by Skip Godfrey
Most breeding problems in Hollands can usually be attributed to three factors: environment, diet, or health. In attempting to isolate the possible causes of breeding problems in ones herd let us look at each one of these factors in detail.
The first factor we will need to consider is environment, and the one thing in a Holland's environment that will have the most pronounced effect upon the production of the doe is light, or lack of it. In order for a Holland Lop doe to be receptive, the doe must be exposed to at least 16 hours of light per day. The reason for this is that in the wild, the rabbit is a seasonal breeder. This seasonal receptivity is governed by both light, and to a certain extent temperature. The pineal gland at the base of the rabbit's brain is sensitive to light and when it detects a shortening of the day-length it decreases the secretion of certain reproductive hormones. If you are housing your Hollands indoors and expect to breed them throughout the year, then you should provide them with artificial lighting that is at least sixteen hours in duration per day, or the same length as the longest day of the year in your area.
I personally feel that not only is the quantity of light important, but also the quality. Research is now showing that the narrow spectrum of light that is produced by both incandescent as well as the regular (cool white) fluorescent lights is having certain adverse effects on the well being of humans and animals. To circumvent these problems, certain manufacturers of artificial lighting have attempted to create a source of light that simulates the wide spectrum of light found in sunlight. One such product is the Vita-Lite fluorescent light by Duro-Test. I can highly recommend the Vita-Lite fluorescent lights as I have used them in my rabbitry for nearly four years, and they have proven their value in enhancing the reproductive capabilities of my Hollands as well as in helping to eliminate both airborne and surface bacteria.
The Vita-Lite is as close an approximation of natural sunlight as modern science is able to provide. These lights not only produce ultraviolet light to kill bacteria, but they also induce the production of Vitamin D in both humans and animals, hence the name Vita-Lite. In areas of your rabbitry where you can only use incandescent lights, you might try the new Daylight-Blue light bulbs which also simulate the full spectrum of light produced by the sun. Since a four foot Vita-Lite tube costs upwards of $15 and a Daylight-Blue bulb costs nearly $5, many rabbit breeders may consider the cost of installing such lighting to be prohibitive. I am well aware of the value of excellent lighting in the reproduction of animals, and I know that the extra Hollands I produce as a result of this lighting more than compensates for the cost of their installation.
Further attempts at simulating the natural environment of your does and increasing their production may be made with the installation of negative ion generators. I have been using these in my rabbitry for over two years and find that they increase production and also keep the environment free from airborne pollutants; I recommend these highly. Negative ion generators work by generating negatively charged ions which are released into the air and attach themselves to dust particles, ammonia molecules, airborne bacteria, and other pollutants and cause them to fall to the floor or be attracted to any object that maintains a ground potential. Research is now showing that negative ions in the environment not only contribute to one's health and well being, but that they improve immunity, health, and overall production in animals. More and more modern animal production facilities are installing negative ion generators in their buildings.
These devices are also relatively expensive. The ion probes that are advertised in Domestic Rabbits magazine cost approximately $50 each, and again many rabbit breeders may find this prohibitive. In my opinion they are worth every penny. The more you install, the cleaner the air.
The second factor that can cause severe production problems in Holland does is improper and/or inadequate diet. I know that many Holland Lop breeders restrict the diets of their Hollands. If you over-restrict a doe in attempts to keep her weight within show limits, then you may be denying her the very nutrition she needs to conceive, gestate, lactate, and still maintain her own metabolism.
Conversely, overfeeding a Holland can cause accumulations of fat to develop around the ovaries which can also prevent conception. If you are feeding a high calorie pellet, this is even more conducive to fat buildup. The best way to prevent this problem from happening is that once a doe is in production--keep her in production. Try to get at least two or three litters from her each year. If a doe remains idle for six months to a year, she may never conceive again.
Many times breeding problems can be caused by the lack of certain vitamins in the diet of the doe. Although these vitamins may originally have been incorporated into the rabbit pellets by the manufacturer, certain vitamins tend to deteriorate as a result of the manufacturing process due to the heat employed in pelleting. Also, most vitamins will deteriorate with age, and who knows how long the pellets have been lying around in the warehouse before being delivered. It is, therefore, a good idea to supplement your Hollands with the addition of vitamins in their drinking water. Another dietary supplement for rabbits is produced by the Vita-Stress company that advertises in Domestic Rabbits. This manufacturer claims that their product will help most problem does to conceive. Vita-Stress is a pelleted vitamin and mineral supplement that is fed by adding several of these pellets to the rabbit's diet on a daily basis. If you have a valuable doe that will not conceive, it may be worth giving this product a try.
The third factor that can affect production i n the Holland is health. There are two organisms that are the primary cause of problems involving the entire herd. One of these organisms is a "spiroformis" that has recently been isolated by the Chief of Pathology at Purdue University. This entity has been causing reproductive problems in rabbits throughout the United States. Not too much is known about this disease which is neither a bacterium nor a virus, but is what is known as mycoplasma. One thing for sure, it is difficult to kill, and at the present time, all you can do is wait until your rabbits can develop a certain amount of immunity to its effects.
From my experience with this entity, it seems that it affects the digestive system of a rabbit inhibiting the animal from extracting sufficient amounts of energy from its diet to be able to reproduce and still maintain its own metabolism. Since there is no cure at this time, the only solution is to increase the energy level of the feed to compensate for the action of this "spiroformis". Therefore, you may find that the same rabbit pellets that worked well for you in the past may now be too low in energy to enable your does to produce, the "spiroformis" organism does not kill rabbits, it merely weakens them.
Another organism that will affect production is a mold that can be found in hay from time to time and can even get into your rabbit pellets. This is an estrogen producing mold, and estrogen, as you may know, is a female hormone that is secreted by the doe. The ingesting of the estrogen producing mold by the doe will throw the hormonal system of the rabbit out of balance causing problems with reproduction.
Fortunately, a teaspoon of apple cider vinegar per gallon of drinking water will neutralize the effects of this mold. Since apple cider vinegar is purported to also have other beneficial effects on the rabbit, I make a practice of adding a whole tablespoon of this vinegar to each gallon of water I prepare for my Hollands. You never know when you will get a dose of this mold in your feed, so why take a chance?
Other organisms which can cause severe reproduction problems in Hollands are parasites such as coccidiosis and worms. Severe infections of these parasites can be devastating to production because a parasitized doe is a weakened doe, and as such may not be able to conceive or carry her young to term.
If your does are emaciated and you can feel the vertebra of their spines when you rub your hand over their backs, you may want to consider taking some stool samples to your veterinarian. If you do have these parasites, a good drug treatment program along with strict attention to cage sanitation will get rid of them in a hurry.
Sometimes a doe can have a retained fetus which will prevent pregnancy. A retained fetus in rabbit prevents pregnancy much in the same way that an IUD works in humans. Not much can be done for this so the doe should be culled from the herd.
Up to this point our discussion has been limited to the doe. However, it is important to realize that there can also be problems with a buck. Many bucks will become sterile in the summer as a result of being exposed to temperatures above 85 degrees. This is not a permanent condition, but it can put your buck out of commission for a couple of months.
Most Holland bucks do not produce sperm until they are at least six months of age. Bucks under this age may breed the does like crazy, but they are still sterile.
Sometimes a buck over 2 years of age will also become sterile for no reason at all. They will usually "come back" but it can be frustrating to breed ones old herd buck into all of the does only to wait for 31 days and have nothing.
If you own or have access to a clinical microscope, it is easy to check sperm. Simply let the buck breed a doe, and then take a vaginal smear with a cover slip. Place the cover slip on a slide and view the sperm at a magnification of 400. If you see many sperm moving at a high rate of speed, you have a fertile buck. If you have only a limited number of sperm that move very lowly, chances are the buck is close to being sterile.
Holland Lops can be very productive animals so long as you provide them with a clean environment, furnish them with a proper diet, avoid extremes in temperature, keep them free from parasites and disease, and breed does to bucks that you know are fertile.
HLRSC Official Guidebook - 5th Edition 2002