Total body electrical conductivity (TOBEC) measurement of compositional differences in hams, loins, and bellies from conjugated linoleic acid (CLA)-fed stress-genotype pigs

Dietary Conjugated Linoleic Acid Does Not Adversely Affect Bone Mass in Obese fa/fa or Lean Zucker Rats

Conjugated linoleic acid (CLA) elevates body ash in healthy animals. The objective of the present study was to determine if single or mixed CLA isomers improve bone mass in an obese and hyperinsulinemic state. Male (n = 120) lean and obese fa/fa Zucker rats (age, 6 weeks) were randomized to 8 weeks on a control diet or to 0.4% (w/w) cis-9, trans-11 CLA (Group 1); 0.4% (w/w) trans-10, cis-12 CLA (Group 2); 0.4% (w/w) cis-9, trans-11 CLA and 0.4% (w/w) trans-10, cis-12 CLA (Group 3); 0.4% (w/w) cis-9, trans-11 CLA, 0.4% (w/w) trans-10, cis-12 CLA, and traces of other CLA isomers (Group 4); and 0.4% (w/w) cis-9, trans-11 CLA, 0.4% (w/w) trans-10, cis-12 CLA, and 0.3% (w/w) other CLA isomers (Group 5). Bone area (BA), bone mineral content (BMC), and bone mineral density (BMD) of the whole body, spine, and femur were measured at baseline (6 weeks) and at 14 weeks of age. Effects of genotype, diet, and genotype × diet interactions were assessed using factorial analysis of variance. At 6 and 14 weeks, whole-body BA and BMC were lower in lean rats compared with fa/fa rats. Similarly, at 14 weeks, fa/fa rats had a higher spine and femur BMD despite a lower femur weight. The fa/fa rats in Groups 4 and 5 had higher adjusted whole-body BMC compared with Group 3, but not with Group 1, Group 2, or the control. In lean rats, Group 3 had a greater adjusted whole-body BMC than Groups 1 and 2, but not Group 4, Group 5, or the control. Thus, commercially available CLA mixtures and single CLA isomers do not affect bone mass in a hyperinsulinemic, obese state.

Positional distribution of fatty acids in triacylglycerols from subcutaneous adipose tissue of pigs fed diets enriched with conjugated linoleic acid, corn oil, or beef tallow

This study was conducted to determine the effects of dietary beef tallow, corn oil, and conjugated linoleic acid (CLA) on the distribution of fatty acids among positions within triacylglycerols. Crossbred barrows (n=6 per treatment group) received diets containing 1.5% beef tallow, 1.5% corn oil, or 1.5% CLA for 5 weeks. Subcutaneous adipose tissue samples were obtained immediately postmortem. The fatty acid composition was determined for the sn-2 positions of the triacylglycerols by digestion with Rhizopus arrhizus lipase. Fatty acids in the sn-1/3 position were calculated from these data. Feeding CLA increased (P<0.05) the concentration of total saturated fatty acids (SFA, especially 16:0) and isomers of CLA in adipose tissue lipids, but reduced (P<0.05) the concentration of total monounsaturated fatty acids (MUFA, especially 18:1n-9). Dietary CLA caused an accumulation of total SFA in the sn-1/3 position, with a proportional decrease in total MUFA and 18:2n-6 in the outer positions. Correspondingly, lipids extracted from CLA-fed pigs had slip points that were 10 °C higher (P<0.05) than those from corn oil- or tallow-fed pigs. These data suggest that dietary CLA increases the melting point of lipids in porcine adipose tissue by increasing the proportion of SFA at the sn-1/3 position of lipids.

Evaluation of the effects of dietary fat, conjugated linoleic acid, and ractopamine on growth performance, pork quality, and fatty acid profiles in genetically lean gilts1

An 8-wk study of the effects of CLA, rendered animal fats, and ractopamine, and their interactive effects on growth, fatty acid composition, and carcass quality of genetically lean pigs was conducted. Gilts (n = 228; initial BW of 59.1 kg) were assigned to a 2 x 2 x 3 factorial arrangement consisting of CLA, ractopamine, and fat treatments. The CLA treatment consisted of 1% CLA oil (CLA-60) or 1% soybean oil. Ractopamine levels were either 0 or 10 ppm. Fat treatments consisted of 0% added fat, 5% choice white grease (CWG), or 5% beef tallow (BT). The CLA and fat treatments were initiated at 59.1 kg of BW, 4 wk before the ractopamine treatments. The ractopamine treatments were imposed when the gilts reached a BW of 85.7 kg and lasted for the duration of the final 4 wk until carcass data were collected. Lipids from the belly, outer and inner layers of backfat, and LM were extracted and analyzed for fatty acid composition from 6 pigs per treatment at wk 4 and 8. Feeding CLA increased (P < 0.02) G:F during the final 4 wk. Pigs fed added fat as either CWG or BT exhibited decreased (P < 0.05) ADFI and increased (P < 0.01) G:F. Adding ractopamine to the diet increased (P < 0.01) ADG, G:F, and final BW. The predicted carcass lean percentage was increased (P < 0.05) in pigs fed CLA or ractopamine. Feeding either 5% fat or ractopamine increased (P < 0.05) carcass weight. Adding fat to the diets increased (P < 0.05) the 10th rib backfat depth but did not affect predicted percent lean. Bellies of gilts fed CLA were subjectively and objectively firmer (P < 0.01). Dietary CLA increased (P < 0.01) the concentration of saturated fatty acids and decreased (P < 0.01) the concentration of unsaturated fatty acids of the belly fat, both layers of backfat, and LM. Ractopamine decreased (P < 0.01) the i.m. fat content of the LM but had relatively little effect on the fatty acid profiles of the tissues compared with CLA. These results indicate that CLA, added fat, and ractopamine work mainly in an additive fashion to enhance pig growth and carcass quality. Furthermore, these results indicate that CLA results in more saturated fat throughout the carcass.

Measurement of belly composition variability in pigs by in vivo computed tomographic scanning

The belly region composition of a representative commercial pig sample of 130 castrates was examined by in vivo spiral computed tomographic (CT) scanning. The lean meat percentage, the muscle/fat tissue ratio within the total body and separately within the bacon part were estimated by image analysis. The lean meat content of the total body was determined by the EU reference method. A correlation of r = 0.97 was found between lean meat content of the total body determined by CT estimation and the slaughtering results. The pigs were divided into seven groups on the basis of their lean meat content. The muscle percentage of the bacon part was 26% and 67%, respectively, in the two groups representing the two extremes of lean meat percentage (36% and 67%, respectively). The total volume of the bacon part was relatively constant (8.6 +/- 1 dm3) in the groups representing different lean meat categories. At the same time, the fat tissue volume of the bacon part was considerably higher while its muscle tissue volume was markedly lower in the group of the lowest than in that of the highest lean meat content (6.6 vs. 2.5 dm3 and 2.4 vs. 5.5 dm3, respectively). To describe changes in the tissue composition of the bacon part during fattening, 10 castrates were scanned repeatedly at 70, 90 and 110 kg of liveweight. A linear regression model was developed to characterise the continuous decrease observed in the muscle/fat ratio within the bacon part due to increasing liveweight.

Conjugated linoleic acid pork research

The driving force behind most conjugated linoleic acid (CLA) research in swine has been related to potential improvements in animal production. Early work that used rodent models indicated that feeding CLA could potentially reduce body fat, increase lean content, increase growth rate, and improve feed conversion efficiency. Producer-backed funding organizations were, therefore, receptive to proposals to extend this research to pigs, and many studies have been completed worldwide. In general, improvements in body composition were found, but evidence indicating that CLA improves growth rate or feed conversion was limited. Inclusion of CLA into pig diets was, however, shown to increase muscle marbling fat and fat hardness, and both of these characteristics have the potential to increase carcass value. Currently, Badische Anilin- & Soda-Fabrik AG (BASF) has the international marketing license to include synthetic CLA in animal feeds, but to date this practice is not approved in Canada or the United States. If and when approval is granted, the next step in realizing CLA's economic potential would be to seek approval for claiming CLA enrichment in pork and pork products. Given the ability of swine to accumulate relatively high amounts of CLA in their tissues, pork and pork products could become an important vehicle for delivery of physiologically significant amounts of CLA to consumers.

Modulation of body composition and immune cell functions by conjugated linoleic acid in humans and animal models: benefits vs. risks

We have reviewed the published literature regarding the effects of CLA on body composition and immune cell functions in humans and in animal models. Results from studies in mice, hamsters, rats, and pigs generally support the notion that CLA reduced depot fat in the normal or lean strains. However, in obese rats, it increased body fat or decreased it less than in the corresponding lean controls. These studies also indicate that t10,c12-CLA was the isomer that reduced adipose fat; however, it also increased the fat content of several other tissues and increased circulating insulin and the saturated FA content of adipose tissue and muscle. Four of the eight published human studies found small but significant reductions in body fat with CLA supplementation; however, the reductions were smaller than the prediction errors for the methods used. The other four human studies found no change in body fat with CLA supplementation. These studies also report that CLA supplementation increased the risk factors for diabetes and cardiovascular disease including increased blood glucose, insulin, insulin resistance, VLDL, C-reactive protein, lipid peroxidation, and decreased HDL. Most studies regarding the effects of CLA on immune cell functions have been conducted with a mixture of isomers, and the results have been variable. One study conducted in mice with the purified c9,t11-CLA and t10,c12-CLA isomers indicated that the two isomers have similar effects on immune cell functions. Some of the reasons for the discrepancies between the effects of CLA in published reports are discussed. Although significant benefit to humans from CLA supplementation is questionable, it may create several health risks in both humans and animals. On the basis of the published data, CLA supplementation of adult human diets to improve body composition or enhance immune functions cannot be recommended at this time.