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November 18, 2004 Cattle Conception Rates – Diets Make a Difference
One of the many advantages of raising cows in the North is the fact that we seldom give up milk to cold stress. Cool temperatures are nothing like heat stress when it comes to affecting cow feed intake and milk production. Preventing a negative energy balance is a key to limiting excessive mobilization of body fat during the first four weeks of lactation, but not just for milk production. It is also of primary importance for subsequent fertility. Cows will tolerate a loss of approximately one body condition scoring unit in the first four weeks after calving. More extreme condition loss will predispose the cow to have a lower conception rate at first service. One unit change in body condition score represents about 120 pounds of body weight change and about 400 megacalories of energy. Although cool weather increases maintenance requirements, a cow's ability to eat will generally compensate. The exception can happen the first two months after calving. So, feeding management that maximizes dry matter intake is essential to minimize body condition loss and reinitiate ovarian cycling within approximately three weeks after calving. Ideally, the second ovulation will occur by 50 days postpartum, when uterine repair will be complete. According to Roy Nebel, Virginia Polytechnic Institute and State University reproductive management specialist, increased negative energy balance (intake not meeting the cow's requirements) may delay ovulation 60 to 75 days or longer, extending the postpartum effects and recovery of the uterus. The stimulation of appetite to ensure adequate dry matter intake in normal, healthy cows is essential to provide nutrients for maximum milk production, follicular growth, ovulation, uterine repair and the initiation of pregnancy. First ovulation usually occurs approximately 10 to 15 days after the point of greatest negative energy balance and sometime before the peak in daily milk secretion. In research trials, dairy cows with greater dry matter intake, despite having a negative energy balance, produced more milk, lost less body weight and ovulated earlier postpartum than those with lower intakes. Additionally, cows with greater intakes also reached their low point of energy balance earlier and experienced a more severe, but shorter period of negative energy balance. The results suggest that when cows are more efficient in partitioning dietary and stored nutrients toward milk synthesis, they are also better able to recover ovarian cycling. Increased feeding frequency and better feed bunk management to maintain a fresh, adequate supply of feed and multiple sources of clean water are critical for stimulating appetite and maximum dry matter intake. ### Source: J.W.
Schroeder, (701) 231-7663, jw.schroeder@ndsu.nodak.edu |
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North Dakota State University |
