Prevention better than cure to cope with heat stress
Heat stress (HS) is one of the major stressors encountered by farm animals. When livestock are subjected to this environmental stress, it can be detrimental to health, well-being and performance, and if severe enough even death. Setting up multiple strategies before HS strikes is the key.
BY GEMMA TEDÓ AND MARTA BLANCH, LUCTA SA INNOVATION DIVISION M 8 Control
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0 1 Davis et al., 2021 42 ▶ HEAT STRESS | MAY 2021 4 7 10 13 16 Days of Lactation 19 22 25 Additive * * *
any of the consequences of HS are readily ap- parent on-farm, especially in swine, cattle and poultry. Several aspects are affected such as feed intake and feeding pattern in all these
species; in fact, heat-stressed animals normally reduce their feed intake leading to negative energy balance and loss of body condition. Another important effect relies on a reduced milk production in mammals; lactation is a period of high met- abolic load that sensitizes individuals to environmental tem- perature. Reproductive problems derived from HS exposure during gestation and lactation stages are also reported. Fur- thermore, negative impacts on carcass, meat, milk and egg
Figure 1 - Effect of a feed additive in a sow’s diet on lactation intake during summer in Arkansas (LSMeans, Kg/sow and day).
quality traits are well described. And, the last but not least, there are long-lasting effects on reproductive animals and in their offspring. Aforementioned points result in a substantial economic loss on the animal production industry worldwide.
Strategies to tackle heat stress HS can be mitigated on-farm using different approaches, such as, investing in equipment to contribute to environmen- tal control, through management and/or applying nutritional strategies. These strategies are present in all farmed species with sensitivity to heat stress and widely described. In this article, the emphasis will be on strategies directed towards the individual, taking into consideration two main aspects: modulation of feeding behaviour and physiological stabilisa- tion of the animal. It is important to highlight that this last group of strategies should be implemented before HS occurs, with the aim to help the animal to become more resilient to it, and additionally, also during HS circumstances, in this case to support homeostasis in this challenging period.
Physiological consequences A physiologically relevant increase in temperature has the po- tential to change the feeding pattern of the animal due to a metabolic heat produced by digestion and absorption pro- cesses, this leads to reduced feed intake and nutrient absorp- tion too. Moreover, during HS, blood flow is diverted from the intestine to the periphery, which results in hypoxia of the in- testinal epithelial cells. The lower irrigation of the intestine plus the lower nutrient uptake compromise the intestinal in- tegrity and barrier function, allowing for an influx of noxious compounds and pathogenic microbes from the intestine to the systemic circulation. Consequently, heat induced intesti- nal permeability is associated with increased blood markers of endotoxemia, hypoxia, and inflammation; all of which may contribute to multi-organ failure syndrome. So, one of the major organs affected by HS is the gastrointestinal tract and associated organs (e.g. liver).
Focus on feeding behaviour For this reason, strategies focused on eating behaviour, with the potential of improving feed efficiency, and others more centred in the reduction of the inflammatory status and oxidative stress responses, are complementary to other strategies based on the environment (e.g. coolings),
Kg feed/sow and day
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