Effects of modified tall oil versus a commercial source of conjugated linoleic acid and increasing levels of modified tall oil on growth performance and carcass characteristics of growing-finishing pigs

Two experiments were conducted to evaluate the effects of conjugated linole ic acid (CLA)enriched feed additives for swine. These additives included a source of CLA that was commercially available (CLA-60) and modified tall oi l (MTO). Experiment 1 used 36 barrows (initially 37.6 +/- 2.8 kg) to compar e the effects of CLA-60 and MTO on growth performance and carcass character istics of finishing pigs. The corn-soybean meal diets contained .50% soybea n oil (control),.50% CLA-60, or .50% MTO. Pigs fed CLA-60 had less (P = .03 ) ADG from 37.6 to 72.6 kg than the control pigs; otherwise, pigs fed eithe r CLA-60 or MTO had growth performance similar (P > .15) to that of the con trol pigs. Pigs fed MTO grew faster (P = .03) and consumed more feed (P = . 10) over the duration of the experiment (37.6 to 106.4 kg) than pigs fed CL A-60. Dietary treatment did not affect (P > .15) plasma triglycerides or ca rcass characteristics, but pigs fed either MTO or CLA-60 had greater satura tion of fatty acids in the adipose tissue at the 10th rib than pigs fed the control diet. Experiment 2 used 80 barrows (initially 33.4 +/- 2.2 kg) to examine the effects of increasing levels of MTO on growth performance and c arcass characteristics of finishing pigs. The corn-soybean meal diet contai ned 1% cornstarch, which was replaced with MITO to give dietary levels of . 25, .50, or 1.00% MTO. Dietary treatment did not affect (P > .15) growth pe rformance. Feeding increasing levels of MTO quadratically decreased (P = .0 2) average backfat thickness and longissimus muscle drip loss (P = .04) and quadratically increased longissimus muscle area (P = .07) and percent age lean (P = .03). Feeding MTO tended to increase belly firmness (P < .10) com pared with pigs fed the control diet. These traits appeared to be optimized with .50% MTO. In summary, pigs fed MTO had greater ADG, ADFI, and ending BW than pigs fed CLA-60. Feeding MTO does not appear to affect growth perfo rmance but improves carcass lean content and may additionally improve some aspects of meat quality in growing-finishing pigs.