Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: July 29, 1997
Publication Date: N/A
Technical Abstract: Plants vary diurnally in concentrations of nonstructural carbohydrates (TNC) with highest levels observed in the afternoon. If ruminants prefer forages with higher TNC the preference for hays harvested within the same 24 h period may vary. Harvests were paired with one hay cut at sundown (PM) and another the next morning at dawn (AM). This process was repeated 3 times resulting in 6 hays. The hays were field dried, baled, and chopped prior to feeding. Three experiments were conducted (Exp. 1, sheep; Exp. 2, goats; and Exp. 3, cattle) utilizing six animals. Meals of each hay were offered during an adaptation phase. In the experimental phase, each possible pair of hays (15 pairs) was presented for 2.5 h. Analysis by multidimensional scaling indicated that the animals were basing selection on a single criteria. In all three experiments, preference for PM hays was greater than for AM hays (p<.01) and preference for Hay 5 and 6 was greater than Hays 1, 2, 3, or 4 (p<.01). In Exp. 1, PM hays were preferred by sheep over AM hays in all cases. Goats (Exp. 2) did not distinguish between Hays 5 and 6 but the PM harvest was preferred in Hays 1, 2, 3, and 4 (p<.01). Steers (Exp. 3) did not prefer the PM harvest as strongly in the Hay 5 and 6 comparison as in Hays 1 and 2 or Hays 3 and 4 (p=.02). Shifting hay mowing from early to late in the day was effective in increasing forage preference.