Adipose triacylglycerol is mobilised during late pregnancy in humans and rats: the liberated fatty acids are incorporated into very low density lipoprotein (VLDL) by the liver and secreted into the blood stream. Similar hypertriacylglycerolaemia was also found in late-pregnant sows (Wright et al, 1995). It has been shown that VLDL can be separated into two subfractions by heparin-affinity chromatography. The proportion of VLDL-subfraction 2 (higher affinity for heparin) from pregnant sows was related to piglet mortality. The purpose of this investigation was to extend the study to seek relationships between fat deposition and plasma lipids, VLDL lipids and VLDL-subfractions in growing pigs. As most of the fat deposited in the adipose tissue of neonatal pigs is derived from the plasma lipoprotein, it seemed likely that the rate of fat deposition would be influenced by the concentration and nature of available lipoprotein in the plasma.

Post-weaning diarrhoea (PWD) is a common problem in the pig industry. Following weaning, severe diarrhoea may occur due to colonisation of the small intestine by opportunistic pathogens, predominantly E. coli. Many serotypes of E. coli are associated with the disease but organisms with the K88 fimbrial antigen predominate. The K88 antigen enables E. coli to adhere to the mucosal surface of the small intestine thereby facilitating colonisation. Many feed additives are available which reputedly inhibit this binding. The aim of this project was to assess whether a selection of these feed additives could inhibit binding in an in vitro model.

Wheat is a major source of energy and may account for over 50% of the pig's diet. Although there are differences in the energy and protein content of different cultivars of wheat, these factors have not been correlated with differences in the growth of pigs (Bell and Anderson 1984). The objectives of this trial were to compare the growth performance of young pigs offered diets differing only in the cultivar of wheat used and to establish whether variation in growth could be explained by other chemical or physical properties of the wheat.

72 crossbred (Large White x Landrace x Large White) pigs were selected at weaning at a mean age of 24 days and mean weight of 7.86 kg. They were allocated by weight in pairs in a randomized block design to one of six dietary treatments in 6 replicates and over three time periods.

Biological subcellular membranes (mitochondria and microsome) contain relatively large amounts of phospholipids which are rich in unsaturated fatty acids (UFA) and are readily susceptible to lipid peroxidation. Thus, it is believed that peroxidative changes in meat is initiated at the membrane level. Monahan et al. (1990) have shown that these membranes are particularly rich in α-tocopherol (AT), hence, the effects of increased dietary supply of α-tocopheryl acetate (ATA) and UFA (from full-fat rapeseed; FFR) on AT content, fatty acid profiles and peroxidative changes in porcine mitochondrial and microsomal fractions were studied.

The north east of Scotland has seen poor harvest seasons in five out of the last ten years. The 1995 season was predicted to be one of the highest yields for a number of years, however, 14 days of continuous rain at harvest resulted in a high proportion of poor quality, sprouted and shrivelled grains, which, if not properly dried, were of dubious micro-biological status. The price of feed wheat is usually determined by the specific weight if it falls below the minimum standard of 72 kg/hl, however, de Lange et al (1993) expressed concern that bushel weight was not a good indicator of DE content. The objective of this experiment was to determine how the commercial assessment of such grains linked to feed value in poultry and the performance of pigs.

Hill and Matrone (1970) postulated that chemically similar minerals would manifest biological similarity. As a result there would be competitive antagonism for inclusion in metabolic processes, including intestinal transport. Such interactions have been reported for copper (Cu) and zinc (Zn), where the chronic over supply of Zn reduced Cu absorption (Fischer, Giroux and L'Abbe 1981). Previous work ( Lowe, Wiseman and Cole 1994) has indicated that when Zn is supplied as a chelate that antagonism to its absorption from calcium may be overcome. As many diets, specifically for piglets, now appear to contain very high levels of supplementary Zn it is appropriate to evaluate the effects of its dietary supplemental source on other mineral uptake.

24 adult female CD rats (327g, SE 4.7) were randomly divided into four groups and fed a maintenance diet (27.mg. kg-1 Cu) on a free choice basis containing 28mgZn.kg-1 to which 65mg of supplemental Zn.kg-1 from four different sources was added for the duration of the study.

Since the 1970's, many studies have been performed to estimate ileal digesibility using different methods for digesta collection. The methods frequently applied for quantitative collection are re-entrant cannulation or ileorectal anastomosis (IRA). Methods involving the use of a marker include the post- valve “T” caecal (PVTC) and simple ileal “T” cannula. Recent studies showed that PVTC has a number of advantages over the simple “T” cannulation methods (van Leeuwen et al, 1991; McCracken et al, 1996). The present study afforded the opportunity to (1) compare the PVTC with the IRA method, (2) compare the use of Cr2O3 and TiO2 as indigestible markers (3) evaluate the PVTC method for quantitative collection of digesta, using a range of diets of different fibre content.

The PVTC experiment was performed in Belfast. Twelve pigs, approximately 20kg, fitted with post valve “T” caecal cannulae according to the procedure introduced by van Leeuwen et al(1991), were randomized to 4 diets based on wheat (W, 760 g wheat/kg), wheat/middlings (WM, 380g wheat, 380 g middlings/kg), wheat/bran (WB,380 g wheat, 380 g bran/kg) or recombined wheat (WR,570 g flour, 130 g middlings, 60 g bran/kg) using a four period cross-over design.

Due to the development of early maturing maize hybrids tlie area of maize grown for silage in the UK has increased markedly. Although there is an important positive relationship between maize silage DM content and silage intake, which farmers should try and take advantage of, high DM crops are difficult to consolidate and as a result are more susceptible to aerobic instability. As a result farmers are tending to harvest crops earlier to reduce the risk of aerobic instability but in so doing they sacrifice silage intake. The problem of aerobic instability exists not only during the winter feeding period but also when maize silage is used as a buffer feed during the summer. The aim of the current study was to determine the effect of a blend of partially neutralised organic acid salts based on propionic and formic acid on the DM loss during ensiling, fermentation characteristics, nutritive value and aerobic stability of maize silage.

Calliandra is a proteinaceous leguminous browse for ruminants. Its PA content may however reduce its nutritive value. The negative effects of PA can be reduced by treatment with polyethylene glycol (PEG). Tannin-protein complexes are stable at pH values up to the isoelectric point of the individual protein, and may dissociate at lower or higher pH values. The aim of the study was to determine the PA concentration of Calliandra, and to evaluate the effect of PEG and pH on the formation of complexes between BSA and compounds from Calliandra extracted with aqueous methanol.

Leaves (containing the leaflets and petioles) were harvested from Kenya Agricultural Research Institute regional research center, Embu, in the central highlands of Kenya. Leaves were oven dried (50 °C for 48 h) and were milled (1 mm aperture). The top 30 and lower 30 cm leaves were harvested from 2.5 year old plants.

Extensive enzymic degradation of proteins in grasses during ensiling, as well as the ease with which the remaining proteins are degraded in the rumen is undesirable. Formaldehyde has bacteriostatic properties, and can protect plant proteins from degradation in silage and in the rumen (Henderson, 1993). Tannins form complexes with proteins and may protect silage protein and improve amino acid utilization in ruminants. Earlier results with tannins (Salawu, et al, unpublished data) were promising but inconclusive because of poor fermentation. Silage fermentation can be improved by the use of formic acid (Barry, et al, 1978). The aim of the experiment was to compare the effect of tannins [quebracho tannins (QT) and mimosa tannins (MT)] or formaldehyde (F) or formic acid (FA) or a mixture of tannins/FA or formaldehyde/FA on silage composition.

Calliandra calothyrsus is a promising tropical leguminous browse, native to South America, but now planted in most parts of the tropics and subtropics. It is a fast growing plant, rich in proteins and can do well on poor soils (NRC, 1983). Its high content of condensed tannins has however limited its use as a feed for ruminants. The chemical composition and degradability in vitro in a consecutive batch culture (CBC) system were studied.

Preferably, a crop for silage should be immediately ensiled after harvesting. However, this is not always possible in research situations when a large number of laboratory-scale silos have to be prepared. Thus, in many cases the chopped material is frozen and ensiled at a later date after defrosting. Richard and Allen (1992) and Nelson and Bozich (1996) have shown that freezing vegetative material may increase cell-wall contents, which in turn, may affect nutritive value. The current study was conducted to determine changes in the composition of fresh and frozen stover, ensiled with and without a cell-wall degrading enzyme solution.

Islam et al. (1996) reported effects of variety, fertilizer nitrogen (N) and sowing date on the botanical fractions of straw from oats grown at one site in NE England (ADAS High Mowthorpe). The present study investigated the effect of the same factors on straw quality from oats grown at a site in the SW Midlands (ADAS Rosemaund). Treatment effects on both botanical fractions and in vitro digestibility were measured, and the relationships between botanical composition and in vitro digestibility were investigated.

Wahed et al. (1990) showed that the intakes of barley straw in untreated, long form, were increased by 0.35 and 0.57 when the ad libitum amounts offered to sheep were increased from 18 to 54 and 90 g dry matter (DM)/kg live weight (M) daily, respectively. The quality (in vitro digestibility) of straw consumed also improved with offer rate. There is no such information available for oat straw. In view of the latter, and the increasing use of oats in human foods and the greater availability of oat straw for feeding, the present experiment investigated whether the intake of oat straw by sheep could be increased by increasing the amount offered.

Extension literature on upgrading straws in the tropics (e.g. Schiere and Ibrahim, 1989) advocates applying 1 kg of 40 g/kg urea solution per kg air dry straw and storing under plastic for 4 weeks. Surprisingly, there is little published information on responses to urea solution concentration and amounts to be applied in order to improve digestibility of organic matter (OMD) and maintain alkaline pH to enable preservation of treated straw. The present experiment aimed at providing such information as part of a study to assess the potential of animal or human urines for upgrading straw and bearing in mind that urines contain a range of urea concentrations.

There are currently about 0.29 x 106t of oat straw available for feeding in the UK and although this is much less than for other cereals, there are indications that oat straw is of higher nutritional quality (see Givens and Moss, 1995). There is increasing interest in the use of oats and naked oats in human foods and the quantities of oat straw are likely to increase. Whilst some earlier work (Tuah et al., 1986) showed that variety of oat could influence the nutritive value of its straw, there has been no systematic study of the effect of agronomic factors such as sowing date, fertiliser use etc. This experiment examined these issues.

Of the many procedures employed for in vitro maturation (IVM) of mammalian oocytes, most rely on inclusion of serum in the maturation medium. The presence of serum, however, confounds investigations of the effects of discrete factors (nutrients, hormones, etc.) on oocyte development and could pose an additional problem in terms of exposure of oocytes to pathogens (Bavister, 1995). The present study investigated the extent of nuclear maturation of porcine oocytes in vitro in the absence of serum. Nuclear maturation represents the attainment of meiotic maturity and together with cytoplasmic maturation, which facilitates male pronuclear formation following sperm penetration, is a pre-requisite for normal development following fertilization.

Individual culture of porcine embryos facilitates precise evaluation of developmental progress during crucial stages of preimplantation growth in vitro. This approach was applied to embryos, collected at different stages of development, from young pre-pubertal gilts induced to ovulate following gonadotrophin treatment. The present study also examined embryo development in 2 media produced for porcine egg culture, NCSU-23 (Petters and Wells, 1993) and modified Whitten's Medium (mWM; Beckmann and Day, 1993).

Embryo transfer in the pig is still very experimental but reduced generation intervals and accelerated genetic improvement could be achieved if younger gilts could be stimulated into an early puberty and used as donor animals. Stimulation of precocious puberty using a single dose injection of hCG and PMSG (PG600) has been shown to be successful (Schilling and Cerne, 1972). Pressing et al (1991) found that at 100 days gilts did not respond to pulsatile GnRH administration inferring that the pituitary-ovarian axis is not mature prior to this time. In this experiment exogenous gonadotrophins were administered to gilts between 100-180 days old in order to assess their ovarian response at both the stimulated heat and a second, natural heat.

The duration of ovulation in pigs may contribute to embryo mortality, as later ovulated ova, which become the least mature embryos, are unable to contend with the changing uterine environment (Pope, 1992). The shorter ovulation of spontaneously ovulating sows, which were mated, compared to induced sows, which were not mated (Soede et al, 1992), suggested that the mating itself may reduce the length of ovulation. The current study determined the effect of mating in the early oestrus period on both the timing and duration in recendy weaned, spontaneously ovulating sows.