Recent Submissions

  • Soil cover of tubers and the percentage of green tubers at various inter-row widths

    Bernik, R.; Godesa, T.; Dolnicar, P.; Vucajnk, F. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    In the years 2002, 2003 and 2004, a field trial was conducted involving three inter-row widths (66, 75 and 90 cm) and three potato cultivars (Agria, Bright and Carlingford). Increasing the inter-row width (IRW) increased both the cross-sectional area of the ridge and ridge height measured before the harvest. With an IRW of 66 cm the majority of tubers were located directly under the ridge surface (at a depth of < 5 cm), which resulted in the highest percentage of green tubers among the three IRW values. At the 90 cm IRW, in particular, the vast majority of tubers was distributed deeply in the ridge (at a depth of > 5 cm), thus generating the smallest percentage of green tubers. Compared to the other two cultivars, Carlingford produced tubers distributed at a larger ridge depth and subsequently yielded the lowest percentage of tubers covered with less than 5 cm of soil. On the other hand, Agria had a wider horizontal span of tubers than the other two cultivars.
  • Prediction of cull cow carcass characteristics from live weight and body condition score measured pre slaughter

    Minchin, W.; Buckley, Frank; Kenny, David A.; Keane, Michael G.; Shalloo, Laurence; O'Donovan, Michael (Teagasc, Oak Park, Carlow, Ireland, 2009)
    A study was conducted to provide information on the degree of carcass finish of Irish cull cows and to investigate the usefulness of live animal measurements for the prediction beef breeds (albeit with a moderate R2 value compared to the carcass weight prediction) using objective, non-intrusive and easily measured live animal measurements, should be of benefit to farmers finishing cull cows in Ireland. of cull cow carcass characteristics. Live weight (LW) and body condition score (BCS) were recorded on cows entering an Irish commercial slaughter facility between September and November, 2005. Data pertaining to sire breed, age and carcass characteristics were collected and subsequently collated for each cow. For analysis, cows (n = 2163) were subdivided into three breed categories: dairy breed sired by Holstein/ Friesian (FR), sired by early-maturing beef breeds (EM) and sired by late-maturing beef breeds (LM). The proportion of cows slaughtered at the desired (TARGET) carcass standard (cold carcass weight ≥ 272 kg, carcass conformation class ≥ P+ and carcass fat class ≥ 3) was low (on average 0.30), but did differ (P < 0.001) between the dairy and beef breed categories (0.22, 0.47 and 0.53 for FR, EM and LM categories, respectively). Regression procedures were used to develop equations to predict cold carcass weight, carcass conformation score, carcass fat score and proportion in the TARGET category from LW and BCS. Equations predicting cold carcass weight had high R2 values for all breed categories (0.81, 0.85 and 0.79 for the FR, EM and LM, respectively). Equations predicting carcass fatness had moderate R2 values for the beef breed categories (0.65 and 0.59 for the EM and LM, respectively). Equations predicting carcass conformation and the TARGET category yielded lower R2 values. The successful prediction of carcass weight for all breed categories and of carcass fatness for the
  • Potential food production from forage legume-based-systems in Europe: an overview

    Peyraud, J.L.; Le Gall, A.; Luscher, A. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Intensification of EU livestock farming systems has been accompanied by the development of maize silage and intensively fertilised grasses at the expense of forage legume crops. However in the new context of agriculture, the development of forage legumes constitutes one of the pillars for future livestock farming systems with high environmental and economical performances. Yield benefits of grass-clover mixtures are equivalent fertiliser N inputs of 150 to 350 kg/ha, and productive grass-clover mixtures can fix 100 to 380 kg N per hectare symbiotically from the atmosphere. Animal intake of legumes is high and the rate of decline of legume nutritional quality with advancing maturity is less than for grasses, especially in the case of white clover, which makes mixed pastures easier to manage. Animal performances at grazing are identical or higher on clover-enriched pastures. Due to their high protein concentration, conserved forage legumes fit well with maize silage. Forage legumes increase the concentration of beneficial α-linolenic acid in ruminant products. Environmental balance of forage legumes is positive. Increasing the proportion of white clover at the expense of mineral N fertilisation can reduce the risk of nitrate leaching. Because forage legumes only require solar energy to fix N from the air, they also reduce energy consumption and associated impacts. They contribute to reduce the global warming potential of livestock systems by reducing emission of enteric methane and nitrous oxide from pasture and crop production. As an element of arable crop rotations, grass-clover leys suppress pests, diseases and weeds, improve soil structure and prevent soil erosion and nitrate leaching. Nevertheless, forage legumes have some limitations: expensive to harvest, difficulties of conservation, management of the associations. To take full advantage of forage legumes in the future, new research and development are required as well as financial support from the EU.
  • Nutritive value of forage legumes used for grazing and silage

    Dewhurst, Richard J.; Delaby, L; Moloney, Aidan P; Boland, T.; Lewis, Eva (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Legume forages have an important position in ruminant production in Western Europe and with further development can play an even larger role. Red clover for silage and white clover in grazed swards lead to enhanced growth rate and milk yield in comparison with pure grasses. Much of the production benefit of these legumes relates to enhanced intake since digestibilities are not markedly different to grasses. The higher intake of legume silages reflects differences in the cell structure of legume plants which combined with high fermentation rates means that they break down into small particles in the rumen, and leave the rumen more rapidly than perennial ryegrass. Ease of ingestion leads to high rates of intake, which explains higher intakes for grazed legumes. A further benefit of legumes is the reduced rate of decline in digestibility with advancing maturity. Whilst legumes have limited effects on gross milk composition or carcass characteristics, there are marked increases in levels of beneficial n−3 PUFA. Legumes have often led to a reduction in methane production from the rumen and again, this relates to both physical and chemical differences between forage species. The high rates of release of soluble protein and of breakdown to small particles from clovers and lucerne is associated with susceptibility to bloat, which is a limitation to further exploitation in grazing systems. The high concentration of rapidly degraded protein in legumes also leads to inefficient utilisation of dietary N and increased urinary N output. Research with tanniniferous forages, such as birdsfoot trefoil and sulla, demonstrates the potential for future legumes with reduced environmental and health effects, though these particular forage legumes are not well adapted to temperate regions of Western Europe that are the focus of this review.
  • A note on the use of FTA™ technology for storage of blood samples for DNA analysis and removal of PCR inhibitors

    Mullen, Michael Paul; Howard, Dawn J.; Powell, R.; Hanrahan, James P (Teagasc, Oak Park, Carlow, Ireland, 2009)
    FTA™ technology is widely used across many molecular disciplines for sample capture, storage and analysis. The use of this technology for the long-term storage of blood samples for DNA analysis was examined as well as its potential to remove inhibitors from DNA samples previously extracted from blood with PCR inhibitors remaining. It was found that blood spots stored on FTA™ cards for 8 years at room temperature gave successful PCR products and that FTA™ cards are a useful tool for removing substances in samples which interfere with or inhibit, the PCR reaction.
  • A note on muscle composition and colour of Holstein-Friesian, Piedmontese × Holstein-Friesian and Romagnola × Holstein-Friesian steers.

    Keane, Michael G.; Allen, Paul (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Holstein-Friesian (HF), Piedmontese × Holstein-Friesian (PM) and Romagnola × Holstein-Friesian (RO) steers were compared for muscle composition and colour. A total of 120 steers in a 3 breed types (HF, PM and RO) × 2 feeding levels (low and high) × 2 finishing periods (short, S and extended, E) factorial experiment were used. Three samples of m. longissimus were taken for chemical analysis, measurement of drip loss and Hunterlab colour measurements. Muscle moisture and protein concentrations were lower, and lipid concentration was higher for HF than for PM and RO, which were similar. There were no effects of feeding level on chemical composition, but after blooming all colour values except hue were lower for the higher feeding level. The E finishing period reduced moisture, protein, drip-loss, L (lightness), a (redness) and chroma values. It is concluded that PM and RO had similar muscle composition but HF had a higher lipid concentration. Feeding level had few effects on muscle composition, but extended finishing increased all measures of fatness and reduced colour values.
  • Influence of testing procedure on evaluation of white clover (Trifolium repens L.)

    Gilliland, T.J.; McGilloway, D.; Conaghan, P. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    This study examined data sets derived from the white clover cultivar evaluation programmes of AFBI (N. Ireland), and DAFF (Republic of Ireland) to determine whether elite performing genotypes are identifiable, independent of test procedure and leaf size factors. Genetic variation in yield and persistency, independent of the leaf size continuum effect, was observed. Identification of elite cultivars by breeders or testers therefore required readjustment of assessment standards to account for the mostly curvilinear relationships between performance and leaf size. The different testing procedures, involving cutting or grazing at different heights, frequencies and nitrogen rates changed the relative performances between the cultivars, making it difficult to predict performance potential beyond specific test conditions. The underlying causes for these changes in rankings was considered, including sensitivity to season and location, the antagonistic affects of defoliation pressure and companion grass competition, the independence of different seasonal profiles and the probable role of other morphological characteristics. In is concluded that testing authorities must calculate the management by leaf size relationships to adjust pass/fail standards if elite performing cultivars are to be correctly indentified.
  • Feed intake pattern, behaviour, rumen characteristics and blood metabolites of finishing beef steers offered total mixed rations constituted at feeding or ensiling

    Cummins, B.; O'Kiely, Padraig; Keane, Michael G.; Kenny, David A. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Two experiments were undertaken. In Experiment 1, behaviour, intake pattern and blood metabolites, were recorded for steers offered total mixed rations (TMR) based on grass silage and concentrates, and constituted either at ensiling (E-TMR) or feedout (F-TMR). Fourteen continental crossbred steers (mean starting weight 505 (s.d. 41.5) kg) were assigned to each of the following eight treatments: grass silage offered ad libitum (SO), E-TMR diets constituted in approximate dry matter (DM) ratios of grass:concentrates of 75:25 (EL), 50:50 (EM) and 25:75 (EH), F-TMR diets constituted in approximate DM ratios of grass silage:concentrates of 75:25 (FL), 50:50 (FM) and 25:75 (FH), and finally concentrates ad libitum (AL). Total DM intake increased linearly (P < 0.001) and the time spent eating and ruminating decreased linearly (P < 0.001) with increasing concentrate proportion. Animals on the F-TMR diets had higher total DM intakes (P < 0.05) and plasma glucose (P < 0.05) and urea (P < 0.001) concentrations than animals on the corresponding E-TMR diets. No effect of method of feed preparation on intake pattern or behaviour was recorded. In Experiment 2, four ruminally cannulated Holstein-Friesian steers of mean initial live weight 630 (s.d. 23.2) kg were used to evaluate rumen characteristics for four of the above diets (FL, EL, FH and EH) in a 4 × 4 latin square design. Higher concentrate diets resulted in lower rumen pH (P < 0.05), higher lactic acid (P < 0.001) and ammonia (P < 0.05) concentrations and lower acetate:propionate (P < 0.05). F-TMR was associated with a higher (P < 0.05) rumen volatile fatty acid concentration but no difference in other rumen fermentation characteristics compared to E-TMR. Concentrate proportion and method of feed preparation had no effect (P > 0.05) on rumen pool sizes but animals consuming the high concentrate diet had a faster (P < 0.05) rumen passage rate of NDF than animals on the low concentrate diet.
  • An evaluation of two grassland-based systems of mid-season prime lamb production using prolific ewes of two genotypes

    Keady, Tim; Hanrahan, James P; Flanagan, S. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    A 4-year study was undertaken to evaluate the effects of two contrasting management systems [year-round grazing (YRG) and normal seasonal grazing followed by indoor feeding during winter (GWF)] on performance of mid-season lambing ewes. On the GWF system, the annual stocking rate was 14.4 ewes/ha, grass silage was conserved for winter feeding indoors, and the ewes were lambed indoors and were then turned out to pasture. The YRG system was stocked at 10.5 ewes/ha, was grazed during the winter, had outdoor lambing and the animals had access to all the farmlet for summer grazing. The ewes were Belclare and Cheviot × Belclare which were balanced across systems. Mean lambing dates and fertiliser N application rates were 20 and 30 March, and 85 and 92 kg/ha, for the GWF and YRG systems, respectively. Concentrate supplementation during late pregnancy was similar on both systems. For the GWF and YRG systems, litter size, lamb mortality, number of lambs reared, birth weight (kg), weaning weight (kg) and lamb carcass output (kg/ha) were 2.17 and 2.24 (s.e. 0.038), 10.1 and 13.8% (P = 0.05), 1.77 and 1.78 (s.e. 0.042), 4.0 and 4.7 (s.e. 0.05, P < 0.001), 27.9 and 30.8 (s.e. 0.25, P < 0.001) and 469 and 348, respectively. Belclare ewes had a higher litter size (2.34 v 2.07; s.e. 0.038, P < 0.001) and number of lambs reared per ewe joined (1.86 v 1.69; s.e. 0.048, P < 0.01) than the Cheviot × Belclare ewes. There were no significant interactions between system and ewe breed type. It is concluded that the YRG system of prime lamb production was sustainable using prolific ewes but at a reduced stocking rate (−26%) and with greater lamb mortality relative to the GWF system. Ewe genotypes with a mean litter size of up to 2.34 lambs are suitable for both systems. Lamb carcass output of 501 kg/ha was achieved from a primarily grass-based system of mid-season prime lamb production using prolific ewes (Belclare).
  • Environmental impacts of grazed clover/grass pastures

    Ledgard, S.; Schils, R.; Erikson, J.; Luo, J. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Grazed clover/grass pastures are important for animal production systems and the clover component is critical for its contribution to N inputs via biological fixation of atmospheric N2. The resource efficiency and environmental emissions for clover/grass pastures can differ from that of N-fertilised grass-only pastures. Fixation of N2 by clover uses photosynthetically- fixed carbon, whereas fertiliser N production consumes fossil fuels and has net greenhouse gas (GHG) emissions. Clover has a higher phosphorus (P) requirement than grass and where extra P fertiliser is used for clover/grass pastures the risk of P loss to waterways is greater than for grass-only pastures. Nitrogen leaching from grazed pasture increases exponentially with increased N inputs and urinary-N contributes 70 to 90% of total N leaching. However, the few studies comparing clover/grass and N-fertilised grass-only pastures at similar total N inputs indicated similar N leaching losses. Nitrous oxide emissions from grazed pastures due to N-cycling of excreta are similar for clover/grass and N-fertilised grass-only pastures at similar total N inputs. However, grass-only pasture requires the application of N fertiliser, which will result in additional specific losses that don’t occur from clover-fixed N. Thus, total N2O emissions are generally higher for N-fertilised grass pastures than for clover/grass pastures. A summary of various whole-system and life cycle assessment analyses for dairy farms from various countries indicated that at similar total N inputs, clover/grass pasture systems can be more efficient than N-fertilised grass systems per kilogram of milk produced from an energy use and GHG perspective whereas results for nutrient losses to waterways were mixed and appear to be similar for both pasture types. In practice, other management practices on farm, such as crop integration, supplementary feeding strategy and winter management, can have a larger overall effect on environmental emissions than whether the N input is derived from fertiliser N or from N2 fixation.
  • The effect of soil moisture content on leaf extension rate and yield of perennial ryegrass

    Laidlaw, A.S. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Three experiments are described that were designed to evaluate the relationship between soil moisture and perennial ryegrass growth and leaf extension rate (LER) in loam or silt clay loam soil. When soil moisture was maintained at a range of proportions (0.5, 0.75, 1.0, 1.25) of field capacity (FC) in a pot experiment in a glasshouse, 0.75FC had consistently higher growth and LER than 0.5FC and, to a lesser extent, 1.25FC. The quadratic relationship between herbage growth and amount of water applied to maintain target field capacity, was stronger than for that between LER and the amount of water applied, with a maximum response at an application of about 2.5 L/m2 per day. In a microsward (soil depth of 30 cm in boxes 56 cm × 72 cm) trial inducing drought by withholding water for a range of durations resulted in a progressive decline in LER. When soil moisture content fell to about 0.4 of that of the consistently watered control LER was less than 0.1 of the control. However within one week of receiving water, even in the relatively severe drought treatment, LER was not significantly lower than the control treatment. LER was quadratically related to soil moisture content when soil was drying or after rewatering. In a further experiment on the microswards, reducing soil moisture content to about 0.18 g/g by limiting water in May-June resulted in a severe reduction in LER and growth rate and a decline in tillering rate. However, after application of the equivalent of 3 mm precipitation per day in late June, while soil moisture content remained relatively low (about 0.2 to 0.25 g/g soil), LER and herbage growth increased rapidly to as high as in consistently watered microswards. In a treatment in which soil moisture content eventually exceeded FC, LER and herbage growth declined with increase in excess above FC, concurring with findings in the steady state soil moisture experiment. Implications of the data for prediction of production from sown grass swards using temperate maritime grass-growth models are that: (1) during drought, when rainfall resumes, regrowth will be influenced more by amount of rainfallthan soil moisture content and (2) excess soil moisture should be taken into account, including effects of reduced nutrient uptake and post-anoxia stress.
  • Do forage legumes have a role in modern dairy farming systems?

    Woodfield, D.R.; Clark, D.A. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    Intensification in New Zealand dairy farming systems has placed greater pressure on clover performance and fitness and has highlighted the need to develop clover cultivars that are better adapted to intensive grazing systems. Increased stocking rates and increased use of nitrogen fertiliser have put enormous pressure on the contribution of clover to modern dairy systems. Future innovations such as semi-hybrid cultivars offer the potential to improve the competitiveness of legumes with nitrogen-fertilised forage grasses. Similarly, advances in condensed tannin research suggest that significant animal performance gains can be achieved in conjunction with reduced environmental impact. In order to capture these benefits, dairy farmers will need to reassess their grazing management to ensure that legumes can be maintained at economically useful levels. Novel grazing management systems that optimise the benefits provided by the grass and legume components need to be used in future dairy farming systems. Forage legumes, and especially white clover, have an important role to play in modern dairy systems.
  • Conservation characteristics of baled grass silages differing in duration of wilting, bale density and number of layers of plastic stretch-film

    Keles, G.; O'Kiely, Padraig; Lenehan, J.J.; Forristal, P.D. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    The effects of duration of wilting, bale density and number of layers of plastic stretchfilm used to wrap bales on the conservation characteristics of baled grass silage was investigated. Grass from the primary growth of a Lolium perenne dominant sward was wilted for 24, 48 or 72 h. For each duration of wilting, 54 cylindrical bales (1.2 m nominal diameter) were made with the baler at a high or low density setting for alternate bales. Bales were wrapped with 2, 4 or 6 layers of plastic stretch-film and stored outdoors for 295 days. Two layers of plastic stretch-film resulted in inferior preservation, lower digestibility and extensive mould growth and deteriorated silage. Substantial improvement occurred to each of these characteristics from applying four layers of stretch-film (P<0.05), while six layers of stretch-film brought little further improvement. When four or six layers of stretch-film were used, extensive wilting restricted fermentation and improved the standard of preservation with the apparently difficult-to-preserve herbage used in this experiment. However, under the anaerobic conditions provided by four or six layers of stretch-film neither progressive wilting nor bale density had a major effect on digestibility, or the extent of surface mould growth or deteriorated silage. It can be concluded that a minimum of four layers of conventional black plastic stretch-film were required to achieve suitably anaerobic conditions, and that the additional benefits from six layers were small. Once anaerobic conditions were achieved, extensive wilting improved the conservation characteristics of baled grass silage made from a difficult-to-preserve crop, whereas bale density had little impact.
  • Comparison of milk production from clover-based and fertilizer-N-based grassland

    Humphreys, James; Casey, I.A.; Laidlaw, A.S. (Teagasc, Oak Park, Carlow, Ireland, 2009)
    This study, conducted over four years (2003–2006), compared herbage production, nutritive value of herbage, the length of the grazing season and milk production per cow and per hectare from grassland systems based on (i) white clover (average 219 g/kg of herbage DM) (WC) receiving on average N application of 90 kg/ha (s.d. 6.4) in spring and successive 0.2 of the area over-seeded annually with white clover seed and (ii) fertilizer N (FN) input of 226 kg/ha (s.d. 9.7). The stocking density of Holstein- Friesian dairy cows on both systems was 2.0/ha 2003 and 2.2/ha in each of the following three years. There were 22 cows per system in 2003 and 24 cows per system in each of the following three years. Cows calved within a 12 week interval in spring with mean calving date in mid-February. Milk was produced until mid-December each year. Total annual herbage DM production was lower (P < 0.01) on WC than FN (0.92 of FN). There were no (P > 0.05) differences in the in vitro organic matter digestibilities of pre-grazing herbage. The crude protein concentration in pre-grazing herbage DM was higher (P < 0.001) on FN than WC: 219 and 209 (s.e. 8.4.) g/kg, respectively. There were no (P > 0.05) differences in annual production of milk per cow (mean 6524 kg; s.e. 83.9 kg), live-weight or body condition score between the two systems. There were no (P < 0.05) differences in the lengths of the grazing season, which averaged 254 days (s.e. 0.9). Although there was no difference in performance per cow, the higher herbage production indicates that a higher stocking rate and milk output per hectare was possible from FN than WC. Nevertheless, the WC swards supported an annual stocking density of 2.15/ha and a milk output of 14 t/ha.
  • Comparative growth and management of white and red clovers

    Black, Alistair D; Laidlaw, A.S.; Moot, D.J.; O'Kiely, Padraig (Teagasc, Oak Park, Carlow, Ireland, 2009)
    The aim of this paper is to provide the underpinning scientific basis for the optimum management of white and red clovers. Critical morphological and canopy characteristics which influence the yield and persistence of white and red clover in swards, and how management factors (choice of cultivar, defoliation and nitrogen (N) fertilizer) modify these are considered. Canopy development is vitally important as it determines the extent to which a) light is intercepted for photosynthesis needed for growth and b) the base of the sward is deprived of the red component in daylight, inhibiting branching of stolons and crowns in white and red clover, respectively. The role of cultivar, defoliation and N fertilizer in determining yield and persistence of the two legumes, mainly in mixtures with grass, are discussed principally in terms of morphological development and exploitation of light. It is concluded that optimum management for grass/white clover places emphasis on building up stolons and maximising contribution of clover leaf area to the upper layers of the mixed canopy and, while red clover is more competitive to grass than white clover, that benefit is lost when a grass/red clover sward is grazed.
  • Effects of multi-species swards on dry matter production and the incidence of unsown species at three Irish sites

    Connolly, J.; Finn, John A.; Black, Alistair D; Kirwan, L.; Brophy, C.; Luscher, A. (Teagasc (Agriculture and Food Development Authority), Ireland, 2009)
    Recent ecological research provides evidence that an increased number of plant species in natural grasslands is associated with increased biomass productivity, and provides a wide range of other ecosystem benefits. This suggests that increases in species diversity in agricultural ecosystems may similarly lead to increased benefits. The work reported below was part of the COST 852 Agrodiversity experiment, carried out at 34 sites across Europe. In Ireland, the effects of four-species grass-clover mixtures on herbage production, species persistence and unsown species suppression at three sites over multiple years, were investigated under growing conditions that were intensive relative to unfertilised natural grassland systems. The design included a range of four-species mixtures and monocultures of perennial ryegrass, timothy, cocksfoot, white clover, red clover and Caucasian clover. Several harvests were taken at each site for two or three years. Species diversity had a strong, persistent and positive effect on overall yield and the yield of sown species, and enhanced resistance to the growth of unsown species. Mixtures generally yielded well when compared with the best monoculture, and sometimes out yielded it. These effects on total yield declined over time but were still important at the end of the experiments. The diversity effects on sown species yield and on resistance to unsown species increased with time. Diversity effects were robust to changes in species composition, and persisted for the duration of the experiments across mixtures and over time. Virtually every mixture had a higher yield, and suppressed unsown species better, than monocultures of perennial ryegrass. These patterns were broadly consistent across sites. The persistence of species varied widely and was not consistent across sites.
  • Optimal system of contract matings for use in a commercial dairy population

    McParland, Sinead; Kearney, K. F.; Lopez-Villalobos, N.; Berry, Donagh P. (Teagasc (Agriculture and Food Development Authority), Ireland, 2009)
    Managing the contribution of prominent animals to the pedigree of livestock populations is a topic of increasing importance worldwide. The aim of this study was to evaluate methods of controlling the accumulation of inbreeding in the Irish Holstein-Friesian population through the methodology used to arrange contract matings. Two non-random mating systems were investigated, linear programming (LP) and sequential programming (SEQ); these were compared with random mating (RAN) and mating of the best sires to the best dams (TOP). All mating systems were compared across a range of objectives: to maximise genetic merit for the economic breeding index (EBI) used in Ireland, to minimise population coancestry with breeding females (R-value), and a dual objective of simultaneously maximising EBI and minimising coancestry with breeding females. Algorithms were developed to identify elite dams and sires from the national herd for use in the contract mating programme. One thousand contract matings were generated using each selection method, with the aim of producing 83 test sires (the number of bulls which it is feasible to test annually in Ireland) for use in a progeny testing scheme. The top 1,000 matings, as selected by the LP and SEQ methods, performed similarly when maximising the dual objective (average progeny EBI of €145 and an average coancestry of the progeny to the population of breeding females of 0.93%). The TOP and RAN methods both selected phantom progeny with higher coancestry with the breeding female population (1.21% and 1.34%, respectively) than the LP and SEQ methods. However the matings from the TOP method generated progeny of higher genetic merit (EBI = €199), whilst the progeny generated from the RAN method had lower genetic merit (EBI = €127) than those selected by the LP or SEQ methods.