Pig raising has a long history in China. As early as about 6000-9000 years ago, local wild boars had been domesticated by the Chinese. The ancient Chinese people also paid great attention to selective breeding. In the Han Dynasty the superiority of Chinese pigs were known at home and abroad. During the Han Dynasty the small-ear pig in Southern China was introduced into Dachin Country (Roman Empire) to be bred into the ancient Roman pig. Up to the seventeenth and eighteenth centuries, the Chinese pig (Guangdong pig varietry) was introduced into the western countries such as the Great Britain and the USA. Since then it played an important role in the improvement of pig varieties in these countries.
In recent years, due to the shortage of pig variety resources, some countries with developed pig industry have paid great attention to the Chinese pig varieties with high reproductivity and introduced them for crossbreeding. The results have been encouraging. And researches have been carried out in France, Britain, Japan and the Netherlands using Chines pigs to improve the reproductivity of pig varieties in these countries.
World wide attension has been focused on the excellent characters of Chinese pigs and the breeding and management technology. They are the precious wealth of the whole mankind. We are thus expecting a glorious future.

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This experiment was carried out to clarify the effects on the survival and acrosome morphology of boar spermatozoa of fructo-oligosaccharides which might provide protection during freezing and thawing.
Sperm-rich fraction of ejaculate was collected from 8 boars, diluted with pre-diluent, held at 15°C for 3h, centrifuged at 800g for 10min. Sperm were suspended in fructo-oligosaccharides diluents containing 20% egg yolk and cooled to 5°C for 2h. Before freezing, cooled semen was rediluted with an equal volume of diluent containing 6% glycerol and 1.48% OEP. Finally diluted semen was packaged in 5ml straw and frozen in liquid nitrogen vapour. Thawed semen at 40°C was rediluted with thawing diluent and then incubated at 37°C for 180 or 240min. to examine sperm survival and acrosome morphology.
Fructo-oligosaccharides were prepared from sucrose through the transfructosylating action of enzymes. 1-kestose (GF₂), Nystose (GF₃), 1^F-β-fructo-fructo-furanosylnystose (GF₄) and Neosugar P (comprised of GF₂, GF₃ and GF₄ at 40, 45 and 10%) were used for diluents. GF₃ and GF₄ were significantly effective for the maintenance of motility and acrosome morphology of frozen-thawed boar sperm. This result indicates that GF₃ and GF₄ are useful cryoprotectants for the cell.

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The effects of centrifugal conditions in porcine blood (time: 5, 10, 15 and 20min.; revolution speed: 1, 000, 2, 000, 3, 000 and 4, 000rpm) on the hemolysis and biochemical constituents of serum were examined. The following findings were obtained.
As for the influence of the centrifugal time, in case of centrifuged for 5, 10, 15 and 20 minutes respectively at 3, 000rpm, the hemolysis of 5 minutes case was significantly higher than the others and the spectrophotometric absorbance became lower as the time extended. As for LDH out of biochemical constituents, 5 minutes case was significantly higher than the other cases and as time extended, the value had a tendency to become lower. Furthermore as for Mg, 5 minutes case was significantly lower than 15 and 20 minutes cases.
As for the influence of the revolution speed, in case of centrifuged for 10 minutes at 1, 000, 2, 000, 3, 000 and 4, 000rpm respectively, the hemolysis of 1, 000rpm case was significantly higher than the other revolution speeds, and the hemolysis became lower as revolution speed went up. Beside, LDH, serum iron and Mg at 1, 000rpm were significantly higher than the other cases. Each value became lower as revolution speed went up.

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The aim of this study is to clarify the factors for the reduction of pig production cost and to determine the constituent factors affecting the pork carcass production cost per kIlogram. The data are based on the pig farm business survey by Yamagata Livestock Association. Those were collected from 132 pig operations and classified into three groups: the first was the high price period on pork carcass and feed (from 1981 to 1983), the second was the falling price period on both items (from 1984 to 1986) and the third was the low price period on both items (from 1987 to 1989).
The factors of pig production cost are clarified by multiple regression analysis and stepwise forward regression method is used to select the independent variables. The dependent variable is the production cost of pork carcass per kilogram and the indepedent variables are 21 items surveyed on pig farms such as: feed cost per kg gain, yearly numbers of weaned piglets per sow, yearly frequency of farrowing per sow, daily gain, feed conversion ratio and so on.
The results of this study are as follows:
1) The multiple correlation coefficients and the contribution rates are 0.920 and 81.7% in the first period, 0.942 and 86.9% in the second period, and 0.859 and 71.4% in the third period, respectively.
2) In the frst period, the contribution rate of the feed cost pet kg gain is 61.4% and that of the yearly numbers of weaned piglets per sow is 8.6%.
3) In the second period, the contribution rate of the feed cost per kg gain is 57.8% and that of the yearly frequency of farrowing per sow is 17.9%.
4) In the third period, the contribution rate of the feed cost per kg gain is 40.1% and that of the yearly frequency of farrowing per sow is 15.8%.
The above figures for the contribution rate stand for the values adjusted by degrees of freedom on the identification of five factors.
From the results of this study, the most effective factor of reducing the pig production cost is the feed cost per kg gain. Moreover, pig farmers have to increase the productivity of sow and hog feeding.

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The effects of hemolytic severity in porcine blood on the measured value of biochemical constituents of serum were evaluated using the sera taken from blood sample with various degree of hemolysis.
The following results were obtained.
1. The linear regression of total heme pigment content (Y; mmol/ml), which indicates hemolytic severity, on spectrophotometric absorbance (X) was given as
Y=0.0644X-0.0050
The correlation between these two variables was 0.98^**.
2. Effects of hemolysis on measurement values
1) The items of which measured values did not change with severity of hemolysis were TP, Alb, α-glob, γ-glob, A/G, BUN, ALP, LDH₃, Glu, T-cho, Fe, Ca, Mg and IP.
2) The items of which measured values increased with increasing severity of hemolysis were β-glob, GOT, GPT, LDH activity, LDH₄ and LDH₅.
3) The items of which measured values decreased with increasing severity of hemolysis were TG, PL, LDH₁ and LDH₂.

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The growth performance and meat productivity of three-way crosses were compared. The three-way crosses were prpduced by the terminal sires of Duroc (D), Berkshire (B) or Meishan (M) and Landrace × Large white F₁ (LW) dams. These crosses were symbolized as LWD, LWB and LWM in this paper, respectively. Thirty-six three-way cross bred pigs, each six barrows and six gilts from LWD, LWB and LWM, were used. They were reared individually and fed ad libitum from 30 to 105kg of body weight. At 70kg of body weight, feed was changed from raising ration to finishing ration. At 105kg of body weight, pigs were slaughtered after 24 hours of fasting and carcass characteristics were mesaured according to the method of the progeny test. Analysis of variance which took cross bred and sex as sources of variance was conducted. The LWB was significantly older than LWD and LWM in the age at 70kg of body weight (LWB, LWD and LWM: 116.5, 110.6 and 110.3 days of age, respectively) and at 105kg of body weight (LWB, LWD and LWM: 159.8, 146.8 and 148.8 days of age, respectively). In the average daily gain, LWB was significantly inferior to LWD and LWM (LWB, LWD and LWM: 866, 976 and 948g, respectively). The cross LWM was the thickest of all cross breds in backfat thickness at all the positions measured and LWB was thicker than LWD in some positions. The cross LWM showed lower carcass weight, dressing percentage and shorter carcass, back-loin and loin than the other two cross breds. Furthermore, the ratio of belly-loin to carcass was significantly higher in LWM than LWD and LWB. The LWM had significantly heavier head and large plus small intestine than LWD and LWB. These results suggest that terminal sire significantly affect the growth performance and the meat productivity of three-way cross bred of pigs.

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In order to predict the fat percentages of whole body and of carcass with the subcutaneous fat thickness and the fat area percentage of carcass cross section, 69 three way crossbred pigs (37 barrows and 32 gilts) were used. The pigs were slaughtered at 70kg and 105kg of body weight, and the subcutaneous fat thickness at the shoulder, the mid back, the loin and the points 2, 4, 6, and 10cm down from the dorsal mid-line at the last rib in the left half carcass were measured. The right half carcass was frozen at -30°C, sliced by electric saw at each thoracic and lumber vertebra and the each cross section of carcass was photocopied. The fat area on the photocopy was measured with a digitizer. The each slice of carcass was grounded, mixed, sampled and chemically analyzed. The fat percentages of whole body and of carcass at 70kg of body weight were predicted with the multiple regression equations which consist of the carcass weight, the subcutaneous fat thickness under the points of 4 and 8cm down from the dorsal mid-line at the last rib. The R_s² and the residual standard errors (RSEs) of the multiple regressions were 0.855, 0.831 and 0.870, 1.107 for the fat percentages of whole body and of carcass, respectively. At 105kg of body weight, whole body fat percentage was predicted as R²=0.923 and RSE=0.865 using the 4 independendent variables (the carcass weight, the subcutaneous fat thickness under the points of 4 and 10cm down from the dorsal mid-line at the last rib and the mean fat thickness). The carcass fat percentage was predicted as R²=0.911 and RSE=1.045 using the 4 independent variables (the carcass weight, the subcutaneous fat thickness under the points of 4 and 10cm down from the dorsal mid-line at the last rib and mid back). Using the 5 independent variables (the fat area percentages of the carcass cross section at the 3rd, 11th, 12th, 16th thoracic vertebra and the carcass weight) the whole body fat percentage was predicted as R²=0.823 and RSE=0.995 at 70kg of body weight. The carcass fat percentage was predicted as R²=0.814 and RSE=1.198 using the 4 independent variables (the carcass weight, the fat area percentages of the carcass cross section at the 3rd, 7th and 11th thoracic vertebra). Furthermore, at 105kg of body weight, the whole body fat percentage was predicted as R²=0.910 and RSE=0.918 using the 4 independent variables (the carcass weight, the fat area percentages of the carcass cross section at the 10th, 14th thoracic vertebra and lst lumber vertebra). The carcass fat percentage was predicted as R²=0.926 and RSE=0.935 using 4 variables (the carcass weight, the fat area percentages of the carcass cross section at the 3rd, 14th thoracic vertebra and lst lumber vertebra). These results show that the subcutaneous fat thickness at the last rib and the cross section fat area percentage were the most important variables for the estimation of fat percentage in whole body and in carcass of pige.

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