The transition period is commonly thought of as three weeks before to three weeks after calving. Many of the diseases that occur in the post-calving period can be related back to problems and mismanagement in the dry period.
Some of the diseases that occur during the transition period are discussed, along with management practices to control them.
The cow’s immune system function declines around calving, which makes her more vulnerable to all infectious diseases. To minimize the impact, it is important that stress is minimized and that the nutritional needs of the cow are satisfied throughout the dry period with special attention to protein, energy, vitamins and minerals.
The effects of any stress are amplified in the transition period and attention should be paid to cow comfort, stocking rates and cooling in hot climates.
Vaccines given in the dry period serve to boost the cow’s own immunity against infectious diseases during the transition period. Vaccines also boost the antibody levels in colostrum, critical to calf health.
Most of the new intramammary infections in modern dairy operations occur during the dry period. New infections can occur immediately after dry-off and the period right around calving. These subclinical infections have a negative economic effect because they lower milk production, and the increased somatic cell count (SCC) can lead to lost milk income from failure to earn premiums.
A time-proven management practice to control mastitis has been dry-cow therapy. Dry cow tubes have a dual role – to treat and cure persistent subclinical infections acquired during the previous lactation and to prevent new infections.
The ideal dry cow tube would prevent those infections occurring around calving, which may mean some milk withhold. Other management practices that reduce new intramammary infections include hygienic and comfortable housing, proper stocking levels and good nutritional programs.
The success of a dry cow mastitis program can be monitored by comparing SCC prior to dry-off to early-lactation SCC. Ideally, early-lactation SCC should be below 200,000, which would indicate that any previous infections had been treated and/or no new infections had been acquired.
Monitoring the number of clinical mastitis cases occurring in the first few weeks of the lactation can also be an indication of the success of the dry cow mastitis program.
Most of the new infections acquired during the dry period are environmental gram-positive infections. Culturing fresh cows can detect these subclinical infections and enable them to be treated before they have had a deleterious effect on the lactation and also serve to find those chronic contagious organisms that are difficult to treat, such as Staph aureus and Mycoplasma spp.
Vaccines may also be given to dry cows to help prevent the severity of gram-negative clinical mastitis.
When a cow loses weight, her body fat is mobilized, which can result in a buildup of ketone bodies in her blood. Subclinical ketosis can be diagnosed with blood and milk tests and has been associated with lowered immunity and many of the diseases occurring after calving, such as mastitis, metritis and LDAs (left displaced abomasum).
It is critical that dry cows do not lose weight during the dry period. It is normal for cows to decrease dry matter intake (DMI) as they approach calving, but if this is excessive, or if the ration is not formulated properly, problems can occur.
Any management practice that could lower DMI should be avoided; this includes overstocking, heat stress, unpalatable or mycotoxin-containing feeds and excessive pen moves.
Calcium is involved in many of the body processes, including the immune system and muscle function. If the enzyme systems that extract calcium from the skeleton of the cow are not functioning properly around calving and if the blood calcium level falls too low, then the cow gets milk fever.
Far more common, though, is subclinical hypocalcemia, where the cow appears normal. However, subclinical hypocalcemia has been associated with many of the problems occurring after calving, including mastitis, metritis, LDA, lower conception rates and lowered immune function.
Methods to prevent the problems of subclinical hypocalcemia include ration manipulation (either very low or very high calcium levels), feeding anionic salts and supplementing cows around freshening with calcium supplements.
Infections occurring in the reproductive tract can be common after calving and can range from mild subclinical infections to severe metritis.
To avoid uterine infections that can result in everything from poor conception and delayed breeding to death, producers need to have proper dry cow and transitional cow management. Management includes providing a clean, hygienic, comfortable calving area and the assistance of experienced personnel who understand the importance of sanitary methods, if needed.
As previously mentioned, subclinical ketosis and subclinical hypocalcemia can both predispose to metritis.
Proper hoof trimming during the dry period can help prepare a cow’s feet for the subsequent lactation and prevent lameness. Improper preparation of the rumen during the transition phase of the dry period for the higher-energy diets of lactation may result in acidosis, which can lead ultimately to sole ulcers and lameness. Heat stress during the transition period can also exacerbate acidosis problems and therefore laminitis.
The dry period is the foundation on which the subsequent lactation is based. Proper management of the cow during this period helps maximize the cow’s welfare, production capabilities and economic return. PD
Mark van der List, BVSc, MPVM, is a professional services veterinarian with Boehringer Ingelheim Vetmedica Inc., and is based in Davis, California.