Milk fat depression
Milk fat can fall by up to 50 % while yield and the other components stay the same. On the cheque it is money; in the cow it is often the first sign of a rumen problem.
What it is
Milk fat depression (MFD) is a reduction of milk fat content — by up to 50 % — while milk yield and other milk components remain unchanged.
What causes it
- Diets high in easily fermented carbohydrates or plant oils, which change rumen fermentation and reduce the precursors for milk fat.
- Ruminal acidosis from excess fermentable carbohydrates.
- Shifts in the rumen microbial population.
- Heat stress, which lowers dry-matter intake and alters rumen fermentation.
- Metabolic disorders such as ketosis or fatty liver syndrome.
- Management stress — abrupt changes in diet or feeding schedule.
What it costs
Lower fat content, and possibly a lower milk price, reduce income directly. Severe cases linked to acidosis, abomasal displacement, laminitis or mastitis need complex treatment and sometimes end in culling.
How HerdLine detects it
The analyser measures each cow's milk at every milking. HerdLine flags MFD when the fat-to-protein (F/P) ratio drops significantly, taking into account milk yield, other milk parameters, breed and stage of lactation.
Prevention
- Limit highly fermentable carbohydrates and plant oils in the diet; consider buffers or other rumen modifiers.
- Increase dietary fibre to support rumen health.
- Monitor milk fat and the other components regularly to see whether the changes work.
On the farm
One cow's fat fell to 2.7 % on 15 October with no clinical signs. On 17 October a veterinarian diagnosed subclinical mastitis and treated her. She recovered within a few days — visible on her lactation graph in HerdLine.