ISSUE FOCUS FEED & ADDITIVE MAGAZINE June 2024 49 tionally utilized as a nutritional aid to mitigate the adverse effects of heat-stress, betaine is recognized for its favorable effect on methylation processes. EFFECT OF HEAT STRESS ON METHYL NEEDS Globally, flocks are often exposed to heat, which can lead to diminished growth. Heat stress increases the production of reactive oxygen species (ROS) and too much ROS results in oxidative stress. As methionine plays a role in managing antioxidants, an increase in ROS and oxidative stress will direct methionine in the diet to function as an antioxidant. An expected consequence of methionine acting in this manner is reduced growth as the nutrient’s work to facilitate protein deposition is impeded. Broilers have an increased need for methionine during heat-stress to address the lack of antioxidants and methyl donors necessary to maintain growth (Del Vesco et al., 2015). How significant this shortage of methionine is was tested by Zeits et al. (2020) as well. They showed that the extra need for methionine was not as big as expected. This dietary dilemma prompted researchers to conduct a trial evaluating whether it is better to supply extra methionine or betaine to flocks. TRIAL DESIGN A trial conducted at the Trouw Nutrition Poultry Research Centre, focused on two questions: 1) Is the matrix value observed under thermal-neutral conditions also valid under heat-stress conditions? 2) Which is better at reducing the negative effect of heat stress, DL-methionine or betaine? Four dietary treatments were repeated under thermal-neutral (TN) and heatstress (HS) conditions (Table 1). The control treatment (T1) received a diet containing methionine at the requirement level and no betaine. A second treatment group (T2) received diets that replaced 14% of the methionine requirement with 0.02% betaine (96% purity). Birds in treatment three (T3) received diets that included the control treatment + extra methionine and no betaine. Birds in treatment 4 (T4) received the T3 diet supplemented with 0.02% betaine (96% purity). A total of 1,640 ROSS 308 male broilers were randomly assigned to the eight different treatments. Diets were corn, wheat, and soybean-meal-based. The minimum temperature in the heat-stress treatment was 25°C (77°F) and was increased to 32°C (89.6°F) during the day from day 11 to 28, and up to 29°C (84.2°F) from day 29 to 41. BETAINE BENEFITS IN THERMAL-NEUTRAL AND HEAT-STRESS CONDITIONS As expected, heat-stress had a significant effect on broiler performance, -10% BW and + 3% 1 2 3 4 1 2 3 4 100% Met+Cys req Met matrix used, regular use of betaine No Met matrix value used + extra Met No Met matrix value used + extra Met + regular use of betaine 100% Met+Cys req Met matrix used, regular use of betaine No Met matrix value used + extra Met No Met matrix value used + extra Met + regular use of betaine TN=Thermal-neutral, HS=Heat stress Symbols: = equal to requirements, ↓ lower than requirements, ↑ higher than requirements, - not present, ✓ present TN TN TN TN HS HS HS HS = ↓ ↑ ↑ = ↓ ↑ ↑ - ✓ - ✓ - ✓ - ✓ TRT Met Betaine Description Environment Table 1. Treatment Table
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