Soybean Protein Substitute for Milk Protein in Milk Replacers for Suckling Calves

Abstract

Eight experiments evaluated soy protein concentrate (60 to 65%) and toasted soybean meal (44 to 48%) as protein sources in milk replacers when fed alone or with concentrates and hay. In the soy milk replacers soy protein contributed 50 to 88% of the total protein. All-milk protein replacers served as control. Israeli-Friesian calves (138) were started on the experimental diets when 3 to 4, 7 to 10, or 30 days old; each experiment lasted 42 days. The growth rate of calves fed soy replacers only from 7 to 10 days of age was approximately 20% less than that of the calves fed all-milk replacers. When concentrates were supplied, the gap decreased to about 10% (not significant). Blood urea indicated a better utilization of the absorbed soy protein when concentrates were consumed by the calves. There was no difference in the growth rate when calves were started on experiment at 30 days of age. Digestibility of food components increased from first to third week on the diet, increasing more for the soy diets. When soy products were included in milk replacers, absorption of fat and ash from the diets decreased. No differences were found for pH, dry matter or nitrogen content of the rumen liquor between control and experimental groups. Soybean meal, supplying 73% of the total milk replacers protein, induced less growth due to low protein digestibility (50%) and reduced fat and ash absorption. No difficulties were encountered in feeding the soy replacers: overall animal performance and health were satisfactory. Milk replacers containing soy protein concentrate up to 88% of the total protein can be used provided a concentrate cereal-soybean meal containing 16% crude protein is supplied. © 1972, American Dairy Science Association. All rights reserved.