L. Panicke et al., Enzyme activities and milk performance by clusters of growth hormone gene (GH) and beta-casein (beta-cN) in German Holsteins, CZEC J ANIM, 46(5), 2001, pp. 202-208
The examined enzyme activities show the same trend as milk yield. The enzym
e activities for combined aminopeptidases increased nonlinearly to a higher
milk performance. Lower physiological load contributes to better fertility
. The increasing enzyme activity of lysosomal esterase is connected with a
higher ATP need, the protein synthesis increases simultaneously. The geneti
c effects of milk protein genotypes beta -casein(A2A2) are superior to thos
e of beta -casein(A1A1). The effect of days open shows the same trend in mi
lk production and fertility. A high milk performance could be combined with
high fertility on a genetic basis.