On closed herd breeding in swine, it is necessary to reserve matings in some excess taking loss after mating into account for maintenance of a constant herd size. Usually, post-mating cull would be necessary to adjust herd size. It is an usual practice to use performance of gilt as a criterion for the post-mating cull.
A comparison between selection differentials caused by post-mating cull based on performance of gilt and mean performance of pair mated was undertaken.
Through the study using constraction and numerical integration with method of successive approximation, it was clarified that, in the case of random and disassortative mating, culling with mean of pair would result selection differentials of 3-5% larger than that with gilt in standard deviation of the performance unit. This difference in selection differentials will be accumulated with every successive generation to an amount which cannot be ignored. Further, the extra effort required for changing the selection criterion from performance of gilt to mean performance of pair mated is small.
Therefore, the change in selection criterion would be an effective step toward efficient closed herd breeding in swine.

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It is of extremely great importance to diagnose the pregnancy of swine at an early stage from both viewpoints of the productivity of swine and the management of pregnant swine. Our present study has been intended for as accurate and simple as possible diagnosis of pregnancy of swine. Our experiment was carired out with a Japanese ultrasonic doppler-phone, getting the following results.
1) At the initial stage of pregnancy, the DS of feti tends to be more audible in the vicinity of the inguinal region of hind legs of swine, and is more audible at the even more anterior region as the pregnancy advances.
2) The accuracy of diagnosis of pregnancy with the ultrasonic doppler method was 80% during the period of 22-29 after mating, 62% in 30-39 days, 77% in 40-49 days, and 99-100% after 50 days from the mating.
3) The fetal pulsation count was found to be approx. 240 beats per minute at the initial stage of pregnancy, but tended to decrease slightly as the pregnancy advanced. The pulsation count of dams is about half of that of feti. The variations in the pulsation counts with the varying stages of pregnancy are not signifiicant.
4) The time in which the fetal DS is audible ranges from about 5 seconds to 10 minutes, and the first sound is audible at 1-2 minues after starting the determination, if the tester gets experienced.
On the basis of the above results, it can be claimed that this method is extremely effective as a method for diagnosis of pregnancy of swine in field trials, particularly as an early pregnancy identification method.

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A series of surveys and experimental studies have beenc arried out by us on the outbreak of esophagogastric ulcer in swine for 4 years from May 1969 to April 1973. Of 1, 763 hogs which were slaughtered soon after their receipts into alaughterhouses and which were subjected to inspection on their stomachs, those with normal stomach shared 54.7%, while balance 45.3% were those with more or less abnormalities in their esophagogastric region (insufficient keratinization 31.3%, erosion 5.4%, and ulcer 8.5%), thus indicating the frequent onsets of so-called porcine gastric ulcer also in Japan.
The fact of interest which was found out during our study was that the esophagogastic ulcer occurred in a higher frequency in the herds of swine which were grown only with microparticulated feedstuffs without using litters in the pigpens. The frequency in this case amounted to as high as more than 80%, and the frequency of serious erosion and ulcer amounted to as high as more than 25%. About 70% of the swine culled due to the illgrowth in these herds were attributable mainly to ulcers.
From the study on the damages inflicted by diseases upon the piggeries mainly intended for growing the fattening pigs, it was found out that deaths were 173 (0.63%) mainly due to gastric ulcer of all the 27, 150 hogs produced in 4 years. Of the 1, 239 hogs culled (4.5%), about 70% may be attributed to gastric ulcer. Therefore, about 4% of all the dead or culled swine could be claimed to have been directly damaged by the esophagogastic abnormalities, which shared the principal part of the economical losses inflicted upon swine by diseases.
Of all the esophagogastric abnormalities in swine, those at the stage of insufficient keratinization do not adversely affect their growths and related aspects. However, if the abnormalities are aggravated into erosion and ulcer, various adverse effects are exerted upon the symptoms depenidng on their degrees, causing deaths due to serious bleeding and due to subacute asthenia. Even if those can survive, they get into malgrowth when aggravated into chronic condition.
The relationship between the development of ulcer and various factors such as age, seasons, varieties, infections by microbes and parasites and intoxication can not particularly be regarded to be significant, but the variations in its development with sexes are substantial, amounting to 67.1% in barrows and 32.9% in guts.
The relationship between the deveopment of ulcer and stress does not seem to be directly related to development of esophagogastric abnormalities. Consequently, the hypothesis of stress by densely populated herds may be doubtful in view of the fact that there are hardly any onsets of ulcers even with the same herds if the swine are kept with litter on the pigpens.

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