S.C.
Loerch1, G.D. Lowe, and D.D. Clevenger
The Ohio State University Department of Animal Sciences
Abstract
Harvested forages are frequently the most expensive component of sheep diets. Alfalfa is frequently priced at greater than $100/ton. On the other hand, corn grain and soybean hulls are often priced at less than $80/ton, despite the fact that these two feeds contain substantially more energy than alfalfa. As a result, inclusion of corn or soyhulls as a replacement for forages in lactating ewe diets may reduce feed costs without compromising performance. The objective of this trial was to determine the efficacy of pelleted soybean hulls vs whole shelled corn as a supplement in forage-based lactating ewe diets. Forty-eight ewes rearing twins and 12 ewes rearing singles were used in a completely randomized experiment with a 2 x 2 factorial arrangement of treatments. Main effects were source of energy supplement (corn versus soybean hulls) and level of energy supplement (1.5 versus 3.0 lb/ewe/day). Performance of ewes and lambs was measured. Results indicated that soybean hulls and corn can be used successfully as energy supplements in alfalfa based lactation diets. Associative effects of source of energy were not measurable. In formulating lactation rations, the source of energy is not of importance as long as energy intake is sufficient to meet the calorie requirements of the animal.
Introduction
Harvested forages are frequently the most expensive component of sheep diets. Alfalfa is frequently priced at greater than $100/ton. On the other hand, corn grain and soybean hulls are often priced at less than $80/ton, despite the fact that these two feeds contain substantially more energy than alfalfa. As a result, inclusion of corn or soybean hulls as a replacement for forages in lactating ewe diets may reduce feed costs without compromising performance. Although the metabolizable energy value of corn is listed as being 50% greater than that of soybean hulls (NRC, 1985), in practice this may not be the case. Most of the metabolizable calories from corn come from starch. Fermentation of starch lowers rumen pH and inhibits fiber digestion. Thus, when corn is fed in combination with forage, negative associative effects on digestion can occur. Soybean hulls do not contain starch. The calories in soybean hulls are derived from the fermentation of the high quality, readily digestible fiber. While corn starch may depress fermentation of dietary fiber, soybean hulls actually enhance fiber fermentation. In this case, actual energy value of the diet may be greater than what would be predicted from book values. This phenomenon is called a "positive associative effect". The substitution value of soybean hulls for corn in ewe lactation diets has not been previously determined. Because lactating ewes are typically fed forages, the impact of the source of supplemental energy on associative effects of digestion may be important. Because forages are expensive, reducing forage intake may be a benefit. These aspects of source of supplemental energy on lactating ewe performance have not been investigated previously. The objective of this trial was to determine the efficacy of pelleted soybean hulls vs. whole shelled corn as a supplement in forage-based lactating ewe diets.