Effect of Protein Level in Calf Starters on the Growth Rate and Metabolism of Young Calves

Eighty two-day-old male and female calves representing the Holstein and Jersey breeds were used in two separate experiments, to deternfine the effect of protein level of calf starters on growth rate and metabolism of young dairy calves.In the first experiment, no significant differences were observed in growth rates of calves receiving starters containing either 12.2, 16.6, 20.2, or 24.3% crude protein.The most efficient gains made were on the 12.2 and 16.6% protein levels.In the second experiment, no significant differences were found among groups receiving either a 13.0, 20.0, or 23.7% crude protein starter.A starter containing only 8.5% crude protein supported growth at a significantly lower rate than any of the other starters.A 16.6% crude protein starter gave growth superior to any of the other groups, which may be explained in part by increased feed consumption.The most efficient gains as measured in terms of pounds of feed required per pound of gain were made by this group.The digestibility, nitrogen balance, and blood studies tended to confirm results obtained from growth studies.Based on these studies, it appears that dairy calves two to 84 days of age do not require starters eontaining more than 12.0 to 16.0% crude protein, to maintain normal growth when a limited amount of whole milk and a medimn to good quality alfalfa hay are fed.It was also shown that starters containing only 8.5% crude protein would not support normal growth, thereby indicating that the minimum protein level of calf starters is in excess of 8.5% crude protein.During the past several years, considerable research has been conducted (2,3,4,6,11,12) to determine the optimmn protein level of rations for swine and poultry.Results of studies in both fields have led to recommendations of lower protein rations.Some limited work (8,9,10) of this nature has been conducted using 3-to 4-mo.-oldcalves in which similar growth was obtained from feeding both high-and low-protein rations.In general, high-protein feeds are more expensive and, therefore, it is economically desirable to feed only the amount of protein required to maintain normal performance of the animals in question.The purpose of this study was to determine the minimum protein level of calf starters satisfactory for normal growth of calves raised on a limited milkhay-starter system.The results reported cover two separate experiments, and will be designated as Experiments I and II. ZX~'ERI~IEXT IProcedure.Forty two-day-old male and female calves were selected at random and divided into four similar groups based on breed and body weight.Each group, composed of five Jersey and five IIolstein calves, was raised to 86 days :