Interpretive Summary: Effects of increasing space allowance by removing a pig or gate adjustment on finishing pig growth performance.
By: Jackie Walling
An article published in the July 2018 Issue of the Journal of Animal Science investigates how finishing pig growth performance is affected by increasing space allowance in pens using gate adjustment or pig removal. It is believed that removing the heaviest pigs two weeks prior to market increases the growth performance of the remaining pigs. A minimum standard of space allowance per pig has been calculated using the equation m2 = .0336 x BW.67 where m2 is floor space (m), BW is body weight (kg), and .0336 is a constant, critical k. Carpenter et al., hypothesized growth reductions occur at k values greater than .0336. Researchers designed this study to validate space allowance using k and evaluate any discrepancies in performance between enlarging space by gate adjustment or pig removal.
The researchers at Kansas State University Swine Teaching and Research Center conducted a 71-day study using 256 pigs housed in an environmentally controlled barn. Pens housed 7 to 8 pigs grouped by like BW. An ad libitum diet of corn-soybean meal was provided and adjusted for three phases of feeding BW: 56-83 kg, 83-98 kg, and 98-124 kg. There were four treatment groups to compare using ADG, ADFI, and G:F as measurement points. All m2 measurements refer to space allowance per pig.
Treatment 1: Only .91m2 per pig
Treatment 2: Only .63m2 per pig
Treatment 3: initially .63m2 per pig, but gate adjusted
Treatment 4: initially .63m2 per pig, but heaviest pig removed
From Day 0-14, growth did not deviate among Treatment groups. Space restrictions started to affect pigs on Day 14. ADG and G:F increased in Treatment 1 while ADFI decreased in all others. Day 28 increased space allowance in Treatments 3 and 4 to .72m2. ADG and G:F were similar across the board. ADFI decreased in Treatments 2 and 4 compared to Treatments 1 and 3. Day 45 increased space allowance to .81 or .84m2. ADFI continued to decrease for Treatment 2, but similar performance was seen throughout the rest of the groups. Day 62 to the completion of the study showed the heaviest pigs in Treatment 1 and ADG decreased in pigs only allowed .63m2 compared to all other groups.
Pigs provided .91m2 had better growth performance overall (based off increasing ADG). ADFI increased more for .91m2 compared to the group living in constant .63m2 and those that had a pig removed. Gate adjustment hogs retained an intermediate level of ADFI.
Optimal growth for pigs appeared to come from a nonlimiting spatial allowance of .91m2. Previous studies suggest the equation for a minimum requirement of space per pig may not be accurate in the smaller ranges of body weight. Though useful in the past, new genetic developments in pigs may be affecting the way the relationship predicts modern growth patterns. The pigs allotted .91m2 even surpassed those groups allowed increasing space as they grew. Social dynamics were not indicative of growth performance in this design. After removing the heaviest pigs, the remaining pigs maintained the same ADG and ADFI as those pigs undergoing gate adjustment. If .91m2 cannot be maintained, it would be beneficial to employ gate adjustment, pig removal, and additional research to develop a new equation (critical k) to determine an optimum minimum space requirement.
To read the full article, visit the Journal of Animal Science.