Tr. Mackle et al., Effects of branched-chain amino acids and sodium caseinate on milk proteinconcentration and yield from dairy cows, J DAIRY SCI, 82(1), 1999, pp. 161-171
Our study investigated the separate and combined effects of branched-chain
amino acids (AA) and sodium caseinate on milk protein concentration and yie
ld. Four Holstein cows (112 d in milk) were abomasally infused with water,
branched-chain AA (150 g/d), sodium caseinate (600 g/d), or branched-chain
AA plus sodium caseinate (44 and 600 g/d, respectively) according to a 4 x
4 Latin square design with 8-d treatment periods. Cows were fed a dry diet
based on alfalfa hay and concentrates for ad libitum intake. The ration was
formulated to exceed requirements for metabolizable energy and protein usi
ng the Cornell Net Carbohydrate and Protein System. Neither daily dry matte
r intake (24.2 +/- 0.4 kg/d; (X) over bar +/- SEM) nor milk yield (32.9 +/-
; 0.4 kg/d) was affected by any of the infusion treatments. Infusion of bra
nched-chain AA had no effect on any milk production parameters, despite a 5
0% increase in their concentrations. Modest increases in milk protein conce
ntration (0.1%) and milk protein yield (62 g/d) resulted from the infusion
of sodium caseinate or branched-chain AA plus sodium caseinate. True protei
n and whey protein concentrations in milk were also marginally increased by
infusion of sodium caseinate and branched-chain AA plus sodium caseinate,
and infusion of branched-chain AA, sodium caseinate, or both elevated milk
nonprotein N content. Plasma urea N concentrations were elevated by the sod
ium caseinate and branched-chain AA plus sodium caseinate treatments. No tr
eatment effects on other plasma metabolites or hormones were observed. Our
results show no benefit of supplementation with branched-chain AA and only
modest effects of sodium caseinate on milk protein concentration and yield
in well-fed cows.