Matching calving closer to when nutrients that are available from the grazed resource are high can reduce feed costs substantially. In studies at the University of Nebraska, ve experienced a lower rebreeding performance of the first-calf-cows during their second breeding season. Pregnancy rates ranged between 75% and 80% for females bred for their second pregnancy in these heifers. Nebraska Sandhills upland range is dominated by warm-season grasses that decline in energy and protein in late summer and early fall. Evaluation of the forage indicated that the quality in some situations is not sufficient to meet the young females’ nutritional needs during lactation, especially energy and protein needs. We have conducted experiments using supplementation regimes to meet the young lactating females’ nutrient needs that have resulted in acceptable rebreeding performance of these females. Pregnancy rates for the second breeding season for the supplemented females was 95% compared to non-supplemented cows of 79%. When we repeated the experiment, pregnancy rates were not different between the two groups. Quality of the grazed forage was different in experiment 1 compared to experiment 2. In experiment 1, drought occurred early in the growing season which influenced quality during the growing season and we saw a response in pregnancy rate to supplementation. Bottom-line, it is important to evaluate the grazed forage resource, especially prior to the breeding season, for young cows in this management system.

From a nutrient management standpoint, if one studies the nutrient quality change in sandhills range, it appears that late April or early May calving may better fit to further reduce feed inputs and possible supplementation, especially for young females during their second breeding season. By moving the calving time to late April, the cow nutrient requirements shifts and the nutrient composition of the grazed forage better mirrors the nutrient needs of the lactating mature cow and 1st-calver. Data-bases that describe protein and energy content of grazed forages, like the ones developed for the sandhills of Nebraska, are tremendous assets to producers to help them design production systems that fit their operation and have potential to increase profit. In additions, these data-bases aid producers in designing strategic supplementation strategies.