We determined milk intake and growth rate of fat-tailed Awassi ram lambs from birth to 30 days of age when sucking ewes that were grazing natural green pasture in the semi-arid Negev. The conversion of milk and energy intake to body mass and body solids gain in the lambs were calculated. Annual rainfall and, as a consequence, pasture availability were below average during the study. Body mass at birth was 4·22 (s.d. 0·71) kg and at 30 days was 12·10 (s.d.1·22) kg for an average daily gain of 256 (s.d.33) g/day. Of the 256 g/day, 100 (s.d.12·3) g/day were body solids, and for every unit body mass increase, proportionately 0·391 was body solids. Milk and energy intakes averaged 1·34 (s.d.0·23) l/day and 5·66 (s.d.0·97) MJ/day, respectively. The volume of milk intake per kg increase in body mass and body solids were 5·2 l and 13·4 l, respectively, whereas, the energy intake per kg increase in body mass and body solids were 22·1 MJ and 56·6 MJ, respectively. Of the total metabolizable milk energy intake, proportionately 0·46 was converted to body energy of the lamb. Although dry matter intake of the ewes was insufficient to prevent body mass loss, they produced sufficient milk to support a relatively high lamb growth rate, presumably by mobilizing fat reserves in the tail.

The effect of tail docking on metabolizable energy requirements and carcass characteristics was studied using 80 weaned entire Awassi male lambs. Docking was performed within 3 days of birth and lambs were weaned at 90 days old. Docked and undocked lambs were randomly allocated to four groups, individually penned and offered different amounts of a pelleted concentrate diet. The pelleted diet was estimated to contain 11·8 MJ of metabolizable energy (ME) and 182 g of crude protein (CP) per kg dry matter (DM). Lambs on the high levels of intake were slaughtered at a target weight of approximately 45 kg. Other lambs were maintained on the diet for 149 days before being slaughtered. The right sides of all carcasses were cut into standardized commercial cuts then dissected into muscle, fat and bone. The soft tissue was pooled and analysed for DM, C P, ash and fat. Prediction of live-weight gain (LWG) and empty body gain for a given ME intake (MEI) was made using the growth and MEI data. MEI was expressed as MJ per kg metabolic body weight (M 0·75) per day. Tail docking had no effect (P > 0·05) on lamb growth from birth to weaning. During the post-weaning growth period, LWG and empty body gain were significantly higher (P < 0·05) for undocked lambs than docked lambs, at feeding levels between 0·31 and 0·52 MJ/kg M 0·75 per day and similar (P > 0·05) at high levels of intakes (between 0·74 and 1·1 MJ/ kg M 0·75 per day). Hot and cold carcass weights were similar (P > 0·05) for the two groups. Differences in empty body weight and fleece-free empty body weight were significant (P < 0·05) only for the 0·443 to 0·522 MJ/kg M 0·75 per day level of ME intake. Predicted ME requirements were higher for docked lambs for an estimated LWG between 0 and 100 g/day and lower for higher LWG (125 to 225 g/day). Docking had no effect (P > 0·05) on food conversion efficiency (FCE). Carcasses from docked lambs had significantly lower (P < 0·001) internal plus tail fat. Pooled soft tissue excluding tail fat, for the undocked lambs contained significantly more (P < 0·01) protein, less (P < 0·001) fat, higher (P < 0·01) moisture and similar (P > 0·05) ash content.

This study investigated the factors affecting milk production and lactation curve parameters from the complete lactations of Awassi dairy sheep. The animals were kept in a single flock under intensive management and milked twice daily starting at lambing. Lambs were removed from the ewes at birth into an artificial rearing unit. The results of the analyses of 3740 complete lactations showed a mean litter size of 1·28 lambs born per ewe lambing and average total milk yield of 506 l from lactations 214 days in length and with an average lambing interval of 330 days. Mean lactation number was 3·71 and ewes conceived on average in the 6th month of the lactation. The lactations peaked on day 45 at a yield of 3·44 l. The maximum milk secretion potential of the ewes was 3·9 l/day, with milk yield increasing at 62 g/day mid way between lambing and peak yield and declining at 16·5 g/day mid way between peak and the end of lactation. Age at first lambing, lactation number, litter size, month of lambing and month of conception during the lactation had significant effects (P < 0·05) on some or all of the lactation parameters investigated. Relatively high milk yield was obtained in lactations starting in the January to March period. The monthly effect on milk production was explained by significant (P < 0·05) heat load and photoperiod effects. High milk production was found to have a significant (P < 0·05) adverse effect on reproductive performance. Conception followed a significant (P < 0·05) short term variation in milk production.

Despite milk being an important product from sheep, there are very few reports of milk production from the complete lactation of dairy sheep. The Improved Awassi in Israel is kept under an intensive system of management with lambs being weaned soon after birth. Records from one such flock were analysed to investigate the suitability of various mathematical functions for describing milk yield from the complete lactations of dairy sheep. This included a consideration of whether the functions could cope with short lactations, a characteristic of dairy sheep, and a limited number of test-day records per lactation.

Four non-linear mathematical functions were investigated (Wood, Morant, Grossman and Pollott), two of which could also be fitted in a linear and a linear weighted form (Wood and Morant). These functions were fitted to weekly data from a ‘typical Awassi lactation curve’, represented by least squares means of daily milk yield from each week of a 40-week lactation derived from an analysis of 25605 test day records. Characteristics of the lactation were calculated from the functions, such as total milk yield, day and level of peak yield and persistency. These functions were also fitted to 1416 individual lactation records of up to 10 test-day records per lactation. The value of the functions was investigated using the residual mean square (RMS) of the fitted curve as an indicator of how well each function described the lactation. Forms of these functions with a reduced number of parameters were also investigated.

The non-linear functions always fitted the data with a lower RMS than their linear equivalent and the weighted form of the linear functions always had a lower RMS than the unweighted form. Of the linear functions, Morant fitted better than Wood. Of the non-linear functions Grossman, Morant and Pollott (additive and multiplicative) fitted the data equally as well but better than Wood. The various functions predicted characteristics of the lactation curve differently; the Wood functions tended to overestimate yield in early lactation and the Morant functions underestimated peak yield.

No function was better suited to short lactations than another. However the three-parameter function of Morant, Pollott multiplicative and Pollott additive were considered to be the most suitable for describing the complete lactation of dairy sheep.

The response of Awassi ewes to graded amounts of supplementary concentrate diet was examined for the first 12 weeks of lactation. The growth rate of lambs and their health status were also investigated. Seventy-five ewes were divided into three equal groups and given a basal roughage diet of shredded wheat straw at a rate of 750 g dry matter (DM) per ewe per day supplemented with a concentrate diet at three amounts, 950 g (low), 1150 g (medium) and 1350 g (high) of DM per ewe per day starting at the beginning of lactation. Ewes were adapted to the diet by feeding daily at a rate of 200 g per ewe during the last 6 weeks of pregnancy. The concentrate was estimated to contain 11⋅8 MJ of metabolizable energy and 182 g of crude protein per kg DM. Ewes and their offspring were housed in a partly enclosed yard. Lambs remained with their dams continuously except for the days of milk yield measurements, when they were separated from the dam for 11 or 12 h. The ewes were examined for subclinical mastitis and the incidence of scouring in lambs was recorded.

Ewes given the high level of concentrate produced more (P < 0⋅05) milk but differences between medium and low groups were significant only up to week 4 of lactation. Total milk yields during the 9 weeks test period were 58⋅5, 70⋅4 and 93⋅3 kg for the low, medium and high groups, respectively. Ewes suckling twins produced more (P < 0⋅05) milk than ewes suckling singles. The rate of weight loss was lower (P < 0⋅01) for ewes given the high feeding regime; these regained their immediate post-lambing body weight by week 10. Sex of lambs and litter size had no effect on body weight loss but ewes nursing twins tended to loose more weight during the 12 weeks suckling period. Lamb growth rates were similar (P > 0⋅05) across treatments. The daily intake of concentrate by the ewes did not affect the incidence of scouring in lambs or mastitis in ewes.

On both economical and biological grounds it is recommended to offer concentrate during the first 9 weeks of lactation at levels >950 g per ewe per day in order to produce an appreciable yield of milk and restore a positive energy balance early in the ewe lactation period.

Ovulation rate, embryo survival, lamb production, lamb survival and milk production of Awassi and BooroolaAwassi crossbred ewes, kept indoors, were compared. Awassi were non-carriers while Booroola × Awassi (F1) and about half of 3/4 Awassi-1/4 Booroola (BQ) ewes were heterozygous at the FecB gene. Mean ovulation rate increased by 1·5 to 1·6 corpora lutea per ewe ovulating and prolificacy by 0·7 lambs born per ewe lambing in Fj and BC1 (B+) ewes as compared with Awassi. Embryo survival rates in BC1 ewes with two, three and four ovulations were 0·83, 0·68 and 0·71, respectively. Lamb survival rates at 1 day of age were 0·93, 0·90 and 0·77 and average birth weight was 4·9, 4·0 and 3·0 kg for lambs born as singles, twins and triplets, respectively. Average milk production of the Awassi was 506 I per ewe per lactation. F1 and BC1 ewes produced respectively, proportionately 0·48 and 0·63 of the Awassi milk production and there was no significant difference in milk production between BC1,(B+) and BC1(++) ewes. The relatively low milk production of the Booroola Awassi crosses suggests that heterosis and recombination effects on milk production were negative. It is concluded that incorporation of the B allele per se can increase lamb production in the Awassi without affecting its milk production.

The length of the oestrous cycle observed in 20 ewe lambs and 424 ewes of the Awassi breed gave mean values of 16·4 (s.d. 1·31) days for ewe lambs and 17·4 (s.d. 1·84) days for ewes. Plane of nutrition did not affect cycle length in ewe lambs and age of ewe (from 2 to 5 years) did not affect oestrous cycle length in ewes (P > 0·05). Of 40 ewes treated with progesterone intravaginal sponges 33 (83%) showed oestrus and 28 (70%) ovulated at the first (synchronized) and 31 (78%) and 30 (75%) at the repeat oestrus. Mean duration of oestrus was 40·0 (s.d. 16·37) h (range 8 to 72) for the first and 34·7 (s.d. 11·19) h (range 16 to 54) for the repeat oestrus. Ovulation rate, measured in the same ewes, gave mean values of 1·18 (s.d. 0·460) for the first and 1·223 (s.d. 0·440) for the repeat oestrus.