The overriding objective is to improve the industry-wide lack of knowledge in utilising high levels of by-products (distillers dried grains with solubles, DDGS, and wheat middlings) in late finishing diets prior to marketing to further reduce feed cost.

In order to accomplish this overall objective, two experiments were conducted at Kansas State University to determine the optimum time period of dietary fibre reduction prior to marketing as determined by growth performance, carcass characteristics (primarily yield), digestive tract weights, carcass fat iodine value and economics.

These data did provide new information in that switching pigs fed a high-fibre diet to a corn-soybean meal diet for as little as five days prior to slaughter will restored over half of the lost carcass yield. Further, switching to a corn-soybean meal based diet 15 days prior to slaughter fully restored carcass yield.

In Experiment 2, while no statistical differences were found, numerical patterns to that of Experiment 1 were seen, where pigs changed to a corn-soybean meal diet for nine days restored over half of the lost carcass yield, with 14 to 19 days of fibre diet withdrawal fully restoring carcass yield.

To help explain the change in yield, digestive tract weights were measured in Experiment 1. First, when the large intestine was weighed full of digestive contents, the pigs fed the high-fibre diet had 2.64 lb more of digestive contents remaining in the large intestine than that of pigs only fed the corn-soybean meal diet throughout the trial. After a five-day withdrawal to the corn-soybean meal diet from the high-fibre diet, full large intestine weight dropped by 2 lb.

Secondly, and more minor influence, while not statistically different, the rinsed large intestine weighed 0.27 lb more from pigs fed the high-fibre diet than the corn-soybean meal diet throughout finishing.

Since both the weight of intestinal contents and the actual weight of the large intestine negatively influence carcass yield, both can help explain why pigs fed high-fibre diets lave lower carcass yield then those fed a low-fibre diet. From a packer prospective, feeding a high-fibre diet until marketing increases the amount of waste generated and disposed of through either their own or multiple sewer systems.

For carcass fat quality, it was expected that pigs fed the high-fibre diet would have softer carcass fat due to the increased level of unsaturated fat from the DDGS and wheat middlings in that diet.

The research did, in fact, find this result. However, when evaluating the withdrawal times of the high-fibre to the corn-soybean meal diet, the iodine value of pigs did decrease (become more firm) in belly and backfat as the withdrawal days increased but did not become fully restored to the corn-soybean meal diet fed throughout. This was not surprising as previous research has shown that once pigs are fed unsaturated fat in early and middle finishing, the withdraw days to a low unsaturated fat containing diet are more substantial to return to a baseline iodine value level.

From an economic prospective, when measured as income over feed cost (IOCF = revenue/pig – feed cost/pig), in Experiment 1, a linear improvement in IOFC was reported as the days of withdrawal increased from the high- to low-fibre diet prior to marketing. The maximum return of IOCF was for pigs fed the 20-day withdrawal treatment at $27.76 per pig, which was $1.64 higher per pig than fed only the corn-soybean meal diet and $2.97 over that of pigs fed the high-fibre diet until marketing.

In Experiment 2, no statistical differences were found but, similar to Experiment 1, the maximum return on an IOCF basis was for pigs fed the 19-day withdrawal strategy at $28.88 per pig, which was $2.92 per pig higher than pigs fed only the corn-soybean meal diet and $2.30 over pigs fed the high-fibre diet until marketing.

Producer Bottom Line

Pigs fed the high-fibre, lower energy diet had poorer feed:gain ratio, lower carcass yield and softer carcass fat than pigs fed the corn-soybean meal control diet.

Withdrawing pigs from the high-fibre diet and switching them to a corn-soy control diet restored carcass yield when done for the last 15 to 20 days prior to harvest.

Pigs fed the high-fibre diet had 2.64 lb more of digestive contents remaining in the large intestine than those only fed the corn-soybean meal diet throughout the trial. After a five-day withdrawal to the corn-soybean meal diet from the high-fibre diet, full large intestine weight dropped by 2 lb.

Income over feed costs was maximised when finishing pigs were fed the high-fibre, low-energy diet until 20 days prior to marketing and switched to a corn-soybean meal diet.

Carcass fatty acid composition and iodine value were impacted by diet type and with increasing withdrawal time of a high-fibre diet containing DDGS and wheat middlings to a corn-soybean meal diet but not back to the baseline level for pigs only fed the corn-soybean meal diet.

February 2014