Milk production and milk composition were studied in 520 primiparous Merino crossbred ewes that were the progeny of 30 sires from several maternal crossing breeds including Border Leicester, Coopworth, Finnsheep and East Friesian. The ewes were born in 3 years (1997, 1998, and 1999), with 3 sires used in every year to provide genetic links. The crossbred ewe lambs were randomly assigned to autumn or spring joining groups and mated to Poll Dorset rams to lamb at 12 or 19 months of age. Ewes were milked on 3 days during their first lactation at approximately 3, 4, and 12 weeks after lambing. On each milking day, each ewe was initially injected with oxytocin, milked out by machine, and then hand-stripped. This procedure was repeated approximately 4 h later, with the milk weight and time recorded to extrapolate to daily milk yield, and composition of the milk was determined. Daily milk yield was analysed using REML mixed models procedures and 3 measures of milk production were predicted: peak milk yield at 21 days of lactation, total milk yield from 21 to 90 days of lactation, and length of lactation (days for daily yield to decline to 600 g/day). Milk composition traits (%fat, %protein, %lactose) and proportion of machine milk yield were analysed with similar models. Sire breed, number of lambs born and suckled, season, and ewe weight gain from mid-pregnancy until lamb weaning were all significant (P < 0.01) for daily yield, which declined from 2.1 kg/day at 21 days to 0.7 kg/day at 90 days of lactation. The Finnsheep-cross ewes had lower peak milk yield (1.84 ± 0.08 v. 2.09–2.19 ± 0.1 kg/day) and lower total yield of lactation (21–90 days) than all the other breed-cross ewes (78 ± 3 v. 92–107 ± 5 kg). The East Friesian-cross ewes had significantly longer lactations (128.8 ± 10.9 days) than the Border Leicester (98.1 ± 4.4 days) and Coopworth (93.7 ± 4.2 days), with the Finnsheep-cross ewes the shortest (80.1 ± 3.1 days). The East Friesian-cross ewes had the greatest and the Finnsheep-cross ewes the least total yield of lactation (107 ± 5 and 78 ± 3 kg, respectively). There were significant differences in peak milk yield for ewes bearing and suckling single lambs, twin-born and single-raised lambs, and twin-born and raised lambs (1.86 ± 0.04, 2.03 ± 0.09, and 2.37 ± 0.07 kg/day, respectively). There was a significant decline in daily milk yield with increasing ewe weight gain from mid-pregnancy to lamb weaning (–18.1 ± 4.2 g/kg). All the components of milk composition changed from the peak of milk production at 3 weeks to the end of lactation. The East Friesian-cross ewes had significantly lower milk %fat (by approx. 1 percentage point) at both 21 days and 90 days of lactation than ewes by all other sire breeds. The 30 sire progeny mean deviations for daily milk yield ranged from –292 to +276 g/day, with considerable ranges between sires within the sire breeds. The implications for lamb production and breeding programs are discussed.

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The growth rate of 667 single cross lambs from birth to 4 weeks (Period 1) and 4 weeks to weaning at 12 weeks (Period 2) was measured, along with the milk production of their 520 primiparous crossbred ewe dams over 3 years. The lambs were the progeny of Poll Dorset rams and first cross ewes lambing for the first time at 12 and 19 months of age. The first cross ewes were the progeny of Merino ewes mated to 30 individual sires from several maternal sire breeds, including Border Leicester, East Friesian, Finnsheep and Coopworth. Milk production of the ewes was measured at ~3, 4 and 12 weeks of lactation using a 4-h milk test. The effect of ewe milk production on lamb growth rate in Period 1 included a significant interaction with lamb birth and rearing type (P < 0.001). These regressions were 52 ± 18 g/day per kg/day for single born and reared, 24 ± 17 g/day per kg/day for multiple born and single reared and 18 ± 17 g/day per kg/day multiple born and reared lambs. The regression of ewe milk production in Period 2 on lamb growth rate in Period 2 was also significant (P < 0.001), although milk production in Period 1 accounted for more variation in lamb growth. There were significant interactions of ewe weight gain (from mid pregnancy to lamb weaning) with season in Period 1 (P < 0.01) and year in Period 2 (P < 0.001). There was also a significant interaction (P < 0.001) of year with ewe mid-pregnancy weight for lamb growth in Period 2. Lamb birthweight had a significant effect on lamb growth rate in Period 2 (regression coefficient 6.68 ± 2.57 g/day.kg, P < 0.01).

The recycling of sewage sludge or biosolids to grassland is strategically important in the European Union (EU) and its use is tightly regulated to control the risk of pathogen transfer to animals and the food chain. Sewage sludges not only contain valuable concentrations of beneficial nutrients, but also elevated concentrations of potentially toxic metals (PTM) compared with average background concentrations in the soil. The EC and UK regulations refer to six PTM, Cd, Pb, Cu, Zn, Ni and Hg, with provisional regulations for Cr, that have to be controlled to prevent detrimental effects on soil and animal health. Despite these regulations, there is still a danger that grazing animals may ingest elevated concentrations of PTM. Biosolids may adhere to herbage after the surface application of sewage sludge to grassland. The repeated surface application of sewage sludge to grassland can lead to elevated concentrations of PTM at the soil surface that may be ingested, together with soil and herbage, by grazing ruminants. This may lead to accumulation of Cd or Pb in liver or kidney. The risk to the human food chain is considered to be low, but the impact on the environment is still unknown. There is little information, for example, on the amount of soil and PTMs that may become incorporated into conserved grass. At present EU and UK legislation and voluntary codes of practice have been developed to protect animal from pathogens in sewage sludge and to minimize any potential risks from accumulation of PTM. The background and implementation of the legislation are examined in this review, and the source and mechanisms of accumulation of PTM by the grazing animal are evaluated.

Semen from Hereford (H), Friesian (F), Charolais (C) and Brahman (B) bulls was used to inseminate H and F cows in August and September of each year from 1970 to 1973. After weaning at 8 months of age, the heifer progeny were grazed on improved pastures and oestrus was detected by sterilized bulls fitted with chin-ball harnesses. Average daily liveweight gains (kg/day) from weaning to 21 months and liveweights (kg) at 21 months were: HH, 0.44, 373 ; FH, 0.47, 402; CH, 0.47,402; BH, 0.45, 374; HF, 0.42, 428; FF, 0.43, 427; CF, 0.44, 451; BF, 0.40, 401. Mean ages (days) and liveweights (kg) at puberty, and the proportions (%) of heifers reaching puberty by 15 months of age were: HH 464, 290, 41; FH 347, 263, 85; CH 470, 326, 38; BH 568, 336, 14; HF 277, 285, 100; FF 298, 294, 98; CF 309, 313, 97; BF 397, 306, 64. Heterosis in HF and FH crosses for age and weight at puberty were - 59 days and - 17.4 kg respectively. These results indicate that, relative to the use of straightbred Hereford heifers, early breeding in the progeny would be facilitated by crossing Hereford with Friesian, unaffected by crossing with Charolais, but made more difficult by crossing with Brahman, in a temperate environment.