Inclusion of amino acid profiles and characterizations improve on existing model
During the breakout nutrition session at the American Feed Industry Association’s Liquid Feed Symposium, Adisseo’s Dr. Daniel Luchini addressed the upcoming changes to the Cornell Net Carb and Protein System (CNCPS). Available as a software program and integrated into commercial platforms, the nutrition model is designed to generate site-specific formulations meant to “predict requirements, feed utilization, animal performance and nutrient excretion for dairy and beef cattle using accumulated knowledge about feed composition, digestion and metabolism in supplying nutrients to meet requirements.”
While many are familiar with the system for dairy rations, the ever-evolving system is also well suited to optimize beef cattle rations.
Modified protein and carbohydrate degradation rates
The animal inputs, such as body weight, and feed inputs entered into CNCPS ultimately influence the output of the model. Among the updates to CNCPS, Luchini’s presentation touched on the new fractional schemes for the protein and carbohydrate pools, specifically the degradation rates based on the estimated nutritional value of what is being fed and its impact on microbial yield.
“Before, in the model, if you fed the cow molasses, it loved it and shot our tons of microbial protein,” Luchini says. “I fed rations up to 15 pounds of molasses because it loved microbial output and it was because I had all these unrealistic assumptions that I had to put there to make the model work. Now, the microbial output is more realistic. It dropped by 5 to 10 percent units of the total metabolizable protein in dairy rations. Before, the microbial level was 50 to 60 percent. Now it is around 45 to 52 percent.”
With dairy cows, it is important to know the total microbial protein levels in the rumen because it is the most important protein for lactating cows.
But what about beef cattle rations? Under the new model, the microbial percentage of total metabolizable protein is 50 to 55 percent. While it is known that lysine and methionine are the first limiting amino acids for milk production (histidine being the third), beef cattle also benefit from the diet’s amino acid balancing.
Amino acids in dairy and beef cattle
CNCPS v6.5’s updated amino acid profiles, which are presented on a crude protein basis, and use combined efficiencies of amino acid utilization for maintenance and lactation, allowing the model to more adequately represent the true gram-per-day requirements of essential amino acids.
“There is a specific ratio of lysine to methionine that needs to fixed to optimize milk protein yield and content,” Luchini reports. According to Cornell researchers, the suggested lysine and methionine concentrations for maximal milk protein yield are 7.00 and 2.60 percent of the metabolizable protein, respectively, and 6.77 and 2.85 percent metabolizable protein for lysine and methionine, respectively, to achieve maximal milk protein content (Foskolos et al., 2014).
CNCPS can be used to balance amino acids in beef rations to maximize the animal’s tissue and hot carcass weight.
“Few people are looking to amino acids in beef rations because it’s usually all about the energy, but the amino acids can be used to exploit their potential,” Luchini explains.
Based on a 351-day study of 108 Holstein using CNCPS v6.1, the comparison of two dietary treatments – the control, featuring a standard, urea-based growing-finishing diet; and the other, a two-phase diet feeding a ration to meet metabolizable amino acid requirements from day 1 to 112 using the NRC 2000 level 1 and the urea-based diet from day 113 to 351 – yielded interesting results (Zinn et al. 2007).
The Holstein calves fed the two-phase CNCPS diet presented a higher total body weight (564 vs. 590 kg), a higher hot carcass weight (352 vs. 369 kg) and higher values in the marbling score, fat thickness and ribeye area.
In conclusion, the study’s lead researcher suggests that “receiving and early growing diets should be formulated to provide 2.1 and 7.0 g/kg dietary dry matter of metabolizable methionine and lysine.” Also, Luchini concludes that the new CNCPS model seems more sensitive to estimating lysine deficiencies.
Amino acids profiles shift format
Amino acid feed profiles within CNCPS v6.5 will be based on the current feed libraries of Evonik, Adisseo and NRC 2001. In addition, the updated amino acid profiles will be expressed as a percentage of crude protein rather than the expressed percentage of the buffer insoluble protein as they had been in the older version.
The implementation of the combined efficiency of MP amino acids aims to provide a more consistent approach between amino acid supply and requirements. It should improve the ability of the model to predict limiting amino acids and provide more sensitivity in determining a dietary approach to overcome the limitation (VanAmburgh et al., 2013).
The updated CNCPS v.6.5 is set to be released in late October 2014