A muscle hypertrophy condition in lamb (callipyge): characterization of effects on muscle growth and meat quality traits.

Abstract

The present experiment was conducted to determine the effect of the callipyge phenotype on traits affecting muscle growth and meat tenderness. Dorset wethers (N = 40) that were either carriers or non-carriers were fed grain and slaughtered at 169 d of age. Callipyge phenotype did not affect (P > .05) slaughter weight, hot carcass weight, or weights of the heart, spleen, viscera, kidney-pelvic fat, head, and pelt; however, callipyge lambs had a higher dressing percentage and lighter lungs, liver, and kidneys (P < .01). Callipyge lambs had reduced fat thickness and marbling score and higher leg scores and longissimus area (34%). Adductor (30%), biceps femoris (42%), gluteus group (31%), longissimus (32%), psoas group (20%), quadriceps femoris (18%), semimembranosus (38%), and semitendinosus (26%) weights were higher in the callipyge phenotype (P < .01); however, phenotype did not affect (P > .05) weights of infraspinatus or supraspinatus. Longissimus pH and temperature declines were not affected (P > .05) by phenotype. Longissimus myofibril fragmentation index was lower at 1 (27%), 7 (35%), and 21 (37%) d postmortem and Warner-Bratzler shear force was higher at 1, 7, and 21 d postmortem in the callipyge phenotype (P < .01). Shear force values of callipyge lambs at 21 d postmortem tended to be greater (P = .12) than shear force values of non-carriers at 1 d postmortem . Activities of calpastatin (83%) and m-calpain (45%) were higher in the callipyge (P < .01); however mu-calpain activity was not affected (P > .05). Longissimus and semitendinosus RNA concentration, DNA content, RNA content, protein content, and the RNA:DNA ratio were higher (P < .05), but DNA concentration, protein concentration, and protein:DNA were not affected in the callipyge phenotype. The higher calpastatin activity associated with callipyge suggests that protein degradation may be reduced in the live animal. Additionally, the increased muscle DNA content associated with the callipyge phenotype suggests an increase in satellite cell proliferation, and results in an increased capacity of skeletal muscle to accumulate and maintain myofibrillar protein. These results suggests that both reduced rate of protein degradation and higher capacity for protein synthesis are consequences of the callipyge condition.

The callipyge mutation and other genes that affect muscle hypertrophy in sheep

“…for callipyge carcasses [25,32]. These superior carcass traits translate into improved yields of wholesale leg, loin, rack, and shoulder from callipyge animals by 11.8%, 4.7%, 2.5%, and 2.3%, respectively, over normally muscled lambs [9].…”

“…The callipyge phenotype in sheep is a muscular hypertrophy that is most pronounced in the muscles of the pelvic limb [26,32]. Muscles from callipygeexpressing lambs enlarge to differing degrees, and not all muscles are affected.…”

“…Therefore, the widespread production of callipyge lamb would have the potential to lower the cost of lamb for consumers and to increase the profitability of the sheep industry. Unfortunately, the stigma associated with callipyge lamb as being unacceptably tough [32,46,51] has limited its production in the United States.…”

Epigenetics and developmental programming of welfare and production traits in farm animals

“…It appears that the callipyge phenotype relates primarily to changes in postnatal rather than prenatal muscle growth, but it does have a complex inheritance pattern (see Georges et al 2003). However, callipyge sheep produce tough meat (Koohmaraie et al 1995), thought to be due to decreased protein degradation pre-and postmortem because of increased levels of calpastatin, the endogenous inhibitor of the calpain proteolytic enzymes.…”

Influence of ultrasound and proteolytic enzyme inhibitors on muscle degradation, tenderness, and cooking loss of hens during aging

“…Calpastatin activity of breast skeletal muscles was determined on days 0, 1, 3, and 7 after death according to Koohmaraie et al (1995), with small modifications. In brief, 2 g of minced breast muscle was homogenised in 6 volumes of ice-cold extraction buffer (5 mmol/l EDTA, 50 mmol/l Tris-HCl, 1 mmol/l PMSF (phenylmethanesulfonylfl-uoride), 10 µmol/l of leupeptin, 50 mg/l of ovomucoid, pH 8.3) and centrifuged at 25 000 g for 1 h at 4°C.…”