294 Evaluation of Variation in Nursery Pig Growth Performance Utilizing Different Allotment Strategies

Abstract

Abstract A total of 720 pigs (200×400, DNA) were used in two 42-day nursery trials (initial BW = 6.20 ± 0.12 kg and 5.63 ± 0.16 kg, respectively) to evaluate multiple strategies for allotting pigs to pens in research. At placement, the population was split into 3 cohorts with similar average BW and standard deviation. Each cohort was randomly assigned 1 of 3 allotment strategies. Strategy 1 (random) utilized a simple randomization strategy with each pig randomized to pen independent of all other pigs. Strategy 2 [bodyweight (BW) distribution] sorted each pig within the cohort into 1 of 5 BW groups. One pig from each weight group was then randomly assigned to pen, such that distribution of BW within pen was uniform across pens. Strategy 3 (BW grouping) sorted pigs within the cohort into 3 BW categories: light, medium, and heavy. Within each BW category, pigs were randomized to pen to create pens of pigs from each BW category. Within each experiment, there were 72 pens with 5 pigs per pen and 24 pens per allotment strategy. For all strategies, once pigs were allotted to pens, pens were allotted to 1 of 2 treatments for a concurrent trial. In Exp. 1, environmental enrichment using ropes tied near the pan of the feeder was compared with a control with no enrichment. In Exp. 2, treatment diets consisted of basal levels of Zn and Cu from the trace mineral premix for the duration of the study (110 and 17 mg/kg, respectively; NC), or diets (PC) with carbadox (50 g/ton; Mecadox, Phibro Animal Health, Teaneck, NJ) fed in phase 1 and 2, pharmacological levels of Zn and Cu (2,414 mg/kg Zn from ZnO; 168 mg/kg Cu from CuSO4) in phase 1 and only Cu (168 mg/kg Cu from CuSO4) in phase 2. There were no meaningful allotment × treatment interactions (P > 0.10) for either study (Table). In Exp. 1, there were no effects of environmental enrichment on growth performance (P > 0.10). In Exp. 2, pigs fed the PC diet had greater (P < 0.001) ADG, ADFI, G:F, and final BW compared with pigs fed the NC diet. The coefficient of variation (CV) within pen between all pens on that allotment strategy and for the entire population of that allotment strategy were calculated for both trials. For between-pen CV, pigs allotted using BW distribution and BW grouping strategies had the least CV at allotment and final weigh day in both trials. Results were used to estimate the replication required with each allotment strategy to obtain significant differences with different percentage responses. Fewer replications are required to discern significant differences in ADG when allotting pigs utilizing BW grouping. However, there is no meaningful difference between allotment strategies in replications required to detect significant differences for G:F.