DRY YOUR BEST. The incidence and importance of milk leakage in the dry cow. Ana I. de Prado Corporate Technical Manager Ceva Santé Animale (France)

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1 DRY YOUR BEST The incidence and importance of milk leakage in the dry cow Ana I. de Prado Corporate Technical Manager Ceva Santé Animale (France)

2 The incidence of milk leakage is an indirect indicator of the three axes at dry-off: management, udder health and welfare. Key messages: Milk leakage is related to the milk production at the moment of dry-off. The genetic potential for milk production has increased during the last decades and stopping milk production in high yielding cows at the moment of dry-off is now the key management challenge. Udder engorgement occurs due to large amounts of milk accumulating leading to high pressure which causes pain and discomfort. Both the milk production and the incidence of milk at dry off leakage have been associated with new intramammary infections (IMIs). The incidence of milk leakage in farms is underestimated and the awareness of this issue among veterinarians and farmers is very low. A simpler method is needed to reduce milk production and milk leakage, one that does not require either feed restrictions or a reduction in milking frequency.this would facilitate the dry-off.

3 Dry Your Best Technical Publications 3 The three axes at dry-off: Management, Udder Health and Welfare One important objective of the dry-off is to minimise the risk of intramammary infections (IMI). However there are two other aspects equally important and very much related to udder health management and welfare. The genetic potential for milk production has increased during recent decades and, as a result, it has become a management challenge to stop milk production in high yielding cows at the moment of dry-off. Large amounts of milk in the udder leads to udder engorgement. Udder engorgement causes pain and discomfort and there is a reduction in total lying time and the average duration of lying bouts 8, 10. Dry-off can be done in an abrupt or gradual way. The type of management has consequences on the udder health, welfare and productivity of the cow The mammary gland needs to regenerate so it is prepared for the next lactation. Curing existing infections and preventing new ones ensures a healthy subsequent lactation. Management Milk leakage Udder pain Udder Health Intramammary infections Welfare The excessive udder engorgement and the increase in udder pressure just after dry-off induces udder pain and discomfort in dairy cows. A good way to evaluate the relationship between the three axes is through these key dry-off indicators: the incidence of milk leakage, the incidence of new intramammary infections and udder pain.

4 Dry Your Best Technical Publications 4 Risks of new IMI at dry-off The cessation of milking at drying-off results in dramatic changes in the composition of the mammary gland secretion which could pose a risk of new IMI. In addition, the flushing of bacteria from the streak canal ceases and teat dipping stops. The slow transition to the involuted state delays the protective effects of lactoferrin and immunoglobulins, whilst fat and casein levels remain high inhibiting leukocyte function 17. The keratin plug formation, an important defence against IMI, may vary between cows and it has been reported that 50% of the teat canal still remained open 10 days after drying off 19. Milk is no longer being removed from the gland but cows continue to produce milk for some days. As a result, there is marked engorgement of the cisternal spaces, ducts and alveoli of the gland. The udder volume and pressure are increased due to milk accumulation. Cows may suffer pain and milk leakage (ML) can occur. This facilitates bacterial penetration of the streak canal during the first few days until involution is complete 17. Each of the biochemical changes, the increased intramammary pressure (IMP) related to the level of milk production at the moment of dry-off and the subsequent leaking of milk are believed to contribute to susceptibility to new IMI in the early dry period 9, 17.

5 Dry Your Best Technical Publications 5 Level of milk production at dry-off The National Mastitis Council recommends abrupt cessation of milking when the target of 15 litres per day has been achieved. The reason why it is recommended to reduce the milk production to that level at dry-off is due to the fact that the higher the milk production at the moment of dry-off, the higher the risk of new IMI. A study was conducted in Ontario (Canada) to evaluate the association between milk production at dry-off and IMI. Dairy Herd Improvement (DHI) records were examined during 1998 and A new IMI was defined as a change in linear score from less than 4.0 at the last test prior to drying off to linear score greater than 4.0 at the first test in the next lactation. Only 16% of cows producing less than 13kg of milk at dry-off developed new IMI compared to 26% of cows producing greater than 21kg 4. Change to linear score >4 (%) P<0,05 < >21 Milk production at dry off (kg) Percentage of cows with changes in linear score by milk production at dry-off. Another study concluded that for every 5kg increase in milk production at dry-off above 12.5kg, the odds of a cow having an IMI at calving increases by 77% 12. Other data showed that for each litre increase in yield at drying off, the odds of a quarter being infected with an Enterobacterial organism post calving increased by This equates to doubling the risk of new IMI in the dry period for every 12 litre increase in yield at drying off. It has been hypothesised that there is also an association of milk production and teat-canal closure. The keratin plug is the udder s natural defence mechanism as it prevents bacteria from entering the teat canal during the dry period. In a study conducted in North America the authors found an association between milk production and closure of the teat canal. At the end of the first six weeks

6 Dry Your Best Technical Publications 6 of the dry period, 47% of quarters from cows producing 21kg or more were still classified as open compared with only 19% of quarters from cows producing less than 21kg 4. Observations of the dynamics of the teat canal closure for a group of 756 dairy cows after dry-off were also reported in a New Zealand study 19. The investigators demonstrated that 50% of teats were still open at day seven after drying off. New Zealand Cows US Cows (Yield<21 kg) US Cows (Yield>21 kg) Days after drying off Proportion of open teats observed during the dry period under natural field conditions in studies conducted in New Zealand and North America 1. It appears that the decline in milk production has a positive effect on decreasing the rate of new IMI during the dry period. It could ameliorate new IMI incidence not only by the increased risk of mastitis associated with milk leaking from quarters but also by the association of production and teat-canal closure 4.

7 Dry Your Best Technical Publications 7 Causes and importance of milk leakage Milk leakage is defined as milk flowing from one or more teats in the absence of milking. ML is considered to be present if we observe streams of milk coming from one or more teats, a drop of milk on the teat end or indirectly if we see milk on the ground under the udders. Following the data from some publications, ML can occur if the closing mechanism of the teat canal is compromised, for instance if the teat end is damaged 6. It has also been observed that milk flow rates were higher in quarters leaking milk than in other quarters 11, 13. This is not exclusively a characteristic of high-producing cows 7. In a study carried out on 15 commercial farms in Germany, even lower yielding primiparous cows with greater peak milk flow rates were at risk of leakage. In addition, short teats, inverted teat ends and cows with teat canal protrusions, that may have less sphincter muscle tone, increased the risk of milk leakage in multiparous cows 7. When a huge amount of cisternal milk yield accumulates in the udder, the IMP increases and may cause ML from the shorter canals 13. The relevance of ML was demonstrated when it was observed that cows leaking milk after dry-off were four times more likely to develop clinical mastitis and had 6.1 times more risk of developing an IMI with a major pathogen during the dry period than cows that did not leak 16. The results of this trial reaffirmed the high susceptibility of cows in the early dry period even when the prevalence of IMI with major pathogens at dry-off was low.

8 Dry Your Best Technical Publications 8 The authors concluded that ML was strongly associated with clinical mastitis and IMI with major pathogens in the dry period. ML allows bacteria to penetrate the teat canal and colonise the mammary gland 2. The percentage of cows leaking milk was associated with an increased incidence rate of E. coli and S. aureus clinical mastitis in herds with low somatic cell counts (SCC). Leaking milk may also enhance the nutrient environment for micro-organism in the bedding, thereby increasing the environmental exposure. The risk of udder infections in association with ML increases when the hygiene in the cows environment, especially in the bedding, is poor. Strategies to reduce the quantity of milk and ML at dry-off may be important to minimise the risk for new IMI 14, 15. Pathways of new IMI Drying off (Cessation of milk) Intramammary pressure Milk leakage Streak canal compromised Increased pressure results in shortening and widening of the streak canal Increased risk of ingress of pathogens Delayed keratin plug formation A flow diagram showing the pathways of new intramammary infections (A. Bradley).

9 Dry Your Best Technical Publications 9 Incidence of milk leakage There are very few publications where we can find data about the real incidence of ML in dry cows. One of the first studies was carried out in Netherlands in The authors concluded that milk leaking was frequent during the dry-off period. Cows were dried off with less than 5kg per day of milk production. 30% of cows leaked milk during the week after dry-off 16. In other studies, the effects of reducing milk yield by feed restriction before the dry-off resulted in less percentage of cows leaking milk 18. Two days after dry-off 14% of cows with lower production leaked milk compared with 42% of cows with higher production. In a recent study carried out in Canada 20, the effect of milk production at the moment of dry-off on ML was evaluated. All cows were treated with antibiotic, internal and external teat seal. Frequency of ML was greater in cows producing an average of 14.1kg compared with those producing 10.9kg before dry-off (75 vs 27%). This suggests that the reduction of milk production reduces the percentage of cows with milk leakage. Dairy cow showing milk leakage (milk at the end of the teat and on the floor).

10 Dry Your Best Technical Publications 10 Recent milk leakage data In order to get information about the current incidence of ML in commercial dairy farms, Ceva Sante Animale has carried out studies in Europe, USA, Brazil (unpublished data) and Mexico 3. All cows were carefully observed for ML detection after dry-off (DO) during three consecutive days. In Europe, a total of 1,142 cows from 41 different farms from eight countries were investigated. The incidence of ML was on average 24.4% at cow level with the difference between farms depending on the level of the yield 24 hours before the dry-off. The highest incidence of ML was found at visit two, between hours after DO. In the USA, 312 animals from three farms were involved in the study. The average percentage of cows leaking milk during any of the observations was 32% and the range among farms was from 21-45%. The highest ML was observed 36 hours after dry-off. In Brazil, 187 cows from three sites were involved in a study. 31% of cows leaked milk at any observation with a range from 26-44% among farms. In Mexico 1,611 cows belonging to nine farms located in two regions of Mexico were dried off by the abrupt cessation of milking. It was found that 24% of all cows studied showed milk leaking in at least one of the observation periods. The lowest and highest limits of the range among farms were 17% and 47%, respectively. The highest ML observation was detected during the second visit. The summary of these results is shown in the following graph % 31% Cows leaking milk (%) % 24% 0 Europe US Mexico Brazil Percentage of cows leaking milk at dry-off The ML incidence after having checked 3,065 animals around Europe and America is higher than expected. However, awareness of this issue between veterinarians and farmers is very low. ML is a valid indirect measure of the intramammary pressure which is related to welfare and udder health.

11 Dry Your Best Technical Publications 11 Conclusion Although one important objective of the dry-off is to minimise the risk of IMI, management and welfare aspects of the cow also have to be considered. Milk production and ML are related with new IMI. Recent studies have shown that the incidence of ML in farms is underestimated. More attention during the first days after dry-off is needed to detect cows leaking milk that may be at risk of new IMI. A simpler method of abruptly reducing milk production that does not require either feed restrictions or reduction in milking frequency is needed. This is essential to improve management, udder health and welfare at dry-off and therefore have a positive impact on the profitability of the farm. References 1. Bradley, A.J. and Green, M.J The importance of the non-lactating period in the epidemiology of intramammary infection and strategies for prevention. Vet. Clin. North Am. Food Anim. Pract. 20: Cousins, C.L., Higgs, T.M., Jackson, E.R Susceptibility of the bovine udder to bacterial infection in the dry period. J. Dairy Res. 47: De-Prado, A.I., Alamilla, M.C., Vazques, C., Mapes, G., Villa-Godoy A Importancia de los goteos de leche después del secado. Hoard s Dairyman magazine en español. Sep. 4. Dingwell, R.T., Kelton D.F., Leslie K.E., Edge V.L Deciding to dry-off: does level of production matter?. National Mastitis Council Annual Meeting Proceedings. 5. Huxley, J. N., Green, M. J., Green, L. E. and Bradley, A. J. Evaluation of the efficacy of an internal teat sealer during the dry period. J. Dairy Sci. 2002; 85(3): Ørstand, A., Farver, B.T., Riemann, H Teat canal diameter and other cows factors with possible influence on somatic cell counts in cow milk. Acta Vet.Scand. 30: Klaas, I.C., Enevoldsen, C., ErsbØll, A.K., Tolle, U Cow-related risk factors for milk leakage. J. Dairy Sci. 88: Leitner, G., Jacoby, S., Maltz, E., Silanikove, N. Casein hydrolyzate intramammary treatment improves the comfort behavior of cows induced into dry-off. Livestock Science : Oliver, S.P. and Sordillo, M Approaches to the manipulation of mammary involution. J. Dairy Sci. 72: Painter, K. A., Leslie, K. E., Tatone, E. H Behavioural changes of dairy cows during drying off using abrupt cessation of milking. First North American Conference on Precision Dairy Management proceeding. 11. Persson, Waller K., Westermark, T., Ekman, T., Svennersten-Sjaunja, K. Milk leakage-an increased risk in automatic milking systems. J. Dairy Sci. 86: Rajala-Schultz, P. J., Hogan, J. S., Smith, K. L Short communication: association between milk yield at dry-off and probability of intra-mammary infections at calving. J. Dairy Sci. 88: Rovai, M., Kollmann M.T., Bruckmaier, R.M Incontinentia lactis: Physiology and anatomy conducive to milk leakage in dairy cows. J. Dairy Sci. 90: Schukken, Y. H.,Grommers, F.J., Van de Geer, D., Erb, H.N. Brand A Risk factors for clinical mastitis in herds with a low bulk milk somatic cell count. 1. Data and risk factors for all cases. J. Dairy Sci. 73: Schukken, Y. H.,Grommers, F.J., Van de Geer, D., Erb, H.N. Brand A Risk factors for clinical mastitis in herds with a low bulk milk somatic cell count. 2. Risk factors for Escherichia coli and Staphylococcus aureus. J. Dairy Sci. 74: Schukken Y. H., Vanliet J., Vandeger D., Grommers J. A Randomized Blind Trial at dry Cow Antibiotic Infusion in a Low Somatic Cell Count Herd. J. Dairy Sci. 76: Sordillo, L. M. and Nickerson, S. C Morphometric changes in the bovine mammary gland during involution and lactogenesis. American Journal of Veterinary Research. 49: Tucker, C.B., Lacy-Hulbert, S.J., Webster, R.J Effect of milking frequency and feeding level before and after dry off on dairy cattle behavior and udder characteristics. J. Dairy Sci. 92: Williamson, J.H., Woolford, M.W., Day, A.M The prophylactic effect of a dry-cow antibiotic against Streptococcus uberis. N Z Vet J. 43: Zobel,G., leslie, K., Weary, D.M., Von keyserlingk, M.A.G Gradual cessation of milking reduces milk leakage and motivation to be milked in dairy cows at dry-off. J. Dairy Sci. 96:

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