Black-bone goat : An investigation report on new genetic resource of farm animal

Black-bone goat is a unique local population recently discovered in Tongshan, Hubei province, China. Its geographical distribution, natural environment and ecological conditions were investigated. The Black-bone goat is mainly distributed in the mountainous area of Tongshan County. Using random sampling, its body shape and appearances, size and weight, reproductive performance and carcass characteristics were examined. The birth weight at 3, 6, 12 and 36 months of age for males were 1.83, 9.50, 14.01, 24.25 and 37.88 kg while those of females were 1.60, 8.75, 13.78, 23.53 and 34.19 kg, respectively. The live weight, dressed weight, dressing percentage, meat weight and meat percentage at 12 months was 22.32 kg, 10.95 kg, 49.02%, 8.01 kg and 35.42%, respectively. The litter size is 1.85. Based on historical materials including literature and folklore, the origin and medical applications of the Black-bone goat were analyzed. Finally, suggestions on preservation were proposed.


INTRODUCTION
There are 22 breeds of goats listed in Sheep and Goat Breeds in China (Zheng, 1989), but these are less than half of the total goat breeds in China.There are 31 provinces and autonomous regions in China, and each province has its own "Livestock and Poultry Breeds".There are 43 goat breeds listed in this kind of authority books (listed at URL: http://cars.hzau.edu.cn/sheep/index.php?option=com_content&task=view&id=97 0&Itemid=38).
A new goat breed (Dazu Black Goat) was recorded in "National Livestock and Poultry Genetic Resources" in 2009 (http://baike.baidu.com/view/1672655.htm).The majority of the goats are kept by smallholder farmers in the South of China and they are primarily used for meat production.Many indigenous goats of the middle and lower Yangtze River valley have not been officially classified into breeds (Jiang et al., 2003).
Black-bone goat is a unique local population recently identified in Tongshan County, Hubei Province.It is a very distinct native animal because of its black pigmentation, which makes many of its tissues, such as skin, bone and liver look black.According to our research, this is the only goat population in the world with "black bone".Chinese people have a very long history of preference for "black food" in their culture, so this kind of goat provokes a lot of interest.Here we investigated its distribution, measured its body weight, body size, reproductive performances and carcass characteristics, and then analyzed its origin and medical applications.

On-the-farm investigation
According to the feedback information provided by local farmers, we investigated the new genetic resource -Black-bone goat.The investigations included distribution range, central production area, natural ecological conditions, and the local humanistic and social economic backgrounds in Tongshan County.Investigation was conducted in the form of visitation, interview and symposium in Tongshan on the history, number, and food therapy of Black-bone goat.Records concerning the history of Black-bone goat were searched in "Tongshan County Folklore Record" (Yu, 1918).Relevent meteorological data were obtained in Hubei Bureau of Meteorology.

Body weight and body size measurement
According to the information provided by farmers, there were 1129 black-bone goats in this area, and most of them were in Jiugong Mountain and Yangfanglin townships.Then 412 goats were selected randomly in these two townships to look at body appearance.The following data were measured: the birth weight of 10 males and 10 females, the weight at 3 month of age of 20 males and 25 females, the weight at 6, 12 and 36 months of age.The body length, chest girth length, withers height and cannon circumference of the goats at 6, 12 and 36 months of age were also measured.Litter size was calculated from 61 births.The reproductive performances, such as age at puberty, gestation length, length of estrous cycle, etc were recorded according to the information provided by farmers.

Carcass measurement
Four black-bone goats (two bucks and two female goats), aged one year old were selected to be slaughtered.They were held overnight without feed before slaughter.The dressed weight, dressing percentage and lean percentage were measured based on National Standard for Chinese Cattle, Sheep and Goat Industry (GB 18393, 2001).Loin-eye area and back fat thickness were measured using an Aquila Vet veterinary Ultrasound Scanner.

Distribution of the population
The black-bone goat is mainly distributed in the mountainous area of Tongshan County.This county is an administrative county belonging to Xianning City, about 200 km southeast of Wuhan City which is the capital of Hubei Province.

Natural environment of production area
Tongshan County is located between 114°14' and 114°58' longitude east and 29°51' latitude north which belongs to north subtropical monsoon climate zone.The total area amounts to 2680 km 2 with an average elevation of 1,400 m.It has four distinguishable seasons, consisting of muggy summers and cold winters with plenty of sunshine, abundant rainfall and long frost-free days.The annual average sunlight length is 1845 h.The average yearly temperature is 16.3°C.January is the coldest month with a minimum temperature of -20°C (February 1, 1969, Jiugongshan Tonggubao).July is the hottest month in a year with the highest temperature recorded being 40.5°C (July 9, 1978, Tongyang).There are about 226 to 248 frost free days every year.The annual precipitation amounts to 1,500 mm, over 70% of which occurs in spring and summer.

Body shape and appearances
The color of thick hair can mainly be classified into 2 types: (1) black type with black hairs and (2) black head type whose head and neck is black and the body is white (Figure 1).The black type makes up to 42% of the population and the black head type 45% (412 samples), the rest (13%) are covered with mixed coat, such as grey, black and white, brown and yellow.
In the population, 75.2% have horns and 24.8% are without horns.The shape and size of the horn vary quite differently among the population.The color of the skin is black.Other black tissues include lips, gums, teeth, tongue, nose, eye socket, eye iris, anus, vulva, tail tip, penis, and nipples (Figure 2).

Body measurements and body weight
The average birth weight of Black-bone goat is 1.83 kg for male kids and 1.60 kg for females.The weaning weight at 3 month of age is about 9.50 kg for males and and 8.75 kg for females, respectively.Body measurements and body weight of Black-bone goat are listed in Table 1.
The body weight and body size of some goat breeds in China are depicted in Table 2.The yearling weight of Black-bone goat is lower than that of famous Boer goat (36.9 kg, Schoeman et al., 1997), but is above the average of Chinese goats.So Black-bone goat is a good genetic resource for meat-type breeding in this area.

Reproductive performances
Black-bone goats have an early sexual maturation with the age at puberty being 94 to 125 days.The length of   2).Usually, the goats can kid twice a year or three times in two years.Most of the first litters (85.24%) are single and the remaining are twins.
The litter size of multiparous goats is mainly 2 or 3 with 85% twins and 14% triplet.The litter size of Black-bone goat is similar to most of Chinese goats (Table 2).

Carcass measurement and meat quality
The live weight, dressed weight, dressing percentage, meat weight and meat percentage at 12 months was 22.32 kg, 10.95 kg, 49.02%, 8.01 kg and 35.42%, respectively.
The carcass traits of some goat breeds in China are depicted in Table 2.The carcass traits of Black-bone goats are similar to those of most Chinese indigenous goat breeds (Table 2).Most of these indigenous breeds can yield only 7 to 15 kg carcass weight, which is lower than the average carcass weight in China (13 kg) and Australia (25 kg, Wang et al., 2011).
The periosteum and marrow are black when the body is dissected (Figure 2a) and all the cartilaginous tissues are black while normal native goat bone looks white (Picture 2b).That is why local people call these goats "Black-bone" goats.The trachea, stomach, heart, liver, spleen, lung, kidney, uterus, ovary, oviduct are all black (Picture 2).
According to the results of Aquila Vet Veterinary Ultrasound Scanner, Loin eye area and back fat thickness of Black-bone bucks are 6.12 cm 2 and 0.18 cm, respectively.The values for the does are 5.82 cm 2 and 0.20 cm, respectively.

Origin of the population
Tongshan County is isolated from the outside by many high mountains.Due to the geographical constraint, the traffic condition is extremely difficult in Tongshan for a long period, so it is almost an isolated area.
According to "Tongshan County Folklore Records", there were 73 kinds of animals around Tongshan in 1910, most of them were pigs, cattle, dogs, goats and horses, and indicated that goats were one of the main livestock species during that period.In the villages, most of the goats belonged to local farmers and one family usually kept 2~5 head, sometime only one.These goats mated randomly and few new breeding stocks were brought in from the outside world, thus the goats were experiencing inbreeding.No one knows when and where and how the black-bone goats appeared in this area.We thought that the geographical isolation and continued inbreeding might be the reason.

Medicinal evaluation
The most unique feature of Black-bone goats is the black pigmentation which makes most of its tissues to be black.Fortunately, many Chinese prefer black food and it is a part of traditional food culture.In this culture, black food has many mysterious functions.
In this investigation, it was found that most of the local farmers and some civil doctors believe that Black-bone goat products (meat, bone and blood) have medicinal effects.Some people believe that Black-bone goat's blood and bone can be used as medicine to expel wind and remove damness, promote blood circulation and remove blood stasis, alleviate gastrointestinal discomfort.The medicinal value of black food is highly valued by this culture, so Black-bone goat has very high market potential.In fact, it is a good project for mountain farmers now.Farmers can sell their Black-bone goats at very high price, which may result in loss of the genetic resource as the total population size is small.

Genetic conservation
Black-bone goat has potential values for market and it is a rare and precious population, but its population size is very small.A few goats are even mixed with normal black coat goats and this may lead to hybridizing the

Figure 1 .Figure 2 .
Figure 1.Appearances of Black-bone goats a) Black type: Male, black coat, small horn (b) Black type: Female, black coat, without horn, (c) Black head type: Female, black head, white body coat, long horn and (d) Black head type: male, black head, mainly white body coat, long horn.

Table 1 .
Body measurements and weight of Black-bone goat.