If your selection process has not changed, what other management practices have you changed that may influence milk production? Did you do a better job of meeting the cow's nutrient requirement after calving, especially energy needs, which can affect milk production? Did you change calving season so that cows calve closer to when the spring grass resource is available? One observation is that in our summer-calving experiment, there seems to be more teat and udder problems in that herd, and our summer-calving cows are the same genetics as the March-calving cows. In the summer-calving cows, the vegetative grass more than meets the nutrient needs during early lactation, and if there are udder and teat problems, they are exposed in the summer-calving cows.

Over the last four or five years, has calf weaning weight increased? If you have not creep-fed the calves, the ways to increase weaning weight is to select for more growth, select for more milk, or select for both. There will be some variation in weaning weight if you haven't selected for more growth and/or milk based on summer weather conditions that affect grass growth. But if you have had a substantial increase in weaning weight and you haven't selected for growth, then milk production has increased. As you increase milk production, the chances increase for unacceptable teats and udders and having to milk out females after calving. One concern is that it is showing up in the young cows, which leads me to think genetics is involved. So have you started to incorporate genetics into the herd that increases milk potential?