Veterinary Medicine Extension,
School of Veterinary Medicine,
University of California,
Davis, CA, USA, 95616.
Following calving the uterus must expel the fetal membranes and fluid that surrounded the calf, reabsorb the small concentrated button-like areas where the calf and mother exchanged nutrients and oxygen, repair the uterine lining, and shrink to a size ready to accept the next embryo. The normal uterus will lose more than 80% of its pre-calving size within the first two to three weeks post-partum. The process controlling this recovery is complex, and filled with a variety of control systems sending signals between the glands in the uterine walls, the ovaries, several areas in the brain, and the adrenal glands (located by the kidneys). Other hormones, such as oxytocin (which is associated with milk letdown), also play a role in recovery. Plenty can go wrong, but I'm always amazed at how much goes right, frequently in spite of rather than because of what we human caretakers do.
The rate of involution, a term that encompasses uterine shrinkage, fluid loss, and tissue repair, is an indicator of the overall status of the recovery. Anything that slows involution will delay or prevent a successful subsequent pregnancy. Traditionally, we caretakers have concentrated much of our effort on dealing with uterine infections by using antibiotics and other treatments as we attempt to "cure" them. The most frequent question asked of most dairy veterinarians is "Which medicine should I use, Doc"? Many of the most popular concoctions have romantic or powerful names, pretty colors, secret ingredients, and a long list of testimonials singing their praises. The frustration associated with trying to get that good cow pregnant drives' dairy farmers to attempt anything, even when it makes neither medical nor economic sense.
Most cows will have their uterus become contaminated at the time of calving and subsequently develop an infection. The cervix, the valve that seals the uterine interior from the outside environment, opens wide at calving to allow the calf to pass, thereby admitting whatever bugs are in the neighborhood, and the neighborhood has plenty. Multiple bacteria types, including the coliforms, Streptococci, Actinomyces pyogenes, Fusobacterium necrophorum, and Bacteroides melaninogenicus, are found in uterine cultures during the post partum period. It is not unusual to find bacteria present in more than 90% of uterine samples at 15 days after calving, close to 80% at 30 days, 50% at 45 days, and about 10% at 60 days. You might conclude that with these kinds of infection rates you should treat everything with antibiotics or antiseptics immediately. Don't.
Why not? Because across-the-board treatment is not in your cow's best interest, nor is it in yours. The first problem is in selecting which therapeutic product to use. Do you know there is an infection? Do you know that the infection will be most effectively treated with antibiotics? Do you know which bugs are involved and which antibiotics they are sensitive too? You name it, someone has infused it, and I can find someone who will swear by it. Unfortunately, research shows that such treatments may be harmful if measured by the success of the next pregnancy. Other non-antibiotic products, including uterine boluses, antiseptic infusions, and hormone treatments have been promoted and defended, but all of these treatments lack definitive research results proving their benefits.
Antibiotic residues are another issue associated with treatment. Antibiotics infused into some cows uterus act a lot like antibiotics injected into muscle, but with less predictability.They move into the blood, course through body organs, and find their way into milk. Residues are always a concern, both in meat and milk, following uterine infusion. The only question is when will they be there and whether they will be at a violative level. Systemic treatment of uterine infections, using either IM or IV regimens, also has its advocates, and has similar residue concerns.
Why can't we develop the data to answer the questions about treatment definitively? One reason is that interpretation of results is difficult. There are three potential outcomes to any treatment; the treatment may help and improvement will follow; it may have no beneficial nor detrimental effect; or the treatment itself can be detrimental. All three can happen with a single treatment when used on different animals within a herd simply by chance, and it requires well-designed trials comparing significant numbers of treatments with untreated controls to recognize the real effects of any given medication or therapy.
We also suffer from an inability to precisely identify those animals in need of therapeutic assistance from their herdmates that can recover without help. The high percentage of positive culture results from uterine samples shows the poor specificity of that test in identifying animals in need. Many of these "infected" animals, when left untreated, recover and display excellent fertility. Rectal palpation, vaginal examination, discharge evaluation, fever, appetite, and other methods are commonly used to identify and initiate therapy in poorly involuting animals, but they are not perfect. The earlier you examine the animal, the more imprecise the decision to treat or leave alone can be, and you will end up treating many that did not need it, a disadvantage to your economics and your cow's fertility. This imprecision also leads to claims of fabulous recoveries (because they would have been OK without treatment anyway), and a false sense that a particular therapy is wildly effective. An example of this dilemma may be helpful in visualizing the point: If I told you that two dairies of the same size had different abortion rates last year, and although Dairy A's rate was two percent higher than Dairy B's, I concluded that Dairy A was in better shape than Dairy B, would you disagree? Would you change your mind if I added that Dairy A had 55% of the herd pregnant, and Dairy B only had 30%? I am sure you will agree that pregnancy is an essential qualification for risk of abortion. The same problem exists with treatment trails; if we do not know which animals really need therapy, and mix in many that do not, we create a difficult problem of interpretation. I have always felt that if "recovery rates" for treatment of infections, cystic ovaries, etc., were high, say more than 50% at a two-week recheck, then I probably treated many animals that did not need it.
Next question--how are you going to evaluate the results? Part of the confusion in evaluating various treatment's result from our inability to routinely select the correct goal of therapy. What yardstick are we going to use to measure success? When I was working as a milker we used to call the vet to come out and "clean" cows with retained fetal membranes. Our yardstick of success was to eliminate the tail switch from stinking so that whenever she hit us in the face she would not transfer that not-so-wonderful odor. By this measure manual removal of a retained placenta was a smashing success, and was a common practice, until some smart person looked at its influence on days open and found treated animals were significantly and adversely affected. We were simply using the wrong yardstick to evaluate the therapy. Need another example? Twenty years ago or so veterinarians were regularly called to bring anestrus cows into heat, and occasionally they used an injection of a hormone available then that resulted in the cow aggressively riding others. It worked--if a cow acting like she was in heat was your goal. We know now, however, the use of that product was counterproductive if you wanted a pregnancy.
I recommend against treating every cow's uterus. In my experience the routine use of uterine boluses creates problems where none existed, and simply stopping that practice will improve herd fertility. Similarly, routine uterine infusions delivered to "normal" animals' result in increased days open in the herd. In my hands it appears that a single uterine infusion in heifers early in the post partum period will add eight additional days open without any improvement of conception rates or numbers getting pregnant. There is ample evidence to be concerned that most treatments administered to normal cows will result in increased days open, and that our ability to identify normal is imprecise. Additionally, there is no clear scientific evidence that any given treatment is beneficial to the majority of animals being treated.
Animals that are off-feed, feverish, with very thin watery and foul smelling discharge, need and will benefit from the appropriate therapy, and I acknowledge that many uterine problems can be treated with improved performance as the outcome. My point is simply that your time is better spent preventing the problems in the first place, with proven effectiveness, rather than spending your time, money, and effort using treatments that do not always result in improvement, and may be detrimental to the animal's subsequent performance.
There has been an explosion in our understanding about how to maintain a healthy uterus under commercial dairy conditions. Prevention management practices allow us to reduce the number of animals needing treatments to less than 25% in most commercial herds, and much lower in exceptionally well managed herds. Cow fertility is significantly improved in animals that never need treatment versus those that do. A "perfect" therapy will return a cow to the level of normal performance, and that goal can be more economically achieved through practicing prevention. Prove this to yourself by comparing days open, services per conception, and culling rates for animals that deliver live calves unassisted, do not retain their placenta, receive no treatment, and are pregnant within two services (my definition of normal) against their treated herdmates.
We now know what many have long suspected. A relationship exists between poor fertility and many other cow problems. The risk of poor fertility is increased if the animal has any one or combinations of: milk fever, prolonged but unassisted calving, assisted calving, retained fetal membranes, prolapsed uterus, mastitis, ketosis, fat cow syndrome, displaced abomasum, unsanitary calving conditions, or unnecessary post partum treatment. The key management points to prevent these conditions revolve around: energy and protein balance; control of rapid weight gain or loss; proper body condition at calving and into the early lactation period; calcium and phosphorus balance; anion/cation dry cow ration balance; trace mineral and vitamin balance; calf size (sire selection); sanitation at calving; and post partum treatment methods.
Heifers must be of adequate frame size, with proper body condition, to deliver a calf successfully while supporting their needs for growth and milk production. High rates of anestrus heifers in the first 70 days of lactation (which were at their proper frame and body condition at the time of calving) represent a ration imbalance or unsuccessful competition with older cows at the feed bunk, or both.
The preparation for the following lactation in cows begins in the last third of the previous pregnancy.This is the time to monitor body condition carefully and adjust rations to achieve ideal condition. An extra bonus to good management during this period is that it is also the most economical time to put weight on animals that are under conditioned, and to take weight off those that are over conditioned.
We now know that our old recommendation to have cows at a body condition score of four+ (on a five-point scale) during the dry period represented the use of the wrong yardstick. It may have prevented them from getting too thin during their first 1/3 of the following lactation, but also lowered both their production and fertility. Cows should be dried at body condition scores of 3 to 3.5, and calved at 3.5, for maximum production and fertility. Rapid changes in weight, in either direction, are likely to result in fat cow syndrome, which can result in delayed involution, increased uterine infection rates, and poorer recovery.
Resist the temptation to dispose of that junk feed you have got laying around by feeding it to your dry cows. These are your most important cows on the farm, and the dry period is the most critical time influencing their next lactation. The ration needs to be carefully balanced for energy, fiber, and quality protein to give the cow the ability to deliver a healthy calf, recover from pregnancy, and reach her maximum potential production. Adequate trace minerals and vitamins are essential. Prevention of heat stress, corral maintenance to promote feed intake, sanitary bedding, adequate water, and all the other well known husbandry requirements that are frequently missing from dry cow pens are money makers if you use the right yardstick as your goal.
Applied Dairy Science Course - University of Alberta:
Managing Reproduction in Dairy Cattle
Alberta Dairy Management Fact Sheet:
Getting Cows Bred - 1. Preparing cows for high conception rates