Genetic correlations among carcass cross-sectional fat area ratios, production traits, intramuscular fat, and serum leptin concentration in Duroc pigs

Abstract

Animals accumulate fat in tissues as subcutaneous, intermuscular, intramuscular, and abdominal fat. Genetic interrelationships of respective fat depositions, however, have not been examined in depth. This study estimated genetic parameters for subcutaneous, intermuscular, and abdominal fat areas of 545 Duroc purebred pigs slaughtered at 105 kg of BW. Measurements were obtained using an image analysis system for positions between the 5th and the 6th thoracic vertebra (56TV), at half body length (HBL), and at the last thoracic vertebra (LTV) of the carcass. Moreover, serum leptin, which is a hormone product that is synthesized and predominantly expressed by adipocytes, was measured to determine if serum concentrations of leptin are useful as physiological predictors of fat accumulation in pigs. The heritability estimate of all fat area percentage at the HBL (0.70 +/- 0.03) was significantly greater than at the 56TV (0.53 +/- 0.03) or the LTV (0.55 +/- 0.04). Furthermore, the heritability estimate of subcutaneous fat areas at the HBL (0.71 +/- 0.04) was greater than at the 56TV (0.56 +/- 0.04) or LTV (0.60 +/- 0.03). Moreover, high heritabilities were estimated for ultrasound backfat thickness (BF; 0.72 +/- 0.03) on the left side at the position of HBL, intramuscular fat content of the loin (0.51 +/- 0.03), the seam fat score (SFS; 0.49 +/- 0.04), and the serum leptin concentration (0.62 +/- 0.05). Increased genetic correlations of BF with the fat area percentage of subcutaneous fat and all fat at 56TV (0.90 +/- 0.03 and 0.91 +/- 0.03), at HBL (0.88 +/- 0.03 and 0.94 +/- 0.01), and at LTV (0.88 +/- 0.03 and 0.90 +/- 0.02) were estimated. The genetic correlations of serum leptin concentration with the percentage of subcutaneous fat area and all fat areas at each position were also high (0.72 to 0.82 and 0.83 to 0.84, respectively). These results suggest that BF and leptin are good indicators of selection for decreasing fat deposition. Increased genetic correlation of the SFS with intermuscular fat area at 56TV (0.74) suggests that SFS is an effective indicator for decreasing intermuscular fat. The genetic correlation between the leptin concentration and feed conversion ratio was high (0.75 +/- 0.04). Results of this study indicate that the combination of BF and serum leptin concentration is a valuable indicator that can be incorporated into selection programs to improve carcass quality and feed efficiency in pigs.

Intermuscular and intramuscular adipose tissues: Bad vs. good adipose tissues

“…In another study, image analysis of abdominal fat, INTMF and SQF from adipose tissue samples from Duroc pigs slaughtered at 105 kg indicated that within anatomical sites the genetic correlations between SQ and INTMF were high whereas, correlations between IM and INTMF fat were much lower. 70 Heritability estimates for INTMF varied between locations and were lower than SQF area heritabilities at all three anatomical sites. 70 In finished feed lot steers, heritability estimates for INTMF and SQF were similar (0.40, 0.42).…”

Effect of genotype on fatty acid composition of intramuscular and subcutaneous fat of Celta pig breed

“…Regarding IMF content it is well known that the occurrence of intramuscular fat deposition has a strong genetic component (Gispert et al, 1997;Suzuki et al, 2009). In this case, the three genotypes of Celta pig showed a markedly different adipogenic capacity, since the Barcina line had more IMF compared to the other ones.…”

Leptin in farm animals: where are we and where can we go?

“…Lean-line pigs differed in carcase composition from normal pigs, and leptin at slaughter correlated with backfat thickness (r 5 0.73). Suzuki et al (2009) also found leptin correlated with s.c. fat (r . 0.72) and total fat (r .…”