Moving gilts from a strawed pen to a crate during farrowing profoundly inhibits oxytocin, probably as a result of a stress-induced opioid-inhibition of hypothalamic oxytocin release (Lawrence et al., 1992). Other work suggests that confinement of gilts in crates for 5 days prior to farrowing protects the gilt against stressinduced inhibition of oxytocin. As producers introduce gilts and sows into farrowing crates at variable times prior to farrowing it is important to identify the minimal period of exposure to crates required to confer adaptation. This work tested whether only a short period of adaptation (1 day) to farrowing crates prior to expected farrowing date (EFD) would be sufficient to prevent stress-induced inhibition of oxytocin.

Traditionally fed outdoor sows at commercial stocking rates can deposit onto soil in excess of 500 kg of nitrogen per hectare per annum from unused dietary nutrients. This has the potential to give rise to serious environmental pollution problems, and it is therefore important to seek methods to reduce this amount or to influence its pollution potential. One major determinant will be the extent to which it can be captured and utilised in grass growth, but this will be dependant on the extent to which the rooting activity of the pigs has destroyed the vegetation cover. This experiment was therefore designed to measure the impact of reducing dietary nitrogen inputs and maintaining grass cover by nose-ringing of sows on the long term changes in soil nitrogen content.

In recent years there has been an improvement in the genetic potential of dairy cattle through intensive breeding programs and of beef cattle through a shift from native beef breeds to Continental breeds. These potential improvements can only be realised if increased intakes can be achieved. If conserved forages are to meet these higher nutrient requirements then the intake of conserved forages should be maximised. Two potential methods by which silage intake can be increased are by increasing silage digestibility through more frequent harvesting of grass (Gordon, 1989) or by restricting fermentation of the resulting silage (Doherty and Mayne, 1996). The objective of the current study was to examine the relative effects of digestibility and restricting fermentation on the intake of silage with the aim of establishing the optimum approach to achieving higher nutrient intakes from ensiled forages.

It is now well established that finishing diets for beef cattle containing a high proportion of grass silage produce lower growth rates and a greater proportion of fat in the gain than high-concentrate diets offered at the same energy input. However, a major proportion of beef cattle in the British Isles are finished off grass and there is little information on the carcass composition of grass-finished cattle relative to those finished on high-concentrate diets. Two comparative slaughter experiments involving both steers and heifers have been carried out to compare grazed grass and concentrate diets in terms of performance and carcass composition at equal levels of performance.

Feed is the single largest cost in most animal production systems. Feed conversion ratio (FCR) is a commonly used measure of growth efficiency. Previous research has shown that FCR is moderately heritable and highly related to growth rate. While selection for FCR is beneficial to those feeding growing cattle for slaughter, any associated increase in the size of breeding females will mean this benefit will be at a cost to the calf breeder, as larger breeding cows require more feed.

The importance of maternal effects on birth weight and early growth is well known. These effects represent the contribution of the dam through milk and other aspects of mothering ability (i.e. uterine environment) (Meyer, 1993; Robinson, 1996). In this study a series of animal and animal maternal models were fitted using MTDFREML (Boldman et al., 1995) allowing estimates of direct and maternal genetic paremeters on weights of Welsh Black Cattle.

The idea that an animal of a given kind has, and grows to, a final or mature size is a useful one and several equations have been proposed that describe such growth to maturity (Winsor, 1932; Parks, 1982; Taylor, 1982). The Gompertz is one of these growth functions and describes in a comparatively simple, single equation the sigmoidal pattern of growth. It has 3 parameters, only 2 of which are important - mature size A and the rate parameter B. Estimates of A and B, however, are highly correlated. Considering A and B as a lumped parameter (AB) may overcome this problem. A Gompertz, or any other, growth function is not expected to describe all growth curves. When the environment (e.g., feed, housing) is non-limiting, it may provide a useful and succinct description of growth. The objectives of this study were to examine: (i) if the Gompertz equation adequately describes the growth of two genotypes of sheep under conditions designed to be non-limiting; and, (ii) if the lumped parameter AB has more desirable properties for estimation than A and B separately.

Fishmeal has been considered for many years an important component of the diet of pregnant and lactating ewes (Hovell and Ørskov, 1989). Recently concerns have been raised over adverse effects of industrial fishing on fish stocks (House of Lords, 1996) and use of animal protein in ruminant diets (GAFTA, 1997). Alternative sources of protein (vegetable sources) to fishmeal have been proposed but they are either expensive or lacking in supply of essential amino acids. The research reported in this paper examines the performance of an alternative protein source to fishmeal given in late pregnancy to ewes bearing multiple offspring and as a creep feed to lambs.

Grazed herbage is the cheapest feed available for dairy cows but total intake of nutrients from grazed pasture alone is generally insufficient to allow high yielding dairy cows to reach their production potential. Cows have their main daily meal following afternoon milking in the period up to sunset (e.g. Rook et al., 1994 ). In addition, both the DM content and water soluble carbohydrate (WSC) concentration of grass increase over the day (e.g. Orr et al., 1997) due to the loss of moisture and the accumulation of the products of photosynthesis. Based on this evidence, this study tested the hypothesis that dairy cows receiving strip-grazing allocations following the afternoon rather than the morning milking would show higher intake rates and consequently higher milk yields.

Twenty Holstein-Friesian cows (median calving date 10 February 1997) were each supplemented with 4 kg concentrates day-1 and strip-grazed a perennial ryegrass pasture in four groups of 5 cows.

Previous studies (Mayne and Laidlaw 1995) have shown that early turnout of dairy cows to spring pasture for a few hours per day (extended grazing) reduces silage intake and increases animal performance relative to that of animals retained indoors. The objective of the present study was to assess the effects of grazing severity and/or degree of silage restriction during the indoor feeding period on the response to extended grazing.

The development of grazing management strategies to optimise nutrient intake from grazed herbage requires an understanding of the factors influencing the dietary preference of grazing domestic ruminants. Although there has been considerable progress in understanding the factors influencing the dietary preference of grazing sheep, there has been comparatively little research with lactating dairy cows (Rutter et al., 1997). The aim of the experiment reported here was to study the dietary preference of lactating dairy cows grazing grass and clover.

The existence of genotype by environment interaction (G*E) can cause a change in the ranking of bulls tested in one environment when their daughters are subsequently milked in another environment. If the degree of re-ranking is large, the genetic correlation between milk production in the two environments will be substantially less than 1.0, with the implication that proofs made in one environment may not be reliable predictors of proofs in the second environment. The aim of this study was to investigate the effect of increasing the difference between environments, defined on the basis of herd average milk yield, on the genetic correlation (rg) for milk, fat and protein yield in Holstein Friesian dairy cattle in Ireland.

Agriculture is one of the major sources of methane in the UK and the major contribution is that from the ruminant animal. Most current inventories include evaluations of emission rates determined from ammals in respiration chambers. Methodolgy has been developed at IGER, North Wyke which enables measurements to be made with grazing animals (tunnel system). Preliminary measurements have indicated that methane emissions from grazing sheep in the tunnel system were lower than reported values for zero-grazed grass determined in chambers. The objective was to determine if these observed differences were a result of methodological differences.

Agriculture is one of the major sources of methane in the UK and the major contribution is that from the ruminant animal. Most current inventories include emissions from growing and adult cattle and it has been assumed that the young calf contributes little to the methane flux. There is a dearth of information for young cattle (65-110 kg liveweight) and the objective here was to provide methane data for this group of ruminants to assist in improving the UK inventories for methane.

The gas production (GP) profile of a feed is complicated by the fact that in addition to the ‘direct’ gas produced as a result of fermentation of substrate to gaseous products, there is also a proportion of ‘indirect’ gas produced. This indirect gas results from VFA produced during the fermentation reacting with bicarbonates in the incubation medium. If the VFA are produced at a different rate from total gas, then the estimation of the direct GP profile is more difficult. The object of this experiment was to observe whether there were any differences in the rates of gas and VFA production during the in vitro incubation of high temperature dried grass (HTDG), and how this might affect the shape of the GP profile produced.

The use of in vitro techniques is rapidly expanding because of an increasing need for routine and reproducible methods to obtain bioavailability data in addition to chemical ones. Furthermore in vivo methods are very expensive, an invasive technique for animals and may give non homogeneous results. In vitro systems could be divided in simulation systems (e.g. Rusitec, Czerkawski and Brekenridge, 1977) that attempt to closely reproduce the animal rumen ecosystem and are characterised by a higher level of complexity; and techniques that are mainly targeted to obtain biavailability data, without trying to mimic rumen metabolism (e.g. enzyme tests, Antoniewicz and Kosmala, 1997). As the fate of feedstufis in the rumen is mostly regulated by the micro-organisms, a rumen simulation system should primarily be characterised by a representative rumen microflora. The aim was to evaluate the possibility of maintaining a normal rumen microflora in an in vitro simulation system.

The UK metabolisable protein system proposed an approach for calculating the energy (termed fermentable metabolisable energy) available for rumen microbial protein synthesis. This approach does not take into account rumen undegradable organic matter (OM; mainly protein and starch) and ignores the dynamic aspects of the value, such as rate of fermentation. The aim was to evaluate three techniques to estimate OM apparently degraded in the rumen (OMADR) of different forages.

The quantity of gas accumulated in the in vitro fermentation technique (e.g. Theodorou et al., 1994) results from gaseous end-products of substrate fermentation, lysis of rumen microorganisms and CO2 released when VFA are neutralised by the carbonate-buffered medium (Beuvink and Spoelstra, 1992). However the quantity of gas produced from this acid-buffer interaction is not directly related to substrate fermentation and therefore needs to be quantified if gas evolution from substrate fermentation is to be estimated. This study examined gas release following the addition of acetic acid to a bicarbonate buffered medium and used a Gompertz equation to describe both the rate and total volume produced.

Two-stage techniques Tilley & Terry (1963) for the estimation of digestibility have 3 main disadvantages for use in developing countries with limited laboratory facilities. Carbon dioxide is needed to saturate the buffers; a centrifuge is necessary to separate residues from solubilised materials; and the methods uses pepsin as a proteolytic agent. The aim of the present study was to eliminate these three requirements for the faecal liquor method ( Omed et al., 1989), by replacing bicarbonate with phosphate buffer (Marten & Barnes, 1980), pepsin with biological washing liquid, and centrifugation with sedimentation.

A previous study (Mauricio et al., 1998) with 12 forage substrates (straw, hay and dried grasses) showed a high correlation between rumen liquor and faeces for total gas production and in vitro organic matter digestibility (OMD). However parameters estimated using faecal inoculum were generally lower man when using rumen liquor. To confirm this observation, a second study was conducted using maize silage and silages made from maize plant fractions.