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Title: VARIATION IN RUMINANT PREFERENCE FOR SWITCHGRASS HAYS CUT AT EITHER SUNDOWN OR SUNUP

Author
item Fisher, Dwight
item Burns, Joseph
item Mayland, Henry

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2004
Publication Date: 5/27/2005
Citation: Fisher, D.S., Burns, J.C., Mayland, H.F. 2005. Variation in ruminant preference for switchgrass hays cut at either sundown or sunup. Crop Science. 45:1394-1402.

Interpretive Summary: During sunlight hours green plants produce sugar and starch. This process can improve the digestibility and reduce the percent fiber in hay cut in the afternoon. Cattle, sheep, and goats were previously shown to prefer tall fescue and alfalfa hay produced in the Western USA when it was cut in the afternoon. Scientists at the J. Phil Campbell, Sr. Natural Resource Conservation Center in Watkinsville, Georgia cooperated with ARS scientists in Raleigh, North Carolina and Kimberly, Idaho to test the preference of cattle, goats, and sheep for hays made over three years using a native warm season grass (switchgrass) produced in the South. A total of nine experiments were performed. In each experiment, the hays were cut in pairs so each time a cutting was made at sundown another was made the next morning at sunup. Every possible pair of hays was presented for a meal. The animals based hay selection on at least two criteria. The suite of improvements in fiber content, digestibility, and sugars as well as the increased animal preference associated with evening harvested hays observed for alfalfa and fescue hays in the Western USA was difficult to reproduce with switchgrass hay in the Southeastern USA. This difficulty is likely related to the less favorable environment for haymaking as well as the physiology, anatomy, and morphology of switchgrass. Southeastern producers of warm-season grass hays such as bermudagrass may not see as great an increase in hay quality and animal responses as western hay growers when cutting is delayed until evening. However, there was no indication that hay quality would decline with evening cutting.

Technical Abstract: Plants vary diurnally in concentrations of nonstructural carbohydrates and structural carbohydrates. The preference of ruminants for hays harvested within the same 24-h period can vary. To test the utility of this effect in a C4 grass harvested in the humid east, established fields of Kanlow and Alamo Switchgrass (Panicum virgatum L.) were used to produce hays in 1998, 1999, and 2000 near Raleigh, NC. Harvests were paired so that each cutting at sundown (PM) was followed by a cutting the next morning at sunup (AM). We harvested in this manner three times in 1998 to produce 6 Kanlow hays; twice with Kanlow and once with Alamo at 2 levels of nitrogen fertility in 1999 to produce 8 hays; and three times in 2000 to produce 6 Alamo hays. The hays were field-dried, baled, and passed through a hydraulic bale processor. Hays from each year were tested with cattle (Bos taurus), goats (Capra hircus hircus), and sheep (Ovis aries). During an adaptation phase, hays were offered individually. In the experimental phase, all possible pairs of hays were presented. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on multiple criteria. The suite of improvements associated with PM harvested hays in fiber content, digestibility, and nonstructural carbohydrates observed for alfalfa and fescue hays in the Western USA was difficult to reproduce with switchgrass hay in the Southeastern USA. This difficulty is likely related to the less favorable environment for haymaking as well as the physiology, anatomy, and morphology of this C4 grass.