Effective use of animal by-products in livestock feeds
Animal by-products (ABPs) are used in livestock diets as they are good source of amino acids (AA), calcium, phosphorus and vitamins (NRC, 2012). Knowledge on feedstuff composition is important for the nutritionist, in order to meet the nutrient requirements of livestock and for the feed manufacturer, to produce nutritionally balanced compound feeds (Gizzi and Givens, 2004). In livestock feed formulation, reliable and up-to-date information is important since data on feedstuff characteristics may be affected by various factors. Both intrinsic (genetics/species, origin, processing, seasonal changes, weather, etc.) and extrinsic (differences in storage, sampling and analytical procedures) factors contribute to nutrient variation and have a significant influence on the nutrient contents of feed ingredient. It is well noted that the variability of ABPs is higher compared to by-products of milling and distilling depending on the sources. To use the ABPs efficiently in formulation of animal diets, this requires a substantial number of samples to be analyzed in order to capture the variability in raw materials. Additional information on AA composition and standardized ileal digestible (SID) AA is necessary in formulating livestock diets as close to their requirements.
Currently, there are published feed tables and databases that can provide the nutrient composition of ABPs. The use of regression equations is another option which provides the fastest and easiest method in estimating the AA content in a raw material based on moisture and crude protein (CP), as an alternative to wet chemical analysis. The wet chemical method is still the first analysis method of choice and is referred to as the "gold standard", however this method is costly and time consuming. The use of Near Infrared Reflectance Spectroscopy (NIR) is the next best alternative to wet chemical analysis to assess the nutritional quality of raw materials like ABPs which will also allow for effective utilization of such ingredients in the formulations. The NIR is considered as the most practical method to analyze large number of samples in a short time. The use of NIR is now accepted worldwide as a rapid and reliable means to predict the concentrations of various nutrients in raw materials and finished feeds. Nutritionists use the information gathered via NIR to update ingredient nutrient matrices almost in real-time. By doing so, nutritionist/feed formulators can adjust for nutrient levels lower than expected in order to avoid issues in animal performance as well as adjusting for nutrient levels higher than expected which can help reduce formulation costs and reduce nitrogen and phosphorus emissions to the environment. This capability is most valuable when dealing with ingredients that are highly variable in their nutrient concentrations. The NIR is an ideal way to analyze ABPs since it can provide information on multiple constituents in one single analysis. It is less expensive and requires minimal or no sample preparation as compared to the conventional methods of analysis. The purpose of this paper is to provide overview of quality of ABPs, with focus on fish meal (FM), meat and bone meal (MBM) and poultry by-product meal (PBPM), analyzed in Southeast Asia (SEA) in 2019 with the use of Evonik AMINONIR® services.
ANIMAL BY-PRODUCTS IN SOUTHEAST ASIA
More than 28,000 ABPs samples were analyzed in 2019 using Evonik's AMINONIR® Advanced services, calibrations for AA and proximate parameters (Figure 1). There was increasing trend in the number of ABPs samples analyzed from 2017 to 2019. This increase is indicative of the increased product availability and competitive pricing, allowing cost effective substitution of other plant protein sources such as soybean meal.
NUTRITIONAL VALUE OF ABPS
In purchasing raw materials for livestock feeds, CP is one of the main nutrients that greatly influences the cost among other parameters like moisture, ash, fiber and fat content. However, CP is not the best indicator of quality as nutritionists need to formulate diets based on digestible AA to meet animal requirement. Figure 2 shows the historical CP and AA contents of FM analyzed in SEA. The average CP content in 2017 to 2018 increased from 60.88 to 61.22 but the values for lysine (Lys), methionine (Met) and tryptophan (Trp) decreased. This clearly indicates that the assumption of linear correlation between CP and AA of similar magnitude is not true and thus the use of linear equations to determine the total AA (TAA) content is not advisable. In order to ascertain the right economic value of the raw material based on quality, continuous evaluation of the nutrient contents of raw materials is important to get optimum performance. The use of NIR allows the analysis of huge number of samples in order to capture the variation in each lot of raw material.
Of the 3 ABPs, FM had the highest average CP content of 60.75 % compared to 48.87 % for MBM and 59.3 % for PBPM (Table 1). FM, aside from having the highest CP content, also contains higher amount of most of the essential AA (EAA) as compared to MBM and PBPM however, the variability as measured by the standard deviation (SD) was highest for FM. The SID AA for swine and poultry was also highest for FM followed by PBPM and MBM.
The average Lys value for FM, MBM and PBPM analyzed in 2019 was 3.97, 2.39 and 2.98 %, respectively. These values were similar to the values reported in the 2018 Asia South Feed Ingredients Report. However, the CV of analyzed FM, MBM and PBPM samples was 16.93, 7.65 and 15.78 %, respectively which showed broad variation in Lys content of mentioned ABPs. Figure 3 shows that the monthly average of Lys for the 3 ABPs varies and follows no specific trend, thus formulating diets based on actual/updated nutrient values is important.
Processing of ABPs typically involves some form of heat and pressure treatment to inactivate microbial contaminants, thus preventing biogenic amines (BAs) production (Bermudez and Firman, 1998). However, heat processing results in increased disulfide formation, and causes a significant portion of proteinbound cysteine (Cys) to be oxidized to cystine. Protein-bound cystine is less digestible than protein-bound cysteine (Miller et al., 2001; Parsons et al., 1992). In addition, heating causes the formation of new (S-S) disulfide cross links and also the rearrangement of existing disulfide bonds during denaturation of the protein. These changes are associated with a reduction in protein and AA digestibility in which cystine is mostly affected (Opstvedt et al., 1984). A deficiency of Cys leads to a change in the requirement for Met, which if unadressed results in a significant decline in feed intake, and as a consequence, impairs growth and feed efficiency, as well as yields alterations in carcass composition. In addition, heat treatment also results in the cross-linking between Lys and reducing sugars thus damaging proteins. This leads to over estimation of the content of Lys analyzed using a standard amino acid analysis because in this way the content of total lysine, both reactive and unreactive, is quantified. Such information on the effect of heat treatment on the AA, Lys and Cys in ABPs is also beneficial when formulating livestock diets.
ABPS AND BIOGENIC AMINES
ABPs commonly used by the animal feed industry which have undergone some degree of spoilage, are generally considered rich sources of BAs (Smith et al., 2000). BAs are important for normal gut development, however, greater concentrations may cause gizzard erosion, mortality and growth depression broilers (Fedderen et al., 2019). Evonik's recent global survey on the BAs analyzed by wet chemistry showed that the BAs level are highly variable which are indicative of the inconsistency in quality or freshness (Table 2). Quantifying the BAs is now possible at Evonik's AMINOLab®, which is an important parameter in evaluating the quality of ABPs.
Phosphorus (P), is the third most expensive nutrient in most livestock diets after energy and AAs (Mavromichalis, 2013). MBM reported the highest average P content of 50,190 mg/kg (5.19 %) followed by FM 27,935 mg/kg (2.79 %) and PBPM 24,671 mg/kg (2.47 %) (Figure 4). However, the variation in P content followed a trend reversal with PBPM reported to have the highest variation of 7,340 mg/kg (7.34 %) followed by FM with 5,921 mg/kg (5.92 %) and MBM with 4,341 mg/kg (4.34 %). Formulating livestock diets using the correct P value can help reduce P waste outputs by meeting the exact nutritional needs which minimizes the feed cost as well. Although P is an inorganic compound, it is present in raw materials bound with organic compounds thus it could be indirectly measured using the NIR.
OPPORTUNITIES FOR FEED COST REDUCTION WITH ACCURATE ANALYSIS
Diet simulations were run to compare the broiler starter diets using different ABPs compared to a corn- soy diet (Table 3). The cost of corn-soy diet formulated without any ABPs was USD 338.36 USD/MT, with the corn price at USD 270/MT and soybean meal at USD 370/MT. A savings of USD 1.28/MT was achieved when MBM at USD 400/MT, was introduced in the formulation. Based on the analyzed nutrient value of ABPs, FM and PBPM are cost effective SBM substitutes at USD 596/MT and USD 526/MT, respectively when SBM is priced at USD 370/MT.
The inclusion of MBM resulted in the slight reduction in soybean meal and corn gluten meal inclusion levels in the diet. This reduction in the inclusion rate of soybean meal can be advantageous when ABPs are available at competitive price. It is important to note that when using ABPs in diet formulations caution should be taken due to the high variability of their nutrient contents.
• The use of NIR technology provides a rapid and reliable means to assess the nutritional quality of feed raw materials including ABPs. Such information would allow the nutritionist to adjust the nutrient matrix of ABPs practically in real-time to take advantage of differences in quality, which can lead to improved animal performance and/or diet cost savings.
• NIR is a reliable tool in capturing the variation that could help to make informed purchasing decisions and support a sustainable livestock production.
• There is broad variation in the nutrient profile of ABPs which need to be assessed on regular basis to ensure their efficient use in livestock feeds.
• Economic value of alternate feed ingredients needs to be evaluated on SID AA profile instead of CP for cost effective feed formulations.
• Aside from raw material variability other factors such as the effect of processing/heat treatment on AA digestibility and availability, and precautions to be taken in the production process to ensure ABPs are free of any undesirable substances (e. g. microbes, biogenic amines etc.) which can affect the health of the livestock.
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Article made possible through the contribution of S.H.M. Ramos, B. Jayaraman, P. Ramesh, M. Ali and Evonik (SEA) Pte Ltd, Singapore