In crossbred female lambs given a concentrate diet ad libitum between 8 and 20 weeks of age, daily subcutaneous injections of 0·1 mg bovine pituitary growth hormone (GH) per kg live weight increased daily live-weight gain (347 v. 284 g/day; P < 0·01; no. = 8), food conversion efficiency (3·94 v. 4·49 kg dry matter per kg gain; P < 0·01) and greasy fleece weight (1·49 v. 0·99 kg; P < 0·001). The increase (4·8 kg) in final live weight was due primarily to an increase in the non-carcass components of the body (3·5 kg), with little effect on carcass weight (1·3 kg). However, bovine GH treatment markedly increased the weights of lean tissue (11·4 v. 9·2 kg; P < 0·001) and bone (2·8 v. 2·4 kg; P < 0·001) and moderately reduced the weight of fat (7·0 v. 8·0 kg; P < 0·10) in the carcass. The bovine GH treatment raised plasma concentrations of immunoreactive GH within the physiological range for about 16 h each day and significantly increased mean plasma concentrations of insulin and prolactin. Daily injection of 1 mg bromocriptine had no effect on daily live-weight gain, food conversion efficiency or carcass composition. This treatment markedly reduced plasma concentrations of prolactin but also significantly reduced insulin concentrations. When given in combination with bovine GH, bromocriptine reduced the GH-induced stimulation of insulin concentration and tended to decrease the effects of GH on food conversion efficiency and growth. This interaction was significant only for the effects on greasy fleece and skin weights (P < 0·01).

SummaryThe influence of physiological state (pregnant, lactating, dry) on body composition and fat partitioning in Friesian cows has been examined. A total of 20 cows, four per physiological state, were slaughtered and their left half carcasses dissected into individual muscles, bones and fat depots. All body parts, including the internal organs and fat depots, were weighed at slaughter.Muscle tissue and the internal organs showed some weight changes, consistent with a redistribution of tissue towards the udder and gut, and mobilization of muscle, but the major changes in weight associated with changing physiological state occurred in total body fat.Intermuscular fat made the greatest absolute contribution to changing fat weight, but subcutaneous fat showed the greatest proportional change with changing physiological state. The order of depletion of fat depots during fat loss was approximately the reverse of the order of development found during developmental growth.The distribution of subcutaneous fat between seven defined regions of the carcass was not affected by differences in total fatness in different physiological states. This, and the high correlation found between fat depth and total body fatness, confirms the view that measures of subcutaneous fat depth, e.g. by ultrasonics, should be useful predictors of the energy status of cows in varying physiological states.

1987). The effects of dose and method of administration of biosynthetic bovine somatotropin on live-weight gain, carcass composition and wool growth in young lambs. ABSTRACT Exogenous bovine pituitary somatotropin (GH) can influence markedly body composition in fattening lambs. However, neither the effects of biosynthetic somatotropin nor the effects of dose and method of administration have been reported. Fifty Dorset-cross lambs (female and castrated male) were given concentrate ad libitum and treated between 10 and 22 weeks of age with biosynthetic bovine somatotropin either dissolved in buffer and injected subcutaneously (s.c.) in proportion to body weight (0-025, 0-1 or 0-25 mg/kg per day), dissolved in buffer and continuously infused s.c. (0-1 mg/kg per day) or suspended in olive oil and injected s.c. (0-1 mg/kg per day), and compared with 10 untreated control lambs. Somatotropin had little effect on live-weight gain (controls = 228 g/day; final live weight 37 kg), food intake and food conversion efficiency, and only marginally increased the weight of muscle and bone dissected from the shoulder joint. The weights of the major fat depots in the abdominal cavity and of fat dissected from the shoulder joint were linearly related to dose of somatotropin (P < 0-001). Lambs given the highest dose had less visceral fat (1-18 v. 2-84 kg; P < 0-001) and proportionately less fat (285 v. 374 g/kg; P < 0-001) and more muscle (542 v. 447 g/kg) and bone (172 v. 149 g/kg; P < 0-001) in the shoulder joint than control lambs. There was a positive curvilinear relationship (P < 0-01) between clean wool growth (mid-side patch sample) and dose; lambs injected daily with 0-1 mg somatotropin per kg grew one-third more wool than control lambs. Method of administration affected plasma somatotropin profiles but had no significant influence on any of the responses measured. The anabolic actions of somatotropin may have been limited in this experiment by a low sodium concentration in the diet. It is concluded that the lipolytic/anti-lipogenic effect of somatotropin can occur in the absence of conditions conducive to the stimulation of muscle protein deposition and that the response is dose dependent but not influenced by method of administration of the hormone.

The growth of Southdown and Clun lambs was studied over the period birth to 415 days of age.At birth, 50, 100, 150 and 200 days of age five lambs of each breed, and at 415 days three lambs of each breed, were slaughtered and their body composition determined by dissection.The relative growth of lean, bone and total body fat was not influenced by breed. At each age both Cluns and Southdowns had similar proportions of total body fat, and were considered to be at the same stage of maturity.There was a breed difference in fat partitioning, with the Clun depositing proportionately more of its total body fat intra-abdominally, compared with the Southdown. However, there was no significant effect of breed on the growth of individual fat depots relative to total fat. From earliest to latest the order of maturity was pericardial, intermuscular, perirenal-retroperitoneal, mesenteric, subcutaneous and lastly, omental fat.

Carcass composition and quality and eating quality of the m. longissimus dorsi (LD) were compared in 15 entire male (ram) and 15 female (ewe) pure bred Dorset Down lambs (carcass weight range 12 to 23 kg).Rams grew 28 g/day faster than ewes, taking on average 2 weeks less to achieve 35 kg live weight. At the mean carcass weight of 16-8 kg, ram carcasses contained more lean (42 g/kg carcass weight) and bone (19 g/kg) and less fat (subcutaneous, 33 g/kg; intermuscular, 28 g/kg; perirenal-retroperitoneal, 14 g/kg) than ewe carcasses.At the same level of fat cover in the commercially prepared side, ewe carcasses required more trimming of subcutaneous fat than rams. However, there was more intermuscular fat (which is not removed by conventional cutting) in the ewes; consequently their saleable meat contained 51 g/kg more fat and 37 g/kg less lean than that from rams.The roast LD was invariably tender and the eating quality of LD from rams was as desirable as that from ewes, while overall eating quality compared favourably with that of animals studied previously. There was no evidence of an undesirable sexual odour or flavour in ram meat.With early maturing breeds, which can be finished off grass, non-castration of entire males offers the opportunity of improving the efficiency of lean meat production whilst retaining good carcass and eating quality.