Environmental impact of micronutrients in livestock feeding by Jake Piel, Sustainability Manager, Novus International
Agricultural production systems are adapting operations to meet the increasing demand for wholesome and affordable food. Attention has focused on the long-term impact on ecosystems of both crop and animal production. With reference to animal agriculture, concerns have
been expressed about the concentration of minerals in manure and its subsequent effect on soil mineral content and phytotoxicity.
he US Environmental Protection Agency has placed some metals such as copper (Cu), nickel (Ni) and zinc (Zn) on their list of priority pollutants, as they are considered among the most toxic elements in the environment when improperly managed. Trace minerals cannot be degraded through chemical or biological processes, and therefore remain in the soil for long periods of time. The benefits of supplementing copper, zinc and manganese in animal feed are critical to animal health and wellbeing, as well as overall production and performance improvements. For example, pork producers supplement diets with copper for enteric benefits. A swine study has shown injected copper could result in a 19.8 percent increase in weight gain and 16.9 percent improvement in feed conversion. These benefits, along with 9.4 percent improvement in loin muscle weight relative to live body weight, underscore the role of available copper in grow/finish pigs. An
50 | November 2015 - Milling and Grain
important trace mineral for red blood cell health, reproduction and immune function, copper is also a metal co-factor for an enzyme responsible for collagen development and is critical for strengthening tendons, bones, skin and intestines. In addition, without adequate available zinc in poultry diets, young birds may not receive the maximum protective benefit of a vaccination program. Zinc deficient birds are more susceptible to diseases, resulting in increased mortality, poor efficiency and ultimately, economic loss for the producer. Deficiencies can lead to structural defects, as well as compromised growth performance. Because zinc, as well as copper, has low natural bioavailability and absorption in the animal, it must be supplemented to realize the animalâ€™s full performance potential. Many studies have identified both copper and zinc, when used at elevated levels, can have a significant effect on the environment through excretion into the manure. Traditionally, supplemental copper has been offered in inorganic forms as copper sulfate (CuSO4) or tribasic copper chloride (TBCC). Depending on the source of minerals fed, as little as 20 percent of the inorganic copper may actually be utilised by the animal, with the remaining 80 percent excreted in the manure. Producers routinely over-supplement inorganic mineral salts, believing this is the best way to get the maximum benefit of a mineral program. However, this over supplementation does not necessarily optimise animal performance, and in fact the majority of these minerals will be excreted in the faeces. In broilers, for example, it can be calculated that 75 percent of the dietary zinc is wasted in this way. Over time, these minerals can accumulate in the soil and can affect plant growth, crop production and ecosystem integrity. The over exposure of some minerals to plants can reduce photosynthesis, brown the root tips, inhibit growth and ultimately cause death. The microbial population in the soil is also affected by minerals contamination when accumulation has occurred.