Department of Animal Sciences
Quarterly Newsletter Vol. 5 No. 4 Fall 2005
DETERMINING WHEN TO HARVEST STAY-GREEN
Several Florida dairy producers have observed an
increased incidence of digestive upsets, Variable Manure
syndrome and Hemorrhagic Bowel syndrome in their cows in
recent times. These problems have greatly affected the
productivity of such herds, and many producers attribute the
problem to feeding corn silage made from hybrids with high
staygreen rankings. To address this problem, the University of
Florida embarked on a series of studies aimed at
understanding the influence of the staygreen ranking on the
nutritive value of corn hybrids and milk production. This
summary presents the results of the first of those experiments,
which aimed to determine the effect of
maturity at harvest on the nutritive
value and aerobic stability of corn
hybrids differing in staygreen ranking.
One high staygreen corn hybrid
and one average staygreen hybrid with
similar relative maturity (118 d) were
selected from Pioneer Hi-bred and
Sutheut M3k, inc. Croplan genetics hybrids. The high
Dairy Check-Off staygreen hybrids were Croplan
genetics 827 and Pioneer 31Y43, while average staygreen
hybrids were Croplan genetics 799 and Pioneer 32D99. The
four hybrids were grown on four replicate, 1 x 6 m plots. The
hybrids were harvested at 26 (Cut 1), 34 (Cut 2), and 39 (Cut
3) % DM, yield was assessed and some selected plants were
separated into ear and stalk fractions for chemical analysis.
The rest of the forage from each plot was ensiled (15 kg)
within plastic bags in mini-silos for 100 days and then
In the freshly harvested plant, yield was similar at Cuts 1
and 2, and higher at Cut 3. High staygreen hybrids had greater
stalk crude protein concentration, lower stalk DM and lower
stalk sugar concentration than average staygreen hybrids.
Whole plant digestibility was also lower in higher staygreen
hybrids than average staygreen hybrids.
The staygreen ranking or source (seed company) of the
hybrids did not affect silage fermentation, but high staygreen
hybrids had greater crude protein and lower starch
concentrations than average staygreen hybrids. High
staygreen silages tended to be less digestible, than average
staygreen hybrids. This suggests that processing is required to
improve the digestibility of high staygreen hybrids.
Dry matter and starch content increased with maturity
while residual (post fermentation) sugar and crude protein
content decreased. Silage pH increased with maturity while
ammonia-N, lactic acid and acetic acid concentrations
decreased. Yeasts increased with maturity while molds
decreased but aerobic stability was unaffected by maturity.
This study therefore indicates that staygreen corn hybrids
should be harvested at the intermediate maturity stage (34%
DM, Cut 2) to optimize nutritive value and yield. High
staygreen hybrids seem more likely to have lower DM and
sugar concentrations than low staygreen hybrids and such high
staygreen hybrids should be processed to improve their
digestibility and ensure proper starch release from the kernel.
Staygreen ranking did not affect the normal fermentation
indices. Further work on the effects of staygreen on milk
production in cows is currently being done.
For more information, contact Dr. Adegbola Adesogan by
email at email@example.com, or (352) 392-7527.
David R. Bray
The latest National DHI Somatic Cell Count (SCC) data
is out and congratulations to the Florida dairymen for having
the greatest reduction in SCC in the nation, dropping from
633,000 to 475,000 even with all the hurricanes that hit in
2004. Georgia also reduced their counts more than 60,000. It
is important to keep our SCC on a downward trend to protect
our market. We still have to contend with the PETA Puss
heads and those who get paid to lower their counts and can't
understand why we aren't as low as they are "up north".
Keeping SCC low in the Southeast is an expensive ordeal.
We don't get paid for it, our hot, humid and wet conditions
increase mastitis rates, which increase treatment costs and
dumped milk. Florida dairymen have been almost free of
contagious mastitis organisms for a few years, which means
we have been able to milk cows well enough to do that.
Increasing cow comfort will pay for itself with more milk
production and better animal health due to less stress on our
animals. I think that the future of dairy cow health in the
Southeast will improve because more cows will be in barns
due to environmental concerns. This will allow us to take
better care of our cows, and we better take better care of the
cows to pay for the barns.
Every dairyman's goal should have the lowest SCC
as they can economically produce, and the state to have a SCC
average below 400,000. We should also recognize that we
still have many dairymen who do not have the facilities and or
are at a point in their life that they don't want to spend huge
amounts of money to upgrade their dairy. That will not help
decrease our average, but if they produce milk within the legal
limits and want to stay in the dairy business, that's their right.
Right and wrong ways to lower your SCC
There a variety of ways to have a low bulk tank SCC,
some are economical, some are not.
1. You milk clean dry udders, post dip, dry treat all cows
going dry, treat clinical mastitis as it appears, keep
records so you can cull chronic cows (those that are
treated more than five times in a lactation), keep cows
clean, cool and comfortable, keep milking equipment in
good repair. This method should be most economical and
2. You think you are doing # 1 above, but your help is not
doing it. Once your SCC is high you try to find high
animals and treat them, and treat them again and again,
not knowing if they are new cases of mastitis or chronic
cows. This is not an economical method and is
3. You don't know what is happening, same as above in # 2.
4. You have a low SCC because you over-treat. You treat
every high cow on the monthly SCC list every month
whether she needs it or not. This will give you a low SCC
and a high pot herd and is very expensive.
Once the SCC elevates or the number of clinical mastitis cases
increase you need to know why. If the cows are outside and it
is wet and summer, that should not be a surprise. It is part of
your plan: you are not paying for a barn but are paying the
cost of not paying for a barn. The secret here is to keep lots as
clean as possible and knowing that this will happen every
year, you need to have your SCC at or below 500,000 before
summer starts so you stay legal.
What size should my pot herd be?
Answer: as small as possible. There are a variety of goals
or suggestions. I have data on 20+ large dairies in another
state and the SCC of these herds ranges from 150,000 to
550,000 and a range of 1.0 % to 7.7% of the cows are in the
mastitis herd per month. Some of low SCC herds had a high
treatment rate and vice versa.
1. Clean the teat ends with alcohol pads first, use only
commercial tubes to put anything in the udder, NO
2. Follow directions on the box; if it says treat every 12
hours that means every 12 hours, if you can't treat every
12 hours, use a tube that is for 24 hours. You only make
resistant bacteria by the wrong time of treatment.
3. If you are going to use extended treatments, check with
your veterinarian for options and milk withholding times.
4. Keep records.
5. Cull chronic cows, five episodes of mastitis per lactation
is the end of the productivity of that cow.
6. We suggest you have a bulk tank sample analyzed, large
herds (1000+ cows) done every week, smaller herds once
a month or more often if you purchase replacements. A
lot of those "Yankee" cows and fresh heifers are rotten.
This will inform you if you have any contagious
pathogens that will pass from cow to cow, or
environmental pathogens that don't pass from cow to
Need help or got any questions?
If you have a mastitis problem and want some help, give
me a call or e-mail: Dave Bray, (352) 392 5594,
MANURE MANAGEMENT SUSTAINABLE
Ann C. Wilkie
Check out the latest publications on the subject of manure
management at http://dairy.ifas.ufl.edu/manure.html. These
publications include papers by Dr. Ann C. Wilkie, describing
the benefits of anaerobic digestion technology, design and
process considerations for anaerobic digestion of dairy
manure, and anaerobic digestion of flushed dairy manure
using a fixed-film digester. There is also a report available
from the National Dairy Environmental Stewardship Council,
a collaboration between dairy producers, environmental
organizations, U.S. Department of Agriculture, U.S.
Environmental Protection Agency and academics which was
formed by Sustainable Conservation and Environmental
Defense. Art Darling and Ann Wilkie are council members.
The report, entitled "Cost-effective and Environmentally
Beneficial Dairy Manure Management Practices," outlines
how innovative dairy producers are transforming manure into
a valuable farm asset. The report provides detailed examples
of cost-effective manure management strategies to assist
producers in matching manure nutrients to crop needs and
capturing nutrients in dairy manure. The report also includes
implementation strategies and a list of funding resources
available to assist dairy producers with sustainable manure
management. Paper copies of the report are available from
Dr. Ann Wilkie is in the Department of Soil and Water
Science, University of Florida. She can be reached by e-mail
at acwilkieitmail.ifas.ufl.edu, or call her at (352)392-8699.
COMPARING THE ECONOMIC IMPORTANCE OF
GENETIC IMPROVEMENTS IN MILK PRODUCTION,
REPRODUCTION, AND PRODUCTIVE LIFE
Albert de Vries
Florida dairy producers have access to genetic evaluations
for many traits that are economically important. These traits
are combined in economic selection indexes to rank bulls and
cows for total profitability. Currently, USDA-AIPL calculates
the genetic merit of 11 economically important traits for bulls
and cows 4 times per year and combines them into 3 lifetime
merit indices: net merit (NM$), cheese merit (CM$), and fluid
merit (FM$). A lifetime merit index is the expected total
additional profit, in dollars, during a cow's lifetime as
compared to the total profit of a breed average animal.
Lifetime is considered to be 3 lactations. The true economic
values of genetic improvement for individual farms depend
considerably on the market prices of milk, fat, feed, heifers,
cull cows, etc. This article discusses how USDA-AIPL arrives
at its economic values for milk production, reproduction, and
productive life and how these economic values may vary on
Genetic merit of a trait in mature animals can be
expressed as predicted transmitting ability (PTA). The PTA is
half an animal's expected breeding value, equivalent to the
genetic worth that is expected to be transmitted to its
offspring. PTAs are expressed as differences from the breed
base. The breed base is equivalent to the genetic merit of an
average animal in the population and is occasionally
recalculated by USDA-AIPL (once every 5 years).
The PTA for milk production is divided in PTAs for milk
yield, fat, and protein. All are measured in total pounds per
305-day lactation in a mature cow. Thus, a PTA milk of 1
implies one pound more milk in 305-days compared to the
breed base. The expected extra lifetime milk production is 3
USDA-AIPL provides genetic evaluations for daughter
pregnancy rate (DPR) as a measure of reproductive efficiency.
DPR is defined as the percentage of nonpregnant cows that
become pregnant during each 21-d period. Pregnancy rates on
Florida dairy farms range from below 10% to over 20%. An
increase in the PTA DRP of 1 implies a one percentage unit
better pregnancy rate, say from 15% to 16%. Each increase of
1 in PTA DPR equals a decrease of 4 PTA days open per
Productive life (PL) refers to the time between first
calving and removal from the herd by voluntary or involuntary
culling, or death. The PTA PL is a measure for total added
lifetime (not per lactation), expressed in months.
Table 1 shows the variation in PTAs for milk, fat, protein,
DPR and PL in the August 2005 USDA-AIPL Holstein Sire
Summaries (200 sires).
Table 1. Minima and maxima of PTAs for milk, fat, protein, daughter
pregnancy rate (DPR), and productive life (PL) in the August 2005
USDA-AIPL Holstein Sire Summaries.
PTA PTA Milk PTA Fat PTA Protein PTA DPR PTA PL
(305-d lbs) (305-dlbs) (305-dlbs) (%) (months)
Min. 285 15 16 -2.1 -2.0
Max. 3110 102 81 2.7 5.0
The amount of genetic progress in the daughter does
depend on the environment and management of the farm.
Typically, well managed herds will see larger responses than
herds where the environment and management is not as
favorable for cows. But the genotype by environment
interactions are not large enough to justify separate genetic
evaluations for each production system (J. Dairy Sci. 87:501).
In other words, the top bulls remain the top bulls regardless of
the type of herd they are used in.
Each trait in the lifetime merit indices is assigned an
economic value by USDA-AIPL (Table 2). This value allows
dairy producers to compare the importance of improvements
in say milk production with the values of improvements in
DPR or PL. An economic value is the profit change when a
given trait changes by one PTA unit, and all other traits in the
index remain the same. The only difference between NM$,
CM$ and FM$ is the way the milk is valued. The FM$ index
is most appropriate in markets where milk is sold for fluid
consumption such as Florida. For example, the expected value
of a daughter of an average cow and a Holstein sire with +70
lbs for protein, +80 lbs for fat, +2000 lbs for milk, +2.5
months for PL, and +0.3 % for DPR under FM$ pricing is 70
x $1.33 + 80 x $2.54 + 2000 x $0.051 + 2.5 x $26 + 0.3 x $17
= $574 compared to a breed base average animal.
Table 3 lists the USDA-AIPL prices for protein, fat, and
milk yield and the resulting economic values for these
production traits. The economic values are calculated as
(component price feed cost) x 0.89 x 3 lactations (0.89
converts ME milk to actual milk). For example, 1 lbs of fat
per lactation is worth $1.30 but the feed cost to produce it is
$0.35. Therefore, profit per lactation is on average ($1.30 -
$0.35) x 0.89 = $0.85 and for all 3 lactations (lifetime) it is
$0.85 x 3 = $2.54.
Table 2. Economic values of the 11 traits in the net merit (NM$),
fluid merit (FM$) and cheese merit (CM$) indices as calculated by
USDA-AIPL in 2005.
Economic Value ($/PTA unit)
Trait PTA Units NM$ CM$ FM$
Protein Pounds 4.81 6.68 1.33
Fat Pounds 2.54 2.54 2.54
Milk yield Pounds 0 -0.056 0.104
Productive life Months 26 26 26
Somatic cell score Log -166 -166 -166
Udder Composite 33 33 33
Feet/legs Composite 15 15 15
Body size Composite -12 -12 -12
Daughter pregnancy rate Percent 17 17 17
Service sire calv. difficulty Percent -5 -5 -5
Daughter calv. difficulty Percent -5 -5 -5
Table 3. Milk component prices and economic values used by
USDA-AIPL for NM$, CM$ and FM$.
Milk yield Fat Protein
Index ($/lbs) ($/lbs) ($/lbs)
NM$ price 0.012 1.30 2.30
CM$ price -0.009 1.30 3.00
FM$ price 0.051 1.30 1.00
Feed cost -0.012 -0.35 -0.50
Lifetime (# lactations) 3 3 3
NM$ (lifetime) 0.000 2.54 4.81
CM$ (lifetime) -0.056 2.54 6.68
FM$ (lifetime) 0.104 2.54 1.34
One pound of milk with 3.5% fat and 3.0% protein is
worth 1 x $0.051 + 0.035 x $1.30 + 0.03 x $1.00 = $0.1265.
The feed cost to produce this pound of milk are 1 x $0.012 +
0.035 x $0.35 + 0.03 x $0.50 = $0.039. The economic value
of a pound of actual milk with 3.5% fat and 3.0% protein in 1
lactation (305-days) in the FM$ index is therefore ($0.1265 -
$0.039) x 0.89 = $0.078 or $0.233 lifetime (3 lactations). In
other words, USDA-AIPL assumes that the economic value of
marginal milk income over marginal feed cost is $0.078 per
pound. The average feed cost on dairies in Florida ranges
from $0.06 to $0.08 per pound of milk. At a $0.17 per lbs
milk price, this means an income over feed cost in the range of
$0.09 to $0.11. The marginal value of an extra pound of milk
in Florida is therefore probably significantly higher than
$0.078. If this value is say $0.10, then the lifetime value of
milk (3.5% fat and 3.0% protein) is $0.330 instead of $0.233.
The PTA DPR is calculated from information on days
open. USDA-AIPL assumes a day open costs $1.50. This
does not include the increased cost for cow replacement due to
reproductive failure because that is included in the cost of
productive life. The lifetime value of 1 day open per lactation
is 2.8 x $1.50 = $4.20. The factor 2.8 is based on the
assumption that fewer breeding are attempted in the third
lactation and includes an adjustment for heifer fertility.
Because 4 days open is equal to 1% DPR, the economic value
of 1 unit PTA DPR is 4 x $4.20 = $16.80, or rounded $17.
This is the DPR value in Table 2.
Many studies have shown that the value of a 1 percentage
unit increase in pregnancy rate increases when the average
pregnancy rate in the herd is lower. Figure 1 shows some
estimates of the change in lifetime profit per cow per
percentage unit change in pregnancy rate for a simulated
typical Florida herd. Pregnancy rate was varied from 10% to
34%. The economic value of a one percentage unit change in
pregnancy rate ranged from $7 to $65 when the cost of
increased cow replacement was included. However, if the cost
of increased cow replacement was excluded, then the change
in lifetime profit ranged from only $6 to $25. These latter
values can be compared to the USDA-AIPL estimate of $17.
The economic value of genetic improvement in DPR clearly
depends on the average pregnancy rate in the herd and can be
significantly higher or lower than $17.
5% 10% 15% 20% 25% 30% 35%
Figure 1. Change in lifetime profit per cow for a change of one
percentage unit in pregnancy rate. The top curve (0) is change in
lifetime profit including the cost of cow replacement. The bottom
curve (0) is the change in lifetime profit per cow excluding cow
replacement cost. The USDA-AIPL estimate (-) of $17 also
excludes cow replacement cost. Lifetime is 3 lactations.
The USDA-AIPL estimate of the value of productive life
accounts for the opportunity cost of delayed replacement
because extending the productive life of one cow denies the
opportunity to make a profit with a replacement animal in the
same slot. The basic calculation is (heifer price beef price) /
lifetime. In 2000, USDA-AIPL assumed a heifer price of
$1240 and a beef price of $525. The economic value of 1
month PTA PL could therefore simply be estimated as ($1240-
$525) / 30 = $24, but USDA-AIPL used $28 per month in
2000. Currently, the economic value of 1 month PTA PL is
set at $26 per month. This value can be considered the
straight-line monthly depreciation of a dairy cow. Table 4
shows how the economic value of 1 month PTA PL varies
from $16 to $59 for different heifer prices and annual cull
rates. Lifetime (in months) is calculated as 1 / annual cull rate
Table 4. Estimates of the economic value of productive life for
various heifer prices and herd lifetimes.
Beef Heifer 25% 35% 45% Annual cull rate
price price 48.1 34.3 26.7 Lifetime (months)
525 1300 $16 $23 $29
525 1700 $24 $34 $44
525 2100 $33 $46 $59
Because the economic values in the lifetime merit indices
in Table 2 are all expressed as lifetime benefits, we can easily
compare the relative value of 1 unit change in milk
production, DPR, and PL. Table 5A lists the economic values
for these traits for USDA-AIPL and two hypothetical farms A
and B. Farm A has a low cull rate, raises its own heifers and
its pregnancy rate is high. Farm B has a higher cull rate and a
lower pregnancy rate. The lifetime marginal value of 1 lbs
milk in 305-days is assumed to be $0.33. Table 5B is a
comparison of the relative values of a 1 unit increase in one
trait compared to increases in other traits. For example, using
the USDA-AIPL economic values, the value of 1 month extra
PL is equivalent to 112 lbs more milk (3.5 % fat, 3.0%
protein) per 305 days in lactation.
Table 5A. Economic values for productive life (PL), daughter
pregnancy rate (DPR), and milk according to USDA-AIPL and for 2
hypothetical farms A and B.
USDA-AIPL Farm A Farm B
1 month PL $26 $16 $36
1 % DPR $17 $10 $24
1 lbs milk in 305-days* $0.233 $0.33 $0.33
* Milk with 3.5% fat and 3.0% protein
Table 5B. Relative value of improvements in 1 unit PTA productive
life (PL), daughter pregnancy rate (DPR), and milk according to
USDA-AIPL and for 2 hypothetical farms A and B.
USDA- Farm A Farm B
1 month PL is worth: 111.59 48.48 109.09 lbs 305-dmilk*
1 month PL is worth: 1.53 1.60 1.50 % DPR
1 % DPR is worth: 72.96 30.30 72.73 lbs 305-dmilk*
* Milk with 3.5% fat and 3.0% protein
Ideally, every dairy should use its own economic values
to rank bulls and cows for lifetime merit. But the effect of
using different economic values for PL and DPR on the
ranking and merit of the top 200 all Holstein sires evaluated
by USDA-AIPL for FM$ in August 2005 is minor. For
practical purposes, the USDA-AIPL ranking of sires seems
adequate under conditions in Florida.
UF DAIRY CALENDAR OF EVENTS
The Southeast Dairy Management Conference will be
held in Macon, Georgia, on November 9-10, 2005. The event
is co-sponsored by the University of Florida. The program is
available on http://dairy.ifas.ufl.edu. For more information,
contact Lane Ely, University of Georgia, (706) 542-9107,
The 17th Florida Ruminant Nutrition Symposium will
be held at the Best Western Gateway Grand in Gainesville on
February 1-2, 2006. For the program and to register, visit
http://conference.ifas.ufl.edu/ruminant/index.html. For more
information, contact Charlie Staples, firstname.lastname@example.org,
The 3rd Florida Dairy Road Show is planned at the
UF/IFAS Extension Offices in:
- Okeechobee, FL, Tuesday February 28, 2006
- Mayo, FL, Wednesday March 1, 2006
- Chipley, FL, Friday March 3, 2006
- Tifton, GA, Tuesday March 7, 2006
The meetings will run from 10 AM to about 3 PM. For more
information, contact Brent Broaddus, (813) 744-5519 ext 132,
babroaddusAimail.ifas.ufl.edu, or Albert de Vries, (352) 392-
7563, devries(ianimal.ufl.edu, or your local UF/IFAS Dairy
The 43rd Florida Dairy Production Conference is
planned for Tuesday May 2, 2006, at the Hilton UF
Conference Center in Gainesville, FL. For more information,
contact or Albert de Vries at devries(ianimal.ufl.edu, (352)
The 2006 Corn Silage/Conserved Forage Field Day is
planned for Thursday May 25, 2006 at the Plant Science and
Education Unit in Citra, FL. For more information, contact
Jerry Wasdin at email@example.com or (352) 392-1120.
The Florida Dairy Update newsletter is published quarterly by the University of Florida, Department of Animal Sciences, as an educational and informational service.
Please address any questions, comments or suggestions to Albert de Vries, Editor, Dairy Update, PO Box 110910, Gainesville, FL 32611-0910.
Phone: (352) 392-7563. E-mail: firstname.lastname@example.org. UF/IFAS Dairy Extension website: http://dairv.ifas.ufl.edu. This issue was printed on October 10, 2005.