Dietary CLA has been reported to decrease backfat and increase marbling in pigs. Our objective was to determine whether the increase in marbling involved changes in intramuscular adipocyte number or size or both. Twenty barrows (53 kg) were penned in pairs and pens were randomly assigned to receive diets containing either 1% soybean oil (SBO) or CLA (60% CLA isomers) for 6 wk. Body weight and feed intake were determined weekly. At slaughter, loin samples were obtained and flash frozen for RNA extraction and real-time reverse-transcription PCR analysis of gene expression. After a 24-h chill, loin eye area and backfat depth were measured and subjective marbling and color scores were assigned. Loin, backfat, and belly fat samples were obtained for fatty acid analysis by gas chromatography. Loin samples were also frozen in ice-cold isopentane for histological analysis of intramuscular adipocytes. Dietary CLA did not affect BW or feed intake at any point (P > 0.10), nor did treatment groups differ in HCW (P = 0.417) or loin color (P = 0.500). The CLA-fed pigs did have less (P = 0.018) backfat and smaller (P = 0.047) loin eye area than SBO-fed pigs and had a trend for an increase (P = 0.069) in marbling score. Relative gene expression for markers of preadipocytes (preadipocyte factor 1; Pref-1), differentiating adipocytes (PPARγ), and mature adipocytes [fatty acid binding protein 4 (FABP4) and perilipin (PLIN)] were determined and normalized to the expression of acidic ribosomal phosphoprotein. No significant differences were detected, but the expression of PPARγ (P = 0.265), PLIN (P = 0.265), and FABP4 (P = 0.148) was numerically greater in CLA-fed pigs than in SBO-fed pigs. Loin samples were stained with Oil Red O to identify intramuscular adipocytes. The average cell area was increased (P = 0.030) in CLA-fed pigs. The cis-9,trans-11 and trans-10,cis-12 CLA isomers were incorporated (P = 0.006) into backfat and belly fat, but only trans-10,cis-12 CLA was increased in the loin (P = 0.004) of CLA-fed pigs. The proportion of SFA was increased (P = 0.006) by CLA in all tissues. These results indicate that the increase in marbling in pigs fed CLA may be related to increased intramuscular adipocyte size, and the combination of increased marbling and degree of saturation could improve the eating quality of CLA-fed pork.

The purpose of this study was to determine if conjugated linoleic acid (CLA) would have an effect on feeding efficiency and carcass composition of 20 finishing barrows obtained from the West Virginia University Animal Science Farm. A posttest experimental design was used to obtain data for the study. The barrows were matched for weight and placed two in a pen. The pens were randomly assigned to a diet consisting of either a 1% CLA oil or 1% soybean oil. The six week study found that weight gain, average daily feed intake, muscle lipids, loin eye area, and color were not affected by CLA. In week five average daily gain for the control group was significantly higher than the CLA group. In weeks one and five the gain to feed ratio was significantly greater for the control group. Subjective marbling scores were higher for the CLA group but not of significant value. Backfat decreased significantly in the CLA group compared to the control group. In conclusion, the use of CLA can create a leaner product with the possibility of increased marbling. iii ACKNOWLEDGEMENTS Without the help of some very special in my life, I know that I would not have made it this far in my education and career. To them I want to say thank you. My Family (Chuck, Becky, Josh, and Logan): Thank you so, so much for standing behind me and supporting me throughout all of this. Without all of you in my life, I would not have made it this far. Especially my father, who if it was not for him pushing me for the past year to complete this, I am not sure if I would have. My Committee Members: Without the help from all my committee members, I would not have been able to successfully complete my thesis and masters. Thank you. Dr. Debby Boone (Chair)-Thank you for answering my many, many questions in the recent weeks. Also, thank you for assisting me in the writing of this. Dr. Kim Barnes-Thank you for allowing me to jump on board with this swine project. I appreciate you allowing me to help in conducting this research, and for your input on the writing. Dr. Harry Boone-Thank you for answering my questions in analyzing and the writing of the data portion of this project. Siri and the Farm Crew-I greatly appreciated the help from Siri for coming each week to help me weigh the barrows and the feeders. Also want to say thank you to the farm crew in assisting me in keeping the pens clean. Tammy, Becky, Lisa, and Vanessa-Thank you Tammy for allowing me the opportunity to further my education. Finally, I want to thank Becky, Lisa, and Vanessa,