Efficient detection of estrus is a permanent challenge for successful reproductive performance in dairy cattle. In this context, comprehensive knowledge of estrus-related behaviors is fundamental to achieve optimal estrus detection rates. This review was designed to identify the characteristics of behavioral estrus as a necessary basis for developing strategies and technologies to improve the reproductive management on dairy farms. The focus is on secondary symptoms of estrus (mounting, activity, aggressive and agonistic behaviors) which seem more indicative than standing behavior. The consequences of management, housing conditions and cow- and environmental-related factors impacting expression and detection of estrus as well as their relative importance are described in order to increase efficiency and accuracy of estrus detection. As traditional estrus detection via visual observation is time-consuming and ineffective, there has been a considerable advancement of detection aids during the last 10 years. By now, a number of fully automated technologies including pressure sensing systems, activity meters, video cameras, recordings of vocalization as well as measurements of body temperature and milk progesterone concentration are available. These systems differ in many aspects regarding sustainability and efficiency as keys to their adoption for farm use. As being most practical for estrus detection a high priority – according to the current research – is given to the detection based on sensor-supported activity monitoring, especially accelerometer systems. Due to differences in individual intensity and duration of estrus multivariate analysis can support herd managers in determining the onset of estrus. Actually, there is increasing interest in investigating the potential of combining data of activity monitoring and information of several other methods, which may lead to the best results concerning sensitivity and specificity of detection. Future improvements will likely require more multivariate detection by data and systems already existing on farms.

1. The normal pattern of social behaviour in growing Large White and Berkshire pigs is described. The pigs were observed from 8 to 16 weeks of age in pens of 6 to 10 pigs. Large Whites were more aggressive than Berkshires.

2. Social rank was found to be positively correlated with initial weight.

3. Initial weight and social rank both influenced growth; the relative effect of rank compared with that of initial weight was greater in the second month than in the first.

4. The contribution of social rank to the total variance in growth over the 2-month period was estimated at about 13%.

5. It is suggested that the use of individual housing in pig progeny test schemes may not be desirable because of the absence of social environmental effects.

Ten hays harvested at three stages (early bloom MB, mid bloom MB or in seed) made from lucerne (Medicago sativaj, sweet clover (Melilotus segetalis), Persian clover (Trifolium resupinatum) and pre-bloom (PB) Italian ryegrass (Lolium multiflorum var.), were offered ad libitum to four Merino male sheep and daily intake (g dry matter (DM) per kg M0·75) and DM apparent digestibility (DMD) were measured. In sacco DM degradation (g per 100 g DM), gas production (ml per 200 mg DM), in vitro digestibility and fibre composition (g/kg DM) of the hays were also studied. Gas production or DM degradation were calculated at 6, 12, 24, 48, 72 or 96 h and their kinetics were described using the equation p = a + b(1 - e-ct). Intake and in vivo DMD of the hays were variable (P < 0·01). Lucerne EB and Persian clover (all stages) had the highest nutritive value, whereas sweet clover (all stages) had the lowest. Apart from neutral-detergent fibre, which was only related to intake (r = -0·68; P < 0·05), chemical components and in vitro digestibility were poorly (P > 0·05) related to animal performance. Between 12 and 96 h incubation, intake and in vivo DMD were better related to DM degradation (r = 0·79 to 0·83; r = 0·61 to 0·77) than to gas production (r = 0·73 to 0·80; r = 0·58 to 0·78). Prediction of intake and in vivo DMD from the (a + b) values did not provide a great advantage over using some of the static values of gas production or DM degradation.

Multiple regression using separated kinetics of degradation resulted in highest accuracy for predicting intake and apparent digestibility from gas production (R2 = 0·63; R2 = 0·78) and nylon bag degradability (R2 = 0·77; R2 = 0·89). It was concluded that the gas test has good potentiality as it was capable of predicting not only apparent digestibility, but also intake to a level close to that of the nylon bag technique.

The impact of internal and external parasitism on productivity of farm animals is considered for cattle, sheep, pigs and poultry. The parasitic challenge experienced and the outcome of that challenge is a dynamic one in which environment, management practices, including housing or grazing management, nutritional status, the host's ability to develop effective immunity and the speed with which this can occur, play a significant role. Much of our assessment of the impact of infection comes from pathophysiological and nutritional studies with contrived infestations. A common feature of all infestations is reduced efficiency of food utilization through reduction in food intake, though in some cases increases in nutrient requirement are induced as a result of damage to or loss of host tissue. Assessment of the impact on productivity in the field is technically very difficult and must take account of fluctuating challenge, determined by environmental and management decisions, and the manager's objectives for the performance of a particular category of livestock. This review attempts to integrate the assessment of losses in productivity based on pathophysiological studies with those based on protection of groups of livestock in production systems by regular pesticide use. Throughout the review the limitations inherent in both approaches and in our knowledge of how parasites impair productivity of the host are emphasised.

Foods derived from animals are an important source of nutrients in the diet but there is considerable uncertainty about whether or not these foods contribute to increased risk of various chronic diseases. For milk in particular there appears to be an enormous mismatch between both the advice given on milk/dairy foods items by various authorities and public perceptions of harm from the consumption of milk and dairy products, and the evidence from long-term prospective cohort studies. Such studies provide convincing evidence that increased consumption of milk can lead to reductions in the risk of vascular disease and possibly some cancers and of an overall survival advantage from the consumption of milk, although the relative effect of milk products is unclear. Accordingly, simply reducing milk consumption in order to reduce saturated fatty acid (SFA) intake is not likely to produce benefits overall though the production of dairy products with reduced SFA contents is likely to be helpful. For red meat there is no evidence of increased risk of vascular diseases though processed meat appears to increase the risk substantially. There is still conflicting and inconsistent evidence on the relationship between consumption of red meat and the development of colorectal cancer, but this topic should not be ignored. Likewise, the role of poultry meat and its products as sources of dietary fat and fatty acids is not fully clear. There is concern about the likely increase in the prevalence of dementia but there are few data on the possible benefits or risks from milk and meat consumption. The future role of animal nutrition in creating foods closer to the optimum composition for long-term human health will be increasingly important. Overall, the case for increased milk consumption seems convincing, although the case for high-fat dairy products and red meat is not. Processed meat products do seem to have negative effects on long-term health and although more research is required, these effects do need to be put into the context of other risk factors to long-term health such as obesity, smoking and alcohol consumption.

Lameness in dairy herds is traditionally detected by visual inspection, which is time-consuming and subjective. Compared with healthy cows, lame cows often spend longer time lying down, walk less and change behaviour around feeding time. Accelerometers measuring cow leg activity may assist farmers in detecting lame cows. On four commercial farms, accelerometer data were derived from hind leg-mounted accelerometers on 348 Holstein cows, 53 of them during two lactations. The cows were milked twice daily and had no access to pasture. During a lactation, locomotion score (LS) was assessed on average 2.4 times (s.d. 1.3). Based on daily lying duration, standing duration, walking duration, total number of steps, step frequency, motion index (MI, i.e. total acceleration) for lying, standing and walking, eight accelerometer means and their corresponding coefficient of variation (CV) were calculated for each week immediately before an LS. A principal component analysis was performed to evaluate the relationship between the variables. The effects of LS and farm on the principal components (PC) and on the variables were analysed in a mixed model. The first four PC accounted for 27%, 18%, 12% and 10% of the total variation, respectively. PC1 corresponded to Activity variability due to heavy loading by five CV variables related to standing and walking. PC2 corresponded to Activity level due to heavy loading by MI walking, MI standing and walking duration. PC3 corresponded to Recumbency due to heavy loading by four variables related to lying. PC4 corresponded mainly to Stepping due to heavy loading by step frequency. Activity variability at LS4 was significantly higher than at the lower LS levels. Activity level was significantly higher at LS1 than at LS2, which was significantly higher than at LS4. Recumbency was unaffected by LS. Stepping at LS1 and LS2 was significantly higher than at LS3 and LS4. Activity level was significantly lower on farm 3 compared with farms 1 and 2. Stepping was significantly lower on farms 1 and 3 compared with farms 2 and 4. MI standing indicated increased restlessness while standing when cows increased from LS3 to LS4. Lying duration was only increased in lame cows. In conclusion, Activity level differed already between LS1 and LS2, thus detecting early signs of lameness, particularly through contributions from walking duration and MI walking. Lameness detection models including walking duration, MI walking and MI standing seem worthy of further investigation.

Mixed crop–livestock systems, combining livestock and cash crops at farm level, are considered to be suitable for sustainable intensification of agriculture. Ensuring the survival of mixed crop–livestock systems is a challenge for European agriculture: the number of European mixed crop–livestock farms has been decreasing since 1970. Analysis of farming system dynamics may elucidate past changes and the forces driving this decline. The objectives of this study were (i) to identify the diversity of paths that allowed the survival of mixed crop–livestock farming and (ii) to elucidate the driving forces behind such survival. We analysed the variety of farm trajectories from 1950 to 2005. We studied the entire farm population of a case study site, located in the ‘Coteaux de Gascogne’ region. In this less favoured area of south-western France, farmers have limited specialisation. Currently, half of the farms use mixed crop–livestock systems. The data set of 20 variables for 50 farms on the basis of six 10-year time steps was collected through retrospective surveys. We used a two-step analysis including (i) a visual assessment of the whole population of individual farm trajectories and (ii) a computer-based typology of farm trajectories on the basis of a series of multivariate analyses followed by automatic clustering. The European Common Agricultural Policy, market globalisation and decreasing workforce availability were identified as drivers of change that favoured the specialisation process. Nevertheless, farmers’ choices and values have opposed against these driving forces, ensuring the survival of some mixed crop–livestock farming systems. The trajectories were clustered into five types, four of which were compatible with mixed crop–livestock systems. The first type was the maximisation of autonomy by combining crops and livestock. The second type was diversification of production to exploit economies of scope and protect the farm against market fluctuations. The other two types involved enlargement and progressive adaptation of the farm to the familial workforce. The survival of mixed crop–livestock systems in these two types is largely dependent on workforce availability. Only one type of trajectory, on the basis of enlargement and economies of scale, did not lead to mixed crop–livestock systems. In view of the current evolution of the driving forces, maximising autonomy and diversification appear to be suitable paths to deal with current challenges and maintain mixed crop–livestock systems in Europe.

There is growing societal pressure, expressed through government legislation and consumers’ purchasing choices, to abolish livestock systems considered detrimental to farm animal welfare. Such systems include farrowing crates, which are behaviourally and physically restrictive for sows. Therefore, identifying less restrictive farrowing systems for commercial implementation has become an important focus of pig research. Despite numerous attempts to develop indoor alternatives to crates, there is as yet no universal acceptance of such systems at the commercial level. The primary concern is piglet survival, because often favourable figures are reported at the experimental level, but not replicated in commercial evaluation. Alternative farrowing systems should equal or surpass survival levels in conventional systems and perform consistently across a range of farm circumstances for widespread commercial implementation. In addition, it is important that alternatives consider ease of management, operator safety and economic sustainability. Utilising a large database of literature, 12 existing alternative indoor systems were identified and compared against each other, conventional crates and outdoor systems. An assessment of how well alternative systems satisfy the design criteria for meeting animals’ biological needs was carried out by developing a welfare design index (WDI). The physical and financial performance of these systems was also evaluated and summarised. The derived WDI yielded values of 0.95 for conventional crates, with higher scores for commercial outdoor systems of 1.10 and indoor group farrowing or multi-suckling systems (e.g. Thorstensson = 2.20). However, the high total piglet mortality (23.7% ± s.e. 2.26) in indoor group systems compared with conventional crates (18.3% ± s.e. 0.63) and outdoor systems (17.0% ± s.e. 2.05), together with the added capital cost (92% more than conventional crates, 249% more than commercial outdoor huts), mainly as a result of extra building space provided per animal, question their feasibility to deliver from an economic perspective. Designed pen systems offered the best compromise, scoring 1.64 from the WDI, with a total piglet mortality of 16.6% (±s.e. 0.88) and capital costs and labour input more comparable to farrowing crates (17.5% more than crates). The critical review of different systems was hampered by the lack of comprehensive data and detailed system descriptions. When attempting to assess welfare and economic attributes of systems, there are certain caveats that require discussion, in particular weighting of the contribution of different design attributes to pig welfare, the relative importance of the sow and her piglets and the many potential confounding factors that arise. Also, when judging any system, it must be emphasised that the maternal characteristics of sows and the quality of stockpersonship will be integral to its success.

Polyphenols are chemically and biologically active compounds. Grape seed extracts (GSEs) have been widely used as a human food supplement for health promotion and disease prevention. However, there is little information regarding its application in animal feeds. An experiment was conducted to investigate the effect of inclusion of GSE at 0.025, 0.25, 2.5 and 5.0 g/kg in a wheat soya bean control diet on growth performance, protein and amino acid (AA) digestibility and plasma lipid and mineral concentrations in broiler chickens at 21 days of age. Performance was not affected by dietary treatment except in the case of birds fed the diet with the highest GSE concentration, which showed a worsening of weight gain and feed conversion. Apparent ileal digestibility (AID) of protein was significantly reduced in the birds fed the highest concentration of GSE, which also had a reduction on the AID of arginine, histidine, phenylalanine, cystine, glutamic acid and proline compared with those fed control diet. The inclusion of graded concentration of GSE in the chicken diets caused a significant linear decrease in the concentrations of plasma copper, iron and zinc. Plasma cholesterol, triglycerides and lipoproteins (high-density lipoprotein, low-density lipoprotein and very-low-density lipoprotein) concentrations were not affected by dietary GSE. In conclusion, this study demonstrated that incorporation of GSE in chicken diets up to 2.5 g/kg had no adverse effect on growth performance or protein and AA digestibility. Feed conversion was reduced and growth rate was retarded, when chickens were fed 5 g/kg of GSE. This study also indicated that grape polyphenols reduce the free plasma minerals.

Three strains of Holstein-Friesian (HF) cows: high production North American (HP), high durability North American (HD) and New Zealand (NZ) were assigned, within strain, to one of three pasture-based feeding systems: Moorepark (MP), high concentrate (HC), and high stocking rate (HS). The effects of strain of HF, feeding system and parity on milk production, body condition score (BCS), live weight, energy balance and reproductive performance were studied using a repeated measures model with a factorial arrangement of strain ofHF and feeding systems. Associations between these variables and conception to first service (CONCEPT1), conception to first and second service (CONCEPTl_2), pregnancy rate at 6 weeks (PREG6) and overall pregnancy rate (PREG) were assessed using logistic regressions. When treatment means were compared, the NZ strain had a shorter gestation length and a higher CONCEPT1J2 than both the HP and HD strains. Similarly, the NZ strain had a higher PREG6 and PREG than the HP strain. Feeding system had no significant effect on reproductive performance. The HP strain had the highest milk yield at first AI and peak milk yield, the NZ strain had the lowest milk yield while the HD strain was intermediate. The energy balance of the NZ strain was higher than that of the HP and HD strains. The NZ strain had the lowest live weight and highest BCS; the HD strain had the highest live weight and the HP strain had the lowest BCS. The results show that dairy cows with superior genetic merit for fertility traits have better reproductive performance.

A series of 4 × 4 Latin-square digestibility trials was carried out to determine whether there were any differences between different types of equid in their ability to digest diets containing different levels of fibre and protein. The equids (Thoroughbreds, Highland ponies, Shetland ponies and donkeys) were offered one of four molassed diets in turn and these contained different proportions of alfalfa and oat straw: 1·0:0, 0·67:0·33, 0·33:0·67, 0:1, respectively. The apparent digestibility of dry matter (DM), organic matter (OM), gross energy (GE), crude protein (CP), acid-detergent fibre (ADF) and neutral-detergent fibre (NDF) were estimated. The rate of passage of the different diets was measured using Cr-mordanted fibre (Cr-fibre) and Co-ethylene diamine tetra acetic acid.

All animals digested the components of the high-fibre diets less well than those of the low-fibre diets (P < 0·001 for DM, OM, GE, CP and ADF). Donkeys digested fibre more effectively than the other equids (F < 0·01 for ADF and NDF). The gastro-intestinal transit time of the high fibre diets was significantly less than that for the low fibre diets (P < 0·001) and donkeys retained food residues longer than the other equids (P < 0·01).

This review aims to present the different effects produced by a post-weaning intake limitation strategy on the growing rabbit, now largely used by French professional rabbit breeders. Although a quantitative feed restriction leads to slower growth, feed conversion (FC) is improved, particularly when the rabbits are again fed freely, as compensatory growth occurs. This better FC or the healthy rabbit is because of better digestion resulting from slower passage through the intestine, whereas the digestive physiology is slightly modified (morphometry of the intestinal mucosa, fermentation pattern, microbiota). Meat quality and carcass characteristics are not greatly affected by feed restriction, except for a lower dressing-out percentage. One of the main advantages of limiting post-weaning intake of the rabbit is to reduce the mortality and morbidity rate due to digestive disorders (particularly epizootic rabbit enteropathy syndrome). The consequences for animal welfare are debatable, as feed restriction probably leads to hunger, but it reduces the incidence of digestive troubles after weaning. However, the growing rabbit adapts very well to an intake limitation strategy, without any aggressive behaviour for congener. In conclusion, restriction strategies could improve profitability of rabbit breeding, but they should be adapted to any specific breeding situation, according to the national market, feed prices, etc.

One important objective for animal welfare is to maintain animals free from pain, injury or disease. Therefore, detecting and evaluating the intensity of animal pain is crucial. As animals cannot directly communicate their feelings, it is necessary to identify sensitive and specific indicators that can be easily used. The aim of the present paper is to review relevant indicators to assess pain in several farm species. The term pain is used for mammals, birds and fish, even though the abilities of the various species to experience the emotional component of pain may be different. Numerous behavioural changes are associated with pain and many of them could be used on farms to assess the degree of pain being experienced by an animal. Pain, as a stressor, is associated with variations in the hypothalamic–pituitary–adrenal axis as well as in the sympathetic and immune systems that can be used to identify the presence of pain rapidly after it started. However, most of these measures need sophisticated equipment for their assessment. Therefore, they are mainly adapted to experimental situations. Injuries and other lesional indicators give information on the sources of pain and are convenient to use in all types of situations. Histopathological analyses can identify sources of pain in experimental studies. When pronounced and/or long lasting, the pain-induced behavioural and physiological changes can decrease production performance. Some indicators are very specific and sensitive to pain, whereas others are more generally related to stressful situations. The latter can be used to indicate that animals are suffering from something, which may be pain. Overall, this literature review shows that several indicators exist to assess pain in mammals, a few in birds and very few in fish. Even if in some cases, a single indicator, usually a behavioural indicator, may be sufficient to detect pain, combining various types of indicators increases sensitivity and specificity of pain assessment. Research is needed to build and validate new indicators and to develop systems of pain assessment adapted to each type of situation and each species.

Weather patterns in northern European regions have changed noticeably over the past several decades, featuring warmer, wetter weather with more extreme events. The climate is projected to continue on this trajectory for the foreseeable future, even under the most modest warming scenarios. Such changes will have a significant impact on livestock farming, both directly through effects on the animals themselves, and indirectly through changing exposure to pests and pathogens. Adaptation options aimed at taking advantage of new opportunities and/or minimising the risks of negative impacts will, in themselves, have implications for animal health and welfare. In this review, we consider the potential consequences of future intensification of animal production, challenges associated with indoor and outdoor rearing of animals and aspects of animal transportation as key examples. We investigate the direct and indirect effects of climate change on the epidemiology of important livestock pathogens, with a particular focus on parasitic infections, and the likely animal health consequences associated with selected adaptation options. Finally, we attempt to identify key gaps in our knowledge and suggest future research priorities.

Crossbreeding, considering either terminal or rotational crossing, synthetic breed creation or breed replacement, is often promoted as an efficient strategy to increase farmers’ income through the improvement of productivity of local livestock in developing countries. Sustainability of crossbreeding is however frequently challenged by constraints such as poor adaptation to the local environment or lack of logistic support. In this review, we investigate factors that may influence the long-term success or the failure of crossbreeding programs, based on the scientific literature and country reports submitted for The Second Report on the State of the World’s Animal Genetic Resources for Food and Agriculture. Crossbreeding activities vary widely across species and countries. Its sustainability is dependent on different prerequisites such as continual access to adequate breeding stock (especially after the end of externally funded crossbreeding projects), the opportunity of improved livestock to express their genetic potential (e.g. through providing proper inputs) and integration within a reliable market chain. As formal crossbreeding programs are often associated with adoption of other technologies, they can be a catalyst for innovation and development for smallholders. Given the increasing global demand for animal products, as well as the potential environmental consequences of climate change, there is a need for practical research to improve the implementation of long-term crossbreeding programs in developing countries.

In the livestock industry, subcutaneous and visceral fat pads are considered as wastes, while intramuscular fat or marbling fat is essential for improving flavor and palatability of meat. Thus, strategies for optimizing fat deposition are needed. Intramuscular adipocytes provide sites for lipid deposition and marbling formation. In the present article, we addressed the origin and markers of intramuscular adipocyte progenitors – fibro-adipogenic progenitors (FAPs), as well as the latest progresses in mechanisms regulating the proliferation and differentiation of intramuscular FAPs. Finally, by targeting intramuscular FAPs, possible nutritional manipulations to improve marbling fat deposition are discussed. Despite recent progresses, the properties and regulation of intramuscular FAPs in livestock remain poorly understood and deserve further investigation.

Digestibility studies were carried out to establish the inter-relationship between crude fibre and total lipid digestibility in the presence of added calcium or non-ionic detergents. Three levels of calcium, corresponding to daily intakes of 2·3, 4·8 and 22·9 g per sheep, were used in a predominantly ground barley diet (65 to 73%) to which was added 8% beef tallow or maize oil. Two non-ionic detergents were used at 0·1% of the diet: nonyl phenol ethylene oxide and fatty alcohol combined with 3 molecules of ethylene oxide.

With a daily intake of 2·3 or 4·8 g calcium per sheep, supplementation with fat resulted in a reduced fibre digestibility. When the intake was increased to 22·9 g, there was a significant improvement (P<0·05) only for the maize-oil-supplemented diet. Increasing calcium intake, associated with increased calcium digestibility, significantly (P<0·05) depressed total lipid digestibility. Intake of 4·8 g calcium per day was associated with the highest calcium digestibility of 33% digestibility units and the total lipid digestibility of 94%. Maize oil was better digested than beef tallow with the lower level of calcium; the position was reversed with the higher level of calcium supplementation. No advantages were found for crude fibre and total lipid digestibility when detergents were added.

A possible mechanism by which the physical wetting of dietary lipids causes decreased digestibility of the fibre component is discussed.

Divergent breeding lines of Romney sheep, selected as lambs for consistently high or low faecal worm egg count (FEC) following natural multi-species challenge by nematode parasites, were established in New Zealand at Wallaceville Animal Research Centre in 1979 and at Rotomahana Station in 1985. In 1988 the Rotomahana lines, including an unselected control line maintained under the same management conditions, were transferred to Tokanui Station where they remained for 4 years. In 1993 elite high and low FEC animals from Tokanui, along with the controls, were transferred to Wallaceville, where merged lines have since been managed together. Selection responses from the lines at Rotomahana and Tokanui, and from a further 5 years of divergent selection in the merged lines, are reported here. For the two most recent lamb crops (1996 and 1997 birth years), log-transformed FECs of the high and low lines were 1·27 and -1·46 phenotypic standard deviation units from the control. After back-transformation to the original scale, where the FEC for control line lambs averaged 1255 eggs per g, the means for the high and low lines were 3Ό5 and 0·27 times the control mean. Animal-model restricted maximum likelihood estimates of her it ability and repeatability for single-record FEC (following separate infections) were 0·28 (s.e. 0·02) and 0·42 (s.e. 0Ό1), respectively. Correlated responses in production traits include significantly decreased post-weaning weight gain and increased dags (breech soiling) in lambs, and decreased fleece weight in yearlings and ewes in the low FEC line, compared with those in the high line. However the low FEC line had proportionally 0·11 more lambs weaned per ewe mated than the high FEC line (F < 0·01). It is concluded firstly that selection for high or low FEC in Romney s has achieved an 11-fold difference between the divergent lines. Secondly, it will generally be necessary in a commercial environment to apply index selection for a combination of increased productivity, decreased FEC and possibly decreased dags, when potential candidates are recorded under conditions of nematode challenge.

A 3-week feeding trial using 300 1-day-old male broiler chicks was conducted to evaluate the effects of adding three levels of a microbial phytase (Finnfeed phytase; 250, 500 and 1000 U per kg diet) to a maize-soya-bean-meal diet containing 3·0 g/kg non-phytate phosphorus and 8·0 g/kg calcium. A diet containing 4·0 g/kg non-phytate phosphorus and 9·0 g/kg calcium served as the positive control. The responses were evaluated in terms of broiler performance, toe ash contents, ileal phytate degradation, ileal digestibility of nitrogen, amino acids, phosphorus, starch and fat, apparent metabolizable energy, apparent ileal digestible energy, and apparent retention of phosphorus and nitrogen. The addition of 500 U phytase per kg diet to the phosphorus-deficient maize-soya-bean-meal diet improved the performance and toe ash contents of broilers to equal those given the positive control diet. Ileal phytate degradation data provided direct evidence to the efficacy of phytase in hydrolysing the phytic acid. Addition of 500 U phytase per kg to the maize-soya-bean-meal diet which contained 3·0 g phytate-phosphorus per kg resulted in more than doubling of phytate degradation from 0·218 to 0·481. Supplemental phytase improved ileal digestibility of nitrogen, amino acids, starch and lipids, with these improvements being eventually reflected in enhancements in ileal digestible energy and apparent metabolizable energy.

Grazed pasture, which is the cheapest source of nutrients for dairy cows, should form the basis of profitable and low-input animal production systems. Management of high-producing dairy cows at pasture is thus a major challenge in most countries. The objective of the present paper is to review the factors that can affect nutrient supply for grazing dairy cows in order to point out areas with scope for improvement on managing variations in nutrient supply to achieve high animal performance while maintaining efficient pasture utilisation per hectare (ha). Reviewing the range in animal requirements, intake capacity and pasture nutritive values shows that high-producing cows cannot satisfy their energy requirements from grazing alone and favourable to unfavourable situations for grazing dairy cows may be classified according to pasture quality and availability. Predictive models also enable calculation of supplementation levels required to meet energy requirements in all situations. Solutions to maintain acceptable level of production per cow and high output per ha are discussed. Strategies of concentrate supplementation and increasing use of legumes in mixed swards are the most promising. It is concluded that although high-producing cow cannot express their potential milk production at grazing, there is scope to improve animal performance at grazing given recent developments in our understanding of factors influencing forage intake and digestion of grazed forages.