Search

Isolation of total RNA from frozen muscle and fat samples typically results in small yields due to the presence of connective tissue between muscle fibers, which impairs complete tissue homogenization, and the excess of fat and relatively small cellularity of adipose tissue. Meat quality studies involve determination of fatty acid composition and content from muscle and subcutaneous fat samples, a process that may produce an excess of lyophilized tissue samples. The purpose of this work was to investigate the stability of total RNA in lyophilized tissue samples generated during the routine detection of fatty acid content of pig muscle and fat tissues, stored at room temperature or at -20[degrees]C. The protocol described here results in increased yields of total RNA from freeze-dried samples stored at -20[degrees]C, which facilitates the homogenization step. The isolated RNA is suitable for common gene expression techniques such as final point and quantitative reverse transcription-PCR. Key words: freeze-dry, gene expression, lyophilization, meat quality, pig doi: 10.2527/jas.2009-2298

The objectives of this study were 1) to determine whether selection toward less subcutaneous fat thickness at constant intramuscular fat content in pigs is related to tissue-specific changes in the expression of lipogenic enzymes acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD), and A% desaturase ([DELTA]6d); and 2) to investigate tissue specific distribution of the porcine ACC, SCD, and [DELTA]6d. The study was conducted on 20 purebred Duroc barrows. Ten animals were from a group selected for decreased subcutaneous fat thickness at constant intramuscular fat content (experimental group). The other 10 animals were from the unselected (control) group. Distribution of ACC, SCD, and [DELTA]6d was investigated in semimembranosus muscle (SM), subcutaneous adipose tissue (SA), liver (L), kidney (K), heart (H), diaphragm (D), rectus capitis muscle (RCM), and abdominal fat (AF). The enzyme expression was studied in 10 animals in the case of SM and SA and in 4 animals in the case of other tissues. The following expression pattern was established for ACC: SM [less than or equal to] H = K [less than or equal to] D< RCM < L < AF = SA, whereas the expression patterns for SCD and [DELTA]6d proteins were SM < H < RCM < D < L < K < AF = SA and RCM = SM = D < L [less than or equal to] H < SA < K < AF, respectively. Expression of ACC and SCD proteins was less in subcutaneous adipose tissue of the experimental animals when compared with the control group (P < 0.001). However, no difference (P > 0.1) in ACC and SCD protein expression between the control and experimental groups was observed in SM. Expression of [DELTA]6d protein did not differ between the control and experimental groups for SA (P = 0.47) or SM (P = 0.31). There was a positive relationship between muscle SCD protein expression and intramuscular fat content (r = 0.48, P < 0.05). Intramuscular fat content did not correlate with ACC or [DELTA]6d protein expression (P = 0.23 and P = 0.80, respectively). We conclude that SCD might be an effective potential biomarker for intramuscular fat deposition. Key words: intramuscular fat, lipogenic enzyme expression, meat quality, pig, subcutaneous fat doi: 10.2527/jas.2009-2091

Data on a pig line selected for litter size (H) and a control line (C) were used to estimate the correlated responses to litter size in carcass, meat, and fat quality traits. The differences between the genetic means of animals from line H and line C were used to estimate correlated responses. No differences were found between the two lines in carcass measurements except backfat depth, which was higher (P < 0.05) in line H (0.69 [+ or -] 0.28 mm). This led to a decrease (P < 0.05) in predicted carcass lean content (-6.0 [+ or -] 2.7 g/ kg). Differences in joint weight distribution between lines were primarily due to belly weight, which was higher (P < 0.05) in line H (6.3 [+ or -] 1.2 g/kg). There were no important changes in meat quality traits. Chemical composition of semimembranosus muscle (SM) and subcutaneous backfat (SB) differed between lines only for DM in SB, which was higher (P < 0.05) in line H (15.1 [+ or -] 7.1 mg/g), and for the fatty acid composition of intramuscular fat. The fatty acid profile in line H showed a lower (P < 0.01) proportion of polyunsatturated fatty acids (-14.7 [+ or -] 4.8 mg/g FA), particularly with regard to the content of linoleic acid (-12.5 [+ or -] 3.9 mg/g FA). It is concluded that selection for litter size reduced the lean content in the carcass but the proportion of high-priced cuts and meat quality traits were not affected. However, selection may lead to changes in the composition of intramuscular fat lipids towards a lower content of polyunsaturated fatty acids. The observed correlated effects can be interpreted assuming that selected pigs are more mature at the same weight, though the underlying genetic and physiologic processes that cause them are unknown. The results of this experiment indicate that the metabolic pathways taking part in fat metabolism should be considered first. Key Words: Correlated Responses, Fats, Litter Size, Meat Quality, Pigs, Selection

Data on individually tested pigs from a line selected for litter size (H) and a control line (C) were used to estimate the correlated responses to litter size in growth, fat, and feeding behavior patterns from 75 to 165 d of age. During the test period, BW and ultrasonic midback (UMB) and loin (ULB) backfat were recorded periodically on the same animal. Individual voluntary feed intake (DFI), number of visits (NVD), and feeding time (FTD) were measured on a daily basis using an automatic feeding system. Third degree polynomial models with random regression coefficients were used to describe BW, UMB, ULB, DFI, NVD, and FTD as a function of age. The first derivative of the model for BW was used to estimate growth rate. Several measurements of efficiency were obtained using polynomial models on accumulated DFI, NVD, and FTD. The difference between the genetic means of animals from line H and line C was used to estimate correlated responses. The H pigs showed higher BW throughout most of the test period (2.29 [+ or -] 0.90 kg at 135 d of age, P < 0.05) but they were not different (P = 0.18) from C pigs at the end of the test (102 kg, SD 9). Thus, despite both lines showing similar average growth rate on the test, line H grew faster at the start of the test (34 [+ or -] 11 g/d, P < 0.01), but it grew more slowly by the end (-68 [+ or -] 27 g/d, P < 0.05). Fat deposition rate differed between lines, with H pigs showing higher UMB (1.26 [+ or -] 0.23 mm, P < 0.01) and ULB (1.32 [+ or -] 0.28 mm, P < 0.01) at 165 d of age. The difference between lines in total on-test feed intake was not significant (P = 0.10), but intake was slightly higher in line H between 105 and 135 d of age (2.28 [+ or -] 1.25 kg, P - 0.07). Line H showed a higher feed efficiency up to about 100 d of age, whereas line C performed better from this age until 165 d of age. However, differences never exceeded 18 [+ or -] 6 g of weight gain per kilogram of feed consumption (P < 0.01). Total feed efficiency throughout the test period was slightly higher in line C (1.37 [+ or -] 0.77 kg of weight gain after eating 185 kg of feed, P = 0.08). Lines H and C had distinct feeding patterns with regard to eating frequency. Pigs from line H ate less frequently, but instead they spent more time and ate more per visit. In the long term, selection for litter size could result in pigs with less capacity of lean growth. Key Words: Correlated Responses, Fats, Feeding Behavior, Growth, Litter Size, Pigs

Litter size and production trait responses to experimental selection for increased litter size in a Landrace pig population are reported. The numbers of sows and litters available for the first cycle of selection were 3,034 and 961, respectively. Selection was carried out using a BLUP repeatability animal model for number of piglets born alive (NBA). The experiment included one selection and one control line, each with three nonoverlapping generations. The selection line (H) consisted of the 160 sows with the highest breeding values and one boar from each of 25 full-sib families with the highest breeding values. The control line (C) consisted of 160 sows and 25 boars randomly chosen. The two subsequent generations in each line were obtained by random selection. A Bayesian analysis of genetic response using a multivariate model was carried out by Gibbs sampler. Marginal posterior distributions were obtained for direct response in NBA, and for correlated response in weight (WT), and backfat thickness (BT) at 175 d of age. The posterior means and posterior standard deviation (PSD) for direct genetic response of NBA ranged from 0.32 (PSD 0.08) in the first parity to 0.64 (PSD 0.08) in the fourth. The posterior means for correlated genetic response in WT and BT were -0.66 kg (PSD 0.36) and 0.20 mm (PSD 0.10), respectively. For WT and BT, the 95% highest posterior density regions (HPD) contain zero-correlated genetic response. Marginal posterior distributions of selection differentials were investigated. The posterior means for standardized selection differentials for NBA in different parities ranged from 0.70 (PSD 0.12) to 0.94 (PSD 0.06) in females for line H, from 0.22 (PSD 0.19) to 0.34 (PSD 0.10) in males for line H, and from 0.08 (PSD 0.08) to 0.13 (PSD 0.07) in females for line C. All available males were used in line C. Results from this experiment showed that selection for increased litter size is effective. Responses to selection were heterogeneous across parities, suggesting that litter size in each parity may have a different genetic background. No correlated genetic response to growth and backfat thickness was observed. Key Words: Bayesian Theory, Pigs, Prolificacy, Selection Responses

A total of 66,620 records from the first six parities for number of piglets born alive (NBA) from 20,120 Landrace sows and 24,426 records for weight (WT) and backfat thickness (BT) at 175 d of age were analyzed to estimate genetic parameters. The pedigree consisted of 47,186 individuals, including 392 sires and 5,394 dams. Estimates were based on marginal posterior distribution of the genetic parameters obtained using Bayesian inference implemented via the Gibbs sampling procedure with a Data Augmentation step. The posterior means and posterior standard deviation (PSD) for heritability of NBA ranged from 0.064 (PSD 0.005) in the first parity to 0.146 (PSD 0.019) in the sixth parity, always increasing with the order of the parity. The posterior means for genetic correlations of litter size between adjacent parities were, in most cases, greater than 0.80. However, genetic correlation were much lower between nonadjacent parities. For example, the genetic correlation was 0.534 (PSD 0.061) between the fourth and the sixth parity for NBA. The posterior means of heritability for WT and BT were 0.229 (PSD 0.018) and 0.350 (PSD 0.019), respectively. Posterior mean for genetic correlation between WT and BT was 0.339 (PSD 0.044). The posterior means for genetic correlation between production (WT and BT) and reproduction traits (NBA in different parities) were close to zero in most cases. Results from this study suggest that different parities should be considered as different traits. Moreover, selection for growth and backfat should result in no or very little correlated response in litter size. Key Words: Genetic Parameters, Growth, Litter Size, Parity, Pigs

Three Iberian boars were bred to 31 Landrace sows to produce 79 [F.sub.1] pigs. Six [F.sub.1] boars were mated to 73 [F.sub.1] sows. The [F.sub.2] progeny from 33 full-sib families (250 individuals) were genotyped for seven microsatellites spanning the length of chromosome 4. Least squares procedures for interval mapping were used to detect quantitative trait loci (QTL). A permutation test was used to establish nominal significance levels associated with QTL effects, and resulting probability levels were corrected to a genomewide basis. Observed QTL effects were (genomewide significance, position of maximum significance in centimorgans): percentage of linoleic acid in subcutaneous adipose tissue ([is less than] 0.01, 81); backfat thickness ([is less than] 0.01, 83); backfat weight ([is less than] 0.01, 80); longissimus muscle area (0.02, 83); live weight (0.19, 88); and percentage of oleic acid in subcutaneous adipose tissue (0.25, 81). Gene action was primarily additive. The Iberian genotypes were fatter, slower growing, and had lower linoleic and higher oleic acid contents than Landrace genotypes. The interval from 80 to 83 cM contains the FAT1 and A-FABP loci that have been shown previously to affect fat deposition in pigs. This is the first report of a QTL affecting fatty acid composition of subcutaneous adipose tissue in pigs and provides a guide for the metabolic pathways affected by candidate genes described in this region of chromosome 4. Key Words: Fat, Fatty Acids, Landrace, Pig Breeds, Quantitative Trait Loci

A quadratic polynomial model with random regression coefficients was used to describe preweaning growth curves of two beef cattle breeds widely used in the Spanish Pyrenees, according to genotype and season of birth effects. In addition, parameters of individual variability that can be used in a stochastic model were obtained. Data recorded indoors from birth to weaning of 217 Brown Swiss calves (3,509 observations) born either in spring or autumn (BS-S, BS-A) and 101 spring-born Pirenaica calves (PI-S, 967 observations) were analyzed. A quadratic model accurately fitted the preweaning weights ([R.sup.2] = .99). Use of random regression coefficients improved the weaning weight adjustment; the residual variance of the model with intercept and linear random coefficients (9.61 [kg.sup.2]) was smaller than that of the model without them (130.03 [kg.sup.2]). Brown Swiss-S and PI-S calves had similar birth weight (40.9 [+ or -] .96 vs 39.4 [+ or -] .73 kg), but BS-S calves achieved significantly higher weaning weights at 150 d of age (175.2 [+ or -] 2.45 vs 158.4 [+ or -] 3.17 kg). Preweaning growth patterns were different for each season of birth, but there were no differences in weaning weight at 150 d of age (172.9 [+ or -] 2.01 BS-A vs 175.2 [+ or -] 2.45 BS-S). Standardization of weaning weights using a linear approximation could lead to biases, especially when comparing animals from the two calving seasons. The estimate of variances of random parameters should be done within breed and season of birth in order to take into account heteroscedasticity. The variances for BS-A, BS-S, and PI-S were 39.9, 57.6, and 32.2 [kg.sup.2] for the intercept, respectively, and .0159, .0141, and .0205 [kg.sup.2] for the linear coefficient. Covariance between the intercept and the linear coefficient (.34 [kg.sup.2]) was only statistically significant in the case of BS-S. The individual variance of weight at 150 d was 424.7 [kg.sup.2] and 526.7 [kg.sup.2] for BS-S and PI-S, respectively, almost 65% of the observed variance of weaning weight. Key Words: Beef Cows, Breeds, Calving Season, Genetic Variation, Preweaning Period