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'What Stocking Rate For My Farm? Maximising Milk Production From Pasture

15 January 2013

To gain insight into what post-quota Irish dairying might be like, field trials on two dairy farms have been carried investigating into stocking rates on farm productivity by researchers by Teagasc at Moorepark, County Cork.

In the next decade, fewer dairy farmers with increased operational scale will take advantage of the opportunities provided by milk quota abolition to increase milk production and farm business profitability from grass based systems fuelled by leading edge management practices. Post quota, and with profitability per hectare as the core objective, Irish dairy farmers must develop and expand their production systems by increasing home grown pasture production and utilisation by virtue of a completely new attitude to dairy herd feed management.

In future, dairy farm businesses will become completely specialised in dairying with contract rearing of young stock, higher dairy farm stocking rates (SR) and more feed efficient high Economic Breeding Index (EBI) dairy cattle to maximise milk production from pasture.

Why are Stocking Rate and Mean Calving Date and Rate so Important?

To capture the maximum benefits of grazed grass, the most fundamental management practice must be to have the correct number of cows calving compactly at the beginning of the growth season (Figure 1). Stocking rate is traditionally defined as the number of animals per unit area of land (livestock units/hectare (ha)) and is best considered as a balancing act between feed supply (the amount of grass grown and the level of feed purchased in this case) and herd demand (the number of cows needed to eat the available feed).

Stocking rate is widely recognised as the major factor governing productivity from grass and previous research indicates that, while milk production per cow is reduced, milk production per hectare will tend to be maximised at higher SRs as increased animal demand drives more efficient grazing practices and improved sward utilisation.

While delivering superior per hectare productivity, increased SRs place added pressures on winter feed supplies and may result in increased feed and capital costs (associated with accommodating and feeding increased numbers of animals). It is therefore recommended that the overall SR of the farm is closely aligned to the individual farms grass growth capability. The optimum stocking rate should allow relatively high individual animal performance but also relatively high grazed grass utilisation to be achieved.

Calving date is also an important factor in grass-based milk production systems and influences both the milk productivity of the dairy herd (lactation length) and also the requirement for supplementation at grazing. In general, the herd should be calved as early as possible, provided that it can be fed adequately from a predominantly grazing diet throughout the lactation.

While highly dependant on the individual farm characteristics, the optimum herd mean calving date will allow high individual animal performance to be achieved by aligning animal feed requirements with spring grass growth to realise high individual animal performance over a 285 day lactation length with minimal requirement for supplementation at grazing. At a given SR, the correct calving date will maximise animal performance by increasing the length of lactation as well as having a high level of production per day of lactation.

Calving too early, in particular at higher SRs, will lead to underfeeding or a requirement for increased supplementation as grass growth rates will be unable to match herd demand in early spring. A spread out calving rate or delayed calving date will lead to reduced grass utilisation as insufficient numbers of dairy cattle are available and grass is wasted.

While there is no ideal mean calving date that will be appropriate to every farm (due to differences in ground conditions, grass growth rates, SRs, etc.), a mean calving date of February 15th to 25th with 90% of the herd calved in 42 days appears to be generally appropriate for most Irish dairy farms in comparison to the current average mean calving date of March 15th.

The current average national SR (1.9 livestock units per hectare; LU/ha) and mean calving date (MCD = March 15th) of Irish dairy farms differs considerably from dairy research herds (SR = 2.5 – 3.3 LU/ha and MCD = February 15th) and indicates that there is considerable scope to increase productivity on Irish dairy farms post quota.

A Review of Recent Research Results on Stocking Rate

Recent research at Curtin’s Farm, Teagasc Animal and Grassland Research and Innovation Centre Moorepark and Ballyhaise Agricultural College has been investigating the likely effects of changes in SR and herd calving date on the productivity of Irish grass-based milk production systems post milk quota and the main findings of these multi-year experiments are reported here.

The importance of calving date and rate and stocking rate to the overall design of highly profitable grazing systems.

Experiment 1: The Curtin’s Farm Stocking Rate Experiment (2009-2012)

The study at Curtin’s Farm is testing the productivity and profitability of a range of SR systems (Low: 2.51 cows/ ha; Medium: 2.92 cows/ha and High: 3.28 cows/ha) and two compact mean herd calving dates (February 14th and March 1st). The study is currently in year 4 and includes high EBI Holstein Friesian cows (EBI = €154). The overall study objective is to identify the optimum overall farm SR and MCD combination to deliver the greatest financial return to the dairy farmer. The low SR treatment was designed to allow each animal to express its milk production potential, unrestricted by limitations in feed supply (based on a target post-grazing residual sward height 4.5 to 5.0 cm).

While foregoing individual animal performance targets, the aim of the medium SR and high SR treatments is to investigate the potential to increase animal productivity per ha by increasing herbage utilisation at higher SRs through increased grazing intensity. (The targets for post-grazing residual sward heights were 4.0 to 4.5 cm and 3.5 to 4.0 cm for the medium and high SR treatments, respectively.)

Milk Production Performance of the Curtin’s Herd (2009-2011).

Calving group1 Early: mean calving date = February 15th, Late: mean calving date = March 1st
Stocking Rate2: Low = 2.52 cows/ha, Medium = 2.94 cows/ha, High = 3.28 cows/ha

Effect of stocking rate (SR) treatment (low SR = 2.51 cows/ha, medium SR = 2.92 cows/ha, and high SR = 3.28 cows/ha,) on the weekly milk production per ha supply profile during each calendar week of year.

Effect of Stocking Rate on Grazing System Productivity (2009-2011)

Calving group1 Early: mean calving date = February 15th, Late: mean calving date = March 1st
Stocking Rate2: Low = 2.52 cows/ha, Medium = 2.94 cows/ha, High = 3.28 cows/ha

The effect of stocking rate on grass growth during the four year study.

Key Lessons from the Curtin’s Farm Stocking Rate Study

The results of this study clearly highlight that increasing SR can be used to increase milk output through increased grazed grass growth and utilisation, however winter feed requirements were not achieved for the higher SR treatments within the study. As farmers increase SR, total milk output from the dairy farm will increasingly be limited by grass growth and so the development of grazing management practices to improve grass production and quality will take precedent over practices informed by individual animal performance.

Grazing (and nutrient) management to support higher SRs post milk quota will be concerned with achieving adequate soil fertility, reseeding underperforming swards and achieving the correct balance between grazing severity and individual animal intake. Further research is required to consistently increase grass DM production and utilisation on each hectare of farmland available for milk production to support higher SRs.

Experiment 2: The Ballyhaise College Dairy Experiment (2008 – 2011)

The objective of this study was to compare the biological efficiency of two likely future pasture-based production systems of spring milk production differing in overall SR and concentrate supplementation level on a wetland drumlin soil. Data was collected from 120 animals over four years (2008 - 2011). The herd had an MCD of March 1st in each of the four years of the study.

Systems Being Evaluated at Ballyhaise:

a) Low cost enclosed system (HG): This was a low cost pasture-based system focused on maximum grass production and conversion to milk and with all winter feed requirements produced from within the grazing platform. The SR of this treatment was 3.1 LU/ha. Concentrate supplementation was set at the minimum level required to buffer periods of low grass growth during the grazing season.

b) High pasture utilisation open system (HI): This was a high supplementation/high output system based on a maximum grass conversion to milk from the grazing platform. Stocking rate on this farmlet was 4.5 LU/ha, while the majority of the winter feed requirements were imported from outside the grazing platform.

The HG system was designed as a low cost pasture management system for a post EU milk quota scenario based on high levels of pasture utilisation and a low level of concentrate supplementation. The HI system was a high productivity pasture system to increase milk output per hectare by increasing SR to utilise more of the available herbage produced during mid-season and supplementing pasture with concentrates and silage during the shoulders of the grazing season when grass growth was insufficient.

Grass Growth and Feed Utilisation

Average pasture growth at Ballyhaise was 13.2 ton DM/ha between 2008 and 2011. Grazing management practices, based on increased grazing severity and reducing pre-grazing herbage yields to improve pasture quality and increase regrowth rates, were adopted during the study.

Annual grass growth rates for both were high at 14.2 and 15.9 tonnes DM/ha, respectively during 2011. The higher growth of the HI system is consistent during the later years of the study and can be partially attributed to an increased level of nutrient loading with the HI system arising from increased feed supplementation over the four years of the experiment.

The feed requirements for the HG and HI systems are outlined in Table 3 below. Grass utilisation was estimated as 10.9 and 10.7 tonnes DM/ha for HG and HI, respectively, during the study, with the remainder of the diet based on grass silage and concentrates.

Concentrate supplementation was 542 and 864 kg DM/cow for the HG and HI systems while total silage requirements, including that fed during lactation, was 1,156 and 1,452kg DM/ cow respectively.

During the study, only 704 and 145 kg DM/ cow of silage was actually conserved for the HG and HI systems, respectively, leaving an annual silage deficit of 451 and 1,317 kg of silage DM/ cow, respectively.

Effect of Feed System1 on Individual Animal Requirements at Ballyhaise.

Feed system1 HG = Low input pasture system, HI = High output per hectare system

Milk Production

The effect of system of production on total lactation milk production over the four year period is shown in Table 4. The results demonstrate that with improved grassland management in combination with increased SR, significant increases in milk production per hectare of farm land can be achieved with both HG and HI type systems. During the 2008 to 2011 period, the HI system produced more milk per cow and higher milk solids (fat plus protein) per hectare.

The higher total lactation milk, fat, protein and lactose yield achieved with the HI system group was expected, given the large increase in energy supply to this system. The results of this study demonstrate that inclusion of supplements, with a concomitant increase in SR, can have beneficial effects in improving the productivity of grazing dairy systems by achieving high pasture utilisation in addition to high per animal production performance.

Effect of System of Production on Milk Production at Ballyhaise.

Feed system1 HG = Low input pasture system, HI = High output per hectare system

Both systems of production at Ballyhaise produced no milk between December 20th and start of calving in early February. Figure 4 outlines the milk supply profile for Ballyhaise during the four years of the study and illustrates that even on a wetland soil type, a peak milk supply of just 3.25 - 3.5% during the peak week of supply in mid- May (equivalent to 14 - 14.5% supplied during the peak month of May) can be achieved with a compact calving dairy herd. The overall milk supply profile for both systems at Ballyhaise is also outlined in Table 5.

The production system characteristics outlined will maximise profitability at farm level through the efficient conversion of milk from grass and also ensures that 10 months of high quality milk is supplied from a profitable system.

The effect feed system (high grass (????) and high intensity (????) on the milk production per hectare per week of year.

The Effect of Feed System1 on Milk Supply Profile

Feed system1 HG = Low input pasture system, HI = High output per hectare system

Key Lessons from the Ballyhaise Research Study

While increasing SR beyond the growth capability of the farm greatly increases overall milk productivity and can be used as a short term strategy to increase animal numbers in advance of expanding on to a larger land block, in the longer term, SRs that largely exceed the growth capability of the farm contribute little in terms of additional grass utilisation and consequently result in significant increases in purchased feed and overall milk production costs.

Conclusions

Dairy farm expansion puts significant additional pressures on the existing dairy farm business and necessitates systems which are entirely profit focused to meet debt repayment commitments. The authors of this paper believe that Irish dairy farms should aim to achieve a minimum SR of 2.4 LU/ha and that further increases in SR should only be considered after completely removing beef cattle, lowly productive dairy cows and young stock from the grazing platform. Furthermore, the current analysis indicates that increasing SR beyond 2.8 LU/ha should be considered as a form of intensification based on potential efficiency gains (in terms of grazed grass, labour and capital infrastructure utilisation,) rather than as a long term means of overall farm business expansion.

Similar to previous studies, this analysis shows that at average or higher milk prices in future years, increasing milking platform SR beyond 2.4 LU/ha can increase overall farm system profitability although the degree to which farm profit is increased is highly dependant on farm grass growth. As Irish milk producers aim for larger herds post milk quota, pasture growth will limit and frustrate the expansion process. It is therefore essential that dairy farmers use the intervening years to quota abolition to adopt grazing and nutrient management practices that ensure high levels of annual pasture productivity.

On dairy farms that achieve annual pasture production of between 13 and 16 tonnes DM/ha/yr, increasing SR to 2.7 to 3.3 LU/ha in combination with an appropriate calving pattern will increase the productivity and profitability of the dairy farms business post EU milk quota.

References

Hodgson, J., and T. J. Maxwell. 1988. Grazing Research and grazing management. HFRO Biennial Report 1979-8. p169-187.

O’Donovan, M. 2000. The Relationship between the performance of dairy cows and grassland management on intensive dairy farms in Ireland, Ph.D. thesis, University College, Dublin

Shalloo, L., P. Dillon, M. Rath, and M. Wallace. 2004c. Description and validation of the Moorepark Dairy System Model. J. Dairy Sci. 87: 1945-1959.

Further Reading

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January 2013

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