Cattle Today

Cattle Today



by: Stephen B. Blezinger
Ph.D., PAS

There is one absolute fact that is central to the cow/calf sector of the beef industry. In order for an operation to “work” you have to get cows bred and get them bred efficiently. Virtually everything revolves around this factor because if this does not take place, nothing else does either. Most breeders do a reasonable job of getting cows bred in a timely fashion but unfortunately many do not. Good breeding is a factor of genetics, health, nutrition and management. Many producers will try to prioritize these four factors with the thought that, “if I do a good job on health, the others will fall into line.” Each of these are of equal importance because if one component is lacking the whole system falls apart. This article will discuss some opportunities a producer has to enhance his reproductive performance and efficiency.

The Basics

Always go back to the basics. This means that your program needs to be based on sound genetics, health, nutrition and management and your program must be complete in each of these areas. This means:

1) Selecting cows and bulls that are of genetic stock where reproductive performance has been prioritized.

2) Working with your veterinarian to develop a complete health program that will have a focus on reducing or eliminating reproductive diseases. This will mean a regularly and properly scheduled vaccination program. It also means regularly and closely observing cattle to watch for illness, injuries or other irregularities that must be treated in a timely fashion to prevent more extensive or longer term problems that can effect reproduction.

3) As in all stages of beef production nutrition is critical and not only one or two components such as crude protein or fat. ALL nutrients must be balanced and in the correct volumes and proportions to one another. Even one nutrient that is deficient can act as a performance limiter. As we have discussed in the past, systemic performance in cattle is prioritized, meaning the less essential systems will be shut down first in the event of a nutrient deficiency to insure the continued operation of more critical processes. Reproduction is generally the first system to shut down. Finding and working with a qualified nutritionist can help you streamline this program and insure you are covering all your bases.

4) Overall management oversees all these components and also brings in other tools such as fertility testing of bulls, heat synchronization (HS), artificial insemination (AI), embryo transfer (ET) and so on.

A breeding operation must have ALL these components in place before any “enhancement” techniques can be effectively utilized. Remember, as with all things, there are NO Silver Bullets, no Band-aids that can be applied that will overcome shortages on any of the four standard components listed.

Under normal operating conditions, if all of a breeding operations bases are covered it is not uncommon to get breeding efficiencies in the upper 80's to lower 90 percentages. This means that in a given production cycle this is the percentage of cows that will breed or conceive and produce a weaned calf – conception to weaning. Subsequently, the remaining percentage does not breed or at least does not breed within the indicated time frame, i.e. it takes them longer to come back into heat and ultimately conceive than desired. This does not allow for cows that lose a calf during pregnancy (abortions), lose the calf during parturition (dystocia) or lose the calf between calving and weaning for any of a number of reasons. We are talking about cows or heifers that fail to breed or breed in a timely fashion.

Let's put this in perspective. Let's say a producer has 100 cows and his conception to weaning efficiency is 85 percent. That means that he has 15 cows that did not produce a calve during a normal production cycle. For arguments sake we'll say these cows simply did not produce at all. This means that the rest of the herd has to cover their annual expenses. Typical annual carrying expense (this number is highly variable) is about $300 per head per year. This means that the other 85 have to absorb the cost of the 15 that did not produce. In this case this number is $4,500 which means your production costs for the 85 that did produce went up $52.94 per head, a 17.64 percent increase in your production cost. Additionally, since the producer did not have these 15 calves to wean, he also lost these revenues. If his average weaning weight is 500 lbs, on today's markets (average price about $1.25/lb.) his lost revenue per head is $625 or a total of $9,375. Between the added cost and lost revenues, this producer, with an 85 percent calf crop is losing $13,875. Compare this to other performance levels in Table 1 below:

Table 1. Economic Comparison of Conception to Weaning Efficiencies.
(Based on a Herd of 100 Head)

Conception to Weaning Percentage                           85                           90                         95         Total Added Cost                                                   $4500.00                  $3000.00             $1500.00
Production Cost per Prod. Animal                          $52.94                      $33.33                 $15.78 Total Lost Sales Revenue                                     $9375.00                 $6250.00             $3125.00 Total Losses                                                         $13,875.00                 $9250.00             $4625.00    

As you can see the losses are reduced dramatically when reproductive efficiency improves. A 10 percent improvement in calving percentage will result in a 66.67 percent reduction in total revenue losses for a 100 head breeding operation based on these assumed values. If total productioin cycle per animal unit lost is $925.00 ($300 + $625) over 15 months then annual losses are equal to $740 ($925/15 * 12 months). Thus it becomes obvious that it is cost effective to take steps to improve reproductive performance.

Strategies to Enhance Reproduction

While many techniques are available that can manipulate reproduction (heat synchronization, A. I., ET) most of the opportunities to enhance reproduction are nutritionally related. Let's take a look at a number of these:

1) Bull Management – managing bulls on many operations seems to be an afterthought. Many commercial producers seem to believe that as long as they have some sort of male bovine out in the pasture with their females, they have it covered. This could not be farther from the truth. Remember that your bull is ½ of each calf and that it takes a fully functional bull to get cows bred in an appropriate period of time. Additionally, since one bull can sire 10 to 40 calves (limited breeding season. One bull can handle more if allowed access to the herd for longer periods of time), he has a profound effect on the breeding efficiency and, as importantly, profitability of the herd. For instance, if a commercial producer does his homework and carefully selects a bull to enhance his calves weaning weights he might realize significant increases in these weights. In this situation, he might increase his weaning weights by 50 lbs per head. Using the $1.25 figure from above this means that each calf is worth $62.50 per head more than the previous year with a lesser bull. This means if he gets 40 head bred the additional revenues generated would equal $2,500.00. If this bull is carefully managed bis productive life could be 5-8 years. With an average productive life of 6.5 years this would meant that this bull could generate an additional $16,250 over his lifetime. Thus selection of genetically superior animals that may cost more ($3,000-$4,000 per head) makes economic sense as compared to buying a bargain basement special for $1000 at the auction ring.

As mentioned, bulls need to be cared for properly, paying attention to their health and nutrition. Body condition is as important in bulls as it is in cows and thus, bulls need to be properly conditioned (but not excessively fat) when they are put with the cows for the breeding season. Aggressive bulls will forgo eating in many cases to pursue breeding activities meaning that nutrient intake is down and that they will loose weight as the breeding season proceeds. They need to be in adequate condition going in so that they can breed as effectively toward the end of the season as they do at the beginning.

Bulls should also be fertility tested by your veterinarian prior to the breeding season. There is nothing worse than placing a bull who is infertile with a group of cows only to wonder why, 2/3 of the way through the breeding season, all the cows in a given group still seem to be cycling. A simple trip to the vet can confirm that your bull(s) are sound and is very cheap insurance.

2) Use of Ionophores. Funston (2006), in a paper given at the Applied Reproductive Strategies in Beef Cattle Conference, reported that the use of ionophores (RumensinTM and BovatecTM) have been shown to influence reproductive performance during the postpartum period. Remember that ionophores are a feed additive that improves feed efficiency and gains (by changing rumen fermentation patterns), thus they allow for improved energy utilization by the animal from feeds and forages. Cows and heifers fed an ionophore exhibit a shorter post partum interval (shorter time between calving and rebreeding) provided adequate energy is supplied in the diet (Table 2, Randel, 1990). This effect appears to be more evident in less intensely managed herds that generally have a moderate (60 to 85 days) or longer postpartum interval. This simply means that if you already have a reasonably short PPI (i.e. 30 to 60 days) you may not see as much of an effect. Researchers have also shown that heifers fed an ionophore reach puberty at an earlier age and a lighter weight.

Table 2. Effect of Ionophore Feeding on Postpartum Interval (PPI) in Beef Cows and Heifers

                Study                       Ionophore                      Control                           Difference
                                     (PPI, days)                    (PPI, days)                          (days)
               1                                 30                                   42                                      -12
                   2                                 59                                   69                                      -10
                   3                                 67                                   72                                        -5
                   4                                 65                                   86                                      -21
                   5                                 92                                 138                                      -46

3) Fat Supplementation. A great deal of work has been conducted over the last few years on the effects of feeding fat to enhance reproductive performance. It is well known that inadequate energy intake and poor body condition can and does negatively effect reproductive function. Supplementation of fats has been used to increase the energy density of the cows diet in general and avoid undesirable, negative associative effects that are sometimes seen when high grain supplements are used in conjunction with a forage or roughage based program.

Supplemental fats may also have positive effects not associated with energy contribution. Dietary fats have been shown to positively affect reproductive function by roles played at the hypothalamus, pituitary, ovary and uterus, i.e. primary sights of hormone production. This appears to be related to the type of fatty acids making up the dietary fat (remember that overall dietary fats are made up of smaller units called fatty acids just as proteins are made up of smaller units called amino acids).

The use of supplemental fats has been investigated at a variety of production stages and a variety of responses have been noted. Consider the following:

a) Fat Supplementation to Replacement Heifers – Studies in this area are, in fact, somewhat limited. Fat supplementation appears to have a positive on breeding of heifers when they have been nutritionally challenged. Well developed heifers and those on a suitable plane of nutrition have shown limited responses to feeding of fats

b) Fat Supplementation Prepartum (Prior to calving) – A study by Hess in 2003 summarized research on supplementing fat during late gestation and concluded that feeding fat to beef cows for about 60 days prior to calving resulted in a 6.4 percent improvement in pregnancy rate for the upcoming breeding season.

c) Fat Supplementation Postpartum (after calving) – Studies have shown an increase in reproductive response when feeding increased dietary fats to cows post calving. One particular study conducted in South Texas showed an increase in breeding rates in thin cows (BCS ~ 3.5 to 4) when cows were supplemented with 3 to 4 lbs of whole cottonseed per head per day.

Fat supplementation, however, may not be the answer to cow/calf producers breeding woes. Some research has shown both increases and decreases in the production of PGF2x, an important reproductive hormone. In some situations where higher fat levels are fed for an extended period of time, PGF2x synthesis is increased and this may compromise early embryo survival. As with all production components, moderation and care in use are important. A producer cannot assume that one practice will solve all his problems or that “if a little is good, a lot must be better!”


Breeding management is probably one of the cow/calf producer's most important jobs. Adhering to the basics and utilization of enhancement techniques can prove profitable to his operation. In the next part of this series we will look at additional opportunities a producer can utilize to improve his breeding performance.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, Texas. He can be reached at 667 CR 4711 Sulphur Springs, TX 75482, by phone at 903-885-7992 or by e-mail at


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