Nitrogen metabolism and hormonal responses of steers fed wheat silage and infused with amino acids or casein.

Abstract

Four Holstein steers (159 kg) surgically fitted with abomasal-infusion cannulas were used in a 4 x 4 Latin square study to test amino acid (AA) and casein (CAS) infusions on nitrogen balance and hormonal status of steers consuming vegetative wheat (Triticum aestivum L.) silage (12.3% CP). Treatments were 5-d infusions of 1) water (CONT), 2) arginine (ARG; 13.69 g/d), 3) limiting amino acids (LAA, 13.69 g/d arginine + 10.92 g/d histidine + 28.97 g/d lysine + 10.88 g/d methionine + 16.96 g/d threonine, and 4) Na-CAS (300 g/d). Whole blood was collected for plasma AA, growth hormone (GH), insulin, and IGF-I concentrations. Data were analyzed by ANOVA, and the following orthogonal contrasts were used to separate treatment means: CONT vs ARG; ARG vs LAA; and LAA vs CAS. Urinary N increased (P < .02) for CAS vs LAA. Arginine increased N retention, as did CAS, compared to LAA. Total plasma essential AA were decreased by arginine. Mean plasma insulin concentrations were increased by CAS (P < .034). Arginine increased mean plasma GH levels, but not IGF-I. The CAS treatment increased (P < .015) IGF-I levels, but not GH. These data suggest that performance of steers fed wheat silage was limited by duodenal AA flow and that arginine was the first-limiting AA. Casein infusion increased plasma insulin and IGF-I, which would explain the improved growth noted in calves and lambs fed forages supplemented with ruminally undegraded protein.

Determination of the methionine requirement of growing double-muscled Belgian blue bulls with a three-step method.

“…Treatment 1 did not contain Na- tively. This experiment also confirms that digestible AA complements can have biological values higher than 1.0 (Storm and Ørskov, 1984;Ragland-Gray et al, 1997). Here, the infusion of 1.6 g/d of N (in Met form) improved N retention 11-fold.…”

Effects of urea, isolated soybean protein and blood meal on growing steers fed a corn-based diet

“…Higher plasma insulin concentrations were observed after abomasal casein infusion in steers (Guerino et al, 1991;Ragland-Gray et al, 1997;Robinson, 1998) and lambs (Beermann et al, 1991). However, we did not observe an increase in glucose, NEFA or insulin (P > 0.05).…”

The effects of concentrate added to pineapple (Ananas Comosus linn. Mer.) waste silage in differing ratios to form complete diets, on digestion, excretion of urinary purine derivatives and blood metabolites in growing, male, Thai swamp buffaloes

“…This is in agreement with McGuire et al (1992), who found that with increased dietary crude protein, given to lactating dairy cows, plasma insulin was higher but there was no increase in plasma glucose and NEFA. Similarly, Guerino et al (1991) and Ragland-Gray et al (1997) found higher plasma insulin after the infusion of casein into the abomasum in steers. But, Knaus et al (2002) observed that plasma glucose and NEFA in growing cattle did not increase when the protein in the diet increased.…”