Selecting the appropriate dry cow therapy and the need to calculate the benefits of pushing for milk constituents were just two of the topics discussed at Total Dairy Expo in Carlisle.
Farmers will be rewarded with lower rates of coliform mastitis in early lactation by avoiding the use of antibiotics when drying off low cell count cows, according to vet James Breen of Nottingham University.
Drawing on previous UK research published by Dr Andrew Bradley, he said: “If a cow had a low somatic cell count (SCC) and got an antibiotic and sealant, versus a sealant alone, she was 12 times more likely to develop mastitis due to coliform infections in the next lactation.”
There was no difference in the rate of clinical mastitis in the first 100 days post-calving and although cows were half as likely to have staph or strep infections at calving, the increase in coliform cases was marked. Low cell count cows were defined as cows with no clinical mastitis or SCC recordings over 200,000 cells/ml in the last three months before drying off.
With farmers facing increasing pressure to move away from blanket use of antibiotics at drying off, this showed they could adopt a selective approach for low SCC cows with confidence, while experiencing cost benefits from less coliform mastitis and less antibiotic use.
Dr Breen said there were clear benefits from using antibiotics and sealant for high somatic cell count cows, defined as those with at least one of the last three readings over 200,000 cells/ml prior to drying off. In these cases, they would be 1.4 times more likely to calve in free of a mastitis pathogen.
When thinking about adopting a selective approach, he said you could not just ‘pluck a figure out of the air’ when it came to determining a SCC threshold for using a teat sealant alone. Instead, the decision should be made according to individual herd objectives.
James Breen: selective approach.
“Just because you have a high (bulk) somatic cell count doesn’t mean you can’t be selective, it just means you will need a different threshold,” said Dr Breen.
For example, a herd with a high bulk SCC of over 200,000 cells/ml may opt to only use sealant on cows with three SCC readings under 100-150,000cells/ml. But in low bulk SCC herds under 200,000 cells/ml, cows with cell counts under 200,000 cells/ml could get sealant alone, and in very low cell count herds this threshold could even be increased to 250,000 cells/ml.
The key was to adopt appropriate herd testing to determine SCC levels. Continuing to pay attention to environmental management during the dry period to prevent new infections, and adopting scrupulous drying off practices, was also essential. Dr Breen added a selective approach could result in a slight rise in bulk SCC, but this was not necessarily a bad thing.
“What is becoming quite evident is SCC can be too low. The mammary environment is not supposed to be sterile. Sitting at 20-50,000cells/ml at quarter level is not such a bad thing. It represents quite a stable population. If we disturb this, it could lead to the establishment of major pathogen infection.”
Dairy farmers need to do the maths based on their specific milk contract before pushing for extra milk fat and protein, otherwise they could actually be worse off, warned EBVC’s vet nutritionist consultant Will Tulley.
“Before making changes, be very clear as to how your milk contract works. The highest price per litre is not necessarily the highest financial return,” he said.
Using rough calculations he worked through an example to demonstrate an increase in butterfat did not always pay due to the compensatory loss in yield.
If milk price was 22ppl and butterfat payment was 2.5p per 1%, and a herd averaging 25 litres had a 0.2% increase in butterfat, they would gain 12p per cow.
However, they would be likely to lose a litre of milk per cow, worth 22ppl, so having the extra litre would be more beneficial. And adding C16 fat to the diet to increase butterfat must also be costed carefully as the cost could outweigh the benefit.
In order to hit the optimum milk constituent levels of a specific contract, Mr Tulley emphasised the need to carefully select feed inputs.
“If you are offered feed which looks cheap on the face of it, you need to be aware they might negatively affect milk constituents and milk price,” he said.
For example, he said high fermentable carbohydrate and high unsaturated oil feeds could detrimentally affect milk fats. High levels of polyunsaturated oils in particular could dampen milk fats (for example in maize distillers), while ‘cheap’ feeds such as confectionary products, which were volatile carbohydrate sources, could do the same.