When emptying finishing barns, it is common practice on U.S. operations to dispatch pigs over a two- to three-week period with the heaviest animals being selected first. However, there has been little research carried out under commercial conditions on the effect of removing pigs from a pen at slaughter weight on the performance of the remaining animals. This study was carried out to investigate the effect of removing the heaviest 30% of animals from a pen on the subsequent growth performance of the remaining pigs.

Wean-to-finish production, which involves taking pigs from weaning to slaughter in the same building, is becoming widely adopted in the US swine industry. This production system is being advocated largely because of claims of improved animal performance and a decrease in labor needed for animal movement compared to conventional multiple-stage systems. One of the potential disadvantages of this system is the considerable underutilization of floor space during the early growth period if pigs are penned in the group sizes that are appropriate for finishing pigs. However, increasing the stocking rate initially at weaning, with some of these pigs subsequently being moved to another finishing facility, may increase output from the system. Therefore, the objective of this research was to investigate effects of initial stocking rate and of feeder-trough space in commercial wean-to-finish facilities on pig performance from weaning to slaughter.

The in sacco technique (e.g. Ørskov et al., 1980) remains the methodology with which the majority of rumen degradability estimates are made. However ethical, animal welfare and cost issues regarding the use of surgically modified animals plus the relatively slow rate at which samples can be examined (two samples per week using three sheep) have combined to compel researchers into developing alternative techniques. Precise, high capacity in vitro systems now exist. However the feed industry is unwilling to adopt these “new” values, partly due to having spent considerable time and effort creating databases of in sacco values which can be used directly in current feed evaluation systems. This paper describes modifications to an in vitro system that provides values similar to that obtained in sacco.

Acute (clinical) and subclinical rumen acidosis is a problem in many production systems where readily fermentable concentrates are fed. In previous experiments (Haubi et al., 2001) a model for subclinical acidosis using the Rusitec was presented. The objective of the present study was to establish a model for clinical acidosis, where excessive carbohydrate fermentation drops rumen pH below 5.0. The effects of N source on pH and feed dry matter degradation (DMD) before and after an acute case of acidosis were determined by comparing level of diet N and source (non-protein nitrogen [NPN] versus soya protein).

Fresh rumen contents are the most common source of inoculum for use to estimate in vitro degradation of ruminant feeds. However, the need to routinely access fistulated or slaughtered cattle to obtain rumen contents limits the availability of such inoculum and hence the applicability of in vitro methods by the commercial laboratories. Therefore, it would be advantageous, if rumen contents are preserved in sufficient quantity and used as a source for inoculum for use when there is a need to do so to estimate degradability of ruminat feeds. This study compared the suitability of frozen rumen contents as a source of inoculum to estimate in vitro rumen degradation of rapeseed meal (rapeseed) and grass nuts at various times.

One of the sources of variation in the in vitro gas production (GP) technique (Theodorou et al., 1994) is the inoculum source that is used. The time of rumen fluid collection in relation to the feeding time of the donor animals could greatly affect the microbial activity and hence fermentative capacity of the inoculum. This study was carried out to quantify both within day and between day variation in rumen fermentative capacity.

Considerable efforts have been made regarding the use of faecal material to provide a microbial inoculum for in vitro feed evaluation systems. However total gas production, rate of gas release and the extent of degradation of feeds incubated using faecal inoculum are lower than those incubated in a rumen fluid medium. It has been suggested that this is due to lower microbial activity, a consequence of the different microflora and reduced microbial numbers (e.g. Mauricio, 1999). Microbial populations are dynamic so, as their enzyme activity profiles change rapidly, little information is obtained from examining these. However, their hydrolytic activity as reflected by their ability to degrade specific substrates can be simply measured and provides a potential method with which to assess the quality of inocula with respect to their use in in vitro systems. The data presented here are from a larger study in which the differences between the hydrolytic activity of faecal material and rumen contents as influenced by the time of sampling were assessed in vitro.

In vitro gas systems characterise substrate degradation by estimating fermentation gas release over time. However, as this offers little information regarding feedstuff utilisation, the extent of organic matter degradation (OMD) must be measured to provide an estimate of the metabolizable end-products (VFA and microbial protein) produced. Systems where capacity is limited use either an incubation end-point derived partitioning factor (PF) to estimate degradation from gas or attempt to model OMD stoichiometrically from VFA analyses or assumed gas / VFA relationships. These estimates contain numerous errors. For instance the PF is not constant and the stoichiometric calculations used assume that all OM degraded is carbohydrate composed of hexose sugars. A further potential error is the estimate of the proportion of released gas that originates from VFA neutralisation, as this varies with buffer composition and both proportion and rate (i.e. concentration) of VFA production.

Despite little published research data (Ekström et al., 1966) the use of crimped cereal grain in the rations of high producing dairy cows has gained considerable acceptance. This is partly due to an earlier harvesting date permitting replanting up to three weeks earlier and to reduced storage costs. However, the main attraction is that high levels of crimped grain are readily consumed without apparently adversely affecting rumen fermentation. Although this appears to be in direct contradiction with the belief that crimped grain is fermented faster due the ensiling process, this information was probably obtained using the in sacco technique which tends to over-estimate processed cereal degradation due of fine particulate losses (e.g. starch granules). This study was therefore undertaken to characterise the degradation profile of crimped wheat grain relative to that of conventionally harvested material.

Grass is the main energy feed for cattle but it declines in digestibility and intake during the summer months and loses about 20% nutrients during ensiling and feeding in winter. Grass is also low in minerals and this has implications for cattle health and performance. It is thus essential to use supplements to boost digestibility and intake of grass and subsequently the performance of cattle. This study compared the effect of two supplements which are marketed as molasses based feed blocks (Booster with 12% crude protein or CP and HIPRO with 28%: CRYSTALYX) on the in vitro dry matter (DM) degradation of barley straw (Straw) and grass nuts (Grass). These blocks contained same energy (13MJ ME/kg DM) but different amounts of sugars (33-35%), oil (6-8%) and minerals (20 to 28%) and thus were considered appropriate for use as feed supplements to compensate for the deficits of nutrients that the cattle can face when consuming grass or straw. These forages represent a range of forage quality that can be found in the UK.

Although high genetic merit dairy cows are capable of peak yields in excess of 50 kg per day these are seldom maintained primarily due to an inability to satisfy energy requirements. Fats and oils are often incorporated into rations as a means of increasing dietary energy content. However, unless included at relatively low levels or in a protected form, lipid supplements may adversely affect fibre degradation in the rumen. The current data are derived from a study conducted to evaluate the potential of an in vitro model to assess the effects of oil supplements on forage organic matter degradation (iOMD).

The seeds from newer, varieties of determinate lupin grown in the UK are potentially a useful source of protein to livestock. Also, their ability to be cultivated in a temperate climate may afford the opportunity to reduce the dependence on imported protein sources such as soya bean meal. There is also currently interest in assessing the potential for harvesting whole-crop forage lupin (WCFL) as a high-protein forage crop for ruminant animals. The aim of the present study was to examine the nutritional value of WCFL samples harvested at different stages of maturity.

Chemical analysis have been useful in characterising both nutrient content and digestibility of forages but less useful in predicting voluntary intake by animals (Ward et al., 1982). Faeces is the product of eroding and synthesising digestive processes and consists of residues of feed and plant tissue, component of microbial and animal origin, for this reasons faeces should contain information about the amount and characteristics of the diet. Near infrared reflectance spectroscopy (NIRS) is widely used to predict quality characteristics in forages and several reports (Lyons and Stuth, 1992; Leite and Stuth, 1995, Coates, 1999) indicated that useful prediction of dietary digestibility in grazing ruminants using faecal NIRS analysis. It is assumed for different authors that rangeland herbivore faeces contains chemical bonds resulting from undigested residues and microbial fermentation and host animal digestion end products which can provide NIRS spectral information highly correlated with dietary crude protein and digestibility (Lyons and Stuth, 1992). The objective of this work was to develop NIRS equation calibrations to estimate acid detergent fibre (ADF), neutral detergent fibre (NDF) and nitrogen in faecal samples to be used as a tool to estimate diet composition in ruminant animals under grazing conditions.

Calpastatin, the specific endogenous inhibitor of the calpain system, is considered to be a principle contributor to variations in meat tenderisation (Parr et al., 1999). Previous studies have suggested that the differences in calpastatin activity in different ovine skeletal muscles could be influenced by muscle metabolic and contractile characteristics according to myofibrillar ATPase activity (Ouali and Talmant, 1990). The type of myofibrillar ATPase activity is largely determined by the content of slow or fast myosin heavy chains (Rivero et al., 1999). The present study was designed to investigate the relationship between calpastatin inhibitory activity and slow myosin heavy chain (MHC-s) and fast myosin heavy chain (MHC-f) expression.

Pale soft exudative pork (PSE) is a major problem affecting swine industries worldwide that results in significant economic loss because it reduces processing and saleable product yields. The PSE condition results from a rapid rate of muscle glycolysis early postmortem and a rapid drop in muscle pH while the temperature of the carcass is still high. Stress prior to slaughter can increase the rate of glycolysis and postmortem acidification. Blood acid-base has been used as an indicator of stress in pigs. The objective of this experiment was to investigate the relationship between blood acid-base status at slaughter and fresh meat quality in pigs.

The characterisation of muscle fibres has become increasingly important as the proportion of slow and fast fibre types are known to influence the biochemical and physiological properties of muscle during postmortem tenderisation (Ouali and Talmant, 1990). Current histochemical methods are labour intensive, time consuming and hazardous, requiring rapid freezing of samples in isopentane cooled in liquid nitrogen. The purpose of this study was to investigate an alternative immunochemical approach for identifying fibre types by examining the expression of slow myosin heavy chain (MHC-s) and fast myosin heavy chain (MHC-f) and comparing the data with classical histochemical techniques. Five different ovine skeletal muscles with known differences in fibre types distribution were studied.

Concerns over low levels of intramuscular fat and poor eating quality of meat from modern lean lines of pigs have focused attention on approaches to increasing the marbling fat content of pork. A number of techniques to increase intramuscular fat by manipulation of the nutrient composition of the diet have been evaluated. These have included feeding of protein deficient diets and of excess dietary leucine levels (Cisneros et al., 1996). Leucine is a ketogenic amino acid, the carbon skeleton of which can be used to synthesize fatty acids in muscle. In a previous study (Cisneros et al., 1996) feeding excess dietary leucine increased intramuscular fat and also improved muscle color. This study was carried out to validate those findings.

Increasing the n-3 polyunsaturated fatty acid (PUFA) content of ruminant products may be important in reducing the incidence of cardiovascular diseases in man. Previous experiments suggest that a-linolenic acid (C18:3n -3) in the form of whole linseed is extensively biohydrogenated both in vitro (Cooper et al., 2001) and in vivo (Wachira et al., 2000) and that some form of protection is required. By contrast the long chain PUFA’s in fish oils appear less susceptible to biohydrogenation (Wachira et al., 2000). The objective of the present study was to quantify the extent to which n-3 PUFA from different sources were biohydrogenated in the rumen and to determine the degree to which they were incorporated into plasma lipids.

Recommendations to improve the UK diet suggest an increase in the ratio of polyunsaturated to saturated fatty acids (P:S ratio) and a higher consumption of n-3 polyunsaturated fatty acids (PUFA). Ruminant meats have a poor P:S ratio, approximately 0.1 compared to the recommendation of 0.4-1.0 for the whole diet. However, the ratio of C18:2 n-6/C18:3 n-3 (the n-6:n-3) is well within the recommended value of <4.0 at approximately 2 and ruminant muscle also supplies longer-chain n-3 PUFA. By feeding lipid in a formaldehyde cross-linked protein matrix, rumen biohydrogenation can be avoided and the tissue PUFA level increased but with potential effects on oxidative shelf-life, colour and flavour of the meat. This trial investigated the fatty acid composition and quality of meat produced by feeding a protected lipid supplement (PLS).

Belgian beef production is mainly using double-muscled Belgian Blue animals finished indoors on all-concentrate diets or high-concentrate/maize silage diets. In relation to consumer health and in order to improve the “functional food” value of beef, it is attempted to increase its n-3 PUFA content using linseed or grass and grass silage in the fattening diet. The aim of this study was to investigate the effect of feeding grass or linseed at different stages of the production period on the intramuscular PUFA content of Belgian double-muscled beef.