The objectives of this study were to determine the model of inheritance of the callipyge gene and to evaluate the growth, ADFI, feed efficiency, reproductive performance, and wool growth of sheep that are heterozygous for the callipyge gene. Ewes (n = 236) with a normal muscle phenotype and genotype were mated to three heterozygous rams that expressed the callipyge gene. Lambs (n = 311) were subjectively classified at weaning (90 to 120d) according to muscle phenotype by a panel of three evaluators working independently. The callipyge muscle phenotype was expressed in 150 lambs, whereas 161 lambs expressed a normal muscle phenotype. The percentage of lambs expressing the callipyge muscle phenotype (48.2%) did not differ (P > .1) from the expected 50%. Growth rate was similar for lambs of both phenotypes regardless of sex. Feed efficiency was superior (P < .05) for both male and female lambs with the callipyge muscle phenotype. Average daily feed intake was lower for male (P < .02) and female (P < .004) lambs with the callipyge muscle phenotype. Grease fleece weight and staple length at 12 mo were superior (P < .03) for ewes with a normal muscle phenotype. These results indicate that the callipyge gene in sheep is dominant when inherited from the paternal parent and lambs expressing the callipyge gene have increased feed efficiency and reduced ADFL.

The objective of this study was to determine technician effects of live animal ultrasonic estimates of fat thickness (FTU) and longissimus muscle area (LMAU). Steers (n = 36) representing four breed-types (Brown Swiss, Average Zebu-cross Mexican, Corriente Mexican, and typical British crossbred) of commercial slaughter cattle were isonified to estimate accuracy and repeatability of fat thickness (FT) and longissimus muscle area (LMA) measurements by two experienced technicians. Repeated measures of FTU and LMAU were taken by technicians on two consecutive days with an Aloka 500V ultrasound unit equipped with a 3.5-MHz, 172-mm scanning width, linear-array transducer. Ultrasonic estimates of fat thickness and LMAU were taken at the 12th and 13th rib interface 48 h before slaughter; carcass fat thickness (FTC) and longissimus muscle area (LMAC) were measured 48 h postmortem. Means for FTU, FTC, LMAU, and LMAC were .91 +/- .36 cm, .82 +/- .40 cm, 70.7 +/- 9.43 cm2, and 72.4 +/- 8.9 cm2, respectively. Ultrasound and carcass measures of FT and LMA were different (P less than .01) among breed-types but were not different (P greater than .10) between technicians or for technician x breed-type interactions. Pooled simple correlation coefficients (P less than .01) were .87 and .86 between FTU and FTC and .76 and .82 between LMAU and LMAC for Technicians 1 and 2, respectively. Repeatabilities estimated by intraclass correlation methods were .91 +/- .03 and .81 +/- .06 for images repeated over 2 d and .95 +/- .02 and .83 +/- .05 for images repeated by two technicians for FT and LMA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pig birth (first 3-wk period) and rearing environments on growth and muscle quality characteristics of loins were evaluated in three experiments over seasons in west Texas and central Missouri. Housing systems included indoor slatted-floor buildings, indoor deep-bedded buildings, outdoor housing on dirt, and outdoor housing on alfalfa pasture. Experiments were conducted during the growing/finishing phases and pigs were slaughtered at the same age. Loins were collected, vacuum-packaged, and stored for 14 d at 2 degrees C. Pigs born and finished in an outdoor environment during the summer months (Exp. 1) had a greater ADG (0.92 vs 0.82+/-0.06 kg/d, P < 0.05) and had heavier carcass weights (87.9 vs 78.4+/-2.4 kg, P < 0.05) than pigs born and finished in an indoor environment with a slatted-floor finishing building. Carcasses from the outdoor-reared group measured a larger (P < 0.05) loineye area and were fatter (P < 0.01) at the first rib, last rib, and last lumbar vertebra measurements than carcasses from the indoor-reared group. Loin chops from outdoor-reared pigs had darker color scores in the retail display case throughout the 4-d period, measured lower L* values on d 1, and had more discoloration and browning on d 4 than loin chops from the indoor-reared group. During the winter months (Exp. 2), no difference was detected in ADG, carcass measurements, sensory characteristics, or shear force values from indoor-born pigs placed in either an outdoor or indoor finishing environment. Pigs finished on deep bedding (Exp. 3) had heavier carcass weights and more backfat (P < 0.01) than pigs finished on slats, but no differences were detected in sensory panel or shear force results. Overall, carcass measurements, pH, drip loss, sensory panel, and shear force values were similar among the groups finished in different housing systems. Outdoor or deep-bedded systems may increase growth rates of pigs if suitable land area and resources are available, but pork quality of loins will be similar for pigs finished in either conventional or alternative systems.

Paternal half-sibling Rambouillet ram lambs (n = 18) representing two muscle phenotypes were slaughtered at 54.5 kg to evaluate carcass characteristics and composition. Lambs were produced from a sire that was heterozygous for the callipyge gene. Carcasses were broken into wholesale and retail cuts to evaluate percentage bone-in retail yield of carcasses at various fat trim levels and percentage of boneless retail cuts. Retail cuts were trimmed to .6 and then to 0 cm fat trim and bones were removed to determine boneless, closely trimmed retail cut yield. Chemical composition was determined using proximate analysis. Lambs expressing the callipyge gene had higher dressing percentages (57.3 vs 53.9), leg (14.4 vs 11.0) and conformation (14.4 vs 11.0) scores, and larger longissimus muscle (LM) areas (17.6 cm2 vs 10.3 cm2). All other carcass measurements were similar between phenotypes except marbling score, which was higher (417.8 vs 325.6) for controls. Lambs expressing the callipyge gene had a higher (40.2 vs 32.9) percentage boneless retail yield than controls. Retail yield of the boneless shoulder did not differ between phenotypes (8.9 vs 8.0). All other percentages of boneless retail cuts were higher (P < .02) for lambs expressing the callipyge gene. Carcasses from lambs with the callipyge gene had higher protein (16.6 vs 15.2), moisture (63.6 vs 58.6) and ash (.85 vs 77) percentages and lower fat (18.9 vs 25.4) percentages than controls. These data suggest that ram lambs expressing the callipyge gene have an advantage in retail yield and carcass conformation when compared to normal-muscled half-siblings.

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