Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/7/2004
Publication Date: 1/20/2005
Citation: Burns, J.C., Mayland, H.F., Fisher, D.S. 2005. Dry matter intake and digestion of alfalfa harvested at sunset and sunrise.. Journal of Animal Science. 83:262-270. Interpretive Summary: Previous preference trials with tall fescue and alfalfa have shown that steers, sheep, and goats consistently preferred hays that were harvested in the PM (about 7:00) vs hays that were harvested in the AM (about 6:30). Compositional data from the hays showed that soluble carbohydrate concentrations were higher in the PM compared with the AM hays and may be the key for greater preference. Although preference for PM hay is of interest, the question remains if it is of any importance in altering animal daily responses. This experiment was conducted to determine if previous determined preference for PM-harvested alfalfa would alter its dry matter intake and digestion when fed to steers, sheep, and goats. If dry matter intake and/or dry matter digestion would increase animal performance from hay harvested in the PM, then the management strategy of harvesting forage for storage in late afternoon would have economic benefits without additional harvesting and storage cost. Results showed that goats consumed more PM forage and digested it better. This should result in higher daily performance. Sheep consumed the PM and AM forage similarly, but digested the PM hay better, and one would expect better digestion about 75% of the time. Steers consumed more of the PM hays but digested the PM and AM hays similarly. In general, goats and steers fed PM hays would be expected to show higher daily gains compared with animals fed AM hays. This management strategy warrants further evaluation over a larger number of animals.
Technical Abstract: The preference exhibited by animals in selecting one feed over another becomes important only if the preferred diet is consumed daily in larger quantities, digested better, or both. Six alfalfa (Medicago sativa L.) hays, previously found to differ in preference, representing three paired harvests so that each time a cutting was made at sundown (PM) another was made the next morning at sunup (AM) were evaluated for DMI and DM digestibility. The hays were field-cured, baled, and chopped prior to evaluation for intake and digestibility separately by sheep (Ovis aries), goats (Capra hirous hircus), and cattle (Bos taurus). Goats were superior in detecting a difference in nutritive value between the paired harvests as reflected in higher DMI (2.97 vs 2.83 kg 100-1 kg BW) and digestion (0.710 vs 0.696) when fed the PM cuts. Steers also showed higher DMI from PM-cut hays (2.90 vs 2.62 kg 100-1 kg BW) but digested the PM and AM hays similarly (mean = 0.661). Sheep detected no difference between the PM and AM hays and consumed (mean = 2.52 kg 100-1 kg BW) and digested (mean = 0.681) them similarly with only the digestion coefficients approaching significance. The digestible DMI from the PM-cut hays compared with the AM-cut hays averaged 7% greater for goats and 11% greater for cattle and should increase animal production. Goats and sheep appeared to be more selective during the intake and digestion trials than were cattle. Intake and digestion responses were correlated with short-term intake and multi-dimensional scaling coordinates for dimensions 1 and 2 from a previous preference trial. The subtle differences in nutritive value between PM- and AM-cut hays were detected by goats and cattle. Employing a management strategy to take advantage of diurnal variation offers potential to improve forage quality at no economic disadvantage.