To study skeletal development and productive performance of the Italian Merino sheep breed, 24 growing male lambs were slaughtered, ingroups equal for number, at 5, 30, 50 and 70 d of age. Lambs were naturally suckled, left to graze with their dams and allowed free access to a commercial diet. In vivo and post mortem performance were evaluated. Metacarpal (MC) and metatarsal (MT) bones were measured for length, diaphyseal diameter, weight, and moisture. MC growth plate width was also assessed after AgNO3 staining. ANOVA was performed and comparisons were tested by Scheff´es test. ADG was 274, 299 and 256 g/d from d 5 to 30, 30 to 50, and 50 to 70, respectively. As age increased, slaughter weight (4.6a, 11.1b, 19.5c, 23.0d kg) and carcass (with head, thoracic organs, spleen, and liver) weight (2.9a, 7.4b, 12.2c, 14.1d kg) increased (P<0.05), but dressing (63.6a, 67.0b, 62.5a, 61.4a %) was the highest (P<0.05) at d 30. Loin eye area, indicative of carcass muscularity, increased (P<0.05) with age (3.0a, 7.6b, 10.3c, 11.2c cm2) up to d 50. Bones mainly grew longitudinally in the first month of age, with a following stop (9.8a, 11.0b, 11.5b, 11.7b cm for MC; 10.3a, 11.7b, 12.3b, 12.3b cm for MT; P<0.05). In the same period, growth plate, the site of longitudinal bone growth, has thinned (P<0.05) of about 35% (from 0.98 to 0.64 mm) and of another 24% in the following periods, reaching 0.40 mm at d 70. However, bone weight continued to increase (P<0.05) with age up to d 50, either in MC (15.5a, 24.1b, 30.2c, 32.6c g) or in MT (15.7a, 24.4b, 30.1c, 32.7c g) due to a persistence in development of transversal diameter (1.0a, 1.2ab, 1.3bc, 1.4c cm for MC; 0.9a, 1.0ab, 1.1bc, 1.2c cm for MT; P<0.05). Bone moisture, expression of bone chemical maturity, decreased (P<0.05) with age up to d 50, in both MC (49a, 38b, 29c, 25c %) and MT (49a, 38b, 27c, 23c %). The second month of age appears to be a critical period in lamb skeletal growth, which strictly related to development of muscular and adipose tissues, and influences carcass and meat quality.
Skeletal development and productive performance of Italian Merino lambs as related to age
MAIORANO, Giuseppe;GAMBACORTA, Mario;MANCHISI, Angelo
2004-01-01
Abstract
To study skeletal development and productive performance of the Italian Merino sheep breed, 24 growing male lambs were slaughtered, ingroups equal for number, at 5, 30, 50 and 70 d of age. Lambs were naturally suckled, left to graze with their dams and allowed free access to a commercial diet. In vivo and post mortem performance were evaluated. Metacarpal (MC) and metatarsal (MT) bones were measured for length, diaphyseal diameter, weight, and moisture. MC growth plate width was also assessed after AgNO3 staining. ANOVA was performed and comparisons were tested by Scheff´es test. ADG was 274, 299 and 256 g/d from d 5 to 30, 30 to 50, and 50 to 70, respectively. As age increased, slaughter weight (4.6a, 11.1b, 19.5c, 23.0d kg) and carcass (with head, thoracic organs, spleen, and liver) weight (2.9a, 7.4b, 12.2c, 14.1d kg) increased (P<0.05), but dressing (63.6a, 67.0b, 62.5a, 61.4a %) was the highest (P<0.05) at d 30. Loin eye area, indicative of carcass muscularity, increased (P<0.05) with age (3.0a, 7.6b, 10.3c, 11.2c cm2) up to d 50. Bones mainly grew longitudinally in the first month of age, with a following stop (9.8a, 11.0b, 11.5b, 11.7b cm for MC; 10.3a, 11.7b, 12.3b, 12.3b cm for MT; P<0.05). In the same period, growth plate, the site of longitudinal bone growth, has thinned (P<0.05) of about 35% (from 0.98 to 0.64 mm) and of another 24% in the following periods, reaching 0.40 mm at d 70. However, bone weight continued to increase (P<0.05) with age up to d 50, either in MC (15.5a, 24.1b, 30.2c, 32.6c g) or in MT (15.7a, 24.4b, 30.1c, 32.7c g) due to a persistence in development of transversal diameter (1.0a, 1.2ab, 1.3bc, 1.4c cm for MC; 0.9a, 1.0ab, 1.1bc, 1.2c cm for MT; P<0.05). Bone moisture, expression of bone chemical maturity, decreased (P<0.05) with age up to d 50, in both MC (49a, 38b, 29c, 25c %) and MT (49a, 38b, 27c, 23c %). The second month of age appears to be a critical period in lamb skeletal growth, which strictly related to development of muscular and adipose tissues, and influences carcass and meat quality.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
