Calcium hydroxide (Ca(OH)2) is widely available in Third World countries because of extensive limestone deposits. Previous studies (reviewed by Owen et al 1984) have shown Ca(OH)2-treated straw to be prone to mouldiness and low intakes. Urea was added to Ca(OH)2 in the present study to inhibit mould and supply nitrogen. Two experiments are reported which investigated the amounts of Ca(OH)2 and urea required for improving intake and digestibility of barley straw in sheep.

Forty Suffolk x Mule store lambs (20 castrates, 20 ewe lambs) aged 8 months were used to measure intake and digestibility of 5 straws (Table 1) in a randomized block experiment, with blocking according to weight and sex. Animals were fed restricted concentrates (Table 1) and ad libitum straw (allowing refusals of 25% of intake) over a period of 35 days, with collection of faeces over the last 8 days. For treatment, straw was chopped, mixed with chemical solutions (Table 1) in a concrete mixer, and “ensiled” for 60 days (September & October) at 500 g dry matter (DM) per kg, in plastic bags contained in 45-gallon oil drums. Straw was aerated for 3 days before feeding. Untreated straw was simply chopped before feeding.

Urease enzymes occur naturally in straw and may hydrolyze added urea to form a mixture of ammonia, carbon dioxide, and “ammonium carbonate”.We have previously found the digestible intake of barley straw by sheep to be lower when it is treated with urea than when treated with an isonitrogenous amount of ammonia (Sherwood and Owen, 1986). At ad libitum feeding levels, urea was considerably less effective than ammonia for improving voluntary straw intake, and the improvement in digestibility by urea treatment appeared to be temperature dependent. However, as level of intake is known to influence digestibility (Kiangi et al., 1981), differences in digestibility may have been confounded by differences in level of intake. There was therefore a need to compare the digestibilities of untreated, ammonia-treated and urea-treated straws where levels of intake were identical across treatments.

Before progress can be made in the selection of barley varieties (or genotypes) which have superior straw quality it is necessary to demonstrate stability for indicators of straw quality. This means that the ranking of genotypes from those with superior straw value down to those with lower value should be broadly similar when planted either at the same location in different years (or growing seasons) or in the same growing season at different locations. A preliminary test which can be carried out is to compare variation in straw quality caused by genotype with genotype x season interaction variation following removal of variation caused by blocks and season.

Barley straw was obtained from 20 genotypes grown, in randomised blocks with three replications, in successive seasons in Syria where rainfall was 229 mm in 1983/84 and 373 mm in 1984/85. There were two experiments, one where the plots had been grazed by sheep at the tillering stage and another where plots were left ungrazed. The material planted consisted of 62-rowed and 146-rowed genotypes.

The gross energy content of cereal straw is almost as high as that of grain, but, because straw is relatively indigestible even to ruminants, much of this energy passes right through the digestive system and so makes no contribution to nutrition. Treatment of straw with alkali (normally ammonia or sodium hydroxide) improves digestibility and thus increases the amounts of energy available to animals. Straw which has been improved in this way is often said to be of similar nutritional value to medium quality hay; but responses in terms of animal performance demonstrate that this is not always so.

It has been observed that the nutritive values of straws of the various cereals and of the varieties within each cereal differ considerably and that, though alkali treatments generally improve the least digestible straws the most, the differences between improved straws may still be large enough to be important. Degradability measurements carried out on large numbers of wheat, barley and oat straws to obtain an indication of nutritive value, confirm this (Tuah et al. 1986), but further evidence was needed using feeding trials with animals to support these findings and demonstrate their practical significance.

Differences in rumen volume can have considerable effects on the digestibility and voluntary intake of ruminants. For instance Mould et al. 1982 showed that cattle in Bangladesh had a much greater rumen volume relative to live weight than reported values of Friesian cattle. They also consume much more straw per unit of live weight than Friesian cattle.

Differences between cows in the ability to consume roughage have often been observed. It is however possible that this strategy could be adopted simply by increasing outflow rate and not necessarily by a high rumen volume. Depending on the strategy adopted this would give rise to differences in the digestibility of the roughage consumed.

In order to investigate these aspects in more detail, 22 lactating Friesian cows were given doses of Cr-mordanted straw having been ground through a hammer mill with a 2 mm screen. The cows were fed completely mixed diets consisting of 50% ammonia treated straw and 50% concentrate.

Recent work has shown a great variability in the nutritive value of different cereal straws. Tuah et al (1986) examined a number of cereal varieties including barley, oats, wheat and triticale. Ramanzin et al. (1986) examined the extent to which these effects could be explained by differences in leaf:stem ratio and that the nutritive value of leaves were far greater value than straw.

Investigations carried out by the Tropical Development and Research Institute (TDRI) in association with the International Centre for Agricultural Research in Dry Areas (ICARDA), Syria, have shown relationships between the physical characteristics of barley and the nutritive value of its straw. The objectives of the work reported here were to examine rice straw and study the relationships between morphological characteristics (height, harvest index, days to maturity), the proportions of botanical components, chemical constituents and nutritive value of the straw as measured by in vitro cellulase solubility. In addition, environmental effects on some of these characteristics were studied by examining inter-plant variations.

Widespread adoption of sheep systems based on mixed swards of white clover and grass may result in conservation cuts with a high proportion of clover, which will affect the intake of the silage or hay. The effect of proportion of clover in silage on voluntary intake was measured by offering mixtures of clover and grass silage with clover proportions of 0, 0.20, 0.40 and 0.60 with (S) and without (U) a ration of 600 g fresh weight per day of a barley, soya and fishmeal concentrate to 78 Finn Dorset ewes. The concentrate was formulated to have a crude protein content (CP) of 160 g per kg DM with 30 g per kg DM derived from fishmeal. The silages were made separately in 1984, with formic acid added at approximately 3.51 per tonne, from uninterrupted spring growths of perennial ryegass (Loliua perenre cv. Melle) cut on 16 June and white clover (Trifolium repens cv. Blanca) cut on 17 July and both were chopped. Mixtures of the two silages were made for each individual ewe separately each day, immediately prior to feeding.

Perez Hernandez, Robinson, Aitken and Fraser (1986) showed that the addition of a protected lipid to the diet of lactating ewes increased the fat content of their milk but had little effect on milk yield. The effects on milk composition were reflected in an improvement of approximately 10 per cent in lamb growth rate. In the experiments of Perez Hernandez et al. the response to the lipid supplement was tested using a diet with a high content of undegraded dietary protein. We now report the results of an experiment in which the response of lactating ewes to a ‘protected’ lipid was tested at three levels of protein intake. We also present data from a second experiment carried out to investigate the influence of the ‘protected’ lipid on the fatty acid composition of the ewe's milk.

High dietary levels of magnesium (> 2 g/kg DM) have been implicated as the main causal factor of urinary calculi in concentrated-fed lambs. Two experiments were performed to test this belief.

Three pelleted Diets A, B and C, contained magnesium in- the following concentrations, A 2.9; B 8.6 ; C 2.9 g/kg DM. Calcined Magnesite was used as the source of extra magnesium in Diet B.

Diets A and B were each fed to twenty four Blackface lambs and the control group of 160 lambs was fed Diet C and ad lib hay. Details of diets and estimated mineral intakes are shown in tables 1 and 2.

The effect of the level of energy intake (EI), crude protein content of the diet (CP), age and sex of growing lambs fed milk diets upon the retention of energy (ER) and nitrogen (NR) was studied.

A total of 114 lambs of the Churra breed removed from their dams at birth were used. The lambs were kept in metabolism cages and during the first two days of life were bottle-fed colostrum in quantity equivalent to 40% of their birth weight.

Afterwards milk-diets in which the protein-energy concentrations were between 15 and 35% were reconstituted at 180 g/kg of dry matter and given to the lambs according to the experimental design.

The importance of dietary fibre in rumen buffering has long been overlooked, despite the realisation that the primary mechanism to achieve maximum ruminant production is by the maintenance of a rumen pH suitable for microbial digestion and growth. It has been demonstrated that the rumen pH following cereal based supplementation is depressed to a far greater degree than when the concentrate supplement is non-cereal based (Rymer, 1986).

Two trials are reported, firstly in which silage fed to finishing lambs was supplemented with either dried molassed sugar beet pulp, a source of highly digestible fibre and low in starch; whole barley (55.6% of D.M. content as starch, (British Sugar, 1986)); or a commercial lamb creep pellet and secondly in which silage plus dried molassed sugar beet pulp was supplemented with undegradeable protein or not.

'Clean’ grazing is accepted as a successful method of overcoming poor performance in lambs and young cattle caused by nematode parasites of the alimentary tract and would virtually eliminate the need for regular anthelmintic treatment. However,it is impracticable on many grass farms and especially where sheep predominate. ‘Safe’ grazing offers a realistic alternative but has not been fully tested under field conditions. Two 2.8 ha paddocks of a predominantly perennial ryegrass sward were managed during the spring and summer of 1985 to produce two different levels of pasture nematode infestation for weaned lamb grazing during the Autumn of that year. Both areas were grazed by non-lactating mature ewes until 5 February 1985. The safe area(S) was then closed for two silage cuts and grazed for 11 days during early August by replacement dairy heifers. The contaminated area(C) was set stocked with 21 cross-bred ewes and their May born Suffolk x lambs per ha between 29 April and 28 August. Dung samples were collected from lambs grazing C at 8,12 and 16 weeks of age. Herbage and dung samples were collected from S and C at weaning (28 August) and 14 day intervals until lambs were removed from trial on 31 October. 138 lambs were divided into two groups by weight and condition at weaning and set stocked at 25/ha on S and C following an anthelmintic treatment. Lambs were selected for slaughter to produce carcasses of MLC fat class 2 or 3.

The East Friesland breed, developed as a dairy sheep, has a potentially useful role as a sire of first-cross breeding ewes from hill breeds of sheep. Advantages have been shown in terms of reproductive and lactation performance (Doney et al, 1983, Gunn, 1986) but the carcase conformation may reduce the acceptability of first-cross castrated male (wether) lambs. The characteristics of lambs derived from dairy-type breeds may be suitable for the heavy, lean carcase market (Butler-Hogg et al, 1985). The present study was undertaken as a pilot investigation of the potential growth rate and carcase composition of wether lambs over a range of live weights. East Friesland X Blackface (EFB) wethers were compared with a similar group of Border Leicester X Blackface (BLB) and a smaller group of East Friesland X North Country Cheviot (EFC) wethers.

Store lambs produced from hill ewes make a significant contribution to lamb meat production, particularly during the winter months. Studies of store stock marketing in Scotland reveal that hill store lambs are criticised frequently for unpredictable growth, poor conformation and low carcass and saleable meat yields (1,2). Trials using Scottish Blackface lambs of a single strain and source suggest that poor performance is a function of inappropriate feeding method and premature slaughter (3). This trial looks at strain ,feeding systems and strain:feed interaction as sources of variation in the growth performance and carcass characteristics of Scottish Blackface lambs.

Lewis Livestock Ltd., in liaison with Highlands and Islands Livestock Ltd., has initiated a cooperative marketing scheme involving the sale of store lambs from crofts in the Western Isles to finishing farms on the British mainland. The crofter-producers’ revenue depends on the sale price to finishers which is based primarily on liveweight recorded at the Island Collection Centres. Management problems have arisen due to losses in liveweight between weighing in the Islands and off-loading and weighing on mainland farms (time interval ranges from 14 to 26 hours) since finishers feel that they are being charged excessively for the weight of lamb as delivered to their farms. A study was undertaken to quantify the extent of this weight loss and try to identify predisposing causes.

The majority of lamb production in Britain is concentrated in March and April resulting in a glut of lambs during July-September when the guaranteed price is at its lowest. Trials were carried out over 3 years to assess the feasibility of lambing hill and lowground ewes in early summer when grass is at its most productive and little concentrates are necessary prior to lambing.

Trial 1 involved 20 bought-in Blackface (BF) ewes which were exposed to the tup in January/February in a sheltered field. Hay was available but no concentrates were fed. Ewes were outwintered and lambed in June/July when they were moved onto clean grazing. Concentrates were fed at the rate of 150g/d rising to 300g/d from 4 weeks pre-lambing to 10 days post-lambing. Results are shown in table 1.

Sward Surface Height (SSH) can be used as a guide for grazing control and recommendations are available for target SSH at various times of the year and at different levels of performance (Hodgson et al 1986).

188 mule ewes with Suffolk cross lambs were allocated to 2 target SSH, 1-6 cm and 6-8 cm. Each treatment was replicated twice and balanced for ewe age, liveweight and condition score and the age, sex and rearing status of the lambs. The areas grazed were under permanent grass (mainly perennial ryegrass) and received 255 kg N/ha applied in 4 dressings with balancing P. and K. The initial stocking rate was 14.7 ewes/ha with 23.2 lambs/ha. SSH was measured weekly using an HFRO swardstlck with 40 readings taken per area. SSH was maintained using a temporary electric fence to adjust the size of the grazing area. Adjustments were made on a pre-set pattern which took into account any difference between current and target SSH and any change in SSH over the previous week. The area adjustments are shown in Table 1.

Lambs were weighed at fortnightly intervals initially and at weekly intervals from the beginning of July. Lambs were drawn for slaughter at constant condition (3L). Ewes were condition scored and weighed at turnout (12th May), 6 weeks after turnout and at weaning (11th August).

The majority of early lambing flocks in the UK consist of crossbred ewes which do not normally cycle at a time consistent with an early January lambing. Oestrus stimulation is therefore necessary and is generally achieved by the use of progesterone-impregnated sponges and Pregnant Mares Serum Gonadotrophin (PMSG). Alternative techniques to sponges and PMSG to induce oestrus may become increasingly important in the future if restrictions are placed on the use of synthetic hormones. The present study aimed to

• a) Investigate alternative ways of advancing the breeding season naturally using vasectomised males and ovariectomised, oestrus-induced females. (Teasing).

• b) Assess whether treatment of ‘teased’ ewes with melatonin would enhance any effect of teasers.

Photostimulation is an effective means of manipulating reproductive activity in most British breeds of sheep. Short term light treatment can initiate oestrus cycles during June/July and thus provides the opportunity for autumn lambing (Williams, 1977). The most effective light treatments comprise a period of supplementary light followed by a period of long nights which requires controlled environmental housing. Recent investigations have demonstrated that melatonin treatment may replace the long night phase thus simplifying management (Williams, 1985). Attempts to dispense with the period of supplementary light by transferring Spring lambing Welsh Mountain ewes abruptly to long nights during early Spring were not as successful as the conventional type of light treatment (Williams, 1967). This investigation was undertaken to compare the response of adult Suffolk crossbred ewes given melatonin in the Spring with or without a priming period of supplementary light.