Where indirect calorimetry and slaughter techniques have been compared previously (eg: Geay, 1984; Beever et al, 1988) estimates of energy retention have tended to be greater from calorimetry than from slaughter studies. However, in most instances each technique was applied to a different group of animal and over only a limited range in energy retention. The aim of this work was to examine the difference between estimates of energy retention obtained using a direct technique (comparative slaughter) (ERs) and an indirect technique (open circuit respiration calorimetry) (ERc) applied to the same group of animals and over a relatively wide range of energy retentions.

The ingestion of tannins and other polyphenols by ruminants can adversely affect the growth and fibre-digesting activities of the rumen microorganisms (Muhammed et al. 1994). However, components of rumen liquor such as preformed monomers (amino acids, purines and pyrimidines) and other nutrients may protect the microorganisms, by providing nutritional conditions optimal for growth and energy metabolism. Rumen liquor also contains plant proteins, to which phenolic substances may bind preferentially. The influence of some polyphenols on the degradation of cellulose by the anaerobic fungus Neocallimastix frontalis strain RE1 has been studied in two nutrient media considered to embrace the range of nutritional conditions that may occur in the rumen at different times. The media used were medium M2 of Hobson (1969) which contains rumen fluid casein hydrolysate and yeast extract, and the medium of Hungate and Stack (1982) (medium HS) which is chemically defined and in particular lacks protein hydrolysate and rumen fluid. Whatman no. 1 filter paper cellulose (30 mg) was the growth substrate. Filter-sterilized solutions of tannic acid (dissolved in dist. H20) or ellagic acid, gallic acid or catechin (dissolved in dimethylsulphoxide, DMSO) were added to the media (10 ml) prior to inoculation with strain REl (approx. 104 zoospores) and incubation for 5 d at 38°C. Separate control incubations were performed with the 2 solvents (H20 and DMSO) used. The compounds tested were more inhibitory towards fungi grown in the defined medium (HS) than in the rumen fluid-containing medium M2 (Table 1). Thus tannic acid reduced cellulolysis to around 50 % of the relevant control values at a concentration of approx. 0.1 mM in HS, and 0.8 mM in M2. Corresponding values for ellagic acid were 0.15 mM and 0.5 mM, for gallic acid 0.25 mM and >3.6 mM and for catechin 0.15 mM and >2.4 mM respectively. It seems that these phenolic compounds are potent inhibitors of cellulolysis by Neocallimastix by mechanisms yet to be elucidated. It also appears that proteinaceous media reduce the inhibitory effects, suggesting that interactions occur between the proteins in the medium and the test compounds. It seems that in the rumen, dietary proteins and/or peptides may partly protect the fungi from the effects of polyphenolics as seen here in vitro.

It is well established that increasing the protein concentration of supplements increases milk yield in cows given grass silage-based diets. The responses are attributed to improved diet digestibility, increased silage dry matter (DM) intake and supply of amino acids from the small intestine. However, physical and chemical treatments of protein supplements used to decrease ruminal protein degradability have produced variable responses in animal production. Another alternative to increase amino acid supply is the processing of the grain supplements, which could affect both the energy availability and protein degradability in the rumen. Kassem et al. (1987) showed some improvements in milk production when barley was treated with a formaldehyde reagent. The aim of this study was to examine the effects of physical treatments to reduce ruminal protein degradability of barley and rapeseed meal (RSM) on milk production in cows fed grass silage ad libitum.

Brewery and distillery co-products such as Brewers Grains and Draff have long been recognised as effective forage replacers within cattle rations. Recently the value of these feeds as concentrate replacers has been demonstrated (Hyslop and Roberts 1990, Forbes and Johnson 1990) with 4kg of concentrates being typically replaced by 16kg of Brewers Grains or Draff within dairy cow rations.

Moist wheat distillers grains (Supergrains) contain higher levels of dry matter, energy and protein compared to Brewers Grains or Draff. At the single distillery producing the co-product, the main raw material used is wheat with a small quantity of malting barley to assist in the enzyme conversion of starch. The cereals and yeast used in the process pass through the entire fermentation and distillation process with the material left after the spirit has been distilled off being concentrated by centrifugation to form Supergrains with a dry matter (g/kg), metabolisable energy (MJ/kg DM) and crude protent content (g/kg DM) of 260, 14.0 and 320 respectively..The objective of this work was to evaluate the effect of replacing concentrates with Supergrains with bulls fed ad libitum grass silage.

The combination of milking combined with restricted suckling is a common production system (dual purpose) in many countries. In a previous study (Boden and Leaver, 1994, Animal production 58, 463-464 Abstr.), Holstein Friesian cows milked once daily, and restricted suckled produced 0.56 of the saleable milk of conventional twice daily milked cows. Restricted suckling substantially reduced milk fat and increased milk protein contents. In this study, a range of milking and suckling patterns were examined.

The objective of this work is to develop non-destructive techniques for assessing the mammary secretory mass of dairy cows. The nutritional responses of dairy cows depend on characteristics of both the feed and the cow and the latter has received insufficient attention. Experimental animals have generally been described in terms of their liveweight and condition score which gives only a rough indication of the masses of fat and protein. These studies are developing a description of dairy cows which has 3 major components whereby nutritional effects can carry forward within (a) body fat, (b) body protein or (c) mammary secretory mass. Milk yields are closely related to mammary secretory mass across a wide range of species although there is sufficient variation in mammary secretory efficiency (milk yield per unit mammary secretory mass) within a species to encourage selection for increased efficiency. Studies of this kind have been limited by the lack of a non-destructive technique for assessing udder volume; serial slaughter studies of mammary mass are particularly affected by large between-animal variation (e.g. Gibb et al, 1992). Recently, a technique utilising polyurethane foam to prepare casts from oxytocin-milked udders has been developed (Knight and Dewhurst, 1994; Dewhurst et al, 1993) and can be used for repeated measurements within-cow. The technique has been used to investigate changes in mammary secretory mass and efficiency in first-lactation Holstein-Friesians.

When the ratio between Metabolisable Protein (MP) and Metabolisable Energy (ME) is optimal for a given level of milk output (not constrained by genotype, management or other nutritional factors), further increases in milk output can be obtained by two strategies:

• Strategy 1. Increased supply of ME and MP (maintaining optimal MP:ME), or

• Strategy 2. Oversupply of MP (ie MP:ME > optimum)

Possible mechanisms underlying Strategy 2 include use of amino acids for gluconeogenesis or oxidation (Oldham, 1994), mobilisation of body energy reserves or, where forage is available ad libitum, increased forage intake (Newbold, 1994). For the purpose of this study, supply of MP above the theoretical optimum was assumed to increase milk protein yield only via the mechanism of increased forage intake.

The objective of this study was to evaluate the economic (cost of ration) and environmental (overall efficiency of N use) consequences of increasing milk yield by these two strategies.

Whole cottonseed and other cotton products contain gossypol {2,2’bi (formyl-1,6,7 trihydroxy-5-isopropyl-3-methyl napthalene)},a polyphenolic compound that is toxic to prefunctional ruminants and monogastric animals. Gossypol in excessive quantities may escape detoxification by the animal and produce toxicosis in functional ruminants. Recent reports have documented that gossypol inhibits rumen microbial growth and the degradation of grass hay by rumen microbes (Ismartoyo et al, 1993), growth and total protein content of animal cells (Ismartoyo et al, 1994a) and fermentation by rumen protozoa in culture (Ismartoyo et al, 1994b). The present study reported herein was designed to investigate the effect of gosssypol on the degradation of cellulose by pure cultures of the rumen fungus Neocalimastix frontalis strain REl.

The metabolisable protein (MP) system (AFRC, 1992), adopted as the official method of describing the protein requirements of ruminants in the UK, introduces the concepts of effective rumen degradable protein (ERDP), digestible undegradable protein (DUP) and fermentable metabolisable energy (FME). For effective protein rationing, the aim is to match the supply of FME and ERDP, and to supply further protein requirements as DUP. This should lead to a better balance of energy and protein to meet the requirements of the animal. Diets are likely to have lower total protein contents than those presently available, leading to reductions in diet costs and nitrogen (N) excretion. The MP system was constructed primarily on a theoretical basis and this experiment was an initial step in validating it for beef cattle.

In order to increase the animal production such as meat, milk and wool, it is vital to relate information on the nutritional characteristics of feed available with the requirements for nutrients according to the purpose and rate of productivity of the animals in question. In the industrialised countries, this information has been incorporated in tables of “Feeding Standards” which interpret chemical analyses of feed resources in terms of their capacity to supply the energy, protein, vitamins and minerals required for the particular productive purpose. However, in Iran,due to the lack of such tables, researchers have had no alternative but to use the mentioned “Feeding Standards” tables for their research work. This had led to little improvement in animal production in Iran since the tables mentioned have been made to meet the Industrialised countries conditions such as resources and environment. Additionally, in Iran where low-quality roughages are the main component of the ruminants diet, it is essential that feed evaluation systems are developed to take this into account. An example of this, although urea/ammonia treatment has been adopted in some areas, there is no up-to-dated methods to investigate by how much nutritive value is increased. Therefore, the nutritive value of some selected Iranian feedstuffs, barley grain (BG), alfalfa (AA), wheat straw (WS), ammoniated wheat straw (TWS) was assessed by chemical analysis, digestion and degradation studies.

The increase of milk yield potential of dairy cows raises a number of questions relating to their management at pasture where the intake potential might be limiting. The interaction of initial milk yield (IMY), sward availability (SH) and level of concentrate supplementation (CI) is largely unknown.

Two experiments of 42 and 24 days in spring and midsummer were carried out with 45 and 27 Holstein Friesian cows respectively. In spring, five IMY groups (range 16.9 to 35.5 kg/day) and in midsummer three IMY groups (range 22.2 to 31.8 kg/day) were used. In both periods, three compressed sward height(3 to 5, 5 to 7 and 7 to 9 cm) and three CI (0, 3 and 6 kg/day, with 160 g CP/kg DM, 12.8 MJ ME/kg DM) were used. The grazing area consisted of 7.9 ha of perennial ryegrass which was set stocked. The herbage intake (HDMI) was estimated indirectly from individual cow performance. Grazing time (GT) was recorded for each cow on 24 hour observations. Multiple regression analyses were carried out relating the dependent variables herbage intake, grazing behaviour and milk production to the independent variables (IMY, SH, CI).

Incidence maps show bovine hypocupraemia to be a widespread problem in the cattle-populated regions of the United Kingdom. Absolute copper defciency, molybdenum-, sulphur- and iron-induced hypocupraemia have been demonstrated on commercial farms and there are specific areas with a high incidence of hypocupraemia, particularly in parts of Cumbria, Derbyshire, Lincolnshire, Somerset, County Down and Londonderry.

Molybdenum- and sulphur-induced copper deficiency is probably mediated through thiomolybdates formed in the rumen, which then react with copper and particulate matter to form highly stable compounds that cannot be digested and absorbed. The consequential loss in physical and financial performance can be high. Hence, a protected source of copper, which by-passes the rumen, could offer an effective method of improving performance.

The purpose of this experiment was to compare the efficacy of copper sulphate sequestered to a polysaccharide coating (Carbosan Copper, Quali Tech Inc Chaska, Minnesota, USA) with conventional copper sulphate using finishing beef cattle on a grass silage-based diet.

The interest for increasing post-ruminal methionine supplies for dairy cows fed maize silage based rations has been clearly demonstrated (Sloan 1992). Theoretically grass silage based rations are also deficient in methionine in most dietary situations. Expressed as a percentage of PDIE (protein digestible in the small intestine when energy is limiting microbial protein synthesis in the rumen) the metDI value for grass silage approximates 1.95 compared to 1.97 for maize silage.

This trial was conducted, to verify, if in practice, methionine alone could limit milk protein secretion in dairy cows fed grass silage based rations.

Recognition of the potential of whole crop wheat (WCW) as an ‘environmentally friendly’ complement to grass silage has led to several studies on its nutritive value. Most of these quantified nutritive value using the in vivo digestibility technique. In spite of the number of studies on the subject, there is little information available on the relationship between the digestibility and metabolisable energy (ME) content of WCW. The complications of measuring methane production have also meant that where reported, ME values for WCW have been estimated rather than measured. Accurate ME measurements are integral for the inclusion of WCW when formulating livestock diets. This study examined the relationship between digestibility in vivo and ME content derived using measured methane contents of WCW harvested at different stages of maturity and conserved using contrasting methods. The study forms part of an on-going MAFF LINK project that aims to develop equations for the laboratory-based prediction of the nutritive value of WCW.

Belgian Blue bulls fattened at grass are not slaughtered directely out of pasture. They are always finished in a stanchion barn with concentrate diets, in order to provide a meat which corresponds to the market demand. So, no data are available on the influence of grass on meat and fat characteristics of bulls from the Belgian Blue breed. The objective of this experiment was to compare meat quality and fat composition of bulls which carried out a complete fattening period either on pasture or indoors.

The increase in rumen digestion of cereal straw by its treatment with anhydrous ammonia has been commonly explained by a chemical action on plant cell wall structure, increasing its solubility and potential degradability, and by an enhancement of microbial access to degradable cell wall. However, although some authors (Kolankaya et al., 1985; Balcells et al., 1993) have also reported an increase in rumen microbial synthesis and activity by treating straw with ammonia, Fondevila et al. (1993) did not observed a higher rumen degradation in sheep given ammonia-treated straw compared with untreated straw. This work was conducted to study straw cell wall degradation and the possible differences on rumen fermentation characteristics induced by ammoniation of dietary straw.

Interest in the production of maize silage in Ireland has increased in the last few years. The objective of this experiment was to evaluate the performance of steers when fed maize or grass silage based diets ad libitum and supplemented with varying levels of concentrates.

Sixty continental cross steers were blocked on the basis of live weight (av. initial weight = 617 kg) and breed (Charolais, Limousin and Simmental) and were allocated to one of the following six dietary treatments with 10 animals per treatment: A) maize silage-1 (sown under polythene) plus 2 kg concentrates (22% CP); B) 50:50 mixture of maize silage-2 (grown without the use of polythene):grass silage plus 4 kg concentrates (16% CP); C) maize silage-2 plus 4 kg concentrates (16% CP); D) maize silage-3 (as for silage-2 but with additive applied to control aerobic deterioration) plus 4 kg concentrates (16% CP); E) grass silage plus 4 kg concentrates (16% CP); F) grass silage plus 6 kg concentrates (14% CP). The steers were fed for 105 days during which live weight gains and group intakes were measured. After slaughter carcass gains were calculated (using an initial kill-out of 53%), kidney knob and channel fat weights were measured and carcass conformation and fat scores were taken.

An effective strategy for milk production is to supplement silage with small amounts of high-protein concentrate based on mixed carbohydrate sources and fish and soyabean meals (Aston et al 1992). Recent work at Trawsgoed by Sargeant and McAllan (1993) using growing steers given high-digestibility grass silage supplemented with rapeseed meal (a source of highly rumen degradable protein) produced similar live-weight gains to those obtained with fish meal. Jacobs and McAllan (1992) concluded that microbial protein yield is greater when the more degradable protein source is given, indicating a better balance in the supply of nitrogen and energy nutrients within the rumen. Lactating cows given grass silage diets have a high requirement for Metabolisable Protein (MP). The source of rumen fermentable carbohydrate may be important when MP supply is derived from degradable dietary protein and hence microbial growth. This study therefore examined the effects of varying the sources of carbohydrate and protein in low levels of concentrate given with high-digestibility grass silage. The main effects observed in the milk production experiment are presented here.

It is well established that the intake and digestibility of roughages by ruminants is positively correlated with rate of passage (ARC, 1980), presumably to enable as complete a microbial degradation of the poorer roughages as possible. On the other hand hind gut fermenters such as horses have been thought to have adopted the alternative strategy of using a high rate of passage to ‘cream’ off the rapidly degradable material of poor quality roughages so as to maintain adequate nutrient intakes. Surprisingly, there are remarkably few actual comparisons between ruminants and hindgut fermenters in the literature. Traditionally dried roughages (hay) and cereal and ‘by-product concentrates’ have been used as horse feeds (grains, brans sugar beet pulp). Recently there has been more interest in the use of silages with horses (eg Smoulders and Hobiers, 1988). However the information as to the utilisation of silages by horses is limited.

It is widely accepted that the fermentation characteristics of grass silages will affect the voluntary intake of animals offered silage. Relationships between voluntary silage intake and various parameters measurable in silage have beei demonstrated and they provide, with varying degrees of accuracy, methods of predicting voluntary silage intake. The objective of this study was to compare the voluntary intake and animal performance supported by two grass silages with similar ME contents but differing FME: ME ratios.