Lysine (Lys) and methionine (Met) have been identified as the two amino acids (AA) most limiting growth of beef cattle. The objective of this study was to determine the effect of supplementing metabolizable Lys and Met on growth and carcass composition of growing bulls.
One hundred and twenty bulls (333 ± 52 kg; mean ± SD) were randomly allocated to one of two treatments and were fed a basal diet composed of corn grain, distillers grains, grass hay and a mineral/vitamin premix at 56.8, 14.8, 25.2 and 3.2% DM, respectively with no supplemental AA (CON) or the basal diet with supplemental Lys (4.59 g/kg DM of a lipid-encapsulated Lys [AminoShure-L] and Met [1.24 g/kg DM, Metasmart] [L+M]). Using CNCPS V.6.1, estimated concentrations of Lys and Met in metabolizable protein were 5.43% and 1.95% for CON and 6.41% and 2.18% for L+M.
Daily DMI was recorded for each animal using the GrowSafe feeding system. Bulls were weighed on 2 successive days at the start and end of the study. Ultrasound (for carcass quality) was made at the start and end of the study.
1) For average daily gain (ADG) and backfat thickness there was an interaction with the covariate (pretreatment body weight [BW] and backfat thickness, respectively) and, therefore, covariates were treated as categorical variables with two levels (low and high groups).
2) L+M increased BW gain (p < 0.05) and tended to increase DMI (p < 0.15) compared to CON.
3) ADG (kg/d) increased (p < 0.01) in the high BW (1.88 and 1.68) for L+M and CON respectively.
4) There was an increase (17%; p = 0.02) in backfat thickness for the high group of animals on L+M treatment compared to the CON.
5) There were no effects of L+M on longissimus muscle area or intramuscular fat.
Results indicate that supplementing a balanced ratio of the two most limiting AA can improve growth and ADG of growing bulls.
Lysine (Lys) and methionine (Met) have been identified as the two amino acids (AA) most limiting growth of beef cattle. The objective of this study was to determine the effect of supplementing metabolizable Lys and Met on growth and carcass composition of growing bulls. One hundred and twenty bulls (333 ± 52 kg; mean ± SD) were randomly allocated to one of two treatments and fed a basal diet composed of corn grain, distillers grains, grass hay and a mineral/vitamin premix at 56.8, 14.8, 25.2 and 3.2 % DM, respectively with no supplemental AA (CON) or the basal diet with supplemental Lys (4.59 g/kg DM of a lipid-encapsulated Lys [AminoShure-L] and Met [1.24 g/kg DM of the isopropyl ester of 2hydroxy-4-{methylthio}butanoic acid, Metasmart] [L+M]). Using CNCPS V.6.1, estimated concentrations of Lys and Met in metabolizable protein were 5.43% and 1.95% for CON and 6.41% and 2.18% for L+M. The AA products were mixed with ground corn and mixed into the TMR. Daily DMI was recorded for each animal using the GrowSafe feeding system. Bulls were weighed on 2 successive days at the start and end of the study. Ultrasound (for carcass quality) was made at the start and end of the study. Data was analyzed using the PROC Mixed procedure of SAS, and pretreatment measurements were used as a covariate. For average daily gain (ADG) and backfat thickness, there was an interaction with the covariate (pretreatment body weight [BW] and backfat thickness, respectively) and, therefore, covariates were treated as categorical variables with two levels (low and high groups). L+M increased BW gain (p < 0.05) and tended to increase DMI (p < 0.15) compared to CON. ADG (kg/d) increased (p < 0.01) in the high BW (1.88 and 1.68) for L+M and CON, respectively there was an increase (17%; p = 0.02) in backfat thickness for the high group of animals on L+M treatment compared to the CON. There were no effects of L+M on longissimus muscle area or intramuscular fat. Results indicate that supplementing a balanced ratio of the two most limiting AA can improve growth and ADG of growing bulls.
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