The current trend in broiler nutrition toward lower protein diets is driven by several factors, including the aim to improve environmental sustainability, reduce reliance on imported soybean meal (which could lower feed costs), and align with the global move towards more sustainable agricultural practices. This shift highlights the critical need to explore efforts aimed at reducing waste and maximizing the use of industrial by-products to build more resilient production systems. The quest towards optimizing low-protein diets is evidence of how poultry nutrition plays a dynamic and crucial role in the broiler industry, which requires continuous heuristic and epistemological efforts in order to find feasible solutions complying with food security requirements and a more efficient and resilient commercial production. A recent evaluation revealed that the protein reduction in practical diets during the starting period presented a negative impact on performance at the final processing age. On the other hand, maintaining protein levels during the starter phase and then strategically reducing and adjusting the amino acid profile in later phases minimize consequent detrimental effects on performance. There are still pressing questions involving some neglected essential (Phe+Tyr) and non-essential amino acids (Ala, Asp, Glu, Pro, Gly, and Ser) which may play significant roles in practical formulation of low-protein diets. Incorporating a blend of free non-essential amino acids into feeds formulated with 3 percentage point protein reduction, while balancing adequately all ten essential amino acids, has shown to sustain live performance comparable to positive control diets. Considering the impact of supplementary non-essential amino acid on feed cost, it is crucial to design future low-protein trials focusing on the pure effect of each non-essential amino acid on performance and meat yield. A third trial comparing lower-protein diets formulated with either corn or wheat demonstrated that corn-based diets resulted in better performance. Wheat-based diets also lead to reduced Ala levels, which may limit the amount of protein reduction if not taken into consideration during the formulation process, despite presumptions regarding differences in carbohydrate characteristics and utilization.
Article Quarter: FY24 Q4
Recent advancements in swine amino acid nutrition
Swine nutrition has focused the last fifteen years of research on reducing dietary crude protein to reduce dietary costs, improve efficiencies and manage environmental impact of swine production. Through the implementation of feed grade amino acids, research concerning the amino acid requirements of pigs in relation to the first limiting amino acid has expanded through the first six amino acids. Furthermore, complex models such as central composite designs can be used to evaluate the interaction of competitive uptake amino acids such as the branched chain amino acids relative to each other. Research has demonstrated the impact of reducing crude protein on grow-finish pig growth and environmental impact. For example, a recent study by Hagen et al. (2024) demonstrated that reducing crude protein in diets resulted in improved feed efficiency (G:F 0.73 vs 0.71, respectively). Through the utilization of various research models, the determination of exact amino acid requirements have been successful. Multiple amino acids demonstrate that the requirement of feed intake or growth are different than that associated with feed efficiency. For example, feeding a lower level of Trp:Lys resulted in the optimal response in average daily gain, but a higher ratio is needed to maximize gain:feed in various phases of production (Liu et al. 2019). Humphrey et al. (2024) demonstrated that average daily gain was optimized when SID Arg:Lys was 95.65% and feed intake was optimized at 97%. Hagen et al. (2024) demonstrated that providing feed grade amino acids in the water can enhance feed efficiency and the utilization of Arg in the water can assist in helping reduce the impact of enteric challenges. Lastly, understanding how the amino acids interact with one another beyond the relationship to Lys has been of significant impact. Humphrey et al. (2023) demonstrated that the response of Val is independent of Leu and Ile, but when Val is deficient then ADFI can be impacted by high levels of Leu. Furthermore, ADG and G:F can be reduced when feeding higher levels of Leu and Ile and responds to lowering either amino acid independently. However, there were no changes in feed intake when evaluating similar branched chain amino acid ratios in sow lactation diets.
Use of NIR technology to characterize dietary fibre and optimize the development of exogenous carbohydrases
It is well recognized that content and composition of dietary fibre (DF: non-starch polysaccharides (NSP) and lignin) have a profound influence on nutrient digestibility and utilization in poultry as it represents the part of the feed that cannot be digested by endogenous enzymes. DF are influencing the digestibility and utilization of nutrients because of its indigestibility, encapsulation of important nutrients in cell walls and because of its influence on viscosity in the gastrointestinal lumen caused by soluble NSP. Knowing the content and composition of the DF fraction is therefore crucial for obtaining high efficiency. This may be even more important in the future as poultry diets are expected to be based on a larger proportion of DF rich co-products than in the past. Common for the DF rich feedstuffs is that they have a higher and more variable content of DF and consequently lower nutrient digestibility and utilization. Exogenous carbohydrases can be used to overcome some of the negative effects of DF but since the nutritional effects of DF and the effects of carbohydrases are related to its composition it is important with analytical data on these aspects. Analyses of DF are usually done using enzymatic-chemical-gravimetric procedures which provide detailed information on the DF fraction. The latter requires tedious and costly wet chemical methods. Near-infrared reflectance (NIR) spectroscopy, which utilises the interaction between light and matter, however, holds the potential to be used as a tool for measuring content and composition of DF.
Optimizing protein and amino acid nutrition of broilers
Optimization of amino acid nutrition requires a balance between improved live performance and yields coupled with least cost solved formulas. Moreover, with an increase in both the U.S. soybean production and availability of feed grade amino acids, the poultry nutritionist has formulation optimization options. Subsequent assessment of feed ingredient quality at the feed mill or from on-farm bins allows for post validation of target nutrients with test kits, near-infrared spectroscopy, or wet chemistry. Additional tools to assess bird performance and feed quality, e.g., bird circulatory physiological compounds obtained during production, are being developed and implemented so that blood chemistry data can be monitored and acted upon. This work assessed blood chemistry differences in birds from amino acid based-nutritional research conducted at the Arkansas Agriculture Experiment Station from October to December 2023. Birds assessed were in floor pens ranging from 12 to 500 birds per pen, consisted of Cobb 500 and Ross 708 strains, and were fed diets differing in overall amino acid density or variations in the branched-chain amino acids across numerous feeding phases. Cobb 500 male broilers fed corn and soybean meal-based diets during the grower phase with increased Leu/Lys (1.35 to 1.55) from L-Leu or increased Val/Lys (0.76 to 0.82) from L-Val had reduced circulatory P (P = 0.012). However, circulatory ionized Ca was only reduced (P = 0.027) in birds fed increased Val/Lys. Birds fed increased Leu/Lys tended to have reduced plasma Na (P = 0.178). Ross 708 male broilers fed high, compared with moderate amino acid density diets, across phases (average digestible Lys across phases of 1.24 vs 1.18%, respectively) to 42 d tended to have decreased circulatory K (P = 0.168), but increased circulatory Na (P = 0.178). Cobb 500 male broilers were fed varying amino acid density regimes across phases to 45 d of age in corn and soybean meal- based diets. Feeding the highest amino acid density diet resulted in birds having increased circulatory uric acid (UA) (P = 0.066), but deceased circulatory ionized Ca (P = 0.112).
Amino Acids
This chapter has implemented new sections that include sources of amino acids, bioavailability of D-amino acids, amino acid analysis of feedstuffs and physiological fluids, amino acid deficiencies, and empirical methodology to estimate amino acid requirements and ratios in poultry. In addition, classification of amino acids, variation in amino acid requirements, special amino acid relationships, and imbalance, antagonism, and toxicity have been expanded from the 1994 NRC publication.
Energy, lipids, carbohydrates, and dietary fiber
The energy requirements for maintenance and production of poultry species are defined as nitrogen-corrected apparent metabolizable energy, with data based on research conducted primarily with cereals and soybean meals. At the present time, the number of raw materials, most of them with a high fiber content, has increased, a trend that is not expected to change in the near future. Consequently, the role of the different components of ingredients and diets, namely proteins, lipids, and carbohydrates, as supplier of effective energy for maintenance and productivity of the birds, needs further evaluation. In addition, factors such as dietary fiber content, and the physicochemical characteristics, feed form, and particle size of the diets affect the feed intake and the development of the gastrointestinal tract of the birds, and thus, the growth and profile of the existing microbiota. In practice, all these effects are confounded and therefore, new research is needed to better understand and evaluate their effects on chicken health and productivity.
Overview of the NASEM process – Improvements and limitations vs the 1994 NRC
The National Academies of Science’s National Research Council (NRC, now NASEM) Nutrient Requirements reports have periodically been published since 1940s, and are updated occasionally. The 2024 poultry report builds on the 1994 report and those that preceded it. The length, number of peer-reviewed publications, scientific rigor, and transparency of decision processes for specific recommendations have increased with time. The Committee’s recommendations do not include a margin of safety for its nutrient recommendations, they are minimums based on the relevant research. However the report provides many new chapters for adjusting formulated levels to avoid nutrient deficiencies or excesses based on ingredients fed and their digestibility or bio availability. In some cases recommendations could not be given with a high degree of confidence and tentative recommendations based on speculative guidance are provided and are clearly identified in the text and by the fonts used in the tables.
Three specific soybean meal processing environments with different TI levels
Soybean meal samples were obtained from a commercial soybean processing plant that utilized solvent extraction. Sample variation was generated by increasing or decreasing conveyance through the integrated desolventizer/toaster/dryer/cooler unit (DTDC). We characterized the samples as Under processed (187 TPH DTDC), Peak processed (180 TPH DTDC), and Over processed (136 TPH DTDC). Characterization was referenced to 175 TPH conveyance being optimal based on the plant’s equipment manufacturer recommendations. Analyzed crude fat, crude fiber, and moisture were decreased and crude protein increased for Over processed relative to Under processed. Trypsin inhibitor activity generated from two independent laboratories decreased for Over processed (4.5 TIU/mg) relative to Under processed (5.3 TIU/mg). Peak processed samples varied; aligning more with Over processed for crude protein and fiber but aligning more with Under processed for moisture, crude fat, and Trypsin inhibitor activity. Samples were also assayed for KOH, PDI, and Urease by three different laboratories. Data show variation among and within laboratories. The most consistent measure was associated with the Urease assay, demonstrating the lowest pH change for Over processed (0.06), highest pH change for Under processed (0.66), and Peak processed being intermediate (0.17). Broiler starter diets formulated to 85% of Ross 308 crude protein and digestible amino acids were batched and mixed using Under processed, Peak processed, and Over processed soybean meal samples. A positive control (PC) was also manufactured using 100% of Ross 308 nutrient specifications and the Peak processed soybean meal sample. Hubbard x Ross 308 broiler chicks were fed mash diets from 0-21d and performance was measured. Live weight gain (LWG) was increased for PC relative to Under processed (P<0.05) and numerically increased relative to Peak processed and Over processed (P=0.01 and 0.09 respectively). Peak processed LWG was increased compared to Under processed (52g, P<0.05), and similar to Over processed (P=0.95). Over processed had numerically increased LWG relative to Under processed (P=0.06). Feed conversion ratio (FCR) was decreased for PC relative to all other treatments (P<0.05). Under processed had increased FCR by 3pts or more relative to all other treatments (P<0.05). Over processed had numerically lower FCR by 2pts relative to Peak processed (P=0.07).
New quick assay for active trypsin inhibitor
Soybean is an indispensable protein source in the rations of poultry and livestock. However, unprocessed whole soybean cannot be directly utilized in the feed due to the presence of various anti-nutritional compounds which reduce animal weight gain. Among them, trypsin inhibitor is the most dominant antinutritional compound. Rapid and accurate measurement of trypsin inhibitor will be critical for soy processors to assess the quality of soy meal used in the animal feed. Currently, trypsin inhibitor activity is measured utilizing the “standard method” that has been approved by American Oil Chemists Society (Method Ba 12-75) and American Association of Cereal Chemists International (Method 22-40.01). We have modified and improved this “standard method” resulting in the elimination of several time-consuming steps and drastically reducing the assay volume from 10 to 1 ml. The proposed 1 ml assay is easy to perform, uses less reagents, more sensitive and reliable. By employing this rapid assay, we have measured trypsin inhibitor activity of hundreds of soybean meal samples obtained from industry partners. Moreover, our rapid assay can also be carried out in 96-well microplates which will enable high-throughput screening of large number of soy meal samples.
Overview of historic means of tests for soybean meal quality and soybean meal particle size
It is well-known that trypsin inhibitors are an important anti-nutritional factor in soybean meal (SBM). Fortunately, these trypsin inhibitors are inactivated by heating or cooking. However, either under cooking or overcooking can have deleterious effects on the protein quality of SBM. Actual direct measurement of trypsin inhibitor has historically been difficult. Thus, several different indirect methods that are easier to conduct have been developed. One of the first useful assays was the urease test. It was found that heat inactivation of trypsin inhibitor and urease enzyme in SBM were highly correlated. Thus, a rapid urease pH change assay was developed and has been used extensively for more than 75 years. The ideal or most desirable range for urease pH change has evolved and been modified over many years. Eventually, it was generally accepted that the urease pH change is a good basic method of detecting underprocessing of SBM but is of little or no value for assessing overprocessing or excessive heating of SBM. Therefore, a method based on protein solubility in KOH was later developed and evaluated and was shown to be a good method of detecting overprocessing of SBM for poultry. There is, however, considerable interlaboratory variability for the KOH protein solubility assay and recent research is being conducted to better standardize the assay to reduce interlaboratory variation so that results are more repeatable and consistent across labs. Recent research has also been underway to evaluate the KOH assay to better define its critical limits for in vivo amino acid digestibility of commercial SBM since most of the earlier research was conducted using laboratory autoclaved SBM and also did not determine amino acid digestibility. There has been considerable recent work and advances for laboratory assays to analyze trypsin inhibitors in SBM. For example, a new official AOCS method was established in 2020 and a new rapid and cost-effective method has been recently developed.
