Utilizing meta-analyses to generate prediction equations for pork carcass back, belly, and jowl fat iodine value
Iodine value (IV) is a measure of unsaturated fatty acids and is currently the industry standard for assessing pork fat quality. The objective of this meta-analysis was to use data from existing literature to generate equations to predict back, belly, and jowl fat IV of finishing pigs. The final database resulted in 24 papers with 169 observations for backfat IV, 21 papers with 124 observations for belly fat IV, and 29 papers with 197 observations for jowl fat IV. Some observations (back n=36, belly n=37, and jowl n=45) changed dietary fatty acid composition during the experiment (i.e. switching from higher to lower or lower to higher iodine value product diet), where initial diets (I) were defined as those fed before the change in diet composition and final diets (F) were defined as those fed after the change in diet composition. The predictor variables tested were divided into 5 groups: 1) diet fat composition (dietary percent C16:1, C18:1, C18:2, C18:3, EFA, and unsaturated fatty acids, and iodine value product) for both I and F diets; 2) duration of feeding of the I and F diets; 3) ME or NE content of the I and F diet; 4) performance criteria (initial BW, final BW, ADG, ADFI, and G:F); 5) carcass criteria (HCW and backfat thickness). PROC MIXED (SAS institute, Inc., Cary, NC) was used to develop regression equations, and experiment within paper was included as a random effect. Statistical significance for including terms in the models was determined at P<0.10. Evaluation of models with significant terms was then conducted based on the Bayesian Information Criterion (BIC), where the lowest BIC were preferred. Optimum equations to predict back (BIC=739), belly (BIC=558), and jowl (BIC=758) fat IV were: backfat IV =84.83+(6.87*I EFA)-(3.90*F EFA)-(0.12*I d)-(1.30*F d)-(0.11*I EFA*F d)+(0.048*F EFA*I d)+(0.12*F EFA*F d)-(0.0060*F NE)+(0.0005*F NE*F d)-(0.26*backfat depth); belly fat IV = 106.16+(6.21*I EFA)-(1.50*F d)-(0.11*I EFA*F d)-(0.012*I NE)+(0.00069*I NE*F d)-(0.18*HCW)-(0.25*BF); and jowl fat IV =85.50+(1.08*I EFA)+(0.87*F EFA)-(0.014*I d)-(0.050*F d)+(0.038*I EFA*I d)+(0.054*F EFA*F d)-(0.0066*I NE)+(0.071*I BW)-(2.19*ADFI)-(0.29*backfat depth). These regression equations may be used to predict the back, belly, and jowl fat IV of finishing pigs fed different diets.
Keywords: Iodine value, meta-analysis, pork quality