• Second generation GM foods: perspectives on likely future acceptance by Irish consumers

      O'Connor, Elaine; Cowan, Cathal; Williams, Gwilym; O'Connell, John J.; Boland, Maurice; Downey, Gerard; Teagasc Walsh Fellowship Programme; Safefood; Safefood (Teagasc, 2005-07)
      Two hypothetical second-generation genetically-modified (GM) products, a yogurt and a dairy spread, were evaluated by consumers. Second-generation GM food products offer specific consumer benefits - in the case of this study, health benefits.
    • Second Generation GM Foods: Perspectives on Likely Future Acceptance by Irish Consumers

      O'Connor, Elaine; Cowan, Cathal; Williams, Gwilym; O'Connell, John J.; Boland, Maurice; Downey, Gerard (Teagasc, 01/07/2005)
      Two hypothetical second-generation genetically-modified (GM) products, a yogurt and a dairy spread, were evaluated by consumers. Second-generation GM food products offer specific consumer benefits - in the case of this study, health benefits.
    • Shortening the interval to resumption of ovarian cycles in postpartum beef cows.

      Diskin, Michael G.; Mackey, D.R.; Stagg, K.; Roche, J.F.; Sreenan, J.M. (Teagasc, 2001-02-01)
      • In beef cows the interval from calving to first ovulation, or postpartum interval, is affected by nutrition and by the suckling effect of the calf. • The suckling effect is the biggest determinant of this interval, comprising: (i) physical contact and (ii) maternal bonding between cow and calf. Restricted suckling and calf isolation induce a rapid resumption of oestrous cycles. • Prepartum nutrition is the next most important determinant of the postpartum interval. Cows that calve in poor body condition have a longer interval than cows that calve in good body condition. • Increasing the level of nutrition in the postpartum period has only a limited effect in shortening the postpartum interval. • In most cows the first postpartum ovulation is silent and is succeeded by a short oestrous cycle of approximately 8-10 days. The first observed oestrus occurs prior to the second ovulation. • When used in combination with calf isolation and restricted suckling, progesterone pre-treatment for 6 days induces oestrus in the majority of cows and eliminates the short oestrous cycle. • The prolonged postpartum interval in beef cows is not due to failure of ovarian follicle development but to failure of successive dominant follicles to ovulate due to the inadequate frequency of LH pulses.
    • The Significance of Heavy Metal and Organic Micropollutants in Soils.

      McGrath, David; McCormack, R.J. (Teagasc, 1999-11-01)
      The southeastern region of Ireland, representing 22% of the land area of the country, has been systematically sampled. Soils have been analysed for a range of heavy metals and persistent organics. These soils have now been archived and are available for future analyses as required. Analyses conducted to date, the results of which are discussed here, are for soil parameters pH and organic matter, for major components, aluminum, iron, and manganese, for trace elements (heavy metals) arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, selenium and zinc and for organics, hexachlorobenzene, hexachloro-cyclohexanes, and for DDT and its metabolites. Other organics, polychlorinated biphenyls and polycyclic aromatic hydrocarbons, were examined in a proportion of soils. Results have been statistically analysed and frequency distributions have been calculated. Geographic distributions have also been plotted and localized concentrations have been found for most elements. Geochemical factors are considered to be largely responsible for most of these localized concentrations. Aerial deposition of lead and selenium was also indicated. Historic usage of DDT and g - HCH was detected in soils with different land uses. Overall, little serious contamination of soils, especially that caused by man, by toxic elements was evident. However, as many as 21% of soils breached the provisions of the EU Sewage Sludge Directive for heavy metals in soil.
    • Significance of Lactobacilli in Cheddar Cheese

      Cogan, Tim; Beresford, Tom; Drinan, Finbarr; Palles, Tony; Fitzsimons, Nora (Teagasc, 1998-09-01)
      The objectives of this project were to isolate and identify the non-starter lactobacilli in mature Cheddar cheese, identify strains which impart mature flavours to cheese and determine their role in developing cheese flavour. The main conclusions were as follows: Based on an analysis of 18 mature Cheddar cheeses, selected from 7 commercial manufacturers, non-starter lactic acid bacteria typically numbered, as expected, 106-108 per gram and were dominated (97 percent) by Lactobacillus paracasei. Although a small number of strains (typically 1 to 4) was found in each cheese there was considerable strain diversity in cheeses within as well as between manufacturing plants. When selected strains were investigated for survival and flavour enhancement when added (as starter adjuncts) with the normal starter cultures in Cheddar cheese manufacture, it was found that they remained dominant for up to 3 months of ripening. Commercial grading of these cheeses at 3 and 6 months confirmed that the added strains did modify flavour development and one (DPC 4103), in particular, had a beneficial effect. It was confirmed that two selected strains of non-starter lactobacilli were capable of metabolising citrate under the conditions of Cheddar cheese ripening and, consequently, if present in sufficient numbers, would influence flavour development. The work was greatly facilitated by the successful and novel adaptation of a modern rapid molecular technique (RAPD) for species and strain classification. In summary these studies found that one species of lactobacilli (Lb. paracasei) was the dominant non-starter lactic acid bacteria in mature Cheddar cheese. Although a wide variety of strains were identified, only a few were found in any particular cheese, suggesting their likely role in cheese flavour diversity even within the same manufacturing plant. This suggests the potential for flavour control or enhancement through the selective and controlled use of non-starter lactic acid bacteria. Preliminary investigations of the metabolism of those organisms supports this view and a follow-up study now in progress should provide greater clarity on this matter.
    • A Slurry Spreader to Meet Farming Needs and Environmental Concerns

      Ryan, Declan (Teagasc, 2005-09-01)
      The splash plate slurry spreader is inexpensive and robust but it is not environmentally friendly. It releases most of the ammonia (NH3) in slurry, emits strong odours and distributes the remaining nutrients unevenly. The object of this report is to identify improvements to slurry spreaders that may eliminate these shortcomings. Several gases are released during and after slurry spreading. NH3 contributes to acidification of the environment and is emitted almost entirely from agriculture.Over 30% of European NH3 emissions come from slurry spreading.The Gothenberg agreement (UNECE, 1999) requires a reduction in national NH3 emission to 8% below 1990 levels. Emission of this gas from band, TF (trailing foot) and injector slurry spreaders is 40, 40 and 20% respectively of that from conventional splash plate machines. A switch to spreaders with lower emissions would provide sufficient reduction to satisfy the Gothenberg objective. Odour from livestock units gives rise to many complaints but there is little evidence that it is a health hazard. Emission of the vapours from slurry spreaders is in the order; (splash plate)>(band)> (TF and injector). Other gases (methane and nitrous oxide) are released primarily after injection. Infection of humans by slurry-borne organisms is not common. In general the differences between spreaders in regard to pathogens are not significant but this conclusion may not apply in all cases. Slurry nutrients amount to 40% of the N and 65% of the P required in agriculture. Several commercial and experimental methods exist to measure slurry nutrient content. Field application using a splash plate and vacuum tanker gives highly variable distribution. Any of the other spreaders reviewed here combined with a fixed displacement pump achieve more uniform application. Accurate spreading reduces the need for excess application so losses to water from soil are reduced. This conforms to the Water Framework Directive. Deep injection and incorporation can reduce loss of P from slurry but other spreading methods will not normally reduce the risk of P loss at spreading time. The proposed tanker consists of a closed tank with running gear fit for road and field conditions. A TF spreader is fitted at the back. The slurry is handled by a fixed displacement pump which fills the tank or empties it through the spreader. The pump must be protected from obstacles so an intake filter or chopper filter should be included. This slurry spreader would reduce emission of NH3 and odour and increase the recycling of slurry nutrients to crops. It is more expensive than splash plate machines but if widely adopted it could be an economical solution to the UNECE requirement to reduce NH3 emissions. Alternatives to improving spreaders exist. These include digesting slurry, and reducing emissions from livestock housing and slurry storage. With the exception of digestion these offer poor prospects of success especially in relation to odour reduction and exploitation of slurry nutrients. The cost of providing this equipment on Irish farms is likely to be between €200m and €800m and depends on the options chosen.
    • The Socio-economic Sustainability of Rural Areas in Ireland

      Leavy, Anthony (Teagasc, 2001-04-01)
      Over the period 1971 to 1996 District Electoral Divisions (DEDs) with the highest rate of decline in population and employment tended to be most widespread in western and north-western counties.In these DEDs average population declined by 19 per cent and average employment by 24 per cent. • Average population increased by 65 per cent and employment increased by 77 per cent in DEDs close to large urban centres.Ap proximately 90 per cent of the increase in both population and employment occurred in these areas. • Leitrim (73 per cent) and Cavan (67 per cent) had the highest proportion of District Electoral Divisions (DEDs) that lost both population and employment in the 1971-1996 period.The counties of Kildare (7 per cent) and Wexford (11 per cent) had the lowest proportion of DEDs losing both population and employment. • Approximately half of DEDs in the Objective 1 region (west, midlands and border region) lost both population and employment in the 1971-96 period. • In the most recent five year inter-census period (1991-96), while population declined in 60 per cent of DEDs, only 20 per cent of DEDs lost employment. However, 100 per cent of population growth and 90 per cent of employment growth occurred in peri-urban areas in the 1991-96 period. • Areas with the most serious history of decline were classified into: (a) Farm Dependent situated in all areas of the country but remote from urban areas, (b) Low Density populated areas situated mainly in inland areas of the west and north-west, and (c) Peripheral areas situated mainly in the coastal regions of the west and north-west. • Optimum use of resources (principally land and labour) in areas with a history of long term decline could result in increases in gross revenue of 25 to 45 per cent.T he principal changes in resource use involve increases in off farm employment opportunities, participation by farmers in extensification and REPS programmes and the reallocation of land classified as rough grazing to forestry. • The challenge facing the various agencies involved in rural development is to ensure that development is widely spread to areas that have formerly suffered considerable decline.
    • Soil Analysis and Comparison of Soil Phosphorus Tests for the Bellsgrove Catchement, Cavan.

      Humphreys, James; Tunney, Hubert; Duggan, Pat (Teagasc, 1999-03-01)
      The Bellsgrove catchment is located in the south-east of County Cavan, on the north-west border of Lough Sheelin and is approximately 9.2 km2 in size. The Bellsgrove stream feeds into Lough Sheelin. Phosphorus loss from agricultural soils to water is perceived as an important water quality issue in the region.
    • Soil and Herbage Heavy Metal/ Trace Element Variability and Relationships at Farm and Regional Level.

      McGrath, David (Teagasc, 2000-08-01)
      Variability of heavy metal trace/element amounts in soil and herbage from 3 farms encompassing 26.5, 33.6 and 21.6 ha and in a 230 km2 surrounding area has been estimated. Variability was least in the farm with the greatest soil physical uniformity. It increased in line with increasing sampling area. In soil, variability was least (CV 10%) for sesquioxide metals, iron and aluminium, and elements chromium and nickel. It was highest where there was evidence of geochemical contamination with cadmium and selenium. In general, variability was higher (>20% CV) for extractable components including copper, zinc and manganese. Regression analysis of elements in soil showed up a number of useful associations particularly for the volatiles selenium, sulphate sulphur, mercury, cobalt, vanadium and fluorine with soil organic matter. Associations were also found between fluorine, vanadium and chromium. • Elements in herbage exhibited two types of associations (i) those reckoned to be within the plant and confined mostly to major elements and (ii) those involving metals associated primarily with soil and indicative of the extent to which herbage was contaminated by soil. • Elements that showed lower variability in soil exhibited large variability in herbage. These included iron, aluminium, chromium, vanadium and fluorine, where the cause was attributed to contamination of herbage by soil. It was suggested that iron could be used almost equally as well as titanium as an indicator of the degree to which herbage has been contaminated by soil. • Long term monitoring of herbage for selenium content highlighted the unreliability of relying on a single determination to characterise the selenium status of pasture.
    • Soil Properties and their Influence on Grassland Production under Low Input and Organic Farming Conditions

      Leonard, C.; Mullen, G.J.; Culleton, Noel; Breen, J.; Teagasc Walsh Fellowship Programme (Teagasc, 2006-01-01)
      This project set out to identify soil properties that most influence grassland production under low mineral nitrogen input conditions. Sixteen farms were selected in Counties Limerick and Clare and the soil sampled. Soil physical and chemical characteristics and soil biological aspects involved in the carbon and nitrogen cycles were studied in the laboratory. Nutrient additions to farms as well as the nature of grazing by livestock (numbers, types of grazing animals, grazing practices), grassland management, and production from the farms were recorded.
    • Soil properties and their influence on grassland production under low input and organic farming conditions.

      Leonard, C.; Mullen, G.J.; Culleton, Noel; Breen, J. (Teagasc, 2006-01-01)
      This project set out to identify soil properties that most influence grassland production under low mineral nitrogen input conditions. Sixteen farms were selected in Counties Limerick and Clare and the soil sampled. Soil physical and chemical characteristics and soil biological aspects involved in the carbon and nitrogen cycles were studied in the laboratory. Nutrient additions to farms as well as the nature of grazing by livestock (numbers, types of grazing animals, grazing practices), grassland management, and production from the farms were recorded.
    • Soil Water Regimes.

      Diamond, J.; Sills, P. (Teagasc, 2001-07-01)
      Soil moisture tension was monitored, for three years, at three sites representing different natural soil drainage classes that were defined morphologically. The soils comprised: • Gley, poorly drained, loam • Brown Earth, well drained, loam • Brown Earth, somewhat excessively drained, sandy loam. The main features of the moisture regime were: • Average annual soil water tension was analogous to the natural drainage classification and followed the sequence: somewhat excessively drained > well drained > poorly drained. • Some horizons that lacked visible evidence of reduction, in the subsoil of the Brown Earths, were saturated for long periods. • The Brown Earths were unsaturated, at 15 cm depth, throughout the three-year period. • The Gley was saturated at 15 cm depth for up to nearly four months per year. This implies that the risk of overland flow, due to saturation excess, differs among soil types. The risk is probably significant on Gleys, which occupy 25 percent of the land area; it is probably small or negligible on Brown Earths and analogous soils, which comprise over forty percent and account for virtually all of the intensive agriculture in the country.
    • A spatial analysis of agriculture in the Republic of Ireland, 1991 to 2000

      Crowley, Caroline; Meredith, David; Walsh, Jim A. (Teagasc, 01/01/2007)
      By linking farm census and administrative data from the CSO and DAF to a geographic information system and analysing the mapping output, this project shows the continued broad division of farming in the state into marginal farming areas in the north and west and more commercial farming areas in the south and east. While this division was compounded by the 1992 CAP reforms, and commercial farming became more spatially concentrated over the 1990s, the influence of the development in the non-farm economy, particularly in peri-urban rural areas across the state, provided local drivers of change that encouraged enterprise substitution to beef production, the farming system most readily combined by farm holders with another job. A full report on the mapping output will be produced in a forthcoming publication (see publications list).
    • Spatial Modelling for Rural Policy Analysis

      Hynes, Stephen (Teagasc, 2006-01-01)
      The objective of the project was to provide the diverse group of interest groups associated with the agri-food sector (farmers, policy makers etc.) with a microsimulation tool for the analysis of the relationships among regions and localities. This tool would also be able to project the spatial implications of economic development and policy change in rural areas. To this end the SMILE (Simulation Model for the Irish Local Economy) model was developed. SMILE is a static and dynamic spatial microsimulation model designed to analyse the impact of policy change and economic development on rural areas in Ireland. The model developed provides projection for population growth, spatial information on incomes and models farm activity at the electoral division (ED) level. The sub-projects funded under this project were concerned with the simulation, development and enhancement of a spatial econometric model of the Irish rural economy which would compliment the existing econometric models used in Teagasc; focusing on the agriculture and food sectors, previously constructed under the auspices of the FAPRI-Ireland Partnership by staff at Teagasc and NUI Maynooth. That partnership has produced an econometric model of the entire agri-food sector that has been simulated to produce estimates of the impact of policy changes on commodity prices, agricultural sector variables, food industry production, consumption of food both in Ireland and the EU and trade in food products, as well as costs, revenue and income of the agricultural sector. The SMILE model was built to compliment these other econometric models by using an holistic modeling approach that takes into account the spatial difference of rural populations, rural labour force and rural income.
    • Spread of brain and spinal cord material during beef slaughter

      Daly, Dyan J.; Prendergast, Deirdre M.; Sheridan, James J. (Teagasc, 2002-04)
      Emboli of brain tissue in the lungs have been reported in cases following severe head injury (McMillan 1956) and birth trauma in people (Hauck e t al 1990) and in cattle following stunning (Bauer 1996; Garland 1996). This has important implications for food safety if the brain tissue of stunned cattle is infected with the prion responsible for bovine spongiform encephalopathy (BSE), (Prusiner 1991). BSE emerged following changes in the rendering process in the early 1980s which allowed the aetiologic agent to survive, contaminate protein feed supplement and infect cattle (Brown e t al. 2001). Within a short period of time after the first case of BSE, concerns were expressed regarding the transmission of BSE to humans and the likelihood of infection from consumption of beef and beef products. This has become increasingly significant with the discovery of the link between BSE in cattle and variant Creutzfeldt-Jakob disease (vCJD) in man (Bruce e t al 1997).
    • Status Report on Acrylamide in Potato Products

      Brunton, Nigel; Gormley, Ronan T.; Murray, Brendan (Teagasc, 2005-01-01)
      Acrylamide is a toxin that can potentially occur in high concentrations in heated starchy foods especially potato products such as crisps and french fries. In model systems isotopic substitution studies have demonstrated that acrylamide is formed via the Maillard type reaction between the amino acid aspargine and a carbonyl source such as the reducing sugars glucose and fructose. Levels of acrylamide in cooked potato products are primarily influenced by the levels of reducing sugars in the product and this in turn is influenced by storage time, temperature and variety of potato used. During cooking acrylamide formation begins to occur at temperatures above 100°C and increases up to temperatures of 220°C but decreases thereafter due to thermal degradation of the compound. Risk assessment studies on acrylamide intakes have been conducted in a number of countries and mg/kg body weight daily intakes have been estimated to be between 0.2-0.8. Adequate analytical techniques exist for quantification of acrylamide in potato and are mainly based around liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) and gas chromatography mass spectrometry (GC-MS) techniques
    • Stimulation of Propionic Acid Bacteria by Lactic Acid Bacteria in Cheese.

      Condon, S.; Cogan, Tim; Piveteau, P.; O'Callaghan, Jim; Lyons, B. (Teagasc, 2001-06-01)
      In the manufacture of Swiss-type cheese two successive fermentations occur. During manufacture, lactic acid bacteria (LAB), particularly Streptococcus thermophilus, Lactobacillus helveticus and Lb. delbrueckii subsp. lactis, convert lactose to lactate while, during ripening, propionic acid bacteria (PAB) convert lactate to propionic acid, acetic acid and carbon dioxide (CO2). CO2 is responsible for eye formation and propionic acid results in the typical nutty flavour of Swiss-type cheese. There have been a few reports of interactions between a small number of LAB and PAB but the compounds involved have not been identified. A better understanding of this phenomenon is necessary to select strains of PAB for cheesemaking and improve the quality of hard cheeses. Cheese cannot be used for such a study because of its complexity and the length of time it is ripened. Hence, a simple whey-based model developed by Piveteau et al (1995) was successfully used to study the interactions between LAB and PAB. In this procedure, the LAB were grown overnight in milk and the whey was collected by centrifugation. After neutralisation and filter-sterilisation, the growth of strains of PAB in this whey and in a control whey produced from the same milk by acidification with lactic acid were compared. The objectives of this study were to refine the model of Piveteau et al (1995) to study the interactions between LAB and PAB and to determine the nature of the stimulant(s) produced by the LAB. * Thirty-two combinations of different commercial strains of PAB and LAB were evaluated in a modified whey model. None showed any inhibition and all showed some degree of stimulation but the extent of the stimulation depended on the particular pair of PAB and LAB used. * An inhibitor of PAB was found in milk, which prevented the growth of PAB from low (105 cfu/ml) but not from high inocula (107 cfu/ml). The inhibitor was heat stable (to autoclaving for 15 min), of low molecular mass and could be removed by pre-growth of some but not all starter LAB in milk. * Growth of P. freudenreichii DPC 3801 in control whey was stimulated by peptone, tryptone, casein hydrolysed by the crude proteinase of Lb. helveticus DPC 4571 and by pre-growth of the lactobacillus in milk, but not by vitamins (riboflavin, thiamine, PABA, Ca panthothenate, biotin and nicotinic acid) or minerals (MgSO4, MnCl2, CoCl2 and CuSO4). * Growth of Lb. helveticus DPC 4571 in milk resulted in significant increases in peptide and amino acid production but the amino acids produced did not stimulate the growth of the PAB. Based on these results it was concluded that the stimulation was due to production of peptides by the LAB from casein. * The whey model developed by Piveteau et al (1995) to study the interactions between PAB and LAB was shown to be reproducible. Adjustment of the pH of the whey to 5.4 rather than 6.0, incubation at 24ºC rather than 30ºC and addition of 1% NaCl, to simulate cheese ripening conditions allowed growth of all the PAB tested. * Several chromatographic procedures, including ion-exchange, gel permeation and reverse-phase, high-pressure liquid chromatography failed to categorically identify the peptide(s) responsible for the stimulation of the PAB. In some of these chromatographic systems,the stimulatory activity was shown to be present in several peaks implying that different peptides were involved.
    • Storage stabilities of fuel grade camelina, sunflower and rapeseed methyl esters.

      Frohlich, A. (Teagasc, 1999-12-01)
      The storage stabilities of fuel grade camelina, sunflower and rapeseed methyl esters were evaluated in airtight and open containers. Commercial amounts (200 litres) of the methyl esters were stored in airtight drums and sampled regularly, and the effects of air exposure were evaluated from sixteen days laboratory-scale accelerated storage tests at 65oC. None of the methyl esters in airtight drums deteriorated during eighteen months of storage; composition, viscosities and free fatty acid levels remained unchanged. The accelerated storage test in open containers, however, indicated that exposure to air can cause rapid oxidation of each of the three methyl esters. However, oxidation can be delayed by the presence of tocopherols (natural antioxidants) in the methyl ester, and it can be further delayed by the presence of an unidentified carotenoid. The exceptional stability of rapeseed methyl ester seems to be due to a combination of relatively high levels of Μ-tocopherol and the unidentified carotenoid. The rates of oxidation (i.e. rate of increase of viscosity etc.) of sunflower and camelina methyl esters were about the same, but rapeseed methyl ester oxidised slower. The observed relative rates of oxidation could be predicted from the levels of reacting double bonds calculated from the oxidation data, but not from iodine numbers.
    • The Strategic Development of Irish Livestock Marts.

      Hennebry, T.; Pitts, Eamonn; Harte, Laurence (Teagasc, 2002-09-01)
      A study of co-operative livestock marts revealed that cumulative marts turnover decreased by 26% from 1990 to 1999: Commission income as a percentage of turnover increased from 2% in 1990 to 3.2% in 1999. However operating expenses increased by 25% from 1990 to 1999. Operating expenses have since 1997, surpassed commision income, thus putting co-op marts in a collective loss making situation from their mart activities. However overall profit from co-op mart societies (including profit generated from all business activities) almost doubled between 1990 and 1999. While overall profitability of livestock marts societies has increased, twelve of thirty nine marts were in a loss making situation in 1999. Four of these marts have been in a permanent loss - making situation since 1990. All loss making societies in 1999 have little or no involvement in non-mart activities and almost all operate from just one site. In general, the large diversified societies are showing profitability. A number of strategic alternatives to deal with their situation were placed before mart executives. A diversification strategy is by far the most likely strategy to be adopted by marts for the future Most marts are unlikely to consider merging with other societies. Most marts have no plans to downsize and exit from the industry is not considered an option by any society. There is a recognition that there is an urgent need to rationalise the industry, but this strategy is likely to meet with a strong resistance from marts . A problem with rationalisation is that there are no incentives to make this strategy a reality. On the one hand, management would be reluctant to follow this approach, as it may be perceived to reflect badly on their own performance or may result in them being forced to seek alternative employment. On the other hand, the shareholders have little to gain and much to lose if the mart closes. Projections of past trends and impact of new policies would suggest continuing decline in turnover and profitability in the co-operative mart sector. Rationalisation is therefore absolutely essential. The industry cannot sustain the present number of marts. Diversification seems the most obvious option for the future of the industry. In general marts that have diversified are profitable and there is no reason why this trend cannot continue into the future.
    • Strategies to alleviate reproductive wastage in dairy cows

      Butler, Stephen (Teagasc, 2007-01-01)
      grass-based systems of production. A series of studies were carried out to (i) improve our understanding of the physiological basis of poor reproductive performance; (ii) examine management and nutritional strategies to improve fertility; and (iii) examine the potential role of extended lactation to mitigate the effects of poor reproductive performance. A comprehensive characterization of the North American and New Zealand strains of Holstein-Friesian cow was carried out. North American cows produce a greater volume of milk, but yield a similar amount of fat and protein on a grass-based diet. Dry matter intake was greater for the larger NA strain, but energy balance did not differ during the first 20 weeks of lactation. Circulating concentrations of metabolic hormones and metabolites during the early lactation period were indicative of lesser bioenergetic status in the NZ strain compared to the NA strain. During established lactation, circulating concentrations of insulin-like growth factor-I (IGF-I) were greater in the NZ strain. Liver biopsies collected at day 35 and day 150 postpartum indicated that the greater circulating concentration of IGF-I was due to greater hepatic mRNA abundance of IGF-I and acid labile subunit (ALS). Embryos were collected from both strains after superovulation. A greater proportion of the embryos recovered were transferable in the NZ strain compared with the NA strain, indicating that the previously reported differences in reproductive performance were manifest as early as 7 days post-insemination. Collectively, the results of the study indicate that the NZ strain are genetically better equipped to survive on a pasture-based seasonal calving system. A study was carried out to examine the effect of dry period duration and dietary energy density on milk production, bioenergetic status and postpartum ovarian function. Omitting the dry period and increasing dietary energy density both resulted in improved energy balance and metabolic status, but omitting the dry period reduced the postpartum interval to resumption of cyclicity whereas increasing dietary energy density had no effect. Omitting the dry period reduced the inherent drive to produce milk, and allowed the cow to fully meet nutritional requirements from voluntary dry matter intake. Increased dietary energy density also allowed the cow to more closely meet nutritional requirements from a higher energy density diet, albeit at a greater milk yield. The results suggest that the mechanism by which a cow arrives at a particular energy balance status may be as important as energy balance per se. One of the main energy costs associated with lactation is milk fat. Trans 10, cis 12 conjugated linoleic acid (CLA) is a geometric and positional isomer of linoleic acid that reduces milk fat synthesis in a dose dependent manner. Supplementing cows with CLA resulted in improved energy balance status during the transition period and reduced postpartum body condition score loss. Some indices of reproductive performance were also improved. In seasonal systems, cows that fail to become pregnant by the end of the breeding season are typically culled and replaced. When reproductive performance is poor, this represents a major cost on dairy farms. A study was carried out to examine the feasibility of extending the lactation to 22 months, resulting in a calving interval of 24 months instead of 12 months. High yielding cows produced the equivalent of 2 normal lactations in an extended lactation system. An economic analysis indicated that an efficient spring calving system with a compact calving pattern and a 12 month calving interval is still the most profitable, but with high yielding cows extending the lactation of non-pregnant cows is more profitable than culling and replacing.