Health planning

In the UK, health planning is compulsory for farmers wishing to obtain organic certification. The focus of ‘positive health’ is to devise health plans that actively promote health rather than relying on chemical prophylaxis to support bad management or exploitive farming practices (Hovi et al., Reference Hovi, Douglas, Vaarst, Andreas, Walkenhorst and Roderick2004). An analysis of the key principles of health and welfare plans and planning and details of how health and welfare plans are promoted and implemented by British governments, industry quality assurance and organic certification bodies has been covered in a recent review (Nicholas and Jasinska, Reference Nicholas and Jasinska2008). This review highlighted that whilst farmers often undertake health planning to prevent or reduce disease problems, many farmers regarded health plans as a paper exercise that are more for the benefit of others. As proposed by Nicholas and Jasinska (Reference Nicholas and Jasinska2008), a simplified health plan may be a way to implement and encourage the practical application of health plans as part of a whole farm management plan on both conventional and organic farms. The main principles of animal health and welfare planning identified included, for example: to identify the current disease status, ensure bio-security, monitor health data records, to obtain veterinary involvement, to aim to reduce the use of veterinary medicine, to explicitly address animal welfare, to encourage the use of preventative management and to make health plans available to all staff working with livestock.

Calving pattern

The organic principles and standards advocate that, where possible, cows should calve outdoors. While this allows the cow to calve in a more natural environment, there are potential implications on health and welfare when calving in different seasons. When a herd calves throughout the year, the question needs to be asked as to whether this was the result of a management decision or problems associated with the health of the herd. In the latter case, failure to achieve a good reproductive performance may be due to lower standards of husbandry, poor quality diets, the incidence of a specific disease affecting fertility in the herd (e.g. bovine viral diarrhoea) or the poor genetic merit of the cow or bull. A spring-calving pattern provides optimal forage quality for high-yielding cows. However, cows may be vulnerable to the effects of unpredictable weather conditions during the spring leading to a more erratic pattern of daily dry matter (DM) intakes and an increased risk of a high negative energy balance leading to metabolic disorders, particularly ketosis (Olesen et al., Reference Olesen, Lindhardt and Ebbesvik1999). Many dairy farmers calve their cows in the autumn period, resulting in most of the milk being produced from silage-based diets. Although the quality of silage is generally lower than grazed herbage, feed intakes are usually easier to monitor. Critical factors in the management and maintenance of good health are the conservation of high-quality silage and achieving high feed intakes. Poor quality forage not only has a low feed value but results in low DM intakes, increasing the risk of metabolic disorders (as reviewed by Driehuis and Elferink, Reference Driehuis and Elferink2000). There is also a risk of infertility problems due to poorer heat detection during the days when both the daylight hours and temperatures are lower, as the oestrus period may only last for only 10 to 12 h (ADAS, 1987).

Summer mastitis (mainly caused by Actinomyces pyogenes (previously Corynebacterium pyogenes) and Streptococcus dysgalactiae pathogens) is a risk for herds with an autumn or a year-round calving pattern as the timing of the dry period has an influence on the incidence of mastitis during lactation (Cousins et al., Reference Cousins, Higgs, Jackson, Neave and Dodd1980; Roberson et al., Reference Roberson, Fox, Hancock, Gay and Besser1994). The incidence of this type of mastitis rises dramatically during July to September, as flies cluster around the teat orifice causing considerable irritation (Blowey and Edmondson, Reference Blowey and Edmondson1995). This type of mastitis is painful with cows suffering from a high temperature, stiff hocks and lameness and also leads to permanent udder damage, the risk of increased culling and financial loss. Smith et al. (Reference Smith, Todhunter and Schoenberger1985) reported that 50% of mastitis cases during early lactation were attributable to intra-mammary infections that occurred pre-calving. In organic herds where the routine use of long-acting antibiotics is prohibited, the risk of subsequent infections in the lactation is increased. Avoiding the grazing of fields that are adjacent to habitats frequented by flies and the use of teat sealants is essential (Klocke et al., Reference Klocke, Ivemeyer, Walkenhorst, Maeschli and Heil2006) to minimise the problem in organic herds.

Calf management

The principles of organic farming encourage dairy farmers to rear calves under a system that is as close to ‘natural living’ as possible. Under natural conditions, mothers would leave calves in a group from about 2 weeks of age, whilst they graze nearby (Webster, Reference Webster1994) and weaning would be introduced gradually at approximately 6 to 8 months (Phillips, Reference Phillips1993). The main welfare implications for rearing calves under current dairy practice, some of which apply to both conventional and organic dairy systems, are: isolation from their mothers and conspecifics, reduced space allowances, barren unnatural environments and poorer nutrition as diets are based on reconstituted milk (Broom, Reference Broom1991; Le Neindre, Reference Le Neindre1993). Whilst the organic standards within some individual EU countries do, the current EU organic standards do not state a requirement or provide guidance on the best time to separate dairy calves from their mothers despite the potential impact of this factor on both the short-term and the long-term performance, health and welfare of both animals. Most organic dairy farmers, like conventional farmers, remove calves from their mothers within the first day of life. In some countries, for example, on some farms in Finland, calves are allowed to remain with their mothers until 3 or even 11 weeks old. It has been shown that short-term suckling can have benefits in terms of performance, udder health and the behaviour of both calf and cow when compared with systems separating calves from their mothers immediately after birth (as reviewed by Krohn, Reference Krohn2001). More recent studies support this evidence as restricted suckling (30 min twice daily) reduced abnormal sucking behaviour and increased live-weight gain in calves and increased milk yield, influenced milk composition and improved udder health in cows (Froberg et al., Reference Froberg, Aspegren-Guldorff, Olsson, Marin, Berg, Hernandez, Galina, Lidfors and Svennersten-Sjaunja2007; Wagenaar and Langhout, Reference Wagenaar and Langhout2007). Barriers to the introduction of natural suckling systems include the weaning stress when cow and calf are separated after 3 weeks and the loss of marketable milk. Another option is the use of nurse cows, where calves are introduced to a foster cow and is able to be reared alongside two to three other calves. Research indicates that these multiple suckling systems were less stressful than single suckling systems for rearing dairy replacements as weaning could be more gradually introduced (Wagenaar and Langhout, Reference Wagenaar and Langhout2007). Farmers need to be encouraged to accommodate an attitude change to the use of these novel rearing systems within organic herds, and standards could recommend their consideration as pressures increase from consumers to provide ‘natural’ rearing systems.

Organic standards require that calves are not weaned before they are 12 weeks old. In some instances, calves with a high birth weight or achieving a high daily live-weight gain may reach a live weight of over 100 kg, the weight at which calves are typically weaned in conventional systems, earlier than 12 weeks old. Restricting the weaning time to a specific age rather than to either a specific weight or age, may mean that animals kept under optimal management systems may be ready to be weaned (and require more forage and concentrates than is provided) earlier than 12 weeks. Whilst it is recognised that good welfare is not merely evident from a good production response, research comparing early weaning (3 to 7 weeks) showed no effect of weaning age on daily intakes or live-weight gain in dairy calves (Winter, Reference Winter1985; Kehoe et al., Reference Kehoe, Dechow and Heinrichs2007), indicating that early weaning was not detrimental to calf development, at least in the early stages. However, the effects of early weaning on the development, health and longevity of a dairy cow needs to be considered if we are to achieve the full aspirations of organic dairy systems. Typically, information on rearing dairy calves is extrapolated from studies into beef cattle and is therefore based on short-term economic considerations rather than the long-term productivity of dairy heifers. Research into the lifetime performance effects of different heifer rearing systems is needed to determine the best approach for weaning both conventional and organic livestock.

Farming systems

Self-sufficient dairy systems aim to maximise the utilisation of (home-grown) forage in the diet and feed a reduced quantity of purchased concentrate feeds. As a result, many herds in self-sufficient systems fed above the minimum 60% forage in the total diet required by the organic standards, even during the early-lactation period. A key factor in their success is the provision of high-quality forage for grazing and conservation. The total quantity of concentrate feeds (cereal grains, pulses) that can be produced on the self-sufficient organic farm determines the quantity available for feeding per cow and on most farms this quantity is too restricted. In general, these systems are more challenging to manage in relation to herd health and welfare standards, as there is less flexibility to balance diet, health and herd performance. Extended grazing within self-sufficient systems may increase the exposure of livestock to gastro-intestinal parasites, which may increase the incidence of parasitic infections (Ruest, Reference Ruest2002) unless a successful rotational grazing system is employed (Larsson et al., Reference Larsson, Dimander, Rydzik, Uggla, Waller and Hoglund2006). The incidence of lameness has been found to be lower in some herds using self-sufficient systems when compared with more intensive systems (Weller and Bowling, Reference Weller and Bowling1999). This may be due to high-fibre forage diets reducing acidosis and laminitis due to improved rumen stability, although the neutral detergent fibre (NDF) concentration in pasture-based diets may need to be higher than 30% to achieve this (Lean et al., Reference Lean, Westwood and Playford2008). This factor also depends on the DM of the forage as studies have shown that diets with a DM below 25% led to an increased number of heifers with both white line and sole lesions (Offer et al., Reference Offer, Fisher, Kempson and Logue2001 and Reference Offer, Leach, Brocklehurst and Logue2003). Therefore, the DM content of the forage in the total diet is as critical in organic systems as the proportion of concentrates in the diet of conventionally fed dairy herds. Haskell et al. (Reference Haskell, Rutherford, Langford, Sherwood, Jack, Maggs, Athanasiadou, Wemelsfelder and Lawrence2007) reported similar levels of metabolic disorders in conventional and organic herds; however, the incidence of these disorders, such as ketosis, may increase when systems aim for self-sufficiency (Vaarst et al., Reference Vaarst, Roderick, Lund, Lockeretz and Hovi2004; Weller, Reference Weller2006). However, research has also found that changing to self-sufficiency on unsuitable farms can increase the risk of poor animal welfare because of nutritional deficiencies. Other studies suggest that the incidence of clinical ketosis is generally lower in organic herds compared to conventional herds (Vaarst and Enevoldsen, 1994; Krutzinna et al., Reference Krutzinna, Boehncke and Hermann1996) despite the potentially high risk of problems because of the limitation on the quantity of high-energy feeds (i.e. concentrates) in the total diet. These findings may have been due to differences in the breeds compared between organic and conventional systems (Hörning, Reference Hörning2006). However, Kjeldsen et al. (Reference Kjeldsen, Thøgersen and Enemark1999) showed that the lower milk production in organic herds could be explained by a lower level of feeding as there was no difference in the genetic potential between organic and conventional herds.

Organic dairy farmers managing a purchased-feed system feed a higher quantity of concentrates in the diet (Weller, Reference Weller2006), with many purchasing all the concentrate feeds to allow a higher stocking rate (1.5 to 1.7 cows/ha) and maximise milk output per hectare. In these systems, there is the opportunity to adjust the type and quality of the individual concentrate feeds purchased to meet changes in the energy and protein concentrations of both the conserved and grazed forages. This option is particularly useful during seasons when climatic conditions have led to forages being harvested at below optimal quality and offers the opportunity to balance diets and prevent nutritional deficiencies. This type of system may also ensure that the reproductive performance of the dairy herd is satisfactory, avoiding the need to raise extra replacements due to infertility problems in the herd (Weller, Reference Weller2006). By avoiding the risk of metabolic disorders, the system also reduces the risk of predisposing cows to other problems. However, while purchasing concentrate feeds has these benefits for the health status of the herd, feeding a higher level of concentrate feeding may lead to an increased risk of acidosis, depending on the method of feeding and quantity of starch in the concentrates. If complete diets (total mixed rations) are fed, then the rumen pH will remain relatively constant. However, if the concentrates are fed only twice daily, there is a potential risk of significant fluctuations in the rumen pH and the risk of acidosis, due to the excessive production of lactic acid that is absorbed into the blood stream that then leads to reduced blood supply to the foot and lameness problems (Chamberlain and Wilkinson, Reference Chamberlain and Wilkinson1996; MDC, 1997).

Access to pasture

The organic principles and aspirations aim for organic dairy systems to be managed as a ‘natural system’. The increasing costs of production are leading many farmers to consider the merits of keeping cattle outside for a greater proportion of the year (e.g. extended grazing systems) or out-wintering non-lactating cattle for the whole winter period (e.g. brassica-based systems). Whilst these grazing systems offer benefits in reducing production costs, there are implications for the health and welfare of the cattle, including the hardiness and suitability of dairy breeds. These systems require additional labour input to ensure that grazing areas are managed effectively and animal health and welfare are not compromised. Factors requiring consideration include: the provision of suitable shelter to ensure that livestock are protected from exposure to extremes of temperature and avoidance of over-poaching of the ground. The latter can increase dirtiness around the udder and cause subsequent infections (Christiansson et al., Reference Christiansson, Nilsson and Bertilsson1996).

Cattle will acclimatise to colder weather by growing longer, thicker coats with reduced hair shedding to provide better insulation against lower temperatures, but the coat must be clean and dry to allow protection to the cow (Webster et al., Reference Webster, Chlumecky and Young1970; Brick, Reference Brick1998; Tarr, Reference Tarr2006). While UK winters are not normally associated with extreme cold, temperature per se is not an accurate measurement in relation to the response and hardiness of cattle out-wintered, as the accumulated effect of the wind chill factor, rainfall and state of the ground all increase the loss of body heat from the cow. In two reviews, Johnson and Vanjonack (Reference Johnson and Vanjonack1976) and Sharma et al. (Reference Sharma, Rodriguez, Wilcox, Collier, Bachman and Martin1988) reported that to maintain good health the ‘comfort zone’ for dairy cows was temperatures between 2°C and 22°C. Beef cattle are frequently out-wintered and are more adaptable to changes in climatic conditions compared with dairy breeds, due to their higher body condition scores and thermal insulation (Webster et al., Reference Webster, Chlumecky and Young1970; Wright and Russel, Reference Wright and Russel1984). Conversely, high summer temperatures and heat stress in UK dairy herds results in reduced fertility and financial loss (Farm Animal Welfare Council (FAWC), 1997), with Holstein cows being found to be less tolerant of high temperatures than Jersey cows (Bakke, Reference Bakke2003). As the target conception date for many organic dairy herds occurs during the periods of warmer weather, heat stress needs to be considered when implementing a strategy to improve cow welfare.

Housing

The majority of organic herds are housed during the winter period in either cubicle housing or straw-bedded yards. A failure to ensure that the cubicles are suitable for the herd will increase the risk of injury, including teat damage, as large cows using cubicles of an inadequate size will have difficulty when lying, entering and rising (Blowey, Reference Blowey1994). In addition to the design of the cubicles, the cleanliness of the passage ways and loafing areas is also important as the build-up of slurry will lead to lameness problems, such as digital dermatitis, requiring the use of antibiotics to achieve effective control (Roderick and Hovi, Reference Roderick and Hovi1999; Laven and Lawrence, Reference Laven and Lawrence2006). While organic standards state the minimal space required per animal, depending on breed and age, the relationship between stocking density and the frequency of bedding renewal and cleanliness is of equal importance. The risk of injury can be influenced by the type of bedding (Livesey et al., Reference Livesey, Marsh, Metcalf and Laven2002), with straw, sawdust, paper, mats, mattresses and sand being recommended within organic standards. Compared with loose housing in straw-bedded yards, the incidence of lameness and leg damage was shown to be higher in cows housed in cubicle sheds (Rowlands et al., Reference Rowlands, Russell and Williams1983; FAWC, 1997; Haskell et al., Reference Haskell, Rutherford, Langford, Sherwood, Jack, Maggs, Athanasiadou, Wemelsfelder and Lawrence2007). However, straw-bedded yards provide an ideal environment for pathogens. If straw moisture content is too high, a rapid increase in the temperature of the bedding and an increased risk of Escherichia coli and Streptococcus uberis infections can result (Ward et al., Reference Ward, Hughes, Faull, Cripps, Sutherland and Sutherst2002). The risk of mastitis from environmental pathogens has been found to be higher in straw-bedded yards compared with cubicle sheds although there are large variations between farms, with lower SCC recorded when clean straw is provided (Krutzinna et al., Reference Krutzinna, Boehncke and Hermann1996; FAWC, 1997; Weller and Bowling, Reference Weller and Bowling2000).

Husbandry and stockmanship

Undesirable handling, transport conditions and stockmanship can have negative consequences for livestock, farmers and consumers as it can seriously damage the welfare, productivity, product quality and profitability of farm animals (as reviewed by Hemsworth and Coleman, Reference Hemsworth and Coleman1998; Maller et al., Reference Maller, Hemsworth, Ng, Jongman, Coleman and Arnold2005; Hemsworth, Reference Hemsworth2007). Negative interactions with humans are associated with reduced milk let-down and subsequently milk yield in dairy cows (Rushen et al., Reference Rushen, De Passille and Munksgaard1999; Breuer et al., Reference Breuer, Hemsworth, Barnett, Matthews and Coleman2000; Waiblinger et al., Reference Waiblinger, Menke and Coleman2002). Chronic and acute stress responses, traumatic incidents, injuries and death are also more prevalent in cows, heifers and calves that have been incorrectly handled (Breuer et al., Reference Breuer, Hemsworth and Coleman2003). The standards for organic production cover the necessity to satisfy the needs of animals by handling and transporting them with due care to ensure freedom from fear and distress and stipulate strict welfare standards regarding the rights of animals to enjoy freedom from fear and distress. It is envisaged that with the tendency towards a higher number of animals per stockperson, the impact of correct stockmanship will become increasingly important as dairy cow herd sizes continue to increase within the industry. In light of this, the standards may need to recommend the number of animals per stockperson for organic dairy systems and to state that all stockpersons should be suitably trained to better meet the principles of organic farming and ensure that a high level of animal health and welfare is maintained.

The principles of organic systems may not be conducive to the use of automated (robotic) milking parlours as compared with the recommended application of excellent husbandry skills and good stockperson to animal relationships. Potential implications for the health and welfare of dairy cows kept in automated milking systems include increased risks of failure for clusters to attach to teats correctly (Miller et al., Reference Miller, Fulton, Erez, Williams and Pearson1995), although Vliegher De et al. (Reference Vliegher De, Laevens, Barkema, Opsomer, Hemling and Kruif De2003) found no significant difference between conventional and automated milking on teat skin and teat end condition. The risk of health problems going undetected in an automated milking system needs careful consideration. On the one hand, automated systems may improve the detection of sub-clinical problems, such as the combined use of automated milking with an automated lameness detection system (Pastell and Kujala, Reference Pastell and Kujala2007) or an online detection system for sub-clinical mastitis (Nielen et al., Reference Nielen, Spigt, Schukken, Deluyker, Maatje and Brand1995; Hovinen et al., Reference Hovinen, Aisla and Pyörälä2006). Alternatively, an atypical health or disease problem, or an injury that would be easily observed by a stockperson, may go undetected for a longer period in an automated system. Guidelines on the use of automated systems and the requirement for good stockmanship in these systems are needed to avoid risks to dairy cow health and welfare.

Dehorning

The principles of organic farming do not support the use of mutilations, such as disbudding or dehorning, to support intensive farming methods. The dilemma with regards to dehorning is whether the horn itself is a potential health and welfare risk or whether it is regarded as an integral part of the animal, required to allow an animal to express its innate social behaviour (Menke et al., Reference Menke, Waiblinger, Studnitz and Bestman2003). Certainly, the process of dehorning is a source of stress and pain in the animal (Stafford and Mellor, Reference Stafford and Mellor2005; Mounier et al., Reference Mounier, Marie and Lensink2007), particularly if performed without anaesthesia or analgesia (Hewson et al., Reference Hewson, Dohoo, Lemke and Barkemaet2007). In practice, in the UK, disbudding with a hot iron is preferred to dehorning and it is advised that this should be performed before cattle reach the age of 2 months (FAWC, 2006). Organic standards do not permit the disbudding of calves after 3 months of age. It has been shown that the application of caustic paste is acceptable in cattle up to 7 days old (Stafford and Mellor, Reference Stafford and Mellor2005) but anaesthesia is required if cattle are dehorned after this period (Faulkner and Weary, Reference Faulkner and Weary2000). Vickers et al. (Reference Vickers, Niel, Kiehlbauch and Weary2005) showed that dehorning with caustic paste, combined with a sedative, resulted in less pain to calves than dehorning with a hot iron combined with a sedative and a local anaesthetic. Recommendations for the best practice to reduce pain and distress when disbudding calves should be part of the organic standards. One route to avoid this problem completely would be the breeding of polled dairy animals. Polledness is a dominant autosomal genetic trait (Stookey and Goonewardene, Reference Stookey and Goonewardene1996) that appears in all offspring of homozygous polled bulls. There are no performance restriction as polled genes are not linked to production or behavioural traits (Goonewardene et al., Reference Goonewardene, Price, Okine and Berg1999). There is large scope to undertake new research programs to develop DNA tests that identify homozygous/heterozygous animals for poll genes that would assist faster introgression of the polled condition into beef cattle populations (Prayaga, Reference Prayaga2007). Similar approaches, such as microsatellite mapping of poll genes (Georges et al., Reference Georges, Drinkwater, King, Mishra, Moore, Nielsen, Sargeant, Sorensen, Steele, Zhao, Womack and Hetzel1993), could be applied to the dairy breeds, but further work may be required with dairy bulls as polled sires are rare in many breeds, including Holstein (approximately 1%).

Yield potential

The type of cow and her genetic merit in relation to milk yield, disease resistance and fertility of cows are key factors in meeting the health and welfare standards required by both the standards for organic milk production and the criteria defined to meet the quality assurance standards of milk production. Correct breeding and selection of appropriate dairy breeds should be viewed as a preventative health strategy for organic dairy systems. Breeding cattle with a good, lifetime milk yield, rather than the short-term high-yielding traits that have previously been selected, may help to fulfil the aspirations of organic dairy production. The trend for high percentages of dairy cows to fail to reach their third lactation is an unacceptable loss for both conventional and organic dairy systems, with the average UK annual culling rate in the dairy industry at approximately 29% (MDC, 1999). Klenke (Reference Klenke1989) studied conventional and organic herds in Germany and found little evidence that longevity is significantly higher in organic herds (average 5.85 and 5.43 years for organic and conventional, respectively), although Krutzinna et al. (Reference Krutzinna, Boehncke and Hermann1996) found that the longer a farm had been in organic management, the longer the productive life span of the dairy cows (as reviewed by Boehncke, Reference Boehncke1997). Whilst economic factors drive many dairy systems and put stresses on modern-day dairy cows, a true cost of the requirement to replace cows within less than three lactations needs due consideration. More recently in the UK, dairy cows selection traits have reduced the emphasis on production rates (to 45%) and increased the emphasis on health, welfare and fitness traits, reflecting both the farming industry and wider consumer demand to strive for higher animal welfare standards, as well as the impact of these traits on profitability (Sandøe et al., Reference Sandøe, Nielsen, Christensen and Sorensen1999).

Within the UK, and some European countries, organic milk production has been dominated by breeds selected for intensive systems where a high proportion of concentrates are fed in the diet. Currently, Holstein–Friesian breed of high genetic merit contributes more than 92% of the UK’s dairy cow population (Moorby et al., Reference Moorby, Esslemont and Jones2003). Walsh et al. (Reference Walsh, Buckley, Pierce, Byrne, Patton and Dillon2008) reported a negative genetic correlation between increasing milk yield and the incidence of health and fertility traits with Holstein–Friesian herds. While the Holstein–Friesian produces higher milk yields compared with breeds of a lower genetic merit, this has not been accompanied by an increase in feed intake. This has led to an increased risk of negative energy balance, metabolic stress due to abnormal physiological function and other problems (Veerkamp et al., Reference Veerkamp, Simm and Oldham1995; Nielsen, Reference Nielsen1999; Weller and Bowling, Reference Weller and Bowling2004). While the breed is predominant in organic herds, other more traditional breeds (e.g. Ayrshire, Jersey and Shorthorn) and crossbreds also contribute to organic milk production in the UK. In other countries, traditional breeds are selected for organic systems. For example, in Switzerland, breeding programmes have (with Brown Swiss, and Swiss Red and White breeds) improved the compatibility between genetics and the system of management (Bapst, Reference Bapst2001).

Disease resistance

Genetics can greatly affect the incidence of three main health and welfare problems in dairy cows: lameness, mastitis and infertility. The incidence of lameness in organic herds may be influenced by breed, with Holstein–Friesian cows appearing to be more prone to lameness either due to their white hooves compared with breeds with black hooves (Peterse, Reference Peterse1985; Webster, Reference Webster1993; Roderick and Hovi, Reference Roderick and Hovi1999) or heavier bodyweight when compared with lighter breeds (e.g. Ayrshire, Guernsey and Jersey) (Radostits and Blood, Reference Radostits and Blood1985). Bakke (Reference Bakke2003) reported that Jerseys, Norwegian Reds and Swedish Red breeds are more prone to milk fever. The critical balance between genetic merit and fertility problems was found by Snijders et al. (Reference Snijders, Dillon, Sreenan, Diskin, O’Callaghan, Boland and O’Farrell1997) who found a higher incidence of failure to conceive and more cows culled for infertility in high genetic merit cows. For cows with high milk-yield potential, failure to meet their optimal nutrient requirements resulting in either clinical or sub-clinical health problems has to be recognised as a welfare problem. A main factor to consider in the aim of minimising disease problems is heterosis or hybrid vigour. Brotherstone et al. (Reference Brotherstone, Santarossa, Simm, Coffey and Stott2003) reported the positive benefits of cross-breeding on SCC in milk. The recent inclusion of health traits in the classification of bull breeding programmes should help to improve the health status of both conventional and organic dairy herds in the UK. If future organic standards included thresholds on acceptable levels for specific health ailments, the selection of suitable breeds and types within individual breeds could have a greater influence on the management of organic dairy systems.

Longevity

Longevity is a factor in dairy herds that has both benefits and disadvantages. Benefits include improved welfare standards associated with the cow having a longer productive life, while the disadvantages include the lower immunity and higher risk of disease occurrence with older cows. It is also generally considered by farmers that younger cows have a superior genetic merit. Optimal age limit lifetime efficiency is achieved by cows with a productive life of six lactations (Webster, Reference Webster2000; Moorby et al., Reference Moorby, Esslemont and Jones2003). However, the major change in the last 30 years has been to select cows for higher milk yields, including changing the type of cow that is managed in different dairy systems from Friesians and other breeds to the Holstein, leading to a decline, in the last 30 years, of the average herd life of a cow from 4.76 to 3.44 lactations (Moorby et al., Reference Moorby, Esslemont and Jones2003). The issue in many European organic dairy systems is to ensure a high average milk yield, leading to the culling of a high number of low-yielding animals during their first lactation. This point is clearly illustrated in the results of a study of organic dairy herds in Denmark where the average annual culling rate from herds was found to be 40% (Kristensen and Pedersen, Reference Kristensen and Pedersen2001). Low culling rates and the maintenance of herds with three or more lactations lead to more efficient systems, with lower culling rates and a better ratio of productive to non-productive cattle. However, older cows have been found to have markedly higher SCC in their milk compared with younger cows (Weller and Davies, Reference Weller and Davies1998), indicating a higher level of sub-clinical mastitis due, in many cases, to Staphylococcus aureus, which can be easily transmitted between cows. Therefore, in some herds, older cows are culled to reduce the average SCC and to gain a maximum price for the milk. Problems with older cows that increase the risk of mastitis infections include the reducing udder support and increasing problem of pendulous udders and also the increased teat size and more relaxed sphincter muscles in many cows (Seykora and McDaniel, Reference Seykora and McDaniel1985). This demonstrates that whilst longevity has welfare benefits, in relation to herd health it may have detrimental effects.

Balancing energy and protein

For organic farmers, the introduction (as from 1 January 2008 in the UK) of standards requiring all ruminant diets to be 100% organic, will increase pressure to use home-grown feed. Using forage compositional analyses are essential to ensure that the nutritional requirements of dairy cows are met. Organic dairy systems are often referred to as high forage–low input systems and have the advantages of allowing animals to have access to pasture and a minimum of 60% of DM intake to be fed as forage. Based on organic principles, livestock diets should be in a form that allows an animal to carry out its natural feeding behaviour and meet their digestive needs and should also provide for high-quality products rather than maximising output. However, failure to maintain the correct energy-to-protein balance in the diet, resulting in the intake of excess protein, affects the fertility of the dairy cow, as discussed later in this section. High-protein diets may also cause peri-parturient problems including retained placenta, metritis and ovarian cysts (Barton et al., Reference Barton, Rosario, Anderson, Grindle and Carroll1996), an increase in the number of services/conception and impaired embryo survival (Chamberlain and Wilkinson, Reference Chamberlain and Wilkinson1996). Organic spring-calving herds often use grass/white clover pastures, including grazing both re-seeded leys and permanent pastures for grazing. By early July, forage protein is above the cow’s nutrient requirements and can reach 25% by the autumn, leading to poor protein utilisation by the cow and the risk of fertility problems (Weller and Cooper, Reference Weller and Cooper2001). When herbage supply is plentiful, a preference for clover rather than grass further increases protein intake. For a high-yielding cow receiving a concentrate supplement that has a high-energy/low-protein value, the diet will be balanced, but for cows not being fed concentrates the protein content of the diet may be too high. These risks should be considered when non-pregnant cows graze protein-rich swards of either fertilised ryegrass or grass/clover mixtures and do not receive a high-energy feed. Grazing swards with a high (greater than 19%) crude protein concentration can reduce reproductive efficiency and increase lameness compared with diets of 16% (Butler et al., Reference Butler, Calaman and Beam1996; Manson and Leaver, Reference Manson and Leaver1988). Measuring the milk urea concentrations is a useful indicator of excess dietary protein, and energy-to-protein imbalance that could be readily implemented on farms. To overcome this inefficient balance of dietary nutrients, increasing the amount of energy provided in the form of concentrates (Dewhurst et al., Reference Dewhurst, Fisher, Tweed and Wilkins2003) is not conducive to the principles of organic farming. Alternative, and more ‘natural’ approaches, may include the use of ryegrass that has been bred to express high water-soluble carbohydrate concentrations (Lee et al., Reference Lee, Jones, Moorby, Humphries, Theodorou, MacRae and Scollan2001; Marley et al., Reference Marley, Fraser, Fisher, Forbes, Jones, Moorby, MacRae and Theodorou2007a) or feeding alternative high-energy forages, such as forage brassicas, which have been shown to improve voluntary intake and N utilisation in ruminants (Marley et al., Reference Marley, Fychan, Fraser, Sanderson and Jones2007b).

Providing a nutritionally balanced diet to organic dairy herds during early lactation is essential to minimise the risk of metabolic disorders associated with underfeeding, such as ketosis. A lack of energy during the early-lactation period is a critical factor in many dairy systems (Roepstad et al., Reference Roepstad, Larsen and Refsdal1989; Heur et al., Reference Heur, Van Straalen, Schukken, Dirkzwager and Noordhuizen2000) and in high-forage organic systems the risk of problems is greater due to the lower energy density of the diets (Knaus et al., Reference Knaus, Steinwidder and Zollitsch2001). A failure to feed balanced diets to organic dairy cows may lead to both clinical and sub-clinical problems, including metabolic disorders (Vaarst and Enevoldsen, Reference Vaarst and Enevoldsen1994; Weller and Bowling, Reference Weller and Bowling2004). Low-energy diets can also increase the number of days from calving to conception due to reduced body condition (Pollott and Coffey, Reference Pollott and Coffey2008), reducing the pregnancy rate (Sehested et al., Reference Sehested, Kristensen and Soegaard2003; Weller and Bowling, Reference Weller and Bowling2004) and increasing the risk of cystic ovaries (Hooijer et al., Reference Hooijer, Oijen, Frankena and Noordhuizen2003). Reksen et al. (Reference Reksen, Tverdal and Ropstad1999) also found that the required feeding of high-forage organic diets reduced herd fertility during the winter months due to the energy level of silage-based diets being lower than grazed herbage. Sub-clinical ketosis is likely to go undetected unless regular milk samples from the individual cows in the herd are analysed to identify any imbalance in the ratio of milk constituents or the level of ketone bodies that indicate a problem (Weber et al., Reference Weber, Pabst, Schulte-Coerne, Westphal and Gravert1993; Heur et al., Reference Heur, Van Straalen, Schukken, Dirkzwager and Noordhuizen2000). Baker (Reference Baker1980) and Mayne et al. (Reference Mayne, Newberry and Woodcosk1988) showed that implementing a leader/follower grazing system (where high-yielding cows are placed in the leader group and have access to grazing areas one day ahead of a lower-yielding follower group) can reduce the risk of metabolic disorders common in high-yielding cows during early lactation.

Minerals and trace elements

Milk is an excellent source of calcium, phosphorous, riboflavin (vitamin B2), thiamine (vitamin B1) and vitamin B12 and a valuable source of folate, niacin, magnesium and zinc in human diets (Food Standards Agency (FSA), 2002). The removal of milk from a farm potentially results in a net flow of these elements from the site, which either needs to be replaced in the form of fertilisers or in feed. A principle of organic systems is to reduce reliance on external inputs, including mineral, trace element and vitamin supplementation. Ideally, the mineral and trace element status of the farm and livestock should be determined and appropriate measures should be taken to avoid emergency remediation. The aim of the standards is to prevent the use of these supplements so as to stimulate production rather than maintain health. The standards allow the use of straight mineral and trace element additives without prior permission provided that justification, such as forage or soil or blood analysis, can demonstrate a deficiency. Potentially, novel management practices, such as using different forages may be a more sustainable option to ensure that these nutrients are made bio-available to the dairy cow. Chemical analysis of certain forages, for example chicory (Cichorium intybus), has received attention due to its higher trace element content (Clark, Reference Clark1995), with preliminary results from grazing trials indicating that, in comparison to ryegrass, chicory significantly increased the copper, cobalt (vitamin B₁₂) and selenium status of grazing ruminants (Marley, Reference Marley2001). Organic systems aim to increase the diversity in the pasture species in grazing swards, and using specific forage species to improve the mineral and trace element status would be closely aligned with organic principles. The risk of hypomagnesaemia occurring during the spring period, when cows graze lush grass swards grown with high inputs of nitrogen and potash fertiliser, is a problem in many conventionally managed herds. However, in organic systems where the primary N input for crop production is white clover, the incidence of hypomagnesaemia has been found to be lower (Weller and Bowling, Reference Weller and Bowling2000) and may be attributed to lower N inputs and the higher magnesium concentration of white clover compared with the levels found in grass. The same may be true for other minerals, trace elements and vitamins. However, there have been few studies into the effects of different pasture species on the mineral and trace element status of organic dairy cows and into the long-term sustainability of this approach to prevent deficiencies.

Effects of herd size and hierarchy on health and welfare

Organic principles require that animals are allowed to express their innate behaviour to meet their psychological and physiological needs. As dairy cows are naturally a herd animal, social behaviour can greatly influence the health and well-being of an individual cow. In the wild, bovines would form strong relationships with members of their herd and develop a natural hierarchy. In extensively farmed cows (i.e. beef), the social bond of cow and calf is life-long for female offspring, whereas for most males, it lasts until they leave the herd (either 10 or 18 months) (e.g. Napolitano et al., Reference Napolitano, Pacelli, De Rosa, Braghieri and Girolami2005). Whilst domestic dairy cows do have some opportunities to develop strong bonds within the herd, given the short longevity and subsequent high turn-over of animals within the herd, the development of a natural herd structure within modern dairy herds may be compromised. Organic principles encourage the use of a closed herd and breeding replacements. This principle offers an opportunity to integrate animals to overcome the socially compromised modern day dairy cow. First-calf heifers and recently introduced cows are often submissive and larger cows, older cows and cows with more seniority in a group are often more dominant (Harb et al., Reference Harb, Reynolds and Campling1985). To overcome any restrictions resulting from the lack of a natural and secure herd hierarchy, handling and housing facilities should be fit for purpose and the size of the herd (Petherick and Phillips, Reference Petherick and Phillips2009). Limited space is a main reason for aggression among cows (Miller and Woodgush, Reference Miller and Woodgush1991) and the design of housing, feeding troughs and access to water should be modified to prevent submissive cows from being unable to meet their needs. Social problems usually occur at housing but also occur at grazing when fields are strip-grazed rather than set-stocked or rotationally grazed. Social hierarchy may alter the time of feeding, time spent lying down, access to water and the time spent ruminating by an individual animal, as dominant cows inhibit the activities of submissive cows (Proudfoot et al., Reference Proudfoot, Veira, Weary and von Keyserlingk2009). Numerous studies have shown that social dominance is particularly critical during feeding periods (Miller and Woodgush, Reference Miller and Woodgush1991; Thomson et al., Reference Thomson, Barnes and Prestidge1991; Grant and Albright, Reference Grant and Albright2001; Huzzey et al., Reference Huzzey, DeVries, Valois and von Keyserlingk2006). Chamberlain and Wilkinson (Reference Chamberlain and Wilkinson1996) found conflicting views on the merits of dividing a herd into sub-groups based on either milk yield per cow or the separation of heifers from cows. Krohn and Konggaard (Reference Krohn and Konggaard1979) concluded that separating a herd into sub-groups was beneficial for first-lactation heifers that are kept separate from the rest of the herd as they spent 10% to 15% more time eating and recorded 20% higher intakes. Grant and Albright (Reference Grant and Albright2001) reported that moving cows between groups had a negative social effect that lasted for 3 to 7 days. Stocking density is an important factor in organic dairy systems, with a direct link to welfare problems, specific diseases and herd performance. While organic standards clearly define an acceptable stocking density on a farm to be 1.7 cows/ha or less, this can be misleading. For example, a farm allocating a significant proportion of the total land area to growing crops may have a low stocking density for the farm but a high density for its dairy enterprise when managed on a relatively small land area.