Nutrition
Nutrition Articles
Looking at Protein Efficiency in Beef Animals
The enduring value of a beef cow is the ability to utilize forages of various quality for meat production. As a domesticated animal the farmer controls the intake and sets rations to meet the nutrient requirements. These ingredients contain two main categories which are energy and protein. Typically, we overfeed nitrogen in an effort to meet energy needs. Protein is further divided into Rumen Degradable Protein (RDP) and Rumen Undegradable Protein (RUP). Both energy and protein are expensive and so we are always engaged in balancing the ration to meet needs but also keep the cost as low as possible.
Efficiency in cattle, of utilization of Nitrogen is about 14% retention compared to 24% retention for dairy cattle.1 Rumen microbes attack and deconstruct RDP into ammonia, peptides and amino acids which are then reconstructed into more microbes. Rumen microbial populations then pass into the small intestine and serve as sources for amino acids and peptides for the animal’s digestive processes. In addition to this is added RUP which serves as additional amino acids once it passes through the rumen and is broken down in the small intestine. Excess nitrogen can enter the blood stream through the rumen wall or through absorption from the small intestine. It travels to the Liver where it is converted to urea and recycled through the saliva where it could be used if needed. Excess is excreted in the urine. This excretion constitutes inefficiency and nutritionists strive to minimize nitrogen loss.
Improvements in efficiency prevent lost performance from being too high or too low in energy and protein. The first step is to formulate a ration for RDP that is not in excess of the animals’ needs. Rations that are too high in RDP suppress synthesis of rumen microbes. Next, match dietary energy level to the RDP level then include RUP sufficient to match the needed level. Most ration balancing programs will do this automatically using a preprogrammed ratio of RUP:RDP. Historically a ratio of RUP:RDP of 30:70 was used but current research is showing better growth rates using a ratio of 45:55.3 In general, rations that are 16% CP or greater are considered too high in protein and below 12% CP could be too low for mid gestation beef cows.2 Finally begin moving the ration RUP:RDP ratio closer to 45:55 and monitor results. This would be a step towards efficiency and lower cost production of finished animals.
Beef cows given better RUP:RDP ratios which are closer to 45:55 also showed an improvement in performance being passed on to their offspring. Calves from cows using this ratio had more muscle cells than calves using the historical ratio. The ability to deliver high quality rations is greatly improved when a Highline® mixer is used which gives a low coefficient of variance ensuring homogenous blends.
1. Hristov AH, Hanigan M, Cole A, et al. Review: ammonia emissions from dairy Farms and beef feedlots. Canadian Journal of Animal Science 2011 V91 Pp 1-35.
2. Veterinary World Vol.14/March-2021/13.pdf Effects of rumen-degradable-to-undegradable protein ratio in ruminant diet on in vitro digestibility, rumen fermentation, and microbial protein synthesis, Ezi Masdia Putri et al, Hermon Department of Animal Nutrition, Faculty of Animal Science Andalas University, Kampus Limau Manis, Padang, West Sumatera, Indonesia.
3. Effects of Dietary rumen undegradable protein:rumen degradable protein ratio on nitrogen metabolism in Hanwoo steers, Sang Yoeb Kim et al, 2025 Animal Bioscience V38 No. 6:1182-1193 June 2025.