PERFORMANCE OF HOLSTEIN HEIFERS FED 100-PERCENT OR MORE OF NATIONAL-RESEARCH-COUNCIL REQUIREMENTS

In trial 1, growth and body condition scores were compared among Holstein heifers from 3 to 6 mo of age that were fed amounts estimated to provide 100% (normal) or 115% (enhanced) of NRC recommendations for CP, metabolizable energy, Ca, P, and vitamins A and D for large heifers gaining 700 g/d. Within each group, half of the heifers were fed control soybean meal as supplemental protein source, and the other half were fed extruded soybean meal. No significant interactions occurred between nutrient amount and type of soybean meal fed, nor were there differences between growth of heifers fed the two types of soybean meal. Actual intakes were 107, 108, 125, and 124% of requirements for normal control, normal extruded, enhanced control, and enhanced extruded, respectively. Heifers on the higher nutrient concentration gained more BW and had greater increases in height, body length, and heart girth but were not over-conditioned. In trial 2, the same heifers were used from 6 to 24 mo of age; those heifers previously on the lower intake were fed a diet containing 100% of nutrients, and those previously on high intake were fed 115% of nutrients. Heifers fed the enhanced diet had greater increments in BW, length, and heart girth gain from 6 to 24 mo of age without excessive fattening and were 7 wk younger at first service and conception than those fed the normal diet. Feeding 124% of requirements from 3 to 6 mo and 115% from 6 to 24 mo of age produced heifers with greater skeletal development and BW without excessive fattening and with potential for earlier calving.