The Booroola Merino strain of sheep carries a major autosomal mutation (FecB) which increases ovulation rate (Davis et al., 1982). To map the gene, heterozygous sires (B+) were mated to non-carrier ewes (++). The female progeny were then examined by laproscopy to determine ovulation rates and these phenotypes used to assign progeny genotypes (B+, ++ or undetermined). Linkage analysis between the assigned Booroola genotype and a set of marker genotypes was used to assign the Booroola gene to a region of sheep chromosome 6 (OOV6) (Montgomery et al., 1994). These studies relied on accurate genotype assignment and a constant gene effect across animals and breeding seasons. This study aims to use regression analysis to verify the validity of these assumptions.

Not all commercial lines and breeds contain the best alleles for genes of economic importance. Introgression strategies transfer a gene from a non-commercial source to a commercial line by incorporating the favourable allele of a gene from the donor animals whilst retaining beneficial alleles affecting commercial traits in the recipient animals. This is achieved through generations of backcrossing and the resulting heterozygotes are selected and intercrossed to produce animals homozygous for the gene of interest. Animals produced from an introgression program can be inferior to commercial animals because of the contribution from the donor genome at loci not under selection. This genetic lag experienced in an introgression program can be partly attributed to the intercross as a higher number of animals are selected primarily upon genotype thereby reducing the selection intensity for other traits (Visscher and Haley, 1999). The chromosome segment containing the desired introgressed gene (linkage drag) can be quite large, e.g., 32 cM for a 100 cM chromosome in backcross 6 (Stam and Zeven, 1981). The aim of this study is to examine the genomic contribution of each generation to animals produced after the intercross and the level of homozygosity.

The increase in ovulation rate caused by the Booroola gene was first observed in the Booroola Merino strain of sheep (Davis et al., 1982) and the gene was subsequently mapped to sheep chromosome 6 (OOV6) (Montgomery et al. 1994). The low heritability of fertility traits and the desire to produce more lambs per ewe from meat breeds has lead to many crossbreeding programs seeking to obtain the benefits of the Booroola gene. However, many producers report animals carrying a Booroola allele to be lighter than non-carriers (G. Davis, personal communication). The Booroola Merino strain of sheep is typically lighter than recipient breeds used in the introgression programmes e.g. Romney. This study aims to determine whether the Booroola gene has a pleiotropic effect on liveweight or whether there is any evidence to suggest a closely linked quantitative trait locus (QTL) affecting liveweight that may ‘hitchhike’ with the Booroola gene.

The Thoka gene for fecundity, a gene which originally occurred in Icelandic sheep, was introduced to the UK in 1985 and through a programme of crossbreeding was established in Cheviot sheep (Russel et al, 1997). Ewes are now retained as "Thoka carriers" only if they have lambed in each of the first three years and had at least two sets of twins. The gene has been introduced into separate North and South Country Cheviot (NCC and SCC) lines which are now phenotypically indistinguishable from purebred animals and contain proportionately less that 0.2 of the Icelandic genotype. The purpose of this analysis was to determine the increase in fecundity in the two breeds and whether or not the reproductive response to the incorporation of the Thoka gene differs between NCC and SCC breed types.

In vitro cumulative gas production is a means to determine the rate and extent of feed fermentation. However, different apparatus and methods used at different laboratories cause variations in the gas production profiles (GPP) obtained. The objective of this experiment was to determine whether any significant difference between laboratories was observed when the same apparatus and method was used.

Leptin is the 16 kDa product of the obese gene secreted by white adipose tissue in proportion to energy intake. In several species, plasma leptin levels correlate with, and may be and endogenous signal of, the extent of body fat reserves. Leptin acts via the hypothalamus to regulate feed intake in rodents and may control gonadal activity through this same axis. Significantly, the mutant ob/ob mouse lacks functional leptin and is both hyperobese and infertile. Leptin may be a useful diagnostic and/or therapeutic aid in high-yielding dairy cows in which infertility is rising inexorably and is anecdotally linked to the scale of the early post-partum negative energy balance. Our objectives were to recombinantly synthesise, and raise antibody to, a leptin-protein conjugate and to develop a useful and specific RIA for ruminant leptin.

Acid detergent insoluble nitrogen (ADIN) is used in the UK Metabolisable Protein system (AFRC, 1992) to estimate the amount of indigestible nitrogen (N) in a feedstuff. A novel process has been developed which is intended to increase the proportion of undegradable protein in rapeseed meal. In situ work on this treated rapeseed product (TRSM) has shown a reduced rate of rumen degradation compared with the untreated product (UTRSM). However when these data were used in combination with ADIN content to calculate digestible undegraded protein (DUP), there was a minimal increase in DUP due to the high content of ADIN in the TRSM. There have been other cases where products have high ADIN content (e.g. distillery by-products; Webster, 1992) but when whole tract determinations of indigestible N were made, this was considerably lower than estimated from ADIN content. This raises some concerns about the use of ADIN to estimate indigestible protein for by- and treated- products. The objective of this study was to investigate whether the ADIN content of the untreated and treated rapeseed products was representative of the indigestible N.

The in vitro gas production (GP) technique was developed using strained rumen fluid (SRF) as an inoculum. This requires the use of surgically modified animals and it is questionable whether maintaining cannulated animals for this purpose can be justified. Faeces (FAE) have been used as an alternative inoculum, but while total gas volume tends to be the same, the rate of gas production is usually slower. This is probably because of a lower microbial activity in FAE. If the initial activities of the two inoculum sources were controlled, the differences between them may be reduced. The objective of this experiment, therefore, was to compare the GP profiles obtained when different concentrations of SRF and FAE were used, and the initial activity of the inocula equalised.

During steam treatment of lignocellulosic materials lignin is depolymerised (Zahedifar, 1996) to lower molecular weight phenolic compounds. Those phenolics may have protein precipitating capacity (PPC) due to bearing some hydroxyl groups on their molecule (Kawamoto et al, 1992) as do some other phenolics like tannins. Protein precipitating capacity of tannins may have a positive effect in ruminants by protecting proteins from microbial degradation in the rumen. The aim of this study was to assess the PPC of the phenolic compounds extracted from steam-treated wheat straw (STWS) and possible use of them to protect protein from rumen microbial degradation.

Associative effects of feed mixtures have been studied looking at the differences (i.e. gas production) between single and mixed substrates, and significant differences have been found when fodder trees were mixed (Rosales et al., 1998). This may not be the more appropriate form to analyze mixtures, because small departures from simple additivity may result in significant differences as the sum of all its components equals one. Taking this fact into account mixture designs have been suggested as an adequate tool when dealing with mixtures (Mead, 1988). Mixtures design are a special class of response surface designs in which the sample under study is made up of several components or ingredients, thus the response depends on the relative proportion of the components. The objective of the present study was to asses the power of mixture designs to identify associative effects in feed mixtures.

Regulated ReleaseTM (RR) is a patented liquid feed technology designed to reduce costs associated with protein supplementation. By causing the rate of ammonia release to mimic that of feed protein, through complexing urea and sugars, RR allows urea to act as a cost-effective ammonia source. However as molasses is used as the carrier it is difficult to demonstrate the efficacy of this technology using standard feed evaluation methodologies such as the artificial fibre bag technique of Ørskov et al. (1980). However the Reading Pressure Technique (RPT, Mauricio et al., 1999) can evaluate such feeds in vitro and the opportunity was therefore taken to examine the ability of RR to alter the rate and extent of fermentation by comparing a blended molasses with three RR molasses-based liquid feeds. As the majority of the CP in these feeds originates from urea rather than true protein, little if any gas will be produced from CP degradation. It was therefore hypothesised that an alteration in measured gas production, relative to that of Stockmol 20, would be due to the influence of RR technology limiting carbohydrate fermentation.

The differential rate and extent with which molasses-based feed supplements are fermented in the rumen, relative for example to starch-based concentrates, could be used to position these products in the market. There are, however, currently no data available to support such an assertion, in part due to the problem of how to assess degradation, as clearly standard feed evaluation methodologies such as the nylon bag technique (Ørskov et al., 1980) are inappropriate for liquid feedstuffs. The ability of the recently developed Reading Pressure Technique (RPT) (Mauricio et al., 1999) to examine such feeds was therefore utilised to describe or “fingerprint” the fermentation profiles of a range of commercially available molasses-based feeds.

Fermentation of the increasingly energy-dense rations offered to meet the nutrient demands of today's high yielding dairy cows ought to adversely rumen fibre degradation. Not only could rumen fluid pH be depressed below that assumed critical to cellulolysis for extended periods of time but the quantity of readily fermentable carbohydrate available will further exacerbate this effect. These, together with the reduced rumen retention time of feed particles associated with high feeding levels could significantly limit fibre degradation. This in vitro study was designed to identify the pH at which degradation becomes impaired, the extent of this depression and whether the effect varies according to the feedstuffs offered.

Considerable research efforts have been directed towards the use of cell wall degrading enzymes as feed additives. However, the factors affecting the response to a certain enzyme preparation are not well understood. A better knowledge of the enzymatic activities present in the preparations and their interaction with a substrate in presence of rumen fluid is needed. The objectives of this study were to characterise the main enzymatic activities of six enzyme preparations and to evaluate them in the presence of rumen fluid, using the in vitro Reading Pressure Technique (RPT).

The breakdown of bacterial protein in the rumen leads to a nutritionally wasteful cycle of protein breakdown and re-synthesis, decreasing the flow of microbial protein from the rumen to the small intestine (Williams and Coleman, 1992). Engulfment and subsequent digestion by ciliate protozoa was demonstrated to be the most important cause of bacterial lysis in mixed ruminal micro-organisms incubated in vitro (Wallace and McPherson, 1987). Despite their importance, little is known about the enzymes responsible for the digestion of bacteria in rumen ciliates. The objective of this study was to clone and characterise a lysozyme from Entodinium caudatum, a common rumen protozoan important in the ingestion and breakdown of rumen bacteria (Williams and Coleman, 1992).

The amount of rumen escape protein is commonly determined with the nylon bag technique. However, there is also an in vitro technique described using a protease of Streptomyces griseus (Aufrère et al., 1991; Cone et al., 1996), allowing systematical analysis of protein quality in a large number of samples. The aim of this study was to identify the influences of growing conditions on content of rumen escape protein in grass and grass silage and to investigate the relationships between rumen escape protein determined in vitro and in situ and chemical composition.

Because feed evaluation of new feeds for animal nutrition requires in vivo trials, which can be expensive, harmful to the animals and time consuming, alternatives have been developed. in vitro techniques are used commonly for many farm animal species. However, in vitro data do not always predict in vivo data satisfactorily. As many processes in the gastro intestinal tract of different animal species are comparable also the digestibility of feeds may be comparable. The aim of this research was to identify similarities in digestibility coefficients between different farm animal species. If it is possible to use in vivo data of one animal species for the evaluation of alternative techniques for another species, this would enlarge existing data sets, accelerate the validation of new techniques and reduce the number of harmful animal trials.

Performance horses are often fed very energetic diets including large amount of grains. Thus, a important quantity of soluble carbohydrate is bound to reach the hindgut, altering biochemical and microbial composition of the intestinal contents (Julliand et al., 1999) and leading to a wide variety of diseases like colic, laminitis and diarrhoea (Clarke et al., 1990). In high concentrate rations, live yeast cultures have been reported to stimulate specific groups of bacteria, and moderate large ruminal pH decreases (Williams et al., 1991). Therefore, this trial was designed to evaluate the effect of a live yeast culture preparation (Yea Sacc1026™) on the activity of the intestinal ecosystem (caecum and colon) of horses fed high fibre (HF) or high starch (HS) pelleted feeds. This current summary reports only the results of the nutrient digestibility in vivo and the ability in vitro of large intestine fluid contents to degrade straw.

In Iran, wheat straw which is produced in huge amounts has been used in animal feed. However, the use of straw as animal feed is limited by its low nutritional value and its low nitrogen content. Various chemical delignification methods to improve the digestibility of straw have extensively investigated (Sundstol and Owen, 1984). Biological methods of treating straw using fungi such as white-rot-fungi have also been reported (Zadrazil, 1984). The solid state fermentation (SSF) of wheat straw with white-rot fungi is a complex process which is influenced by factors such as the species of fungus, substrate, temperature and moisture (Zadrazil, 1984). The objective of this study was to investigate the effect of pre-treating the straw with urea and incubation with two species of Pleurotus fungi on the chemical composition and digestibility of wheat straw.

Current pressures to extensify agricultural systems are leading to more emphasis on incorporating legumes, such as white clover, into swards thus reducing the amount of fertiliser nitrogen used. Cattle fed clover rich diets often receive poloxalene (Bloat guard ®, Agrimin Limited) as a feed additive to prevent bloat. Poloxalene is a surfactant, reducing surface tension of bubbles caught in froth, and thus reducing foam formation in the reticulo-rumen. The n-alkane technique (Dove and Mayes 1991) to measure intake is widely used in grazing experiments. Alkanes are saturated hydrocarbons found in the waxy cuticle of plants, which are used as internal markers to estimate herbage intake and to determine dietary composition in grazing ruminants. Animals are typically dosed with a controlled release bolus (CaptecTM FERNZ, New Zealand) containing an even-chained synthetic alkane (C32). Mean daily dry matter intake is calculated using the assayed release rate of C32 and the concentrations of C32 and C33 in herbage and faeces (Dove and Mayes, 1991). Given that poloxalene is a surfactant, it could potentially interact with the n-alkanes and therefore invalidate the technique. The aim of this experiment was to investigate the effect of including poloxalene in the diet on the n-alkane concentration in faeces from dairy cattle.