Studies on the Utilization of Urea by Young Calves
III. The Ability of Urea Utilization of Early Weaned Calves
1973 Volume 44 Issue 10 Pages 512-516
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1973 Volume 44 Issue 10 Pages 512-516
To study the ability of early weaned calves to utilize urea, feeding experiment was conducted for 4 weeks from 9 to 13 weeks of age, followed by 5 days of digestion and nitrogen balance study. Throughout this period, the level of urea in the ration (starter and hay cube) was met to the generally accepted guidelines for mature cattle of not more than 1% urea in the ration air-dry matter and not more than one-fourth of the total protein equivalent from urea. Holstein male calves were weaned at 7 weeks of age and were divided into four groups of four heads each (A, B, C and D). Four experimental starters were used: Starter A or D were prepared as positive and negative control, respectively, and Starter B (urea supplement, 1.5%) or C (urea supplement, 1.2%) were formulated as to be equal to Starter A in the level of DCP (8.0%) and CP (11.4%), respectively. The results are summarized as follows. 1) The average daily gains of Group A, B, C and D were 0.37, 0.36, 0.37 and 0.23 kg, and feed conversion ratios were 8.87, 8.16, 9.30 and 12.34, and the levels of DCP intake were 60, 69, 57 and 33% of NRC requirement, respectively. 2) Group A, B and C retained significantly more nitrogen (P<.05) than Group D. The percent of nitrogen retained of N intake for Group A and B was significantly higher (P<.05) than that for Group D, and that for Group C, though non-significant, was higher than that for Group D. 3) The apparent digestibilities of crude protein, crude fiber and dry matter were significantly higher (P<.05), and those of NFE and energy tended to be higher for Group A, B and C than for Group D. 4) Group B tended to be higher than Group C in the amount of nitrogen retained and the apparent digestibility of crude fiber. 5) Differences among Group A, B and C in average daily gain, feed conversion ratio, nitrogen retention and apparent digestibility, were not significant (P>.05). Jap. J. Zootech. Sci., 44, (10):512-516.516 1973.10.
