Every cow's milk follows a predictable shape across her lactation. Learn to read that shape and a glance at the curve tells you more than a single day's figure ever could — whether she's fed right, healthy, and earning her keep.
The three phases 1. Rise to peak (calving to ~6–8 weeks) — milk climbs fast after calving. The height of the peak largely sets the whole lactation: a rough guide is that **each extra litre at peak is worth ~200 litres over the full lactation.** This is why fresh-cow management matters so much. 2. Peak and early decline (~weeks 6–12) — she holds near the top, then begins a gentle, steady fall. 3. Persistent decline to dry-off (~month 3 onward) — milk falls roughly 8–10% per month. A flat, slow decline ("good persistency") is the mark of a well-fed, healthy, well-managed cow.
The mismatch you should know about A cow peaks in milk at ~6–8 weeks but peaks in feed intake later, at ~10–12 weeks. That gap in early lactation is negative energy balance — she's literally milking off her own back fat — and it's why ketosis, poor fertility, and weight loss cluster in fresh cows. The curve explains the disease pattern.
Reading the curve to spot problems - A sudden drop off the expected curve = investigate (mastitis, illness, heat, feed change — see "Why has my cow's milk suddenly dropped?"). A gentle expected decline is normal and needs no action. - A low, flat peak = the cow didn't get going after calving — transition-cow or feeding problem. - A steep decline (poor persistency) = often under-feeding for her stage, or sub-clinical disease dragging her down. - Heifers have a lower, flatter curve than mature cows — that's normal; compare like with like.
Why this matters in Vache With 30 days of milk records, the platform can draw a cow's curve and compare it to where she should be. A cow with no recent milk data is a blind spot — you can't tell a healthy decline from a problem. Logging daily (or even regular) yields turns raw numbers into a curve you can actually manage by.
Using the curve for decisions Curves guide when to dry off (yield falling below the point where she earns her feed), which cows to cull (chronically low, poor-persistency animals), and whether a feed change is working (the curve should lift or flatten).
Sources Penn State Extension — The Lactation Curve. AHDB Dairy — Lactation Persistency. University of Minnesota — Energy Balance in Early Lactation.