In many research situations it is useful to store silage frozen for use in future experiments. However, previous studies using fresh grass have demonstrated that freezing and thawing induces changes in the chemical composition of the herbage (Beever et al., 1974; MacRae et al., 1975). Of particular importance are the reductions in nitrogen and increases in carbohydrate solubility. The situation with grass silage is uncertain. The aim of this study was to examine the effect of freezing and thawing grass silage on intake, liveweight gain, rumen parameters and digestibility in steers.

Quebracho (Loxopterygium loetzil) tannins (QT) are condensed tannins that reduce the digestibilities of nutrients in ruminants (Robbins, et al, 1991), probably by forming complexes with the dietary protein and carbohydrates and reducing microbial activities (Makkar, et al, 1988). Browse Plus (BP), a commercial preparation of polyethylene glycol (PEG) has recently been used to improve the nutritive value of tannin-containing browses. Trials on commercial farms in Zimbabwe have demonstrated that BP improved the nutritional performance of cattle fed high tannin diets (Anon., 1995). Some in vitro work tend to support these findings (Acamovic, et al, 1995). An experiment to study the effectiveness of BP in ameliorating the effects of QT on the rumen environment was conducted.

Cattle fed grass silage generally have higher fatrprotein ratios than cattle fed other forage-based diets. This has been shown to be at least partly due to impaired protein accretion (Gill et al., 1987). It is however unclear whether differences in fat accretion are also responsible. This experiment was designed to compare rates of whole body fat metabolism, rates of fat deposition and carcass composition between grass silage and dried grass diets fed over a range of ME intakes.

Controlling the timing of ovulation in cows that fail to conceive after insemination would provide a further opportunity for scheduled rebreeding in a group of cows to save time and optimise results. The ear implant Crestar containing the synthetic progestagen norgestomet provides a means of achieving this control (Sinclair et al., 1992; Lowman et al., 1994). Removing the implant on day 25 after oestrus results in less false positive pregnancy diagnoses than removal on day 21 with the implant in place for nine/ten days. However, treatment of beef heifers with a norgestomet implant towards the end of luteal phase to control oestrus and ovulation is associated with development of a persistent ovulatory follicle and reduced pregnancy rate (Mihm et al., 1994). The objective of this study was to determine the effects of treating beef cows with one or two norgestomet implants on the development of the dominant ovulatory follicle of the second follicular wave.

As part of a long term study to assess the suitability of beef cow genotypes, differing in body size and milk potential, for different forage environments within the UK, eight purebred Aberdeen Angus (AA; considered to be small and relatively non-milky) and eight purebred Simmental (Sm; considered to be large and relatively milky) heifers were placed on different levels of annual energy intake. Changes in body composition and milk yield were recorded and related to early post partum ovarian activity.

Reproduction is the main factor limiting the production efficiency of beef suckler cows and the prolonged post-partum interval is a major factor contributing to this poor reproductive performance. This interval is determined by a number of factors of which nutrition and the suckling effects of a calf are the most important. The aims of this experiment were to determine the effects of energy level post-partum and suckling on the PPI of cows in a low to moderate body condition at calving

Vegetable proteins, including soya-bean meal (SBM), can only be included in diets for newly-weaned piglets in restricted amounts as they can induce a transient local gut hypersensitivity. This hypersensitivity may be a causative factor in post-weaning diarrhoea. The object of the current experiment was to assess whether protease treatment of SBM could reduce in vitro antigenicity of SBM and improve its nutritional value when fed to newly weaned piglets.

Soya-bean meal was treated for 3 h at 50°C at 800 g water / kg. Treatment was carried out at pH 4.5 without and with lg protease P2 (Finnfeeds International Ltd) / kg soya-bean meal dry matter (DM). Treated SBM was neutralised and dried at 65°C before inclusion into diets. The diets were formulated to contain 14.5 MJ Digestible Energy (DE), 190 g crude protein (CP) and 12 g total lysine / kg.

While there is little information in the literature on the effect of feed freshness on acceptability, feeds containing oxidised or rancid fats are thought to be unpalatable. Both free fatty acid level and peroxide level have been used as measures of fat quality and suitability for feeding especially to young animals. Neither is now considered a reliable predictor of animal performance (Carpenter, 1968). Connolly et al. (1970) found that pig performance was unaffected by high levels of peroxide in the diet or prolonged storage and concluded that it is doubtful if toxicity from lipid peroxides would arise in practical feeding. The aim of this study was the examine the effect of feed freshness on intake and growth of suckling and weaned pigs, using free fatty acid and peroxide levels as indicators of freshness.

The benefits of creep feeding in a 3 - 4 week weaning system is uncertain. Sow milk yield peaks at 3 - 4 weeks postpartum and the need for supplementary feed to maintain growth rates of suckling pigs is minimal. The objective of this study was to quantify creep feed intake by suckling pigs and to assess the effect of creep feeding on piglet growth and weight at weaning when weaned at 26.0 (s.e. 0.6) days of age.

The results reported here were obtained by combining data from 296 litters of suckling pigs on 5 creep feeding trials. The five trials involved comparison of diets and management systems as follows: (A) effect of quality of creep feed (high quality starter diet vs medium quality starter diet vs a pelleted cooked cereal); (B) comparison of meal and pelleted diets; (C) the effect of form (reconstituted calf milk replacer - 20 % dry matter vs solid pellet vs peat primer offered with a solid pellet); (D) effect of feed freshness (fresh creep vs 30 day old creep vs 60 day old creep feed); (E) effect of creep feeding piglets on pre-weaning performance.

Spray dried plasma protein (SDPP) has been used as a replacement for expensive milk based ingredients in starter diets in the US over the past few years. The objective of this trial was to assess dried blood products as a replacement for dried milk products and fish meal in diets fed to pigs for four weeks after weaning.

Thirty six mixed sex groups of 16 pigs, weaned at 22-28 days of age and weighing 7.6 (s.e. 0.1) kg, were used in this trial in a factorial design of two starter diets (control and 10% SDPP (AP920) - American Protein Corp., Ames, Iowa) for 14 days from weaning, followed by two link diets (control and 2.5% spray dried blood cells - SDBC (AP301)) for 12 days. Composition of diets is shown in Table 1. All pigs received a common weaner diet from day 26 to day 49 (34 kg liveweight approx).

Previous studies on glucosinolate (GS) toxicity have focused on progoitrin since it is the most abundant GS in single-low varieties of oilseed rape. Progoitrin levels have been greatly reduced in new double-low varieties, but levels of indole GS (glucobrassicin and 4-hydroxy glucobrassicin) have remained relatively static and represent a much higher proportion of total residual levels. In this study, the aim was to evaluate the metabolic and toxic effects of rapeseed differing in indole GS and progoitrin concentration.

Equations based on the chemical composition of feedstuffs have traditionally been used to predict the energy value of cereal-based diets for pigs. However, the dietary fibre fraction is the greatest source of variation in predicting energy value and it is recognised that the predictive power of equations could be improved by the use of more detailed chemical analysis of the fibre fraction, as opposed to using more traditional gravimetric techniques which do not define specific chemical entities. The potentially fermentable fraction of dietary fibre is the non-starch polysaccharide (NSP) portion and there are methods available to allow the routine measurement of total NSP and its constituent monomers. In this study we investigated the effect of including total NSP and its major constituent monomers as independent variables in data sets for step-wise regression analysis in addition to more traditional measurements of fibre content on the accuracy of equations designed to predict the energy value of feedstuffs for pigs.

In vitro methods which can be used to predict the nutritive value of feedstuflfs for livestock are attractive in terms of both speed and economy. The in vitro pressure transducer technique (PTT) whereby the gas evolved during the in vitro fermentation of feedstuffs in rumen fluid is quantified by a pressure transducer, has been used to predict the nutritive value of ruminant feedstuffs. Here the potential for the PTT in predicting the digestible energy contents of eight feedstuffs varying in non-starch polysaccharide (NSP) content fed to growing pigs, was investigated.

Low protein diets have been proposed as a way to enhance fat reserves and reduce liveweight gain in breeding animals of very lean genotypes. The objective of this study was to examine the effect of different protein levels on daily gain, body composition and reproductive performance of gilts.

At 118 (sem=0.28) days old, 54 genetically lean gilts ((Landrace x Large White) x Large White) were allocated, considering firstly age and secondly weight, between three treatments with different dietary lysine:energy (g/MJ DE) ratios: High (0.9), Medium (0.6) and Low (0.3), fed twice daily at 2.9 x maintenance energy. Animals were weighed weekly and backfat thickness (P2) and muscle depth values were also taken. Eye muscle area measurements were taken by real time ultrasonography (Aloka 500) at the end of the experiment At 160 days of age, puberty was induced by administration of exogenous gonadotropin (PG600).

The body condition of the gilt at first mating may have a significant effect upon its lifetime reproductive performance. (Gueblez et al, 1985). Gaughan et al (1995), have recently demonstrated that gilts with low backfat thickness (9- 13mm) had fewer litters and weaned fewer piglets than gilts with medium (14-16mm) and high (>17mm) levels. The extent to which variations in both body weight and backfat thickness of gilts at first mating influence long-term reproductive efficiency has been further investigated in a commercial trial at the JSR Commercial Development Unit, Catwick. The overall objective of the trial was to assess the long-term performance of modern pig genotypes under commercial conditions.

In commercial systems it is highly desirable that gilts are synchronised into a predictable first heat. The use of PMSG/hCG injections (PG 600) has met with some success inducing a synchronised fertile oestrus and slightly increased ovulation rate (Schilling and Cerne, 1972) in gilts and anoestrus sows. Diets containing a high proportion of dietary fibre may influence litter size in gilts (Stewart et al, 1995). The aim of this study was to determine the effect of a high level of dietary fibre on oestrus expression and ovulation rate of gilts synchronised with exogenous gonadotrophins (PG600) or given daily boar stimulus.

Ad libitum feeding of a high fibre diet may be instrumental in reducing the development of abnormal behaviours in group housed sows (Brouns et al.1994). However, although there may be welfare benefits associated with feeding sows in this way, such a feeding practice is unlikely to be adopted unless it is commercially viable. This study compared the reproductive performance of gilts fed a high fibre diet ad libitum throughout gestation, with gilts fed a commercial diet on a restricted level.

Unsaturated fatty acids especially n-3 polyunsaturated fatty acids (PUFA) are recognised as important components of a healthy human diets and increased intake has been shown to reduce the incidence of cardiovascular diseases (BNF, 1992). These fatty acids are susceptible to oxidation and lipid oxidation in meat may adversely affect meat quality and safety. However, tissue α-tocopherol (AT) may reduce oxidative changes. In this study, the effect of increased dietary supply of AT and unsaturated fatty acids on tissue AT content, fatty acid profiles and oxidative stability of pig muscle lipid was assessed.

Food intake is one of the most important factors governing animal performance. Amongst the dietary variables that affect food intake, both deficiencies and excesses of protein and amino acids are known to be important. Moreover, excesses of certain amino acids may alter protein utilisation and consequently animal performance. Although large amino acid excesses have been shown in various experiments to alter food intake of weanling or growing pigs (Baker, 1993) the effects of the moderate amino acid excesses that may arise in normal diet formulation have been little studied. The objective of this experiment was to study if a 100% excess of single amino acids in a diet with an 'ideally' balanced amino acid pattern could alter daily food intake, average daily gain or food conversion ratio in growing pigs. The excesses used were relatively small to investigate the effect of excess within the range that might be found in practice.

The potential reduction in nitrogenous excretion by growing pigs, through the reduction of protein levels in diets, has not been consistently achieved without compromising performance. This may have been due to inadequate formulation of the diets. Formulation on the basis of the total amino acid content of feed ingredients may limit the nitrogen retention, and hence the rate of protein accretion (Lee et al., 1993). Therefore, the objective of the experiment reported here was to evaluate the nitrogen balance of pigs fed diets at two levels of protein, formulated on the basis of true ileal digestibility of the essential amino acids (Rhône-Poulenc Animal Nutrition, 1993) and the net energy available from the raw materials (Noblet et al., 1994).