The effects of glycerol, dried distillers grains with solubles, and alternative fat sources on growth performance, carcass parameters, belly and bacon characteristics and fatty acid profiles in grow-finish pigs

The purpose of the experiments in chapters II and III was to evaluate the effects of using by-products such as glycerol and dried distillers grains with solubles in grow-finish pigs diets. In chapter II crossbred pigs were assigned to one of 6 dietary treatments to assess the impact of increasing levels of glycerol in the grow-finish pig diet on growth, carcass traits, and bacon quality. The 6 dietary treatments were: (1) Control, 0% Glycerol (Gly) (2) 5% Gly (3) 10% Gly (4) 15% Gly (5) 20% dried distillers grains w/solubles (DDGS) and (6) 20% DDGS +10% Gly. Feeding glycerol increased ADG and ADFI quadratically while linearly decreasing G:F. Increasing Gly linearly increased tenth rib backfat (BF) corresponding to a linear decrease in percent fat free lean (FFL). Feeding Gly resulted in minimal changes in belly weights, and bacon slice characteristics or fatty acid profiles. Feeding Gly up to 10% of the grow finish pig diet can improve ADG and ADFI however, carcass quality may be impacted by increasing BF and reducing percent FFL. Feeding DDGS with Gly resulted in major shifts in the fatty acid profile of all tissues. The experiment in Chapter III utilized crossbred pigs assigned to 1 of 7 dietary treatments to assess the impact of removing 20% DDGS and adding choice white grease (CWG) or beef tallow (BT) to the late finish diets on growth and carcass traits. Feeding an added fat source the last 26 d of finishing resulted in greater ADG and a greater G:F. No differences (P > 0.05) were observed for overall (d 0-103) ADG and ADFI across treatments. Overall GF was greater for pigs fed added fat the entire grow-finish period than for pigs fed added fat the last 26 d of finishing or not at all. Pigs fed DDGS had reduced 10th rib loin muscle area, decreased last rib BF and decreased carcass yield than pigs fed corn-SBM diets. Feeding corn-SBM resulted in firmer bellies than pigs fed DDGS. The level of linoleic acid (C18:2n6) changed increased in pigs fed DDGS in all adipose tissues resulting in greater IV, increased omega 6 to omega 3 ratios, and decreasing saturated to unsaturated ratios in all adipose tissues. Withdrawing 20% DDGS and adding CWG or BT for the last 26 d had little effect on growth performance or pork quality in grow finish pigs. Adding CWG or BT may partially recover some of the adverse fat quality effects caused by the increase in linoleic acid in the diet when DDGS is fed. In conclusion, using by-products in grow-finish pig diets is possible with minimal effects on growth performance, carcass parameters, belly and bacon characteristics, but may greatly shift fatty acid profiles.