):88-92.

Interpretive Summary: Millions of calves are transported from the farm on which they were born and reared to the southern Great Plains region to graze annual cool season grass pastures before entering a feedlot for finishing. Wheat forage is an unfamiliar feed to most of these stocker calves and they are hesitant to readily consume a strange feed source. Wheat forage also contains high concentrations of digestible energy and protein, which can cause digestive disorders if too much wheat forage is consumed too quickly. Adding a combination of Lactobacillus and Enterococcus bacteria to the diet of beef calves has been shown to increase appetite and daily gain. This practice has not been evaluated in stocker calves to mitigate poor performance when the calves are first placed on cool season grass pasture. A single dose of bacteria did improve stocker calf performance during the spring grazing season but not during the fall grazing season. Chemical composition of cool season grasses in the fall is different from that observed in the spring and may account for the lack of a consistent positive response.

Technical Abstract: Previous research has shown that beef calves have low ADG during the first three weeks of grazing winter wheat pastures. Three experiments were conducted to determine the impact of a single oral dose of direct-fed microbials (DFM) on the overall performance of stocker calves grazing annual cool season grass pastures. Calves received 0 g (Control) or 15 g (DFM) of a gel paste that contained 10 million colony forming units (CFU) of bacteria/g of product before initiation of grazing. Within an experiment, control and DFM calves were grazed together in the same pasture. In Exp. 1 steer calves (N=241) grazed wheat pastures in the spring for 77 d. Calves in the DFM group gained more (P = 0.02) BW than calves in the Control group. Experiments 2 and 3 were conducted in the fall. Heifers (N=53; Exp. 2) and steers (N=61; Exp. 3) grazed pastures containing a mixture of wheat, triticale and annual ryegrass for 73 d (Exp. 2) and 83 d (Exp. 3). A single dose of DFM did not increase BW gains during the fall and winter gazing period. These data support the conclusion that a single dose of DFM can improve stocker gains in the spring. Comparison of stocker performance during the spring and fall grazing periods was confounded by forage source as well as seasonal differences in forage chemical composition.