Evaluation of Long-Term Reproduction and Lactation Performance of Dairy Heifers Fed Increasing Dietary Concentrations of ReducedFat Distillers Dried Grains in Replacement of Forage During Pubertal Development

South Dakota State University/Jill Anderson

This project is an expansion of existing research that is evaluating growth performance, rumen fermentation, total tract digestion, metabolic profile, and onset of puberty of dairy heifers fed three increasing inclusion levels of reduced-fat dried distillers grains (RF-DDGS) in replacement of forage.

In this expansion, another 12 heifers will be added to the original 36 in the experiment, to increase the statistical strength of the study for collection of long-term data. All heifers will finish the study and cease to be fed the treatment diets at approximately 11 months of age, which is also predicted to be approximately 1 month post-puberty. Post-trial, all the heifers will be returned to the general herd at the South Dakota State University Dairy Research and Training Facility, managed under normal farm protocols, and fed common herd diets. Data will be collected on reproductive performance, such as number of AI services, age at conception, and predicted calving age. Frame size and body weights at approximately 3 weeks prior to predicted calving date and within 48 hours post-parturition will be measured. During the first 100 days of lactation, daily milk weights and milk composition will be monitored to evaluate lactation performance. If it can be demonstrated that long-term reproductive and lactation performance is maintained or enhanced with high levels of RF-DDGS in the growing heifer diet, it will give dairy producers and nutritionists increased confidence in the co-product and its utilization increased.