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Pregnant sow nutrition has potential effects on the muscle fiber development of progeny in utero. A total of 199 Landrace x Large White sows from parities 0 to 6 and their offspring were used to evaluate the effects of increasing the feeding amount during midpregnancy on the muscle tissue, growth performance, and meat quality of the progeny. The experiment was divided into 2 study replicates, and in each replicate, sows were assigned to 1 of the 2 treatments: 1) sows in the control group (C sows) were fed 2.5 to 3.0 kg/d (feed: 12.1 MJ of ME/kg and 0.62% lysine) throughout gestation; and 2) sows in the high group (H sows) received an extra feed allowance of 1.5 kg/d for gilts and 2.0 kg/d for multiparous sows above the C amount from d 45 to 85 of gestation (period of secondary muscle fiber formation). Sow backfat was recorded on d 40 and 85 of gestation. Sow performance (litter size and piglet BW) at farrowing and on d 18 of lactation was measured. At weaning, pigs were divided into 5 BW groups/treatment, and progeny growth performance was measured during the nursery (n = 958) and the growing-finishing (n = 636) periods. At slaughter, carcass and meat quality traits (lean content, main cut weight, pH, Minolta color, and drip loss) were recorded from the second lightest group at weaning (BW group 4; n = 90), and samples from the longissimus thoraeis muscle were taken to study muscle fiber characteristics (n = 70). The extra nutrition from d 45 to 85 of gestation did not lead to differences in litter size or piglet BW at farrowing and on d 18 of lactation. Pigs born to H mothers had fewer muscle fibers and fewer estimated primary and secondary fibers than did pigs born to C mothers (P < 0.05). However, postnatal growth performance was not consistently affected by the maternal treatment. The smaller number of muscle fibers found in the H group of pigs was associated with fewer type IIB fibers (P < 0.05) with greater cross-sectional areas (P < 0.10), which might be related to the significantly greater meat pH at 24 h postmortem and the smaller L* (lightness) values recorded in the H group of pigs. Results from the present study confirm the existence of effects of maternal nutrition on fetal development, at least in terms of muscle tissue development and meat quality, although with no beneficial effects were found for the postnatal growth performance of the progeny. Key words: growth performance, meat quality, muscle fiber, pregnancy feeding, sow

To evaluate the effects of dietary fats on the evolution of the fatty acid profile of swine backfat, 30 castrated Landrace x Duroc pigs averaging 26 kg were assigned three diets with 4% added pomace oil (O), hydrogenated fat (H), or linseed oil (L). Subcutaneous fat samples were taken from biopsies at 0, 17, 31, and 60 d, and at 24 h postmortem when pigs averaged 95 kg live weight at 82 d on trial. On d 17, saturated fatty acid (SFA) content was 2% lower for the O diet than for H and L (P < .089). There was a linear increase in SFA at a monthly rate of 2% in the three diets. The increase was mainly due to 18:0; palmitic acid percentages showed no variation. Pigs fed the O diet experienced exponential increases in monounsaturated fatty acids (MUFA), especially until d 17 (P < .001). In pigs fed the H or L diets, MUFA contents decreased at a monthly rate of 2.40%, and the same happened with oleic acid contents. Diets rich in (n-3) (L) and trans-fatty acids (H) caused exponential increases in swine backfat contents of total (n-3) and total trans, respectively. At d 31 (P < .001), 72 to 73% of the maximum contents had been reached. Contents for 20:3(n-3), 20:5(n-3), and 22: 5(n-3) follow a pattern similar to that of their precursor 18: 3 (n-3), showing an exponential increase in pigs fed the L diet, and contents for H and O treatments were lower (P < .001). The three diets caused a linear decrease in (n-6) fatty acid contents throughout the 82-d trial. Key Words: Pigmeat, Fatty Acids, Trans-Fatty Acids