Understanding the effect of reduced supplementation frequency on performance, digestion and metabolism of stocker cattle.

摘要

Supplements are often fed to stocker cattle on forage-based diets to improve animal performance. Delivery costs can make up a substantial portion of the cost of supplementation, particularly for small producers and those that travel long distances to feed cattle. Reducing supplementation frequency can reduce labor and equipment operation costs and therefore has the potential to increase profit. However, less frequent feeding requires feeding larger quantities of supplement at once and can increase the likelihood of negative associative effects of supplementation on digestion and forage intake and can therefore decrease gains. Additionally, little is understood about the metabolic response of ruminants to large fluxuation in nutrient intake. Therefore, even if microbial digestion is not affected by less frequent supplementation, performance may still be altered. A 50:50 blend of soyhulls and corn gluten feed is widely used by producers to supplement growing cattle. This blend is high in energy but low in non-structural carbohydrates. It also contains a moderate amount of protein, much of which is ruminally degradable. Therefore, reducing the frequency of supplementation of a 50:50 blend of soyhulls and corn gluten feed may not cause negative effects on fiber digestion. The purpose of this research was to determine the effect of reducing supplementation frequency of a soybean hull and corn gluten feed blend on performance, digestion, and concentrations of metabolites and hormonal growth regulators in blood of growing cattle. In Experiment 1, growing steers consuming medium quality tall fescue hay were supplemented either daily (∼1% BW), 3 times a week (∼2.3% BW), or 2 times a week (∼3.6% BW). Hay intake was decreased by reducing supplementation frequency but gains were not affected. As a result, the feed to gain ratio increased slightly with less frequent supplementation. In Experiment 2, six ruminally cannulated beef steers consuming medium quality fescue hay were used in a replicated 3 x 3 Latin square design to determine the effect of supplement frequency (daily at 1% BW or on alternate days at 2% BW) on digestion and ruminal parameters. Reducing supplementation frequency decreased hay intake but did not affect digestibility of the diet. On the day of supplementation molar proportions both of propionate and butyrate in the rumen of steers supplemented on alternate days was increased compared to those supplemented daily. In Experiment 3, growing steers were individually fed medium quality hay and supplemented daily (1% BW) or on alternate days (2% BW). Gains did not differ due to supplementation frequency. However, plasma IGF-1 was greater and insulin tended to be greater in steers supplemented less frequently. The effect of less frequent supplementation on insulin and IGF-1 deserves further examination as it may explain why the steers supplemented less frequently with a soybean hull and corn gluten feed blend appear to be more efficient. When supplementing medium quality hay with a blend of soybean hulls and corn gluten feed, producers can reduce supplementation costs by decreasing supplementation frequency to as little as 2 times a week without negatively affecting gains. Future research should focus on determining the main factors that influence the performance responses to less frequent supplementation so that the response can be predicted when utilizing different supplement and forage combinations.