January 22, 2018

Interpretive Summary: Effect of Forage Species and Supplement Type on Growing Beef Heifers Grazing Winter Forage

Review: Effect of forage species and supplement type on growing beef heifers grazing winter forage 

In a paper recently published in the December 2017 edition of the Journal of Animal Science, researchers explored the effects of forage species and supplement type on rumen kinetics and serum metabolites in growing beef heifers grazing winter forage. Results suggest that there may be benefits to using stockpiled warm-season forage, however, a period of compensatory gain may be needed prior to the breeding season.

The feed cost associated with retaining and developing replacement heifers represents one of the largest costs in an operation. This requires researchers to discover and implement strategies that optimize production while maximizing profitability. The current study hypothesizes that extending grazing through the winter using stockpiled cool- or warm-season forages with supplementation may be an economical alternative to feeding harvested feedstuffs. The objective of this study was to determine the effect of stockpiled winter forage type and protein supplementation on volatile fatty acid (VFA) production, serum metabolites, and body weight in yearling beef heifers.

In a two-year study (Jan-Mar, 2014 & Jan-Mar 2015), a research team at the Middle Tennessee Research & Education Center studied 42 spring-born, crossbred Angus heifers. Forage pasture types included endophyte-infected tall fescue (TF), a big bluestem combination (BI), and switch grass; then each pasture was assigned to receive either 1 of 2 isonitrogenous CP treatments: dried distiller's grains with solubles (DDGS) or blood meal and fish meal (BF) resulting in a 3×2 factorial arrangement of treatments. Treatments were initiated in January and terminated in April, and body weights and blood samples were collected every 28 days.

Results show that overall body weight changes were greater for heifers on the TF pastures, specifically within January and February. However, there was no difference in body weight changes between March and April among the forage types. Supplement type did not influence body weight from January to April, but heifers fed the DDGS supplement experienced body weight gain from March to April. Serum metabolites and VFA concentrations did not exhibit interactions between variables studied. Initial results indicate that BF-fed heifers gained more body weight on BI pastures than the DDGS-fed heifers.

Overall, using native warm-season grasses delayed gain in heifers before breeding, however, heifers grazing warm-season native forages had maintained a positive rate of gain by the end of the grazing trial period. Indicating that if stockpiled warm-season forage for winter grazing is utilized for heifer development systems, a compensatory gain period may be needed to make these species a viable option for beef producers in the southeastern United States.

To view the full article, “Effect of forage species and supplement type on rumen kinetics and serum metabolites in growing beef heifers grazing winter forage,” visit www.journalofanimalscience.org.