Removal of feces from pigpens takes away a large portion of total labor in pig farming. The purpose of our present study consists in clarifying and favorably utilizing the dunging habit of swine, so as to save labor in cleaning the pigpens.
In the first part of our study, we investigated the lunging sites of pigs within a pen in relation to the situations of adjacent pens. The following results were obtained.
1) Generally, pigs liked to dung near the partitioning fence or water supplier, particularly near the corners of the pen, and very little or no feces were found in the center of the pen or near the feeder.
2) If one of the adjacent pens was not occupied, the pigs selected the area near the empty pen for resting, and the area adjacent to the occupied pen for dunging.
3) The type of partitioning fence between pens exerts influences upon the dunging habit of pigs. If both of adjacent pens were occupied and one side of the partitioning fence was boarded up, while the other side was of see-through fence, a larger portion of dungs was found on the side of the see-through fence.
4) Once established, the dunging habit and the dunging site were maintained even though the situations of the pen were slightly changed. However, irregular noises such as squeaking of pigs from the pen near the resting site has an immediate effect upon the pigs to respond so strongly to the noise as to change their dunging sites.
Specifically, it may be therefore claimed that pigs are very sensitive to sudden changes in the environments (e. g. irregular noises or movements), though they appear insensitive to the established environments due to familiarity to them.
5) At initial stage of growth, pigs tended to have no specific site for Bunging. It is attributable to that (1) space needed by young pigs for resting is relatively small in comparison with the size of a pen and that (2) sense of self-defense against enemies has not yet been developed in young pigs and therefore they are not choosy in selecting safe corners for resting.
6) There were minor variations in dunging sites by seasons, particularly between summer and winter. The variations may be attributable to that pigs prefer to rest in comfortable areas, e. g. breezy, wet, and cool floor during summer and sunny and dry areas during winter.
7) In the present study using the trial pen as shown in Fig. 1, no difficulty was experienced in concentrating the dunging area on either of both sides of the narrower fence, but it was difficult to establish a satisfactory dunging area on the side of the wider fence, i. e, so-called dunging sector of the Danish pigpen. It may be conjectured that the shape of the pen can exert a considerable effect on the dunging habit of the pigs partly because the shape of the pen was rectangular.

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Subsequent to our previous report on the dunging habit of pigs in relation to the setting and environments of adjacent pigpens, we have attempted in the present study to check various factors within the pigpens, which exert influences upon the dunging habits of pigs. The following results were obtained:
1) It was found out that once the feeder was placed in an area favorable to their living and the comfortable conditions were perceived, the pigs find no difficulties in choosing their resting area and dunging site, and as a result, the site for dunging also is often concentrated. In contrast, if the location of the feeder is incompatible with the comfort of living conditions, the pigs tend to lay preference rather to the site of the feeder, and as a result, the site of dunging tends to be unspecific.
2) As the floor around the water supplier is usually wet with consequently poorer living conditions, the particular area tends to be preferred as the dunging site to the other conditions or other sites. However, by raising the floor around the water supplier, the pigs can use the area for their resting.
3) Presence of two or more sites with comparable safeguard against enemis and with comparable living conditions within a pigpen tends to have the pigs choosy for the resting site and consequently for the dunging sites which were not therefore consistent.
4) When the floor space of a pigpen allocated for the pigs to rest is more than enough, it is difficult for the pigs to concentrate the dunging sites within the space expected by the pig farmers.
5) In conclusion, it is desirable to meet the following requirements in order to concentrate the dunging sites of pigs within a limited range.
(1) The floor level of the resting area should be elevated higher than that of the dunging area. The fence adjacent to the resting area should be of a boarded structure not allowing see-through so as to provide them with sense of security. The feeder should be placed within the particular area.
(2) The fence adjacent to the dunging area should be of a see-through structure. The water supplier should be placed in this area so as to keep the floor generally wet. The access door should desirably be located within this aera as far as possible.
(3) A reasonable (not too few) number of pigs against the area of the resting place should be kept in the pens.

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In the two previous reports, we described the influences of the life-long in-door group-feeding upon the dunging sites of pigs in particular relationship to the conditions of the adjacent pigpens and the structure of pigpens. In the present study, we have conducted experiments on the relationship between the dunging behaviors of pigs within pigpens with attaehed open yards and the external environmental factors. The results were as described below.
1) Under the conditions kept in a pigpen with free access to the open yards, the pigs tend to prefer dunging outdoors to that within the pigpen. This would be attributable to the factors of instability in the outdoor yards such as the irregularities of weather and noises and passage of other animals including humans, for which reason the pigs may instinctively prefer using the inside of the pigpen as the resting sector to the open space, which is used for dunging and walking area. However, if excessive irregularities causing horror or sense of over-instability to them such as stormy wind or heavy rainfall are noted, pigs tend to hesitate and very often choose the inside of the pigpen as the dunging area.
2) It appeared that pigs can adapt themselves for the gradual fall of temperature, but they tended to be hesitant to go outdoors on the days with sudden drop in the atmospheric temperature and tended to dung in the pigpens.
3) Comparison between winter and summer in terms of their dungings revealed that more or less dungs were found in the pigpens in the winter, whereas the majority of the summer days saw no dunging in the pigpen. This finding may be attributed to the fact that the pigs take their resting sites all over the floor of the pen, whereas, in winter, they rest in groups to warm each other, by which considerably large space is left in the floor for their dunging.
4) It was noted that once the diarrheal feces by a pig soiled the floor of the pigpen, the others tended to fllow it with dunging in the pen. This phenomenon suggested the likelihood that there would be a type of learning effects by the pigs to refrain from dunging in the pen by keeping the inside of the pen as clean as possible at all times.
5) As a general trend, it was noted that the size and structure of a pigpen have little to do with the dunging behaviors if there is an open yard attached. However, if the pigs in the pigpen on the opposite side of the partitioning fence are kept confined within it so as to force their dunging therein, the pigs kept in the pigpen on this side also tended to dung within the pigpen on this side possibly because they are lured by the pigs on the opposite side. It was therefore conjectured that it is desirable to have all the partitioning fences in the pigpen made of boarded type which will not allow any see-through.

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It is claimed that there is a big fluctuation in the number of vertebrae of swine and that the fluctuation is related to the shapes and quality of carcasses. In the present study, the relationship between the number of vertebrae and growh or both shapes and quality of carcasses of swine was evaluated using the data of 2761 Landrace pigs. The results revealed the following findings.
1. The pigs with above average number of vertebrae tend to have greater body lengths and smaller girth from those with less vertebrae.
2. An evident relationship was identified between the numbers of vertebrae and the lengths of carcasses and back-loin II, which proved to be 1.78 and 2.01cm longer, respectively, per additonal vertebrae.
3. On the basis of a fixed age (in days after birth), the correlation coefficients between the numbers of vertebrae and the lengths of carcasses and back-loin II were identified as 0.390 and 0.621, respectively.
4. No significant difference was noted among various types of vertebrae in terms of average daily weight gain, age to attain a weight of 90kg, on thickness of backfat and belly fat.
The pigs with larger numbers of vertebrae tended to have greater lengths of carcasses and back-loin II and higher percentages of loin and belly, but tended to have smaller loin eye, shoulder, and ham.

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The following results could be obtained from the present study on the relationship between the variations in the number of vertebrae and the heritability of variations in the number of the vertebrae of Landrace pigs by means of the analysis of the data with 117 sires, 425 dams, and 3819 piglets from them.
1. The number of thoracic vertebrae of Landrace pigs ranged from 14 up to 17. The frequency of emergence of the type with 16 vertebrae was the highest, while the counterpart of the type with 15 vertebrae was about half of that of 16. The frequencies of the types of 14 and 17 vertebrae were very low.
2. The number of lumbar vertebrae ranged from 5 up to 7. Those with 6 lumbar vertebrae was of the highest frequency, followed by those with 7 and 5 lumbar vertebae in the decresing order.
3.The number of vertebrae including both the thoracic and lumbar vertebrae ranged from 20 up to 23. Those with 21 and 22 vertebrae shared approx. 95%, and were of the highest frequency.
4. Even with the mating of parents with the same numbers of vertebrae, variations in the numbers of vertebrae were noted in the piglets farrowed by them. Mating of the pigs with larger numbers of vertebrae produced piglets with larger average numbers of vertebrae than the counterparts of the piglets farrowed by the parents with smaller numbers of vertebrae. The numbers of vertebrae showed no differences by generation.
5. The heritability of the numbers of vertebrae was as described in Tables 6, 7, and 8. The results suggested that selection of individual pigs for mating would be effective for increasing the numbers of vertebrae because of the high heritability, except for the one concerning lumbar vertebrae.

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The therapeutic efficacy of ronidazole, a synthetic antimicrobial agent of nitromidazole origin, against exrerimental swine dysentery in vivo was examined in the present study, along with its antimicrobial activity in vitro against Treponema hyodysenteriae. The results were described as follows.
1. In vitro study: The antimicrobial activity of ronidazole against isolates of T. hyodysenteriae was evaluated by the agar plate dilution method. The minimum inhibitory concentrations proved to be≤0.1μg/ml for five isolates used in the present study, showing its high antimicrobial activity.
2. In vivo study: The therapeutic efficacy of ronidazole against swine dysentery with SPF pigs intentionally infected by the pure culture of T. hyodysenteriae was evaluated by its administration for 3 successive days through water medication of ronidazole in a concentration of 0.003 or 0.006%. The results revealed that the affected pigs were recovered within 48 hours after initiating its administration and T. hyodysenteriae was eliminated from the feces. Normal weight gain and feed efficiency were also recovered. There was no case of onset of any symptom in the co-housing pigs during the experimental period of 10 days after terminating its administration, nor was there any recurrence of any symptoms from the recovered pigs.

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