title: Influence of methionine supplementation of growing diets enriched with lysine on feedlot performance and characteristics of digestion in Holstein steer calves.
abstract: OBJECTIVE
  Two trials were conducted in order to examine the effects of level of supplemental methionine on productive performance, dietary energetic, plasma amino acid concentration, and digestive function.
  
  
  METHODS
  Dietary treatments consisted of a steam-flaked corn-based diet containing urea as the only source of supplemental nitrogen supplemented with no supplemental amino acid (control), or control plus 1.01% lysine and 0.032%, 0.064%, 0.096%, or 0.128% methionine. In Trial 1, 150 Holstein steer calves (127±4.9 kg) were utilized to evaluate the influence of treatments on growth-performance, dietary energetic, plasma amino acid concentration during the first 112 days of growing period. During the initial 56-d period calves received the 5 experimental diets. During the subsequent 56-d period all calves were fed the control diet.
  
  
  RESULTS
  During the initial 56-d period, methionine supplementation increased (linear effect, p<0.01) plasma methionine. In the presence of supplemental lysine, increases on level of methionine in diet did not affect average daily gain. However, increased gain efficiency (quadratic effect, p = 0.03) and estimated dietary net energy (NE; linear effect, p = 0.05). Estimated metabolizable methionine supply was closely associated (R2= 0.95) with efficiency NE utilization for maintenance and gain. During the subsequent 56-d period, when all calves received the control diet (no amino acid supplementation), plasma amino acid concentrations and growth performance was not different among groups. However, the effects of methionine supplementation during the initial 56-period carried over, so that following a 56-d withdrawal of supplementation, the overall 112-d effects on gain efficiency (quadratic effect, p = 0.05) dietary NE (linear effect, p≤0.05) remained appreciable. In Trial 2, 5 cannulated Holstein steers were used to evaluate treatment effects on characteristics of digestion and amino acid supply to the small intestine. There were no treatment effects on flow of dietary and microbial N to the small intestine. Postruminal N digestion increased (p = 0.04) with increasing level of supplemental methionine. Methionine supplementation linearly increased (p<0.01) duodenal flow of methionine. Likewise, lysine supplementation increased an average of 4.6% (p = 0.04) duodenal flow of lysine. In steers that received non-supplemented diet, observed intestinal amino acid supply were in good agreement with expected.
  
  
  CONCLUSIONS
  We conclude that addition of rumen-protected methionine and lysine to diets may enhance gain efficiency and dietary energetics of growing Holstein calves. Observed amino acid supply to the small intestine were in good agreement with expected, supportive of NRC (2000, Level 1).
authors.affiliation: Research Institute of Veterinary Sciences, UABC, Mexicali, Baja California 21100, México.
authors.forename: Noemí
authors.initials: N
authors.lastname: Torrentera
authors.affiliation: Research Institute of Veterinary Sciences, UABC, Mexicali, Baja California 21100, México.
authors.forename: Ramsés
authors.initials: R
authors.lastname: Carrasco
authors.affiliation: PVeterinary and Animal Science School, UAT, Cd. Victoria, Tamaulipas 87000, México.
authors.forename: Jaime
authors.initials: J
authors.lastname: Salinas-Chavira
authors.affiliation: Research Institute of Veterinary Sciences, UABC, Mexicali, Baja California 21100, México.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Plascencia
authors.affiliation: Department of Animal Science, University of California, Davis CA95616, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Zinn
keywords: Amino Acid Supplementation; Digestion; Feedlot; Holstein; Performance