Title: Improving the Feeding Value for Saturated Fats for Lean Genotype Swine: Effects of Tallow and Supplemental CLA

Principle Investigator: Jack Odle

Year: 2000

Objective: To determine the additive effects of dietary tallow and CLA supplementation on pig growth and performance and carcass quality, pork quality, and belly quality.

Lay Summary/Industry Summary: : Swine producers are continuously searching for alternative energy sources to feed their market pigs. Since 1993 the pig/com price ratio, which is an indicator of profitability, has averaged less than 20 (approximate break-even point). In 1999, from March to August, the ratio has ranged from 10 to 15 (USDA, 1999). The low price of hogs and relatively higher cost of com causes rising interest in supplemental dietary fat because it is an inexpensive source of calories. This is especially true in the Southeast where hog prices tend to be 5% lower than the national average and a bushel of com is about $0.45 higher due to added transportation costs (Kelly Zering, personal comm.).

Southeastern producers have limited options for sources of supplemental fat. Tallow is available in mid-west markets. However, transportation is cost-prohibitive so increasing amounts of unsaturated fats, such as rendered restaurant grease, are being added to the diets. However, packers and processors such as Smithfield and Oscar Meyer are concerned about the effects of feeding unsaturated fat on the composition of pork fat (Morgan et al., 1994). One solution to the soft fat problem created by increased polyunsaturated fats in the diet is to remove supplemental fat altogether. Indeed, one large integrator’s response to this concern was to remove supplemental fat completely from their finishing diets (Todd See, personal comm.).

Our data show that tallow and conjugated linoleic acid will significantly reduce the iodine value (N) of belly fat and have an additive effect when supplemented together. This combination can enhance the value of tallow as a fat source. We did not detect any negative effects of tallow or CLA supplementation on growth, feed intake, feed efficiency or carcass quality. Fatty acid composition of belly fat was altered by both tallow and CLA addition. They both resulted in increased saturation of belly fat and when supplemented together resulted in a reduction of the N to 62. This is within the range desired by the industry. However, supplementation of yellow grease led to increased linoleic acid in belly fat samples and could result in increased opportunity for lipid oxidation in pork products. Unfortunately, feeding yellow grease combined with CLA did not result in Ns of belly fat as low as those from pigs fed no supplemental fat, CLA alone, tallow or tallow combined with CLA. Further, our taste panel evaluation determined that flavor attributes of bacon and pork products from pigs fed CLA would be accepted by consumers and would not differ from commodity pork products.

Scientific Abstract: Both conjugated linoleic acid (CLA) and tallow supplementation have been shown to increase firmness of pork bellies. However, effects of CLA on flavor of pork have not been described. This study evaluated the combined effects of dietary CLA and supplemental fat (SF) in lean-genotype gilts (n = 144) and on organoleptic characteristics of bacon and pork loin samples (n = 48). Gilts (49.3 kg) were randomly assigned to a 2 x 3 factorial arrangement of supplemental fat level and linoleic acid supplementation. Animals were slaughtered (96.9 kg) after a period of 47 d. Supplemental fat treatments included 0%, 4% yellow grease (YG), and 4% tallow (T). Linoleic acid treatments included l % com oil (CO) or l % CLA (CLA-60, Natural Lipids, Norway). Lysine:calorie ratio was constant in all diets. A trained six member sensory panel developed a flavor profile on commercially cured bacon samples (12 descriptors) and center-cut boneless pork loin chops (19 descriptors) using a 14-point universal intensity scale. Samples were vacuum packaged and stored at -7° C, then thawed in a refrigerator 20 to 24 hand cooked immediately prior to analysis. There were no significant effects of CLA on ADG (0.87 kg), G/F (0.38), or ADFI (2.26 kg) (P> 0.10). No effects of CLA were detected on carcass measurements including longissimus muscle area, backfat depth, water holding capacity, or Minolta L*, a*, orb* values (P > 0.10). Four percent supplemental fat improved G/F (0.37 vs 0.40 ± 0.01; P < 0.02) and ADG 0.85 vs 0.88 ± 0.02 kg; P < 0.09). Feeding CLA resulted in an increase in C18:0 and a decrease in C18:l (P < 0.01), suggesting a reduction in activity of the delta-9 desaturase enzyme. CLA supplementation improved green weight (2.51 vs 2.69 ± 0.05 kg; P < 0.02), pump weight (3.06 vs 3.28 ± 0.06 kg; P < 0.02), and smoke weight (2.30 vs 2.45 ± 0.06; P < 0.08) of pork bellies. No effects of supplemental fat level on belly weights were detected (P > 0.10). Bacon samples from pigs fed CO were considered to have a sweeter flavor (4.07 ± 0.07) than those fed 0% SF (3.89 ± 0.07; P < 0.04). The intensity of salty flavor was higher in bacon samples from pigs fed CO (6.18 ± 0.09) compared to those fed CLA (5.86 ± 0.1O; P < 0.02). The intensity of salty aftertaste was greater when CO was combined with YG (5.21 ± 0.14; P < 0.07) or T (5.44 ± 0.14; P < 0.01) than CO alone (4.85 ± 0.14) but SF combined with CLA was not different from CLA alone (fat* la; P < 0.02). Sour flavor intensity tended to be lower in loin samples from pigs fed CLA than from those fed CO (1.60 vs 1.73 ± 0.06; P < 0.09). Samples from animals fed 4% T tended to have slightly lower (P < 0.09) notes of astringent aftertaste (1.42 ± 0.08) compared to those fed 0% SF (1.62 ± 0.09) or 4% YG (1.66 ± 0.09). Minimal differences in flavor descriptors determined by the sensory panel were detected. In conclusion, CLA but not tallow supplementation increased belly weights and increased belly weight may result in improved processing characteristics. Panel results indicate consumer acceptance of bacon and pork products from pigs fed CLA will not differ from commodity pork products.Publications: Journal of Nutrition

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