Hydrogenated dietary fat improves pork quality of pigs from two lean genotypes

Pork quality is influenced by nutrition, genetics, management, and pork-processing procedures. Pigs of lean genotype fed diets high in unsaturated fat may have thinner, lower-quality bellies with a soft fat composition. Therefore, we investigated the effects of supplementing 5% choice white grease that had been chemically hydrogenated to iodine values of 80, 60, 40, or 20 on pork quality. Diets were fed to barrows and gilts of two genotypes (NPD [Ham-line x Manor hybrid] and PIC [406, 419, or 420 x C22]; n = 240) in a 4 x 2 x 2 factorial design. Pigs (76.8 kg of mean initial weight) were placed on test at a common age and were fed dietary treatments for 52 d. Pigs of PIC genotype were heavier at trial initiation, had higher feed intake and feed conversion ratio (F/G; P < 0.05), and greater backfat (26.3 vs. 24.0 mm; P < 0.001) and loin depth (59.0 vs. 55.3 mm; P < 0.001) compared with the NPD genotype pigs. As the iodine value of dietary fat was reduced, belly thickness increased (P < 0.05) and length decreased linearly (P < 0.05). Congruently, belly fat iodine value decreased from 73.9 to 67.4 (linear effect; P < 0.001) and belly fat C18:2 concentration declined from 20.6 to 16.3% (linear and quadratic effect; P < 0.001). The belly mono- and polyunsaturated fat ratio increased 29% as diet iodine value declined from 80 to 20 (linear and quadratic effect; P < 0.001). Further, there was a linear increase (P < 0.001) in saturated fatty acid concentration of belly fat (C14:0, C16:0, and C18:0) as dietary fat iodine value declined. Quadratic (P < 0.005) effects were detected in the level of C18:1trans as iodine value decreased from 80 to 20, paralleling dietary content. Dietary fat iodine value did not affect fat digestibility, ADFI, or F/G. Pork belly quality was improved as defined by reduced iodine value, C18:2 content, increased saturated fatty acid content, increased thickness, and decreased length as dietary iodine value decreased. Results indicate that reduction of dietary fat iodine value by chemical hydrogenation has the desirable effect of improving pork quality and does not alter growth performance.