Why Cows Don't Get Pregnant - Continued

Farm Journal, Inc. ( “Pre-calving nutritional management is the only way to robustly improve subclinical hypocalcemia,” says Cornell University's Tom Overton. )


Research shows anestrus cows during the first nine weeks after calving ate between 5.5 lb. and 7.9 lb. less feed per day than cycling cows. Cows that cycled the earliest had the highest dry-matter intakes during the first two weeks after calving. The same cows started recovery to a positive energy status immediately after the first week in lactation.

Anestrus cows showed a more negative energy state during the second week after calving than the first week. Therefore, the difference between the intake of the cycling cows and the anestrus cows was greater during the second week after calving than the first week. This negative energy status during the first few weeks after calving seems to carry over and affect the conception rate later on, affecting overall reproductive success. 

Any infectious or metabolic disease that affects dry-matter intake early in lactation will have a subsequent affect on the cycling and fertility of lactating dairy cows. Once again, the importance of a good close-up dry cow ration and management program in preventing metabolic disease in the fresh cow needs to be emphasized. 


Calcium is necessary for all muscle contraction, including the muscles of the gastrointestinal tract (GI tract). If blood calcium levels are low, the contraction of the muscles in the GI tract are less frequent. This slows down feed passage and results in decreased dry-matter intakes at calving. Decreased dry-matter intake will put the animal in a more negative energy state causing more weight loss early in lactation. This will in turn have a negative effect on reproductive efficiency at breeding time.

Animals suffering from subclinical hypocalcemia will have higher incidence of infectious disease postcalving, especially with metritis. This will have an adverse effect on reproduction and delay the time to conception.

Stress and low calcium levels will both have an adverse effect on the animal’s immune system, resulting in an increased incidence of retained placenta. Basically all animals that have retained placenta will have a uterine infection, which will prolong average days open in these animals and often reduce first-service conception rate. 

Nutrition has emerged as the No. 1 reason for reproductive failure. Evaluating the cow comfort and nutrition of both the dry cows and lactating cows with your herd veterinarian and nutritionist might provide you with important information to improve reproductive efficiency on your dairy herd.


For more information on reproduction, read: