For decades, the global swine industry fed low levels of certain antibiotics to pigs to maintain gut health and improve growth. However, concerns about antibiotic resistance in humans and antibiotic use in animals have resulted in tightened regulations, which have minimized or altogether banned the use of many antibiotics except with a veterinarian's supervision.
Stress and disease continue to play havoc with pig health, especially weaned pigs struggling with a new environment, pen mates and feed source. Without the use of antibiotics in diets, the industry is seeking new ways to improve young pig growth. While the importance of mineral nutrition is widely recognized, growing evidence suggests that trace mineral requirements in piglets are not consistently met by feeding inorganic forms of these minerals. Therefore, studies investigating the impact of organic trace minerals on animal immunity are being considered more closely by nutritionists and producers as a means to maximize pig health and growth.
Mineral's Role in Pig Health
Essential trace minerals such as zinc, copper and manganese play a wide variety of biological and physiological roles in piglet health and development. These minerals take part in immune function, antioxidant defense and bone and tissue development. Providing a more bioavailable source of organic trace minerals can exert a variety of positive effects, including improved immune responses, reduced oxidative stress and enhanced bone and tissue development. And, the amount of trace minerals can be met at lower rates in the diet, resulting in reduced excretion into the environment.
Zinc is essential for pig health and development. In the form of zinc finger proteins, it is involved in the regulation of DNA transcription which controls the differentiation of many cell types, including T-lymphocytes. Hundreds of enzymes related to growth and health in the pig require zinc for their normal structure and function, such as the carboxypeptidases and aminopeptidasess which are key players in protein digestion, and superoxide dismutases which plays a key role in oxidative balance and overall health. Pigs deficient in zinc show poor growth, decreased feed intake and impaired immune system.
Copper is necessary to allow red blood cells to form normally, and deficiencies can lead to anemia, which weakens the animal and predisposes to disease. Copper is also important for health. If it is removed from creep diets, piglets can experience diarrhea, bacterial enteritis and poor growth, which has been associated with the rapid multiplication of pathogenic bacteria in the gut.
Manganese is important in enzyme production and the development of bone and cartilage. Manganese is required by enzymes such as pyruvate carboxylase, which is essential in energy metabolism, and superoxide dismutase, which supports oxidative balance and health. Manganese is also required for normal reproductive function. Deficiencies are generally associated with lameness, irregular oestrus, delayed sexual maturity and weak pigs at birth.
One of the systems most responsive to mineral status is the immune system. Studies indicate that feeding a mineral-deficient diet can result in reduced weight gain and a more immune-challenged piglet. One study showed that diseases are more detrimental in mineral-deficient animals, and the feeding of organic trace minerals provided better performance and mineral status following a disease challenge.
MINTREX Trials Show Improved Immune Response
In a study, replacement gilts were fed diets supplemented with zinc, copper and manganese, either as inorganic trace minerals or an equal mixture of inorganic trace minerals and methionine analog chelated minerals fed as metal methionine hydroxyl analog chelate (MMHAC). The gilts were vaccinated with a commercial vaccine for Mycoplasma hyopneumoniae on weeks 0 and 2 post-weaning and bled for antibody titers on weeks 0, 2, 4, 8 and 12. While both groups of gilts achieved a similar titer by 12 weeks, the gilts supplemented with the MMHAC minerals reached a positive titer 8 weeks prior to gilts fed the control diet (Figure 1).
In another study designed to test if zinc can affect the response to coccidiosis vaccination and challenge, animals were vaccinated on Day 0 while being fed a zinc-deficient basal diet, zinc sulfate (ZnSO4), ZnMet or Zn as MMHAC, all at dietary levels of 40 ppm of zinc. The results indicated that zinc supplementation did improve performance of vaccinated animals (Figure 2). The study also indicated the effect of zinc on the immune response to a vaccination. Antibodies to antigens were significantly higher in animals fed MMHAC, which is an indicator of overall positive immune response to the vaccine (Figure 3).
Zinc deficiency has been shown to affect T-cell and antibody responses in animals. In another study looking at immune response, neutrophil (white blood cell) activity was measured by in vitro assay of phagocytosis, evaluating the potential for neutrophils to engulf pathogens. This process is an important part of cell function, allowing a cell to protect itself from harmful pathogens. The antibody titer in animals treated with chelated trace minerals was 2.8 fold that of the animals treated with inorganic trace minerals, which indicates better immune response and health for animal fed chelated trace minerals. The data indicated the phagocytosis was significantly greater for animals fed MMHAC than for animals fed inorganic trace minerals during week 4 (25.4% versus 15.6%) and week 12 (28.9% versus 21.7%). Chelated trace mineral supplementation in diets containing MMHAC enhanced neutrophil function and improved adaptive immune response to vaccination.
The study also showed that zinc reduced expression of inflammatory markers on jejunum of offspring and improved gut health. The abundance of inflammatory markers – IL6, IL8, IL-1b and TNFa – in offspring was examined. Zinc supplementation decreased mRNA levels of inflammatory markers (IL6, IL8, IL-1b and TNFa) in jejunums compared with offspring fed zinc deficient diets. Also, use of Zn MMHAC offered greater jejunal protection and increased offspring mRNA expression of MUC2. This gene encodes for mucin production, which serves as a barrier to protect the intestinal epithelium, creating a better enteric mucosal barrier and improving gut health.
Improved Feed Conversion Rate
Supplementation of minerals in pig diets is crucial for animal growth and health. However, the use of high-inclusion rates of inorganic trace minerals are largely excreted by the animal. Diets formulated with the right source of minerals for the best absorption in the gut will improve gut health, resulting in better feed conversion rate and a more economical feeding strategy.
In a study to measure digestibility and retention of zinc, copper and manganese in pigs fed either inorganic or MMHAC sources, the results indicated that Zn, Cu and Mn from MMHAC have greater digestibility and retention rates compared with inorganic sulfates when included in a corn–soybean meal diet.
A meta-analysis of 6 trials evaluated the effect of different levels of copper from either Cu MMHAC or CuSO4 on growth performance of nursery pigs. Results indicated that average daily gain quadratically responded with increasing copper supplementation, and the Cu MMHAC source of copper reached higher plateau compared to the inorganic source (Figure 6). The linear slope for increasing copper supplementation for gain efficiency was 2.1-fold higher for Cu MMHAC than that of CuSO4 (Figure 7). Copper MMHAC was more effective than CuSO4 in improving feed efficiency and growth rate.
Piglets are heavily challenged by a changing diet, pen moves, cross fostering, not to mention viruses, damaging gut flora and other disease exposure. Luckily, the immune system is among the most responsive to mineral status, and there's no question that mineral supplementation can improve pig health, and the supplementation with MMHAC is more beneficial than with ITMs. Better health means better gut health, which can improve rate of gain and overall feed efficiency, which ultimately will increase profitability.
Article made possible through the contribution of Cassio Villela and Novus International, Inc.