ARS | Publication request: Diurnal Changes in Forage Quality and Their Effects on Animal Preference, Intake, and Performance

Submitted to: California Alfalfa Symposium Proceedings
Publication Type: Proceedings/Symposium
Publication Acceptance Date: November 21, 2005
Publication Date: December 12, 2005
Citation: Mayland, H., Gregorini, P., Mertens, D.R., Taylor, J.B., Burns, J.C., Fisher, D.S., Ciavarella, T., Smith, K., Shewmaker, G., Griggs, T. 2005. Diurnal changes in forage quality and their effects on animal preference, intake, and performance. Proceedings of the 35th California Alfalfa & Forage Symposium, December 12-14, 2005, Visalia, California. p. 223-230.

Technical Abstract: Net photosynthesis, respiration and translocation in growing plants cause a circadian rhythm in forage quality. Concentrations of soluble sugars increase in plants during daylight causing a dilution in ADF and NDF and an increase in RFQ and RFV. Herbivores show a strong preference for afternoon (PM) vs. morning (AM) harvested forage. Cattle, sheep, goats, horses and rabbits are able to distinguish between PM and AM hays that differ by as little as 0.5% soluble sugar. Dairy cows fed total mixed rations containing 50% Idaho grown alfalfa produced 6% more milk when the hay had been cut in the PM vs. cut in the AM. No difference in milk production was measured when cows were fed the PM- and AM-cut Wisconsin hays. Sheep and rabbits have a strong preference for PM vs. AM-cut alfalfa but when not given a choice, they eat the same amount of each hay. During the spring season, cattle in 24 h strip grazing studies in Argentina, gained more weight (2.5 vs. 1.2 lbs./d) when given access to fresh pasture each afternoon (3 pm) compared to those given access each morning (7 am). Extrapolating the benefit of afternoon swathing to 25% of the alfalfa in the western United States has an annual value of nearly $300 million. Continued research is needed to identify conditions where these management strategies would be appropriate.