Effect of plane of nutrition before and after 200 kilograms of body weight on mammary development of prepubertal Holstein heifers

Twenty Holstein heifer calves at 138 d of age and 118 kg of BW were assigned randomly to one of four treatments in a factorial design. Heifers were fed for low (0.7 kg/d) or high (>1.0 kg/d) gain during two periods. Period 1 was from start to 200 kg of BW, and period 2 was from 200 kg of BW to slaughter, which occurred in the middle of the luteal phase following the third estrus. Calves on the high plane of nutrition during period 2 were heavier at the end of trial and gained more BW between puberty and the end of trial. Those calves also had heavier mammary glands, which had more fat and dry fat-free tissue. Heifers that had been raised on the low plane of nutrition throughout the trial had greater concentrations of DNA and RNA but did not have greater protein in the dry fat-free tissue. Low plane of nutrition during either period increased DNA and RNA concentration in the dry fat-free tissue. Total mass of DNA and RNA did not differ among treatments. Protein mass was increased by the high plane of nutrition during period 2. This study indicated that dietary manipulation affects mammary dry fat-free tissue, protein, and adipose mass in the period up to and including puberty.