Four cracked corn-based diets supplemented with 0, 5, 10 and 15% soybean meal (SBM) were fed to weaned male Holstein calves to study effects of protein level on digestibility and nitrogen balance, in one trial, and on feed intake, in another. Twelve calves were used in each trial in a replicated 4 x 4 Latin square design. Calves were 9 to 12 weeks of age at the start of the experiment and diets ranged from 9.9 to 16.2% crude protein (CP). In trial 1; feed intake was restricted to 80 g dry matter (DM) per kilogram metabolic body weight (W-75). There was a linear change (P less than .01) in apparent DM digestibility, increasing from 71.1% with the low protein diet to 75.1% with the high protein diet. Similar significant trends were observed in digestibility of organic matter (71.2 to 75.3%), nitrogen (61.6 to 72.2%), acid detergent fiber (36.2 to 44.8%) and starch (86.3 to 89.7%). Fecal starch decreased, from 28.4 to 22.1% of DM, and fecal pH increased, from 5.21 to 5.52, as SBM was substituted for corn; both of these trends were significant (P less than .01), linear component); they were also correlated (r = .55, P less than .01). Nitrogen (N) retention increased with dietary protein level (P less than .01, linear component), from 9.0 to 10.9 to 11.9 to 13.2 g N/kg digestible organic matter intake for diets 1 through 4, respectively. The same percentage of nitrogen intake was retained on all diets, but the amount of absorbed nitrogen that was retained decreased with dietary protein level (P less than .01, linear component) from 63.0% with 9.9% CP to 51.4% with 16.2% CP. In trial 2, voluntary feed intake averaged 98.2, 110.1, 106.3 and 106.5 g DM/W-75 for diets 1 to 4, respectively, (P less than .05, quadratic component). Live weight gain increased in a linear manner (P less than .01) with increasing CP, from .77kg/day with diet 1 to 1.22 kg/day with diet 4.

No abstract

In trial 1, the effects of dietary energy (102, 131 or 162% of requirement) in the dry period and of sodium bicarbonate (0 or .75% of diet dry matter) in early lactation were assessed with 31 cows in a 3 X 2 factorial arrangement of treatments. Body condition and weight increased linearly with prepartum energy. Dry matter intake and milk yield were similar across treatments through 12 wk postpartum. Sodium bicarbonate increased milk fat content only in the 131% group, an effect apparently related to greater mobilization of fat in that group. In trial 2, energy treatments imposed in late lactation (145 to 55 d prepartum) and in the dry period (55 to 0 d) were 1) cows fed to requirement in both periods, 2) cows overfed in the first and underfed in the second period, 3) cows fed to requirement in the first and overfed in the second period, and 4) cows overfed in both periods. Cows in treatments 1 and 2 (normal) calved in a thinner state than those in 3 or 4 (fat). In the first 12 wk postpartum, intake did not differ, but cows in groups 3 and 4 produced more milk. Sodium bicarbonate imposed factorially postpartum increased milk fat content. Overconsumption of energy prepartum did not impair production when high energy total mixed rations were fed postpartum.

ABSTRACT

No abstract