A. P. Schinckel

Myosin heavy chain isoforms account for variation in pork quality

The objective of this study was to determine the impact of myosin heavy chain (MyHC) isoforms (I, IIB, IIA and IIX) on pork quality traits of halothane (HAL)-negative (NN) and halothane-carrier (Nn) pigs. Gilts (n=32) were assigned to a 2×2 factorial of genetic population (GP) and slaughter weight (WT; 120 and 135 kg). Classical meat quality characteristics were collected and MyHC content was determined on muscle samples. Regression equations for pork quality and carcass composition traits were determined. Only I/IIB accounted for variation in drip loss of NN gilts (R(2)=0.18), while GP related to drip loss in Nn gilts (R(2)=0.70). Type I MyHC content explained variation in ultimate (24 h) muscle pH of NN gilts (R(2)=0.09), while I/IIB, I/IIX and IIB/IIX were significant for Nn gilts (R(2)=0.99). I/IIA, I/IIX, IIB/IIX and GP accounted for variation in Hunter Color a (redness) values of NN gilts (R(2)=0.69), while IIB, IIA, IIB/IIA and GP were significant for Nn gilts (R(2)=0.97). Overall, fiber type composition accounts for a larger proportion of variation in the quality traits of Nn compared to NN gilts.

Nonlinear Mixed Effects Model for Swine Growth

Abstract A mixed effects model version of a common swine growth function is introduced. This version, in which the mature BW of each pig is considered random, accounts for increasing variation with age and serial correlations across age that are common in serial BW growth data sets, thereby providing a much better fit and significantly smaller parameter SE. The inclusion of random effects also reduces the impact of selective sampling, which occurs when fast-growing pigs are removed for marketing, and provides a statistic (i.e., variance estimate) that describes the between-pig variation within a group. Comparisons between the fixed and mixed effects models are made using swine growth data consisting of 93 pigs with biweekly BW data from 54 to 138 d of age. In addition to a much better fit, the mixed effects model version is easily adaptable to stochastic modeling because only an additional random effect (i.e., mature BW) for each pig needs to be generated.

Early postmortem electrical stimulation simulates PSE pork development

Carcasses from 64 gilts were subjected to electrical stimulation (ES) at 3, 15, 25, 35, 45, and 55 min postmortem or were untreated (NS). Temperature and pH of longissimus muscles were recorded at 1, 7, 14, 20, 30, 40, 50, and 60 min, and 24 h postmortem. Muscle samples were collected at 1, 30 and 60 min, and 24 h for determining glycolytic metabolite concentrations. ES at 3, 15, and 25 min resulted in lower (P<0.05) muscle pH, but stimulation after 25 min had no effect on muscle pH. Likewise, ES prior to 25 min resulted in greater (P<0.05) muscle temperatures. Muscle lactate concentrations were greater (P<0.05) in carcasses stimulated before 45 min postmortem. Glucose 6-phosphate concentration decreased (P<0.05) during the first hr postmortem and increased (P<0.05) thereafter. ES of carcasses at 45 and 55 min resulted in higher (P<0.05) concentrations of muscle glucose 6-phosphate at 24 h compared with NS and early-stimulated carcasses. Muscle glycogen concentrations at 30 min in carcasses stimulated at 3, 15 and 25 min were lower (P<0.05) than NS carcasses. Carcasses stimulated at 3 and 15 min exhibited lower (P<0.05) concentrations of muscle glycogen at 60 min than NS carcasses. Carcasses stimulated at 3 and 15 min postmortem exhibited lower (P<0.05) color and firmness scores, while ES at 3 and 25 min postmortem resulted in lower (P<0.05) water holding capacity. ES had no significant effect on CIE L(∗), a(∗), b(∗), or 24 h muscle pH. These data show that ES of pork carcasses during the first 25 min postmortem creates PSE-like quality characteristics and suggest that ES is a potential model for studying pork quality development.

Evaluation of Alternative Nonlinear Mixed Effects Models of Swine Growth

Abstract Alternative versions of a common three-parameter nonlinear growth function were evaluated on two groups of gilts. Gilts were randomly assigned to be reared under all-in, all-out (AIAO; n = 96) or continuous flow (CF) management (n = 96). The addition of a single random effect, in which the mature BW of each pig varies, provided a substantially better fit and smaller parameter standard errors. This model predicts a constant coefficient of variation between pigs. The addition of a second random effect further improved the likelihood statistics and reduced the residual standard deviation, although the impact was much smaller. The inclusion of the second random effect accounts for different patterns of growth between pigs. Variations in the growth patterns allow greater fleiibility to describe the underlying variance/covariance structure of the serial live BW. For all miied effects models, the mean and approiimate variation in age required for pigs to reach a specific BW can be predicted. After 104 d of age, the growth of CF gilts declined more rapidly, and the standard deviation in days required to reach specific target BW (TBW) (110, 120, or 130 kg) increased more rapidly than for the AIAO gilts. These models are also easily adaptable to stochastic modeling.

Economic Replacement of a Heterogeneous Herd

A model was developed to determine the optimal slaughter weights of pigs with heterogeneous growth raised in a 1,000 head barn and marketed in truckload groups. Under commonly used revenue schemes, which include discounts for weight and leanness, the optimal strategy was to market one or two truckloads of the heaviest animals, to wait several days, and then to market the rest of the herd. This multiple marketing strategy allows the producer to avoid some sort losses for heavy animals, but only modestly extends the grow/finish period, reflecting the dominance of the opportunity cost of facilities in the herd replacement decision.

Development of a Stochastic Pig Compositional Growth Model

Abstract A stochastic pig compositional growth model was developed using mixed model nonlinear functions. Serial BW measurements were fitted to mixed model nonlinear equations with three parameters and two random effects. Empty body protein mass ( EBPRO ) data were predicted from serial real-time ultrasound and BW measurements. Predicted EBPRO data were fitted to a nonlinear function of predicted BW ( PBW ) with one random effect: EBPRO = C (¦(PBW)) + cp i (¦(PBW)) D , where ¦(PBW) = (1 - exp (b 0 + b 1 PBW + b 2 (PBW) 2 ), C and D are fixed parameters, and cp i is a random effect. The model also accounts for the relationship among the random effects for BW growth and cp i . Daily lipid accretion was predicted from genetic population-sex specific relationships between BW, EBPRO, and empty body lipid mass: empty BW = 0.93 BW and empty BW = a 1 EBPRO b1 + a 2 (empty body lipid mass) b2 . The model predicts a BW growth curve and daily compositional growth rate for carcass fat-free lean, carcass fat tissue, EBPRO, and empty body lipid. To reproduce the total variance, the residual variance of each variable was produced by multiplying the residual standard deviation of each prediction equation by a value sampled from a standard normal distribution. The stochastic model can be used to develop strategies to target a specified mean and distribution of carcass composition end points.

Physiological response to acute endotoxemia in swine: effect of genotype on energy metabolites and leptin☆ ☆

Certain high lean gain swine genotypes have greater sensitivity to pathogen and nonpathogen stressors evident by reduced productivity and increased mortality during disease stress or in suboptimal production environments. Saline (control) and an immunologic challenge (LPS; 25 microg lipopolysaccharide/kg BW) were administered to three genetic populations (each pig used as its own control): high lean (H), moderate lean terminal cross (MT), and moderate lean maternal cross (MM). LPS induced anorexia, and significantly increased body temperature and circulating TNF-alpha, cortisol, and NEFA in all genotypes (P < 0.0004). LPS reduced circulating glucose, insulin, and IGF-1 in all genotypes (P < 0.05). The LPS-induced hypoglycemia was significantly greater in MM versus MT and H pigs (P < 0.03). The hypoinsulinemia was significantly greater in MM versus H pigs (P < 0.02). MM pigs recovered from hypoinsulinemia slower than MT pigs (P < 0.03). Control insulin was higher in H versus MT pigs (P < 0.08), but relative to basal, the insulin response to LPS was similar. Plasma haptoglobin response to LPS was lower for MM versus MT and H pigs (P < 0.02), and tended to be lower in MT versus H pigs (P < 0.09). LPS treatment caused similar decreases in plasma IGF-1 concentrations among genotypes. Ten hours after LPS treatment, leptin mRNA abundance in adipose tissue was significantly reduced (relative to control) in MM and H pigs (P < 0.02) but not in MT pigs (P > 0.05). Physiological differences in leptin, a potent regulator of food intake and energy metabolism, may be important factors in the genetic variation in sensitivity to environmental stress.

The effect of genotype and sex on the patterns of protein accretion in pigs

Protein accretion curves were derived using food intake, growth and body composition data from a total of 320 pigs, which comprised castrated males and gilts from five genotypes. The 32 pigs from each genotype/sex subclass were offered ad libitum a series of isoenergetic diets (13·8 MJ metabolizable energy per kg) designed to provide a non-limiting intake of nutrients and to allow maximum protein deposition rates. Four pigs from each subclass weren slaughtered at each of the live weights (kg) 25, 44, 65, 85, 100, 115, 130 and 150. Daily food intake (dF/dt) was described as an increasing exponential function of age (t), live weight (W) as an increasing exponential function of cumulative food consumed (F), and protein weight (Pr) as an allometric function of live weight (W). The rate of protein accretion in the body of pigs [d(Pr)/dt] was calculated as d(Pr)/dt = (dF/dt).(dW/dF).(dPr)/dW). Bootstrap procedures were used to estimate standard errors for the food intake, growth and compositional parameters and to obtain the confidence bands for the dependent variables (dF/dt, W, Pr and d(Pt)/dt). Protein accretion rate as a function of live weight was curvilinear, increasing to a maximum, then decreasing with increasing live weight. There were significant differences between subclasses in the maximum rate of protein accretion, although there was no relationship between this rate and the live weight, stage of maturity, or age at which maximum protein accretion occurred. Describing protein accretion as a multiplicative function of food intake, food efficiency and the partitioning of nutrients in the body allowed changes in the magnitude and shape of the protein accretion curve to be ascribed to one, or a combination, of the above mechanisms.

Optimal Hog Slaughter Weights Under Alternative Pricing Systems

Three hog genotypes are simulated to determine how producer profits, economically optimal slaughter weights, and carcass component weights change under three pricing models. Live weight pricing pays more for the fatter barrows whereas a three component (separate payments for fat, lean, and byproducts) and six component (separate payments for major primal cuts, other lean, fat, and byproducts) pricing system pay more for the leaner gilts. Implications for selection of genetic stock and pricing system are presented.

Feeding conjugated linoleic acid partially recovers carcass quality in pigs fed dried corn distillers grains with solubles

Dried corn distillers grains with solubles (DDGS) fed to swine may adversely affect carcass quality due to the high concentration of unsaturated fat. Feeding CLA enhances pork quality when unsaturated fat is contained in the diet. The effects of CLA on growth and pork quality were evaluated in pigs fed DDGS. Diets containing 0, 20, or 40% DDGS were fed to pigs beginning 30 d before slaughter. At 10 d before slaughter, one-half of each DDGS treatment group was fed 0.6% CLA or 1% choice white grease. Carcass data, liver- and backfat-samples were collected at slaughter. Longissimus muscle area, 10th-rib back-fat depth, last rib midline backfat depth, LM color, marbling, firmness and drip loss, and bacon collagen content were not altered by DDGS or CLA. Outer layer backfat iodine values were increased (P <or= 0.05) with DDGS feeding and were 65.07, 69.75, and 74.25 for 0, 20, and 40% DDGS, respectively. Addition of CLA decreased (P <or= 0.05) outer layer backfat iodine values from 71.11 to 68.31. Diets containing DDGS decreased (P <or= 0.05) percent lean tissue contained in bacon from 48% for controls to 38% for pigs fed 40%. Abundance of fatty acid synthase, carnitine palmitoyl transferase Ia, acetyl-CoA-carboxylase, stearoyl-CoA desaturase, and glycerol-3-phosphate dehydrogenase mRNA in adipose or liver were not different (P > 0.05) for pigs fed DDGS. Feeding CLA decreased (P <or= 0.05) the Delta(9) de-saturase index in adipose tissue. The data indicate that decreased carcass firmness with DDGS feeding is not reflected by changes in lipogenic gene expression. Feeding 20% or more DDGS to finishing swine decreases bacon leanness, but inclusion of 0.6% CLA in the finishing diet can partially reverse these effects.