There is little published data on the detailed performance of continental genotypes as suckler cows in a hill environment. The work presented investigates levels of blood metabolites and hormones in autumn calving heifers during the post-partum period. Reproductive performance of the herd is detailed in an accompanying paper (Keatinge et al 1994).

Recent developments in cattle breeding technology have made the mass production of in vitro fertilised (IVF) embryos a realistic possibility. One use of this technology will be the production of “designer calves” for beef, from dairy and suckler cows. The IVF embryos used for this purpose are likely to have the genetic potential for high growth rates which may result in higher birth weights. If used incorrectly, this development in embryo transfer (ET) technology may increase the incidence of dystocia and therefore reduce the welfare of both cows and calves. A better understanding of the factors involved in dystocia would enable management action to be taken before ET and during pregnancy which would minimise dystocia and maximise welfare of both cow and calf.

The successful re-breeding of suckler and dairy cows is vital to the economics of farming cattle. The gestation length of cows is 280-290 days, so the optimum interval after calving for the subsequent mating is 75-85 days if a 365 day calving interval is to be achieved. Average calving rates to a given service are of the order of 0.5 to 0.6 (Diskin and Sreenan, 1980). Most practical management strategies allow cows to be mated during a 7-10 week period (giving 3 or 4 opportunities to show oestrus). The chance of conception improves with each oestrus cycle following calving, so the earlier a cow begins to show oestrus activity after calving the more likely she is to be successfully mated, because the early, less fertile oestrus cycles, are likely to happen before the planned mating period.

Current ration formulation schemes for calculating the feeding requirements of dairy cattle are primarily based upon empirical relationships between nutrient availability and milk production. Although these schemes can provide reasonable estimates of nutrient requirements, they are inadequate at predicting the responses in milk yield and composition to changes in nutrient availability. Clearly, a more integrated approach is required where the predictions are based on the metabolic fate of the absorbed nutrients. An ability to achieve this requires knowledge of the precursors used for milk protein synthesis and how nutrient intake influences their partition to the mammary gland for utilisation in milk protein biosynthesis.

During lactation the ruminant mammary gland removes relatively large quantities of circulating amino acids (AA) to meet the requirements for milk protein synthesis but arterio-venous uptake studies in dairy cows (1) have indicated that the uptake of certain AA may be insufficient to account for their output as milk protein. The apparent deficit may be accounted for by the use of AA supplied to the gland as small peptides or proteins. A dual-labelled tracer approach involving infusion of [13C]-labelled peptides into the external pudic artery which supplies blood directly to the mammary gland demonstrated that dipeptide-bound AA can be utilised as direct precursors for milk casein synthesis in lactating dairy goats (2). However, previous studies using vascular infusion of [13C]-labelled free AA (3) have provided equivocal data on involvement of non-labelled extra-mammary derived peptides/proteins in vivo in the biosynthesis of milk protein.

Amino acid requirements for energy metabolism and protein turnover within the gastrointestinal tract are substantial and may be met from luminal and arterial pools of amino acids. Several studies have demonstrated that the quantity of amino acids appearing in the portal blood does not balance apparent disappearance from the intestinal lumen and that changing diet or the availability of energy-yielding substrates to the gut tissues may influence the uptake of amino acids into the portal blood (Seal & Reynolds, 1993). For example, increased net absorption of amino acids was observed in animals receiving exogenous intraruminal propionate (Seal & Parker, 1991) and this was accompanied by changes in glucose utilisation by the gut tissues. In contrast, there was no apparent change in net uptake of [l-13C]-leucine into the portal vein of sheep receiving short term intraduodenal infusions of glucose (Piccioli Cappelli et al, 1993). This experiment was designed to further investigate the effects on amino acid absorption of changing glucose availability to the gut with short term (seven hours) or prolonged (three days) exposure to starch infused directly into the duodenum.

The feeding of molasses influences the rumen fermentation by changing the balance of microbes in the rumen and their metabolism. One of the consequences is a decrease in efficiency of utilisation of dietary protein when high molasses levels are fed. The dietary protein requirements of ruminants may therefore be higher for diets containing high molasses levels. A previous experiment with dairy cows has shown positive responses in feed intake and milk production to increases in both effective rumen degraded dietary protein (ERDP) and digestible undegraded protein (DUP) in diets containing 310 g/kg DM of molaferm 20 (a mixture of 800 g cane molasses with 200 g condensed molasses solubles per kg, supplied by United Molasses) (Yan and Roberts, 1993). The current experiment was undertaken to evaluate the effects of dietary ERDP and DUP levels on rumen fermentation, hay DM degradability and microbial growth in the rumen of wether sheep.

The production performance of cattle fed forage-based diets, particularly conserved forages, is poor and unpredictable. It has been shown that protein deposition is limiting in silage-fed cattle (Gill et al., 1987). It has also frequently been reported that the ratio of carcass fat:protein in silage-fed cattle is high (Baker, Young & Laws, 1992). There are few comparative dietary studies on whole-body fat metabolism in cattle. It was therefore the aim of this study to measure some of the parameters of whole-body fat metabolism in cattle fed forage-based diets and thus to determine if the high fat:protein ratio of silage-fed cattle is due to altered rates of whole-body fat metabolism. It was also our aim to determine whether the well-documented effects of β-agonists on fat metabolism are dependent on dietary status.

With the development of pig genotypes having high N deposition rates, previously accepted nutrient requirement recommendations must be re-examined. Requirements for protein (assuming lysine represents ‘ideal’ protein) for conventional growing pigs have been in the range of .60 to .74 g lysine/MJ DE (Batterham, 1994) while recent work with hybrid boars has shown a positive growth and N deposition response to ratios of the order of 1.0 (Rao and McCracken, 1991). It is generally accepted that sex has an effect on N deposition rate (Campbell et al., 1990) and therefore possibly on nutrient requirements. There is little information available on the effect of sex on growth and N deposition rate of modern genotypes. This experiment was conducted to estimate the N deposition rate of highly selected boars, gilts and castrates from 25 to 90 kg liveweight when fed diets containing ratios from 0.4 to 1.4 g lysine/MJ DE.

Reducing foregut digesta viscosity is the primary mode of action of feed enzymes in improving performance in broilers fed wheat and barley based diets (Bedford & Classen, 1991, Graham et al, 1992). In pigs, inclusion of appropriate fibre-degrading enzymes can improve the apparent digestion of nutrients in the small intestine (Graham et al, 1988). This has been attributed to both reduced digesta viscosity and an opening up of the feed cell walls enclosing the nutrients. However, the exact mechanism of this effect is unknown. This trial was designed to investigate the influence of enzyme supplementation on gut parameters in the pig.

A total of 40 crossbred pigs were weaned at about 9.5 kg and placed into 5 blocks of 8 individual metabolism cages based on litter origin, sex and liveweight. There were 2 treatment replicates per block. The mash diets were based on barley (751 kg/t), soyabean meal (150 kg/t), fish meal (40 kg/t) and soya oil (20 kg/t), with 1 kg/t chromic oxide as a marker. A hulled, low β-glucan (2.9 % of DM; Arra, Finland) and a naked, high β-glucan (5.3 % of DM; Condor, Canada) barley were used, and diets were fed without or with added /3-glucanase. Pigs were fed for 21 days, then sacrificed. Digesta was collected from the stomach, 4 equal lengths of the small intestine, the caecum and 2 equal sections of the colon plus rectum.

Growing pigs offered a choice of feeds differing in nutrient density (ideal protein and energy) may select a diet to meet individual requirements for optimum lean tissue growth rate. This has the potential for reducing the inefficiencies of nutrient under or over-supply associated with conventional single-diet feeding. The aim was to evaluate the scope for using the choice-feeding system in commercial growing and finishing pig production.

Seventy-two pigs were selected in 3 equal blocks at around 25 kg and housed in single-sex (gilts and boars) groups of six. They were offered least-cost formulated growing and finishing complete diets (Table 1) as a choice (C) from 25 to 95 kg or as in conventional single-diet (S) feeding in which a growing diet was fed from 25 to 50 kg and a finishing diet from 50 to 95 kg. Pigs were fed ad libitum and had unrestricted access to water. Pigs and residual feed were weighed weekly. Pigs were selected for slaughter in the week they approached 95 kg and measurements on chilled carcasses were made according to the method of Diestre and Kempster (1985).

The requirements of a weaned piglet are expected to change systematically over the period 6kg-25kg. Commonly during this time animals will be offered two diets. However, initially on each diet the animal may be restricted because it's protein requirements are in excess of that supplied by the diet. Then latterly, amino acids may be oversupplied requiring deamination of the excess by the pig. This is a costly process, in terms of the energy required by the pig and commercially, in terms of food protein costs. This system also does not take into account differing individual requirements within a group of pigs due to genotype, sex, maturity and stage of growth. As a result potential benefits are to be obtained if weaned piglets can be shown to choose an adequate diet, meeting their individual requirements, when given a choice of feeds.

When a highly digestible food is progressively diluted with one of greater ‘bulk’ the prevailing view is that the rate of food intake will initially increase at such a rate such that DE intake remains constant and, that beyond a critical point, intake of food and DE will fall as the dilution proceeds further. The critical point has been assumed to reflect the capacity of the pig for ‘bulk’. Current models which attempt to predict the voluntary food intake (VFI) of pigs use either food dry matter (DM) as a measure of bulk (eg Whittemore, 1983) or the undigested organic matter (eg Roan, 1991), or ignore the problem (ARC, 1981). It has long been known however, that such views are likely to be inadequate across the complete range of foods (eg the significant reduction in VFI of pigs on foods based on sugar beet pulp, compared to that on other more undigestible materials).

The experiment described here was designed (i) to try to identify the property of ‘bulky’ foods which might be responsible for limiting their VFI and (ii) to see the extent to which the capacity for a ‘bulky’ food might be modified by prior experience.

The inclusion of supplementary fat in the dairy cow diet is an effective and cheap method of increasing its metabolisable energy (ME) density. However, an increase in the fat content of the diet frequently causes a decrease in the protein concentration of milk, which, when the market requires an increase in the protein:fat ratio of milk, is not a desireable effect. This experiment was designed to compare die effect of dietary fat on die yield and concentrations of milk proteins in comparison to a carbohydrate ME source.

Twelve multiparous mid-lactation Holstein-Friesian cows were used in a 3x3 Latin square changeover experiment with 3 four-week periods. Cows were allocated to squares on the basis of their mean milk yield over the 7 days prior to the experiment. Within squares, treatments were randomly allocated to each cow. The first 21 days of each experimental period were used for adjustment, and the last 7 for sample collection.

Several studies have shown increased silage dry-matter intake (SDMI) and improved milk fat concentrations in dairy cows offered restricted fermented grass silages compared to more extensively fermented silages. A recent study suggested that differences in silage intake per se rather than an alteration in rumen fermentation may be responsible for the changes in milk composition observed in the previous studies (Doherty and Mayne, 1993). The aim of the present study was to examine the effect of changes in concentrate composition on milk production parameters in dairy cows offered grass silages of contrasting fermentation type.

Two direct cut grass silages were prepared using either an inoculant, containing a single strain of Lactobacillus plantarum, (Ecosyl, 3 1/t fresh weight, Zeneca Products Ltd) or a mixture of aliphatic carboxylic acids (Maxgrass, 6 1/t fresh weight, BP Chemicals Ltd). Two concentrates (high starch or high fibre) were formulated containing either: barley, 300; wheat, 355; and soyabean-meal, 270 g/kg (high starch) or unmolassed sugar-beet pulp, 555; citrus pulp, 100; and soyabean-meal, 270 g/kg (high fibre).

Unprotected tallow is used as a feed ingredient to meet the energy requirement of high milking dairy cows, but its hydrolysed free fatty acids in the rumen can inhibit microbial activity and dietary fibre digestion. However, the negative effects of the tallow could be minimized when high levels of molasses are also fed since feeding molasses could shorten the retention time of the hydrolysed free fatty acids in the rumen. In addition, molasses contains a large proportion of non-structural carbohydrates (sugars) which have fast fermentation rates in the rumen. When a diet is formulated to have a low fermentable metabolisable energy (FME) concentration, supplementing with a high molasses level may partially make up the deficiency of the energy requirement of the microorganisms in the rumen of dairy cows. Previous experiments have showed that molasses could be fed to dairy cows up to 312 g/kg DM without adverse effect (Yan and Roberts, 1992) and a crude protein level at 160 g/kg DM in the diet containing 310 g/kg DM of molasses was satisfactory for feed intake and milk production of dairy cows (Yan and Roberts, 1993). The current experiment was subsequently undertaken to investigate the response of dairy cows given high levels of molasses to dietary levels of FME produced by altering unprotected tallow concentrations in diets.

Methionine has been shown to be the first-limiting amino acid for milk protein synthesis in lactating dairy cows fed maize silage-based diets complemented with soyabean meal (Sloan et al., 1992) (Pisulewski et al., 1993). Thus, the aim of this trial was to investigate the hypothesis that methionine was first-limiting or if not at least colimiting with lysine for milk protein synthesis in dairy cows fed grass silage complemented with soyabean meal.

8 muciparous and 4 primiparous dairy cows six weeks into lactation were randomly allocated to three 4x4 Latin squares (cows and heifers separately), each period containing 2 weeks. The four treatments consisted of Tl = Control ; T2 = 3.7 g methionine ; T3 = 7.4 g methionine ; T4 = 7.4 g methionine and 22.2 lysine . All figures relate to estimated intestinally available amino acids, g/day (Smartamine™ technology Rhône-Poulenc Animal Nutrition). The basal ration was a second cut grass silage offered ad libitum plus 0.57 kg of hay plus an average 10.9 kg concentrate.

In two previous studies at this Institute, premixing of the silage and concentrate elements of the diet prior to feeding (complete diet feeding) produced either no increase in intake and milk production (Agnew and Mayne, 1992) or a slight increase in intake with no response in milk production (Agnew and Mayne, 1990). However the maximum proportions of concentrate dry matter intake (DMI) in the diets used in these experiments were 0.54 and 0.51 respectively. With the present rapid increases in cow genetic merit, across the industry, coupled with possible changes in the relative costs of feed grains and ensiled grass, there is a need to explore the response to complete diet feeding with animals of high genetic merit receiving higher proportions of concentrates. The current study therefore examined the response to complete diet feeding and its interaction with genetic merit of the cow, when using high concentrate diets.

Lameness is the second commonest cause of culling in breeding sows after reproductive failure and can occur as a result of physical injury, infection or inherent leg weakness. Lameness incidence may be affected by both genetic and environmental factors, and is especially prevalent in confined systems such as stalls and tethers, which restrict the amount of exercise that the sows can perform. Confinement, with a corresponding lack of exercise, has been shown to affect bone strength in poultry but this weakness has not been documented in other species housed in confinement. The objectives of this experiment were to compare bone strength and muscle conformation in sows housed in two different dry sow systems.

A total of 18 non-pregnant Large White X Landrace sows of similar age, parity and genetic stock, were studied in two different dry sows systems: 1) permanent stalls (n=8) and 2) a large group with Electronic Sow Feeder system (n=10). All sows were weighed and following slaughter by pentabarbitone injection, the left thoracic and pelvic limbs were dissected and five forelimb and nine hindlimb locomotory muscles were removed and weighed. The muscles were chosen partly on the basis of perceived importance for locomotion and partly on the basis of ease of identification and removal. A proportional muscle weight was then calculated by dividing individual muscle weight (in grams) by total body weight (in kilograms). This removed any differences in muscle weight due purely to differences in total body weight between systems. The left humerus and femur were also removed, and were broken by a three-point bend test using an Instron Universal Tester.

Most UK pig farmers will be turning to housing sows in groups due to the regulations which will phase out stall and tether systems by 1st January 1999. The formation of either small stable groups or large, dynamic groups by mixing unfamiliar sows, will result in aggression between sows. One consequence of aggression is the level of damage to the skin which, if severe, may compromise the welfare of the sow. Information is needed on the effect of different methods of mixing and managing sows in groups on the level of skin damage and, hence, the welfare of the sow. In addition, aggression between sows in early pregnancy may have deleterious effects on reproductive performance. In particular, Simmins (1993) showed that sows housed in stable groups throughout the implantation period of pregnancy had larger, heavier litters than sows housed in dynamic groups. However, no information was available on the level of aggression between sows on each treatment. The object of the present experiment was to determine the level of skin damage, as an indicator of aggression between sows, that occurs when sows are mixed in small stable groups, before or after mating, or large dynamic groups after mating.