Brady Campbell, Program Coordinator, OSU Sheep Team
How does corn processing and fiber source affect feedlot lamb performance, diet digestibility, nitrogen metabolism?
(Image source: Maine Organic Farmers and Gardeners Association)
Behaviorally, sheep and cattle are very different, especially in the way they eat. Sheep are more selective in their eating pattern and spend more time physically chewing and breaking down their feed than cattle do.
Regardless of the animal we are feeding, it is common practice in the livestock feed industry to process the grains fed to our animals. An issue with feeding processed grain is that due to an increase in surface area, the starches in grain become more readily available for the animal to digest. As a result, an increase in digestion may lead to metabolic issues such as acidosis in our ruminant species.
Therefore, a question of interest that arises is can sheep be fed unprocessed grains without sacrificing lamb performance to save money and decrease the likelihood of acidosis? Also, how does the incorporation of different dietary fiber sources affect lamb performance when fed processed or unprocessed grains?
To address these questions, two studies were performed. The first study compared whole shelled corn (WSC) to ground and pelleted corn (GC) and compared the effects of pelleted supplemental fiber sources (no fiber as the control (C), soybean hulls (SBH), and peanut hulls (PH)) on lamb performance. From a performance standpoint, WSC diets showed an increase in average daily gain (ADG) when compared to GC diets. Lambs fed a diet that consisted of WSC and no supplemental fiber had a lower ADG when compared to WSC diets with SBH and PH supplemental fiber. Lambs fed diets that were supplemented with SBH or PH fiber had an increase in dry matter intake (DMI) and ADG when compared to diets with no supplemental fiber. Lambs fed diets that were supplemented with PH fiber spent fewer days in the feedlot to reach market weight when compared to lambs fed diets with no supplemental fiber. When looking at carcass characteristics, lambs fed GC based diets had more carcass fat at the 12th rib when compared to WSC fed lambs.
In the second study, the same diet combinations as outlined above where used to compare digestibility and nitrogen metabolism of each diet. From a digestibility standpoint, lambs fed WSC diets exhibited a greater overall digestibility of the ration when compared to GC diets. Lambs fed diets that were supplemented with PH fiber had a decrease in digestibility when compared to diets with SBH supplemental fiber and no supplemental fiber. From a nutrient management perspective, lambs fed WSC diets had a greater nitrogen intake compared to GC fed lambs. Interestingly, WSC fed lambs demonstrated greater urinary nitrogen excretion when compared to GC fed lambs, however, GC fed lambs showed greater fecal nitrogen excretion when compared to WSC fed lambs. No differences were seen in nitrogen metabolism when comparing fiber supplementations.
In conclusion, results from these studies show that processing corn fed to sheep may not increase lamb performance. These studies support that feeding unprocessed grains to sheep may be beneficial as this can decrease the need for mechanical processing and may reduce the cost of feedstuffs. The inclusion of fiber, regardless of source, can improve ADG even if the fiber source is provided in a pellet and small in particle size. Overall, WSC corn diets can save money, improve lamb performance, and improve nutrient and feed utilization.
Hejazi, S., F. L. Fluharty, J. E. Perley, S. C. Loerch, and G. D. Lowe. 1999. Effects of corn processing and dietary fiber source on feedlot performance, visceral organ weight, diet digestibility, and nitrogen metabolism in lambs. J. Anim. Sci. 77: 507-515.