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Seventy-two crossbred pigs (Goland x Hypor), half barrows and half gilts, were assigned to one of four experimental treatments split of by the following combinations: two levels of L-lysine-HCl supplementation (0% and 0.16%) and either 0% or 0.75% CLA added to the feed. Eighteen pigs per dietary treatment were weighed at the start and the end of the trial. At the end of the trial blood samples were collected from 10 pigs per treatment. Triacylglycerol, total cholesterol, glucose, urea and total protein content of 40 pigs were determined in serum by enzymatic spectrophotometric assays. Dressing percentage (hot carcass weight/live weight at slaughter) and lean percentage were calculated. Longissimus muscle was removed for chemical composition, intramuscular collagen content (IMC) analyses, pH and colour measurements at 24 post-mortem, dry matter, nitrogen, fat and ash. Distal portions of bones of anterior and posterior legs were also collected from 36 pigs from 0.16% L-lysine-HCl lysine groups with or without CLA added (18 pigs per treatment).
Neither CLA nor lysine supplementation influenced growth, blood metabolites or carcass characteristics. CLA reduced pH24 and increased yellowness of the Longissimus muscle. Lysine increased pH24 and reduced muscle ash content. CLA reduced collagen synthesis, and lysine increased collagen synthesis in Longissimus muscle, but no influence on intramuscular collagen maturity or muscle hydroxylysylpyridinoline crosslink concentration were observed. Metacarpal bone had a smaller diameter and tended to be longer in CLA pigs than controls. Barrows had higher final weight, ADG, serum cholesterol, triacylglycerol, carcass weight and lean percentage than gilts, whereas, metatarsal diameter was larger in gilts than barrows.
It is concluded that a higher level of dietary lysine is not necessary for a major lean tissue deposition in CLA-fed heavy pigs. Although data from the present study suggest that the intramuscular collagen content in pigs may be sensitive to CLA supplementation.
C Corino, M Musella, G Pastorelli, R Rossi, K Paolone, L Costanza, A Manchisi, G Maiorano. Meat Science 2008, 79: 307-316.
