Forty eight Iberian castrate pigs were divided into two groups: low feeding level (L) during the growing period, and high feeding level (H) for the same period. At the end of the growing period and with 80 kg body weight in L fed pigs, and 125 kg body weight in H fed pigs, animals present in each group were further divided into two groups: receiving during the fattening period a high feeding level, and a low feeding level, determining thus four experimental groups (LL, LH, HH, HL). At the beginning of the fattening period ultrasonic measurements of Longissimus dorsi muscle lean and backfat were carried out. Moreover, backfat biopsy samples were taken at the beginning of the growing and fattening periods, and after slaughtering. Chops from the Longissimus dorsi were obtained from the carcasses in order to determine real measurements of lean and backfat thicknesses, and of intramuscular fat content. Different activities of enzymes were evaluated in the subcutaneous backfat.
The growing phase lasted for 163 days in alls groups, and then animals were slaughtered at 153 kg body weight. The ages at slaughter were different depending on the feeding plan: 383 days for HH, 406 for HL, 439 for LH, and 503 days for LL. The best feed conversion ratio was found in the LH fed pigs. At the slaughtering, the LL regime determined the higher values of loin depths, lower intramuscular fat percentage in the Longissimus dorsi and the lower backfat thicknesses. In the subcutaneous backfat samples the higher proportion of monounsaturated fatty acids were found in LH and LL fed pigs (P< 0.05), being the lower values of saturated fatty acids found in the LL fed pigs. Feeding high levels to the animals also determined a higher lipogenic enzymatic activity in the subcutaneous backfat.
A marked effect of feeding level was found in the meat characteristics (in terms of fatty acids) and on pig productivity, results showed that the highest monounsaturated fatty acid concentration was higher in LL fed pigs, but the LL group spend a long period to reach market weight . The LH strategy provided a reasonable fatty acid composition while not extending too much the time to reach the market weight.
Daza, A., Rey, A.I., Menoyo, D., Bautista, J.M., Olivares, A., López-Bote, C.J. (2007). Animal Feed Science and Technology 138: 61-74