Animal Science Department


First Advisor

J. Travis Mulliniks

Second Advisor

James C. MacDonald

Date of this Version



King, T. M. 2020. Influence of strategic supplementation and genetic potential for milk yield on forage digestibility, amino acid utilization, and livestock production. PhD Diss., University of Nebraska-Lincoln.


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Animal Science, Under the Supervision of Professors J. Travis Mulliniks & James C. MacDonald. Lincoln, Nebraska: August, 2020

Copyright 2020 Tasha M. King


When consuming low-quality forages or at times when nutrient demands are high, ruminants may be unable to meet these requirements resulting in a state of negative energy balance. With feed costs contributing a large portion of production costs, providing dietary nutrients to maintain energy balance must be done so strategically. Additionally, producers must ensure consistent reproductive performance and offspring weaned to maintain a successful livestock enterprise. The objective of these studies was to evaluate the effect of glucogenic precursor supplementation and milk yield on forage digestibility, amino acid utilization, and livestock production. In experiment 1, a metabolism study was conducted on wethers receiving supplementation treatments with increasing levels of glucogenic precursors. Supplementation treatments providing 40 and 70 g of glucogenic potential (GP) resulted in greater OM digestibility (P ≤ 0.01). Serum urea nitrogen (SUN) and circulating amino acid concentrations were also increased (P < 0.01) in the supplementation treatment providing 40 and 70 g of GP. Experiment 2 was conducted at the Gudmundsen Sandhills Laboratory (GSL) providing postpartum protein with and without calcium propionate to 2- and 3-yo March calving cows. Pregnancy rate and calf pre-weaning performance were not influenced (P ≥ 0.35) by supplementation treatments of dam. Inclusion of calcium propionate tended (P = 0.07) to decrease circulating serum β-hydroxybutyrate concentrations. In Experiment 3, the impact of genetic potential for milk yield on cow reproductive and calf performance was evaluated utilizing data collected from March calving cows at GSL from 2000 – 2018. Milk yield was estimated 4 times throughout the lactation period utilizing the weigh-suckle-weigh technique. Pregnancy rate and subsequent calf birth date were not influenced (P ≥ 0.43) by level of milk production. Increasing dam milk production resulted in greater (P < 0.01) calf pre-weaning growth. Heavier calves at weaning maintained the weight advantage through slaughter (P < 0.01). In conclusion, providing increasing levels of protein can increase digestibility and circulating amino acid concentrations. Additionally, GP supplementation tended to decrease ketone production suggesting improved energy metabolism. Increased milk production in the current study did not negatively impact reproductive performance and produced heavier calves at weaning.

Advisors: J. Travis Mulliniks and James C. MacDonald