MANAGEMENT PROTOCOL OF MASTITIS ON SA DAIRY FARMS.

Discipline: mastitis; Key words: diversity, management practices, antibiotics, pre-dip, strip, bulk milk somatic cell count, AMR. 

The South African dairy industry shows immense diversity when it comes to mastitis management practices. However, if consistently executed, which should improve udder health and milk flow, it could be satisfactory, but supporting the diversity by extension is a challenge. As is the case globally, the dairy industry is aware of and actively addressing antimicrobial resistance (AMR). To that effect, a survey was funded by Milk SA to record what practices are followed and a project: ‘Resistance to Available Antibiotics in Lactating Cows with Mastitis’, was initiated in 2015. The results of the survey were published by the authors cited below. 

Four dairy regions were arbitrarily chosen for the survey, roughly equating to the provinces of Western Cape, Eastern Cape, Kwazulu-Natal, and the remaining provinces combined into a ‘Central Region’. An online survey was deployed to the MPO members of approximately 1700 dairy farmers in April 2016. Twenty of the surveyed farms, milking more than 200 cows, were selected at random, five from each dairy region, for on-site visits where further data was collected. A software application (iPrep) was used to measure the timing between milking routine steps. 

Following vetting, 147 surveys were eligible for analysis. Herd size for the survey averaged 449 ± 424.6 (SD) and was similar irrespective of the management type – pasture only (49%), pasture with concentrate and/or total mixed ration (TMR) (35%) and TMR only (16%). Jersey’s and Holsteins were equally represented. A wide variety of parlour types are in use, with swing-over, herringbone and rotary being the most common. When asked to describe their management style, an equal percentage of dairy farmers considered themselves either low input - lower production or high input - higher production farms, relating to the intensity of their management. The average milk production was 18.2 l per cow per day, the average butterfat 4.24 % and average protein 3.54 %. 

Approximately 50% of dairy farms pre-dip, lower than in some other parts of the world and approximately a third of producers either do not strip or wipe and/ or do not use gloves. Timing between individual steps of the milking routine was erratic within and between most of the dairy farms visited. Allowing for an ideal stimulation time of between 60 to 120 seconds, only 11.1% of rotary and 18.2% of other parlours were in this range. The average bulk milk somatic cell count (BMSCC) was 287 ± 98 x 103 (SD) and were similar across management types and regions. About two-thirds of farmers routinely identify cows with an elevated SCC, either by testing individual cows and/or groups. Of these, two-thirds consider cows with a SCC of more than 500 000 cells per ml eligible for treatment. Udder cleanliness reported in the survey was similar to that recorded on the herds visited. The regular trimming of tail switches is implemented on roughly two-thirds (65.2%) of dairies, yet only 1.0% reported clipping or flaming udders. The mastitis incidence of 31.8% was higher than the median of 20% to 25% seen elsewhere in the world and ranged from 3.5% to 93%. The average cull rate due to mastitis was 6.9%, which is lower than the target upper limit of 15% and ranging from 0.7 to 27.8%. Milk samples for culture and microbial identification were collected on 29.2% of farms and 20.2% requested antimicrobial sensitivity, which is lower than in the USA where 68% of dairy farmers always or at least some of the time submit samples for culture and identification. In this study, the majority of dairy farmers treat mastitis with intra-mammary antibiotics (86.3%), of which half also use injectable antibiotics (49.3%). The three most commonly isolated mastitis causing bacteria reported were, in decreasing order, Staphylococcus aureus, Escherichia coli and Streptococcus uberis. In contrast, bacteriology of high cell count, normal appearance milk showed coagulase-negative staphylococci, Staphylococcus aureus and Streptococcus agalactiae as the most common. One-fifth of dairy farmers reported using antibiotics in an off-label manner (including higher dosage, shorter treatment intervals and/or an extended duration of treatment), and not always doing so under the supervision of a veterinarian. The efficacy of using of injectable antibiotics, at 49.3%, must be questioned.

In conclusion: The results of management procedures to control mastitis are disturbing. In addition, dairy farmers’ attitudes toward mastitis are alarming, with only a third testifying that they had enough knowledge of the condition. There certainly is a need for systematic extension and training as mastitis is costing the industry millions.  

Reference: 

N. Schlimmer, L. Leenaerts, H.Hogeveen & M. van der Leek, 2018. The reality and perceptions of the South African dairy farmer regarding mastitis in 2016. IDF Animal Health Report • Issue N°12, 30-32