Optimising gut health to overcome performance losses


Global climate change is influencing animal production even in temperate climates. As the number of days when the temperature humidity index exceeds animals’ comfort threshold rises, heat stress has become one of the most important ambient stressors in animal production worldwide.


BY DR JESSIKA VAN LEEUWEN, PROGRAMME MANAGER SWINE HEALTH; MELCHIOR DE BRUIN, DVM PROGRAMME MANAGER POULTRY HEALTH AND SANGEETA SINGH, PHD-MBA, PROGRAMME LEAD NUTRITIONAL SOLUTIONS, TROUW NUTRITION


H


eat stress occurs as an animal’s heat gain exceeds the heat it can dissipate. Modern production animals, selected for rapid growth, are more susceptible to heat stress, and adverse effects


include decreased productivity, susceptibility to infectious diseases and higher mortality.


Negative effects of heat stress As heat stress immediately reduces feed intake, animals lose energy for growth and production. Redistribution of blood flow


presents more challenges. During heat stress, blood vessels dilate, redirecting blood flow to the regions where heat can dissipate more easily: the skin. This reduces blood blow to the gastrointestinal tract (GIT) by as much as 40%. Oxidative stress, damage from free radicals, is another concern. Studies show that hydrogen peroxide production increases up to 50% during heat stress. Simultaneously, maldondialdehyde (MDA) levels increase three-fold in the mitochondria and two- fold in muscle. This level of MDA emphasises the importance of protecting cells (especially GIT cells) from oxidative stress to prevent cell death and loss of functional tissue. Heat stress effects (free radical generation, intestinal hypoxia, gut barrier integrity disruption) occur before clinical symptoms appear, making avoidance essential. As recently uncovered


Oxygen deficiency (a) harms gut wall mechanism and cell structures (b) allow- ing pathogen trans- location, nutrient malabsorption. Modified from Lian et al., 2020.


36 ▶ HEAT STRESS | MAY 2021


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