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Dairy Pipeline: June 2005
Ray L. Nebel
Dairy Extension Coordinator,
Reproductive Management Scientist
(540) 231-4432 email: rnebel@vt.edu
Only once in the last 20 years has a dairy producer told me he had "Too many Pregnant cows" and that is another story I do not have time to get into for this article. Reproductive performance is a function of certain management policies and how well these policies are implemented in the day-to-day management of the herd. Excellent reproductive performance is essential to the long term success of a dairy operation. Throughout a cow's herd life, she should calve without difficulty, experience little or no postpartum reproductive disease, breed back within an optimal time period, carry each fetus to term, and have a live birth. The management team of a particular dairy must decide the specific methods to be used to meet this goal. Together the methods selected will become the reproductive management program for that particular dairy. These methods may include such approaches as chalking tail heads, activity tags, controlled hormone synchronization and timed AI, and I can go on and on. My point is "one-size-does-not-fit-all" when it comes to reproductive management in today's dairy industry. This week I visited six Virginia dairy farms where the herd size ranged from 110 to 750 milking cows and no two farms had the same reproductive management program and all were below the state average for days open and above the state average for 21-day pregnancy rate. A key to their success in my opinion was an excellent nutrition program and housing that produced exceptional cow comfort. The free stalls ranged from "waterbeds" to sand with two having bedded packs but the key was they were all very well managed. Getting cows pregnant is a two-step process. First, cows need to be detected in heat so they can be inseminated at the appropriate time or a controlled synchronization program used with either re-synchronization or visual submission for subsequent AI. Then, insemination needs to result in conception. A general rule is that at any given time 50% of the herd should be confirmed pregnant. Approximately 8% of the herd should become pregnant each month to maintain a consistent herd size without the purchase of replacements. So, the average 150 cow milking herd requires 12 new pregnant cows monthly. If the average conception rate is 35% then 34 cows need to be inseminated to achieve 12 new pregnant cows monthly. During the period of summer heat stress when conception rates commonly drop to 20% to achieve 12 new pregnant cows 60 cows must be inseminated. Most dairy producers would like to have more pregnant cows. They would also like to have more cows pregnant soon after the end of the voluntary waiting period. However, reproductive performance is a result of several aspects of the dairy operation and there is no easy road to reproductive success or I would have retired long time ago.