Twenty-six Meishan pigs and fourteen three-way crossbred pigs produced by F₁ female from Landrace dam and Large White sire × Duroc terminal sire were fed with feed of three different TDN levels (70, 60 and 50%) during the period from 30kg to 90kg of body weight. The TDN levels were regulated by the percentages of alfalfa meal addition. The pigs were slaughtered at 90kg of body weight after fasting. The weight of each organ and the lengths of small and large intestines were recorded after the slaughter. The data of the measurements were analyzed by the minimum square method.
The total sum of the weights of all the internal organs and the wight of each of stomach, large intestine, omentum and mesentery was significantly heavier in Meishan pigs (large intestine: p<0.05, others: p<0.01) than in the crossbred pigs. The length of the large intestine was longer in the Meishan pigs (p<0.01). The weights of liver and cecum increased with decreasing TDN levels in the feed (p<0.05). Conversely, the weight of heart decreased with decreasing TDN levels in the feed (p<0.01).
There were no feed × breed interactions in any of the measured items.

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Fourty-eight animals (Beijing Black 7, Kagoshima Berkshire 11, British Berkshire 10, and Duroc breed 20) were introduced into Tokyo Prefectural Livestock Experiment Station as the original pig population for production of hybrid pigs. The genetic variations of blood groups and biochemical polymorphisms were investigated in this study as one of the attempts to clarify the genetic properties of this original population. Blood types investigated comprised eight blood groups (A, E, F, G, H, K, L and O), five serum proteins (Tf, Pa, Hp, Cp and Am), five red cell enzymes (PHI, 6PGD, PGM, ADA and EsD) and two serum allotypes (PSA-I and PSA-II), 20 loci in total. The results were as follows:
1) Eleven of the 20 loci investigated of Beijing Black pigs and 15 of the 20 loci in the other three breeds or strains were found polymorphic. Eighteen loci excluding Cp and Am loci showed polymorphism in at least one or more breed or strain.
2) The genetic variability among the four breeds or strains investigated by H. I. (gene homogeneity index), H (the expected proportion of heterozygosity per individual), P poly (the proportion of polymorphic loci) and Ne (the effective number of alleles per locus) were the lowest in Beijing Black pigs and the highest in Duroc breed. However, the differences among the four breeds or strains were found to be small.
3) On the basis of the gene frequencies at the 20 loci, the genetic distance between each other was calculated among the four pig breeds or strains using the two formulae of ROGERS and NEI to prepare the dendogram showing genetic similarities among them, It was clarified by the dendogram that Kagoshima and British Berkshires were in the closest distance, and Duroc breed and Beijing Black pigs were located further apart from them in this order.
4) The genetic distances were calculated among Beijing Black pigs, the mixed population of the four breeds or strains and the 15 breed populations investigated to date. It was clarified by the calculation that Beijing Black pigs were in the closest distance from short-ear breed, and next Large White and Middle Yorkshire breeds, and in the furthest distance from Hampshire breed. On the other hand, the mixed population was the closest to Landrace breed and the furthest to Taoyuan breed. It was clarified by the dendogram that Beijing Black pigs belonged to the Asian pig group, but it was found located fairly apart from the pig breeds of the Chinese Continent, while the mixed population belonged to Euro-American pig group and was located in the closest distance from Landrace breed.

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The author carried out studies on density and diameter of dust particles in swine houses which were dominant causes of scattering dusts. The test samples used for analysis in this study were the same as in the previous paper. The density was determined by 50ml pycnometer. The particle size was measured by comparing the reflections of dusts with unit length mark on scanning electron micrograph by vernier calipers. Dropping speed of dusts was obtained by substituting these data, coefficient of viscosity and air density at sampling into Stokes' formula.
The results were as summarized below.
(1) Solubility of dusts in pig houses in water was estimated as 20.46% (17.12-22.95%), while that in xylene was 1.16% (1.08-1.25%), which was much less than that in water. Consequently, it was demonstrated that xylene is more preferable than water for use as a medium in the measurement of dust density.
(2) On the basis of these results, density of dusts in swine houses was measured with xylene. The density of air-dried matter was 1.4374 (1.4308-1.4486). Calculated density of dry matter by subtracting moisture content was estimated as 1.4677 (1.4618-1.4778), which was about 0.03 larger than the density of air-dried matter.
(3) Particle size of dusts in this paper was defined as arithmetic average of the major axis and the minor axis. The average value of particle size obtained was 15.2±3.1μm (2.6-35.45μm), while the proportion of dusts smaller than 10μm which was so-called “respirable dust” has was estimated as 25.7%.
(4) These measured values, coefficient of viscosity and density of air at sampling were substituted into Stokes' formula, and the equation with particle size (X: cm) and dropping speed (Y: cm/sec.) resulted in Y=3, 509, 153.942X². Dropping speed of 8.1cm/sec. was obtained by substituting the average particle size (15.2μm) into this equation.

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In order to investigate the differences between male and female Taoyuan pigs in terms of carcass traits, chemical composition of muscles, fatty acid composition and iodine value of muscles and adipose tissues, 3 male and 3 female pigs were fattened from the body weight of 30kg up to approx. 90kg by feeding the meat production performance testing feed for pigs.
The carcass weight and yield of dressed carcass (in percentage) were higher in female pigs than in male pigs, and the carcass length (proximalis of symphysis pubis-atlas), loin length I (proximalis of symphysis pubis-proximalis of 1st vertebrae thoracis) and loin length II (distalis of last vertebrae lumbales-proximalis of 1st vertebrae thoracicae) were longer in male pigs than in female pigs. The ratios of the fore part and the hind part of the body were higher in male pigs than in female pigs, and that of the middle part of the body was higher in female pigs than in male pigs. As for the ratios of bone, fat and muscle in the composition of the hind parts, the ratios of bone and muscle were higher in male pigs than in female pigs, while that of fat was higher in female pigs than in male pigs. The mean thickness of back fat at the 3rd to 4th and the 11th to 12th thoracic vertebrae, and the 3rd to 4th lumbar vertebrae in female pigs were about twice as much as that of the male pigs. The loin eye area of male pigs was similar to that of female pigs.
The ranges of values of moisture, crude protein, and crude fat in muscle tissues (M. longissimus dorsi, M. biceps femoris and M. semimembranosus) were 73.8-75.9%, 20.9-22.9% and 1.3-1.9% for male pigs, and 73.6-75.0%, 20.5-22.2% and 2.2-3.6% for female pigs, respectively. The muscle tissues of female pigs tended to have higher proportion of crude fat, but less moisture and crude protein than those of male pigs.
In conjunction with the composition of fatty acids of the muscle tissues, the amounts of C18:2, C20:2, C20:3 and C20:4 and the ratio of C18:2/C18:0 were higher in male pigs, and that of C16:0, C18:1 and saturated fatty acids were higher in female pigs. With respect to the composition of fatty acids of the adipose tissues, the amounts of C18:2, C20:2 and C20:4 and the ratio of C18:2/C18:0 were higher in male pigs, and that of C16:0, C18:1 and saturated fatty acids were higher in female pigs. The iodine value and refractory index of back fat and kidney leaf fat tended to be higher in male pigs. From the results of fatty acid composition and properties of adipose tissues, it was conceived that the back fat and kidney leaf fat from male pigs were slightly softer than those from female pigs.

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Heat production at fasting was determined with 6 piglets each weighing 13-24kg (Middle White, male, at age over 35 days) using a HALDANE Type appatus for respiration test at an ambient temperature of 25°C. The results revealed a close negative correlation (r=-0.83) between the heat production at fasting (Y: kcal/kg^0.75. day) and the metabolic body size (x: kg^0.75), and a regression equation of Y=-2.14X+140.97 was obtained.
Earlier studies on heat production at fasting with pigs weighing more than 25kg revealed that the heat production by them at fasting decreased as they gained weight, but this decrease was almost negligible in consideration of energy metabolism. However, the ratio of the decrease in the heat production at fasting as found out in the present study using piglets weighing less than 25kg was too big to be neglected in the energy metabolism. It was therefore concluded that the heat production can not be neglected in energy metabolism when piglets weighing less than 25kg are to be used.

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The growth and digestion trials using fifteen pigs (Landrace) were conducted to evaluate the effects of feeding medium chain triglycerides (MCT) on growth performance and the digestibility of a basal diet (TDN70.4%, DCP12.9%) over the range 60 to 85kg weight. Backfat thickness and fatty acid composition were also measured. MCT or long chain triglycerides (LCT, soybean oil) were added to the control diet at the level of 8% and the pigs had ad libitum access to feed during the experimental periods for 28 days. The digestion trial was conducted in the second week of the experiment using the index method of chromium oxide.
Although the daily feed intake in the LCT and MCT groups tended to decrease, the digestible energy intake increased when compared with that in the control group. The daily weight gain in the LCT group tended to be higher than in the control group. But the daily weight gain in the MCT group was similar to that in the control group. As a result, feed efficiency (gain/feed) in the LCT group was significantly higher (p<0.05) than in the control group, and tended to be improved in the MCT group.
Additions of LCT and MCT had no effect on the digestibilities of nutrients in the basal diet. However, the digestibility of crude protein and that of the LCT were negatively correlated (p<0.05) with daily feed intake, but no relationship was found out between the digestibilities of the other nutrients or that of MCT and daily feed intake. The digestibilities of ether extract for the LCT and MCT used in this experiment could be estimated at 92.4 and 100.0%, respectively.
Backfat thickness in the LCT group tended to be thicker than in the control group, but no differences were found between the MCT and control groups. Means of backfat thickness of three positions (shoulder, midback and loin) for control, LCT, and MCT group were 30.1, 32.4 and 30.4mm, respectively.
Fatty acid profiles in outer and inner Backfat layer and leaf fat were similar to each other. As expected, the content of linoleic acid was significantly higher and stearic and oleic acid were lower in the LCT group when compared with those in the contol group. On the other hand, higher stearic acid and lower oleic acid were found in the MCT group. No difference in the content of linoleic acid was found between the MCT and control group.

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A number of extenders are employed at present for keeping semen, but the limit of its storage without losing its fertilizing capacity is still only 3 to 4 days. Difficulties still exist in reducing the considerable spermatozoal metabolism and in the control of bacterial growth in boar semen. The purpose of this study consists in 1) finding effective antibiotics on enteric bacteria, 2) evaluating the effects of bacteria on the survival of boar spermatozoa using 6 extenders (Polyzanon, BTS, Kiev, Zorlesco, Modena, and Butschwiler), and 3) selecting more useful extenders from those containing gentamicin and polymyxin B at various temperatures of 5, 10 and 15°C.
The following results were obtained.
1) Dibekacin (DKB), Amikacin (AMK), Gentamicin (GM) and Polymyxin B (PM-B) showed excellent antibacterial activities, whereas Streptmycin (SM) and Penicillin G (PCG) were not effective for 5 species of enteric bacteria (Escherichia coli, Serratia sp, Klebsiella sp, Enterobacter sp, and Citrobacter sp).
2) The survival of spermatozoa in the presence of Esherichia coli regardless of the types of extenders were remarkably affected, and the motility and normal acrosome of spermatozoa decreased into 0-30% and 15-24% in 3 days.
3) The effects of 6 extenders containing GM (100-150ug/ml) and PM-B (100-150units/ml) for the survival of spermatozoa were tested after 7 days'storage at 15, 10 and 5°C. Modena, Butschwiler and Zolresco proved to be more effective for preservation and the retained activity of spermatozoa was 75-80% on the average and its pH was 6.6-7.0 on the average. Polyzanon gave the poorest results among other extenders in sperm motility, and the activity of the sperm was 49-52% on the average.
The results with BTS and Kiev were between those of Modena, Butschwiler and Zolresco and those of Polyzanon, and the resulting sperm activity was 67-69% on the average. Hardly any bacteria were detected in the stored semem samples.
4) The effects of Modena and Butschwiler extenders containing GM and PM-B on the survival of spermatozoa were evaluated during 10-21 days' storage at 15 and 10°C. The motility and normal acrosomes of the spermatozoa were well maintained during 10 to 16 days' storage at 15 and 10°C. The activity of the spermatozoa was 67-78% on the average. Hardly any bacteria were detected in stored semen samples.
5) Sixteen sows were inseminated three times with 50-60ml of semen diluted with Modena and stored for 7 or 14 days at 10°C in the presence of GM (100-150ug/ml) and PM-B (100-150IU/ml). The farrowing rate for spermatozoa stored for 7 or 14 days were 100% and 57.1%, and the mean litter sizes were 10.2 and 12.8, respectively.
6) Eighteen semen samples diluted with Modena stored for 7 or 8 days at 10 and 5°C and for 14 or 15 days at 10°C containing GM and PM-B were inseminated in vitro. At 18 hours after the insemination, the fertilization rates of pig oocytes were 79.5% (136/171), 33.7% (57/169) and 68.1% (96/141), respectively.
The results of the present study showed that boar spermatozoa can be stored for 7 or 8 days at 10 or 15°C when Modena or Butschwiler was used as an extender containing GM (DKB or AMK) and PM-B.

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