Insta-Pro: How to reduce antibiotics usage in agriculture
Growth-promoting antibiotics have been used in commercial animal production for decades. Unlike typical applications of antibiotics, which are used to treat a bacterial disease outbreak, growth-promoting antibiotics are included in dietary formulations at low levels all the time. Research long ago showed that this practice improved body weight gain beyond what could be explained by differences in nutrition (Ewing, 1963) and it soon become an industry-wide practice of commercial animal production, especially for broilers.
While the widespread use of growth-promoting antibiotics accomplished many things, and probably did so by way of several mechanisms of action (Dibner and Richards, 2005), without question one of the most important results from a commercial perspective was to promote standardization. For example, the use of growth-promoting antibiotics has been shown to reduce microbial species diversity and total numbers of intestinal bacteria (Collier et al., 2003), as well as cause morphological changes in the intestine associated with improved broiler performance (Miles et al., 2006).
Using data from the Miles et al. (2006) study, the benefits on reducing uncertainty in broiler production are apparent. I calculated the amount of variation in body weight for broilers fed a commercial-type diet, and the results are shown in Figure 1.
Figure 1. Both male and female broilers exhibited reduced body weight variation when growth-promoting antibiotics were used after 5 weeks of feeding a commercial-type diet.
At the same time, birds fed growth-promoting antibiotics were heavier than those on the antibiotic-free treatment, and this is shown in Figure 2.
Figure 2. Broilers, in particular females, exhibited greater live weights when growth-promoting antibiotics were used after 5 weeks of feeding a commercial-type diet.
Therefore, as consumers continue to demand, and food companies continue to comply with, reduced or antibiotic-free meat production, the amount of variation and uncertainty will increase. As this happens, any potential problems from an animal nutrition perspective will become magnified - it is likely that growth-promoting antibiotics have been minimizing deficiencies in nutrition programs.
There are two main areas of focus for mitigating these risks as antibiotic-free production becomes standard - quality control programs to include animal research, and the use of high-quality ingredients in diet formulations.
Every ingredient producer and feed mill should have a quality control program, and it should center on an incoming raw materials testing program. Every raw material and ready-to-use ingredient must be inspected, sampled, and tested before acceptance into your facility. Often, this includes a range of assessments, from a simple visual inspection to verify information on packaging, as well as material color and particle size, to analyzing for key nutrients, such as moisture, protein, fat, and fiber using near infrared (NIR) technology (Albin, 2016).
While all of these approaches are important for a successful quality control program, for a complete animal nutrition feeding program, feeding trials and digestibility experiments must be conducted periodically. Ingredients that are assumed to be commoditized will often exhibit variation. For example, samples of solvent-extracted soybean meal displayed substantial variation in digestibility of economically-important amino acids as shown in Figure 3.
Figure 3. True digestibilities (%) of lysine and methionine in samples of solvent-extracted soybean meal determined with cecectomized broilers (Personal communication, Dr. Carl Parsons, University of Illinois).
This is very important because many animal diets are formulated on a digestible basis. So, assuming th at the total lysine content of solvent-extracted soybean meal is 2.8%, the amount of digestible lysine in this material would range from 2.31% to 2.52%. A decline of 0.21% lysine in a formulation could easily result in poorer growth performance in broilers. At the same time, the relationships between key nutrients as one varies is important. Also shown in Figure 3 is that as lysine digestibilities rise and fall in samples, digestibilities of methionine follow a somewhat similar pattern. So, as the balance of these key nutrients to each other, and other important parameters (i.e., metabolizable energy), is extremely important for consistent performance results, knowledge of these relationships is a requirement.
So, the use of quality control programs, with animal research included, should lead to higher-quality ingredients and less variable performance without growth-promoting antibiotics.
"Higher-quality ingredients" can mean many things, but in the context of this topic, refers to ingredients that can repeatedly and consistently be produced to higher standards than others. For example, dry extruded soy meal can be properly processed to generate predictable animal performance. As shown in Figure 4, increasing processing temperature at the extruder reliably improved metabolizable energy content in broilers.
Figure 4. True metabolizable energy (kcal/kg DM) was increased with dry extruder processing temperature in samples of extruded soy meal fed to broilers (Zhang et al., 1993).
Likewise, increasing processing temperature at the extruder reliably improved true lysine digestibility in broilers, which is shown in Figure 5.
Figure 5. True lysine digestibility (%) was increased with dry extruder processing temperature in samples of extruded soy meal fed to broilers (Zhang et al., 1993).
Having predictable ingredients such as this is even more important when they can be used to replace another ingredient and result in superior performance. For example, dry extruded soy meal has been shown to be capable of completely replacing solvent-extracted soybean meal and improving broiler growth performance (Subuh et al., 2002).
In conclusion, growth-promoting antibiotics were used for decades in animal production, helped to increase uniformity, and provided predictable results. Now, as they are being phase out of use, uncertainty will result, and this will put pressure on animal nutrition programs. The use of quality control programs and higher-quality ingredients will help with these challenges. This is especially important as alternatives to antibiotics, such as probiotics and prebiotics, have similar mechanisms of action, but may not result in improved growth performance (Sims et al., 2010).
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Article made possible through the contribution of Insta-Pro