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Blood urea levels in high producing dairy cows
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Neospora
and Reproduction Study
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Nitrogen
fertiliser and pasture quality
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Selenium
Fertiliser Field Trial
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On-farm indicators of magnesium status in cows
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The Substitution of
Dairy By-Products for Pasture
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Application of Dexcel Whole Farm Model to Lincoln
University Dairy Farm
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Modelling
the effects of zero-inductions on profitability
in dairy systems
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Pasture analysis
in relation to the spring dip in milk production
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Monitoring
climate stress in Canterbury dairy cows
Blood
urea levels in high producing dairy cows [2005]
As an initial scope for this project
the following objective was set: to confirm that high
blood urea are a feature of cows in an intensive managed
pasture dairy farm with known below average embryo survival
(with good submission rates). The trial was designed
to collect about 1200 blood samples for urea analysis.
About two hundred animals were sampled
once a week for six weeks during the mating period giving
1187 samples from a total of 528 cows. Preliminary
analysis suggests that reproductive performance of the
cows is below expected levels and this may be indicating
problems. The whole herd pregnancy rate after 3
rounds of insemination is 73%, and for animals within
the subset sampled for urea at insemination (±10
days) is 69%. Within this subset, cows with High
urea levels (above a mean of 46.4 mg / dl) had a pregnancy
rate of 66.4 versus 71.43% for those cows designated as
Low urea group. Sampled pasture had an average protein
level of 223g/kg DM and digestibility of 798/kg DM.
(Conducted by
Ricky Mandibela [postgraduate student], Alastair Nicol,
and Andrew Sykes, Lincoln University. Funded by
Lincoln University.)
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Neospora
and Reproduction Study [2005]
This study has investigated the possible involvement of
disease issues in infertility at LUDF by [i] pregnancy
testing to define the prevalence and timing of pregnancy
loss and [ii] blood sampling and testing for Neospora
and BVD. Thirty [30] cows [4.6% of the herd] lost
pregnancies; this is very similar to the national
average. Most pregnancies were lost from cows mated
in the first three weeks and most pregnancy losses occurred
soon after the cow conceived. Most farmers would
observe these cows as long returns. All 31 cows
tested were negative for Neospora; 9 however were positive
for BVD. This is surprising since LUDF has consistently
had a bulk milk BVD of less than 10%.
Summary: Both tests indicate
that the LUDF herd does not have a major underlying disease
issue affecting herd fertility.
[Conducted by Donald Arthur, Selwyn
Rakaia Vets, Dunsandel; Adrian, van Bysterveldt, Dexcel.
Funding from Lincoln University Dairy Farm [LUDF]].
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Nitrogen
fertiliser and pasture quality [2003]
The objective of this
trial was to determine and compare the effects of Ammonium
Sulphate Nitrate (ASN) and Urea fertilisers on pasture
dry matter production and pasture quality of irrigated
dairy pastures in Canterbury.
Conclusions
The influence of ASN
and urea at two rates of N application on the production
and quality of irrigated dairy pastures in Canterbury,
New Zealand was investigated. Under the conditions
of this trial representing typical frequent centre-pivot
irrigation and high soil fertility, pasture production
ranged from 15.9 [Control] to 19.4 [ASN 250] t DM ha-1
yr-1 and was strongly influenced by the rate
of N fertiliser application. ASN showed a small
significant yield advantage [P <0.05] over urea
applied at the 150 N rate but not at the 250 N rate.
The clover content
of the sward did not vary significantly with the type,
or rate of fertilisers. Seasonal variation in sward
clover levels was high, and moderately high clover contents
were maintained on fertiliser treated pastures [from 10-45%].
Clover levels in the pastures were 5-10% more dry matter
with virtually no drop in pasture quality.
Further pasture quality
analysis revealed that amino acid concentrations in the
herbage varied widely over the season. The data
indicate that the variation of amino acid levels in the
pasture sampled due to fertiliser treatment is however
small.
[Conducted by
Jim Moir, Keith Cameron, H J Di, Centre for Soil and Environmental
Quality, Lincoln University; Ants Roberts, Ravensdown
Fertiliser Co-operative Ltd; and Wybe Kuperus, Dexcel
Ltd.]
Acknowledgements
The authors wish to thank Ravensdown Fertiliser Co-op
Ltd for funding this study, and Carole Barlow, Hamish
Masters, Trevor Hendry and Koleightne Ford for field and
technical assistance.
For Full Report Click here
Back to
top Selenium
Fertiliser Field Trial [2004]
The objective was to
compare the effectiveness of a range of selenium fertilisers
for increasing pasture herbage selenium concentrations
Summary of selenium
trial carried out on Lincoln University dairy farm from
October 2003 - October 2004
The uptake of selenium
(Se) by pasture herbage from four different Se fertiliser
materials was determined in a field experiment throughout
the course of a whole year. The products tested
were: the commercially available Selenium Chip™;
Selcote®
Ultra; and two new formulations (Ravensdown
A and B), manufactured in a way to slow the release of
Se in the form of sodium selenate. All four Se fertilisers
increased pasture herbage Se concentrations above the
level required to meet the nutritional requirements of
grazing livestock; however, the size and duration
of the responses varied between products. The Ravensdown
A product was as effective as Selcote Ultra at maintaining
pasture Se concentrations above the critical animal health
level for the whole year of the trial. The effects of
the other two products, particularly the Selenium Chip,
were not so long-lasting. Recoveries of Se in the
pasture herbage throughout the year ranged between approximately
15-17% of the Se originally applied in the fertilisers.
[Conducted by R G McLaren.
Funded by Ravensdown Fertiliser Cooperative Ltd]
Back to
top On-farm
indicators of magnesium status in cows [2004]
This study investigated
the suitability of urinary Mg as an on-farm indicator
of Mg status in dairy herds. Serum, urinary and
milk Mg concentrations, along with estimates of Mg intake
in Mg-supplemented and un-supplemented cows were measured
from calving until mid-lactation.
Results from this research
showed that urinary Mg concentration has potential to
be used as an appropriate indicator of herd Mg status
for pasture-fed dairy cows. The use of urinary Mg
concentration offered advantages over blood sampling in
that at low serum Mg concentrations and excretion of Mg
in urine will virtually cease when serum Mg concentrations
fall below 0.7 mmol/l. Hence, cows with low concentrations
of urinary Mg can be identified without requiring a veterinarian
to take blood samples and the delay between sampling and
return of results can be avoided.
Under typical New Zealand
dairy farm conditions urinary Mg concentration could be
a practical indicator of herd Mg status without the need
for correction for urine volume using urinary creatinine
concentration. This probably reflects the high and
relatively constant water content of high quality pastures
used in modern dairy production systems. Observations
suggest that creatinine concentrations may fluctuate with
changes in live weight that occur after calving and during
peak milk production when cows are in negative energy
balance.
A urinary Mg concentration
reference level of 0.5 mmol/l is suggested. Further
studies are required to confirm this for a wider range
of New Zealand pasture-fed herds given the significant
genetic variation in Mg metabolism that is a feature of
the international literature.
Magnesium concentrations
in the pasture ranged from 1.51 - 2.21 g/kg DM.
Dietary antagonists such as potassium concentration in
herbage were greater than 25 g/kgDM - the concentration
at which significant impairment of Mg absorption can be
anticipated. The estimated mean Mg availability
(%) was 13 - 16 during the August to October period in
the Mg-supplemented herd.
Mean serum Mg concentrations
for both herds ranged between 0.72 - 0.96, and 0.77 -
0.92 for the supplemented and un-supplemented herds, respectively.
Serum Mg concentrations from 28% of the Mg-supplemented
cows were below the accepted critical clinical threshold
of 0.6 mmol/l on one or more sampling days. The
supplemented cows were offered Mg at recommended rates
via an in-line water dispenser. However, owing to
lower than expected levels of trough water intake, the
level of Mg supplementation initially, was not adequate,
highlighting the need to also monitor water flow to adjust
Mg concentrations or to dust additional Mg on pasture
or silage.
In conclusion, it is
suggested that urinary Mg concentration may be used as
an appropriate on-farm indicator of herd Mg status in
pasture-fed dairy cows in early lactation. The occurrence
of an animal with a urinary Mg concentration of <0.5
mmol/l in a herd with a mean urinary Mg concentration
of <4.0 mmol/l suggests the need for supplementation.
Results indicate that for animals in a pasture-based system,
with access to similar levels of dry matter and water
intake, urinary Mg concentration can be used exclusively,
without the need to be corrected for creatinine, thus
providing a simple on-farm method to assess herd Mg status
and evaluate the need for Mg supplementation.
(Conducted by Professor
Andrew Sykes and Amanda Phillips (Masters student) with
scholarship support from Dexcel).
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The Substitution of Dairy By-Products
for Pasture [2005]
The objective of the trial was
to quantify the level of substitution for pasture at three
feeding levels of PROLIQÒ,
none (control), 1/2 adlib and adlib using three reps of
8 calves for each treatment for 8 weeks. This was
quantified using a combination of pasture disappearance,
alkanes measurement of grazing intake and live-weight
gain of groups of calves. Water and PROLIQÒ
intake were measure and a plasma mineral assessment was
carried out.
Conclusion:
PROLIQÒ can be fed in large
quantities to calves without adverse effects as long as
care is taken with introducing them to the feed.
In
this trial PROLIQÒ was substituted
for pasture at the rate of -0.5 to -0.7kgDM of grass per
kgDM PROLIQÒ consumed.
This did not give a significant increase in consumption
of dry matter in calves fed PROLIQÒ
which would explain the lack of live-weight response.
However, there is a pasture saving effect of PROLIQÒ
making more pasture available for milking cows.
[Conducted
by Dr Alistair Nicol, Lincoln University, and Karen Turnbull,
Fonterra Summer Scholar]
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Application of Dexcel Whole
Farm Model to Lincoln University Dairy Farm [2005]
Dexcel has developed
a whole farm model of dairy farms that allows investigation
of the effects of management, climate (including irrigation)
and soil type variability on pasture and animal performance
and farm profitability. The ability to simulate multiple
years allows us to examine risk related to both climate
and prices.
In this study we are
examining three aspects using the Lincoln University Dairy
Farm as a case study. These are the impact of calving
pattern, the decision rules around winter grazing and
spring rotation planning and irrigation scheduling.
(Researchers: Pierre
Beukes and Bruce Thorrold of Dexcel Ltd. Funding
from Dairy InSight and FRST)
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Modelling the
effects of zero-inductions on profitability in dairy
systems [2004]
Inductions are an animal
welfare issue and regulations aim to achieve <2% inductions
on a national basis by 2010. There is a need to
assess the longer-term impacts of alternative reproduction
management strategies on farm economics and their success
in solving the problem of poor reproductive performance.
Dexcel's Whole Farm Model was calibrated against observed
data from Lincoln University Dairy Farm where 11% of the
herd was subjected to inductions in the 2002/03 season,
but a zero-induction policy has since been adopted.
Results from one-year simulations over five different
climate years showed a significant decrease in farm profit
($105/ha, P<0.05) from the benchmark farm with 11%
inductions (following "best practice" guidelines)
to a farm where the later-calvers were culled and replaced
by bought-in early-calving heifers and where stocking
rate was raised moderately (<10%) to compensate for
the higher proportion of heifers in the herd. Multiple-year
simulations reflecting carry-over effects showed that
a strategy with a 10-week mating period, annual culling
of 25% of the herd including all empties and replacement
with synchronized heifers mated to start calving one week
before planned start of calving can match the farm profitability
of the "Induction" strategy if implemented consistently
for 5-8 years. View
the full paper. (PDF, 45 KB).
[Conducted by P C Beukes, B S Thorrold,
M E Wastney, C B Glassey, C R Burke and A M van Bysterveldt,
Dexcel Ltd]
(Funded by Dairy InSight and MAF (SFF))
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Pasture
analysis in relation to the spring dip in milk production
[2007]
This project will investigate
causes of the dip in MS production at LUDF during October
and November. The rate of decline in MS production
is much greater during this period than later in the summer.
We will investigate the extent to which the decline is
related to pasture composition.
The project proposes:
a. more detailed
analysis of pasture composition through [i] sampling pasture
in front of the cows three times each week, and [ii] sampling
from pasture exclosures managed under a constant cutting
regime.
b. to investigate
changes in the production of 'green odour' compounds when
grass is damaged over the period September to December
[may be extended].
Data collection for the
project has been completed and analysis is underway on
a detailed set of pasture analysis at high frequency over
the period September to December 2006. It should
be noted that 2006 was an atypical Spring.
Report - May 2007
Summary
The objective of this project
was a more detailed investigation of the rapid decline
in milk solids production experienced at LUDF during late
October and November in the 2003/04, 2004/05 and 2005/06
seasons. Analysis of a sample of production curves
from dairy farms across New Zealand failed to identify
consistent patterns of ‘Spring milk dip’.
While some farms in each region showed a dip in milk production
during the period of interest it was not as large as that
observed on the LUDF and was not repeatable across years.
2006 was an atypical year at LUDF, with a wet Winter and
cold Spring resulting in high sugar levels, high DM% and
low protein content in the early pasture.
There was no evidence of differences
in pasture composition between cultivars growing at LUDF
(Bealey or Tabu). A ‘Spring Dip’ in MS production
was not observed at LUDF during late October/November
2006. This allowed us to make comparisons of pasture covers
and composition with previous ‘Spring Dips’,
notably the large dip in 2005. The LUDF ‘Spring
Dip’ appears to result from lower pasture covers
in the period soon after peak milk yield and is not related
to pasture composition. It may be more of a feature of
herds that adopt extremely low grazing residuals and so
are more likely to run into low covers at this time, though
national database information did not allow us to verify
this assertion (see above). The project reinforces the
importance of maintaining pasture monitoring during this
busy (mating) period. Further work should focus on ensuring
a reliable indication of pasture covers during this critical
phase of lactation.
[Conducted by
Richard Dewhurst, Jim Gibbs, Lincoln University, Dawn
Dalley, Dexcel Ltd, and Richard Christie, SIDDC.]
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Monitoring
Climate Stress in Canterbury dairy cows [2006]
It is not known whether dairy cows in Canterbury experience
thermal stress during hot, dry days. Measurements are
being made of the diurnal range of changes in core temperature
in dairy cows of differing body condition score (and milk
production) on hot days compared with cool days.
Baseline core temperature
data from individual cows are also being obtained and
variations examined. Climatic data will also be examined
to determine if extreme climatic events can be predicted.
Conclusions:
The potential for thermal
loading on cows waiting to be milked on summer afternoons
appears to be minimal in Canterbury. Likewise, there
appears to be minimal thermal impact on cows caused by
walking distances up to 6 km on summer afternoons in Canterbury.
These conclusions must be tempered by the fact that few
very hot days were encountered during these studies and
both farms had low endophyte pasture. High endophyte
pastures may increase susceptibility to heat stress and
this factor needs to be considered where such pastures
occur. However, the fact that much of the Canterbury
region has experienced only a very few days per year when
THI exceeded a value of 75 in the 5 years from 1998 to
2003 (McLane et al., 2004), and this has continued to
apply in the last 3 summers when temperatures have been
lower than the average (National Climate summaries, NIWA
National Climate Centre, Auckland), indicates that thermal
loads experienced by dairy cows on summer afternoons in
Canterbury are only occasionally going to impose severe
stress on the animals. It is likely that measuring
the thermoregulatory effort required to dissipate thermal
stress of cows by recording their breathing rate will
provide better insight into the questions under study
in this work. This makes development of a compact
recording device for recording breathing rate a primary
objective for the conduct of further studies.
(Dr Graham Barrell and Mark Bloomberg,
Lincoln University, plus Masters student Duncan McLane)
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