Selection of Breeding Stock
The selection of breeding buck and doe is very much important aspect of breeding since good progeny is expected from good buck and doe. One has to consider the breeding stock in terms of fertility, maternal instinct, milk yield, growth rate, fecundity and viability.
The male rabbit is known as buck. A buck develops its breeding capabilities at the age of 8 months. An ideal buck should continue to maintain its reproductive ability at least for 2 to 3 years. A young buck may be allowed to mate one doe at an interval of 3 to 4 days. But, from 12 months of age onwards it may mate 4-6 does in 7 days. A buck beyond 6 years of age should be culled since semen quality declines. In order to keep the buck healthy additional protein, vitamin and minerals are to be supplemented in diet. Two breeding bucks should not be kept in same place as they will fight each other and cause injury.
The female rabbit is known as doe. A doe should have the perfectability to reproduce. A doe becomes capable to reproduce based on breed,nutritional status and seasons. The smaller breeds attain sexual maturity earlier than larger breeds. A small breed may accept mating at 3-4 monthsof age whereas the larger breed may accept mating at 8-9 months of age.A doe can be used for breeding up to the age of 3 years and culling shouldbe made afterwards.
The rabbit belongs to a group of mammals which do not ovulate spontaneously. There is no oestrus cycle. Ovulation requires stimulus of mating and thus induced in nature. Sexual stimulation with copulation or in response to exogenous, gonadotropins, ovulation takes place. Sometime females may stimulate each other to the point of stimulation. This type of ovulation is expected in does becoming pseudo pregnant or sterile for few days. Ovulation is apt to occur within the range of 9-13 hours. But, generally it takes place at 10 hours following mating.It is thought that does may remain in constant heat throughout the year or in breeding season. But, it is known that follicles develop and regress in cycles of 15-16 days. There is a lack period when the doe may loose interest for the buck. Ovulation can also be induced through mechanical stimulation of vagina.
A doe whether is in heat condition or not is difficult to recognize outwardly. But, does may show some manifestations like restlessness, nervousness, rubbing of head and chin on the side of the cage or other objects. The vulva becomes swollen and purple in colour. But, acceptability of the does to the bucks or does reaction to bucks should be taken as a criteria for heat. Therefore, detection of heat through buck should be made before allowing for copulation.
The approximate age of first mating is around 5-6 months of age. As a rule doe should be taken to the cage of buck but never be done vice versa to avoid fighting. Early morning and early evening are the most conducive time for mating. A receptive doe will lift her tail and allow mating. Males vary greatly in their sexual drive. A buck may be slow in performing the service to a strange cage. If a buck is virile and doe in perfect heat, mating will occur almost immediately. After successful mating the buck usually produces a typical cry and falls down to one side of the doe. One mating is usually sufficient. If a female does not allow in that case keeper should wait for 3 to 4 days or assist in mating holding the female. After mating the doe should be returned to her cage.
In a commercial rabbit farmers would like to have five or six litters per doe per year. This is possible only by weaning the litter at five weeks of age and mating the doe immediately following weaning. Each breeding cycle will take 65 to 75 days. This can also be achieved by mating the doe 21 days after kindling.
The gestation (pregnancy) period in rabbit ranges from 28-32 days (approximately 30 days). The nest box is to be kept within the cage to facilitate the doe for preparing bedding for the new born. The nest is to be provided at least 5-6 days before parturition. The nest box should contain nesting materials like straw, grass, wood savings etc. Saw dust should not be used as bedding material. A doe may pullout some of her own hairs to make nest for litters. Adequate measures should be taken concerning feeding and management during pregnancy period. Quantity of feed should be increased for 10 to 15 days of pregnancy. Plenty of fresh water should be provided.Environmental stresses should be avoided as far as possible.
Pregnancy can be detected by various methods:
(a)Through palpation of abdomen by which embryos can be felt by hand. This is best done at about two weeks after mating. This technique can be perfectly done through experience.
(b)Placing the buck near the doe for mating. A buck may not mate the pregnant one.
(c)Uterine swelling-uterus may swell up to 12 mm at 9 days after mating. It may reach 20 mm at 13 days. Only experienced keeper may be able to predict the changes accurately.
(d) Changes in body weight-There are significant change in body weight from mating up to 30 days. Average gain of around 300-400 gm has been suggested from mating to 30 days in large sized rabbit.
(d) Kindling (Parturition)
Process of giving birth of new baby of rabbit is known as kindling. It is a natural physiological phenomenon. The parturition very often takes place at late night or early morning. It may not require any interference by the keeper. The process usually completes within 7-30 minutes. Sometime all the litters may not be born on succession. Some may born after several hours or a day. The pregnancy may required to be terminated through injection of oxytocin. Following parturition the does used to lick the young and may eat the placenta. The baby rabbits will try to suckle the mother. If the number of litter is eight, all may be able to suckle since doe has eight teats. The baby rabbits those will be unable to suckle may turn weak and susceptible to diseases. Many of them may even die prematurely. The does should not be disturbed during this time and be fed ad lilbitum. Adequate food and water should be provided so that optimum amount of milk is available to the baby rabbits. Rabbit used to nurse her young usually at night or early morning only for once. 6-12 baby kids may be barn from a single kindling.
Immediately following birth baby rabbits are solely dependent on their mother. They are born naked. But at about 7 days, there is growth of hair and vitality of them. The eyes used to open after 10 days. The baby rabbits can lead their lives without mothers' milk at about 21 days of age. The young should be removed from their mother not before 4th week. The doe should be removed from the cage. Foods like concentrates and grasses should be provided. The baby rabbits can chew and eat after 3 weeks of age. The does can be rebred provided the physical conditions of them are satisfactory in nature after one week of kindling.
(f) Identification of Sex (Sexing)
Sexing is done at the time of weaning. The baby rabbit has to be placed on the hand and by the pressure of thumb and forefinger the sex organ is to be pushed on either side. In case of buck the penis will come out as a protruded mass having rounded tip. But, a slit will be located in case of Doe.
(Source: Namakkal KVK, Rabbit Farming)
Stage-wise description of reproductive stages in rabbit
|Breeding males required
||1 male for 10 females
|Age at which first bred
||Small breeds - 4 months age (Polish, Dutch)
Medium breed - 5 to 6 months (Newzealand White, Chinchilla)
|Characteristics of reproduction
||Polyoestrous. A female rabbit appears to have no definite oestrus cycle although a certain rhythm exists in their sexual receptivity. Cycle lasts for about 12 days of which 4 are infertile.
|Signs of heat
||Congested, purple and moist vulva, restlessness, rubbing the chin on the sides of the cage, lying in mating posture and lifting the tail
||The doe is always taken to the buck’s cage for mating, and if the doe is in full sexual receptivity it will lift the tail and
within a minute the buck will be mating the doe. Mating is
successful when the buck falls to one side or backwards
||Ovulation occurs 10 - 13 hours after copulation – reflex
||Pseudo pregnancy in rabbit may result from sterile copulation and lasts for 16 to 17 days. At the end of this period she may pull hair from her body and attempt to make nest and shows development of uterus and mammary gland.
||28 -34 days (average 31 days)
||The methods adopted to determine the state of pregnancy
are test mating, weight gain method and the ‘palpation
technique’. The palpation technique is the most reliable
method if done by an experienced person.
||A completely relaxed doe should be placed on a table which has been covered in sacking to prevent her from slipping.
The doe should be restrained by gently holding the fold of
skin behind ears and over the shoulders. The left hand is
placed under the body between the hind legs and in front of the pelvis. The uterine horns are felt gently using fingers and thumb. The thumb is placed to right of horns. Embryos can be located and felt like small marble shaped bodies slipping backwards between thumb and fingers when moved gently in a sideways direction. An experienced person can deter-mine pregnancy by 8th to 10th day of mating using this technique. During last week of pregnancy a nest box lined with wood shaving or hay or coir fibre should be placed inside the cage.
||2 months (it may be as short as one month if bred immediately following kindling)
(Source: www.vuatkerala.org )