Herd Expansions Don't Need to Expand Health Problems

Herd expansions don’t need
to expand health problems

By following six basic biosecurity practices, you can avoid losses and costs when you add animals to your herd

By Bill Stone

Few dairy producers add a line to their financial statement for additional treatment costs or deaths due to a disease outbreak during an expansion. But for many dairies, a severe disease outbreak almost sunk expansions and, in some cases, the business.
    By looking at approaches some dairies took during expansion, and the problems that resulted, hopefully you can prevent risks.

Herd A
    History: Expanded from 350 to 600 cows.
    Purchased: Bought primarily springing heifers that were due or would calf in about four weeks from two cattle dealers. Bought some cows from herd dispersals.
    Biosecurity: All animals were supposedly vaccinated prior to purchase and upon arrival at the dairy. Purchased animals moved directly into the pre-fresh group.
    Results: Severe respiratory outbreak in animals around freshening for a six-week period. About 25 head died soon after freshening; production was impaired in at least 50 head.
    Over the next few months, bulk tank somatic cell counts (SCC) rose from 200,000 to 600,000. Bulk tank cultures showed that Streptococcus agalactia, a form of contagious mastitis, was present. The entire herd was cultured seven times over the next several months to eliminate the infection.

Estimated costs related to disease

	Deaths	$30,000
	Mastitis cultures	$38,000
	Dumped milk, drugs, etc.	Variable
	Additional labor	Variable
	Lost milk due to impaired health	Variable
	Total	$70,000

Herd B
    History: Expanded from 600 to 1,000 cows.
    Purchased: Late-bred heifers, 6 weeks to 3 months from freshening, from several heifer growers.
    Biosecurity: All animals were supposedly vaccinated prior to purchase and seven to 14 days after arrival. Purchased animals were housed in a separate pen until three to four weeks prior to freshening.
    Results: Animals freshened with normal levels of health disorders. Bulk tank SCC increased from 240,000 to 500,000 over the next few months. Bulk tank cultures indicated that Mycoplasma, a form of contagious, non-treatable mastitis, was present. Two whole-herd cultures were needed to find and cull the 35 animals that had become infected.

Estimated costs related to disease

	Culling of replacement animals	$28,000
	Mastitis cultures	$20,000
	Total	$48,000

Herd C
    History: Added 70 lactating cows.
    Purchased: Herd was bought in Canada.
    Biosecurity: Herd supposedly vaccinated two weeks before and upon loading to be trucked for 20 hours. No feed or water was available during trucking. Animals were isolated in an old barn.
    Results: Cows developed severe respiratory infections within one week and 28 died.

Estimated costs related to disease

	Deaths	$36,000
	Dumped milk, drugs, etc.	Variable
	Additional labor	Variable
	Lost milk due to impaired health	Variable
	Total	$36,000

Herds D and E
History: Each had relatively small expansions many years ago. A couple of years later, some of the purchased animals had clinical Johne’s disease. Both herds now have a significant Johne’s disease problem where they had none prior to expansion.

Estimated cost.............Many thousands of dollars

Herd F
    History: Purchased 200 short-bred heifers from local growers.
    Biosecurity: All heifers had been properly vaccinated with known vaccines prior to purchase. Purchased heifers were isolated either on pasture or in a renovated old barn.
    All heifers had milk samples cultured at freshening.
    Results: Dairy lost one heifer due to calving complications out of 200 purchased.

Estimated costs related to purchase
Mastitis cultures............... $2,000

Cut Your Risks
    Many times you can break the “rules” when bringing new animals onto your dairy without any consequences. But it can take only one “consequence” to put your dairy under financial stress.
    The table shows factors that influence the short- and long-term health status of your herd following an expansion.

Practices Protect Animals
    The occurrence of disease depends on the interaction of the animal, the environment its in and the pathogen. For example, animals that are poorly vaccinated may not have any respiratory problems if stress is minimal because of a short truck ride, being housed in familiar stalls in well-ventilated facilities and being fed in a familiar system.
    On the flip side, well-vaccinated animals may get severe respiratory infection if they’re highly stressed from a long truck ride, a poor housing environment or co-mingling with existing livestock.
    The following six practices can protect animals you add to your herd:
    1. Buy heifers a few months from freshening to give them time to adjust to feeds, new environment and other animals before facing the added stresses of calving.
    2. Ensure – and verify – that animals are appropriately vaccinated against major respiratory diseases – IBR, BVD-PI 3, BRSV – prior to moving to your dairy. Some veterinarians also recommend vaccinating against pasteurella. Because an animal is vaccinated, it doesn’t necessarily mean the appropriate vaccine was administered or that it will protect against pathogens most likely to cause problems during expansion. Verify vaccinations by questioning sellers.
    3. Isolate newly purchased animals for about three weeks post-arrival to give them time to adapt to a new environment before socializing with the resident herd. If new animals are going to get respiratory diseases, it usually happens within this period.
    Other infectious problems such as contagious mastitis or Johne’s disease won’t be apparent for some time.
    Ideally, isolation facilities should be separate from facilities housing resident animals. They should be comfortable and well ventilated. If the “old barn” is being used, bed the stalls well and size stall loops appropriately. Provide adequate feed and water space.
    If purchased animals must be housed with resident animals, provide excellent ventilation. Prevent contact with the resident animals.
    4. Culture milk of all purchased cows upon arrival and that of all heifers upon freshening. If you buy cows, culture the bulk tank of the herd of origin at least once. All milk samples should be evaluated with the standard aerobic culture and with the additional Mycoplasma culture.
    5. Collect blood samples before transport or soon after animals’ arrival on your dairy. Test samples for Bovine Viral Diarrhea Virus-Persistently Infected (BVDV-PI) and Johne’s disease. The BVDV-PI test provides a reliable yes/no answer. Cull all positive animals immediately.
    The Johne’s ELISA test is only a screening tool. Higher readings indicate an increased probability of infection. Many dairies will reject heifers with Johne’s ELISA values greater than 40, although the cut-off point can vary with your herd’s Johne’s goals.
    Registered herds may want to test for Bovine Leukosis Virus (BLV).
    6. Review your expansion plan and biosecurity protocols with your veterinarian.

Factors affecting cattle health during an expansion
Risky			Conservative
	Replacement source
Auction barn	Cattle dealer	Local grower	Your own
	Purchasing
Lactating cows	Fresh or nearly fresh heifers		Heifers 4 to 5 months pregnant
	Vaccinations
None to one at moving		appropriate vaccine given 4 to 5 wks. and 2 to 3 wks. before moving
	Truck ride
Long distance			Local grower
	Testing
None		Mastitis – bulk tank and individual BVD – blood test for PI status Johne’s – blood ELISA
	Farm arrival
Mixed with the home herd			Isolated