Wool growth and plasma amino acid responses of N.Z. romney sheep to formalin-treated casein and methionine supplements

Lactic casein was treated with formalin in an attempt to protect the protein against ruminal degradation. Sheep received diets supplemented with 100 g/day of treated casein. Wool growth and the level of free amino acids in the plasma were compared with those of sheep receiving no supplement or untreated casein. A fourth group of sheep received a supplement of 1 g/day of methionine hydroxy analogue (MHA) mixed with 5 g of casein, the mixture being formalin treated after blending. Substantial wool growth increases from midside areas resulted from both the formalin-treated and the untreated casein supplements. Significant differences occurred in the levels of free citrulline, valine, leucine, histidine, proline, and ɛ-N-methyl lysine in the plasma. With each of these amino acids the untreated-casein supplemented sheep showed a small increase and the treated-casein group a larger increase when compared with the control group. No change in either wool growth or free amino acids resulted from the MHA supplement.