Pea-wheat bi-crop silages were reported to have moderate nutritive value when the proportion of peas in the sward was less than 200 g/kg (Adesogan et al., 1999). These authors also suggested that improvements in the digestibility, intake and nitrogen (N) balance of the forages may result from increasing the proportion of peas in the sward. This experiment was designed to examine this theory by determining the in vivo apparent digestibility, N retention and voluntary feed intake (VFI) in sheep of pea-wheat bi-crop silages containing different ratios of peas to wheat and harvested at two stages of growth.

The basis of diet selection for protein by ruminants has been questioned by Tolkamp et al. (1998). They suggested that diet selection by ruminants is based on the ruminally degradable protein (RDP) of foods whereas the metabolizable protein (MP) yield has no effect when the foods offered as a choice contain adequate RDP. However, it is necessary for an animal to have some knowledge of the nutritional properties of the available foods in order to select appropriately between them, as the prevailing view is that its feeding behaviour depends largely on learning (Arsenos and Kyriazakis, 1999). The objective of this study was threefold: (i) to test whether sheep are able to form specific associations between food flavours and post-ingestive consequences (PIC) induced by the administration of a ruminally undegradable, but readily digestible protein source (DUP); (ii) to investigate the relative importance of RDP and DUP sources and their consequent PIC in the development of such associations; and (iii) to test whether such associations can be formed when DUP is administered concurrently with a RDP source. Following Tolkamp et al.'s (1998) suggestion we have hypothesised that learned associations would be dictated by the PIC attributed to RDP rather than DUP administration.

Improving the efficiency of lean meat production is of major importance to the UK sheep industry. Compared to a range of other breeds, Texel-sired lambs have been found to contain a higher proportion of carcass lean content. Carson et al. (1999) found that Texel X Greyface (Border Leicester X Scottish Blackface) lambs contained 38 g/kg more lean than Rouge de l'Ouest (Rouge) X Greyface lambs. The aims of the present experiment were (a) to investigate the efficiency of liveweight and carcass gains in Greyface, Rouge and Texel lambs at equal dry matter intakes of a standard diet (b) to test the hypothesis that carcass chemical composition would be similar in Greyface, Texel and Rouge lambs when finished on the same level of feeding.

Mineral deficiencies for livestock are reported from almost all world regions. Deficiency can be caused by inadequate intake or by the presence of antagonists in the diet. Traditionally, inorganic salts, such as oxides and sulphates have been added to the diet to meet the requirements of the animal. More recently, there has been increasing interest in mineral chelates. Studies by Rojas et al. (1995) and Ward et al. (1996) have reported that the copper and zinc availability in copper and zinc chelates is greater than in the traditional inorganic salts. Other studies by Kegley et al. (1994) and Schell et al. (1996) reported contradictory results. In this study, two separate trials were carried out to compare the effects of Bioplex copper and Bioplex zinc with the effects of copper and zinc sulphate on plasma copper and zinc levels in adult Texel sheep.

Alpha-tocopherol is the natural antioxidant in milk preventing the oxidation of milk fat and development of off-flavour and off-odour. The feeding of dairy cows can significantly affect plasma and milk concentrations of α-tocopherol. There is growing interest in the use of legumes in milk production and so it is important to investigate their effects on milk a-tocopherol as well as the oxidation of milk fat during storage and, hence, shelf-life of milk.

Tabulated sodium requirements of dairy cows, such as those of the Agricultural Research Council (ARC, 1980), are all based on milk yield. The principle for this is the apparent homeostatic control of sodium concentration in the milk of cattle, with sodium loss in milk being approximately proportional to milk yield. However, there is evidence that low yielding cows respond more than high-yielding cows to a sodium supplement when grazing lucerne with a low sodium content (Joyce and Brunswick, 1975), and the present study therefore investigated the effect of dairy cow milk yield potential on the response to the application of a fertilizer containing sodium.

Many references (review, Hemingway, 2000) indicate that giving supplementary dietary selenium (Se) and vitamin E during the dry period in amounts greater than accepted nutritional requirements can decrease the incidence, duration and severity of high somatic cell counts (SCC) and mastitis in dairy cows. Low dietary Se intakes and plasma Se concentrations are more frequent than those for vitamin E. As one example, Erskine et al. (1987) investigated two groups each of 16 herds each having either > 700 x 103 SCC /ml (High) or < 150 x 103 SCC /ml (Low). Mean contrasting plasma concentrations (μg /ml) were respectively 0.074 and 0.138 (P < 0.01) for Se with 4.2 and 4.8 (NS, adequate) for vitamin E. Supplementary dietary Se and vitamin E were given more frequently to the Low SCC herds. The present experiment investigated the effect of two multi-trace element/vitamin boluses (‘All-Trace’, Agrimin Ltd. DN20 0SP) which, inter alia, release 2 mg Se and 9 i.u. vitamin E /day giving a significant increase in glutathione peroxidase activity over an 8-month period (Allan et al., 1993).

Clinical copper deficiency is the second most common mineral deficiency in the world, the main cause being high dietary levels of molybdenum, sulphur and iron. Phillippo et al, (1987) reported that clinical signs of deficiency resulted from high dietary Mo and S. However, Fe and S resulted in hypocupraemia but did not induce clinical signs of deficiency. Therefore is was concluded that clinical copper deficiency was due to a direct effect of dietary Mo and S on copper metabolism in ruminants. Mackenzie et al. (1997) reported that plasma copper levels were not an accurate indicator of copper status and unlikely to predict animals requiring copper supplementation. Caeruloplasmin is large copper enzyme and accounts for 88% of plasma copper and Mackenzie et al. (1997) proposed that a caeruloplasmin to plasma copper ratio may provide a more accurate biochemical indicator of copper status. This trial was designed to investigate the effect of dietary Mo, S and Fe on the copper status of the lambs.

Grass forms the basal forage for the majority of ruminant livestock in Ireland and the UK. Level of nitrogen (N) and harvest date are the two major factors affecting the yield of herbage. In a concurrent study, Keady et al. (1999) concluded that herbage dry matter (DM) yield of the primary growth of a perennial ryegrass sward is increased by 7.9 kg DM/ha/kg N and by 152 kg DM/ha/day delay in harvest respectively. However as herbage yield increases, particularly as a result of delayed harvest, digestibility declines. The present study was undertaken to evaluate the effects of rate of N fertilisation application and harvest date on the degradation characteristics of grass.

Grass silage forms the basal forage for the majority of beef and dairy cattle during the winter indoor feeding period. Previous studies undertaken at this Institute have clearly indicated that the major factors affecting the feed value of grass silage are the date of harvest, rate of fertiliser nitrogen (N) application and additive treatment. The present study was undertaken to evaluate the effects of rate of N fertiliser application, harvest date and additive treatment on in-sacco degradation characteristics of grass silage.

Whole oil seeds represent an alternative to many commercial rumen-protected fat sources as energy supplements in rations for lactating dairy cows. Rumen protection reduces the potential for negative effects of unsaturated fatty acids on fibre digestion, but the structure of many whole oil seeds are thought to reduce the reactivity of their fat in the rumen. Cotton seed is often imported for inclusion in UK dairy rations, but rape seed represents a home grown oil seed which has potential as an economical fat and protein source in UK dairy rations. However, the seed must be crushed or chemically treated to be digested effectively and crushing may liberate oil to the extent that rumen digestion is altered. In a 20 week lactation study, supplemental fat from rumen-protected fat, cotton seed and rape seed fed at 25 g/kg dry matter (DM) in a grass-silage based total mixed ration (TMR) increased milk yield to a similar extent. However, DM intake was reduced by cotton seed and milk protein was reduced by rumen-protected fat (Reynolds et al., 1998). These responses may reflect alterations in digestive function, thus the objective of the present study, conducted simultaneously to the lactation study, was to evaluate the effects of the same diets on rumen, postrumen and total digestion in lactating dairy cows.

Maize distillers grains (MDG) are a traceable and valuable energy and protein feed for dairy cows (Owen and Larson, 1991) but little is known about the ability of UK MDG to replace more conventional protein sources, particularly their effects on the supply of protein to the cow. The purpose of the present experiment was to examine the effects of replacing soyabean meal with MDG on digestion in the rumen and flow of protein to the duodenum of lactating dairy cows.

The current UK Recommended Lists For Cereals (Anon., 1997), include grain quality information on each variety outlining its potential value to the miller, baker or maltster. These grain quality measures are used as a basis for premiums paid to producers. However, no such standards exist for feed grains with the exception that contracts often indicate a minimum specific weight. This is in spite of the fact that feed grains account for 41% of wheat and 50% of barley sales from UK produced cereals. Usage may be increased if its nutritive value was better defined to include information such as the proportion of the starch that is rumen degradable and the rate of degradation of this starch in the rumen. It is vital to know the quantity of starch available to the rumen since it is a major source of energy for microbial protein synthesis (see Reynolds et al., 1997). This study aimed to use the in vitro automated gas production (GP) technique to estimate rate and extent of starch degradation from a large population of wheat grains obtained from wide ranging agronomic conditions and relate this to chemical and quality parameters.

The UK is bound by the UN Framework Convention on climate change to reduce methane emissions to below 1990 levels by the year 2000. The Kyoto protocol requires a further cut of 12.5% by 2010. Ruminants are estimated to produce 74 Tg of methane per year (Benchar et al. 1998) which represents about 15% of total emissions (Crutzen et al., 1986). Therefore any reduction in the release of methane gas by enteric fermentation from the dairy herd is environmentally important. The objective of this study was to use data obtained from calorimetry trials to generate multiple regression equations predicting the levels and variability of methane emissions from dairy cows.

The UK metabolisable energy (ME) system for dairy cattle and net energy (NE) systems presently used in Europe and America were developed over 30 years ago. Recent studies have however indicated that these systems could under-predict the ME (MEm) or NE (NEm) requirement for maintenance for current dairy cows (e.g., Yan et al., 1997). The objective of the present study was to validate these systems using calorimetric data produced with lactating dairy cows and published around the world since 1976.

Feeding lambs diets formulated to be synchronous in terms of hourly energy and protein supply to the rumen has been reported to improve the efficiency of energy utilisation (Richardson et al. 1999). In a previous study Sinclair et al. (1995) reported that the efficiency of microbial protein production was improved when animals were fed a synchronous diet. The objectives of the present study were to investigate whether the changes in metabolism reported by Richardson et al. (1999) may be related to rumen microbial protein production and diet digestibility.

Recent data indicate that rumen fluid contains a relatively high concentration of peptide nitrogen and that it is influenced by the source of protein in the diet (Mesgaran & Parker, 1995). In addition, it has been demonstrated that ruminant gastrointestinal tract may have the potential for absorbing intact peptides, and that the hydrolysis rate of the peptides is influenced by peptide structure in the blood (Mesgaran, 1996; Mesgaran & Parker, 1996). The objective of the present experiment was to investigate the effect of altering the sources of protein in diets with similar effective rumen degradable protein (ERDP), on blood free and peptide-bound amino acid-N (FAA-N and PBAA-N) concentrations in Iranian Baloochi lambs.

A major constraint on smallholder dairy farms in Kenya is inadequate feed supply resulting in low productivity. In Kiambu district of the Central Highlands, principal feed resources are cultivated Napier grass, roadside grass and fodder from maize, including stover and higher quality thinnings cut during the growing period. An average farmer in Kiambu owns 0.8 ha of which 0.19 and 0.17 ha are dedicated to Napier and maize cultivation, respectively, and 2.2 cows producing 5.8 kg milk/day (Staal et al. 1998). Meeting the feed requirements of the dairy animals, while maintaining food production is already a challenge. There are indications that the maize crop will become increasingly important as a source of fodder (Staal et al. 1998). Methu (1998) showed that by planting 4 rather 2 maize seeds per hole, 1.9 t DM/ha of thinnings, with high energy and N content could be harvested without affecting significantly the yields of stover or grain. The present study explored further the potential of increasing production of good quality thinnings without jeopardising grain yield in a series of on-farm trials.

Fat is often fed to sheep and cattle as a means to increase dietary energy concentration. There is increasing interest in the supplementation of ruminant diets with fats and oils. However feeding fat may reduce dry matter digestibility, and feeding ruminant animals large quantities of fat (>5% of total dry matter intake) can result in a marked negative effect on fibre and dry mater intake. The aim of the present study was to investigate the effect of fat supplementation on ruminal degradation of dry matter (DM) and neutral detergent fiber (NDF) of sheep fed a tropical hay.

Grass hay is the traditional conserved fodder fed to horses in the UK, yet good quality hay is often scarce and expensive. Working or breeding equines often require a higher plane of nutrition than that provided by hay, yet feeding high levels of concentrates can lead to a number of metabolic disorders such as colic and laminitis. Furthermore, the high dust content of hay can elicit the onset of the debilitating disorder, chronic obstructive pulmonary disease. Thus, there is increasing interest in feeding horses forage-based diets which are both low in dust and have enhanced nutritive values. The aim of this experiment was to determine the intakes and digestibility of four types of conserved forage by ponies.