State of the art milk production encourages an intensive system of maximising peak milk yield and minimising calving interval, epitomized by the 40 kg peak daily production and 10,000 kg 305 d lactation yield of a well bred, well fed Holstein. Given good management, milk yield typically declines at approximately 2% per week. It requires only a simple calculation to show, therefore, that this same cow would still be yielding around 20 kg of milk daily at 2 months before calving. The dilemma for the farmer is whether to dry her off or not, and if he is sensible he will probably do so. However, if he is really clever he will then change his rebreeding policy!

The MOET open herd operated by Genus is an open-nucleus breeding programme, designed to identify superior families and individual females. The herd of 250 cows was established over the period 1987-1990, with embryos from high genetic merit dams in North America. Subsequently, replacement heifers have been bred both from donors selected within the nucleus herd, and from external donors. The herd is milked three times a day, and fed a high-quality complete diet, to maximise production and so facilitate selection. Average NMR 305 day production figures for 440 heifers were 8995 kg, at 3.88% and 3.41% protein. A relatively high proportion of the herd is kept open for embryo production, with 40% of these heifers milking beyond 400 days and 13% for over 500 days. Data from the MOET project are currently being used to model production up to and beyond 305 days, and to establish correlations between performance in early and extended lactations and between lactation length and subsequent performance. These results will be discussed in the context of options for calving interval available to high production-high genetic potential Holstein Friesian herds.

In dairy cows, effect of pregnancy on milk production is acknowledged but little documented, and with conflicting data. Weak during the « normal » lactation, this effect becomes important in late pregnancy. To precisely model milk secretion, and to adjust novel management of the lactation cycle, it is important to specify this effect.

Previous studies (Moorby et al, 1994) have shown that supplementing grass silage with undegradable protein (UDP) during the dry period can lead to increased yields of milk protein and lactose. These studies have often involved restriction of forage intake through limitation of access time and the feeding of straw. This experiment was conducted to assess the effect of UDP supplementation with ad libitum access to grass silage as well as the effects of restricting forage intakes by including straw in the diets of dry cows.

The genetic merit of the UK dairy herd is increasing rapidly and this trend is likely to continue for the forseeable future. With cows of higher milk yield potential and higher nutrient requirements, feeding systems developed in the past with medium genetic merit animals, may now need to be adapted to meet the needs of high genetic merit animals if nutrition x genotype interactions exist. This would be particularly true to increasing proportion of concentrates in grass silage based diets. This study was undertaken to compare the milk yield responses of high and medium merit dairy cows.

Provision of a balanced supply of fermentable metabolisable energy (FME) and effective rumen degradable protein to rumen microbes enables maximum utilisation of energy and protein in dairy cow diets. Cane molasses containing a high proportion of water soluble carbohydrates can be very effective source of FME in dairy cow diets. The objective of this experiment was to evaluate the effect of the inclusion of molasses and fishmeal in the concentrate component of the diet, on the performance of lactating dairy cows.

Protected fats are very useful for increasing the energy concentration of diets fed to high-yielding dairy cows without adverse effects on rumen fermentation. However, in previous studies, it has been found that although high-fat diets usually increase yields of milk and milk constituents, they can lead to a depression in milk protein content. This can be partially overcome by increasing the supply of fermentable carbohydrates, using lactose, thereby increasing microbial protein yield (Garnsworthy, 1996), or by increasing undegradable protein supply (Garnsworthy, unpublished). The objective of this experiment was to study the response of cows in mid lactation to a product containing protected fat and protein (MegaPro, Volac International) fed with or without lactose.

In recent years the use of complete diets has increased markedly in the UK. Although figures are difficult to obtain, it is estimated that approximately 20% of the National Herd is now fed complete diets. This represents 400,000 cows and the number is steadily increasing . Complete diets are often associated with rations where the forage component contains a significant proportion of maize silage, and where sodium hydroxide treated wheat (Soda Grain) is often included. Although it is widely believed, within the farming community, that the inclusion of Soda Grain (SG) results in a marked increase in milk protein content, there is limited scientific evidence to support this view . At the same time there has been a concomitant decrease in the inclusion of molassed sugar beet feed (MSBF) as this by-product is associated with increased milk fat content. Recent feeding studies at the Centre for Dairy Research have also established that the use of distillery by-products will reduce milk fat content. The aim of the current study was to determine the effect on forage intake, milk yield and composition of lactating dairy cows fed a complete diet based on grass and maize silage, when SG was replaced by either MSBF and cracked wheat (CW), or MSBF and distillery by-products, which were used to replace a conventional protein supplement of soya bean and rape seed meal.

The diet selection of weaned piglets may vary according to the social environment in which they are housed. Many choice feeding experiments have been performed with pigs housed individually, in order to monitor their food intake and preferences effectively (e.g. Kyriazakis and Emmans, 1990; Kyriazakis, Emmans and Whittemore, 1991). However commercial animals are usually housed in groups and their feeding behaviour may differ from that of individual animals as a result of social interactions (Haer and Merks, 1992). This could have associated effects on the diet selection of pigs. The intention of this experiment was to observe the behaviour and production information of pigs offered a choice of foods, that differed only in their crude protein (CP) levels, and compare this with pigs offered a single food. Pigs were housed individually, in groups of two or eight.

Performance testing several genotypes on one diet may impose nutritional constraints on the genetic merit for growth of particular genotypes. Use of the diet choice procedure may remove nutritional constraints on growth, if pigs can “choose” the appropriate combination of the diets to attain the growth determined by the animal's genotype. In a genetic improvement framework, the diet choice procedure could be used to identify animals of high genetic merit for a given selection objective.

There were 120 Large White pigs from the high, low and control lines, which had been selected for lean growth rate for seven generations in the Edinburgh lean growth selection experiment. In each selection line, there were 10 full-sib groups of four pigs. Pigs were performance tested from 30 to 85 kg, with individual penning and ad-libitum feeding. Within each full-sib group, one pig was allocated to each of the high (HP : 220 g crude protein (CP)/kg) or low (LP : 120 g CP/kg) protein diets.

Pigs exhibit a range of abnormal behaviours (e.g. stereotypies or tail-biting) which may, at least in part, be linked to feeding regimes which produce high levels of feeding motivation. Therefore, a welfare dilemma exists because the quantitative food restriction of sows and boars remains an essential husbandry practice to reduce excessive weight-gain and maintain breeding efficiency. However, it has recently been proposed that underlying levels of feeding motivation may be reduced through the ingestion of foods of high bulk (e.g. Brouns et al .,1994). These foods may serve to reduce feeding motivation through gastro-intestinal distension rather than by increased nutrient supply. Therefore, the aim of this experiment was to investigate whether iso-energetic foods with different bulk characteristics (water-holding-capacity - WHC) affect the level of feeding motivation, and if so, the duration of their effect.

Dominance hierarchies are commonly observed in groups of pigs (Beilharz & Cox 1967). These hierarchies appear to be established by individuals assessing each other's relative abilities, usually through fighting (Rushen & Pajor 1987). The resulting aggression is a well documented problem in pig husbandry. It could be reduced by mixing pigs who differ in certain respects, such that they rapidly form a hierarchy without vigorous fighting. Hessing et al. (1994) found that mixing pigs who showed high levels of resistance to being placed on their backs in a “back test” with pigs who were less resistant resulted in low levels of aggression. In this study we investigated whether mixing pigs which differ in their aggressiveness could reduce the negative effects of regrouping.

Growing pigs are observed to spend a considerable amount of time chewing substrates in their environment (e.g. Jensen et al., 1993). This behaviour has been exposed to scientific investigation on many occasions because of its link to the serious welfare problem of tail-biting (see Fraser, 1987). However, there is still no motivational explanation which adequately describes the causation of chewing because it is unclear if the behaviour reflects feeding motivation, exploratory motivation, or a combination of both (Day et al., 1995). Therefore, this aim of this paper was to test the hypothesis that the initial exploratory chewing of a novel substrate may identify nutritional properties which could, if appropriate, reinforce feeding motivation and subsequent foraging behaviour.

Enzymes have been successfully used to improve the nutritional value of cereal based feeds for pigs and poultry since the early eighties. Their benefits derive from improved digestion of nutrients following the destruction of anti-nutritional compounds such as β-glucans and arabinoxylans and the augmentation of the animal's existing enzyme arsenal where this may be sub-optimal. In the ruminant sphere fibrolytic enzymes have been used as aids to silage preservation for almost as long. Their action here is to enhance natural sugar levels by the breakdown of structural carbohydrates - an action which can concurrently render the fibre more amenable to digestion by rumen microbes.

Crops are presently exploited for the economic production of materials like carbohydrates, lipids and proteins for e.g. food, feed, or processing industries. The designed modification of plants by genetic engineering has opened up the possibility to broaden this range of products. The number of novel compounds successfully produced in plants using this “molecular farming” approach is steadily increasing, and includes carbohydrates, fatty acids, biodegradable plastics, high-value pharmaceutical (poly)peptides and industrial enzymes.

The technical feasibility of producing active industrial enzymes in plants at a relatively high level has been demonstrated. The use of seeds as the formulation and delivery vehicle for the enzymes greatly enhances the economic competitiveness of plants as a source of industrial enzymes. This novel concept exploits the fact that many plants and plant organs are or can be a component in industrial processes, animal feed and human food.

Responses in sow traits at farrowing and during lactation and in pre-weaning piglet growth rate were determined in a population of Large White pigs, after seven generations of divergent selection for components of efficient lean growth rate. Information on the factors influencing preweaning piglet growth rate is required for a comprehensive evaluation of alternative selection strategies.

There were four selection groups: daily food intake (DFI), lean food conversion (LFC), lean growth rate (LGA) on ad-libitum feeding and lean growth rate on scale feeding (LGS). There were 242 gilts in the study, with 20 gilts in the high, low and control lines of each selection group. Pigs in the ad-libitum selection groups were performance tested over a fixed weight range of 30 to 85 kg. Pigs fed on scale feeding were performance tested for a fixed time period of 84 days from 30 kg with food intake equal to 0.75 g/g of daily ad-libitum food intake. Matings were unsupervised and took place in outside paddocks.

A significant relationship between the oestrogen receptor gene (ESR) and litter size has been detected in USA populations of Large White and a synthetic comprising 50% Meishan (Rothschild et al., 1995). Animals carrying two copies of the favourable allele (B) had an extra pig born per litter than those that did not have the allele. This paper reports on results observed in a UK 50% Meishan synthetic and four UK Large White lines.

Litter size data from 50% Meishan synthetic (L93) full-sib females where more than one ESR genotype was segregating. Data were analysed using a mixed model with full relationships and including the fixed effects of season of farrowing, parity, ESR genotype (AA, AB or BB) and service type (AI or natural service). Heritiability and permanent environmental effects for litter size were assumed as 0.09 and 0.11, repectively. A total of 27 full-sib families were represented and included 62 sows and 139 litter records. Hypothesis testing used the option in PEST under a mixed model (Groeneveld et al., 1991).

Meishan synthetic sows and gilts have been shown to produce higher litter weights at weaning than White breed type sows and gilts (Sinclair et al. 1995). The explanation for increased litter weight weaned could be attributed to one of three areas: (1) The M sows are inherently better mothers than W and can support a higher level of piglet production. (2) The higher piglet production could be solely a result of hybrid vigour in the cross-bred piglets. (3) The increased litter production could be primarily attributed to a higher number of piglets born and reared by M. This experiment aimed to evaluate the maternal post-natal effects by standardising litters between breeds by cross-fostering techniques.

Sixty-four 3rd parity sows were used in a 2x2x2 factorial experiment to assess the influence of maternal breed type (Meishan synthetic 50% [M] or pure-bred European Landrace and Large White [W]), litter size (8 [L] or 12 [H] piglets) and breed of piglet (25% Meishan hybrid [m] or white hybrid [w]) on sow and litter production over a 28 day lactation. All litters were formed by cross-fostering 24hrs after farrowing.

Previous research into the genetics of broiler traits in a commercial breeding operation found a significant maternal effect on juvenile body weight, at 32 days of age, in addition to the additive genetic effect (Morris and Pollott, 1995). Since no nurture or imitative behaviour occurs between the dam and offspring in modem broiler production, any maternal effects are likely to be conferred to the offspring via the egg. This study attempts to investigate the nature of these effects.

Pedigreed eggs from two separate broiler breeding lines, one experimental male line and one experimental female line, were individually weighed prior to incubation. In total 2871 eggs were weighed, 1887 eggs from the experimental female line and 984 eggs from experimental male line.

Baker et al. (1994) and Park et al. (1996) have demonstrated the potential of near infrared reflectance spectroscopy (NIRS) for the prediction of organic matter digestibility (OMD) of grass silages. Equally, Steen et al. (1995) and Park et al. (1996) have shown a similar potential in the use of NIRS to predict intake potential. However these workers have all used NIRS with dried silage samples, a practice which increases analytical costs and results in differential losses of volatile components. The present study was designed to explore the potential of NIRS with undried silage for the prediction of OMD and intake potential.

One hundred and thirty six grass silages, produced commercially on farms across Northern Ireland, were selected and their ad libitum intake and OMD determined through cattle and sheep respectively (Steen et al., 1995).