Title: Use of different types and amounts of dietary fats to redesign pork.

Background: Using high energy fat-supplemented diets in pork production can offer several economic advantages to producers when fat sources are cost effectively priced. Because of a decreased heat increment, dietary fat supplementation allows a greater proportion of dietary calories to be available for tissue synthesis when pigs are maintained at or above the thermo neutral zone. Previous research has indicated that diets that have increasing dietary saturated fatty acids (SFA) cause hypercholesterolemia, atherosclerosis development, and greater coronary heart disease risk in humans. When dietary polyunsaturated fatty acids (PUFA) are substituted for saturated fatty acids (SFA), decreased blood cholesterol concentration occurs. This information has caused the consumer to question the consumption of meat products, such as pork, which are perceived as being rich in SFAs. The objective of this study was to alter the polyunsaturated (PUFA) to saturated fatty acid (SFA) ratio in pork for better human nutrition.

Methods and findings: Pigs were fed either choice white grease or soybean oil at 10, 20, 30, or 40% of total dietary calories. All diets were based on corn and soybean meal. The study used 54 pigs with six pigs per treatment. Initial and slaughter weights were 54 and 110 kg, respectively. Skeletal muscle samples were taken from the longissimus dorsi, biceps femoris, and triceps brachii muscles. Adipose tissue samples were taken from the outer, middle, and inner 10th rib backfat layers, perirenal adipose tissue, and an inter muscular adipose deposit within the ham. Total lipids were extracted; fatty acid methyl esters were formed by trans esterification and quantified by gas chromatography. Adding choice white grease or soybean oil to diets fed growing swine did not alter animal growth rates. The PUFA from the outer 10th rib backfat layer showed linear increases (P < 0.05) when pigs were fed diets with increasingly greater soybean oil content, whereas the backfat from pigs fed diets containing greater choice white grease contents resulted in a linear increase (P < 0.05) of monounsaturated fatty acids (MUFA). Including soybean oil in the low-fat control diet at 30 and 40% increased the PUFA to SFA ratios (P:S) to 0.9 and 1.26 (P < 0.05), respectively, in longissimus muscle. The MUFA content in the longissimus muscle was decreased by 30% (P < 0.05) with the 40% soybean oil diet. Myristate, palmitate, and total SFA in longiIIssimus muscle decreased 27 (P < 0.05), 30 (P < 0.05), and 29% (P < 0.05), respectively, with the 40% soybean oil diet.

Conclusions: Including choice white grease in the diet had minimal effects on the unsaturated to SFA muscular lipid ratios. In conclusion, high fat diets rich in unsaturated fatty acids can be used effectively to redesign pork for consumers wanting to decrease their consumption of saturated fatty acids.