Effect of Double Stocking and Nursery Split-Out Age on Wean-to-Finish Growth Performance and Economic Parameters of Growing Pigs

It is common practice in the swine industry to double stock wean-to-finish barns with nursery pigs until a desired weight or age has been reached, at which point half of the pigs are removed and transported to a feeder-to-finish barn for the remainder of the finishing period. However, it is uncertain what the optimal timing and duration of the double stocking strategy is to maximize growth and carcass characteristics. The objective of this study was to determine the effects of nursery split-out age in double-stocked wean-to-finish barns on subsequent growth performance, carcass characteristics, and economics. A total of 1,260 (PIC TR4 x (Fast LW x PIC L02)) finishing pigs with an initial BW of 5.7 kg were used in a 155-d growth trial with 21 pigs per pen and 10 replications (pens) per treatment. Split-outs were performed at 4, 6, and 8 weeks after nursery placement, at which time 50% of the pigs were loaded on a truck and transported to mimic the stress pigs would endure during split-outs and then returned to the barn and placed in separate pens at single stocking density. Data was analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with pen as the experimental unit. From day 0-56 there was a linear decrease in ADFI and subsequently ADG and BW as nursery split-out age increased (Linear, P < 0.003). The differences in ADFI were not significant from day 56-155; however, G:F and ADG improved as nursery split-out age increased (Linear, P < 0.019). Overall, there was an improvement in G:F as nursery split-out age increased (Linear, P = 0.024). There was no difference (P > 0.16) in live weight, HCW, or carcass yield, however, lean yield, loin depth, and back fat thickness tended to be decreased (Linear, P ≤ 0.09) as split-out age increased. In terms of economics, fixed cost decreased as split-out age increased, reducing total cost per pig (Linear, P < 0.001). Cost per unit of gain improved as split-out age increased (Linear, P = 0.026). When taking into account the savings in facility cost by double stocking pigs in the nursery longer, nearly $1/hd of marginal revenue was gained when marketing to the packer. These data indicate that double stocking up to 8 weeks does not result in impaired feeder-finish growth performance and can be utilized without a negative impact on overall economic parameters or final carcass characteristics.