Reproductive performance of female rabbit (Oryctolagus cuniculus) at the smallholder farmer in Karanganyar Regency, Central Java Province, Indonesia

The aims of this study was to find out the reproductive performance of female rabbits in small holder farmer in Karanganyar Regency, Central Java Province, Indonesia. This research was conducted in July-Desember 2022 in Colomadu, Gondangrejo, Kebakkramat, Karanganyar, Matesih, Jumantono, Jumapolo, Karangpandan, and Tawangmangu. The methode used in this research was a survey with a purposive sampling method. The number of respondents used was 30 New Zealand White rabbit farmers. Data collection was carried out through interviews and observation. Research parameters used in reproduction were the age of first birth, gestation period, litter size, kitten interval, and service per conception (S/C). The results showed that average age of first bith, gestation lenght, litter size, kindling interval, service per conception (S/C) were 6.1±0.8 month, 30±0.7 days, 6.0±1.0 kits, 75.8±9.9 days, 1.6±0.7 times. It can be concluded that the reproductive performance of female rabbit in Karanganyar Regency were classified as in a good condition and have a potential to be developed in the future.


Introduction
Rabbit (Oryctolagus cuniculus) is a type of pseudo ruminant livestock, herbivores that cannot digest fiber properly and fermentation occurs in the caecum, which is part of the large intestine 1.Rabbits have the advantage of being able to give birth 4-6 times a year and at each birth they are able to produce 6-10 kitten 2.Furthermore, rabbit meat also has the advantage of having a relatively high nutritional content compared to chicken and beef 3.
The population of rabbits in Karanganyar Regency in 2017 was 12,465 heads 4.Five years later, data on the population of rabbits in Karanganyar Regency increased by 13,772 (Department of Fisheries and Livestock of Karanganyar Regency, 2022, unpublished data).The data shows that in the last 5 years, the rabbit population has increased by 9%.The increase in population indicates that people are increasingly aware that rabbit farming has the potential to be developed.This is because Karanganyar Regency has the potential for culinary tourism which serves many kinds of processed rabbit meat, such as in the Tawangmangu and Karangpandan areas.
The development of rabbit farms must be balanced with good maintenance management, especially reproduction management.Faradila et al. 5 stated that reproduction has an important role in increasing the rabbit population through a high level of productivity.Efforts to increase the rabbit population can be done by knowing the efficiency of reproductive performance.The efficiency of reproductive performance can be observed through the age at first mating, gestational age, litter size, spacing of children and service per conception (S/C).The reproductive performance of female rabbits in various regions has different variations.The age at first mating of female rabbits varies between 6-7.8 months

Sampling methods
The method of determining the sample used in this study is purposive sampling.The criteria used in this study were that breeders were willing to be respondents, had a minimum number of five does that had given birth at least twice, and had at least one year of farming experience.The purpose of selecting these criteria is to make it easier to collect data and to find out the variables observed from the reproductive performance of rabbits, mainly the frequency and kitten interval.The population of rabbits per subdistrict in Karanganyar Regency in 2020-2021 can be seen in Table 1.Data on the number of breeders as the samples can be seen in Table 2.

Data collection
Data collection was carried out through interviews and observation.Interviews were conducted by conducting question and answer directly to respondents or rabbit breeders using a prepared 3 questionnaire.Observations were made by direct observation accompanied by recording of information related to the observed variables, namely age at first mating, length of gestation, litter size, spacing of children, and service per conception (S/C).
The data obtained from this study will be processed or analyzed with the help of the Microsoft Excel application and conclusions will be obtained in the form of averages and standard deviations and then analyzed descriptively.

Result and discussion
The characteristics of rabbit breeders in Karanganyar Regency in 2022 can be seen in Table 3.

Rabbit breeders characteristic
Breeders who make rabbit farming as their main job are as much as 10% and the remain as part-time businesses.Rabbit breeders in the study area generally work as entrepreneurs, civil servants, farmers, parking attendants and laborers.The average doe population is 11 heads with the highest population being 50 heads and the lowest being 5 heads.This shows that the rabbit farms in the study area are classified as small-scale, so they are used as a part-time business.10 stated that rabbit farming which is used as a part-time business is usually a small-scale business with 5-25 doe owners.Rabbit farming on a small scale will not interfere with the main work.If the population is more than 50 doe, it will usually be the main job because it requires more attention, effort and time.A 93% of rabbit breeders in Karanganyar Regency are of productive age with an average final education of 47% high school and 80% having farming experience more than 2 years.Farmers in the study locations who are of productive age, have a history of higher education, and have long-standing farming experience tend to have good planning in running their livestock business.This is in accordance with the opinion of 11 that breeders who are highly educated and have long-standing farming experience will be able to run their livestock business well because they have social interaction skills.
Rabbit breeders in Karanganyar Regency who have the aim of raising for breeding are 7%, fattening are 16% and combining the two are 77%.Rabbit breeders in research locations are usually used for contest rabbits.Common rabbit breeds used for contests are New Zealand Red, New Zealand Blue, Flamish Giant, English Spot, Rex, and Netherland Dwarf.Meanwhile, meat rabbits such as New Zealand White, Rex, Hyla, and Bligon will usually be sold when they reach a minimum weight of 2 kg at a price of IDR 35,000.00-40,000.00/kg.Generally, rabbit breeders in the research location choose to sell readyto-slice rabbits and also seeds so that they can reap more profits.12 stated that the purpose of maintenance is divided into two, namely meat rabbits which are cultivated specifically for meat consumption and ornamental rabbits which are sold in the form of broodstock or pets.
Based on the description of the paragraph above, it can be seen that the breeder's characteristics affect the reproductive performance of rabbits.Breeders with productive age, highly educated, and long enough experience will tend to be able to carry out good maintenance management, one of which is reproductive management.This is supported by the ease of accessing information, experience, and relationships, making it easier for breeders to understand and deal with existing problems, especially in improving reproductive performance in their rabbits.

Doe's reproduction performance
The reproductive performance of female NZW rabbits in Karanganyar Regency in 2022 is presented in Table 4. 1.6±0.7

Age at first mating
Age at first mating is the right age for rabbits to have their first mating.The first mating age of female NZW rabbits in Karanganyar Regency was 6.1±0.8 months.This age is included in the normal range, namely 5.5-6.5 months 1.The data obtained is also in accordance with the results of research by 5 in Blitar which was 6-7 months.However, the first mating age of female NZW rabbits in Karanganyar Regency was relatively quicker than in Magelang, which was 7.85 months 6.Usually, breeders mate rabbits for the first time by looking at their age which can be calculated from the rabbit's birth date.
Birth data recording or recording by breeders is done by recording it in books, calendars, boards in cages, and recording cards.Parameters that can be used as indicators of rabbits ready for mating include body weight, age at first mating, and estrus.Rabbits will be ready to mate with a minimum weight of 2.5 kg.Sexual maturity and body maturity in female rabbits are when they are 5.5-6.5 months old.Signs of estrus can also be used as an indicator for rabbits ready to mate.Rabbits that are in estrus have the characteristics such as trying to join the nearest cage with a male, wet vulva, and reddish color.

Length of gestation
The gestation length for rabbits is the time it takes for rabbits to mate until they give birth 15.Based on the data obtained, the gestation period for NZW rabbits in Karanganyar Regency was 30.0 ± 0.7 days.The duration of gestation is within the normal range, 29-33 days.The data obtained is also in accordance with previous studies in Magelang and Surakarta that the duration of gestation for NZW rabbits is around 29-31 6,16.
The age of the young mother usually causes the gestation period to be shorter because this is the first time the doe gives birth, so the possibility of the doe experiencing stress will be high.Adequate feeding and according to needs also affects the duration of pregnancy.The doe rabbit will not be able to maintain her body condition if there is a lack of feed, which can cause embryo death and eventually, the gestation period will be longer.Furthermore, the length of gestation in rabbits also depends on the number of kits born.The duration of gestation is longer if the number of children born is small and weighs more than 100 grams.On the other hand the large number of children makes the gestation period shorter.The large number of kits causes the stimulation of birth hormones caused by the movement of the kits.This condition causes the parent to become stressed due to increased cortisol hormone.Stressed mother rabbits cause an increase in the hormone estrogen and a decrease in the hormone progesterone so that birth occurs.

Litter size
Litter size is the number of kits born from a doe.The average litter size of NZW rabbits in Karanganyar Regency was 6.0 ± 1.0 (Figure 2).The litter size of rabbits at the study site was within the normal range, 6-12 rabbits/birth.The data obtained is also in accordance with the results of research by 7 in Blitar, 5-6 individuals.However, the litter size of rabbits in Karanganyar Regency was lower than that reported by 17 that the litter size of rabbits is 7.1-8.2kits.
The litter size of NZW rabbits in Karanganyar Regency is normal but still relatively small and has the opportunity to be increased.The litter size of the rabbits at the study site was influenced by the NZW rabbit breed, which were not all pure, the physiological conditions of the does were not the same, the feed, and the age at first mating were different.The purity of the rabbit breed will affect the number of kits born.Good physiological condition of doe, body and genitals have entered mature age also affects litter size.The feed given also affects the number of kits born.The feed given must be in accordance with the nutritional needs of the doe so that it can reduce abortion or mortality.

Kitten intervals
The kitten interval of NZW rabbits in Karanganyar Regency obtained an average of 75.8 ± 9.9 days.The data obtained is in accordance with the results of studies in Magelang, Jakarta, and Batu with a kitten interval of 60-90 days 6,8,9.
Rabbit breeders in Karanganyar Regency chose to re-breed NZW doe when the kits had entered the weaning period, at the age of 45 days.The goal is that the parent is in a condition ready to be mated and re-pregnant.In addition, breeders also regulate the kitten interval so that they remain in ideal conditions, 75 days so that in one year rabbits can give birth 4-5 times.Factors that influence variations in kitten interval in rabbits are breeders' expertise in detecting estrus, planned mating arrangements, and supported by good quality feed.The longer the breeder breeds the rabbits after giving birth, the slower the production will be.In addition, rabbits that are given good quality feed will affect the success of the mating program.

Service per Conception (S/C)
Service per conception (S/C) is a number that indicates the number of mating to produce a pregnancy 5.The S/C rate for NZW rabbits in Karanganyar Regency is 1.6 ± 0.7 times, which means that in general with 1 to 2 matings, the mother rabbit can be sure to be pregnant.The data obtained also corresponds to the S/C numbers for NZW rabbits in Blitar, with 1-2 matings, it is certain that the rabbits are pregnant 5.The ideal S/C value is 1 with good management ranging from 1.3-1.6 times and is said to be bad if ≥ 2 times.It was further explained that the lower the S/C value, the higher the fertility.The S/C value in rabbits is influenced by several factors including the ability of breeders to detect the time of estrus and the time of mating 7.
The mating process is usually carried out at night or in the morning.The female rabbit is put into the male cage so that the natural mating process occurs.The reason is that at night or in the morning the environmental conditions are cool so the rabbits don't experience stress.This statement is in accordance with the opinion of 7 female rabbits that are in estrus are put into male cages to be mated.The mating process is carried out naturally at night or in the morning.High environmental temperatures can cause stress to the mother so that it can affect reproductive performance, especially estrus and decrease egg cell quality 7,18.The advantage of using a natural mating system is that breeders can determine the quality of the sires and males used.In addition, the success rate of pregnancy in natural marriages is higher than in artificial marriages 16.

Conclusion
The conclusion this study was that the reproductive performance of female rabbits in Karanganyar Regency which included age at first mating, length of gestation, litter size, spacing of litters, service per conception (S/C) and were within the standard range.
Suggestions that can be conveyed in this study are that breeders must pay attention in detecting heat and mating rabbits so that the value of service per conception (S/C) is getting smaller and the pregnancy rate is high.Breeders must also pay attention to the age of first mating and the purity of the New Zealand White rabbit so that the litter size increases.Further research on the reproductive performance of rabbits from other breeds such as Rex and Hyla also needs to be studied.

Table 2 .
Data on the number of breeders samples

Table 3 .
Characteristics of rabbit breeders in Karanganyar Regency in 2022

Table 4 .
Reproductive performance of female NZW rabbits in Karanganyar