Characterizing the amount and variability of intramuscular fat deposition throughout pork loins using barrows and gilts from two sire lines

Abstract

The objective was to determine the amount and variability of intramuscular fat (IMF) in a pork loin attributable to anatomical chop location, sex, and sire line. Pigs were sired by commercially available terminal Duroc boars selected for meat quality (MQ; n = 96) or lean growth (LG; n = 96) and equally split between barrows and gilts. After slaughter and fabrication, bone-in chops were removed from four locations of each left-side loin (A = 6th rib, B = 10th rib, C = last rib, and D = 4th lumbar vertebrae). An adjacent pair of chops from each location was collected and evaluated for visual color and marbling, subjective firmness, moisture and extractable lipid (IMF) (anterior chop), and Warner–Bratzler shear force (posterior chop). Data were analyzed using the MIXED procedure of SAS as a split-plot design. Homogeneity of variances was tested on raw data using Levene’s test of the GLM procedure and found to be heterogeneous. Thus, a two-variance model was fit using the REPEATED statement of the MIXED procedure, grouped by pig. The mivque(0) option of the VARCOMP procedure was used to calculate the proportion of variability that each factor contributed to the total variance. Barrows (3.64%) produced chops with greater (P < 0.01) IMF content than gilts (3.20%), and barrows (2.14) had greater (P < 0.01) IMF variability than gilts (1.23). Chops from MQ pigs (4.02%) exhibited greater (P < 0.01) IMF content than LG (2.82%), and MQ (1.76) had greater IMF variability (P < 0.01) than LG pigs (0.97). Chops from locations A (3.80%) and D (3.77%) had greater IMF than B (3.34%; P < 0.01), and A, B, and D had greater IMF than C (2.77%; P < 0.01). Variances of IMF also differed (A = 1.44, B = 1.59, C = 1.05, and D = 2.18; P = 0.01) across chop locations. Of the variability in IMF, 33.0% was attributed to sire line, 10.16% to chop location, and 4.01% to sex, with 52.83% not accounted for by these three factors. Location A chops were the most (P < 0.01) tender (2.57 kg) and C chops the least (P < 0.01) tender (2.93 kg), while B and D chops were intermediate and not different from each other. No differences in variability (P = 0.40) of tenderness were observed among chop locations (A = 0.31, kg B = 0.24 kg, C = 0.24 kg, and D = 0.23 kg). These results demonstrated that variability in tenderness values did not reflect the variability of IMF. In conclusion, chop location, sex, and sire line all contribute to the amount and variability of pork loin marbling.

Combining pig genetic and feeding strategies improves the sensory, nutritional and technological quality of pork in the context of relocation of feed resources

“…With this finding, and due to the well described lower IMF content in females compared to castrated males (Schwob, Lebret, & Louveau, 2020), we cannot argue that the use of females in the present study may explain the observed differences. Our findings rather illustrate the high diversity between Duroc lines for this trait (Redifer, Beever, Stahl, Boler, & Dilger, 2020;Schwob et al, 2020). The R feeding regimen did not affect muscle protein and water contents as observed in growing-finishing Large White pigs with increasing dietary intake of n-3 PUFA (Belmonte et al, 2021).…”

Evaluation of Improvest effects on production parameters of gilts from two different genetic sire lines

“…In general, several traits that barrow carcasses exhibit are preferred to that of gilt carcasses, in particular when fat deposition and fat quality are sorting criteria for merchandized products such as loins and bellies ( Boler et al., 2014 ; Kyle et al., 2014 ). All the while, Pietrain-sired pigs tend to have less backfat and more lean muscle percentage compared to Duroc-sired pigs, making the comparison of the two different genetic groups of pigs in this study of interest ( Kušec et al., 2004 ; Morales et al., 2013 ; Redifer et al., 2020 ). In our study, barrows from both genetic lines showed the greatest amount of backfat, while untreated (i.e., CON) gilts from both genetic lines showed the lowest amount of backfat.…”

Evaluation of the variability of instruments used in meat color assessments

“…Using a C illuminant decreased lightness and increased yellowness measurements in loins and Boston measured in the exact same area using both machines, and although measurements from each machine were made on the same loin, they may not have been evaluated in the exact same location. Redifer et al (2020) reported that even small distances between loin locations can cause differences in color and marbling. Additionally, 3 measurements per machine were observed on each loin and averaged in the university study, decreasing variability contributed by measurement position.…”