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Newsletter 3 March 2018

Dear dog breeding enthusiasts

 Look at our website for more information on dog reproduction http://www.rantendal.co.za.

Semen can now be frozen on demand at our premises with as little as 1 weeks’ notice. Contact Gigi at reports@rantendal.co.za to make a booking. 

Breeding soundness evaluation of the stud and management subfertile studs

Semen quality

The semen quality is evaluated by comparing the semen parameters against a set of parameters known to be associated with good fertility. Macroscopic examinations of the volume and colour of the semen, and microscopic examinations of sperm motility, sperm concentration, sperm morphology, sperm number, pH, cytology, and alkaline phosphatase activity are usually performed.

A dog’s ejaculate consists of 3 fractions. The volume of the ejaculate will depend on the size of the stud dog and can range from 0.5 ml – 4.5 ml; 0.5 ml-4.0 ml; 2.0-40.0 ml respectively for the first, second and third fractions. The total number of sperm in the ejaculate can vary between 300 million to 2 billion. Generally, testicular size and weight is an indication of the dog’s sperm producing capacity. Scrotal width, as an indicator of testicle size, has been documented for many breeds and a stud dog’s scrotal width is then compared to known values. In a normal ejaculate, 70-80% of the sperm should be motile and 80% should have normal morphology. Sperm motility should be evaluated immediately

Poor semen quality

Poor semen parameters are frequently the cause of subfertility or infertility in stud dogs. True infertility (total inability to produce offspring) can be due to either azoospermia (total absence of sperm in the ejaculate) or severe sperm abnormalities as evidenced in a spermiogram (semen analysis). Absolute infertility is rare in dogs. Suboptimal fertility (subfertility) though, is much more common. Subfertility in the stud dog is normally associated with either: poor sperm motility, low sperm counts, poor sperm morphology or a combination of all these parameters. A reduced number of live progressively motile sperm reduces the availability of sperm for fertilisation, which in turn results in reduced fertility. This occurs because a minimum number of sperm are required to fertilise a bitch. Although the absolute minimum number of sperm required in fresh dog semen (deposited intravaginally) is not known, it is speculated to be around 100 million live progressively motile sperm. It is difficult to understand why such immense sperm numbers are required to fertilize a very small number of eggs. Nevertheless, breeders should not underestimate the importance of these minimum sperm numbers required. This is important because some studs have ejaculates of such poor quality that it is truly not worthwhile to use the dog as a stud. If breeders insist on using such a stud dog, artificial reproductive techniques might provide better results. It is also important to realise that as sperm numbers increase above the minimum number, both pregnancy rates and litter size will improve until it reaches a maximum. Under normal circumstances, given normal bitches and stud dogs, in excess of 80% of bitches will conceive and have normal litter sizes when using healthy studs with good semen parameters. In contrast, when a sub-fertile male is used, some bitches may conceive with normal sized litters but most will either not conceive or have small litters. Therefore, the fact that a particular stud dog has sired a litter, does not imply that the stud dog is optimally fertile. Veterinary surgeons are often asked to investigate why a bitch did not conceive, as she was put to a stud of “proven” fertility. In many instances, examination of the bitch reveals no abnormalities, while on the other hand, evaluation of the stud dog’s semen, reveals very poor semen quality.

It is seldom possible to establish the exact cause of poor semen quality. Some drugs are known to deleteriously affect semen parameters and should be avoided. Most drugs, though, will only have a temporary effect. Disease, endocrine (hormonal) conditions, and longstanding fever can also negatively affect semen parameters. In most cases, if the cause is reversible, it will take 6-8 weeks to return to normality, but up to 6 months if the cause is more serious. It is advised that the dog be rechecked before being put to stud again. In certain breeds, particularly giant breeds, poor semen parameters seem to be inherited. It is prudent to take note of this aberration and select against it, in cases where a genetic origin is either confirmed or strongly suspected. If breeders do not select against poor fertility they are likely to exacerbate the problem and become more reliant on veterinary assistance to improve results through the use of artificial reproductive techniques. Intervention by artificial means does not (per se) imply genetic deterioration of semen parameters. This is because many causes of poor semen quality have nothing to do with the genetic makeup of the dog.

Whatever the cause of poor semen quality, a dog should be thoroughly examined for genital (reproductive) soundness. It is not possible to certify a dog sub fertile or infertile based on an examination of a single sample. If the semen quality is good, a single collection is adequate for certification purposes, but if the semen quality is poor, it is recommended to repeat collection and evaluation on 2-3 occasions, a couple of days apart. Even then it is recommended that the dog be retested, and that semen is collected a month or two later to confirm previous poor results.

If it is categorically established that a stud dog has poor semen parameters, it is only fair that the owner of such a stud dog informs everyone who wishes to use the stud of the fact.

 Daily sperm output (DSO)

This discussion is important because it clarifies the impact of frequent matings on the stud dog’s sperm reserves and fertility. The daily sperm output refers to the number of potentially fertile sperm which can be produced by the testes each day. DSO is influenced by age, testicular size and individual variation; all probably predetermined by genetic factors. The DSO can only be established by taking the average daily sperm count over several days. The DSO is an accurate measurement of sperm production (spermatogenesis). Although most dogs aged 8 or older may have decreased DSO, there are exceptions to the rule and some studs of 11 years may still have excellent semen parameters. For small, medium and large breeds this number respectively on average is 290, 490 and  800 million sperm per dog per day.

It is important for breeders to understand that sperm is eventually evacuated from the testicles irrespective of whether ejaculation took place or not. Under normal circumstances, the fate of the old sperm is resorption within the testicles and passive transport into the urethra and the bladder. Therefore sperm which is not ejaculated is disposed of through resorption within the epididymis or transported to the bladder. There is a small sperm reserve that resides within the tail of the epididymis of the testis and this reserve is greatly reduced after a single ejaculation. This reserve is replenished within 24 hours.

The duration of sexual rest does not influence DSO but it might influence the sperm numbers and sperm quality in the ejaculate, on the day of collection. By resting (4-5 day) the sperm count may increase by about 25-30% for one day or so and thereafter the stud’s sperm count will be approximately equal to his DSO again. What this implies is that the normal stud has little to gain from sexual rest.  Many breeders may have heard of “old sperm” which may have accumulated after sexual rest (10 days or more). This refers to old and degenerate sperm which reside in the sperm reserve of the testis. A single ejaculation is usually sufficient to rid the stud of these old and degenerate sperm. It is important that this single ejaculation is  not less than 1 day and not more than 7 days before semen is collected for semen evaluation or for freezing purposes.

The practical implication is that the normal healthy stud with a normal DSO can mate daily for several weeks without deleterious effect on its semen parameters. It is however more likely that this frequent mating schedule will result in temporary lack of sexual interest. More than once a day matings is not harmful to the stud or his sperm producing tissues but will result in slightly lower sperm counts in the ejaculates from which the dog can recover in a few days, irrespective of how long the twice daily mating had continued. When using normal males of good fertility, twice a day mating is unlikely to adversely affect conception rates. This is in contrast to the notion by breeders that an “overworked stud” is likely to result in poor conception rates. When a stud is collected twice in short succession (1-2 hours), the second ejaculation will contain 70% of the sperm numbers attained in the first ejaculation. This is often practised to maximise sperm numbers when collecting semen for freezing purposes. Twice a day semen collection or matings should only be used under special circumstances and not as a routine. Besides reproductive repercussions there are also ethical concerns and allegations of exploitation when maintaining such extensive use of a stud.

In summary, healthy studs can comfortably mate daily for some weeks or every alternate day indefinitely without any deleterious effect to his sperm number, quality and fertility. This may however not be true for dogs which are not reproductively sound and have either poor semen quality or inadequate DSO or both.

Many registering authorities however, will not allow the registration of more than a finite number of litters for any one given male over any given 12 month period. Breeders should acquaint themselves with and abide with these regulations.

Confusing issues regarding poor fertility in stud

A very frustrating confusing issue with poor fertility of males is that it may go unnoticed for a period of time. This is because very few males are totally infertile. Most male fertility problems present as subfertility meaning they have poor fertility, owing to poor semen quality. Let me explain the cause of the confusion. If for instance, we look at a Labrador retriever male or Boerboel stud that is subfertile and the stud has been used in 10 bitches of known good fertility. The expected conception rate (percentage of bitches that become pregnant) using perfectly fertile studs should be around 80%, meaning 8 out of ten of the bitches should become pregnant and have normal average sized litters. However, if a subfertile stud is used on the same 10 bitches then (depending on the extent of subfertility) only 4 or so of them may conceive of which 1 pregnancy may have been a very big litter. What happens now is that because the stud was able to impregnate a single bitch with a large litter and three other bitches conceived, the owner of the stud is convinced that the stud is indeed perfectly normal and that the reason for the poor fertility in the other bitches must therefore be something related to them and not the stud. That is not true, studs with poor fertility will typically result in poor conception rates with the odd normal to large litter just to confuse matters. 

Incomplete semen evaluations may also mislead the owners of the stud. All too often a stud is presented to a veterinarian and semen is collected and immediately evaluated under a microscope slide and based on “ a lot of movement under the slide” the stud is considered normal. Meanwhile the semen numbers are vastly inadequate and there are a very large numbers of abnormal sperm present that are incapable of fertilizing eggs. In such cases all sorts of other causes of the poor conception rate experienced is sought in the bitches with no results.

Another confusion issue is the fact that semen quality can deteriorate over time and this is particularly common in the larger breeds. Although in some cases there may be a plausible explanation for the cause of subfertility e.g. very serious bout of tick fever or some infection that caused prolonged fever. In such cases the stud should be rested for 6-8 weeks and re-evaluated after rest. There are some supplements that may aid in this recovery. In many cases however there is no plausible explanation and the drop in fertility remains unexplained.

Some studs have a poor daily sperm output, meaning that they are not able to produce adequate numbers of sperm on subsequent days. Some studs are incapable of being collected if the intervals are too short (daily for a couple of days) and only prostatic fluid with little sperm is collected. This scenario is particularly worrisome if a breeder has a number of bitches that need to be bred to such stud.

Management of the subfertile stud

First and foremost, it is always advised that for genetic improvement of your stock, selection against subfertile studs is employed by replacing such studs with very fertile ones. If for whatever reason this is not possible, there are a number of option available.

Proper ovulation timing using vaginoscopy or progesterone may improve results using subfertile studs. When using frozen semen, the semen needs to be deposited in the uterus for optimal results mainly because of reduced semen motility, damaged sperm and reduced sperm numbers. For the same reasons semen from subfertile males may be deposited directly into the uterus and better results may be attained.

The breeder may consider using semen of good quality in the last 24 hrs before the bitch has entered dioestrus (end of season). This is commonly known as using a top-up male. The logic behind this is that if the semen of poorer quality did not impregnate the fertilizable eggs, then the semen of the “top-up” male might do so. In this case , the breeder should perform DNA parentage verification in order to register the litter to the correct sires.  Dual breeding to multiple sires helps reducing the percentage of bitches that do not conceive and also reduce the number of small litters.

More information about these matters can be obtained from our website and my book “Breeding is a bitch” . For further details go to http://www.rantendal.co.za.