Current methods to adjust pig performance data to a constant BW or age assume linear relationships between the growth of the measurement and either age or BW. Serial BW and ultrasonic measurements from a set of gilts were used to provide an example of the development of alternative methods to adjust pig performance data. Each pig was weighed at approximately 125, 138 153, 167, and 174 d of age. Ultrasonic backfat depth and loin depth measurements were collected at each weigh day on approximately one-half of the gilts. The BW data were fitted to a mixed model generalized Michaelis-Menten (GMM) function with one pig-specific random effect for mature BW. By including each pig’s random effect, the pig’s predicted age to achieve target BW was estimated. An allometric equation Y = (1 + ai) A BWBwith a pig-specific random effect (ai) provided the best fit of the ultrasonic data to BW. An alternative approach to adjust pig growth or measurement data using mixed model nonlinear equations was suggested. The pig’s actual data were used to solve for its specific random effect. Then, using the nonlinear equation and the pig’s random effect, the pig’s measurement at the target age or BW can be estimated. This alternative approach may better predict the mean and variances of each pig’s growth and better adjust pig performance data.

Effects of ractopamine hydrochloride (RAC) on carcass parameters in heavy weight (133.24 +/- 8.07 kg) finishing pigs (n = 278) given amino acid fortified (AA) or 16% crude protein (CP) diets were evaluated. A total of seven experimental diets were formulated; RAC was added at 0, 5 and 20 ppm to the 16% CP diets (CPO, CP5 and CP20, respectively) and at 0, 5, 10 and 20 ppm to the AA fortified diets (AA0, AA5, AA10 and AA20, respectively). Carcass, tenderloin, and ham weights were heavier (P < 0.05) for RAC AA diets vs. AAO. Loin weight was heavier (P < 0.05) for AA20 vs. AAO and CP20 vs. CPO. No differences (P > 0.05) were observed for color or firmness scores. Carcass muscle score, ham weight and protein% were greater (P < 0.05) for RAC diets. Moisture was greater (P < 0.05) and fat was lower (P < 0.05) for AA5 and AA20 vs. AAO and CP5 and CP20 vs. CPO. Feeding RAC to late finishing swine increases carcass yields and protein% with lower fat% for pigs weighing up to 136 kg. (C) 2008 Elsevier Ltd. All rights reserved.

ABSTRACT The objective of this study was to determine the effects of loin muscle location on glycolytic potential (GP) and fresh pork quality traits. Seven sections (5‐cm thick) from approximately between the eighth rib and fourth lumbar vertebra were evaluated. Numerous quality measurements were taken within each section. Ultimate pH was similar (P > 0.05) at all locations. Drip loss decreased (P < 0.01), while subjective firmness and color scores improved (P < 0.01) toward the posterior end of the loin. Minolta L* values (Minolta, Osaka, Japan) were highest (P < 0.01) in the anterior sections. Intramuscular fat was lower, but shear force and GP were higher in the middle sections than at the extremities (P < 0.01). In conclusion, GP and pork quality traits vary throughout the longissimus dorsi. However, differences in GP among sections were of low magnitude, and ultimate pH was unaffected by loin location. For studies that require multiple measurements of GP, samples should be taken in the region of the longissimus that yielded similar values, i.e., between the 10th rib and the third lumbar vertebra.

Blood acid-base responses to handling were evaluated in slaughter weight pigs fed diets supplemented with L-carnitine and fat. The study was carried out as a randomized block design with a 2 x 2 factorial arrangement of treatments: 1) dietary L-carnitine supplementation (0 vs. 150 ppm, as-fed basis); and 2) dietary fat supplementation (0 vs. 5%, as-fed basis). Sixty pigs (91.1 +/- 5.14 kg BW) were housed in mixed-gender groups of five and had ad libitum access to test diets (0.68% true ileal digestible lysine, 3,340 kcal of ME/kg, as-fed basis) for 3 wk. At the end of the feeding period (110.3 +/- 7.52 kg BW), pigs were subjected to a standard handling procedure, which consisted of moving individual animals through a facility (12.2 m long x 0.91 m wide) for eight laps (up and down the facility), using electric prods (two times per lap). There was no interaction between dietary L-carnitine and fat supplementation for any measurement. Pigs fed 150 ppm of supplemental L-carnitine had lower baseline blood glucose (P < 0.05) and higher baseline blood lactate (P < 0.05) concentrations than the nonsupplemented pigs. After handling, pigs fed L-carnitine-supplemented diets had a higher (P < 0.05) blood pH and showed a smaller (P < 0.05) decrease in blood pH and base excess than those fed the nonsupplemental diets. Baseline plasma FFA concentrations were higher (P < 0.01) in pigs fed the 5% fat diet. After the handling procedure, blood glucose, lactate, and plasma FFA were higher (P < 0.05) in pigs fed the 5 vs. 0% fat diets, but blood pH, bicarbonate, and base excess were not affected by dietary fat. The handling procedure decreased (P < 0.01) blood pH, bicarbonate, base excess, and total carbon dioxide and increased (P < 0.01) blood lactate, partial pressure of oxygen, and glucose, and also increased (P < 0.01) rectal temperature. Free fatty acid concentrations were increased by handling in pigs fed both 0 and 5% fat and 150 ppm L-carnitine. In conclusion, dietary L-carnitine supplementation at the level and for the feeding period evaluated in the current study had a relatively small but positive effect on decreasing blood pH changes in finishing pigs submitted to handling stress; however, dietary fat supplementation had little effect on blood acid-base balance.

ABSTRACT Pigs from four commercial packing facilities were utilized to characterize the impact of downer pigs on meat quality and the impact of respiratory health on downer pigs. Lungs of downer pigs were evaluated for pneumonia and the pH of the longissimus was measured at approximately 45 min postmortem on 246 carcasses. At approximately 24 h postmortem, subjective color, marbling, firmness of the loin, carcass conformation, gender, objective loin color and ultimate pH of the longissimus were determined on 229 carcasses. Muscle score, 45 min pH and lung score averaged 2.14, 6.32 and 1.67, respectively. Subjective color, marbling, firmness, Minolta L‐value, pH and drip loss averaged 3.75, 2.72, 3.16, 45.72, 6.00 and 1.91%, respectively. Downer pigs tended to produce pork that was dark in color with a relatively high ultimate pH and low drip loss. Virtually no relationship was observed between downer pigs and lung score.

The objective of this study was to determine the effect of live weight on the plasma acid-base response of pigs subjected to various handling intensities. Eighty pigs (equal numbers of barrows and gilts) were used in a completely randomized block design with a 2 x 2 x 2 factorial arrangement of the following treatments: 1) live weight (light [104 kg] vs. heavy [128 kg]), 2) handling intensity (low vs. high), and 3) gender (barrows vs. gilts). Before the handling test, pigs were weighed, venous blood samples were taken to establish baseline levels, and rectal temperature was measured. Pigs were allowed to rest for 2 h before being subjected to the handling treatments, which consisted of moving the pigs through a course (12.2 m long x 0.91 m wide), for a total of eight laps. Animals on the high-intensity treatment were moved rapidly through the course and subjected to a total of 16 single shocks (two shocks per lap) with an electric livestock goad, whereas pigs on the low-intensity treatment were moved at their own pace using a moving panel and a paddle. Rectal temperature and a venous blood sample were taken immediately after handling and at 2 h after handling. Blood plasma was assayed for pH, partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), saturated oxygen (SO2), total carbon dioxide (TCO2), bicarbonate (HCO3), base excess, and lactate. Live weight had no effect on the baseline measurements. After handling, light pigs had higher (P < 0.05) blood SO2 (65.6 vs. 57.2+/-2.80%) and showed a greater (P < 0.05) increase in PO2 from baseline to post-handling than heavy pigs (15.6 vs. 8.3+/-2.63 mmHg). Post-handling, pigs on the high- compared with the low-intensity handling treatment had greater (P < 0.001) lactate (19.1 vs. 4.9+/-0.56 mmol/L) and PO2 (51.6 vs. 36.5+/-2.44 mmHg) with lower (P < 0.001) TCO2 (18.6 vs. 34.7+/-0.64 mmol/L), pH (7.02 vs. 7.36+/-0.015), HCO3 (16.7 vs. 33.0+/-0.62 mmol/L), and base excess (-14.2 vs. 7.5+/-0.75) values. There were no effects of gender on blood measurements or rectal temperatures. Results from this study highlight a major effect of pig handling intensity, a limited effect of live weight, and no effect of gender on blood acid-base responses to handling.

The relationships between glycolytic potential and growth performance, carcass traits, and pork quality were investigated in a group of 72 pigs from the same genetic line. Glycolytic potential (GP) was determined on live-animal biopsy samples and postmortem samples taken from the longissimus muscle, and free glucose concentration was measured on the exudate from the longissimus muscle taken postmortem. The mean live-animal and postmortem GP and free glucose values were 201.6 micromol/g (range = 113.8 to 301.1), 149.8 micromol/g (range = 91.0 to 270.5) and 110.1 mg/dL (range = 30.0 to 406.0), respectively. Correlations between live-animal and postmortem GP and free glucose ranged from 0.47 to 0.70; however, all three measures were weakly related to growth and carcass traits (r = 0.03 to -0.22; P > 0.05). Correlations of GP and free glucose values with fresh pork quality measurements were moderate (r = 0.23 [P < 0.05] to -0.63 [P < 0.001]). Regression analysis suggested that a one standard deviation increase in live-animal and postmortem GP and free glucose resulted in an increase in L* values (0.99, 1.32, and 2.05, respectively) and drip loss (0.85, 1.10, and 1.39 percentage units, respectively), as well as a decrease in ultimate pH (0.05, 0.11, and 0.16, respectively). Correlations between GP and cooking loss and tenderness and juiciness scores ranged between 0.16 (P > 0.05) to 0.34 (P < 0.01). Free glucose concentration showed no relationship (P > 0.05) with cooking loss, tenderness, and juiciness. Regression analysis suggested that a one standard deviation increase in live-animal and postmortem GP increased cooking loss (1.26% and 1.65%, respectively) and would improve taste panel tenderness (0.54 and 0.44, respectively) and juiciness (0.40 and 0.48, respectively) scores. Increasing GP and free glucose was also associated with decreased longissimus fat and protein, and increased moisture contents (r = 0.14 [P > 0.05] to -0.45 [P < 0.001]). Overall, relationships with fresh meat quality characteristics were stronger for free glucose values than either live-animal or postmortem GP. Results from this study indicate that decreasing longissimus GP and free glucose concentrations may improve pork color and water-holding capacity.

Loss of animals during transport to the slaughterhouse (dead on arrival and downers) and poor meat quality are interrelated issues resulting in significant losses to all sectors of the pig industry. Historically, a major cause of these losses could be attributed to the halothane gene, however, substantial losses also can occur in halothane negative population (Channon et al., 2000; Miller et al., 2000). Occurrence of downers is associated with stress leading to high blood lactate and metabolic acidosis (Ivers et al., 2002). This metabolic condition also can compromise meat quality when it occurs immediately before slaughter. Some of the factors associated with stress and elevations in blood lactate are physical exercise (van den Hende et al., 1970), electric stimulation (Bickhardt and Wirtz, 1987), or both (Bertol et al., 2002), which are factors commonly experienced by pigs during handling. Therefore, approaches that reduce metabolic acidosis during physical and emotional stress are practically important. Reduction in lactate production by reducing glucose and increasing fatty acid utilization as the energy substrate could be one way to address this problem.

A total of 736 pigs was used in a study with a 2 x 2 x 2 factorial arrangement to investigate the effects of and interactions between sire line (Line A vs. B), floor space (unrestricted vs. restricted), and gender (barrow vs. gilt) on growth performance, BW, and protein and estimated lipid accretion curves from 40 to 120 kg of BW. Pigs were by eight Line-A and nine Line-B sires mated with PIC C22 dams. Line A was of Pietrain ancestry and Line B was a synthetic line. The unrestricted floor space treatment consisted of small groups (four pigs) with 0.93 m2/pig of floor space for the entire grow-finish period. Pigs in the restricted floor space were in larger groups (12 pigs) with 0.37 and 0.56 m2/pig of floor space for the grower and finisher phases, respectively. Pigs were given ad libitum access to a three-phase dietary program, and one and three nipple waterers were available in the groups of 4 and 12 pigs, respectively. No sire line x floor space interactions were found for any of the traits measured. Line A pigs grew more slowly (50 g/d, P < 0.05), took longer (4.1 d, P < 0.05) to reach harvest weight (120.3 kg), and had similar feed intakes, but a lower gain:feed ratio (2.8%, P < 0.05) than Line B pigs. Line A pigs had greater longissimus muscle depth (P < 0.05) and estimated protein accretion rate (P < 0.05) than Line B pigs, but Line A and Line B pigs had a similar estimated percentage of lipid-free soft tissue. Pigs reared in the restricted floor space grew more slowly (105 g/d, P < 0.05) and consumed less feed (280 g/d, P < 0.05) but had a similar (P > 0.05) gain:feed ratio to pigs reared in the unrestricted floor space. Pigs reared in the unrestricted floor space had greater (P < 0.05) predicted protein and lipid accretion rates throughout the growth period than pigs reared in the restricted floor space. Differences between genders for growth traits and carcass measurements were in agreement with previous research. The differences in growth performance, carcass measures, and compositional growth curves between these two sire lines were similar in the two floor spaces.

A total of 192 pigs were utilized in a 2×3×3 factorial arrangement with an additional control treatment. The treatments were: (1) magnesium level (1.6 vs. 3.2 g of magnesium pig(-1) day(-1)); (2) magnesium source (sulfate vs. proprionate vs. proteinate); (3) feeding duration (5 vs. 2 vs. 1 day), and a control (no supplementary magnesium). Minolta L(∗) values were lower (P⩽0.05), indicating darker muscle color, for pigs supplemented with 1.6 g magnesium pig(-1) day(-1) compared to the controls while pigs on the 3.2 g magnesium level were intermediate between these two treatments. Animals on the 1 day treatment had a higher (P⩽0.05) ultimate pH and lower (P⩽0.05) Minolta L(∗) compared to those on the 2 days and control treatments, while 5 days pigs were intermediate and had lower L(∗) values compared to the controls. The sulfate and proteinate treatments produced pork with the lower (P⩽0.05) Minolta L(∗) values compared to the controls. Pigs fed the sulfate diet had a lower (P⩽0.05) drip loss compared to those on the control treatment. Results from this study suggest that the lowest level (1.6 g magnesium pig(-1) day(-1)) and the shortest time of supplementation (1 day) may be effective in improving pork color and water-holding capacity.

Pale soft exudative pork (PSE) is a major problem affecting swine industries worldwide that results in significant economic loss because it reduces processing and saleable product yields. The PSE condition results from a rapid rate of muscle glycolysis early postmortem and a rapid drop in muscle pH while the temperature of the carcass is still high. Stress prior to slaughter can increase the rate of glycolysis and postmortem acidification. Blood acid-base has been used as an indicator of stress in pigs. The objective of this experiment was to investigate the relationship between blood acid-base status at slaughter and fresh meat quality in pigs.

The objective of this study was to compare the carcass and meat quality of pigs of two sire lines (A vs B) reared in either a spacious or crowded environment. A total of 128 pigs (barrows and gilts) were used in the study. Animals were slaughtered at 120 kg live weight. Dressing percentage was greater for line A in the spacious but not the crowded environment and line A had a greater loin eye area than line B. Compared to line B, the longissimus from line A had lower pH, higher L* and b* values, and was judged to be paler and softer with a lower marbling fat content. Longissimus L* values were lower for pigs reared in the crowded compared to the spacious environment. Longissimus drip loss was greater for line A compared to line B in the spacious but not the crowded environment. This study highlights genetic differences in pork quality and suggests rearing environment effects that warrant further study.

Introduction There has been limited research carried out on the effects of environmental factors such as group size and crowding on carcass and meat quality characteristics in pigs. A number of studies investigating the effects of rearing environment on carcass and meat quality traits have compared outdoor versus indoor rearing systems and have shown variable results. Pigs reared outdoors have been reported to have darker meat color and no difference in ultimate pH when compared to confinement reared pigs (Wariss et al., 1983). Enfalt et al. (1996) showed that pigs reared in confinement had higher ultimate pH and marbling and lower drip loss than pigs reared outdoors. Other studies have shown no effect of rearing environment on these traits (van der Wal et al., 1993).

The objective of this study was to compare the effects of longissimus glycolytic potential (GP) and of time of feeding of supplemental magnesium sulfate heptahydrate on carcass and pork quality traits. The study was carried out in a 2 x 2 x 4 factorial arrangement; the treatments were sex (castrate vs gilt), GP (Low [normal] vs High), and time of feeding of magnesium sulfate-fortified diets (0 [control] vs 2 vs 3 vs 5 d prior to slaughter). Glycolytic potential was determined on a biopsy sample of longissimus from the live animal prior to the start of the study. A total of 144 pigs were allotted to the feeding-time treatments on the basis of sex (castrate and gilt), weight, and GP. Pigs were placed in individual pens and had free access to water. Prior to the start of the study, pigs were given ad libitum access to a standard finisher diet. During the study, animals were fed at a fixed level of 2.75 kg of a standard finisher diet/day; the fortified diet contained 3.2 g/d of additional magnesium. At the end of the feeding period, animals were transported to a commercial packing facility and slaughtered within 15 min of arrival. Fresh meat quality was measured on the longissimus. There were no treatment interactions. Carcass traits were similar across time of feeding treatments. Backfat thickness at the last lumbar vertebra and 10th rib were lower (P < 0 .05) for High than for Low GP pigs. High GP pigs had lower ultimate pH (P < 0.001) and higher drip (P < 0.05) and purge loss (P < 0.01) than Low GP pigs. Drip loss was reduced (P < 0.05) for pigs fed the magnesium-fortified diet for 5 and 2 but not for 3 d compared to controls (8.98, 7.29, 7.89, and 7.41 for the 0-, 2-, 3-, and 5-d treatments, respectively, SEM 0.447). Purge loss was similar for all of the time of feeding treatments. Longissimus L* values were lower (P < 0.05) for the 2-d treatment than for the controls. Results from this study suggest an inconsistent effect of short-term feeding of magnesium sulfate on muscle color and drip loss in pigs with both Low (normal) and High GP.

Introduction There have been numerous studies reporting the differences in performance levels and carcass characteristics between contrasting breeds and lines of pigs. Additionally, there is also a body of literature reporting that increased group size and reduced floor space allowance (crowding) results in reduced feed intakes and growth rates (Edmonds et al., 1998; Hyun et al., 1998). It is well known that the animal’s environment dictates the level to which it will express its genetic potential. Thus, the concept of genotype x environmental interactions (G x E) becomes important. Merks (1986), defined a G x E as a change in the relative performance of two or more genotypes measured in two or more environments. Several researchers have shown that genotype x environmental interactions may exist in swine populations (Bidanel and Ducos, 1996; Merks, 1989). As commercial producers continue to try new techniques to increase the efficient use of their facilities such as large group sizes and increased stocking densities, the presence of genotype x environmental interactions may become more important. The objective of this study was to investigate the interaction between genetic growth potential and rearing environment.

Forty-eight growing-finishing pigs were used in a split-plot design with a 2×2 factorial arrangement of treatments to investigate the effect of sire line and sex (castrates and gilts) on feeding patterns. Sire line A was of Pietrain ancestry and sire line B was a synthetic line that included Large White, Landrace, Duroc, and Pietrain. Sires from line A (n=8) and line B (n=9) were mated with PIC Camborough 22 females. Growth performance and feeding patterns of the progeny were measured from 40.2±2.04 to 120.0±2.85 kg body weight (BW). Pigs were housed in groups of eight, with two pigs from each line×sex subclass in each pen, at a floor space allowance of 0.9 m2 per pig. Feeding patterns were monitored by a computerized feed intake recording equipment (FIRE) system. Line B progeny had higher growth rates (1036 versus 956 g per day, S.E.=15, P<0.01), higher feed intakes (2657 versus 2470 g per day, S.E.=61.2, P<0.05), but similar gain:feed ratios, as compared to the progeny of line A. Line B pigs tended to have smaller loin-eye depths (P<0.10), and had greater lean growth rates (P<0.01) than line A pigs. Line B pigs, compared to line A pigs, had a greater feed intake per visit (207 versus 172 g, S.E.=9.9, P<0.05), and a higher feed consumption rate (36.7 versus 28.7 g/min, S.E.=2.41, P<0.05). Line B pigs tended to have lower feeder occupation times per day than line A pigs (P<0.10). There were no differences between the two sire lines for number of feeder visits or feeder occupation time per visit (P>0.10). Castrates had higher growth rates (P<0.01) and feed intakes (P<0.001), lower gain:feed ratios (P<0.01), but similar (P>0.05) feeding patterns compared to gilts. Feeding patterns showed significant changes with increasing BW: number of feeder visits and feeder occupation time per visit, and per day decreased linearly, while feed intake per visit and feed consumption rate increased linearly with increasing pig BW. The rates of change in a number of feeding pattern traits differed (P<0.05) between the two genetic lines. The results of this study highlight the influence of genetic ancestry and, particularly, BW on growth performance and feeding patterns in growing-finishing pigs.

Crossbred pigs (n = 1,400) were used to evaluate the effect of group size (25 vs 50 vs 100 pigs/pen) in a wean-to-finish production system on growth performance and carcass measures. Pigs were weaned at 17 d (range = 15 to 19) of age with a mean initial BW of 5.9 +/- 0.02 kg and taken to a final mean pen weight of 116 +/- 0.9 kg. A 10-phase dietary regimen was used, and pigs had free access to feed and water. Feeder-trough space (4.3 cm/pig) and floor-area allowance (0.68 m2/pig) were the same for all group sizes. Compared to groups of 25, pigs in groups of 50 and 100 animals were lighter (P < 0.001) at the end of wk 8 after weaning and had lower (3%, P < 0.01) ADG and gain:feed (G/F) but similar (P > 0.05) ADFI during the first 8 wk of the study. At the end of the study, pig weight and the coefficient of variation in pig weight within a pen were similar (P > 0.05) across group sizes. During the period from 8 wk after weaning to the end of the study, pigs in groups of 100 compared to 50 animals had greater (3%, P < 0.01) ADG, and pigs in groups of 25 were intermediate for ADG. Average daily feed intake during this period was similar (P > 0.05) for all group sizes; however, G/F was greater (3%, P < 0.01) for groups of 100 compared to 25 or 50 animals. For the overall study period, ADG, ADFI, and G/F from weaning to slaughter weight were similar across group sizes (P > 0.05; 655, 648, and 658 g; 1,759, 1,755, and 1,759 g; and 0.37, 0.37, and 0.37; for ADG, ADFI, and G/F, respectively, for groups of 25, 50, and 100 pigs, respectively). Mortality was similar (P > 0.05) across group sizes; however, morbidity (pigs removed due to poor health or injury) was higher in groups of 25 pigs compared to the other two group sizes (7.0, 3.5, and 3.9% for groups of 25, 50, and 100, respectively; P < 0.05). Group-size treatment did not affect (P > 0.05) carcass dressing percentage, backfat thickness, or loin-eye depth. In summary, growth performance from weaning to market weight was not affected by group size.

The objective of this study was to determine the effects of the Halothane (N) and Rendement Napole (RN) genes on carcass and meat quality characteristics in pigs. Halothane and RN carrier (Nn/RN- rn+) Hampshire boars (n = 4) were mated to dams that were homozygous for the normal allele of both genes (NN/rn+ rn+) to produce progeny of four genotypes: 1, NN/rn+ rn+ (n = 31); 2, Nn/rn+ rn+ (n = 27); 3, NN/RN- rn+) (n = 30); and 4, Nn/RN- rn+ (n = 23). A DNA test was used to determine Halothane genotype, and longissimus glycolytic potential was used to predict the RN genotype. Pigs were reared under standard conditions to approximately 120 kg live weight and slaughtered at a commercial plant, and carcass characteristics and meat quality were evaluated. Halothane carriers (Nn/ _ _), in comparison to Halothane normal (NN/_ _) pigs, had shorter carcasses, lower longissimus ultimate pH, higher Minolta L* and b* values, and greater drip loss. Rendement Napole gene carriers (_ _/RN- rn+) had higher L* and b* values and drip and cooking loss and lower longissimus ultimate pH than homozygous recessive animals (_ _/rn+ rn+). There were Halothane x RN genotype interactions (P < 0.05) for subjective color, firmness, and marbling scores, and for shear force. Animals that were normal for both genes (NN/rn+ rn+) had the highest subjective scores for color (2.60, 1.88, 1.85, and 1.95, SE = 0.181, P < 0.05), firmness (2.53, 2.03, 2.10, and 1.89, SE = 0.182, P < 0 .05), and marbling (2.11, 1.44, 1.53, and 1.55, SE = 0.153, P < 0 .05) for genotypes 1, 2, 3, and 4, respectively, suggesting darker, firmer muscle with a higher level of marbling for this genotype. Shear force was highest for Nn/rn+ rn+ animals (3.83, 4.41, 3.79, and 3.70, respectively, SE = 0.172, P < 0.05). Gilts had less s.c. backfat thickness, greater longissimus muscle area, and lower subjective marbling scores than barrows. There was no effect (P > 0.05) of gender on other meat quality traits. This study illustrates the negative effects of the Halothane and RN genes on fresh pork quality and suggests that in combination the detrimental effects of the two genes are additive for ultimate pH, objective color, and water-holding capacity.

The reproductive performance over five parities of two one-quarter Meishan female genotypes were compared with a three-breed cross female genotype based on conventional breeds of pigs. Hampshire-sired progeny from these females were evaluated for growth performance and carcass measures. The female genotypes evaluated were Landrace × (Meishan × Yorkshire) (LMeY) (n = 45), Duroc × (Meishan × Yorkshire) (DMeY) (n = 41), and Landrace × (Duroc × Yorkshire) (LDY) (n = 50), respectively. LMeY had a greater number of pigs born alive (11.1, 10.6, and 10.2, SE = 0.24 for LMeY, DMeY, and LDY, respectively, P < 0.05) and a higher total litter birth weight (20.02, 18.16, and 17.29, SE = 0.383 kg for LMeY, DMeY, and LDY, respectively, P < 0.001) than the other lines. Gestation length was reduced for the two Meishan-cross genotypes (114.5, 114.3, and 114.9, SE = 0.18, for LMeY, DMeY and LDY, respectively; P < 0.001). A shorter farrowing interval was observed for the LMeY (147.1, 148.6 and 151.4, SE = 1.32 for LMeY, DMeY and LDY, respectively, P < 0.05). Number of pigs weaned per litter was highest for LMeY line (10.7, 10.0, and 9.4, SE = 0.22 for LMeY, DMeY and LDY, respectively; P < 0.05). No differences (P > 0.05) were observed between the Hampshire-sired progeny of the three dam genotypes for growth performance, backfat thickness and loin eye depth at 114 kg. These results indicate that the development of a female line with one-quarter Meishan may result in improved reproductive efficiency compared to female lines based on western breeds. Key words: Pigs, crossbred, Meishan, reproductive performance, growth performance