In the first trial, the high-protein animals made a much greater gain of protein than did the low-protein ones. In the second trial, Nos. 72, 73 and 74 showed remarkably small gains, falling to at out the same low level, while No. 71 showed a more normal increase. As compared with the estimated "normal" gain of protein, computed in the manner described on p. 226, and with the amounts of digestible protein available for growth the results were as stated in Table 31. TABLE 31 Protein supply and daily gains per 1000 pounds live-weight Of the high-protein animals receiving protein largely in excess of the estimated minimum requirements and net energy not greatly below the estimated requirements, No. 71 closely approached the estimated "normal" gain while No. 72 fell about 25% below it in the first trial and about 66% below it in the second trial. This animal was described by the authors as "unthrifty." On the other hand, both of the low-protein animals, on rations approaching the estimated requirements as regards energy, but with a protein supply distinctly below the estimated minimum, showed a rate of gain notably below the "normal." LIVE WEIGHTS AND GAINS The average live weights for 10 days at several intervals as compared with Eckles' results for the same ages, and the mean daily gains, are shown in Table 32. In proportion to their live weight (Table 33) the animals showed in the first period a tendency to more rapid gain in weight than the computed normal, i. e., they tended to make up lost time. In the second period, however, they fell much below the normal rate of increase, this difference being much larger on the low protein rations. On the whole, both the live weight results and the nitrogen balances show a distinct advantage on the side of the high-protein TABLE 33 Daily gain per 1000 average live weight at middle of period Before rations but indicate that even these animals failed to gain weight or store protein at the normal rate for their age and size. ascribing these differences to the difference in the protein supply, however, it is necessary to consider whether the rations furnished sufficient energy. In the first period, it appears from Table 29 that the net energy in both the high-protein and the low-protein rations was distinctly less than the estimated requirement yet the high-protein animals appear to have made almost a normal gain of protein (Table 31) and a super-normal gain of live weight for their size (Table 33). The low-protein animals, on the contrary, which received slightly less protein than the estimated minimum requirement, showed a distinctly sub-normal gain of protein but a nearly normal relative gain of live weight. In the second and longer period, the energy supply of all the animals was nearly equal to the estimated requirement. In this period No. 71 of the high-protein animals made almost a normal gain of protein, while No. 72 (the "unthrifty" animal) showed a very low gain, but both animals made about the estimated normal increase in live weight. The low protein animals, whose protein supply was about % of the estimated minimum requirement, showed a notably small increase in both body protein and in live weight. It would appear, then, despite some irregularities and uncertainties, that the protein content of the low-protein rations, which was considerably lower than was intended, was a limiting factor in the growth of these animals. INVESTIGATIONS AT THE VIRGINIA EXPERIMENT STATION (CONTINUED) EXPERIMENTS OF 1919 ANIMALS For this experiment four pure-bred Holstein bull calves were selected, all of them relatively large animals. No's 2 and 3 seemed less thrifty than the other two and were therefore placed in different groups. The ages and weights at the beginning of the experiment, on June 1st, 1919, were as shown in Table 34. No grouping of the animals by pairs is reported. The live weights are notably greater than those reported by Eckles for light-fed Holstein calves of corresponding ages. The rations as computed were intended to correspond to those given in the plan. As was the case with the exper ments of the previous year, the digestion trials showed that they were actually somewhat lower in net energy and decidedly lower in digestible protein than was intended. The first rations computed, the feeding of which was begun on June 1st, proved to be too bulky for the animals to consume completely. Accordingly a portion of the oat straw was withdrawn from the ration and starch substituted for it. The feeding of this new ration began on June 29 and extended to August 1. On that date the rations were increased in amount to correspond with the increase in weight of the animals but the amounts of protein and energy per 1000 |