Dairy Heifer Health, Disease Control, and Vaccinations

he future of the dairy herd is dependent on the production of superior heifers to replace culled lactating animals. Therefore, it is imperative that the health status of the replacement animal is optimized to present a healthy first calf heifer to the lactating herd. Studies have consistently demonstrated the detrimental effects of pneumonia in calves on age at first calving and on milk production once these animals enter lactation. Calves with respiratory infections were twice as likely to leave the herd and age at first calving was delayed by 6 months when compared with calves that did not experience respiratory disease or pneumonia. In another study, calves treated for scours were three times more likely to calve at 30 months of age or greater.

The areas of management of primary concern in maintaining the optimal health of the heifers include parasite control, coccidiosis, infectious diseases like IBR, BVD, PI3 and BRSV, and other problems such as pink-eye and foot rot. Mastitis control in pre-partum heifers is also included in this list.

Health

Both parasite control and the feeding of growth promotants improve feed efficiency and enhance growth. Regular deworming and treatment programs for internal and external parasites are essential to improve heifer performance. At the Virginia Tech dairy facility, we use a strategic deworming protocol. This protocol not only deworms the heifers, but decreases the parasite (worm) larva population on the pasture. Heifers are first dewormed in early May, using an Ivomectin® or Eprinomectin® product. This rids the heifers of the initial parasite burden obtained during the early warm, moist days of spring, when parasite loads are beginning to peak in cattle and on the pastures. The second deworming occurs 5 weeks later dependent on whether the product is a pour on, injectable or bolus. The reason for this second 5-week injection is two-fold. First, the ivomec has residual internal parasite killing activity for 2 weeks. Therefore, any parasites developing in the digestive tract during this time period of 2 weeks will be eliminated. After this 2-week period, many parasite larva ingested on the grass or pasture contamination will develop into adults. This development period is approximately 3 weeks (larva to adult parasite). The second injection, 5 weeks later in mid June will eliminate or kill these adults. By keeping the adult infection (which produce larva for the pasture) to a minimum within the digestive tract of the calf, we maintain minimal parasite burdens on the pasture as well. These two injections give adequate protection during the peak period of parasite contamination.

When using the Eprinomectin® pour-on product, the second deworming should be administered at 5 weeks, as well. There is some data to support a residual activity of 4 weeks with the Eprinomectrin® product; however, to date this is not supported with adequate information.

Typically by early July, pasture parasite loads will begin to decrease due to hot weather and decreased moisture. If good parasite management has been implemented, parasite burdens on the pasture will be negligible. Producers should be cautioned against introducing heifers that have not been dewormed, as they can be a source of parasite contamination for the pasture and the original dewormed heifers. A third deworming of a single dose of either product may be beneficial in late October. This would eliminate internal and external parasites (grubs and lice) obtained during the summer and decrease the parasite load prior to winter feeding. Also, if the summer season has been mild and moisture has been high, parasites will survive in higher numbers on the pasture, causing a higher heifer parasite load.

Coccidia control measures should be started in baby calves at 5 to 10 days of age and continue until 30 days prior to calving. These products are found in some milk replacers as well as a feed additive in concentrate. Medicated feeds may improve performance and can aid in the prevention of coccidiosis, when calves are fed a specific coccidiostat like Decoquinate, Rumensin®,or Bovatec®. Ionophores, such as Bovatec® or Rumensin®, are effective as an aid in reducing coccidiosis, but have the added benefit of improving feed efficiency. However, ionophores are not effective as a treatment against coccidia. If calves have been diagnosed with coccidiosis, they should be treated with Corid® (amprolium,) or sulfonamides (sulfa) and then fed one of the ionophores for prevention. Supplementation costs pennies per heifer per day, which is more than offset by decreasing the amount of grain required per pound of gain or supporting adequate growth with lower quality forage for older heifers. The use of ionophores in confinement-reared heifers or those fed excessive energy rations may lead to over-conditioning. This is especially important during the time calves are 3 to 9 months old or the pre-pubertal phase of rapid mammary gland development. Excess feeding during this period can lead to a decrease in milk secretory tissue.

Crpytosporidiosis is perhaps one of the larger problems we face in nursing replacements. It has been diagnosed on essentially every dairy farm in the United States. In our experience, it strikes calves at approximately 8 to 14 days of age, causing a profuse diarrhea with subsequent dehydration. Morbidity (number of calves with the disease) is high, however mortality is low with the proper administration of fluids and supportive therapy. Therapy and vaccinations are now being tested to eliminate this problem, but at this time products have not been adequately tested to advocate their use. Adequate intake of quality colostrum and keeping calves clean, dry and comfortable, thereby reducing stress, are the essential components to combat cryptosporidiosis.

Vaccination Protocols

Vaccination programs in the heifer herd are tailored to protect against the diseases prevalent in the area and specific diseases on individual farms. Herd owners should consult their herd veterinarians for specific vaccination protocols for your area. Most vaccinations are initiated between 4 and 5 months of age, when maternal protection gained from colostrum has subsided. These vaccinations may need to be repeated 3 weeks later, following label directions to insure peak immunity or protection. Follow all label directions, as some vaccinations must be repeated, while others are single injections. Vaccinations should be repeated 45 days prior to breeding or at approximately 12 to 13 months of age. Injections are then repeated at 18 months of age and 45 to 60 days prior to calving for sufficient levels of immunoglobulins (antibodies) in the colostrum for the calf. Many of the diseases that cause infertility and early embryonic death or abortion can be prevented with proper vaccination procedures. Again, the type of vaccination will depend on the diseases that have been isolated on a specific farm or are found in your specific region.

Following is a list of typical management procedures and vaccination protocols. These can vary depending on the area of your farm location or specific diseases that have been isolated on your farm. This protocol should only serve as a guide, as specific vaccination questions should be directed to your veterinarian.

Follow label directions on all vaccines. Some vaccines require boosters at specific time intervals following the initial vaccination. Consult your veterinarian for specific directions and vaccination protocols. We do recommend modified live vaccines; however, directions must be adhered to for safe use of the product. Remember, the heifer vaccination program is the foundation of disease control in the lactating cow herd.

The Newborn (1 to 10 days of age):