Producer Questions prior to 2009

Pregnant cows, timing of pregnancy, open cows, pregnancy rate

How long after a cow gives birth can she get pregnant again?

It depends on a number of things, body condition at calving, age of dam, if there was any calving difficulty during the calving process, and if diet is adequate after calving during lactation so that weight and body condition losses do not occur or are minimal. First-calf cows have a longer post-partum interval than do mature cows. Cows that calve in a body condition of less than 4 (scale 1 to 9) have a longer post-partum interval. Cows that have calving difficulty have longer post-partum intervals. And cows that lose weight and body condition after calving have longer post-partum intervals. So with all that in mind, the postpartum interval, if conditions are ideal, for beef cows is between 50 and 60 days for an average of 55 days. First-calvers will be at least 10 days longer.

I have some forage that is a summer annual and I tested it for nitrates. It tested on the high side of acceptable level of nitrates to be fed to pregnant beef cows. Do you have any suggestions for feeding this forage?

There needs to be some caution when feeding this forage to pregnant beef cows. If the forage is high in nitrites, then it needs to be mixed with a forage that is much lower in nitrates or a forage that does not contain any nitrates. Using other forages, the nitrates can be dilute to safe levels and fed. The easiest way to dilute the forage that has the nitrates is to grind and mix with the other forages. Keys to feeding a forage that contains nitrates: Dilute the forage that has nitrates to a safe level. Adapt cattle slowly to a forage that contains the high nitrates. Never allow cattle that are hungry access to forages that contain high nitrates.

What info is available on pine needles abortions in bred cows?

Pine needles consumed by cows during late pregnancy can cause abortion, or premature calving. Producers need to be aware that few options exist to decrease the risk of pine-needle-induced abortion other the physically isolating cows from exposure during late pregnancy. Exposure to any source of pine needles, whether they are fresh, dry, weathered, on the ground, on standing trees, or on fallen trees during late pregnancy should be avoided. The culprit is isocupressic acid, a yellow, oily substance in pine needles. Identification of the culprit is the first step in developing an antidote. As far as I am aware, the antidote is not yet available.

Can pregnant cows be vaccinated for BVD or can the vaccine be given only prior to breeding?

Pregnant cows can be vaccinated against bovine viral diarrhea virus (BVDV) using killed-virus (KV) vaccines. Modified-live virus (MLV) vaccines should be given when the cow is not pregnant — ideally 30-60 days prior to breeding. Some BVDV MLV products state on the label that they can be safely administered to pregnant cattle if the cattle had also received the vaccine prior to breeding.

Although some cattle producers prefer to vaccinate during fall work for convenience; it makes the most sense from a BVDV control standpoint to vaccinate prior to breeding so that cattle have the best protection during early pregnancy.

Looking for information on the first cycle after a cow has calf. Want to move the calving earlier in the year. Best ways to accomplish?

Not an easy task to accomplish. Usually the length of the post-partum interval (PPI, time from calving to the first estrous cycle) is 45 to 55 days in beef cows. If cows are in good body condition at calving, then the PPI would be in the 45 to 50 day range and if in poor condition, the PPI would be longer. First-calf heifers have a longer PPI compared to mature cows, about 10 days longer if she has no calving difficulty and is in good body condition. If cows are exposed to bulls (bull exposure) after calving, then the PPI is usually shorter by may be as much as 10 days shorter.

It has been documented in beef cows that uterine involution is not completed by 20 days post-calving, but the uterus is back to its non-pregnant size by 30 days post-calving. Another 10 or so days is needed to complete uterine involution and be prepared for another pregnancy. I don't think many cows will come into heat (estrus) before 35 day post calving.

You can "jump start" estrous cycles with progestins and gonadotropins (GnRH), but this will only happen in females that are close to begin cycling. There are synchronization programs for cows that use CIDR (progesterone) and GnRH (Cystorelin, Factrel, Fertagyl, OvaCyst). Use of these programs has the potential to induce estrous cycles in cows that are close to cycling.

So, nutrition is very important, have cows in at least body condition score 5 at calving and don't skimp on the groceries after calving. Ionophores such as Rumensin or Bovetec have a positive impact on the reproductive axis, at least there are experiments using the heifer that demonstrate this, so consider using an ionophore in the ration after calving. Expose cows to sterile bulls as soon after calving as possible. Jump-start the reproductive axis using a progestin and/or GnRH. These considerations are all for not if the cows have not been managed properly from a nutritional perspective.

We just preg checked the cows in our herd and we felt we had too many open cows. Is there any way to prevent so many open cows? They are given salt and a good mineral all the time. All bulls are checked before being used.

Open cows are usually due to mis-management of the nutrition program. Minerals are important, but I rarely see large reductions in reproductive performance due to minerals alone, especially in Nebraska.

Here's a check list for you to help evaluate the reproductive performance of the herd.

  1. Separate non-pregnant cows by age. Are the majority of the opens in young cows, females trying to become pregnant for the second calf. If this is the case, then more often than not, it is due the nutrition program. Calf first-calf-females in a body condition score of 6 (on 1 to 9 scale). A lot of the diets that I see for these females after calving is often deficient in energy. Grass hay and alfalfa don't not have enough energy, so you will need to added some corn, distillers, gluten, silage, etc to the diet. If there are a lot of "running" age cows (4 through 12 year olds), then this is a concern because if you have paid close attention to the genetic make-up of you herd, these cows should be of the weight and milk output that fit the resources on you operation. If the majority of the opens are old cows.......then you may have kept them to long.
     
  2. Bull to cow ratio. For young bulls, 1:12 to 1:15; older bulls 1:25 to 1:30. Did you have any breeding pastures that had only one bull for the entire breeding season? Maybe the bull was good early and got hurt or sick later in the breeding season. Did you run 2 yearling bulls in one breeding pasture? This is probably not the best management strategy.
     
  3. What was the length of the breeding season — 60 to 65 days is common. A shorter breeding season, especially in drought conditions, could result in more open females.
     
  4. Vaccination program for the cows. Consult your vet to make sure the reproductive diseases are covered.
     
  5. Did you notice any other bulls in your pasture? Trichomonisis is not common in Nebraska, but it is in some bordering states. Consult your vet to make sure this was not the cause. If you observed very few cows cycling towards the end of the breeding season, then observed cows cycling after the breeding season ended, may indicate early abortions.
     
  6. Did you have a lot of calving difficulty in the heifers? This will cause an increase in the postpartum interval and result in more opens young females.

Again, minerals are important and it sounds like you have this area covered.

What are the advantages of target breeding weight on beef industry?

Substantial research has been conducted contributing to the traditional guidelines of developing heifers to 60 to 65% of mature body weight at time of breeding. In general, studies evaluating different post weaning rates of gain or target weights have used either different amounts of feed, or different types of feeds varying in energy and/or protein content to obtain differences in rates of growth.

A review of these studies conducted over the last several decades along with new research indicates the association among BW, puberty and heifer pregnancy rate appears to be changing over time. In general, research reports published through the late 1980s have shown much greater negative effects of limited post weaning growth on age of puberty and subsequent pregnancy, whereas more recent studies indicate less of a negative impact of delayed puberty on pregnancy response. Several factors likely contribute to this change over time. Initial research in this area of interest corresponds to the industry shift from calving heifers at 3 years of age to calving at 2 years of age. Thus, selection pressure for age of puberty was probably minimal in the animals used in the early studies.

While selection intensity would have increased with the reduction in calving age of heifers, genetic progress would take time due to the long generation interval in cattle. In the mid 1980s, researchers identified the association between scrotal circumference in bulls and age of puberty in their female offspring. Since then, scrotal circumference has been used as an indicator trait for puberty. The change occurring in scrotal circumference from 1985 to the present indicates substantial progress has been made, and a similar response in age of puberty would be expected (see breed association websites for changes over time in EPD for scrotal circumference).

Indeed, the inability of heifers to attain puberty prior to breeding may not be as problematic as heifers reaching puberty before weaning.

There are data developed at the University of Nebraska were feeding replacement heifers to a traditional target weight increases development costs relative to more extensive heifer development. They reported similar pregnancy rates from the initial through fourth breeding season for heifers developed to reach either 53 or 58% of mature weight prior to breeding as yearlings. This demonstrated heifers developed to only 53% of mature weight could achieve similar initial pregnancy rates and retention compared to heifers developed to 58% of mature weight. In this data set, heifer development costs were reduced by $22 per head.

We hear stories of poor conception rates when feeding cows WDS. Is this fact or fiction?

We have recorded no negative effect on reproduction when beef cows are supplemented with distillers grains as a protein or energy source, or for both protein and energy. In a number of experiments, we have used a distillers grains based cube as a major component of the supplement that is fed to cows prepartum while grazing cornstalks or dormant native range.

Following reports provide examples of research where distiller was a part of the supplement and we recorded the impact on cow and calf performance.

Effect of Winter Grazing System and Supplementation on Beef Cow and Progeny Performance

Supplementing Gestating Beef Cows Grazing Cornstalk Residue (PDF 148KB)

We've developed replacement heifers using dried distillers grains. Heifers were fed distillers grains at 0.6% of their body weight on a dry matter basis. Distillers fed heifers had greater reproductive performance compared to the control heifers. Following is a NE Beef Report on using distillers grains in heifer development diets.

Utilization of Dried Distillers Grains for Developing Beef Heifers (PDF 108KB)

We have not conducted research investigating the effect of feeding distillers to beef cows where the distillers may be 1/3 of the diet or more on a dry matter basis. I have worked with producers where they have fed close to 1/3 of the diet being distillers on a dry matter basis to beef cows and they have not reported any negative effect on reproduction. In these cases, distillers was fed with low to medium quality forages. I most cases, at least for beef cows, I can't think of many feeding situations where you would need to feed more than 1/3 of the diet being distillers.

Always monitor sulfur and fat (when fed with forages) intake.