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        Knowledge for the CommonWealth

Reproductive efficiency is still very important!!!

Dairy Pipeline: July 1996

by Ray L. Nebel
Extension Dairy Scientist
Virginia Tech

The Virginia State average for days open in DHI herds was 148 days in April of 1996. This is 10 days longer than last year at this time and the highest days open for Virginia DHI herds that anyone can remember. The comment is often made that having a low days open or a 12 month calving interval is not as important as it once was. A cow with a 14 month calving interval would have to average 65 lbs per day to give the same production as a cow with a 12 month calving interval averaging 78 lbs per day. The 14 month calving interval requires 60 days of additional feeding, milking, and handling to equal the same amount of milk with 20% fewer calves born, thus less voluntary culling and less cull cows and bull calves to sell. If profitability is to be maximized a high level of reproductive efficiency is required. Three areas of performance must be evaluated to determine why long calving intervals exist; (1) average days to first service, (2) heat detection, and (3) conception rate. Additionally, the profile or distribution of all cows not just the average is essential to determine if a few cows are influencing the records to have them appear better or worse than the situation really is. In other words, two herds could have the same days to first service, but in one herd, first services range from 45 to 130 days, whereas cows in the second herd range from 60 to 100 days. Obviously, the second profile is best for proportionally more cows. Heat detection is the one area that needs more attention. Average days to first service has now been extended past 90 days and is a major contributor to extended days open. However, the lack of heat detection is probably the major cause of extended days to first service. Motivation to observe cows often for sign of heats is a key that is lacking on many farms. Most dairy operations can improve production and net income substantially by improving the reproductive performance of the dairy herd.

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