279 Impact of Increasing Additions of Choline Chloride on Broiler Chicken Body Weight Variability

Abstract Previously, we observed a linear improvement in feed conversion and no difference in body weight (BW) in broiler chickens fed increasing additions of choline chloride in a diet with reduced digestible methionine (dMet) reared under summer environmental conditions. Poor uniformity in broiler carcass weights can negatively impact processing yields and profitability. The objective was to evaluate the impacts of increasing choline concentration on BW variation of broilers from the previous study. Yield Plus × Ross 708 male broilers (n = 2,232) were reared for 41 d on used litter in floor pens (n = 31 birds per 2.3 m2 pen). Birds were fed 1 of 6 corn and soybean meal-based, reduced dMet diets containing 0, 400, 800, 1,200, 1,600, or 2,000 mg added choline chloride per kg of feed (n = 12 pens per treatment). Diets were provided in 3 phases: starter from d 0 to 15 with 0.42% dMet, grower from d 16 to 28 with 0.42% dMet, and finisher from d 29 to 41 with 0.37% dMet. Rearing temperatures began at 34.4 °C, were reduced over 21 d to 26.7 °C and maintained there until d 41. Individual weights were collected at 15, 28, and 41 d. Broilers (n = 10 per pen based on proximity to pen median BW) were processed on d 43. The distance of each bird from both mean and median of the pen, added choline treatment, and whole flock BW over time was calculated. Uniformity was reported comparing within a pen to the pen, treatment, and flock averages. Intra-pen CV was calculated using pen mean and median weights. Data were analyzed as a 1-way ANOVA using SAS PROC GLIMMIX with added choline as main effect. Means were separated at P ≤ 0.05 with tendencies declared at 0.05 < P ≤ 0.10 using the PDIFF option, and orthogonal contrasts were evaluated. Supplementing the diet with choline increased individual bird distance from the treatment and flock average BW from d 15 to 41 (P ≤ 0.0244). Intra-treatment and flock uniformity showed a quadratic response to increasing additions of choline at d 41 (P ≤ 0.0214) as did the CV within pens at d 41 (P = 0.0455). Variability of carcass part weights of birds selected for processing was not impacted by choline addition. While supplementing dMet-deficient diets with choline chloride can improve broiler feed efficiency without impacting BW, it may alter variation among individual birds depending on the concentration in the diet. These results indicate that there is variation in how individual birds respond to choline chloride additions and highlight the importance of analyzing variation as part of comprehensive feed additive evaluation to deepen the understanding of its impacts.