Growth and body composition of dairy calves fed only milk replacer at 3 intakes.

Determination of energy requirements for growth depends on measuring the composition of body weight (BW) gain. Previous studies have shown that the composition of gain can be altered in young dairy calves by composition of the milk replacer diet. Here, our objective was to determine body composition and the composition of empty body gain in young calves fed increasing amounts of a milk replacer containing adequate CP. Male Holstein calves underwent an adjustment period of 14 d after birth in which they were fed whole waste milk at 10% of BW. Calves were then stratified by BW and randomly assigned to either an initial harvest group (n = 11) or to groups fed 1 of 3 milk replacer amounts and harvested after 35 d of growth. All treatments consumed the same milk replacer containing 24.8% CP (dry matter [DM] basis; from all milk proteins) and 18.9% fat, reconstituted to 12.5% solids. Treatments were milk replacer fed at 1.25% of BW (DM basis; n = 6), 1.75% of BW (n = 6), or 2.25% of BW (n = 8), adjusted weekly as calves grew. Calves fed at 1.25% or 1.75% of BW were fed twice daily and those fed 2.25% of BW were fed 3 times daily. No starter was offered. Post harvest, the bodies of calves were separated into 4 fractions: carcass; total viscera minus digesta; head, hide, feet, and tail; and blood. The sum of those 4 fractions was empty BW, which increased linearly as amount of milk replacer increased. Final heart girth and body length, but not withers height, increased linearly as intake increased. Gain:feed increased linearly with increasing milk replacer. Feeding more milk replacer increased the amounts of lean tissue and fat in the body. The percentages of water and protein in the final body decreased linearly, whereas fat percentage and energy content increased linearly as intake increased. As gain increased, the percentage of protein in gain decreased and the percentage of fat increased, resulting in an increase of energy content of EBW gain. Efficiency of energy use (retained energy:gross energy intake) increased linearly but retained energy:metabolizable energy available for growth was not different among treatments. Efficiency of protein use increased quadratically as feeding rate increased; there was no further increase at 2.25% of BW. Plasma insulin-like growth factor 1, insulin, and glucose increased linearly, whereas urea-N decreased linearly, as milk replacer intake increased. Our data document changes in body composition that affect estimates of retained energy in the bodies of calves harvested at a common age. These data are important for calculations of energy requirements for young calves.

Supplementation of 1% L-glutamine to milk replacer does not overcome the growth depression in calves caused by soy protein concentrate.

Glutamine, an important fuel and biosynthetic precursor in intestinal epithelial cells, helps maintain intestinal integrity and function when supplemented to the diet of many species. The hypothesis tested here was that glutamine supplementation would overcome the decreased average daily gain (ADG) and altered intestinal morphology caused by milk replacer containing soy protein concentrate (SPC). Holstein calves (9 male and 1 freemartin female per treatment) were assigned to diets of 1) all-milk-protein (from whey proteins) milk replacer, 2) milk replacer with 60% milk protein replacement from SPC, and 3) SPC milk replacer as in diet 2 plus 1% (dry basis) l-glutamine. Milk replacers were reconstituted to 12.5% solids and were fed at 10% of body weight from d 3 to 10 of age, and at 12% of body weight (adjusted weekly) from d 10 through 4 wk of age. No dry feed (starter) was fed, but water was freely available. Glutamine was added at each feeding to reconstituted milk replacer. Five calves from each treatment were slaughtered at the end of wk 4 for measurements of intestinal morphology. The ADG was greater for calves fed the all-milk control than for those fed SPC; glutamine did not improve ADG (0.344, 0.281, and 0.282 kg/d for diets 1 to 3, respectively). Intake of protein was adequate for all groups and did not explain the lower growth for calves fed SPC. Villus height and crypt depth did not differ among treatments in the duodenum. In the jejunum, villus height (713, 506, and 464 mum, for diets 1 to 3, respectively) and crypt depth (300, 209, and 229 mum, respectively) were greater for calves fed all milk protein than for either SPC group. In the ileum, villus height was greater for calves fed all milk than for either soy group (532, 458, and 456 mum), whereas crypt depth tended to be greater (352, 301, and 383 mum for diets 1 to 3, respectively), and the villus to crypt ratio was lower for calves supplemented with glutamine than for those fed SPC alone. Urea N concentration in plasma was greater for calves supplemented with glutamine than for those fed SPC alone, indicating that glutamine was at least partially catabolized. Supplemental l-glutamine did not improve growth or intestinal morphology of calves fed milk replacer containing SPC.

Growth and body composition of dairy calves fed milk replacers containing different amounts of protein at two feeding rates.

Previous research has demonstrated that increasing the CP concentration from 16 to 26% in milk replacers fed to male preruminant dairy calves at 1.5% of BW (DM basis) daily resulted in increased ADG, G:F, and deposition of lean tissue. However, the effects of dietary CP would be expected to vary depending on ME intake. Here, male Holstein calves < 1 wk old were used to determine the effects of feeding rate and CP concentration of isocaloric, whey protein-based milk replacers on growth and body composition. After a 2-wk standardization period, calves were assigned randomly to an initial baseline group or to treatments in a 2 x 4 factorial arrangement of feeding rate (1.25 or 1.75% of BW daily, DM basis) and milk replacer CP concentration (14, 18, 22, or 26% of DM). No starter was offered, but calves had free access to water. After a 5-wk feeding period, calves were slaughtered and body composition was determined. Increasing the feeding rate increased (P < 0.05) ADG, G:F, empty-body gains of chemical components and energy, the percentage of fat in empty BW gain and in the final empty body, and concentrations of IGF-I and insulin in plasma. Increasing the feeding rate decreased (P < 0.01) percentages of water and protein in the empty body and decreased urea N in plasma. Increasing dietary CP concentration linearly increased (P < 0.05) ADG, body length, heart girth, and gains of water and protein but linearly decreased (P < 0.05) fat gain. As dietary CP increased, fat content in empty body gain decreased, and water and protein increased. Increasing CP concentration increased (quadratic, P < 0.02) G:F, with greatest efficiencies for calves fed 22% CP. Gross energetic efficiency (retained energy:intake energy) was greater (P < 0.05) for calves fed at 1.75% of BW daily. Efficiency of dietary protein use for protein gain was greater for calves fed at 1.75% of BW daily but was not affected by dietary CP. The ratio of protein gain to apparently digestible protein intake above maintenance decreased as dietary CP increased. Interactions (P < 0.05) of feeding rate and CP concentration for gains of water and protein indicated that when dietary CP was 26% the ME supply limited protein use by calves fed at 1.25% of BW daily. Body composition of preruminant calves can be markedly altered by manipulating the protein to energy ratio in milk replacers. These dietary effects on body composition and growth are not predicted by current NRC standards.