The success of sheep breeding programmes involving sire reference schemes depends on effective oestrous synchronisation programmes that provide optimum pregnancy rates following fixed-time insemination (McKelvey & Simm, 1995). Effective oestrous synchronisation is characterised by low progesterone concentrations at the time of insemination. However in pedigree Suffolk ewes inseminated at a synchronised oestrus in early August, Dingwall et al (1995) reported that a significant number of ewes in some flocks had elevated progesterone concentrations at the time of insemination and, as a consequence, flock fertility was adversely affected. It is hypothesised that high progesterone reflects aberrant luteal activity arising from spontaneous ovulations following the preceding lambing. The present study sought to identify the incidence of aberrant luteal activity in Suffolk ewes during seasonal anoestrus and to study the effect on conception of interventional treatment of these animals prior to artificial insemination.

The breeding season of mature Mule (Bluefaced Leicester X Scottish Blackface) ewes at 57°N extends from September to April (King et al, 1995). Previous studies have shown that ewe lambs which become reproductively active in their first year of life have a shorter breeding season than mature ewes with both fewer and less regular oestrous cycles (Dyrmundsson, 1978a). The aim of the present study was to determine (i) whether ewes lambing in the autumn (i.e. during their natural mating season) would subsequently experience oestrous cycles and (ii) whether age has an effect on the pattern and duration of cyclicity and on ovulation rate.

Perinatal lamb mortality can account for up to 20% of annual lamb losses, and at least a third of these deaths can be attributed to maternal factors (Mellor, 1988). Improvement in the quality of maternal behaviour may, therefore, lead to a reduction in lamb deaths. In order to identify if there is a genetic component to the expression of maternal behaviour, the behaviour of a lowland (Suffolk) and a hill (Scottish Blackface) breed of parturient ewe were quantified after the birth of a single lamb.

The mammalian placenta is an active endocrine organ capable of synthesising and secreting a wide range of hormones and proteins. Pregnancy-associated glycoprotein (PAG) is one of these. It is produced by the binucleate cells of the placenta and becomes detectable in the maternal circulation soon after implantation (Zoli et al., 1992a). PAG occurs in cattle (bPAG), goats and sheep (oPAG), and has been used for early pregnancy diagnosis and the detection of embryonic death (Ranilla et al., 1994).

In the postpartum cow bPAG has a slow disappearance rate and is detectable in maternal serum until 100 days after calving (Zoli et al., 1992b). The present work was carried out to determine the rate of decline of oPAG in postpartum ewes and to test if the disappearance rate differed with litter size, age and diet.

The use of semi-skimmed cow milk diluent for liquid storage of ram semen is more convenient in Iranian sheep farming condition than other solutions. Preliminary tests showed that the motility and live percentages of ram spermatozoa were significantly (P>0.05) lower for semen samples were diluted in citrate buffer than semen samples in either tris buffer or semi-skimmed cow milk (Ahangari, 1996). This study was carried out for liquid storage of ram semen under Iranian farm conditions.

Lasalocid is a polyether antibiotic derived from the fermentation of streptomyces lasaliensis used as a coccidiostat in sheep. There are varying literature reports on lamb growth rate and feed intake when lasalocid is included in the diet of feedlot lambs. While some reports have shown that lasalocid enhances feed efficiency in ruminants by decreasing feed intake and either maintaining or improving rate of gain others indicate that lasalocid did not have any effect on lamb growth rates or feed efficiency (Stobart et al., 1987). Also, when lasalocid was fed to Chios lambs, growth rate was increased but there was no improvement in feed conversion efficiency (Hadjipanayiotou et al., 1988). There are no published data in the literature relating to the use of lasalocid as a growth promoter in the Awassi breed of sheep fed complete diets and the purpose of this study was to investigate the effect of lasalocid with two levels of protein on the growth rate and feed efficiency of weaned male and female Awassi lambs.

Wheat straw (WS) is used extensively for sheep feeding in Iran. The nutritive value of wheat straw is low and characterized by low crud protein and low available energy contents. Chemical treatments have often been used to increase the nutritive value of cereal straws (Sundstol & owen, 1984). It has been reported that the ammoniation of these straws increased dry matter intake and the daily gain of ruminants. In addition, Alkali treatment with Ca(OH)2 are effective and economically feasible for cereal straws (Sundstol & owen, 1984). The present investigation was conducted to determine the effect of treated WS with Urea and Ca(OH)2 or molasses on voluntary intake and growth rate of Iranian Baloochi lambs.

Lamb consumption fell from 11.1 to 7.5 kg / year / person between 1960 and 1990 and in recent years has fallen even further (5.9kg / year / person in 1994, source MLC). There are a number of possible reasons for this, but the high saturated fat content of lamb is likely to be a major contributer. Health considerations have led to repeated calls to reduce saturated fat intake (Dept of Health, 1994). Lamb has particularly suffered because it has a higher content of the saturated fatty acid stearic acid (C18:0) than other red meats. This has a high melting point and gives cold lamb its unpopular texture. The majority of lipid in lamb comes from de-novo synthesis of the saturated fatty acid palmitate (C16:0) from acetate in the adipose tissue by the enzymes acetyl co-A carboxylase and fatty acid synthetase (FAS). Palmitate can be elongated to stearate (C18:0) and this can be desaturated to the potentially healthier monounsaturated fatty acid oleate (C18:l), by the enzyme stearoyl co-A desaturase (SCD). The aim of this work has been to examine the fatty acid profile of lamb during growth and the enzymes involved in fat deposition.

Cortisol has been implicated in the mediation of both stimulatory and inhibitory effects of stessors on immune function in domestic animals, depending on the rate of secretion (Griffin, 1989; Munck, Guyre and Holbrook, 1984). Stressors differ in intensity and duration and it is likely that blood Cortisol profiles will differ accordingly. However, the importance, with respect to immune function, of the magnitude, duration and frequency of increases in circulating corticosteroid concentration is unknown. The aim of this study was to determine the effect of different profiles of Cortisol in the peripheral circulation, on antibody and cell mediated immune responses.

Glucose uptake by tissues is controlled by both insulin dependent and insulin independent pathways. One mechanism by which growth hormone is thought to increase the productive efficiency of ruminants is to antagonise insulin mediated glucose uptake (IMGU), thereby sparing glucose for non insulin mediated glucose uptake (NIMGU) dependent processes, such as milk production and growth (Rose and Obara, 1996). The aim of this experiment was to determine if growth hormone also has an effect on whole body NIMGU, by infusing somatostatin. Somatostatin prevents the release of insulin from the pancreas, thus, once insulin has cleared from the circulation, estimates of glucose turnover should be entirely non insulin mediated (Baron et al. 1987).

The gas production (GP) technique, (e.g. Theodorou et al., 1994; Cone, 1994) is increasingly used as an indirect measure of substrate fermentability in the rumen. However, there are few data concerning the effects of making changes to the various integral steps of the GP procedure. This study investigated the effects of inoculum concentration and method of inoculation on the GP profile of high temperature dried grass (HTDG).

The gas production (GP) technique has been established to estimate the rate and extent of rumen fermentation of feeds. Different types of apparatus have been developed to measure GP profiles, and these may have, an effect on the profiles observed. The aim of this experiment was to compare three such apparatus in terms of the GP profile obtained when all other aspects of the method were kept constant.

There is a need to be able to measure the methane producing potential of a range of feedstuffs under different rumen conditions in order to predict more accurately the amount of methane produced per animal. In vitro techniques using rumen fluid as an innoculum can be considered as models of in vivo rumen digestion and have been applied to estimate digestibility of feedstuffs. The in vitro gas production technique (Menke et. al, 1979) can be used successfully to estimate this but there have been limited attempts to use it to estimate the methane producing potential of feedstuffs. The objective was to assess the potential of the technique to do this.

Concentrate ingredients for ruminants are valued with the help feeding tables, based on chemical composition, the Tilley and Terry technique and nylon bag incubations. However, tables only give averages, which cannot be used for individual lots, and the nylon bag technique is expensive, time consuming and accuracy may be low. The aim of this research was to investigate the possibilities to obtain feed characteristics of a broad range of concentrate ingredients with the gas production technique (Cone et al., 1996).

Recently, the automatic in vitro gas production techniques (e.g. Cone. 1994; Theodorou et al., 1994) have been developed to study rumen fermentation kinetics. Many approaches have been taken. This work investigates the suitability of different methods for estimating the rumen fermentation of two starch rich feedstuffs.

The objectives of this study were a) to examine the effect of particle size and silage dry matter (DM) content on the rate and pattern of fermentation of fresh silages in vitro as an aid to modelling the in vivo situation and b) to compare the rate and pattern of fermentation of fresh silage samples with those obtained for freeze-dried material.

It has been suggested that the beneficial effects of yucca plant (Yucca shidigera) extract when used as a feed additive are based on its demonstrated ability to bind ammonium (Cromwell, et al., 1985; Johnston, et al., 1981). Benefits include the reduction of noxious gasses, the easing of waste management problems and the enhancement of livestock performance. However the amount of ammonium bound is very small (Ryan, et al., 1993; Quinn and Leek, 1994), and it is difficult to explain the observed enhancement of livestock performance, particularly in ruminants, in terms of this effect alone. Consequendy, in order to evaluate the overall effect of Y. shidigera extract on rumen fermentation in this study, samples of ruminal fluid from pre-conditioned hay-fed sheep were incubated with the extract and die effects on ammonium, pH and short chain fatty acids after 24 h were compared.

The in vivo digestibility of compound foodstuffs and ingredients can be predicted from laboratory techniques such as the in vitro rumen fluid (RF), the pepsin cellulase gammanase (PCG) and the neutral cellulase gammanase (NCG). There have been few comparative studies of these techniques using concentrate feed ingredients, especially since the addition of gammanase to the cellulase based techniques. Young et al. (1996) reported little difference between the cellulase based techniques in the accuracy of predicting in vivo organic matter digestibility (OMD) of concentrate ingredients, but both were superior to the rumen fluid technique. The objective of this study was to evaluate these techniques with a different set of foodstuffs which included less cereal and pulp samples but more maize by-products and oilseed meals.

The classical assessment of feedstuff cell walls has mainly been done using lignified material such as grasses; in which chemically poorly-defined fractions such as NDF and ADF were studied. Less effort has been put into the elucidation of cell wall polysaccharide structure and its effect on microbial degradation of non-lignified primary cell walls. In this experiment, the breakdown of cell walls of soya and com endosperm were studied, using the in vitro gas production procedure (Iheodorou et al., 1994).

Tree fodder is a vital dry season feed resource, used to supplement crop residues, on smallholdings in Nepal and other parts of the Himalaya. Farmers have a detailed and effective knowledge of the nutritive value of different types of tree fodder and the factors affecting this (Rusten and Gold, 1991; Thapa et al, in review). However, the implications of this knowledge for planning research to develop fodder resources and feeding strategies or for the effective delivery of research results to farmers are unclear. The study described here assessed the consistency between analytical indicators and farmers' perceptions of the nutritive value of tree fodder. The potential for using information from these two sources, in a complementary manner, to improve the focus of nutritive value assessment on farmers' needs was also examined.