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Nine male and nine female lambs each from the Karagouniko (K), Chios (C) and East Friesland (F) breeds were weaned at a mean age of 50 days and were killed over a commercial range of live weight from 16 to 44 kg (carcass weights 6 to 22 kg).Carcass weight was linearly related to fasted live weight prior to slaughter (r = 0-994). There were significant but small differences between breeds in mean weight of lungs, pelt and internal fat. The carcass components of bone, muscle and fat tissues were related to carcass weight by linear or quadratic regression. Adjusted to mean carcass weight, the mean weight of bone did not differ between breeds (2-82 kg, s.e. = 0-056 at 12-8 kg carcass). The K and C lambs had significantly less muscle than the F lambs (6-77, 6-63 and 8-20 kg, respectively, s.e.d. = 0-094) and more fat (2-87, 2-95 and 1-29 kg, respectively, s.e.d. = 0-017) when compared at mean carcass weight. The breed differences were significant over the whole range whether compared at equal weight or at an equal proportion of estimated mature weight. At the same proportion of carcass fat, corresponding to the United Kingdom market average (250 g/kg) the calculated carcass weights were 16, 17 and 30 kg, respectively, for K, C and F lambs.It is concluded that the Friesland breed differs from many others in the proportions of muscle or fat at corresponding carcass weights but this difference is not a general characteristic of dairy sheep. Comparison of breeds at defined proportions of carcass components, as determined by market standards, can be effectively achieved by serial slaughter over a suitable weight range.

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The effects of melatonin, administered during anoestrus, on the time of onset of oestrus and on conception rate were investigated in two trials carried out on mature ewes of three indigenous and one imported breed. The ewes lambed between December and February, their lambs were weaned in March and they were hand milked twice daily until September.In the first trial, 12 Chios and 12 Serres ewes were dosed, orally, for 60 days from 19 April with 3 mg melatonin (M) in 10 ml ethanol and water (1: 4 v/v). A similar number of Chios and Serres type ewes in the same flock were nominated as untreated controls (C). Vasectomized rams were used to detect oestrus from 1 May and detected ewes were immediately mated to entire rams of their own breed. The mean dates of first oestrus in Chios ewes were 4 July (s.e. 1·7 days) and 23 July (s.e. 5·4 days) (P < 0·01) for treated and control ewes respectively. Spread of first oestrus was 19 and 61 days, respectively (P < 0·01). Conception rate and ovulation rate were both higher in M (0·90 and 2·3, respectively) than in C (0·55 and 1·8, respectively) but the differences were not statistically significant. The corresponding results in the Serres ewes were 8 July (s.e. 1·6 days) and 31 July (s.e. 6·8 days) (P < 0·01) for date of first oestrus, 19 and 69 days (P < 0·01) for spread of first oestrus, 0·75 and 0·50 (P > 0·05) for conception rate and 1·8 and 1·2 ( P > 0·05) for ovulation rate.In the second trial, 12 Karagouniko and 12 East Friesland ewes received a single subcutaneous implant of melatonin (Regulin®) on 5 June and a further 12 ewes of each breed were untreated controls. The procedure was as given for trial 1. The mean date of first oestrus was advanced by melatonin in both Karagouniko ewes (25 July (s.e. 3·91 days) v. 11 August (s.e. 6·7 days); P < 0·05) and Friesland ewes (28 July (s.e. 3·2 days) v. 24 August (s.e. 7·3 days); P < 0·01). Spread of oestrus was reduced (43 v. 68 days in Karagouniko, P < 0·05 and 22 v. 87 days in Friesland ewes, P < 0·01). Conception rate of melatonin-treated ewes was higher (0·60 v. 0·45; P > 0·05) in both breeds. Ovulation rate was higher in melatonin-treated Karagouniko ewes (1·8 v. 1·3; P > 0·05 but, in the Friesland breed melatonin-treated ewes had a lower ovulation rate (2·8 v. 3·7; P > 0·05).In both trials, melatonin treatment significantly advanced and condensed the dates of first oestrus. Conception rate was consistently increased over all groups (P < 0·05) and there was a tendency towards a higher ovulation rate.