Effect of floor space allowances on growth performance of finishing pigs marketed at 138 kilograms

Today on the blog, we are sharing a study by our colleagues: Dr. Lee Johnston from the College of Food, Agricultural, and Natural resources Sciences (CFANS) and Sara Schieck from the swine extension team, regarding floor space allowance and its impact on growth on finishing pigs.

The full article is available online in open access on the Journal of Animal Science website.

Rationale

Most floor space allowance studies were conducted 20 years ago when pigs were sent to market when they reached 113kg (around 248 lb) whereas pigs are currently sent at 128kg (281 lb). Therefore, guidelines need to be updated.

Study design

Experiment 1: Pigs from 27 to 138 kg (59 to 304 lb) were housed providing either 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space (respectively 7.64, 8.61, 9.58, 10.55, 11.52 square ft/pig). Growth rate, cortisol concentration and lesion scores were measured for each pig.

Experiment 2: Pigs around 130 kg (286 lb) were housed providing either 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space (respectively 7.64, 8.61, 9.58, 10.55, 11.52 square ft/pig).

Results

Floor space allowance finishing pigs
Impact of floor space allowance on Average Daily Gain (ADG), Average Daily Feed Intake (ADFI), and growth to feed ratio (G:F) in the last 16 weeks of the experiment.

Initial body weight of pigs was not different across floor space allowances; however, increasing floor space allowance increased final body weight (linear, P = 0.04) and tended to increase ADG (linear, P = 0.06) and ADFI (linear, P = 0.06). Gain efficiency was not influenced by increasing floor space allowance. There were no differences in initial salivary cortisol concentrations across floor space treatments. Similarly, there were no differences in salivary cortisol among floor space allowances 2 and 1 wk before the final weight, when pigs should have experienced the greatest differences in crowding among treatments.

Based on the growth performance and pig welfare data collected in Exp. 1, a clearly optimal floor space recommendation is not apparent. The equation from previously published studies estimates that 138-kg pigs require 0.91 m2 of floor space; therefore, the present study provided 2 treatments below and 2 treatments above the predicted requirement. Our data are clear that pigs in the present study did not respond to floor space allowances greater than the predicted need of 0.91 m2 with improved growth performance or welfare.

In Exp. 2, the floor space needs of heavy market pigs could be studied isolated from the diluting effects of the early growth period that were present in Exp. 1. Results of Exp. 2 indicate that 0.98 m2/pig optimized growth performance of pigs between the weights of 133 and 148 kg.

Conclusion

Pigs marketed at 138 kg BW optimize growth performance when provided 0.89 to 0.98 m2 of floor space per pig. However, the negative effects of low space allocations were mostly observed in heavy pigs. Therefore, the use of a pig removal strategy near the end of the finishing period may be an effective strategy to diminish the negative effects of crowding when pigs are near market weight.

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 m2/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, P = 0.04) and tended (linear, P < 0.06) to increase ADG and ADFI. There were no improvements in final BW or ADG beyond 0.89 m2/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 m2/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, P < 0.01), ADFI (3.03, 3.26, 3.22, 3.49, and 3.25 kg; quadratic, P < 0.05), and final BW (145.6, 145.7, 146.4, 148.3, and 147.9 kg; linear, P < 0.01) increased. Based on the results of these 2 experiments, pigs marketed at about 138 kg require at least 0.89 m2/pig to support optimal growth performance. However, heavier pigs (about 148 kg) at the end of the finishing period require 0.98 m2/pig.