As global temperatures rise year upon year, threatening economic losses and placing increased environmental pressure on livestock farming, it is essential that diets are formulated to support animals in achieving proper performance, especially under challenged conditions. Data from commercial trials and studies at research centres around the globe show that trace minerals improve the resilience of animals.
Global Technical Commercial Manager Trace Minerals
Selko Feed Additives
While a wide range of stressors can threaten animals’ health, reproduction and welfare, environmentally induced heat stress is a major concern for today’s livestock producers. The detrimental effects that high temperatures can inflict on various species – especially highly productive animals – coupled with an increase in global temperatures is bringing increased scrutiny to heat stress. Considering that the seven hottest years on record have occurred since 2015 and the rate of warming has doubled since 1981 to 0.18 degrees Celsius per decade, warmer conditions seem to be the norm rather than episodic events.
In this article, we’ll consider how thermal conditions affect livestock as well as producers’ bottom lines. We’ll then turn our attention to practical approaches farmers can take to mitigate the effects of heat stress on their flocks and herds.
HEAT STRESS – CONSIDERING CONSEQUENCES AND COSTS
Animals have a thermoneutral zone, in which normal body temperature is maintained and energy expenditure is kept to a minimum. Factors such as temperature, ambient humidity and wind can influence an animal’s capability of staying within this range. When the total heat load on an animal exceeds its capacity for heat dissipation heat stress can be an unwelcome result. A reduction of feed intake is one consequence of heat stress. In pigs for example, every degree of increase in environmental temperature above 23 C° potentially reduces feed intake by 89 to 106 grams in the grow-finishing phase, dependent on the level of humidity.
Beyond reducing the level of nutrients available for the animal to use, reduced feed intake can also harm gut integrity. Less feed intake can lead to leaky gut, which increases circulating bacterial components and can lead to systemic inflammation, inducing a further loss in performance. From a sustainability perspective, leaky gut can potentially increase the environmental impact of production. Thus, from an animal welfare and environmental point of view, heat stress can cause animals to suffer physically and result in a more of the energy consumed being wasted.
Farm economics are also affected. Estimates of heat stress loss for the U.S. swine business alone total nearly US$1 billion. The magnitude of the loss heat stress imposes depends on how quickly the animals recover or the capability of the animal to respond to stressors. Producers can also play a role in managing heat stress by implementing a holistic approach that includes feed, farm and health management practices. Reducing animal density, feeding livestock during cooler parts of the day, adjusting nutritional density and providing colder drinker water are some examples of feed, farm and health adjustments that can help support animals exposed to risk of heat stress.
NUTRITIONAL INTERVENTION TO DEFEND AGAINST HEAT STRESS
Nutritional interventions represent a practical and cost-effective opportunity to reduce the negative effects of heat stress and improve animal productivity. Precision nutrition allows diets to be formulated in a manner that reduces internal metabolic heat generation. Increasing the levels of dietary fat and reducing the amount of crude protein or crude fiber is one example of tailoring the formulation to reduce metabolic heat generation. Compared to other feed ingredients, dietary fat generates less heat. In contrast, the fermentation of fiber and excess protein are associated with heat generation. Feed additives that supply antioxidants, osmolytes or gut health should be considered to support animals subjected to heat stress. Selecting trace minerals that are more bioavailable could potentially ameliorate production losses as well.
HOW MINERALS SUPPORT PRODUCTION DURING HEAT STRESS
Trace minerals are essential for maintaining animal health and production. The animal’s need for an immunological response during heat stress leads to an increase in its relative trace mineral requirements . Zinc, for example, plays an important role in the immune response, acting as a cofactor of many essential enzymes. It can also increase the expression of tight junction proteins in the gut, supporting gut integrity. Copper, much like zinc, acts as a cofactor in enzyme function and can affect microbial populations in the gut, thereby supporting proper gut functioning. Due to the effects of these trace minerals in the animal, they are a key factor to focus on during formulation, especially in cases of heat stress. Trace mineral contents in raw materials are generally low and they suffer from unpredictable availability. When selecting the right source of mineral to add to a formulation, factors to consider include content, solubility, relative bioavailability, particle size and economic value. The way a mineral is designed can have a big impact on these factors. Selko IntelliBond minerals are covalently bond minerals present in a crystalline structure. This structure allows the mineral to have low solubility in water and only become soluble under a low pH. As the structure of the trace mineral supports less reactivity with other ingredients and essential nutrients in the diet, it ensures a higher relative bioavailability for the animal compared to inorganic trace minerals.
UNDERSTANDING COSTLY REACTIONS IN THE FEED
While heat stress affects the animal, people often forget the effects heat can have on the feed and premix, especially when warm temperatures coincide with high humidities. Vitamins, for example, are highly susceptible to reactivity with minerals. In challenging conditions, such as high temperatures, formulators increase the levels of vitamins to mitigate oxidative stress. Studies have indicated that vitamin A reduced at twice the rate at 43 degrees Celsius compared to 25 degrees Celsius. When a soluble mineral source such as sulphates is included in the formulation, moisture can lead to the metal (e.g., copper, zinc or manganese) easily separating from its sulphate ligand, creating a free metal ion of positively charged particles. The loosed metal ions can rapidly attach to and degrade biological material such as vitamins, further reducing the levels of minerals present. Figure 1 illustrates the effect of 200 ppm of copper coming from either sulphate or IntelliBond, and shows that the sulphate degraded the vitamin E levels up to 70% of the initial dose. IntelliBond however performed similar to the control which contained no minerals, indicating that IntelliBond does not affect vitamin levels. As indicated earlier, fat levels in feeds can be increased in heat stress conditions as a source of energy. However, because fats are susceptible to oxidation, the formation of peroxides and free radicals can occur, adversely affecting palatability and leading to oxidative stress. This oxidation damage, much like the effects on vitamins, is irreversible. Studies performed with IntelliBond versus sulphate sources indicated a reduction in the formation of anisidine, a marker used for fat oxidation. Taken together, the inclusion of IntelliBond leads to less reactivity with other feed ingredients that play a critical role in battling the negative effects of heat stress.
MIXABILITY MATTERS – INTELLIBOND BENEFITS IN THE FEED
As animals reduce their feed intake during heat stress and fewer nutrients are taken in, it is essential that minerals be properly mixed in rations. A mineral can only exert benefits if it is consumed by the animal. Studies show that size matters when it comes to trace minerals. IntelliBond, due to its unique OptiSize technology, has an improved mixability in complete rations compared to inorganic mineral sources.
INTELLIBOND BENEFITS IN THE ANIMAL
Because IntelliBond minerals suffer less from reactivity, their improved availability for animals means a higher likelihood of meeting the animal’s requirements. The ability to meet an animal’s nutrient requirements under different circumstances enables it to respond properly to stressors. This ability can help make animals more resilient in heat stress conditions. A trial done in Australia with the University of New England indicated that feeding IntelliBond rather than sulphate trace minerals improved laying hen performance in cyclical heat stress conditions, as shown by a better egg mass and improved FCR/dozen egg (Figure 3).
During heat stress, tight junction dysfunction can lead to the influx of lipopolysaccharide (LPS) from Gram-negative bacteria into the portal and systemic blood. This can lead to stimulation of macrophages to release pro-inflammatory cytokines like TNF-α. A LPS infection trial with pigs comparing IntelliBond to inorganic minerals showed that the use of IntelliBond alleviates the immune response and appears to mitigate the drop in performance induced by LPS (Figure 4).
The tight junction dysfunction that is observed under heat stress is in part driven by a reduction in feed intake. Recent literature in ruminants demonstrated deleterious effects of feed restriction on gut barrier integrity. A study in Holstein cows under feed restriction fed zinc from IntelliBond or a sulphate source was therefore designed to evaluate the effect on gut permeability, metabolism and inflammation. Feed restriction tended to decrease ruminants’ intestinal surface area, with IntelliBond ameliorating that decrease. Overall, replacing zinc sulphate with IntelliBond zinc improved barrier morphology and modulated acute-phase protein response and neutrophil function.
As global temperatures rise year upon year, threatening economic losses and placing increased environmental pressure on livestock farming, it is essential that diets are formulated to support animals in achieving proper performance, especially under challenged conditions. Data from commercial trials and studies at research centres around the globe show that IntelliBond minerals improve the resilience of animals. Feeding the right trace mineral can helps sustain proper performance and reduce the impact of heat stress on producers’ bottom lines.
References
1. United Nations. (2022, January 19). 2021 joins top 7 warmest years on record: WMO. United Nations News. https://news.un.org/en/story/2022/01/1110022
2. Zhuge, Q., and C. F. Klopfenstein. “Factors affecting storage stability of vitamin A, riboflavin, and niacin in a broiler diet premix.” Poultry Science 65.5 (1986): 987-994.
3. Luo, X. G., et al. “Effects of dietary supplementation with copper sulfate or tribasic copper chloride on broiler performance, relative copper bioavailability, and oxidation stability of vitamin E in feed.” Poultry Science 84.6 (2005): 888-893.
4. Harshman, Jared A., et al. “115 Effects of a Chronic Lipopolysaccharide Challenge on Growth Performance and Immune Response of Nursery Pigs Fed Differing Sources of Dietary Zinc.” Journal of Animal Science 100.Supplement_2 (2022): 52-53.
5. Key, Nigel, Stacy Sneeringer, and David Marquardt. “Climate change, heat stress, and US dairy production.” USDA-ERS Economic Research Report 175 (2014).
6. Huynh, Thi Thanh Thuy. Heat stress in growing pigs. Wageningen University and Research, 2005.
7. Horst, E. A., et al. “Evaluating effects of zinc hydroxychloride on biomarkers of inflammation and intestinal integrity during feed restriction.” Journal of dairy science 103.12 (2020): 11911-11929.
About Gavin Boerboom
Gavin Boerboom received his Bachelor’s in Biomedical Sciences and Master’s degree in Human Food sciences from Maastricht University in 2016. He joined Trouw Nutrition’s R&D department right after focussing on feed additives. In 2018 he combined this role in R&D with a PhD position at Wageningen University focussing on trace mineral nutrition in monogastric animals. He completed his PhD in 2021 and joined the Selko USA team afterwards focussing on providing technical support on trace minerals for the North American market. As of August 2022, he is part of the Global Selko Feed Additives team responsible for supporting trace mineral solutions in all animal species across the globe.
