Factors Affecting Growth Performance, Carcass Characteristics, Fatty Acid Profile Variation, and Iodine Value Prediction of Growing-Finishing Pigs

摘要

There were three objectives for this study: to quantify the impact of diet, sex, season, and market pull on fatty acid composition and iodine value of grow finish pigs. Develop equations for rapid and accurate prediction of iodine values of pork carcass to assess pork fat quality. Predict iodine value of two relevant adipose depots in growing-finishing pigs by near infrared reflectance spectroscopy to assess pork fat quality. A single experiment was conducted in a RCBD with two replications, utilizing crossbred pigs (n =480; initial BW = 48.6 +/- 6.7 kg) which were blocked by BW and sex. Treatments arranged in a 2 x 2 factorial with dietary fat source (TA and CO), and level of RAC inclusion (0 vs 10 mg/kg). Each treatment group consisted of 12 pens (6 barrow pens and 6 gilt pens) with 5 pigs per pen per replication. Pigs were harvested in 1 of 3 marketing pulls (d 56, 64, 76), in which the four heaviest pens per each treatment were removed. Fat tissue samples removed from the belly (posterior to the sternum, ventral edge of belly) and backfat (at the adjacent area of the first lumbar vertebra). Fatty acid profile was determined via gas chromatography (GC) and near infrared (NIR) spectroscopy. Chapter 1 observed that dietary fat supplementation did not affect (P > 0.05) live growth performance or carcass characteristics, while dietary RAC inclusion increased final BW, ADG, G:F, LMA, HCW, and FFLP. Total fatty acid (FA) concentrations of saturated FA (SFA), monounsaturated FA (MUFA), and MUFA:PUFA were higher (P < 0.01) in belly and back fat from pigs fed TA. Total polyunsaturated FA (PUFA) and the UFA:SFA concentrations in belly and back fat were higher (P 0.01) iodine value (IV) of belly and back fat depots at a greater magnitude then TA. Sex, season, and market pull also affected (P < 0.05) the concentrations of total SFA, PUFA, UFA:SFA and IV from belly and back fat depots. Increasing the degree of unsaturation of supplemental dietary fats negatively affected fat quality of growing-finishing pigs; while supplemental fat had the greatest effect on fat quality, the additional factors of sex, season, and market pull impacted fat quality in some measure. Single variable regression models utilizing dietary IVP (Loin BF: R2 = 0.84; Belly: R 2= 0.79) and C18:2, (Loin BF: R2 = 0.90; Belly: R 2= 0.87) had the highest coefficient of determination to predict iodine value of loin BF and belly fat sample sites. The inclusion of other live growth performance and carcass characteristic measures resulted in only a marginal improvement in R2. Pearson Correlation Coefficients between GC and NIR for IV between loin BF (r = 0.93; P < 0.001) and belly (r = 0.92; P< 0.001) fat depots, were highly correlated between determination methods. Similarly, Pearson Correlation Coefficients between loin BF and belly sample site locations for IV determined by GC (r = 0.88; P < 0.001) and NIR (r = 0.88; P < 0.001) were highly correlated suggest either location would be suitable for predicting IV. NIR calibration statistics for fatty acid proportions amongst fat depots were quite variable with R2 values ranging from 0.26 -- 0.96. Difference between fat depots was the largest contributor to the variation in the coefficient of determination, belly fat had comparatively lower R2 values and Ratio of Performance to Deviation (RPD) values generally < 1 when compared to loin BF. NIR calibration models were however, able accurately and precisely predict major FA constituents known to influence pork fat quality; C18:2n6, (Loin BF: R2 = 0.96, RPD = 5.31; Belly: R2= 0.91, RPD = 3.32), PUFA (Loin BF: R2 = 0.95, RPD = 4.68; Belly: R2= 0.87, RPD = 2.77), and IV (Loin BF: R2 = 0.93, RPD = 3.87; Belly: R2= 0.89, RPD = 3.04). The accuracy of NIR standard curves for IV loin BF and belly fat samples proved that NIR could be used to screen pork carcass fat quality and provide a rapid, cheap, non-destructive alternative to traditional IV determination methods of GC or titration.