The process of parturition -delivering the newborn calf- is the most stressful time in a cow's life. There is a significant decrease in immune system from two weeks before to two weeks after calving. There is an increased demand for available calcium as she comes into milk production. The ration changes in composition and energy density. Hormonal changes occur to facilitate the calf coming through the birthing canal. Pathogens have easier access to the body through the birth canal and udder.
As the cow prepares to have her calf, many hormonal changes occur. A hormone called relaxin is produced, which allows a loosening of ligaments. This allows for the stretch in the birth canal to allow the delivery of the calf. The risk factor is all tendons and ligaments in the body are affected. This is why there are more leg, joint, and tendon injuries at this time. It is important for cows during this time to be in pens on dirt or skid resistant rubber to minimize these injuries.
During the weeks prior to caffeine, the immune system is sequestering antibodies and bioactive proteins in the udder. These are components of colostrum, which serves as a primary source of immunity for the baby newborn calf. Because it occurs well in advance of calving, vaccines given to the cow, in hopes of passing production to the calf, should be done prior to dry off or in the early dry period. Because there is a large decrease in immune system at dry off, it is best not to give vaccines that dry off to two weeks after. Adequate levels of protein, vitamins and trace minerals are vital to maximizing the quality and quantity of the immune protein in the colostrum.
Demands for calcium in the body greatly increased at the time of calving. Calcium is required for proper muscle contractions. The birthing process requires strong contractions of smooth muscles in the uterus as well as other muscles of the abdomen. Cows that are low in calcium will have a difficult time dilating the cervix and quickly delivering the calf. Additionally, the inability of good muscle functions can present as "milk fever", where a cow is unable to stand. Prevention of this during the dry period is accomplished by feeding a high quality dry cow mineral and adequate levels of vitamin D. A dry cow mineral usually contains a 1:1 ratio of calcium to phosphorus. Excess calcium levels can be detrimental.
It is common to see some degree of milk fever complex at the time of calving. This involves the interplay of four primary elements: calcium (Ca), phosphorus (P), magnesium (Mg), and potassium (K). Of these, calcium is the most important. Range of symptoms of calcium shortage are dependent upon how low the blood calcium levels are. Clinically progression of symptoms would go as follow:
- Off feed or decrease appetite with low or normal temperature (101.5 degrees or less)
- Ear flicking/tail swishing while working with cow
- Slow progression with calving/poor cervix dilation
- Difficulty in passing manure or/hard manure
- Weakness or instability when standing
- Unable to get up
- Lying flat on side/rumen bloated up
- Comatose – "deep sleep"
- Death
Treatment options are based on severity. Cows that are able to stand can respond adequately to oral products, such as liquid, gel/paste, or boluses. They certainly also can be treated with IV products or by sub Q 23% calcium. Once they are unable to get up, treatment is best given by IV or sub Q 23% calcium. If they have an advanced to the stages of flat out or comatose, the only option is IV. My preference for calcium plus electrolyte boluses is Dr. Paul’s Downer Boluses.
There are some important considerations with calcium administration"
- The only calcium that should be given sub Q is 23% calcium (also called 23% calcium borogluconate). All others may cause abscesses and cellulitis.
- All oral calcium are caustic. Make sure heads are well restrained and administer gently. Irritation or tearing on back of throat (pharynx) can result in cellulitis, which is painful and fatal. Lubricate large boluses with vegetable oil before administering. Never give oil calcium to a downer that cannot swallow.
- Always warm up the IV calcium two body temperature before administering. Administer slowly while keeping a hand on the jugular vein or over the heart to monitor the pulse. It is normal for pulse to quicken but abnormal beats or rhythm would be a reason to stop the IV.
- IV calcium causes a spiking blood calcium levels over normal. Do not repeat IV calcium for at least six hours after first treatment unless a very largecow or old Jersey and no significant improvement.
- Milk fever will be most common in cows third lactation or older (second lactation or older in Jersey and Jersey cross). Nearly all fresh animals will have some drop in blood calcium levels at calving. Not all will require treatment.
Other blood electrolytes play a role in fresh cow milk fever complex
1. Phosphorus - A deficiency in this can contribute to cows being unable to stand. Often will see this demonstrated as a bright downer. The cow will be alert and difficult to halter and may move around a lot when trying to start an IV. Upon completion of treatment, they try to get up but just can’t quite do it. They may eat and pass manure, but often needs some time to rise.
Clinically, these cows are usually treated with calcium initially. Calcium products such as CMPK and Amcalcilyte also contains phosphorus. The preferred method to provide additional phosphorus is orally. The phosphorus in mineral form is not quickly absorbed and not suited for treatment purposes. A product containing mono or disodium phosphate provides quick absorption. An excellent product is Phos-Drench from Dr. Paul‘s Lab. I drench 4 to 6 hours after calcium administration with second bottle 12 to 18 hours after the first.
2. Magnesium - A deficiency in this is sometimes referred to as "grass tetany" although the term refers to the condition in cattle grazing lush pastures during cool, wet springs. In fresh cows, it exhibits as an aggressive downer. They will lunge when trying to be haltered or will charge if they are still up.
Calcium is indicated as a treatment as 50% of the cases will respond to just go calcium treatments. Again, CMPK and Calpus contain magnesium and helps improve response.
3. Potassium - In fresh cows, potassium does not present as a deficiency, but high levels in the diet can affect the other electrolytes and response to the treatment. Alfalfa grown with high amount of potash and manure will have high potassium levels and our best fit at low levels to dry cows or springing heifers.
An easy clinical sign of high potassium levels is severe udder edema that is poorly responsive to treatment. My preferred product for this edema is Dr. Paul‘s Comfort Boluses.
Caution needs to be used when administering IV products that contain potassium. Increased blood levels of potassium will cause the heart rate to increase and too high of levels with cause rhythm issues. This is another reason to space IV treatments properly, if using preparation that contains potassium.