Evaluation of fat sources on cholesterol and lipoproteins using pigs selected for high or low serum cholesterol

Abstract

At approximately 8 weeks of age, four-way cross (Chester White×Landrace×Large White×Yorkshire) pigs ( n=24) were selected based on genetically high (H) or low (L) serum cholesterol levels—12 from each genetic group—to determine the relationship between genetics, fat source, and sex class on plasma cholesterol, growth, carcass characteristics, and cholesterol and lipid content of muscle and adipose tissues. Boars and gilts, six each from the two genetic groups, were assigned randomly to one of three dietary treatments for 46 days. A standard grower diet was modified to include beef tallow (T), corn oil (CR) or coconut oil (CC), and the pigs were given ad libitum access to feed. Cholesterol was added to each diet to ensure the diets contained the same amount of cholesterol. Except for the plasma lipids, there were no differences between boars and gilts at the initial evaluation or at the end of the treatment; therefore, sex means were pooled for statistical analyses. Body weight was unaffected by diet on days 18, 29 or 46. Blood samples were taken on days 1, 29, and 46 via the anterior vena cava. Plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL) concentrations were greater in the H than L groups (overall TC in H and L pigs=150 and 124 mg/dl, respectively, and LDL in H and L pigs=105 and 76 mg/dl, respectively). Pigs fed diets containing saturated fats had greater TC and LDL than pigs fed unsaturated fats (TC=165, 149, and 126 mg/dl for T, CC, and CR diets, respectively, and LDL=108, 88, and 77 mg/dl for T, CC, and CR diets, respectively). There were significant time×gene×sex interactions for both TC and LDL yielding subtle differences in the response of the sexes from the two genetic groups over time. Pigs were slaughtered on day 46, and carcass data were collected. There were no differences in fat at the first rib, 10th rib, last rib, or last lumbar vertebra, but differences ( P <0.05) were found between genetic groups for M. longissimus thoracis et lumborum (LTL) muscle area (H=21.0±0.8 cm 2, L=18.1±1.0 cm 2) and USDA muscle score (H=2.1±0.1, L=1.7±0.1). There were no genetic or diet effects for cholesterol content of pre-rigor or post-rigor LTL muscle. Neither genetics nor dietary treatment affected the cholesterol content of the adipose tissue. There were no differences in fat percentage between genetic groups for muscle or adipose tissue. There were differences ( P <0.05) in total lipid content among the dietary treatments for the pre-rigor (T=6.0±0.6%, CC=4.3±0.3%, CN=3.9±0.5%) and post-rigor (T=6.4±0.9%, CC=4.1±0.3%, CN=5.0±0.4%) LTL. Cholesterol accretion in muscle and adipose tissues of growing pigs was not influenced by source of fat in the diet or by their genetic propensity for high or low plasma cholesterol.