- Heifers are more susceptible to mastitis than are cows
- Heifers that are infected at calving produce less milk during their first lactation compared with uninfected heifers
- Internal teat sealants, administered 4-6 weeks pre calving by trained personnel, have proven the most effective protection
- Regular teat spraying and/or milking within the first 12 hours after calving are low cost approaches that can also reduce the risk of clinical mastitis
- Herds that have more than 15 cases of clinical mastitis within 2 weeks of calving per 100 heifer calvings require proactive management to reduce heifer mastitis.
Heifers are most at risk of mastitis prior to calving. As the udder develops in size, milk often leaks from open teat canals allowing in bacteria, such as Streptococcus uberis or coagulase negative staphylococci (CNS), resulting in infection before calving.
A study using the DairyNZ identical twin herd1 identified that heifers which calved down with a subclinical Strep. uberis infection produced 7% less milk than their uninfected twin mates throughout their first lactation. Twins which were detected and treated for clinical mastitis due to Strep. uberis had similar losses (Figure 1).
This degree of loss has not previously been reported because subclinical cases, which don’t create visible changes in milk or the udder, are usually not detected. It is possible that damage to the milk producing tissues had occurred, prior to calving.
This research indicates that prevention of all Strep. uberis infections is important, not just the clinical cases. A number of approaches have been tested under research and field conditions.
They focus on four control points:
- reducing the risk of udder oedema and milk leakage;
- reducing bacteria at the teat end before calving;
- placing a barrier at the teat canal to block entry of bacteria; or
- supporting the animal to deal quickly with new infections.
1. Reducing udder oedema and milk leakage
Oedema is the swelling that occurs under the skin of the udder and sometimes along the belly in a heifer prior to calving. It is a significant risk factor2 for heifer mastitis, but what causes it is poorly understood. Contributing factors appear to include:
- excessive feeding immediately prior to calving
- excessive dietary sodium or potassium levels
- over-fat heifers, and
- hereditary predisposition.
Extra hay or silage in the diet pre-calving has been reported to have no impact to aid oedema or reduce milk leakage3.
Twice daily calf pick up
Milking heifers within the first 12 hours after calving is another way that may reduce udder oedema and milk leakage. It may also reduce the chance of bacteria getting into the teat canal and causing infection.
In practice, this involves twice-daily pick up of new calves, and bringing freshly calved heifers in for milking at both the morning and afternoon milkings.
A NZ study4 identified that halving the interval between calving and first milking, from 20 hours to below 10 hours, led to a 45% reduction in clinical mastitis, less subclinical mastitis and less udder oedema.
2. Reducing bacteria at the teat end
Teat spraying before calving
Using normal disinfectant teat spray at regular intervals before calving is a relatively low-cost approach for reducing the number of bacteria on heifer’s teats. A NZ study5 identified that applying an iodine-based teat spray three-times weekly for the last 3 weeks before calving led to reductions in the number of Strep. uberis on the teat-ends at 24-48 hours before calving. Although there were fewer Strep. uberis infections at calving and 50% fewer Strep. uberis clinical cases, the incidence of clinical mastitis caused by all pathogens was not significantly reduced.
3. Placing a barrier at the teat canal
Treatment with an internal teat sealant pre-calving
Using an internal teat sealant has proved to be the most effective strategy for reducing environmental mastitis in heifers. It involves introducing a non-antibiotic material into the udder about 4-6 weeks before calving to provide a physical barrier to the entry of bacteria (figure 2).
Following calving, the calf strips out some of the teat sealant when suckling, and the rest is removed by manual stripping, before attaching the teat cups. However, milking staff need to be aware that flecks of teat sealant may persist in milk for some weeks after calving and may be incorrectly diagnosed as cases of clinical mastitis.
Two NZ herd studies6,7 have proven the effectiveness of internal teat sealants.
Good hygiene at application is imperative and some vets provide technicians to perform the task. For herds with an above average rate of heifer mastitis (15% or more heifers clinical in the first two weeks after calving), this approach becomes cost effective.
External teat sealant ineffective
By contrast, application of an external teat sealant pre-calving has proved ineffective and cumbersome. The non-irritant latex, acrylic or polymer-based film which produced a thin layer over the teat had to be re-applied weekly and a New Zealand study showed that it didn’t significantly reduce cases of clinical mastitis8.
4. Supporting the animal to deal quickly with new infections
Studies identified that treatment with long-acting antibiotics before calving showed no benefits. Treating with short-acting antibiotics just prior to calving or on the day itself were effective in reducing clinical mastitis, but it is an expensive option, and not recommended because of the risk of inhibitory substances contaminating milk.
Other helpful9 strategies are based on common-sense. They include: keeping udders clean by managing pasture allocation following rain, reducing the risk of dystocia or retained foetal membranes, running separate heifer and cow mobs pre and post-calving to reduce bullying and pre-calving milking as a last resort for heifers with very tight udders. However the latter should be used with caution as it may increase the risk of a negative-energy balance in the pre-partum period.
Which approach is best for your system?
The best approach for your herd will depend on a number of factors, which include:
- Gap in performance between current levels of clinical mastitis among first-calving heifers and industry targets
- Farm-specifics costs, management risk and likely benefits of each approach
- Availability of infrastructure for safe administration of internal teat sealants to heifers, four weeks before calving
- Availability of labour to pick up new-born calves twice per day and bring heifers in to be milked
- Practicality of teat spraying heifers’ teats 2-3 times per week, for the last three weeks before they calve.
For herds with more than 15 cases of clinical mastitis within two weeks of calving, per 100 heifer calvings, SmartSAMM recommends steps are taken to more proactively reduce heifer mastitis.
This article was originally published in Technical Series June 2015.