being overweight.
Age to Breed
Individual rabbits vary somewhat in the rapidity with which they develop, so both development and age must be taken into consideration in determining the proper time to start them in production. Sexually, the smaller breeds mature much earlier than the heavier breeds. The small Polish usually are ready to start production at 4 months of age, the medium weight New Zealand, Californian, etc., at 4½ to 5½ months, and the heavy Flemish at 6 to 7 months.
For best results, junior bucks and does should be fed in such a manner that they will make normal growth, develop strong, healthy bodies, and be firm in flesh when they are to be mated for the first time, without being excessively fat. Bucks should be put into service about a month later than does, as they are slower to mature sexually.
A method of determining sexual maturity in does is to examine the vulva. Does that are ready to breed, regardless of age, are those that have a moist, swollen, reddish-pink vulva. Does that show this condition will readily accept the buck when placed in his cage. When does are not ready to mate, the vulva is small and whitish in color with very little moisture observed.
Breeding Schedule
For production of show rabbits, it may be advisable not to attempt to produce more than two or three litters a year, with the time of matings arranged so that the offspring will be of the proper age and development for the desired show classification.
For commercial meat rabbit production, the objective should be to produce and raise as many marketable fryers per doe per year as possible. It takes about 35 offspring per doe per year to meet expenses, or the equivalent of about five litters per year. Fryers may be kept with the doe until marketing at eight weeks, but the trend now is for earlier weaning and earlier breed-back, to attempt to increase productivity. Many producers now breed back at 14 or 21 days. In intensive production systems, does may even be bred within 24 hours of kindling. It is remarkable that does will rebreed immediately after giving birth; in fact, their receptivity is very good at that time. Under post-partum breeding systems, litters must be weaned at 28 days, so the does can be given nest boxes in preparation for kindling three days later. No other type of livestock has such a potential for high reproductibility as the rabbit. However, this system may increase the percentage of does that are culled annually. Intensive breeding increases nutritional requirements, so a high quality feed is needed. Intensive breeding is not recommended for new rabbit raisers. Probably a 35- or 42-day breed-back should be first selected, and if satisfactory results are obtained, it can be shortened to a period that suits the producer and his or her management skills. With early breed-back, more cages are needed than when does and litters are kept together until marketing of the fryers. This increase in caging costs may be more than compensated for by increased production. Research studies on the “best” weaning age have given mixed results. Work at Oregon State University suggested that highest profits were obtained when all cages were filled with producing does rebred 42 days after kindling. Kits were left with the does until market age; therefore, no cages were used for finishing fryers. Other studies have shown that greatest profits were obtained when does were rebred 14 days after kindling.
Various breed-back schedules, such as 7, 14, 21, 28, 35, and 42 days, are used. Generally, does are on a seven-day schedule basis, simply for ease of recordkeeping. A system that may produce greater profits and longevity of the does is to breed “depending on condition,” taking into account the number of offspring in a litter and the condition of the doe. If a doe has a small litter (less than four for medium breeds), she might be bred back in seven days if she is in good condition. However, if she has a big litter, is milking heavily, and is beginning to lose flesh, she should not be bred back until the young are weaned. It is generally agreed that breeding back at 21 or 28 days results in reduced conception.
One of the best methods to judge the body condition of a doe is to use the sense of touch. It is difficult to tell the body condition of a doe by visual examination because of the fur. Put your hands on the doe’s back and feel the back-bone and the hipbones. If these bones are prominent, the doe is in poor condition. If she is bred in this condition, she might conceive, but the next litter may be born weak or small in number or weight, or she may abort or resorb the litter. The best thing to do if the doe is in poor condition is to delay breeding until her condition improves. In commercial herds it may be best to cull the doe.
The opposite problem can occur with junior does, which can very easily become overweight, especially if they are on full feed. If they become fat (again, you can tell by feeling the body with your hands), they will not breed. They should be put on restricted feed until they reach normal condition. This can take several weeks to several months. It may be more economical to cull fat junior does and replace them with does in proper condition.
The Mating Process
The doe gives evidence of being receptive by behaving restlessly; by rubbing the chin (chinning) on the cage, water crock, feed troughs, etc.; and by making an effort to join other rabbits in nearby cages. The appearance of the vulva, whether it is pale or reddish in color, is generally indicative of the receptivity of the doe. A doe with a dry, pale vulva is less likely to be receptive than one with a pinkish-red, moist vulva.
The doe may object to another rabbit being placed in her cage and quite often will attack and even injure the intruder, so she should always be taken to the buck’s cage for mating. If the doe is ready for service and the buck is active, mating should occur almost immediately (Fig. 5.3). When it is completed the buck usually falls over on his side (Fig. 5.4). The buck’s ejaculation occasionally misses the vagina. If there is evidence of this, the doe should be bred again before being returned to her cage. Studies have shown that allowing the buck to breed the doe two or three times when first placed in the buck’s cage will increase the conception rate and perhaps the litter size. This may be due to the additional stimulation causing a stronger ovulatory response.
Fig. 5.3. An example of natural mating. (Courtesy of D.J. Harris)
Fig. 5.4. When mating is completed, the buck usually falls over on his side. (Courtesy of J.I. McNitt)
Sometimes a doe will squat in the corner of the cage and will not accept service; in this case, restraining her for mating may expedite and ensure service. This procedure makes many matings possible that would not occur otherwise. Restraining her, however, does not necessarily mean she will conceive. The conception rate from forced mating is much lower than from unrestrained mating.
Figure 5.5 shows the proper method for restraining the doe. Either the right or left hand is used to hold a fold of skin over the doe’s shoulders; the other hand is placed under her body and between her hind legs. The thumb is placed on one side of the vulva, the index finger on the other, and the skin is pushed gently backward while avoiding any pinching of the vagina. This procedure throws her tail up and over her back. The weight of the doe’s body is supported by the hand, and the rear quarters are elevated, but only to the normal height for mating. Bucks accustomed to being handled will not object to this assistance by the attendant, and many does will respond and
