Effects of Rumen-Protected Amino Acids on Ruminant Nitrogen Balance, Plasma Amino Acid Concentrations and Performance

Abstract

A series of trials was conducted to determine the effects of supplemental rumen-protected methionine (RPMet) and lysine (RPLys) on nutrient metabolism and performance. In situ RPMet N disappearance was less than 4% following 48 h of incubation and was not affected (P greater than .05) by diet or resultant ruminal pH differences, indicating that RPMet was well protected from ruminal microbial degradation. Thirty-five Dorset-sired crossbred wether lambs (avg wt 28 kg) fed ground corn-soybean hull diets supplemented with urea were randomly assigned to one of the following treatments: 1) 0% RPMet, 2) .03% RPMet, 3) .06% RPMet, 4) .09% RPMet or 5) .12% RPMet. Dry matter, fiber and N digestibilities and N retention were not affected (P greater than .05) by treatment. Plasma methionine concentration tended to increase linearly (P less than .07) with dietary RPMet level. Six Simmental X Angus steers (avg wt 427 kg) were fed a corn grain-corn silage diet supplemented with urea and five levels of RPMet: 1) 0%, 2) .04%, 3) .08%, 4) .12% and 5) .16%. The plasma methionine concentration increased linearly (P less than .01) with dietary RPMet level. In a steer performance trial, no improvements in feedlot performance resulted due to these RPMet levels (P greater than .05), suggesting that the control diet (0% RPMet) was meeting the methionine requirement of these steers. The effects of RPMet and RPLys on growing and finishing steer feedlot performance also were evaluated. Treatments were 1) urea control, 2) soybean meal positive control, 3) .09% RPMet + .06% RPLys, 4) .12% RPMet + .08% RPLys and 5) .15% RPMet + .10% RPLys. In the growing trial, added RPMet and RPLys did not improve steer feedlot performance. In the finishing trial, only steers fed .09% RPMet + .06% RPLys had higher (P less than .05) gains than those fed the urea control diet. These trials indicate that postruminal methionine and lysine supplies were not limiting feedlot steer performance.

Effect of dietary concentration of metabolizable lysine on finishing cattle performance.

“…The use of ruminally protected amino acids has been investigated as a method of improving performance of growing-finishing beef cattle (Oke et al, 1986;Wright and Loerch, 1988;Hussein and Berger, 1995). However, results of growth studies have been variable.…”

Promotion of cashmere growth by sulfur supplements in cashmere goats

“…Limiting amino acid insufficiency or amino acid imbalance can increase the plasma concentration of urea nitrogen in sheep (Wang & Lu, 1999). Wright & Loerch (1988) found that RPMet supplement decreased the plasma concentration of urea nitrogen, and that the plasma methionine concentration increased linearly with the dietary RPMet level. The results of this study indicated that dietary supplementation with ZnSO 4 or HMBi increased the concentration of plasma total protein and decreased the concentration of plasma urea nitrogen in cashmere goats.…”

Effects of Ruminally Protected Amino Acid-enriched Fatty Acids on Growth Performance and Carcass Characteristics of Fattening Hanwoo Cows

“…Strasia et al (1986) detected no response in growth performance when growing steers were supplemented with as much as 20 g/d of ruminally protected methionine. Some improvements in gain or feed efficiency were detected when ruminally protected lysine and methionine (RPLM) was supplemented (Wright and Loerch, 1988;Veira et al, 1991), but these results demonstrated neither consistent responses to graded levels of supplementation nor large improvements in growth performance. Previous researches also suggested that source of supplemental CP (Merchen and Titgemeyer, 1992) or CP contents of concentrate (Deetz et al, 1985) can influence growth response of growing or fattening cattle to RPLM supplementation.…”

“…However, most protein feeds are a poor source of at least one essential amino acid (Merchen and Titgemeyer, 1992), and methionine and lysine are generally the first limiting amino acids for production of beef cattle (Hussein and Berger, 1995). Supplementation of ruminally protected methionine and lysine improved body weight gain or feed efficiency of growing steers (Wright and Loerch, 1988).…”