Rabbit

Factors that prevent conception

There are many factors that influence conception rate. Sterility, extreme age, poor physical, pseudopregnancy, poor genetic quality, sore hocks, injuries, retained fetuses, and disease are among the most important factor. If she is too thin, you are probably underfeeding, or if she’s too fat, you’re overfeeding. Both conditions have negative effect on reproduction. Intensive breeding (on a 14-day or less remate schedule)can cause a doe to lose weight  and condition, thus reducing to conceive.

Sterility

 In its natural environment the wild rabbit breeds during the spring and early summer and is barren during the fall and winter. During this barren period the ovaries become somewhat shriveled and inactive, and fail to produce normal egg cells; buck may fail to produce sperm, or the sperm may lack motility or be abnormal in development. In developing the domestic rabbit, humans have shortened the barren period somewhat. Its duration an intensity very considerably. Some does and buck are fertile throughtout the year and  for successive years. Others will not conceive for extended periods. When  does are out of production for an extended time, it is  more difficult to get them to conceve; but if herd has received proper care, a large percent of both does and buck should be over the barren perid in a short time. In extreme cases, horever, the period may last four to fine months. Usually these prolonged periods occur in areas where excessive temperatures have prevailed, especially when unseasonably or excessively high temperatures occure or continue for some time, or when  the high temperatures are associated with drought conditions. Indications are that the sperm production of the buck more likely to be  impaired by these high temperatures than ovulation in the does, but both sexes can be affected.

Another cause for the prolonged sterile periods may be that the ration has no been properly balanced, or the proper may be that the wasn’t used to keep the rabbits in desired breeding condition while the animal in molting, the development of a new coat may tax its vitality, and conception may be delayed. Occasionally an animal is permanently inferlie and should be culled.

Because there is so much variation among does and buck in regard to the regularity of breeding, the rabbit breeder may well give considerable attention to overcoming this factor through proper selection of breeding stock. Breeding stockshould be selected from fparent that produce regularly. Attempts to increase production during the sterile period by the use of vitamins an other fee supplements have not een effective.

During the late autumn and early winter, when the percentage of does that conceive is below that of the spring and summer, the birth weight of the young may be below normal, litter may contain fewer individuals, and the does may neglect their young.

A decrease in conception in the winter may be caused by inadequate feeding. In the cold of winter in unheated rabbitries, the rabbit use more of their daily ration to produce heat to keep warm. Therefore, less energy is available for reproduction processes. To offset this increased body heat demand, the daily feed allotment to does should be increased by about 25-50% in the winter.

Another factor that may  influence seasonal fertility is the lighting program. In the wild, the rabbit is a seasonal breeders; this pattern is possibly regulated both by temperature and by light. During the fall, as day length decreases, a light-sensitive gland, the pineal gland, detect the decreases in light and decreases the secretion of certain reproductive hormones by the pituitary gland at the base of the rabbit’s brain. By maintaining a longer  day length in the rabbitry by using artificial light, you may be able to prevent the winter decline in reproduction. A lighting  period of 16 hours per day seems adequate in most regions; the length of the lighting period should be as long as the longest day in your region. This is the principle used in the poulty industry to keep bird laying in the winter. A great deal more research is needed to eclucidate the role of environmental factors such as temperature an light in controlling rabbit production.

Young does and buck may be sexually immature, while other does and buck may be too old, having passed their period of usefulness. The proper age for the animals to be put into production was discussed earlier, and they may be retained in the breeding herd as long as they maintain good physical condition and produce satisfactory litters. This may be until they are 2^1/2 to 3 year old. There is wide variation, and some individuals may reproduce satisfactorily for four years on more. However, in some cooercial herds, un to 100% of the does may be replaced in a year.

A  high culling rate may be desirable to continually upgrade the herd. If proper selection procedures are used, each doe that is culled can be replaced by a doe of higher genetic quality.

Physical condition

            Rabbits that are abnormally fat or thin will have impaired fertility or they may become sterile, and the ration should  be adjusted and breeding delayed until they are in the proper physical condition. For those that are too fat, a pelleted diet should be redtricted and a limited quantity of a good quality hay fed. For those that are too thin, the complete  pellets or a grain and ration should be fed in increased amounts.

Pseudoprenancy

           

            Pseudopregnancy can result from a sterile mating or from stimulation caused by one doe riding another, or by a doe riding the young in her own litter. This condition lasts for about 17 days. Dring this time the the doe may not conceive, so if the does have been kept in groups they should be separate and put into individual cages at least 18 days before being  mated. Pseudopregnancy is discusses further in Chapter 11

Sore hocks or injuries

            Sore hocks or injuries may affect the vitality of does and buck and should be corrected before the animals are mated. They should also be examined  carefully before being mated, and if any symptoms of disease are found yhe affected animals should be isolated and  held in quarantine until completely recovered, or culled from the herd. Because susceptibility to sore hocks is genetic, affected animals should be culled. Buck with sore hocks will refuse to breed, because the weight is shifted to the hind feet during mounting.

Retained fetus

            In rather rare instances, a doe may fail to deliver the entire litter, and the fluids of the retained fetuses will be resorbed and mummified fetuses produced which remain in the uterus, usually causing permanent infertility. These dases be be diagnosed accurately by palpation. Because these does will seldom conceive again, they should be culled from the herd.

DETERMINING PREGNANCY

            Test-mating does by returning them to thr buck’s cage to determine pregnancy is not a dependable practice. Some does will accept service again after they have conceived, and others will not accept service even though they have not conceived. Nothing the development of the abdominal regin and the gain in flesh by the doe as the period of gedtatin advances is not always accurate and will delay definite diagnosis until late in the period.

            Palpating or feeling the development of the young in the uterus with the thumb and forefinger is an accurate and quick method for determining pregnancy. To make this test, restrain the doe by hold ing the ears and a fold of skin over the shoulders in either the right or left hand, with tour free hand placed under the body slightly in front of the pelvis (Fig. 5-8). To make the test accurate, you must relax the doe so the abdominal muscles will not be tense. Generally, you can place the doe on top of the cag for palpation. If it is necessary to use a table or cart, cover the top with a feed sack or carpeting to prevent her from slipping.

            Tou must be acquainted with the relative size and location of the uterus an d the embryons as pregnancy advances. Fig. 5-9 shows the position of the uterus 9the digestive tract has been removed) and illusutares the size of the uterus of a on-pregnant doe (left) and that of a doe at the end of 10 days of pregnancy (right). It should be noted that the uterus has expanded to accommodate developing embryos; as the period of gestatin advances, the embryos grow larger and the uterus is pushed forward as shown in Fig. 5-10.

            There is little danger in palpating, provided at the proper stage of fetus developmwnt and the proper technique is followed, but you must use caution and not put too much pressure on the tissues, in order to prevent injury to the developing embryos. The test will be more accurate and there will be less danger of injury if the examination is made about of pregnancy the embryos are about the size of an olive and are distributed in the uterus as indicated in Fig 5-10 (left). Just enough pressure must be used with the thumb placed on one side enable the one doing the pappating to note the marbleshaped bodies or embryos by allowing the thumb and finger to slide over them gently. If the technique has been perfected, and no developing embryos are found, the doe should be returned to the buck’s cage for another service. She should be kept on the ration that is suitable in quantity and quality for dry does until she is known to have conceived or is culled.

            It would be well for the inexperienced to repalpate in a few days the does that were diagnosed ad non-pregnant. If a mistake was made at the fist handling and a doe is now found to be pregnant, she should be placed immediately on a management regime that is suitable for pregnan does.

            Later than the fourteenth day it is more difficult to distinguish between the developing young and the digestive organs when palpating (Fig. 5-10, right). After the technique has been developed, however, it is possible to determine pregnancy by the tenth day. In palpating earlier than 10 days following mating, the embryos are very small and you must make sure that pellet-shaped fecal material in the large intestine is not confusin by remembering that, with the animal in the proper position for palpating (Fig. 5-8), the uterus lies at the bottom of the abdominal cavity while the large intestine is above it, nearer the backbone of the animal.

            As one gains proficiency in the practice and becomes bette acquainted with the anatomy of the organs in the abdominal cavity, it is possible to identify retained fetus and the presence of abscesses or  cysts in the reproductive tract. When any of these conditions are detected, the does should be culled.

            It is a good idea to repalpate does at the time the nest box is added to the cage (usually 28-29 days after breeding). The reason for the second palpation is that occasionally does will conceive normally but later will resorb the embryos. If the fetuses die before day 19 of gestatin they are resorbed, whereas if they die after 19 days of gestation they are aborted.

            Palpation for pregnancy is a must for commercial rabbit raisers. The profit of the operation depends on the production of live litters on schedule. Palpation at 12 days of gestation saves 19-20 days of feed labor because if the doe is found to be non-pregnant she can be rebred immediately.

KINDLING

            The nest box should be p;aced in the cge 28-29 days after the doe has been bred. It should contain bedding or straw, shvings, or similar material. The doe will make a nest of straw or other materials (Fig 5-11), after which she pulls fur (Fig. 5-12) from the hiparea, the dewlap, and around the mammary glands, to complete the nest (Fig . 4-16). Care should be taken when inserting the nest box to ensure that it is not placed  where  water may drip in it from the waterer or in the doe’s latrine area. If the doe moves the box to a specific place in the cage, it should be left there.

            A doe will usually consume less fees than normal for two or three days before parturition, and a small amount of green feed each day may tempt her appetite and have a beneficial effect on the digestive system. She should be made as comfortable as possible and ters will be kindled during the night. Either the anterior or breech delivery if the fetuses are normal in size. Occasionally there may be only a few kits in the litter, and in these cases one or more may be abnormally large and kindling amy be delayed a day or two.

            As each kit is delivered the doe licks it and may nurse it immediately. When the entire litter is kindled, she pulls more fur from her body and covers the litter (Fig 5-12). A normal litter that is clean and has full stomachs and a comfortable nest has made a good strat in life.

If a doe has not kindled  by day 32 of preginancy, one method of getting a live litter is by injecting the hormone oxytocin to induce labor. Kindling usually occurs within 5 minutes after the intramuscular injection of 2 units of oxytocin ( 1unit for dwart breeds). If the doe has not built a nest, some fur can be taken from other nest boxes to make one. Does induced by oxytocin rarely kindle in the nest box, so the kits should be picked up as soon as they are born an placed ain the box. The doe will usually accept the litter.