The objectives of the trial were to Investigate the effects of long-term administration of bovine somatotropin (BST) from week 2 and 10 post-partumn on the yields of milk, milk components, body weight, body condition, health and reproductive status during the first lactation of dairy heifers.

19 Friesian dairy cows in their first lactation were allocated at calving to one of 3 treatments: Daily subcutaneous Injection of recomblnantly derived bovine somatotropin (25 mg/d) from either week 2 (BST2;n=6) or week 10 (BST10;n=6) of lactation, or injection of buffer solution from week 2 of lactation (C;n=7). Treatments continued until week 42 of lactation, or until 60 days prior to predicted calving date, if this occurred before week 42 of lactation. Initially cows were housed in cubicles and fed ad libitum individually through calan doors, on a diet of concentrate and grass silage (Table 1) on a 60:40 dry matter ratio. In approximately mid-lactation cows were turned out to grass but continued to receive concentrates according to milk yield and body condition. Milk yield was recorded daily and milk composition twice weekly as were live weight and body condition. Health and reproductive status were monitored over the lactation.

Avoparcin is a feed antibiotic which has been widely used as a growth promoter for broiler chickens, pigs and beef cattle throughout Europe. This paper presents results from a trial investigating the potential of Avoparcin as a performance enhancer when included in the diet of lactating dairy cows.

Research on the effect of supplementary light on the production of dairy cows (Tucker, 1985) has shown that it increases the milk production and feed intake of cows receiving less than 12 hours natural daylength, but it is not clear whether this arises from a behavioural stimulation to longer feeding times or a physiological response to light. In addition, although the reproduction of dairy cows has been reported to be seasonal with no effect of photoperiod on LH or FSH production (Rzepkowskl et al 1982), no studies have been made of the effects of supplementary light on oestrous activity and behaviour.

The introduction of milk quotas within the European Economic Community may not have been a popular choice in 1984 but with the benefit of hindsight, few dairy farmers in the UK would now advocate their removal.

Contrary to expectations, profitability on dairy farms since 1984 appears to have improved, admittedly from a very low base. Farmers have been compelled to re-consider their management practices and have concentrated on the priority of lowering production costs. Price factors have also worked in favour of margins and agricultural suppliers have been forced to compete for a reducing market through keen price competition. At the same time quotas have themselves become a substantial asset without any investment on behalf of the original owner.

There can be no guarantee that quotas will continue indefinitely as political policies can change at short notice. It Is, however, self evident that such a mechanism does work at least in terms of controlling milk supply. Most observers therefore take the view that quotas will remain a long term constraint within which dairy farmers must manage their businesses.

Dairying is the largest single sector of British agriculture. European milk production is however in surplus and the imposition of quotas has put pressure on the industry. It has also constrained the interaction of the industry with market forces and hence its potential for progressive development. The greater the pressure the more important is efficency and hence the greater the need for and the benefits from genetic improvement. This paper reviews breeding objectives for dairy cattle, and considers the opportunities for the uptake of new technologies such as multiple ovulation and embryo transfer, and physiological predictors of genetic merit.

Concentration on clear and limited breeding goals is crucial to the success of any breeding programme. This is probably the principal factor underlying the greater genetic progress achieved in North America and New Zealand than in Europe.

Gibson (1987) has estimated that the optimum ratio of fat:protein In milk for processing is currently about 1.65:1 (i.e. 5.6% fat would be required to match the current average protein production of about 3.4%). Even with a 30% fall In consumption of dairy fat, the optimum fat % in milk for manufacturing would still be 3.8—4.7%.

Pregnant sows tethered in stalls frequently show high levels of stereotypic behaviour such as bar biting and chain chewing. This indicates chronic stress, with long-term effects similar to metabolic diseases (Broom, 1983; Cronin, 1985; Dantzer, 1985). Food restriction is a major cause, but sows restricted in food intake are variable in frequency of sterotypies (Appleby and Lawrence, 1987). Another possible cause of stress is the behaviour of neighbouring sows (Barnett, Hemsworth and Winfield, 1987). Here, the effect of stereotypic behaviour of neighbours on the development and performance of stereotypies is examined.

There is increasing evidence that hunger and frustration of feeding motivation are potential sources of stress for pigs on restricted food levels such as tethered, pregnant sows. However, it is not clear what factor(s) of feeding regimes are critical in this respect. It has been suggested that the hunger of pigs on restricted food allowances may result in part from the use of concentrated foods lacking dietary bulk. This paper reports on 2 experiments conducted to examine the effect of straw as dietary bulk on hunger as measured by operant response rate.

On a single feed an animal can increase its intake of a nutrient (eg. protein), as its ratio to energy is reduced, only by increasing its rate of energy intake. When given, as a choice, two feeds of a different protein but equal energy contents, it can vary its protein intake independently of Its energy intake by varying the proportion of each feed in its diet.

The experiment described here was designed to investigate the effect of feed protein content on the feed intake of young pigs and to test the proposition that young pigs, when given a choice between two feeds of different protein contents, a combination of which is non-limting, will select a diet which meets their protein requirements. In addition an investigation of the rules which govern the diet selection was carried out.

Four feeds (L, A, B and H) with similar energy contents (16.5 MJ DE per kg fresh feed) but different levels of crude protein (CP) were formulated and made into pellets. All feeds were intended to be non-limiting in vitamins and minerals.

Information on the digestibilities of amino acids in soya-bean, sunflower, meat and low-glucosinolate rapeseed. meals, and effects of manufacturing methods, should be useful when interchanging these foodstuffs in pig diets. Also of interest is the extent the determined digestibility values provide adequate measures of amino acid availability for growth.

Best Linear Unbiased Prediction (BLUP) is now the method of choice for the estimation of breeding values in dairy and beef populations. The advantages of this mixed model methodology over traditional methods are well documented and include the simultaneous estimation of fixed effects and prediction of random effects and the utilization of records from all relatives to predict an individuals breeding value. In addition, account is taken of genetic trend and of reduction in genetic variance due to selection. In Canada, BLUP is now used for breeding value estimation of pigs but the structure of the Canadian pig industry is one of many herds practising selection with the herds linked by a widespread use of artificial insemination. The advantages of BLUP have not been investigated for the situation of the UK pig industry where most selection is performed within closed nucleus herds.

The objectives of this study were to use computer simulation to determine rates of response, accuracy of prediction and accummulation of inbreeding for pigs in closed nucleus herds when selection decisions were based on estimated breeding values (EBVs) derived from BLUP compared to more traditional methods of phenotypic selection and index selection.

For the past 20 years specialised sire and dam lines have generally exploited existing breed differences, and there has been little within-breed selection for litter size. However, some lines may now be approaching optimum fatness. At the same time, more accurate methods are evolving for estimating genetic merit for litter size. This study therefore re-examines the benefits of selection for litter size in specialised dam lines.

International field data suggest that up to one out of every four piglets dies before weaning. After accounting for stillbirths, crushing and piglets that die because they do not get enough to drink or are too weak to survive, most of the remainder die of scours. In the first week of life most scours are caused by Escherichia coli. Data have suggested that up to 50% of these scour deaths are caused by the K88 type E. coli, accounting directly for the deaths of about 150 thousand piglets per year in the U.K. and over 10 million worldwide.

Field observations have suggested that only some litters are affected while others remain healthy even though they are reared alongside litters with K88 scour. Similarly, it has been observed that the progeny from certain boars are more susceptible.

Despite its importance, relatively few measurements have been made of the metabolisable energy (ME) content of fresh herbage. Changes in the nutritive value of spring herbage are commonly described in terms of its digestible organic matter content (DOMD) either measured in vitro or predicted from a fibre fraction. ME is normally assumed to be directly proportional to DOMD.

Energetic studies of herbage such as those of Armstrong (1964) and Beever et al (1985) have been restricted to pure species and one location. The purpose of the present experiment was to examine changes in DOMD and energy values with increasing maturity in vivo using sheep in commercial swards over several years.

The objective of the trial was to examine the effects of partial storage-feeding (silage fed indoors overnight, grazed herbage during the day) on the herbage utilization, milk production, reproductive performance, and health of spring and autumn-calving dairy cows.

The implementation of milk quotas has caused the dairy industry to reappraise its production strategy. The producers previous goal of maximising milk output has been replaced by minimising the cost of producing each unit of output, as a means of maintaining profitability. Feed costs account for the greatest proportion of expenditure in any dairy farming system, it is important therefore that efficient resource use is made in this aspect of production. Herbage provides the lowest cost feed available, as such it is important that it makes as large a contribution as possible to the production requirements of the dairy cow. The grazed sward tends to be more efficiently utilised at low grass heights by the grazing animal. The corollary of this,is that the dairy cows intake potential may not be reached at these heights. Research indicates that a silage buffer feed would have the ability to prevent this short fall in intake but the importance of silage quality is not known. A grass/ clover mixture has the potential to offer a higher feed value whilst requiring a lower input of fertiliser nitrogen than a pure grass sward. Knowledge regarding the ideal sward height to help maintain the clover component is scarce.

The pattern in which animals consume their daily allocation of feed may affect both total daily intake and the efficiency with which the ingested nutrients are used. The experiment described here compared the patterns of intake of four forages offered to lactating cows either alone or with 9 kg concentrates/head/day.

The control of milk production costs has gained even greater importance when striving to improve profitability under a quota regime. Consequently there is a resurgence of interest in the use of competitively priced byproduct feedstuffs for dairy cows. However detailed information concerning the use of distillery byproducts under UK conditions is scarce. This experiment examines the effect of replacing a proprietary pelleted concentrate with malt distillers grains (draff).

In a changeover design experiment consisting of 4 three week periods, sixteen autumn calving British Friesian cows were offered four treatments, in which draff plus a mineral supplement replaced part of the concentrate allocation. The mineral supplement was formulated and fed to ensure that levels of calcium, phosphorus, magnesium, sodium and potassium supplied by the concentrate plus draff/mineral fraction of the diet were equal for all treatments. Cows were offered silage ad libitum with both concentrates and draff/mineral being offered separately in two feeds per day.

Many experiments have shown (see Armstrong and Ross, 1968) that the addition of fats to ruminant diets can lead to a reduction in the digestibility of forage cell walls due to adverse affects on the rumen microflora. Jenkins and Palmquist (1982) showed in vitro that the formation of insoluble calcium soaps in rumen fluid could prevent this problem. Additionally, Jenkins and Palmquist (1984) reported that the feeding of the preformed calcium soaps of tallow and soya oil fatty acids to dairy cows allowed normal rumen digestion of fibre whereas non-saponified tallow fatty acids caused a reduction in fibre digestion.

The main aims of the present experiment were to examine a new calcium soap of palm fatty acids for its effects on whole tract digestibility of various feed fractions and to measure its effective metabolisable energy (ME) content at maintenance, the present United Kingdom standard.

Fodder beet is a high yielding crop in terms of dry matter (DM) per hectare with yields of up to 12 t DM ha-1 from the roots and 2 to 5 t DM ha-1 from the tops. The root has a high metabolizable energy (ME) content and the average utilized metabolizable energy (UME) per hectare is 150% of average grass silage UME production (Heppel, 1985). The roots are highly digestible and can be used in dairy cow diets as a substitute for silage or concentrates. Most research work has shown an increase in total dry matter intake when fodder beet is included in a dairy cow ration (Roberts, 1987). The effect on animal performance, particularly milk fat content, is however more variable (Sabri, 1987). One reason for the differences may be the level of protein supplementatio in the fodder beet rations.

This experiment evaluated the interactions between the feeding of fodder beet and level of protein supplementation in the concentrate on feed intake and cow performance.

Previous experiments have shown important differences in milk production when mixed starch sources were replaced by mixed high quality by-products in high concentrate diets with hay as the forage (Sutton et al. 1987). The purpose of the present experiment was to compare rolled barley with sugar beet feed (SBF) in both molassed and unmolassed forms when given alone with grass silage in a high-concentrate diet. Additionally the effect of altering protein concentration of the concentrates was examined.