Cow genetics, forage supply and quality, and feeding systems are relatively fixed in the short term. Therefore, it is important to establish the effect on intake and performance of a range of nutritional strategies. The purpose of the current study was to determine the effects on milk production and composition of nutritional strategies designed to increase forage intake by altering the composition of the concentrate supplement, and reducing the level of concentrate feeding.

Body fat and protein reserves at calving can affect milk production and composition (Garnsworthy, 1988; Moorby et al., 1996). Milk producers frequently feed their dry cows with a low quality diet to prevent them from becoming too fat before calving. However, the cow must nourish the foetus and develop mammary secretory tissues, which can be a problem if she is offered a low protein diet. This experiment was designed to test the interaction between energy and protein supplies during the dry period on changes in live weight (LW), condition score (CS) and muscle Longissimus dorsi depth (LD). Subsequent milk production and composition data are reported in a separate summary (Jaurena et al., 2001).

Nutritional manipulation during the dry period can alter subsequent animal responses to feeding in terms of milk yield and composition. Previous research has shown interesting differences in milk production and composition due to energy or protein supply in the dry period (Moorby et al., 1996). The objective of this experiment was to test the interaction between energy and protein supplies during the dry period on subsequent milk production and composition. Effects on live weight gains and condition scores are reported in a separate summary (Jaurena et al., 2001).

Rapeseed meal is a common protein supplement in ruminant diets that is characterized by high rumen protein degradability (Bertilsson et al., 1994; Vanhatalo et al., 1995). Appropriate treatment can however reduce ruminal protein degradability and increase the efficiency of protein utilization. RaPass (UM Feeds Marketing, Burton on Trent, Staffs, UK) is a commercial rapeseed meal product that made using the Maillard reaction. This is the non-enzymatic browning reaction between proteins and reducing sugars that protects protein from rumen degradation. Release of the protein at abomasal pH allows the peptide chains to be digested at an efficiency similar to that of untreated rapeseed meal (Moss et al 2000). Cows fed rapeseed meal that was treated to increase the rumen undegradable protein (RUP) content have been reported to perform better than those fed untreated rapeseed meal (Bertilsson et al., 1994). This study evaluated the potential of using RaPass as a protein supplement in dairy cow rations.

Chowdhury and Ørskov (1994) observed that heat production in sheep was reduced by approximately 10% below that at fasting when the animal was offered one third of the predicted maintenance requirement through intragastric nutrition. These authors also suggested that this indicated a glucose deficient state in the fasted animal, and that as a result the heat production at fasting was artificially raised. In agreement with Ørskov and MacLeod (1990), Chowdhury and Ørskov (1994) further stated that when measuring heat production to estimate basal metabolism animals should have their heat production measured when being offered one third of maintenance rather than fasting, although this was not tested by experiment. Birnie et al., (2000) reported that fasting heat production was influenced by the condition score of the cow. The objectives of this experiment were firstly to investigate the influence of maintenance and sub-maintenance levels of feeding on the observed heat production in nonpregnant, nonlactating dairy cows offered a more normal diet and secondly to further examine the influence of cow condition score on the fasting heat production.

San Pietro and Rittenberg (1953) reported that urea appeared to meet all the requirements of a satisfactory tracer. Urea is non toxic, not foreign to the body and it shows an even and rapid distribution throughout the total body water without any physiological effect. For these reasons in addition to its easy and accurate measurement, urea is an ideal candidate tracer to estimate empty body water in vivo. Total body water volume (urea space) can be estimated by dividing the total amount of urea infused by the increase in plasma urea concentration from prior to infusion until 12 or 30 minutes after mean infusion time. Kock and Preston (1973) reported significant relationships between urea space measurements and percentage of empty body fat and water in cattle. However, Andrew et al. (1995) using 21 Holstein cows showed that prediction of empty body water using the urea space technique only explained 31 % of the variation. The objective of this experiment was to use the urea dilution technique to estimate the body composition of lactating dairy cows and produce relationships between urea space and body fat and protein content.

The present energy rationing system used in the U.K., the metabolisable energy (ME) system (AFRC, 1990), is an empirical model incorporating a factorial approach to estimate the requirements of animals. Axiomatically, when this approach is adopted each component of the system must be accurately determined. Recent studies at this Institute using regression techniques have indicated that ME requirements for maintenance (MEm) are greater than that predicted using the equations of AFRC (1990), while the efficiency of use of ME for lactation (kl) is in line with the latter predictions (Kirkland and Gordon, 1999). There is a paucity of recent data relating to the efficiency of use of ME for tissue gain during lactation (kg), and the efficiency of use of body tissue for milk production (krl). The objective of the present study was to use regression techniques with data obtained from several recent calorimetric trials at this Institute to predict the MEm and efficiency factors of lactating dairy cows offered different diet types.

Using food industry liquid co-products can significantly reduce the cost of pig production (Scholten, van der Peet-Schwering, Verstegen, den Hartog, Schrama and Vesseur 1999) as well as reducing environmental pollution (Brooks, Moran and Beal 1999). Greenwich Gold (GG)(Amylum UK Ltd.) is a liquid residue, known in the trade as bottom stills, resulting from alcohol fermentation of wheat starch. Although the product is widely used by UK pig producers there is no published information on which to base a recommendation for maximum inclusion rate in diets for growing-finishing pigs. The objective of the study reported here was to assess the effect on growth performance and carcass quality of feeding pigs diets containing increasing levels of GG.

In Nigeria, the need to improve poultry production cannot be overemphasized because increase in population has necessitated an increase in the demand for animal protein. Increased egg production holds a unique position in bridging this animal protein supply (Longe, 1984). But the conventional energy sources like maize and sorghum are very expensive making feed to account for about 60% of cost of egg production. Alternatives are now being searched for in agro-industrial by-products because these by-products can be biodegraded to improve their energy value for poultry feeding.

Variety and location of production can affect the nutritive value of barley grain (Valaja et al 1997). Riviera and Dandy are the most commonly produced varieties of barley in Northern Ireland and it was an aim of this study to compare their nutritive value and to examine the effect of location of production. The growing and harvesting conditions have been shown to affect chemical and physical properties of cereal grain (Rogel et al 1987). A further aim was therefore to compare the nutritive value of Riviera and Dandy produced in 1998 (McCann et al 2000) and in 1999.

Spring barley is the most widely produced cereal in Northern Ireland. Riviera and Dandy are the main varieties but there is a lack of information regarding their nutritive value. Variety and location of production affect the nutritive value of barley (Valaja et al 1997). An aim of this study was to determine the nutritive value of Riviera and Dandy and also to examine the effect of location of production. Cereal grains contain a high level of non starch polysaccharides (NSP). The major NSP present in barley are β-glucan and arabinoxylan and supplementation with exogenous enzymes has been shown to increase digestibility to different extents (Yin et al 2000). A further aim of this study was to examine the effects of a mixture of β-glucanase and xylanase on these two varieties.

Variety and location of production affect the chemical composition of cereal grain (Valaja et al 1997). There are several varieties of Spring barley produced in Northern Ireland (NI) and in the Republic of Ireland (ROI). However, there is no information in the literature concerning the chemical composition of these varieties nor is there any information regarding location of production. The main aim of this study was to examine the effect of variety and location of production on the chemical composition of barley grown in these countries. Specific weight is traditionally used to predict nutritive value. However, a number of research reports including that of Stewart et al (1997) have not found a strong relationship between specific weight and chemical composition or nutritive value. For this reason the use of specific weight as a predictor of chemical composition was studied.

Wheat is often the largest single ingredient in piglet diets and therefore variation in quality may have a large effect on piglet performance. Currently there is no rapid method for the nutritive assessment of wheat. The livestock feed industry traditionally uses bushel weight as a predictor of nutritive value; however this assumption has recently been challenged by a literature review (Miller and Wilkinson, 1998) and by a weaner trial (Miller, Toplis, Arnold, Cook and Marshall, 2000). The aim of this experiment was to compare two more extreme bushel weights of Riband (64 v 78 kg/hl) than used in the previous experiment (Miller et al., 2000) when fed to weaned piglets with and without a xylanase enzyme. In order to amplify possible differences wheats were uncooked and included in the test diets at an atypically high level. We hypothesised that 78 kg/hl bushel weight would outperform 64kg/hl bushel weight (which is below the standard accepted by feed mills for feed wheat) and that enzyme supplementation would improve the performance of both wheats.

Soyabean meal (SBM) is used extensively in poultry rations. As the cultivation of soya bean is limited in Iran, annually a large amounts of SBM is imported. In recent years cultivation of some oil seed such as sunflower seed (Heliantus annus) is undertaken in some provinces of Iran. This plant will grow in cooler and dried climates than the soya bean or cotton plants. It contains 45 percent oil and a good source of protein and B-group vitamins. Due to high fibre content and low lysine content, use of sunflower meal (SSM) is limited in poultry feeds, but dehulled SSM is suitable for broiler feeds (Church, 1988 and Scott et al., 1982). The objective of the present study was to investigate the effect of SSM on performance of broiler chicken.

Severe negative energy balance (NEB) in the postpartum period of dairy cows may be associated with declining fertility but the mechanisms by which nutrition influences reproduction are complex, poorly understood and confounded by lactation. Hence, both chronic and acute nutritional restriction of beef heifers have been used as models to examine the effects of NEB on ovarian and endocrine responses in the absence of lactation. Plasma IGF-I concentrations gradually decreased until the onset of anoestrus (Stagg et al., 1999) but concentrations may be confounded with stage of the oestrous cycle, especially around ovulation (Mackey et al., 2000). Therefore, the aim of this study was to examine the effect of nutritional restriction on periovulatory oestradiol (E2) and IGF-I concentrations.

In vitro-produced (IVP) bovine embryos are used in a wide range of biotechnologies but develop less well than their in vivo counterparts and can give rise to foetal/neonatal anomalies after embryo transfer. The quality of bovine IVP embryos and the systems in which they are produced are traditionally assessed in terms of morphological and developmental criteria; namely, embryo grade and blastocyst formation rate. Lane and Gardner (1996) showed that mouse embryos selected for transfer on the basis of a low glycolytic activity (conversion of glucose to lactate), measured non-invasively, were 4 times more likely to implant than those selected randomly. Comparable data are not available for bovine embryos. The aim of this study was to assess linear glycolytic index of cattle blastocysts in vitro as a marker of viability. We have measured glucose consumption and lactate production by individual bovine IVP embryos grown in cell-free conditions and in a novel co-culture system (Orsi et al., 2000) involving confluent bovine oviduct epithelial cell monolayers on permeable supports. This preparation allows the epithelial cells to be fed by a nutritionally-rich medium via the physiological, basal, route, while the apical medium, containing the embryos, is more dilute, mimicking oviduct fluid.

Until relatively recently, breeding programmes for Holstein Friesian (HF) dairy cattle have focused selection procedures on increasing milk output with little emphasis on secondary traits such as fertility. As a result the fertility of the Holstein Friesian dairy animal is currently declining in the UK. This decline in fertility causes particular problems in seasonal calving dairy herds, where compact calving is crucial to overall performance of this system. In the Norwegian dairy cattle (NC) breeding programme, emphasis has been placed on a multi trait selection procedure including fertility and disease resistance. There is evidence that this selection procedure has resulted in improved fertility within the NC population. The present study is part of an overall programme comparing the performance of HF and NC cattle with respect to food intake, animal performance, nutrient utilisation, behaviour, health, fertility and longevity. The objective of the present study was to investigate possible differences in fertility between the two breeds when offered either a high or a low nutrient input diet based on grass silage.

Size, or its commonly used proxy live weight, is a necessary input when calculating the energy requirements of an animal. It is also a major factor in determining the intake capacity of an animal. The sole use of live weight as a determinant of size incorporates the implicit assumption that body fat and body protein mass are equivalent for the purposes of calculating energy requirements and intake capacity. Recent evidence indicates that this is not so in either case (Birnie et al., 2000; Friggens et al., 1998). The use of live weight may be acceptable where it can be reasonably assumed that there is a stable relationship between body fat and protein. However, when making breed or parity comparisons there is no reason to assume a stable relationship between body fat and protein. Meaningful comparisons can be made if live weights can be adjusted for differences in body fat content. In the applied context this means adjusting to a standard body condition score. This study provided the opportunity to examine the relationships between condition score and live weight in three breeds across three parities.

Traditionally, in most dairy cattle breeding programmes genetic evaluation of dairy sires and cows has been primarily based on 305-day lactation yield. To provide 305-day lactation yields many partial lactations have to be extended by adjustment factors resulting in overestimation or underestimation of 305-day yields which in turn leads to biased prediction of breeding values. Over the past decade there has been a considerable interest in using monthly test day records instead of 305-day lactation yield to predict breeding values of dairy cattle as early as possible and also to increase genetic gain through reducing generation interval. The main objective of present research was to estimate the genetic correlations between 305-day and monthly test day milk yields in Iranian Holstein dairy heifers.

Although it is not a substantial constituent of dairy cattle feed, there has been much work on the effects of feeding supplemental fat on reproductive performance. Supplemental fat increases the energy concentration of the diet and may lessen the effects of the negative energy balance post calving. Adding fat has been reported to positively influence reproduction in a number of ways, for instance increasing plasma progesterone concentration and increasing the life span of the corpus luteum (for a review Staples et al., 1998). A number of studies have demonstrated the importance of progesterone in early pregnancy and in particular the timing and strength of the post ovulatory progesterone rise. The aim of this study was to establish the effect of a dietary supplement of fat, in the form of calcium soaps of fatty acids, on reproductive function and in particular on post ovulatory progesterone levels in lactating dairy cows.