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• Probiotics were not effective in improving calf performance under experimental conditions.
• Calves under stressed conditions may respond to probiotics.

Probiotics are used to control or maintain a constant state of intestinal bacteria. When the bacterial populations are altered by stress or antibiotic therapy, animal health and performance may decline. Probiotics should be most effective when fed to animals that are undergoing stress. Illinois researchers (1994) reported increased dry matter intake and average daily gain when calves were fed a probiotic in the summer, but not in the spring. The seasonal effect was due to a more stressful environ- ment in the summer period. This experiment was design to study the effects of feeding a probiotic to dairy calves in winter conditions.

Twenty-four female and fourteen male calves were randomly assigned to two treatments. Calves were either fed a control diet or the control diet supplemented with a probiotic for 6 weeks. One half of the calves received 1/4 teaspoon liquid dispersible direct fed microbials¹ and non-specific proteins daily in milk for 6 weeks. All calves were fed colostrum and moved to individual hutches at two days of age. Each calf was fed whole milk twice a day at a rate of 10 percent of body weight for the first 5 weeks. All calves were then fed whole milk once per day at 5 percent of their body weight during the sixth week. All calves were fed a calf starter (Table 1) ad libitum for 7 weeks. Water was available free choice and calves remained in hutches for the duration of the experiment. Body weight of each calf was measured at birth. Body weight, height at the withers, body length, and heart girth were measured at 2 days (when moved to hutch) of age and weekly throughout the experiment. Fecal scores were assigned daily to evaluate health status. Data were analyzed using the general linear models procedure of SAS. Body weight measured on day two (hutch weight) after birth for each calf were used as a covariate for all analyses.

The results of the experiment are summarized in Table 2. Hutch weight was significantly higher for male calves and was corrected for in all other measurements. Average daily intakes were not affected by probiotic supplementation. A sex by treatment interaction was observed with male calves supplemented with probiotics consuming more starter than control calves and an opposite effect on female calves. Average daily gain was unaffected by treatment, however male calves significantly (P <0.01) gained more than female calves. Female calves fed probiotics were more efficient in feed conversion that control calves. These observations were reversed in male calves. Average daily fecal score, wither height, body length, and heart girth were similar between sexes and treatments. Overall, probiotic supple- mentation had little effect on calf growth and health. A relatively mild winter may not have put enough stress on calves to cause a positive probiotic response. The differences observed between sexes can not be explained.

¹ Direct fed microbials consisted of S. cervisiae, S. faecium, and L. acidophilus, Conklin Inc.

TABLE 1. Ingredients and nutrient composition of calf starter.

TABLE 2. Average daily intakes, body weight gains, feed:gain, fecal scores, and body measurements from day 2-49 from calves fed control or probiotic supplemented diets.