Getting to the heat of the matter!
Heat stress is responsible for large economic losses in animal production around the world. Producers can play a part in help mitigating the negative effects of heat stress through nutritional solutions.
BY ADISSO A
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18.0 SS OH-SeMet
nimal production in hot conditions is a major chal- lenge in many regions and has been forecast to be- come more widespread in the future. During heat stress, several adaptive strategies are used to dissi-
pate excess heat. Firstly, when high temperatures occur, water consumption increases, and feed intake decreases (thus reduc- ing nutrient uptake). Secondly, in the attempt to dissipate heat, livestock increase heart and respiration rates. Metabolism is se- verely impacted, often resulting in oxidative stress.
Improving antioxidant status During heat stress conditions it has been shown that supplementing diets with antioxidants can help to prevent any detrimental effects. At a cellular level, metabolic changes that occur during heat stress induce an overproduction of free radicals; the cell needs to be protected by antioxidants to counteract this. Selenium plays a key role in antioxidant defence; however, the form of selenium is important. OH- SeMet has a high level of bioavailability and regulates specific selenoproteins. During heat stress OH-SeMet supplementation can increase antioxidant status, cell-
Figure 1 - OH-SeMet improved milk yield in heat stressed cattle.
Milk yield during HS, kg/d P = 0.08, +9.3%
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mediated immunity and selenium storage in tissues – to a greater extent than other forms of selenium.
Supporting metabolism Methionine is an essential amino acid for protein synthesis and downstream metabolites actively participate in antioxi- dant defences. Methionine in the form of HMTBA has been shown to be more efficient than other sources during heat stress. As it is a better supplier of cysteine, glutathione and taurine than L-Met or DL-Met. HMTBA helps protect muscle by reducing the negative influence of heat stress on growth and meat quality. Heat stress causes an increased amount of fat at the expense of lean tissue, due to its effect on nutrient partitioning. It has been demonstrated that supplementing with HMTBA has a positive impact on performance, oxidative stress and lipogenesis.
Optimising feed intake One of the key effects of heat stress is a reduction in feed in- take, with sows particularly affected by nutritional deficiencies. If a palatability enhancer is used, both the average daily feed intake of the sow and the growth rate of her piglets can be im- proved. Optimising ADFI allows sows to drive nutrients and en- ergy to the mammary gland – maximising milk production for their litters. As a result, piglets show improved growth, with bigger and heavier litters weaned. Ruminants also benefit from palatability enhancers during heat stress, in the same way.
Figure 2 - HMTBA improved broiler body weight gain and FCR under hot conditions in Brazil. 2.1 2
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DLM HMTBA BWG 14-12 d
HMTBA FCR 14-42 days
HMTBA
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▶ HEAT STRESS | MAY 2021
MILK YIELD, KG/D
PHOTO: ADISSEO
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