Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2000
Publication Date: N/A
Interpretive Summary: An understanding of how animals graze and what constituents present in the plant cause them to accept or reject a specific portion of the vegetation has both management and economic implications. Our study shows that even among tall fescue cultivars, that are in general very similar, both sheep and goats consistently preferenced for and against several cultivars. Through post ingestive feed-back, animals remembered cultivars they liked and cultivars they didn't like. Preference appeared to be in two dimensions with carbohydrates and fiber constituents having different roles. Animals could consistently detect small differences which means that changes in management strategies, such as time of feeding (grazing), can have important influences on how much animals eat each day. Further, small changes in constituents through breeding programs can also make large changes in animal daily dry matter intake. Both knowledgeable management strategies and small changes in specific constituents, as soluble sugars, can have large economic impacts. These strategies can be realized by the producer without additional input cost making them economically very attractive.
Technical Abstract: Grazing ruminants use both visual cues and taste in selecting their diet. Preference during grazing may not be the same when forage is dried for hay and cut into lengths prior to feeding in confinement. Eight cultivars of tall fescue (Festuca arundinacea Schreb.), previously evaluated for preference while grazed, were harvested three times over a period of two year. The hays were air-dried, baled, and passed through a hydraulic bale processor prior to feeding. Five experiments were conducted. All three harvests were evaluated with sheep and the last two also with goats, using six animals each time. During an adaptation phase, hays were offered alone as meals. In the experimental phase, every possible pair of hays (28 pairs) was presented for a meal. Data were analyzed by multidimensional scaling and by traditional analyses. Preference was significant among cultivars in all experiments. Multidimensional scaling showed that selection was based on two criteria with two dimensions being significant. Sheep preferred KENHY followed by KENTUCKY 31 and STARGRAZER but preferenced against BARCEL. HIMAG, MO-96, and C1 were intermediate and MOZARK was variable. Goats were similar to sheep in preferring KENHY followed by STARGRAZER and selected against MOZARK and BARCEL. KENTUCKY 31, HIMAG, MO-96, and C1 were intermediate. In all five experiments the general association was positive for available carbohydrate fractions and negative for fiber fractions that contribute to cell wall rigidity.