Milk Drop and a Positive CMT in a Crossbred Cow
Kalaivani keeps four crossbred cows in Erode. Her five-year-old Jersey cross, in third lactation, has dropped from 18 L to 13 L per day over 10 days. The ration is 6 kg paddy straw, 4 kg green fodder and 3 kg concentrate (18% crude protein) per day, plus one hour of grazing. Body condition score is 2.5 out of 5, rumen movements are reduced, dung is loose, and strip-cup examination shows small clots in the left hind quarter. The California Mastitis Test gives a score of 2 in that quarter. Rectal temperature is 38.4°C. She has not changed the feed but has started giving extra rice bran. She wants to increase concentrate to 5 kg and give antibiotics from the local shop. She asks what is wrong and what to change first.
1. What are the likely reasons for the milk drop, and what does the CMT result mean?
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There are two overlapping problems. The CMT score of 2 and clots in the left hind quarter indicate subclinical mastitis in that quarter; the normal temperature of 38.4°C argues against an acute systemic infection, but the quarter is not normal. The milk drop also fits a ration problem. The cow receives 6 kg paddy straw but only 4 kg green fodder, and 3 kg concentrate for 18 L of milk is low; concentrate allowance should be roughly 1 kg for every 2.5 L of milk plus maintenance. The extra rice bran adds energy but not enough protein, minerals or fibre balance. Rumination is reduced and dung is loose, so the ration change and low effective fibre need attention. The body condition score of 2.5 shows she is not carrying excess energy reserves.
2. What should she do immediately, and why should she not start antibiotics from the shop?
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Start with hygiene and diagnosis, not a random antibiotic. Milk the affected quarter separately and last, use a strip cup at every milking, wash hands and teats, and apply a post-milking teat dip. Submit an aseptic milk sample from the affected quarter for culture and sensitivity before treating. Giving an antibiotic without knowing the organism risks treatment failure, residues in milk and unnecessary cost. Because there is no fever and the cow is eating, acute supportive treatment can wait for the test result, but watch for fever, heat, swelling or a hard quarter. Check the milking machine or hand-milking routine for teat trauma. Improve ventilation and bedding, and keep the udder clean and dry. Record daily quarter milk yield and CMT score to see whether the quarter is improving.
3. How should the ration be corrected without causing another digestive upset?
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Correct the ration gradually over 7–10 days. Reduce paddy straw from 6 kg to about 3–4 kg and increase green fodder to 15–20 kg, so that effective fibre and moisture are better balanced. Raise concentrate gradually to about 1 kg per 2.5 L of milk plus maintenance, which is roughly 7–8 kg per day for an 18 L cow, but split it into two or three feeds. Do not jump from 3 kg to 5 kg in one day. Include a mineral mixture about 50 g per day and salt about 30 g per day, and add a bypass protein source rather than only rice bran. Provide clean water freely. Recheck rumen movements, dung consistency and milk yield after a week; if the quarter worsens or fever develops, seek veterinary treatment immediately.