Rearing Your 2010 Herd -  An A to Z of Heifer Rearing

Rearing dairy heifers efficiently has the potential to improve farm profit by over £11,000 per 100 cows. It was recognised that an integrated approach in terms of research development and technology transfer was necessary in order to make progress. Thus, the Agri-Food and Biosciences Institute (AFBI), the College of Agriculture, Food and Rural Enterprise (CAFRE), DARD, AgriSearch and John Thompson and Sons formed a partnership to integrate the results from research programmes, an extensive survey of NI dairy farmers and on-farm trials into a new rearing regime to improve the sustainability of dairying.

Parts 1 to 4 and 11 are in the calf section of the web site while Parts 5 to 11 are in the dairy section.

Only one third of milk producers start breeding heifers at the optimum age for economic heifer rearing yet research and development by the partners in this programme show that a live weight at first calving of 540-580 kg at 23 to 25 months of age can provide savings on feed inputs and grazing, gives better reproductive performance and decreased incidence of lameness. In addition fewer herd replacements are required and there are savings on housing facilities, labour inputs and other overhead costs.

This article reviews the research and development which underpins this calving target and the feeding guidelines developed by John Thompson and Sons Ltd, in collaboration with AFBI and CAFRE, as part of the heifer rearing blue-print.

Effects of age at first calving on subsequent performance

Research over a number of years has indicated that, economically, the optimum age at first calving is between 23 and 25 months of age.  Whilst first lactation milk yields may be increased by delaying age at first calving beyond 25 months of age, this is outweighed by the additional rearing costs and poorer reproductive performance which impacts on overall lifetime yield.

For example a recent analysis by AFBI of data from herds of the Irish Holstein Friesian Association found that -  moving from 24 to 30 months of age, increased first lactation milk yield by 452 litres but increased calving index by 20 days. By the 3^rd calver stage differences in cumulative milk solids yield from first calving had disappeared.  Work in GB has also shown fewer problems around calving and increased herd life (+0.2 lactations) with heifers calving at 24 compared with 36 months of age.

Age at first calving has a considerable impact on the number of replacements carried on a dairy farm (Table 1).  Compared with calving at 24 months, 3-year old calving increases the number of replacement stock on a 100-cow dairy farm by 30 heifers.  This will increase farm stocking rate by 0.4 cow equivalents per hectare and by 25 kg of organic manure N per hectare.  To maintain the same organic manure loading as a farm calving heifers at 24 months, an additional 10 hectares of land would be required for a 100-cow dairy herd.  Calving at older ages also places greater demands on housing facilities, labour inputs and other overhead costs.

Table 1.  Number of heifer replacements required per 100 cows according to age at first calving

What is the optimum calving size for Holstein Friesian heifers?

Body size targets for Holstein-Friesian dairy herd replacements have been developed from a number of research studies carried out at AFBI Hillsborough over recent years on the feeding and management of dairy heifers. The main findings of this work are summarised as follows:

Live weight at calving on performance

• Milk production. Heifers reared to calve at heavier (620 kg) compared with moderate weights (540 kg) produced 800 litres more milk in their first lactation.  However the effects did not extend into subsequent lactations.
• The additional milk produced by rearing heavier heifers (620 compared with 540 kg) resulted from greater body condition score in early lactation, resulting in poorer reproductive performance. In addition, foot claw condition was poorer with heavier heifers (20% more heifers with heel erosion during rearing period) and this was associated with increased lameness (50% higher (poorer) locomotion scores).

Growth rates during the rearing period and subsequent performance

• Increasing growth during the first year of life (above 0.7-0.8 kg per day) increased skeletal size. However, very high planes of nutrition can have detrimental effects on udder development, particularly with strains/breeds of lower mature weight.
• Increasing growth during the second year of life (above 0.8 kg per day) has been found to increase body condition score at calving, reducing dry matter intake in early lactation.
• Feed inputs to achieve moderate (540-580 kg), but not heavy (600 kg+), live weights at first calving are significantly less. In studies at AFBI Hillsborough, this has amounted to 500-800 kg less concentrates over the 2-year period. Also, in-calf heifers reared to moderate weights required less grazing area (12% less)
• Forage type (silage versus straw) fed during the rearing period has been found to have only small effects on subsequent performance in the milking herd

Management At Mating

To achieve an average first calving age of 24 months, insemination needs to start from 13.5 months of age.  Once the decision is made to start mating, on average it will be 11 days before the average heifer is on heat.  Allowance must also be made for missed heats and returns to service.  Good fertility records and observation are essential and submission rates can be improved through using heat detection aids such as tail paint, kamars, teaser bulls, and pedometers.

Currently, 30% of producers surveyed across Northern Ireland estimate that they commence breeding at 13-14 months of age.  A further 30% of producers commence breeding heifers at 15-months of age with 40% of producers delaying the start of breeding to 16 months or above.  So overall, only one third of producers are aiming to start breeding at the optimum age for economic heifer rearing, with a significant number delaying their breeding programme and consequently incurring increased costs.

In terms of deciding when to commence breeding, body size and live weight as well as age are considered important by the majority of producers (90%+).  On dairy farms, visual assessments only are made of heifer growth with little weighing or measuring being undertaken (less than 5% of producers).  Whilst producers are confident of their ability to identify the optimum size for breeding, the AFBI/CAFRE survey shows (1) there can be a large difference between actual live weight and that predicted by producers using visual assessment, (2) body sizes targeted by producers to commence breeding tend to be larger than optimum.

Monitoring growth

Monitoring heifer growth by measuring heifers is key to making informed management decisions. Over the last 10 years, AFBI Hillsborough has collected a comprehensive dataset on body size measurements during each stage of the rearing period. This has enabled development of a simple and easy assessment of live weight, through the measurement of heifer girth. Measuring tapes scaled with the live weight of Holstein Friesian heifers are now available to enable producers to monitor progress of heifers against targets at key times, facilitating a cost effective rearing regime. The optimum live weights developed from the Hillsborough research programme are presented in Table 2.

Table 2.  Target live weights for Holstein Friesian heifers

More information on heat detection and dairy herd fertility management is available through the CAFRE Dairy Herd Fertility Challenge or at: http://www.ruralni.gov.uk/index/learning/challenges.htm

Central to achieving 24 month old calving at 540-580kg live weight and the resultant economic benefits is a controlled feeding and management approach throughout the rearing period from 12 weeks old to the point of calving.

John Thompson and Sons Ltd. in collaboration with AFBI and CAFRE, have developed a series of rearing blueprints to achieve a liveweight gain of 0.7-0.8 kg/day from 12 weeks old to calving.

The blueprints take into account different management and feeding policies, land availability/accessibility, labour resources and in particular the season of birth of the calf, as this has a significant impact on the ease with which targets will be met on farm. This is particularly important with March-July born calves.

Three of the blueprints are based on winter diets using grass silage with an ME content of approximately 10.7 MJ/kg DM and summer grazing. The fourth is based around a housed system using straw as the forage. In each case a concentrate allowance of an appropriately balanced Heifer Rearing concentrate is recommended to enable target growth rates to be acheived.

Rearing the August-November born calf:- Key Points

12 Weeks old – mid April

• Achieve steady growth rate over the period - balanced nutrition required throughout

• Good ventilation and no draughts in the rearing house

• Good calf health requires good nutritional and housing management

From Mid April – Autumn

• Maintain a level pattern of concentrate supplementation at grass to ensure adequate calf growth

• Adopt management and veterinary routines to control parasites

• House sufficiently early in Autumn to ensure performance is maintained

Breeding Management

• Minimise stress around mating and maintain a steady nutritional regime before and throughout the breeding period

Post-Breeding and Pre-calving

• Maintain steady growth rate throughout pregnancy and calve down at Condition Score 2.5-3.0

• Acclimatise heifers to the post-calving diet for 3 weeks pre-calving

Feed Plan to Achieve targets with August – November born calves

Rearing the December-February born calf:- Key points

12 Weeks old – 9 months of age

• Calves should be kept inside until at least 12 weeks of age

• Pasture quality must then be very good, and good parasite control adopted

• Concentrate may be required throughout the summer to ensure controlled growth rates – this is primarily a factor of grazing management

• House in early Autumn to ensure a steady growth rate through this difficult period

Second winter

• Settle animals quickly onto full winter rations and adopt an appropriate parasite control programme

Second summer

• These animals must be kept growing at pasture and this may require supplementation with concentrates, depending on grazing management

• House in early Autumn to ensure animals maintain steady growth during pregnancy

Pre-calving management

• Maintain a steady growth rate throughout pregnancy and calve down at Condition Score 2.5 - 3.0

• Acclimatise heifers to the post-calving diet for 3 weeks pre-calving

Feed Plan to Achieve targets with December – February born calves

Rearing the March - July born calves:- Key Points

12 Weeks old – 11 months of age

• One option is to keep these calves inside until 11 months of age and preferably offered straw as the basal forage

• While this method adds costs it is essential if these calves are to calve down at 24 months of age

• This method also allows for pulling these calves towards 22-23 month old calving which may be beneficial in terms of herd calving pattern

Second Summer period

• These animals must be kept growing at pasture and depending on grass quality and grazing management supplementation with concentrates may be required

• At grass a good parasite control policy is vital

• House in early Autumn to ensure animals maintain steady growth during pregnancy

Pre-calving management

• Maintain a steady growth rate throughout pregnancy and calve down at Condition Score 2.5 – 3.0

• Acclimatise heifers to the post-calving diet for 3 weeks pre-calving

Feed Plan to Achieve targets with March - July born calves

Straw System:- Key Points

• Conventional grass silage and grazing systems have their advantages e.g. reduced variable costs. However in some farm situations e.g. shortage of land/labour or requirement to reduce bio-security risk with off-farm grazing, straw-based systems may offer an advantage

• Straw must be of good quality

• Allow animals access to grazing during some stage of the rearing programme to enable them to develop grazing skills

• Remember animals put to grazing after being housed for most of the rearing period are still susceptible to intestinal parasites despite their age

Feed Plan to Achieve Targets with a Straw-based System

Summary

Key issue is steady growth rate of 0.7-0.8 kg/day from 12 weeks old to calving at 540-580 kg, condition score 2.5-3.0

Heifer rearing delivers results on farm

John Thompsons & Sons Ltd. recognised that there was a considerable volume of new research evidence on heifer rearing, particularly from Hillsborough, which if implemented at farm level had the potential to reduce milk production costs by over 1 p/litre on all milk produced on the farm.  As a result in 2005 they developed a series of Heifer Rearing Blueprints for managing and feeding heifers born during different seasons of the year.

In order to validate these blueprints and ensure that they could be easily implemented at farm level, in September 2005 Thompsons, in conjunction with AFBI Hillsborough and CAFRE, Greenmount entered into a province-wide heifer rearing project on 8 commercial dairy farm units.  These farm units ranged in size from 90 to 400 cows.  The objective of the project was to demonstrate that the rearing blueprints, in conjunction with a simple system of measuring heifer size quarterly, could economically produce well grown heifers to calve at 24 months of age.  Heifers on each farm born after 1^st September 2005 were therefore entered ounto the blueprint rearing systems.

Project set-up

A selection of heifers within each age group (normally 5 heifers per group) were measured for size on a quarterly basis on each of the 8 farms. Progress in weight gains during the rearing period were monitored and nutritional regime adjusted where necessary.  In total, over 1,500 animals have been reared according to their appropriate blueprint with some now coming near the end of their first lactation.

Results

As can be seen from Table 1 below the average age at first calving of the 2005/06 season born heifers has been reduced from 27-29 months to 25 months of age.

Table 1.  Average age at calving in autumn-born heifers across the farms

¹ Data from all 8 farms; ² Data from 5 milk recorded farms; * Data includes completed and projected records

As expected, first lactation milk yields in the recorded farms have been reduced (by approximately 150 litres) (Table 1), however projected calving interval records show an improvement in fertility performance, key in meeting the target lifetime yield of 30,000 litres, a figure which is well above the national average of approximately 25,000 litres.

Monitoring Progress

Tracking heifer growth performance through quarterly measurement highlighted a number of issues.

• Quality of winter forage had a significant effect on the ability of heifers to meet targets when fed according to the blueprint recommendations.

• Equally periods of difficult grazing conditions either in grass quality or quantity significantly impacted on performance.

• If not recognised early, these periods of poor growth resulted in heifers not achieving targets and subsequently incurred increased feeding costs.

• It is also important to recognise periods of over nutrition where excess fat will be laid down.This is common on high quality silages where concentrates continue to be fed and is detrimental to long term heifer performance as well as adding unnecessary cost to the system.

For example, a yearling heifer given a very good quality silage (high ME content and good intake potential) can achieve 0.8 kg/day when supplemented with only 0.5 kg concentrate/day. In contrast with a lower quality silage, 3.5 kg concentrate will be required to achieve the same target growth rate. There are therefore massive opportunities for making savings in heifer rearing costs through ensuring that they receive good quality silage where at all possible. Unfortunately, on many farms the heifers are allocated the poorer quality silages and hence will require higher levels of concentrate supplementation.

To provide farmers with guidance on the necessary levels of concentrate required with differing silages, Thompsons are now providing concentrate feeding guidelines for heifers of different ages on all their silage analysis reports.

Similar opportunities arise when calves/heifers are at grass. This is particularly true when animals are in their first year at grass. In the majority of grazing systems, young calves at grass will require concentrate supplementation. However if calves can be grazed as a leader group, in which they can select the higher quality grass leaf and leave the lower quality material to be grazed by older stock, then concentrate levels can be reduced - or even eliminated

An additional, and vital, factor in management at grass is the need for a robust approach to the control of parasites. A good grazing season can be quickly ruined through a relatively short lapse in parasite control. While this particularly applies to young calves it can be equally important with older animals.

Key Messages

• Blueprint rearing systems ease management decisions.

• The systems presented here have been validated on 8 farms with 1500 heifers.

• During winter, silage quality dictates the amount of concentrate required to acheive 0.7-0.8 kg liveweight gain/day.

• Thompsons have now introduced a “Heifer Concentrate Feeding Recommendation” on all their silage reports.

• Grazing systems can be extremely variable and often cause many problems.

• Monitoring growth rates and adjusting feed accordingly is the key to success and cost reduction in heifer rearing.

Sire selection represents the key breeding decision, with long-term effects on animal performance, health, welfare and overall farm profitability.  Today’s breeding decisions will result in replacements entering the dairy herd in 2011, with a direct impact on herd performance lasting to 2015 and beyond.

Sire proofs work in practice

The breeding values of sires for an increasing range of traits are now available. These values are expressed as Predicted Transmitting Abilities (PTAs) which measure the average value of traits transmitted from a sire (or cow) to its progeny and are derived from the performance of the animal and all known relatives.

Increasingly, genetic information on fertility, health and longevity traits is becoming available for sires.  Whilst such traits are very much affected by herd health, feeding and management, genetics has also a significant effect.

In regard to reproductive performance, the genetic variation in daughter fertility produced from different sires has been found to be relatively large, meaning that significant genetic progress can be made.  Thus in sire selection it’s important that appropriate consideration is given to health and fertility traits, (published for example, at www.ukcows.com and www.DairyCo.org.uk )

Selection indexes are useful tools

An index of total economic merit is a combination of an animal’s predicted transmitting ability (PTA) for all economically important traits, with each trait weighted by its relative economic value.

In the UK, the index of total economic merit, Profitable Lifetime Index (PLI), has recently been amended, based on research carried out by Scottish Agricultural College (SAC) on behalf of DairyCo.  In general terms, the new PLI has a reduced emphasis on production traits and an increased weight on the ‘fitness’ traits in line with their future expected economic values. to farmers. Consequently, the predicted genetic response to selection on the new PLI indicates that alongside increased production, lifespan will increase, somatic cell count will decrease, feet and legs and udder traits will improve and the decline in fertility traits will have nearly been brought to a standstill.  In addition the new PLI is presented as a ‘true’ Profitable Lifetime Index and so reflects the profitability differences of the progeny over a lifetime, rather than per lactation as undertaken previously.

The relative economic values for traits within selection indices are determined from national farm economic models.  These models continually develop to take into consideration changing market outlooks, new environmental considerations and developments in production systems.  AFBI is currently carrying out work in this area, with SAC, examining the relative economic values for production and non-production traits in 7,000-8,000 litre systems.  Modelling work has shown these moderate output systems are optimum over a range of milk pricing/input price scenarios and are likely to be the “norm” for the majority of the industry in Northern Ireland.

Sire selection for use on maiden heifers

Ease of calving is an important consideration in selecting sires, particularly for use on maiden heifers. Calves are more likely to die if they have experienced calving difficulty.  Calves born from a difficult calving are also more likely to be weak or have low vigour, and these grow more slowly to weaning and are more susceptible to other diseases.  On the cow side, there is evidence that dystocia reduces milk yield, increases the risk of mastitis and increases the chances that a cow will be prematurely culled.

In terms of sire selection, it is important to note the negative genetic relationship between genetic merit for ease of calving and subsequent maternal calving ability.  Within a breed, female calves born more easily are expected to show greater difficulties when giving birth as dams, because of reduced pelvic dimensions.  Hence selection for both direct and maternal genetic components of calving ease is the best way forward.

Currently some genetic information is available on direct calving ease for sires.  Work by SAC is currently being undertaken, with input from AFBI Hillsborough, to better quantify the relative economic value of calving ease and enable the incorporation of direct and maternal calving ease traits into selection indexes. At present no UK data is available for maternal calving ease, hence type predictors such as rump width are the only available option.

Current sire selection

For the first time, we have information regarding the basis for sire selection by dairy producers in Northern Ireland based on the AFBI/CAFRE heifer survey. The key messages from this AFBI/CAFRE work undertaken over the last 12 months are summarised below.

• In Northern Ireland, whilst the use of AI is extensive, it is still lower than some of the other main dairy producing countries and there is scope for increased use of AI. 62% of producers use AI for the majority (50% plus) of their heifer matings. With mature cows, the use of AI is slightly greater, with 69% of producers using mainly AI for breeding.

• A high proportion of farmers consider ease of calving and PTAs for milk composition as very important criteria in sire selection (Table 1). In addition, milk yield and type traits are considered very important by a significant proportion of producers. There were no indications of any significant use of the fertility index in sire selection.

• Surprisingly, only a relatively small proportion of farmers consider that PLI is very important, with significantly more assessing it either as unimportant or had no opinion on it.

• • Table 1.  Sire selection criteria for use on maiden heifers

    Criteria	% of producers assessing as very important	% of producers with no opinion or consider unimportant
    Ease of calving	56	5
    Milk composition	44	12
    Type traits	26	21
    Milk yield	22	16
    Selection index (PLI)	7	43.5
    Cost of straw	6	34

    Genomic selection

    Increasingly, genomic (DNA) data will be incorporated into future dairy cattle selection programmes. This will enable more accurate selection index evaluations and direct increased genetic gains. Inclusion of genomic data in national evaluations is expected to increase genetic progress by around 50% over the next 10-15 years.

    The use of genomic information in the livestock industry is not a new phenomenon. Many farmers and AI companies routinely send hair samples for parentage identification, as well as the detection of genetic defects such as BLAD and CVM.

    AFBI have developed a resource in this area enabling parentage verification in support of animal identification (contact Dr Adrian Allen, VSD, Stormont: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ). Current research, in partnership with The Roslin Institute (University of Edinburgh), funded by the BBSRC, is investigating whether host genetics influences TB susceptibility in cattle. This potentially involves identification of DNA markers linked to TB resistance, which could be used to breed for reduced TB susceptibility.

    Main messages

    1. Sire proofs are a reliable indicator of progeny performance.

    2. Only high PLI bulls are made available by breeding companies.

    3. Genetic evaluations for fertility, health and welfare traits are becoming increasingly available.

    4. Selection indexes, such as PLI, are the best way to combine information on the large number of traits now available for sires. Currently, the PLI is only considered important by a minority of producers. It will be important to address this. AFBI work looking at selection indexes specific to Northern Ireland circumstances will play a role here.

    5. The accuracy of selection indexes will increase further with the introduction of genomic information. In addition, new possibilities for breeding for disease resistance are likely to develop.

    
    

  Part 9. Transition into lactation

  Introducing the heifer into the herd

  During the period around first calving, dairy herd replacements are exposed to many changes which, if not managed, can result in nutritional, physiological and social stress. These types of stressors can have long-term effects on subsequent milk production, fertility, health and welfare.

  Training heifers to the parlour

  Training heifers prior to calving to the milking routine has been suggested as a way to reduce stress in early lactation. The AFBI/CAFRE heifer survey indicated that 58% of producers adopt this practice. Research has shown that while there is a benefit of increased milk yield in early lactation – 1.3 kg/day over the first 100 days of lactation, and a significant reduction in somatic cell count (95,000 versus156,000), there were negative effects on fertility.

  Introducing heifers into the herd

  The majority of producers introduce dairy heifers straight into the dairy herd after first calving.  However, some producers form small groups of calved heifers (or heifers/mature cows) and introduce these groups into the milking herd together. This approach is likely to be beneficial, based on the findings of recent research at AFBI Hillsborough.  This work found that heifers introduced to the milking herd as pairs rather than individually had higher milk yields in early lactation (2 kg/day during the first month of lactation) without detrimental effects on fertility.  Behavioural observations indicated the paired heifers were less fearful than those introduced into the milking herd as individuals. Delaying the introduction of heifers (as singles) into the herd from day 1 to day 7 post-calving had no benefits on performance or behaviour.

  A small study in GB has indicated that heifers find it easier to integrate if they are introduced into the milking herd after the evening, rather than the morning, milking.  Cows are less socially active in the evening thus heifers may have time to settle into the pecking order more easily.  Work funded by DARD and AgriSearch will examine this, and other management options, to enable improved transition management to be developed for dairy herd replacements.

  Managing heifers as a separate group

  Work carried out some years ago in GB and in Denmark reported significant benefits from housing heifers separately from mature cows. These responses were the result of heifers grouped separately spending 10 to 30 minutes longer per day eating compared with heifers grouped with older cows.  It was suggested that this difference in intake was due to the fact that first lactation heifers mixed with mature cows follow the same eating pattern as the cows (social facilitation).  Since mature cows eat faster than first lactation heifers, the eating time for heifers mixed with cows is reduced compared to the situation when heifers are housed as a single group.  With complete diets, the effects of housing heifers separately have been found to be less, or totally absent, perhaps as a result of total time feeding being less of a limitation on total dry matter intake.

  Housing first lactation animals separate from mature cows undoubtedly complicates feeding and management and is only practiced by a very small number of dairy producers in Northern Ireland (less than 1%).  Research information in this area is limited, particularly in relation to effects on reproductive performance, incidence of mastitis and lameness.  Nonetheless, in some housing systems the separation of heifers from mature cows during the first lactation may be a practical and cost-effective practice.

  Housing systems

  There is clear evidence that feet lesions in first lactation heifers are greater when animals are housed in cubicle accommodation compared with straw yards.  Housing heifers for 4 to 8 weeks after calving on straw before moving to cubicle accommodation has been found to significantly reduce the severity of feet lesions.  However, even this limited period of housing heifers on straw would have a significant impact on the costs of production and it is also important to consider that there is an increased risk of environmental mastitis with animals on straw bedded courts.  With cubicle accommodation, emphasis must be placed on adequate number of cubicles and making them as comfortable as possible to maximise lying time and hence reduce the incidence of lameness.

  Main messages

  1.      Training heifers to the milking parlour has only short-term benefits on milk yield and somatic cell counts, and this has not been accompanied by improved fertility (in fact the opposite has been the case in the AFBI study).

  2.      Form small groups of heifers (2+) before introducing them into the main milking herd.

  3.      Housing heifers separately from mature cows during the first lactation may have benefits but complicates management and has been adopted by a very low percentage of producers.

  4.      Housing heifers on straw for 4-8 weeks post-calving reduced lameness but again is not a practical option on most systems. With cubicle accommodation emphasis must be placed on and adequate number of cubicles made as comfortable as possible in order to ensure optimum comfortable lying time.

  
  

Part 10. True heifer costs

Farmers are not aware of the true cost of rearing a dairy heifer!

Dairy farmers in Northern Ireland reckon that they can rear their heifers or less than £1000 and 23 % of these would estimate as low as £500, according to an indepth survey conducted by AFBI/CAFRE. But benchmarking figures show that the real cost is £1220

Typically, dairy heifers calve at 28 months of age on average having consumed 860 kg of concentrate to rear them to this stage. Table 1 shows how current input costs will impact on rearing costs. The average cost of £1,200 is well beyond the estimates given by farmers in the survey. It is evident that farmers often do not take into account the full rearing cost (including overheads) of their heifers.

Table 1.  Typical costs of rearing a Holstein dairy heifer to point of calving

• • A number of points should be noted from Table 1.

    • No account is taken of the farmer’s own labour.

    • There is a large variation around the average. The top 25% most efficient farmers can rear their dairy heifers using over 620 kg less meal per heifer than the bottom 25% of farmers (580 kg compared with 1200 kg). For a 100 cow dairy farm rearing 30 heifers per year, this difference in concentrate feeding at current costs is equivalent to £4,500 per year.

    The top farms:-

    o serve heifers earlier

    o maximise grazing days for heifers

    o make quality silage

    o have more heifers born in the autumn than in the spring

    • Overheads are allocated per hectare on a dairy farm. This method of allocation is the same for all farmers using benchmarking and thus guarantees consistency.

    The high cost of heifers requires high lifetime yields to spread this cost over a greater number of litres. If an animal lasts for only 1 lactation of 7,000 litres and is then culled for £400, the replacement cost per litre for that milk will be almost 12 pence. This shows just how important an investment heifers are to the modern dairy herd.

    Calving age

    Take an example of a farm with 100 cows currently calving heifers at 36 months of age and with 30 heifers over two year old. If this farm moved to calving at the typical 28 month calving, there would be 11 heifers over two years and at 24 month calving there would be no heifers over two years old

    Assume that additional cows can now be accommodated in the housing that the heifers over 2 years of age occupied and that sufficient slurry capacity exists to milk additional cows instead of keeping 30 heifers on average over 2 years of age.

    It is also assumed that 24 month heifers yield 780 litres less per lactation than 36 month heifers while 28 month old heifers yield 580 litres less than 36 month heifers.  The lower yield of 24 month heifers may well be made up during the productive life of the animal but this has been ignored in this calculation.

    Moving from 36-28 month calving.

    Farm profit would be £5,100 higher if the farm moves to 28 month calving and keeps additional cows (up to the 170 kg livestock manure nitrogen per hectare limit).  This assumes an average milk price of 20 pence per litre.

    If the farm stays at 100 cows and moves to 28 month calving, there is land released that does not have to be taken in conacre or land that can be let out.  If a price of £300 per hectare (£120/acre) is used for conacre, the farm would be better off by £4,600.

    Moving from 36-24 month calving

    Farm profit would be £8,400 higher if the farm moves to 24 month calving and keeps additional cows (up to the 170 kg livestock manure nitrogen per hectare limit). This assumes an average milk price of 20 pence per litre. Every 1 pence difference in milk price from 20p would change this calculation by almost £1,000.

    If the farm stays at 100 cows and moves to 24 month calving, there is land released that does not have to be taken in conacre or land that can be let out.  If a price of £300 per hectare (£120/acre) is used for conacre, the farm would be better off by £6,900 (Table 2).

    Table 2.  Increases in profit by moving from 36 month calving to either 28 month or 24 month calving through renting out land or increasing cow numbers

    	28 month calving (typical calving age)	24 month calving (target calving age)
    Moving from 36 month calving and land freed up let out in conacre	£4,600	£6,900
    Moving from 36 month calving and additional cows milked	£5,100	£8,400

    Summary points

    1)    Dairy farmers in Northern Ireland underestimate the cost of rearing their heifers. At current prices, a heifer will cost £1,220 to rear.

    2)    Efficient use of forage will reduce rearing costs. The top 25% of farms use 620 kilos less meal to rear a heifer than the bottom 25%.

    3)    Moving to 24 month calving will increase farm profit if the additional land released is used to milk additional cows or let out in conacre. Savings in rearing costs and additional fertility performance and lifetime yield will be additional benefits.

    4)    Autumn born calves are cheaper to rear to 24 months of age than spring born calves, because they have a higher proportion of grazed grass in the diet.

    
    

    Part 11. Summing up the different aspects of research and development when put into practice.

    Typical performing herd with 100 cows with 30 replacements

    • Calf feeding and management

    o Reducing calf mortality to 3% equates to £400 per annum.

    o Increasing reliance on milk replacer and optimum weaning age: estimated at £12 per calf i.e. £360 per annum.

    • Smoothing the transition into lactation

    o Introducing heifers in groups to main milking herd: estimated at 1-2 litres additional milk in early lactation. Longer-term effects currently being determined.

    • Managing heifers to calve at 24 months

    o Additional cows milked: moving from 28 months to 24 months of age increases profit by £3,300 per annum.

    • Targeting live weight of 540-580 kg

    o Compared with 600 kg+ heifers, feed costs reduced by £130/heifer equating to cost saving of £3,900 per annum.

    o Reproductive performance improved (30 days shorter calving interval) Reduced lameness also observed. Overall, assumed 4 months additional herd life in milking herd increasing output, net of variable costs, by £2,140 per annum.

    Overall financial impact of over £10,000 or over 1 pence per litre on all milk produced.