Effect of floor space allowances on growth performance of finishing pigs marketed at 138 kilograms1,2,3

Abstract

Current floor space allowances were determined in research studies conducted 10 to 20 yr ago using pigs that were marketed at a BW of about 113 kg or less. Currently, pork producers are regularly marketing pigs that weigh over 128 kg. Given this precipitous increase in market weight, we conducted 2 experiments to determine if floor space allowances previously determined apply to pigs marketed at greater than 128 kg. Experiment 1 was conducted at 5 university research stations throughout the Upper Midwest region. In this experiment, we evaluated the growth performance, salivary cortisol concentrations, and lesion scores of pigs weighing between 27 and 138 kg provided 0.71, 0.80, 0.89, 0.98, or 1.07 m/pig of floor space. Within each station, group size (range = 6 to 19 pigs) remained constant across floor space treatments but pen size was altered to achieve the desired space allocations. There were 14 replicate pens for each treatment. Overall, increasing floor space allowance increased final BW (linear, = 0.04) and tended (linear, < 0.06) to increase ADG and ADFI. There were no improvements in final BW or ADG beyond 0.89 m/pig. The G:F was not influenced by increasing floor space allocation. Salivary cortisol concentrations and lesion scores were not affected by floor space allowances. Experiment 2 focused on floor space needs of pigs nearing market weight and was conducted at 4 research stations. Pigs weighing about 130 kg were assigned to pens that provided 0.71, 0.80, 0.89, 0.98, or 1.07 m/pig of floor space. Group size ranged from 4 to 11 pigs per pen but was constant across floor space treatments within station. The study lasted 2 wk and there were 8 replicate pens per treatment. As floor space allowance increased, ADG (0.86, 0.95, 0.95, 1.10, and 1.06 kg; linear, < 0.01), ADFI (3.03, 3.26, 3.22, 3.49, and 3.25 kg; quadratic, < 0.05), and final BW (145.6, 145.7, 146.4, 148.3, and 147.9 kg; linear, < 0.01) increased. Based on the results of these 2 experiments, pigs marketed at about 138 kg require at least 0.89 m/pig to support optimal growth performance. However, heavier pigs (about 148 kg) at the end of the finishing period require 0.98 m/pig.

Effects of increasing space allowance by removing a pig or gate adjustment on finishing pig growth performance1,2

“…More recently, 2 studies (Flohr et al, 2016;Thomas et al, 2017) have applied these equations in both commercial and research environments and found reductions in performance due to inadequate space allowance at lighter BWs than predicted previously. Johnston et al (2017) also observed that floor space allowance predicted by Gonyou et al (2006) might be underestimated for heavy weight market pigs. In the study herein, we used a limited number of pigs per pen (7 or 8) relative to what is frequent observed in commercial production (25 to 30 pigs per pen).…”

“…Gonyou et al (2006) proposed a critical k value, 0.0336, and suggested that pig growth should not be decreased until their BW reaches the critical point where there is inadequate space to maintain maximal growth rate. However, recent studies (Flohr et al, 2016;Johnston et al, 2017;Thomas et al, 2017) demonstrated that growth reductions due to inadequate space may start to occur at k value above 0.0336.…”

Effects of space allowance and marketing strategy on growth performance of pigs raised to 165 kg

“…Recent research evaluating space allowance (either by changing pen inventory or adjustable gating) for pigs raised to modern market weights continues to report decreased growth rate as a consequence of reduced FI ( Johnston et al, 2017 ; Thomas et al, 2017 ; Carpenter et al, 2018 ). Thomas et al (2017) and Carpenter et al (2018) reduced floor space in pens with fixed inventories and observed decreased ADG and ADFI, with these reductions occurring from ~70 kg BW, or prior to reaching the critical k -value.…”

“…Unlike growth rate and FI, the effects of space allowance on gain efficiency in the literature are more variable. Several have reported no evidence for differences ( Johnston et al, 2017 ; Thomas et al, 2017 ; Carpenter et al, 2018 ), while others observed decreased G:F as floor space becomes restricted ( NCR-89 Committee on Confinement Management of Swine, 1993 ; M. C. Brumm and NCR-89 Committee on Management of Swine, 1996; Street and Gonyou, 2008 ). Possible mechanisms for decreased G:F accompanying floor space restriction include decreased protein deposition ( Chapple, 1993 ), increased activity, and increased trips to the feeder in crowded pens ( Shull, 2010 ).…”

“… Johnston et al (2017) conducted an experiment to evaluate the space requirement for heavy weight pigs and suggest that 0.98 m 2 /pig is necessary for pigs weighing 130 kg due to little evidence of improved growth performance beyond this space allowance. The current data displayed continued linear improvement in ADG and ADFI up to 1.17 m 2 /pig, suggesting the point at which floor space would no longer improve performance was not reached.…”