Relationship between litter size and farrowing conditions was examined using 110 litters from crossbred sows. The time required for piglet expulsion was found to be 195±150 minutes, showing large differences among the individuals. Therefore, by excluding the sows with an interval of piglet expulsions over 60 minutes, the relationship of the inter-litter interval and the time for farrowing the entire litter to the litter size was investigated, by which the inter-litter interval and the time needed for expulsion of all piglets turned out to be 10.2 minutes and 191.4 minutes, respectively, for the litter size of 14, 12.4 minutes and 157.1 minutes, respectively, for that of 10, and 20.1 minutes and 143.2 minutes, respectively, for that of 6. In every pair of the litter sizes, a significant difference (p<0.01) was noted.
The relationship between the litter size and conditions of newborn piglets was then examined on the basis of the farrowing records of 1, 348 litters. The parity of the sows was 3.62±2.55 and the litter size was 11.13±1.84. With regard to the rate of expulsion of abnormal piglets, immature, stillborn and mummified piglets were 5.18, 5.81 and 1.28%, respectively. A negative correlation was found out (r=-0.793) between the litter size and the ratio of expulsion of normal piglets, while with regard to the relationship between the litter size and the ratio of abnormal piglets, no significant tendency was found in mummified piglets, but significant correlations were found (p<0.01) in the cases of immature piglets (r=0.807) and stillborn piglets (r=0.794).

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The present paper describes the results of our study to measure the density of dusts and number of airborne micro-organisms in four pigpens for fattening pigs in winter, in order to examine the actual environmental conditions in pigpens for this purpose. The high-volume air sampler and the digital dust-meter were used for measuring the density of dusts, while the aerial bacteria were determined according to the normal method, i. e. measuring the number of bacteria dropped on agar plate in five minutes.
(1) The highest dust density measured was 10.794mg/m³ in the H Farm (Growing house), while the lowest one was 0.797mg/m³ in our college farm (fattening house).
(2) The largest number of bacteria measured was 1, 487 in the H Farm (Growing house), while the smallest one was 79 in our college farm (fattening house).
(3) The dust density measured with the digital dustmeter ranged from 53 down to 7 per minute. In order to compare the dust density with the airborne bacteria, these factors were counted at one hour and at five minutes and were compared with each other, respectively.
(4) The correlation coefficient between the dust density measured by the high-volume air sampler and the aerial bacteria proved to have r=0.795, while the regression equation of the dust density (X) to the aerial bacteria (Y) was found out to be Y=149.84X-1.17. From the dust density (Y) and the one-hour dust count (X), r=0.860 and Y=0.00581 X-1.55 could be obtained, while, from the five-minutes dust count (X) and the aerial bacteria (Y), r=0.913 and Y=14.58X-736.44 could be obtained.
(5) Of all the behaviors of pigs, three groups of behaviors were made, i. e. the behaviors in daytime, those before sleeping and those while sleeping, and the dust density for each of the 3 time groups was each determined. The highest dust density per minute was the smallest while sleeping, whereas the highest was noted before sleeping.
(6) The results of the study revealed that, in order to measure the environmental factors in relation to the dust density in pigpens, using the one-minute dust density, it would be necessary to determine the dust counts at a uniform interval and besides frequently.

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The analysis was based on the data of pig carcasses from 30 local hog farms in 1987. Twelve items of the carcass were evaluated, such as unit price, average weight, standard deviation of average weight per farm, market price of the excellent (Jo) on the marketed day, average loss of market price from that of the excellent, etc.
These items can be classified into three categories: 1) Marketing techniques to meet the market conditions, 2) Quality control techniques to attain better prices, and 3) Carcass weight control techniques.
These groups are independent of each other.
In order to define the factors affecting the unit price, multiple regression equation (by forward method) of which the response variable (Y) was the carcass unit price and the rest of items were explanatory variables.
These computations resulted in the identification of three most effective factors. The following conclusions were obtained.
1. The multiple regression equation was as follows:
Y=-60.563+1.067X₁+0.323X₂-1.211X₃
(0.046) (0.033) (0.340)
R²=0.970 R²2=0.967 Se=0.963 d. f=26
where, X₁ was the unit price of “Jo” on the marketed day, while X₂ was the proportion of “Jo” carcass to the total marketed amount, and X₃ was the standard deviation of the mean weight per farm.
2. The adjusted coefficient of multiple determination (R²) was 0.967, indicating that 96.7% of the total variations in the unit price could be explained by the three variables included in the equation, and the standard error was 0.963.
3. Standardized regression coefficients were 0.833, 0.439 and -0.158, respectively, for the variables of X₁, X₂ and X₃.
As the result of these coefficients, the market price of “Jo” carcass on the marketed day proved to be the most important factor for the improvement of the mean carcass unit price.

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The possibility of effects of fraternity sizes on the growth of piglets, meat prodiction traits of growing pigs and reproduction traits of sows was investigated. The traits examined were the body weight from birth up to 8 weeks of age, and weight gain of 2216 Landrace line piglets, the meat production traits of 291 growing boars and 735 growing guts and the reproduction traits of 239 sows of the first down to the sixth generations Landrace line pigs. The piglets were given feed from 2 weeks of age and weaned at 5 weeks of age. The number of the successfully weaned piglets was termed as the fraternity size. The fraternity sizes were classified into 4 groups of less than 7, 8-9, 10-11 and more than 12.
The differences in the body weight and the weight gain between the group of less than 7 and that of more than 12 piglets were 0.1, 0.31, 0.58, 1.08, 1.62, 2.04, and 2.64kg at birth, 1, 2, 3, 4, 5 and 8 weeks of age, respectively, and 0.47kg and 1.47kg for the body weight gain from the birth to 2 weeks of age and that from 2 to 5 weeks of age, respectively. All the differences thus noted were significant. It was found out that the larger the litter size, the poorer the growth was. However, the effect of the litter size was not significant upon the weight gain (0.54kg) from the 5 weeks down to 8 weeks of age. It was clarified that the effect of the litter size was significant upon the body weights of the growing boars and gilts at age of 8 weeks and upon the age of reaching the body weight of 30kg, but that the effect of the fraternity size was not appreciable upon the age of reaching the body weight of 90kg, daily mean weight gain, backfat thickness, daily mean feed intake, feed conversion ratio, selection index value, or numbers of farrowings by sows or number of produced piglets. These results suggest that the effects of fraternity size on the growth, meat production and reproduction traits are tapered off as age advances.

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Three each of castrated males and females of the crossbreds with Berkshire × Wild boar (Sus scrofa leucomystax) were fattened up to 90kg and used for the present study on the influences of sex and anatomical locations on the intramuscular lipids.
The composition of intramuscular lipids and that of the fatty acids in the total lipids, neutral lipids, phospholipids, phosphatidyl ethanolamine and phosphatidyl choline fractions were examined for M. longissimus thoracis, M. biceps femoris and M. semimembranosus which were taken from the three each slaughtered at 90kg of body weight. The following results were obtained.
1) The amounts of triacylglycerol and neutral lipids in the lipids were larger in the castrated males than in the females. The amount of phospholipids tended to be larger in the M. biceps femoris among other muscles.
2) No appreciable difference was found out in the compositions of fatty acids in the total and neutral lipids between the castrated males and the females. The ratio of the total saturated fatty acids was the highest in the M. longissimus thoracis.
3) There were no significant influences in connection with sex and anatomical locations upon the compositions of fatty acids in phospholipids or phosphatidyl choline.
4) The differences in the compositions of fatty acids in phosphatidyl ethanolamine in conjunction with sex and anatomical locations were comparatively small.
From the above-mentioned results, it was found out that the differences in the composition of fatty acids of the crossbreds at body weight of 90kg between sexes were smaller than those among the muscles.

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The contractile actions of carbetocin (a long-acting oxytocin), oxytocin and prostaglandin F_2α (PG) on porcine uterus were comparatively evaluated in vivo. Six healthy post-weaning sows, each weighing between 195kg and 300kg were given 25 IU of oxytocin, 0.2mg of carbetocin and 10mg of PG on the first, second and third day, respectively, by intravenous administration.
These drugs induced appreciable increase in uterine contraction soon after their administration, and the frequency of uterine contraction also was increased.
The mean duration of the responding contraction and the amplitude of the contraction were 312.5 minutes and 54.0mmHg by carbetocin, 17, 0 minutes and 51.6mmHg by oxytocin and 145.0 minutes and 62.8mmHg by PG. The effect for its duration by carbetocin proved to be approx. 2.7 times longer than that of oxytocin. No adverse effect was experienced upon the uterine contraction with any of the administered drugs, but PG caused redness of skin, vomiting, urination and defecation since immediately after its injection, all of which lasted for approx. 30 minutes thereafter.

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