Growth performance, metabolic and endocrine traits, and absorptive capacity in neonatal calves fed either colostrum or milk replacer at two levels

Colostrum (CO) contains high amounts, whereas whole milk and milk replacer (MR) contain small amounts, of bioactive and growth-promoting substances, s uch as IGF-I. An experiment was designed to study the effects of feeding CO or MR on the first 3 d to neonatal calves, followed by whole milk up to d 7, at low and high density. Intestinal absorptive capacity, plasma metaboli te and hormone concentrations, and growth performance were measured during the 1st wk of life. Body weight increased (P < .05) similarly in calves fed low or high amounts of CO but did not rise in MR-fed calves. Loose feces w ere more frequent (P < .05) and absorption of xylose on d 5 was lower (P < .01) in MR- than in GO-fed calves, but there were no effects of feeding den sity within GO-fed or within MR-fed groups. However, high feeding density w ithin CO-fed groups enhanced (P < .05) total protein, globulin, triglycerid e, cholesterol, and insulin concentrations, whereas in the initially high a nd low MR-fed groups only plasma glucose and insulin after the first meal a nd plasma NEFA on d 2 were modified (P < .05) by different feeding density. Thus, feeding different amounts of CO partly influenced protein and fat me tabolism in calves during the Ist wk of life, but it did not measurably aff ect intestinal function. However, feeding different amounts of MR, in the a bsence of CO, barely affected metabolic and endocrine traits and absorptive capacity. Thus, high density CO feeding, and therefore a high supply of nu trients, together with greater amounts of bioactive and growth-promoting su bstances influenced neonatal metabolism and growth more than a high density of MR feeding containing only small amounts of bioactive and growth-promot ing substances. Factors in addition to nutrient density seem to be importan t for the development of neonatal calves.