The importance of abomasal protein clotting for optimal nutrient utilization, health and growth of milk-fed calves remains a controversial issue. Clotting of casein in whole, waste and colostral milks was thought to be responsible for improved digestibility, greater daily gains and improved calf health. Early milk replacers were formulated with casein containing protein sources. The milk replacer industry in the United States is currently using protein sources that are non-clotting, primarily whey and soy protein, in the formulations of replacers. In the past, milk replacers that exhibited no curd formation were characterized as inferior because of their association with poor growth rates and high incidences of diarrhea. Research suggests that factors other than clotting are directly responsible for this decreased performance. The calf's immature digestive system during the first three weeks of life indicates a physiological need for clotting in the abomasum to fully utilize complex proteins. Thus whole milk proteins are suggested by some as the most suitable liquid diets for this age. Enzymatic secretion is limited up to one month of age, restricting digestion of carbohydrate, fat and protein. After three weeks of age most calves can perform comparably when fed non-clotting milk replacers. Inhibition of coagulation with an oxalate-sodium buffer illustrated that clotting may only affect nutrient flow and not nutrient digestibility or performance of calves. Therefore, clotting may not be the fundamental element causing poor performance. Evidence suggests that the types of protein sources, the manufacturing methods and the inclusion of other less digestible sources of nutrients in the milk replacer may be the components hindering the growth and health of calves less than one month of age. The physical or chemical nature of milk substitutes as well as their digestibility may influence the nutrient delivery from the abomasum to the small intestine. The milk replacer industry in the US has been formulating milk replaces based on calf performance rather than only analyzed quality.
All Science Journal Classification (ASJC) codes
- Animal Science and Zoology