Opportunities to enhance performance and efficiency through nutrient synchrony in concentrate-fed ruminants

Authors: Cole, Noel; Todd, Richard

Submitted to: Journal of Animal Science Supplement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2007
Publication Date: 4/1/2008
Citation: Cole, N.A., Todd, R.W. 2008. Opportunities to enhance performance and efficiency through nutrient synchrony in concentrate-fed ruminants. Journal of Animal Science Electronic Supplement. 86(E. Suppl.):E318-E333. Available: http://jas.fass.org/cgi/content/full/86/14_suppl/E318.

Interpretive Summary: In ruminant animals such as cattle, the digestion of dietary proteins and carbohydrates begins via anaerobic fermentation by bacteria, protozoa, and fungi present in the first stomach compartments. It has been proposed that for optimal digestion and animal performance the digestion of the protein and carbohydrate fractions need to be synchronized. However, attempts to synchronize the fermentation of dietary carbohydrates and crude protein (CP) have been met with mixed results. The limited data with high-concentrate diets suggest that either ruminal synchrony is not important or that physiological mechanisms offset a lack of synchrony. Ruminants have the unique capacity to recycle nitrogen from the lower gut to the rumen, and visa-versa. Recent studies have attempted to increase nitrogen recycling via synchronizing the supply of nutrients in one segment of the gut with those in another segment: i.e. by oscillating the dietary protein content. In some studies with corn-based diets and oil-seed based natural protein supplements, nitrogen retention and animal performance has been greater in lambs or steers fed oscillating CP concentrations (at 48-h intervals) than in animals fed a constant CP percentage however results are less favorable with high roughage diets. Nutrient intakes also need to be synchronized with the animals’ nutrient requirements. Because protein requirements decrease as animals mature, one method to possibly improve nitrogen utilization is to decrease dietary protein concentrations as animals grow: referred to as phase-feeding. Although results of studies with dry-rolled corn-based diets indicate that phase feeding has no adverse effects on animal performance, results of studies using steam-flaked corn-based diets are less consistent, possibly due to differences in the protein requirements and aggressiveness of the implant program used. In conclusion, ruminal nutrient synchrony is theoretically a sound principle; however, it seems that physiological adaptations may mitigate effects of asynchrony. Thus, methodologies that increase nitrogen recycling and/or increase the utilization of recycled nitrogen may benefit animal performance and the environment.

Technical Abstract: Synchronization of the ruminal degradation of carbohydrates and crude protein (CP) is projected to increase ruminal microbial protein synthesis and improve nitrogen (N) use efficiency. Attempts to synchronize the fermentation of dietary carbohydrates and CP have been met with mixed results, suggesting that either ruminal nutrient synchrony is not important or that N recycling to the rumen offsets lack of synchrony. Nitrogen recycling to the rumen is controlled primarily by the concentration of urea in the blood, ammonia in the gut, and the availability of fermentable energy in the gut. We hypothesized that N utilization could be improved by synchronizing the supply of nutrients in one segment of the gut with those in another segment (i.e., synchronize a ruminal N deficiency with a lower gut N excess, etc.) via oscillating the dietary CP between deficient and adequate concentrations. With corn-based diets and oil-seed based natural protein supplements, N retention has been greater in lambs or steers fed oscillating CP concentrations (at 48-h intervals) than in animals fed a constant CP percentage. Effects of oscillating CP on cattle performance have been variable and may depend upon the fermentability of the carbohydrate source (e.g., forage vs. grain, grain processing). Studies with sheep noted that net portal uptake of urea was greater in lambs fed oscillating CP than in lambs fed constant CP concentrations. Nutrient intakes also need to be synchronized with the animals' requirements. One method to adjust nutrient intake with requirements is via phase- feeding. Results of studies with dry-rolled corn-based diets indicate that dietary CP concentrations can be decreased late in the feeding period with no adverse effects on animal performance; however, results of studies using steam-flaked corn-based diets are less consistent, possibly due to differences in the aggressiveness of the implant program used. In conclusion, ruminal nutrient synchrony is theoretically a sound principle; however, it seems that N recycling may mitigate effects of asynchrony. Thus, methodologies that increase N recycling and/or increase the utilization of recycled N may benefit animal performance and the environment.