Can you feed a milk replacer containing soy protein concentrate without depressing calf growth?

University of Illinois researchers added the amino acid glutamine to a soy-based milk replacer in hopes of doing just that. However, it did not improve average daily gain or feed efficiency, according to study results published in the May Journal of Dairy Science.

Soy proteins commonly serve as an alternative to milk proteins in milk-replacer formulas. In most cases, soy protein replaces a portion — usually 50 percent or less — of the milk protein in milk-replacer formulas. Although this substitution lowers the cost of the milk replacer, you can expect to see reduced calf growth and feed efficiency in young calves, particularly those less than two weeks of age.

During the University of Illinois study, the researchers fed one of three treatments:

1. An all-milk-protein milk replacer.

2. A milk replacer in which soy protein concentrate replaced 60 percent of the whey protein.

3. The same milk replacer as used in treatment 2, but supplemented with 1 percent glutamine.

All three milk replacers contained 20 percent crude protein and 15 percent fat. Free-choice water was always available, but no starter grain was fed. Calves began the experimental protocol on day 3 of age — after they were fed colostrum — and were on the protocol for about 28 days.

The results, summarized in the following table, show roughly an 18-percent decrease in average daily gain in both soy-protein treatments versus the whey-protein treatment. Calves fed soy protein also saw a 14.5-percent decline in feed efficiency. 

                                                                         Milk Replacer Treatment
                         All milk protein            Soy protein     Soy protein concentrate, 
                                                                concentrate             plus glutamine
Average Daily Gain   0.76 pounds   0.62 pounds      0.62 pounds                                     
Gain-to-feed Ratio          0.55                   0.47                         0.47

May 2006 Journal of Dairy Science