Evaluation of Betaine and Methionine Replacement for Improving Performance and Meat Quality for Broilers reared under Higher Temperature Conditions

4,096 broiler chicks were randomly allocated to 128 floor pens (32 birds/pen). 2,048 day-old male broilers were placed in the east end of a barn, and the following week 2,048 day-old male broilers were placed in the west end. At each placement day, half of the chicks were Cobb 500 and half were Ross 708, and each pen contained only one breed source. East end birds received coccidiostat in the feed, west end received coccidial vaccine, and each end was under separate environmental control. Eight diets contained two levels of coccidiostat (0, 1 lb./ton), methionine (deficient, adequate), and betaine (0, 2 lb./ton). Live weights were measured at days 0, 15, 31, 42 and 56. Cocci scoring was performed on day 22, ammonia flux was measured on day 36, and paw scoring was performed on days 42 and 56. Processing occurred on days 43 (5 birds/pen) and 57 (5 birds/pen). There were no significant differences between treatments in live weights for days 15, 31, 42, or 56. Day 42 paw scores for birds fed betaine + deficient methionine were significantly lower than other treatments, for Cobb Treatments 3 and 7, and for Ross Treatment 3. Birds in the west end had no cocci lesions, while the east did. Ross birds receiving coccidiosis-vaccine, fed betaine + reduced methionine had lower ammonia flux than Ross birds receiving either coccidiostat, fed no betaine + reduced methionine or Ross birds receiving coccidiosis-vaccine, fed betaine + adequate methionine. At day 57, Cobb birds fed betaine + reduced methionine had significantly higher breast and tender weights than all other Cobb birds, while Ross birds fed reduced methionine + no betaine had higher wing weights than any Ross birds receiving betaine. These findings indicate betaine supplementation can act to partially spare methionine. Betaine supplementation was also shown to decrease single-day heat-related mortality and also affect processing performance in broilers reared to heavy weights. ACKNOWLEDGEMENTS Thank you to my major advisor, Susan Watkins. You have been a wonderful guide and mentor. Thank you for your time, constant positivity, and the opportunities you have given me. Sincere thanks to my fellow research partners, past and present: Tyler Clark, Mary Foy, Deepthi Gadde, Pramir Maharjan, David McCreery, Chance Williams, Joel Thompson, and Samantha Shelton. You are a great team of smart and funny people. Thank you all for your help. Randy Chick, thank you for all of your insight, efforts, and guidance with the research trials. Thank you for graciously making the time and effort to serving on my committee. Thank you, Nick Anthony, for assistance with my office and for your time to serve on my committee. Charles Maxwell, thank you for your time to serve on my committee. I am very grateful for your assistance. Thank you, Mike Kidd, for your enthusiasm and willingness to help me find opportunities and develop as a student. Thank you to my parents, Lonnie and Kate Graham, for your constant support and help. You are both wonderful teachers, supporters, and friends. I am very glad to have you as parents. My brother, Lucas, thank you for your support while completing this program. Thank you, to my children, Sophie and Graham, for helping me with the chickens. And last but not least, to my husband, Kyle, thank you for making it possible for me to complete this program. Your support and humor have helped more than you know.