Rethinking Milk Fever Prevention

Oh the stories we could tell about the numerous milk fever cases we have seen.  Typically, we can I.V. uncomplicated cases and look like a hero.  But the memorable cases span from the cow that vomited her rumen contents and took her last breath to the cow that hops up as soon as you lay a hand on her after receiving 3 tubes of calcium over a 3 hour period before you arrived.  Both wasted trips, or were they?  We now have time, because the cow is either dead or standing there after trying to die, to discuss with the client how we can easily treat, or better yet, prevent milk fever.     

When you think of milk fever, you think of calcium.  We treat milk fever with calcium and the cow typically responds quickly and successfully.  Even though milk fever is easy to treat, the disease is costly with an estimated cost of $350/case.  Hypocalcemia typically leads to or is a forewarning of transitional disease.  The  clinically weaker and immuno-suppressed cow is at greater risk for injury, mastitis, retained placenta, and metritis.  Therefore, we need to strive for a low herd incidence.  A herd level milk fever incidence should be less than 3%.  This article will analyze the impact of nutrition on the incidence of milk fever.

To achieve a low incidence rate, we need to focus on prevention.  An obvious strategy to decrease milk fever is to maintain pre-fresh dry matter intakes and to lessen the degree of dry matter intake decline prior to calving through adequate bunk space (30” per head) and cow comfort.  Additionally, the dry cow should consume a ration with excellent forage quality and adequate metabolizable protein (>1200g/day) without exceeding the NEl requirement of 14-15 Mcal per head per day (0.64 Mcal NEl per pound of DM).  Another milk fever control strategy that has been incorporated in pre-fresh rations and extensively analyzed is the DCAD (Dietary Cation Anion Difference) Theory which focuses on Calcium, Magnesium, Potassium, Sulfur, Sodium, and Chloride dietary levels. 

Lean et al analyzed 137 trials with 2545 calvings to determine which minerals had the greatest influence on the development of milk fever.  The results will surprise you!  First, picture a bell curve. 

Milk fever incidence in response to varying dietary calcium concentrations as predicted by Model 1.

(Lean et al Journal of Dairy Science 89:669–684 2006)

When analyzing the influence of calcium as a % of dry matter intake on milk fever incidence, the highest incidence of milk fever occurred at calcium levels between 1.1-1.5% dry matter with decreasing incidence below 1.1%DM and above 1.5%DM.  Lean saw a greater benefit to lowering pre-fresh calcium levels to <0.5% dry matter. 

Second, the meta-analysis revealed a significant influence of magnesium on the incidence of milk fever.  In fact, the influence of magnesium was significantly more important than potassium!  The study showed a greater benefit to formulating pre-fresh rations with magnesium levels >0.4% dry matter.  We understand many farms have seen a higher milk fever incidence with high potassium forages.  The greater incidence was likely a result of insufficient dietary magnesium levels!  Low potassium levels are often recommended, but the agronomic negatives are more significant to the dairy’s bottom-line than the metabolic benefit to the cow.  Lowering grass potassium levels significantly reduces yields (correspondence with Dr. Ferguson, University of Pennsylvania).   

With the information presented in the meta-analysis, we recommend keeping pre-fresh calcium levels low, <0.5% dry matter, potassium levels as low as physically possible for the farm, and, more importantly, magnesium levels >0.4% dry matter. 

Please work closely with your nutritionist and veterinarian, ensuring excellent communication between all team members, to optimize the health and productivity of your transition cows.   

Get the Most Out of Your Timed A.I. Investment

Many risk factors impact the success of any breeding program.  For instance, management segments on the dairy are interdependent.  Therefore, changes in one segment will directly or indirectly impact another segment.  Timed A.I. offers additional challenges associated with protocol compliance, scheduling, and time management, which are critical to success.  If implemented correctly in a herd that has minimized management challenges, timed A.I. can increase pregnancy risk and improve your bottom line.  The key is to identify the risk factors on your farm that impact pregnancy risk and initiate change in order to get the most out of your timed A.I. investment.

           

Why should you be motivated to focus on reproduction?  The ultimate goal of the reproductive program is to achieve a pregnancy in order to maintain milk production and replacements.  Ten Percent of your cows should calve every month to maintain consistent milk production.  Your greatest return on investment is milk produced during the first 100 days in milk when the return is 3:1!  Additionally, reproduction significantly impacts culling strategy. With more replacements, culling options increase. 

           

In order to keep days in milk low, cows need to efficiently conceive in a timely manner after a clearly defined voluntary waiting period.  Optimizing pregnancy risk achieves this objective.  Pregnancy Risk is defined as the probability that an eligible open cow will become pregnant in the next 21 days, or more simply, the number of pregnancies over a 21-day period divided by the number of eligible cycles over the same 21-day period.  The average pregnancy risk in Pennsylvania is 14%.  The goal pregnancy risk is 22-25%! 

Studies have analyzed the value associated with pregnancy risk.  A one percentage point increase in pregnancy risk is valued at $15-35 per cow per year.  The further you go below the goal pregnancy risk of 22-25% the higher the value of increasing pregnancy risk.  Consider this example, a 150-cow herd with an average pregnancy risk of 14% could potentially see an additional profit of $15,750 by increasing pregnancy risk to 17% (3 points*$35/cow/year*150cows).  The pregnancy risk value is partially dependent on decreasing days open which has an estimated cost of $2-6 per cow per day open in addition to the cost associated with reproductive culling.

Are you motivated to invest in change?  Now let’s discuss getting the most out of your reproductive investment.  First, you must start with dairy management basics because all management segments are interdependent.  Optimize transitional health and decrease body condition loss post-calving.  Promote cow comfort and decrease social stress.  Focus on nutrition and work closely with your nutritionist and agronomist to maximize forage quality.  Decrease lameness and promote milk quality.  Work with your veterinarian to design a vaccination program specific for your dairy.  A problem in any of these areas re-partitions nutrients away from reproduction, negatively impacting fertility. 

Strict Adherence to Program Compliance is critical to enhancing timed A.I. conception risk.  A successful timed insemination program is dependent upon strict protocol compliance.  Protocol drift will result in lower conception rates and wasted opportunity.  Consider this Ovsynch Compliance Example (based on % compliance per injection) that proves Mistakes Multiply:

90% GnRH1 x 90% PGF2a x 90% GnRH2 = 73% !

With the investment you place in drugs, supplies, and labor expenses, a 73% compliance rate is not tolerable.  Hormones used in your reproductive program need to be labeled and stored properly.  Be able to control and monitor drug inventory to monitor correct usage rates.  Injections must be administered according to labeled instructions (route of administration and dose) on schedule.  Use color-coded bottles and different sized syringes to make hormone identification easier.  Make sure the correct hormone is administered and the correct cow inseminated at the prescribed times.  Timing is extremely critical.  Cows enrolled in the program should be easily identifiable and pregnant cows should be clearly recognized. Give employees ownership of the program to encourage compliance and accountability.  Use the smallest needle allowed, 18 or 20 gauge 1.5 inch needle, so that the injection is placed deep in the muscle with zero hormone loss from the injection site.

The cow must be inseminated properly by a trained technician.  Employees should be retrained annually to prevent protocol drift.  Technician conception rates can be monitored through various computer programs.  Make sure semen is handled according to the recommendations of the bull stud.  Check thermometer accuracy.  Timing and maintenance of proper temperature during temperature extremes is critical.  Analyze ways to become more efficient by decreasing distance between semen prep and the cow. 

An all-encompassing discussion about estrous synchronization protocols is beyond the scope of this article.  However, we need to talk about modifications to Presynch and Ovsynch that studies have proven to increase conception risk.  Remember this concept - The optimal day of the reproductive cycle to start Ovsynch is 6-7.   The first follicular wave is more consistent and 2 CL’s are created which means more progesterone exists to optimize fertility.  Using Presynch (Pg-14days-Pg-14days-Ovsynch) to set-up Ovsynch for first service has been shown to increase conception rates by 12%.  However, the standard 14 day interval between the second prostaglandin injection and start of Ovsynch is not consistently within the optimal 6-7 day window of the reproductive cycle.  Therefore, decreasing the interval between the second Presynch prostaglandin injection and the start of Ovsynch from 14 days to 11-12 days has been shown to further increase conception rates by 6 percentage points.

Now let’s discuss Ovsynch and Cosynch.  First, preliminary assumptions are that 56-hour Ovsynch (G-7days-PGF-56hrs-G-16hrs-Breed) has higher conception rates than the typical 48-hour Ovsynch protocol.  Unlike Ovsynch where cows are bred 16 hours after the second GnRH injection, Cosynch cows are bred when they are injected with the second GnRH injection eliminating another handling.  So, Cosynch is more convenient, but does it pay?  Numerous studies have repeatedly shown an 8-10% improvement in conception rates at the optimal time for AI which is 16 hours after a GnRH injection, like 56-hour Ovsynch, compared to a Cosynch protocol.  Conception Rate improvements are seen regardless of a Presynch/Ovsynch first service or a Resynch service.  Considering the statistically significant difference and investment made into the reproductive program, the decision to use Ovsynch over Cosynch should be clear.

We should finish up by talking about Resynch conception rates.  Resynchronization programs are timed re-insemination protocols that insure all open cows are re-bred within a defined interval with the goal of decreasing the interestrous period (time frame between breedings).  In this article, we will simply discuss Resynch in relation to a standard 56-hour Ovsynch protocol. Many Resynch protocols exist.  The most common is an Ovsynch protocol initiated a week before pregnancy check.  Resynch conception rates are typically lower than 1st service conception rates with a Presynch-Ovsynch protocol.  Many studies have analyzed the optimal time to start Resynch.  Conception rates for Resynchs initiated on days 32-33 (38%) post-A.I have been consistently higher than Resynchs initiated on days 19 (23%), 21, and 26 (34%) post-A.I.  The difference between d26 cows and d33 cows is likely due to a greater period to allow natural embryonic death.  Studies have shown that 12% of all pregnancies between 30-42 gestation result in natural early embryonic death.  Consequently, you have 2 preg check options when initiating Resynch on day 32-33 post-A.I.  You could Preg check on day 32 or 33 post-A.I. and give GnRH1 to all open cows and complete Ovsynch.  Or, you could give GnRH1 on day 32 or 33, preg check on day 39 or 40, and give PGF2a to all open cows and complete Ovsynch.  Consider using CIDR’s in Resynch-restarts associated with cystic cows and cows without CL’s.  When performing early open tests, it is very important to recheck pregnancy ~60 days gestation.

           

As you can see, many factors impact your reproductive investment.  Identify potential risk factors in management areas that directly and indirectly impact reproduction.  Focus on protocol compliance and eliminate protocol drift.  Finally, follow the data and use proven protocol modifications that enhance conception rates. 

14-11day Presynch / 56-hr Ovsynch /  Day 32 Resynch

	Sunday	Monday	Tuesday	Wednesday	Thursday	Friday	Saturday
Week 1				PGF (pm)
Week 2
Week 3				PGF (pm)
Week 4
Week 5		GnRH (am)
Week 6		PGF (am)		GnRH (pm)	Breed (am)
Week 7
Week 8
Week 9
Week 10
Week 11		GnRH (am)
Week 12		PGF (am) Preg Check		GnRH (pm)	Breed (am)

Heat Abatement

It is never too early to discuss heat abatement strategies to help prevent the summer-related reproduction and milk production slump.  Too often we step onto farms in the middle of summer and see broken and  misaligned fans, clogged sprinkler nozzles, poorly maintained curtains, and dirty inaccessible water troughs.  We see fantastic heat abatement strategies for milk cows, while dry cows suffer through the summer with minimal heat abatement.  Studies, especially coming out of Israel, show a significant improvement in lactational performance by providing heat abatement for your dry cows.  Remember, a lactating dairy cow's optimal environmental temperature is between 40-60F. The purpose of this article is to show you graphically through some cool Dairy Comp 305 graphs, the impact of summer heat on a herd representative of herds in our practice region.  Attention will also be given to at-risk sub-populations in the herd who have the greatest risk for summer-related culling.  The impact analysis will then lead into a discussion of heat abatement strategies that can be implemented in your herd now before summer arrives.

    

The example herd has an annual herd 21-day pregnancy rate of 19%.   19% is a good preg rate, however, the goal is 21-24%.  The problem occurs over the summer when the preg rate lowers to 11%.  Interestingly, if this herd would average 30 pregnancies per 21-day period, annual preg rates would reach 21%.  Two components affecting preg rates are insemination rates and conception rates.  As you can tell, insemination rates remain the same mainly because this example herd utilizes presynch, ovsynch, and resynch.  Conception rates take the dive during the summer, staying below 26% from June-August.                                                             

Conception Rates

Obviously, heat will lead to reproductive problems.  However, reproductive problems are secondarily affected by other health problems that decrease conception rates.  For instance, over summer the example herd experiences an increase in mastitis, DA’s, and abortions. 

     

So why do abomasal displacements increase during the summer?  The problem can actually be related to reproductive problems that occurred during the previous summer.  Reproductive recovery occurs ~60 days after the last incidence of heat stress which usually occurs in early-to-mid fall.  A transitional bottleneck results as these cows enter the close-up and fresh cow pens together the following summer.  Thus, overcrowding stress and all the problems associated with heat stress meet leading to transitional problems that are repeated year end and year out until heat abatement management is instituted in order to break the cycle. 

    

Heat stress will affect certain herd sub-populations more than others, increasing the risk of being culled.  These at-risk herd groups include fresh cows, sick cows,  lame cows, lactation 3+ cows, and open cows >150 days in milk entering summer heat.  In the example herd, all lactation groups experienced a production decline during the first period of heat stress.   L1 and L2 cows quickly rebounded, however, the L3+ group never rebounded and they continue to hold the herd production average down.  L3 cows should be pulling the average up.  Open cows >150 DIM are at greater risk for reproduction–related culling.  Cows freshening between months 1-8 have a greater risk for culling because a greater percentage of animals are open after 380 DIM which can be graphically depicted with a survival curve.  Cows calving between months 9-12 have a survival curve that infers a decreased risk for culling.  So what’s the difference?  Open cows entering summer and summer fresh cows have a greater risk for culling.

    

Asides from heat-related reproductive slumps, heat stress will affect other areas of management as well.  Milk production drops 10+%, dry matter intakes drop 10+%, and disease rates increase.  Additionally, heat stress affects dry cows.  Heat stress will reduce birth weights 10%, decrease milk production in the subsequent lactation 12%, decrease colostrum quality by reducing IgG concentrations in colostrum causing failure of passive transfer and sick calves, and leads to more calving problems and transitional disease.

    

So what can we do to save these at-risk cows?  The following list provides some recommendations:

Water:

·        Water consumption increases to 50-60 gallons/head/day during the summer.  Therefore, increase flowrates! 

·        Check your water quality twice per year for minerals, pH, and bacteria.  An agricultural system demands a water chlorination system!

·        Thoroughly clean with chlorinated solution at least once per week.  Dump troughs daily.

·        Provide at least 2.5 feet water trough perimeter for every 10 cows.  Single holed waterers are too limiting and have no place in cow pens.  Minimum of 2 water troughs per group.  

·        Position water troughs close to parlor exit lanes and within 50 feet of the feedbunk

·        Make water troughs easily accessible with limited restrictions.  Position in a shaded, well-ventilated area with good footing.  Ensure that cow flow is not disrupted, allowing adequate room for cows to back-up and walk past (14 feet crossovers).   

Fans:

·        Should run continuously over 70F providing 4-5 mph airspeed over the feedline and freestalls.

·        Spaced every 10 feet multiplied by fan diameter.  Fans 48 inches and larger should limit distance to 30 feet.   

·        Fan Maintenance:  Poor maintenance can reduce efficiency by 40%!

o   Check proper engine function  

o   Clean blades and cages.  Fans are not bird housing 

·        Position fans at a 30 degree angle.  Aimed towards the bottom of the next fan

·        Position over both feedline and freestalls in the direction of the prevailing winds.

·        No more than 8 feet high

·        Holding pens:

o   One 36 inch fan for every 10 cows or every 150ft2

o   Mount at front of holding pen with airflow towards back of pen

o   Mount fans 3 feet apart.

Sprinklers:

·        Goal:

o   To soak the cow to the skin and stop to allow evaporation (maximized by fans) before the beginning of the next cycle.

·        Prior to the warm season, flush system and clean nozzles.

·        Feedline:

o   Deliver 0.33 gallons/cow/cycle

o   Space nozzles every 6-8 feet and mounted no more than 6-7 feet off the floor.

o   Frequency:

§  >74F = 1-3min.  On every 15 minutes

§  >80F = 1-3min.  On every 10 minutes

§  >90F = 1-3min.  On every 5 minutes

·        Holding Pen:

o   Area of greatest heat stress

o   System capacity = 1 gallon per 150ft2 (10 cows)

o   Mount 8-10 ft above the floor

o   An umbrella sprinkler system appears to be most efficient

o   Frequency:

§  >70F = 1-3min.  On every 6 minutes

Facilities: 

• Facility design:  open sidewalls – 14-16’; ridge opening – 2”/10’ barn width; eave opening – 1”/10’ barn width
• Focus on facility dimensions: Provide enough pen space to accommodate the largest yearly calving slug.  As the Wisconsin data has shown us, 30” per head feedbunk space is imperative for transition cows and comingled heifers with mature cows.  Provide 150’ bedpack space. 
• Heat stress will impair foot health, leading to lameness.  Therefore, we need to encourage cows to “get off their feet!”  Lying times increase when the freestalls possess the correct dimensions and, perhaps, more importantly, a comfortable stall surface.  Clean, cool, deep-bedded sand is considered the best bedding material providing adequate traction and drainage and reduction in bacteria exposure (heat stress will increase mastitis risk) if maintained properly.  Next, take measuring tape and identify your freestall dimension limitations assessing freestall width (>48-50”), neck rails (height is 48” above surface and 66-72” from back of the curb), brisket locator (68-72” from back of the curb and no more than 4” above stall surface), and front of stall (open 42” above stall surface).
• Change and add bedding more frequently.  Bacterial growth increases dramatically during warmer temperatures.  If using organic bedding such as sawdust, straw, or manure solids, add bedding every 48 hours.
• Manure and urine volumes increase due to higher water consumption.  Also, sprinklers add a significant volume of water to the alleyways.  Therefore, you need to scrape the alleyways more frequently in order to reduce mastitis risk and to control heel warts and foot-rot.

Nutrition:

• Minimize acidosis by decreasing sorting, providing 2” effective fiber source.  Also, use bicarb
• Maintain optimal dry matter intake:  Feed more frequently with a priority to provide fresh feed during the cooler am, increase push-up frequency, provide comfortable and cool environment, minimize overcrowding
• Minimize BCS loss post-calving
• Minimize transitional problems
• Consider using buffers, extra salt, bypass fat, and ration stabilizer that prevents yeast growth and ration heating.  
• Always use forages of excellent quality

Reproduction:

• Maintain compliance with reproductive protocols
• Continue breeding cows
• Utilize TAI programs (presynch, ovsynch, resynch) to increase insemination rates
• Continue heat detection aids like Kamars, tail chalking, podometers, etc
• Breed early am
• Vaccinate and test for infectious diseases that cause infertility

Sick cow monitoring:

• Early diagnosis and treatment of disease is key
• Fresh cow diseases, mastitis, etc cases increase leading to greater days open.

Calves:

• Heat and humidity increases environmental bacterial exposure
• Colostrum management is essential
• One gallon 1st feeding followed by 2 quarts the second feeding
• An additional benefit exists to feed colostrum up to 3 days after birth
• Collect in a sterile bucket and cool rapidly if not feeding immediately 
• Provide free-choice water.
• Use 5 gallon buckets to ensure water is available 24 hours a day 
• Feed 3-4 quart milk replacer or pasteurized milk every feeding  
• Provide a clean, dry, well-ventilated environment.  Open up the hutches 

So I institute all of these changes and make the investment, what will it get me?  On average, heat abatement strategies will gain 5-7# milk/day.  A 100 cow herd gains an average of 5# over a 30-day period during the summer at $15/cwt milk, $2250 is gained.  But not only will you reap production benefits.  By increasing preg rates from 19% to 21%, some models predict a ~$70 return per cow.  KSU agricultural economist K. C. Dhuyvetter indicates that the breakeven cost for an installed heat abatement system is around 3-4% milk production loss.  A return of $2/cow/day can be acquired from heat abatement systems when heat stress related production systems exceed 20%.  And remember that for every peak pound of milk you gain 250# milk over the lactation. 

    

Work now to institute heat abatement in order to reap the rewards this summer.