Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

Michael O. Smith

Committee Members

Brynn Voy, Agustin Rius, Arnold Saxton


A study was conducted to determine the effects of supplemental choline (CHO) and betaine (BET) on broiler performance, carcass characteristics, corticosterone levels, immune organ weights, intestinal morphology and choline metabolites under thermoneutral (TN: 23.9oC) and heat stress (HS: 28-36oC) conditions. Eight hundred day-old chicks (400 per temperature treatment) were assigned in groups of 10 to each of five dietary treatments: 1 (CON) the basal diet; 2 (CHO500), basal diet plus 500 ppm methyl equivalents added CHO; 3 (CHO1000), basal diet plus 1000 ppm methyl equivalents added CHO; 4 (BET500), basal diet plus 500 ppm methyl equivalents added BET and 5 (BET1000), basal diet plus 1000 ppm methyl equivalents added BET. Pen feed intake and body weights were recorded weekly. Foot pad dermatitis (FPD) was assessed and litter samples were collected on day 42. On days 22 and 45, blood samples were collected from eight birds per treatment to determine corticosterone and choline metabolites concentrations. On day 52, birds were processed, spleen, bursa and thymus were weighed. Liver and intestinal samples were collected for CHO and CHO metabolites determination and histology (intestine). Breast color was measured and drip loss evaluated 4 and 7 days post slaughter. Results showed that HS birds consumed 20.59% less feed, gained 23.35% less weight and had lower feed efficiency compared to TN birds (P < 0.05) during days 22-49. Foot pad dermatitis was decreased (P = 0.003) by CHO500 and BET1000. Drip loss 4 days post slaughter was reduced (P = 0.04) by CHO500 (0.60%) in HS and BET1000 (0.83%) in TN birds. On day 45, HS increased (P = 0.02) corticosterone levels (3.61 ng/ml HS vs 2.16 ng/ml TN). Thymus and bursa weights were reduced (P = 0.03) by HS. There was a diet X temperature interaction for liver BET concentration (P = 0.03) whereas intestinal BET was increased only by diet (P = 0.02). Liver CHO and glycerophosphocholine were increased by temperature (P = 0.01). Dietary supplementation with CHO and BET did not negate the negative impacts of HS on broiler performance and immune system. However, they reduced FDP as well as drip loss.

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