The transition period that begins two weeks before calving (parturition) until 60 days after calving is a critical time for a cow’s health, her milk production and the overall success of a dairy operation.

The long list of things that can go wrong during transition can be distilled down to a short list of inherent perils or factors that can make an adverse impact on milk production throughout lactation: inadequate dry matter intake, milk fever/hypocalcemia, retained placentas and mastitis, ketosis and displaced abomasums.

Most cows reach their peak milk production 45 to 65 days after calving. Their milk production then decreases by 5 to 10 percent each month through the remainder of lactation. Dairy scientists estimate that, at the peak of lactation, any peril that decreases milk production by 1 pound will decrease milk production throughout lactation by a total 500 to 1,000 pounds. Cows that decrease peak milk production by 2 to 5 pounds will have proportional decreases in production over the entire period. The following descriptions illustrate why these perils make such a dramatic effect on milk production.

Inadequate dry matter intake
Inadequate dry matter or feed intake has a major impact on milk production during the transition period. Most cows drop their feed intake by 10 to 30 percent starting about two weeks prior to calving, and won’t reach an optimum level of feed intake until two to three weeks after calving.

During this period, the rumen environment converts fermentation and digestion from the higher roughage of dry cow rations to the higher-energy rations routinely fed after calving. The rumen papillae elongate during this change to better utilize the higher-energy ration. Rumen pH levels also tend to drop and the cow becomes susceptive to digestive upset and rumen acidosis. Proper management and monitoring will enable these digestive changes to occur while minimizing the problems of cows going off feed.

Milk fever/hypocalcemia
Within the first 24 to 48 hours after calving, milk fever can present a problem as the cow requires a major supply of calcium from its blood supply for milk production. When the blood calcium drops too quickly and too low, the cow develops classical milk fever. Most dairy personnel recognize milk fever as the cow develops incoordination and becomes comatose. Caretakers usually proceed with the appropriate intravenous administration of calcium and other complementary electrolytes.

The incidence of milk fever in high-producing cows is estimated to occur in 4 to 10 percent of the cows beyond their second lactation. The classical milk fever incidence is relatively low compared to the number of cows that develop lower-than-normal levels of blood calcium and retain persistent levels of low blood calcium – but do not develop classical milk fever. These cows are classified as hypocalcemic and can present a persistent problem for several weeks after calving.

Some dairy scientists think that the incidence of hypocalcemia after calving can range from 10 to 30 times greater than classical milk fevers. Hypocalcemic cows have a higher incidence of retained placentas, abomasol displacements and impaired rumen motility. The lower-than-normal blood calcium reduces smooth muscle tone and thereby reduces the intensity of uterine, rumen and intestinal contractions. Most hypocalcemic cows will respond to oral calcium and electrolyte supplementation, which minimize the problems of hypocalcemia. Oral calcium supplements are somewhat limited in their efficacy to treat cows already recumbent or semi-comatose with milk fever. But they are an effective aid in reducing persistent hypocalcemic cows after calving.

Retained placenta/mastitis
The problems of retained placentas and mastitis the first few days after calving are not generally a result of a single cause or factor. Both retained placentas and mastitis seen shortly after calving are associated with some incompetence of the immune system, hormone changes at calving (such as higher levels of blood cortisols) and the increase of estrogen hormones that stimulate parturition or calving.

Cows with high blood levels of cortisols and hypocalcemia have a much higher incidence of post-calving problems such as retained placentas and ketosis. They may also be predisposed to displaced abomasums. Dairy producers should work with their veterinarians to develop a treatment protocol that’s for retained placentas and mastitis the first few days after calving. If not treated properly, severe post-calving mastitis and metritis (uterine infections) not only decrease milk production but can also lead to permanent infections, which can result in reproductive failures. Cows with severe mastitis the first seven to 10 days after calving often develop permanent mammary gland scar tissue, which, if toxic in nature, can be life-threatening.

Ketosis
Ketosis is a potential problem in high-producing cows: They can’t maintain enough blood sugar or glucose to meet the energy demands of producing large volumes of milk during the first 60 to 70 days after calving. To meet the energy/glucose demand for milk production, a cow must call on body reserves of energy and the primary continuous supply of blood glucose is from body fat.

When converting body fat to blood glucose, the intermediate form of energy from the fat prior to changing to blood glucose are non-esterified fatty acids (NEFAs) and ketones. When body NEFA levels and blood ketones rise above normal levels, they tend to act like toxins and cause the cow to go off feed. Most cows suffering from ketosis the first few days after calving are often associated with over-conditioned cows or carrying excessive fat with body scores of 4 or 5. The fat converted in these over-conditioned cows changes to NEFAs and the energy, as such, is not available for milk production.

Cows that develop ketosis 10 to 40 days after calving often have higher blood levels of ketone bodies then NEFAs. These high levels of ketones may present an odor in the cow’s breath and some body excretions. When ketones are not converted to blood glucose (as required for milk production) they, again, tend to act like toxins and make cows go listless and off feed. In rare cases, these ketones can cause central nervous disorders which will be manifested by the cow excessively salivating, chewing on pipes or leaning on bunks or pen structures. When not recognized and treated quickly, ketosis can cause a severe loss of milk production throughout lactation, infertility and culling from the herd. Most cows respond to appropriate therapy after ketosis recognition and have minimal long-term losses of milk production.

Displaced abomasums
The abomasum is a partially free-floating, flexible, tubular extension that connects the cow’s stomach to the small intestine. The rumen part of the stomach is relatively immovable with the exception of normal rumen wave-like contractions which help mix rumen engesta for optimum fermentation and digestion. The primary engesta flowing from the rumen to the abomasums is liquid and gaseous in nature.

Records indicate that 80 to 90 percent of the displaced abomasums occur on the left side within 30 to 40 days after calving. Some researchers report that when the uterus involutes after calving and returns to the pelvic area, the space held by the uterus near the rumen is often filled by the floating and moving abomasum. When the abomasum migrates to this lower abdominal space, it may become entrapped and remain displaced.

Many clinicians believe the abomasums become entrapped and displaced primarily because of the lack of smooth muscle tone and weak contractions to facilitate movement of the engesta. Regardless of the cause, displaced abomasums block the flow of engesta, inhibit digestion and cause the cow to go off feed. Electrolytes such as calcium, potassium and a constant supply of energy and protein will help maintain smooth muscle tone and strength. Most cows consume more potassium prior to calving than they require. However, once the cow calves, potassium reserves are marginal and supplementation with calcium, potassium and magnesium will help maintain smooth muscle tone essential for rumen contraction, as well as abomasol and intestinal normal function.

Minimizing the dangers
The above perils are a greater challenge to today’s dairy operations than they were 20 to 30 years ago. Increased milk production by individual cows, and the greater challenge of recognizing cows with stress conditions during the transition period, have led to potentially greater impact on milk production throughout lactation.

Today’s cows have an increased milk production by 20 to 50 percent over the past three decades. Conditions or perils such as hypocalcemia, ketosis and displaced abomasums are thought to be an increasing problem in cows with greater milk production. Group housing, as opposed to individual stanchions and tiestalls, have made it more difficult to recognize cows with problems during the transition period. Dairy producers should work with their nutritionist to develop programs that will maximize dry matter intake during the transition period. Veterinarians, through their regular farm visits, can develop treatment protocols that will minimize the threatening perils as soon as they’re recognized during the transition period. Equipment suppliers and facility designers should be consulted so individual cows can be easily observed and handled without excessive work and interference to daily responsibilities.

All cows have inherent predisposition to perils that impair milk production during times of transition. With appropriate treatment and action, long-term losses of milk production can be minimized. PD

Dr. Peter Franz is a DVM on staff at the Form-A-Feed and TechMix companies, headquartered in Stewart, Minnesota.

Peter H. Franz
Veterinarian Form-A-Feed
(800) 422-3649