By Annie B. Lerner, Mike D. Tokach, Jason C. Woodworth, Steve S. Dritz, Joel M. DeRouchey, Robert D. Goodband, Travis G. O’Quinn, John M. Gonzalez and Emily A. Rice, Kansas State University; and Matt W. Allerson, Holden Farms
Market pig weights in the United States have continued to increase over the past several years and averaged 282 pounds in 2017. With the expectation that market weights will continue to increase in the future, it is necessary to better understand the optimal floor space allowance required for pigs raised to heavier live weights.
In addition to adjusting the initial stocking density of a pen, topping is another strategy that producers implement to provide finishing pigs increased floor space. Topping involves the removal of one or more of the heaviest pigs in the pen prior to the final marketing event. This additional space allows the remaining pigs to reach the target market weight, provides more consistent weights at the packing plant and may be an ideal strategy to simultaneously maximize space allowance and pigs marketed per pen.
The objective of the present study was to understand space requirements of pigs raised to 360 pounds by either providing increasing floor space allowance via decreased initial stocking density or by implementing traditional topping strategies. The experiment was conducted at a commercial finishing barn in Minnesota and incorporated seven treatments. The experiment began when pigs were approximately 48 pounds and lasted for 160 days.
The first four treatments (Table 1) consisted of increased initial stocking density and did not utilize topping strategies: 1) 14 pigs per pen (12.7 square feet per pig); 2) 17 pigs per pen (10.4 square feet per pig); 3) 20 pigs per pen (8.9 square feet per pig); and 4) 23 pigs per pen (7.7 square feet per pig). The fifth treatment began with 25 pigs per pen (7.1 square feet per pig) with three pigs per pen topped on Day 93, then on Day 122 pens were topped to a common inventory of 20 pigs per pen, and a final topping event occurred on Day 147 to achieve a common pen inventory of 17 pigs per pen. The sixth treatment started with 23 pigs per pen (7.7 square feet per pig) and was topped to a common inventory of 20 pigs per pen on Day 108 with a final topping event occurring on Day 147 to reach a common inventory of 17 pigs per pen. These topping events were scheduled according to when pigs would reach maximum stocking density according to previous research.
Growth performance and final body weight are depicted in Figures 1-4. Reducing floor space via initial pen inventory (Treatments 1-4) impacted pig performance as expected. As floor space allowance was decreased from 12.7 to 7.7 square feet per pig, average daily gain, average daily feed intake and final body weight were also decreased for the overall trial. There was no evidence that decreasing floor space allowance from 12.7 to 7.7 square feet per pig impacted feed to gain ratio. It should be noted the F/G across all treatments for the heavy weight pigs were ~3.0 which demonstrates the genetic improvement for late-finishing feed efficiency.
The treatments that incorporated multiple marketing events (Treatments 5 and 6) were evaluated in comparison with each other and to the treatment that was initially stocked at 7.7 square feet per pig with only one marketing event (Treatment 4). There was no evidence that overall ADG, ADFI or final BW differed between these three treatments. Feed efficiency was improved for pigs initially stocked at 7.1 square feet per pig and marketed four times compared to both treatments that initially allowed 7.7 square feet per pig, regardless of marketing strategy. Additionally, F/G was improved for pigs that began at 7.7 square feet per pig and were marketed three times compared to the treatment that also began at 7.7 square feet per pig but was only marketed once at the end of the study.
In conclusion, these results indicate that decreasing space allowance of heavy weight pigs reduces growth, feed intake and final body weight, although use of multiple marketing events prior to final marketing may allow for increased number of pigs marketed per pen while balancing reduced growth performance often associated with increased stocking density.
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