If actual performance is much less than this then investigation is warranted to determine where to concentrate on improving performance. Each herd manager should establish reasonable goals for the herd and the personnel doing the work. To better understand where these figures come from and what they indicate, let's break the cow year down into its components. Cows need 50-60 days dry for the mammary gland to recuperate from the previous lactation and to prepare for the next lactation. If they have much less than 50 days dry their production will be lower in the subsequent lactation and if the dry period is much longer maintenance costs will be higher and the cows will tend to get too fat.
Fat cows are prone to more metabolic problems and lower production.
The average gestation length for a Holstein cow is about 280 days which leaves about 110 days for the cow to recover from calving and get pregnant if she is to have a 330 day lactation or 390 day calving interval. If some of these figures seem too high then it will be worthwhile to examine where the problem lies. On most dairies the VWP is 50-60 days. Cows bred less than 50 days in milk are likely to have lower fertility. If we use 50 days as the VWP, then we have 49 days to get the cow pregnant, as shown above.