Improving energy utilization in high by-product diets with copper

The overriding objective is to determine if energy utilization from diets containing high levels of by-products and differing in energy content can be improved with supplemental Cu in commercial finishing pigs. In order to accomplish the overall objective, an intensive field experiment was conducted to determine the effects of added Cu and diet type (energy and fiber) on growth performance, carcass characteristics, economics, energy digestibility, gut morphology, and mucosal mRNA expression of finishing pigs.

Although these data did not demonstrate the large increase in feed intake and gain from feeding added Cu observed in previous experiments, it did provide data on possible modes of action for Cu. Furthermore, it was successful at demonstrating the differences in growth performance when high-fiber, high-energy diets are fed to finishing pigs compared to a simple corn-soybean meal-based diet. It is important to note, that the original proposal intended to have an additional diet type that was high in fiber and low energy; however, due to technical difficulties in the production facility, data integrity for those treatments could not be maintained. Therefore, those treatments were not included in the data set.

Treatments included the main effects of diet type, a corn-soybean meal-based diet (corn-soybean meal-based) or a high byproduct diet (byproduct) with 30% distillers dried grains with solubles (DDGS) and 15% bakery meal, and with or without added Cu (0 or 150 ppm added Cu). Overall, neither added Cu nor diet type influenced growth performance. However, caloric efficiency was decreased for pigs fed the byproduct diet compared to the corn-soybean meal-based diet. One potential reason for this is accurate energy values for bakery meal does not exist and is a potential area for future research needed by producers. Furthermore, pigs fed the byproduct diet had decreased carcass yield and HCW F/G and tended to have decreased HCW and HCW ADG compared to pigs fed the corn-soybean meal-based diet. This is consistent with previous NPB Project #12-167.

Dry matter and gross energy digestibility (GE) during the early finishing period were improved when Cu was added to the corn-soybean meal-based diet, but not in the byproduct diet. During the late finishing period, added Cu increased DM digestibility by nearly 1% and GE digestibility by 3% while pigs fed the byproduct diet had decreased DM and GE digestibility compared to those fed the corn-soybean meal-based diet. This could potentially explain why Cu may have provided a late finishing response in some previous studies. For gut morphology, pigs fed added Cu had decreased crypt depth in the distal small intestine compared to those fed no added Cu. This could potentially be a sign of improved gut health with reduced turnover intestinal cells over time. Furthermore, relative mRNA expression of intestinal fatty acid binding protein (iFABP) was decreased in pigs fed added Cu compared to those fed no added Cu. A decrease in iFABP of the distal small intestine mucosa of pigs fed added Cu would suggest that the gene responsible for iFABP transcription is possibly down regulated with added Cu. If fat digestibility is truly increased with Cu supplementation, we would expect increased iFABP expression to accommodate the additional end products of fat digestion (Fatty Acids). This makes for an interesting finding demonstrating that Cu does impact intestinal metabolism of dietary fats at the molecular level, unfortunately there is currently very little data available for comparison and further research in this area is warranted.

From an economic prospective when measured as income over feed cost (IOFC = gain value/pig – feed cost/pig), statistically there were no differences between diet type nor added Cu. Economics were calculate on a carcass basis because of the known negative impact that high fiber diets have on carcass yield and producer profit. Numerically, when calculated on a constant time basis pigs fed added Cu had a $1.75 advantage over pigs not feed added Cu in the corn-soy diet. For pigs fed the byproduct diet, the advantage for feeding Cu was $0.96/pig. When calculated on a constant weight basis, only a small numerical improvement was observed in the corn-soy diet with added Cu.

Producer bottom line:
• Adding 150 ppm Cu to the diet during the early finishing period tended to increase in ADG, but growth performance for the overall growth study was not influenced by added Cu.
• Pigs fed the byproduct diet compared to the corn-soybean meal-based diet had decreased ADG and ADFI during the early finishing period, but diet type did not affect overall growth performance even though pigs fed the byproduct diet had a reduction in carcass yield and HCW.
• Dry matter and energy digestibility are influence by diet type and Cu may provide a means for improving that; however, more research is need to determine the typical amount of improvement that can be observed
• Added Cu provided a numerical improvement in IOFC on both a constant weight and time basis.

Dr. Bob Goodband
Kansas State University
Department of Animal Science and Industry
242 Weber Hall

Manhattan, KS 66506
785-532-1228