Three popular breeds in Taiwan, i. e. L, W and D, were used in mating with 9 combinations by artificial insemination of mixed semen of two breeds. The results of 1251 pigs from 150 litters revealed that the cross of L and W was superior to others in litter size. The reciprocal cross of L and W for F₁ female in 74 litters indicated that L_??_×W_??_ was superior in litter size and survival rate. The 3-way and 4-way crossbred litters of 76 from LW and WL F₁ females were similar to each other. The line cross litters of Danish and American L were better than American L in pig weight and survival rate.
In purebred combination trial, pigs from L and D mating were superior than L and W mating in body weights. There were little difference in feed conversion ratio and carcass merits among the mating groups. Crossbred barrows from the reciprocal cross of L and W were similar to each other in gains and feed conversion ratio. WL crossbreds were a little bigger in loin eye areas and percentage of ham and tended to be leaner. The 3-way and 4-way crossbreds from LW and WL (female) showed no significant difference in each other in terms of gain and feed conversion ratio. Pigs from LW female had thinner backfat thickness and larger ham and boston butt. Pigs sired by D and H were superior than DH and HD in carcass merits. Pigs sired by D were superior in loin eyes, while those by H in loin percentage. Being superior to or better than H in other carcass merits, D was suggested to be a special sire line. Pigs from Danish and American L were superior in daily gains, backfat and loin eye areas.
These results suggested that the system of crossbreeding in commercial pig production in Taiwan be LW×D, taking advantage of reproductive performance of LW F₁ female and feed lot performance and carcass merits of D male.

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The effects of body weight of pigs on digestibility of feed were investigated in the present study with 53 Landrace barrows each weighing 24 up to 74kg, as the body weight is regarded as one of the factors for variability in digestibility of feed in pigs. The feed used was the formula feed generally adopted in Japan for performance test of pigs on meat production.
With the increase in the body weight, the digestibilities of crude protein, crude fat and crude fiber became clearly higher, showing significant correlation between them and the body weight (p<0.01), whereas those of dry matter and nitrogen-free extract (NFE) did not, showing no significant correlation (p>0.05).
In conjunction with the relationship between the nutritive values and body weight, it was revealed that both the digestible crude protein (DCP) and digestible energgy (DE) of feed increased with the increase in body weight, showing a significant correlation (p<0.01), whereas the total digestible nutrients (TDN) did not show any consistent trend with the body weight, showing no significant correlation (p>0.05). Of these feed constituents, the digestibility of crude fiber tended to be generally lower in pigs weighing less than 40kg.
From the above-mentioned results, it was conceived as important in performing the measurement of digestibility to select the objective pigs taking into full consideration the time point when the tested feed is to be actually given to the pigs.

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Lysine tends to be the first limiting amino acid in the feeds for pigs. A type of high-lysine naked barley (HLNB, Shikoku 79) has been recently developed by Shikoku National Agricultural Experiment Station. Chemical and amino acid analyses, an in-vitro digestion trial with intestinal fluid of pigs and an energy and nitrogen balance trial with growing pigs were conducted using corn as the control so as to determine the nutritive value of the HLNB. Six piglets each weighing approx. 30kg were used for the balance trial, which were individually housed in the metabolism cages and were fed daily 1200g of one of the three experimental diets. The three different types of feed were the HLNB alone, the corn alone and the mixture of corn with soybean meal. The experiment was conducted for two test cycles each comprising 4 preparatory days and 4 experiment days to collect feces and urine. 1) The HLNB contained 13.4% crude protein (CP), and 0.68% lysine. Its CP content was higher than that of naked barley of 11.2% demonstrated in the Japanese Standard Tables for feed components. The lysine content in the CP was 5.1%, which was substantially higher than that of corn of 2.8%. 2) In the in-vitro test, the digestible crude protein (DCP) and the digestible energy (DE) of the HLNB were 11.7% and 3.14kcal/g, respectively, which were higher than the counterparts of corn of 6.1% and 2.90kcal/g, respectively. 3) In the test on metabolism, the apparent digestibilities for CP of the HLNB diet and corn diet were 83.7% and 75.2%, respectively, the former being higher. The digestibilities of gross energy with the HLNB diet and corn diet were 86.4% and 84.6%, respectively, while the DE and metabolizable energy were 3.28kcal/g and 3.17kcal/g, respectively and 3.19kcal/g and 3.11kcal/g, respectively. The figures of the HLNB tended to be slightly higher than those of corn. The daily nitrogen retention of 10.1g for both the HLNB diet and corn-soybean meal diet were significantly higher than that of corn diet of 3.5g (p<0.05). 4) The results suggested that the HLNB is an excellent grain because of its higher lysine content and its higher utility as an energy source.

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In order to examine whether the correlation among the growth, meat production trais and halothane sensitivities will vary or not with feeding systems, phenotypic correlation among these traits of pigs were compared between the pigs reared under ad-libitum feeding and those under restricted feeding. Also, the variance on these traits was analyzed to investigate whether or not there are interactions between genotype and feeding conditions.
Ninety-four male Landrace piglets from the basic (23 litters) and the first (24 litters) generations of the closed herd in Miyagi Prefectural Livestock Experiment Station which were obtained by mating of 11 boars (of the basic and the first generations) with 2-6 sows were divided into two groups of the ad-libitum and the restricted feedings.
The analysis with the feeding methods and the boars used as the factors revealed that pigs reared under the ad-libitum feeding condition were superior in terms of mean daily weight gain, feed consumption and feed efficiency to those reared under the restricted feeding condition, but no significant difference was seen in backfat thickness and loin-eye area between the two feeding conditions. Nor was there any significant genotype feeding interaction noted in any of the traits. The restricted feeding group proved significantly closer correlation between the mean daily weight gain and the feed efficiency (r=-0.883) and between the mean daily weight gain and the feed consumption (r=-0.754) than the ad-libitum group (r=-0.452 and -0.426, respectively), whereas the correlation between the mean daily weight gain and the daily feed consumption was significantly closer in the ad-libitum feeding group (r=0.751) than in the restricted feeding group (r=0.504). Although the correlation between the mean daily weight gain and the backfat thickness was not significant, it was positive (r=0.074) under the ad-libitum feeding and negative (r=-0.149) under the restricted feeding.
In the first generation, the halothane positive pigs showed significantly less feed intake and better feed efficiency than the halothane negative pigs under the ad-libitum feeding, but these differences were not found under the restricted feeding condition. The above-mentioned results suggested that the effects of halogene sensitive genes on the traits were influenced by the difference in the feeding system. In the next generation, however, there were no differences in these traits between the halothane positive and the halothane negative pigs in either of the two feeding groups.

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Prostaglandin F2α, PMSG and HCG were administered to lactating sows, followed by injection of semen of varying boars in time course so as to see whether or not conception and parturition would take place. Of all the signs of estrus in the sows, colouring and swelling of vulva were distinct, whereas secretion of mucus and response to back pressure test were not so clearly developed.
The artificial insemination was found to be most successful when conducted at 18-24 hours after the HCG administration, and conception and pregnancy could be established in 58.3% of the lactating sows.
The litter sizes resulting from this treatment were found to be larger, but the body weights of the newborn piglets at birth were smaller. There was no adverse influence upon the growth of suckling piglets by the conception and pregnancy during lactation.
As it was possible to use the lactating sows repeatedly for this treatment method, it would possibly prove to be of greater utility if the conception rate is improved and if the timing to initiate this treatment could be made earlier.

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In order to establish the criteria for judging the quality of pork, the physico-chemical properties of muscles of longissimus thoracis from 83 swine carcasses were examined for the relationships among color shade (L, a and b), pH, water-holding capacity, spreadability and transmission value (TM-value).
The correlation coefficients among the reciprocal measurements were within the range of 0.3-0.8, showing high significance (p<0.01) in any measurements except the correlation between the meat color shade (a value) and other measurements.
Water-holding capacity was evaluated by the press method for fresh meat (WHC-PM) and the centrifugal method for salted ground meat with addition of sodium pyrophosphate (WHC-PP) or without its addition (WHC-NonPP).
The correlations of WHC-PP to such measurements as pH, WHC-NonPP and spreadability were positive, while those to L value and TM-value were negative. From the relation between the WHC-PP and other measurements, WHC-PP was classified into the group showing high and stable values ranging from 89 to 93% and into the group showing very broad range of values from 50 up to 93%.
On the basis of the relationship of the high and stable value group to the other measurements, the criteria for judgement of desirable meat quality turned out to be L value below 48, pH above 5.45, TM-value below 70%, WHC-PP above 72%, WHC-NonPP above 60% and spreadability above 20cm/g.

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