The effect of carbetocin was evaluated in different doses on porcine myometrium with contractile pattern of uterus. Six healthy post-weaning sows, weighing between 200kg and 300kg, were given 25IU of oxytocin, 0.05mg, 0.10mg, 0.20mg, 0.40mg and 0.60mg of carbetocin on the first, third, fifth, seventh, ninth and eleventh day, respectively, by intramuscular administration.
The following results were obtained.
1. The amplitude of uterine internal pressure increased gradually after 25IU of oxytocin administration and the pressure reached 60mmHg in maximum. The highest frequency of uterine contraction (once per 0.98min.) was recognized soon after the administration. The frequency of contraction gradually decreased and returned to the value before the administration. The pattern of uterine contraction after carbetocin injection was similar to that after oxytocin injection. The decreased amplitude and heightened frequency of uterine contraction immediately after carbetocin administration gradually changed to the increased amplitude and low frequency and finally returned to the state before the injection by 2 to 5 hours after the administration.
2. The mean internal pressure of uterus was increased from 50.3 to 60.0mmHg by oxytocin injection. Thereafter the pressure decreased and returned to the value before the injection by about 2 hours after the injection. There was no significant difference in the mean uterine pressure between the group of carbetocine and oxytocin injection. The amplitude of the contraction of both groups increased temporarily soon after each administration then gradually decreased and tended to be smaller than that before each administration.
3. The mean wave length in changing pattern of uterine pressure in oxytocin group was shorter by half at 5 minutes after the injection. The length was slowly extended and returned to the value before the injection by 0.5 to 1 hour after the injection. There was significant shortening of the wave length in 0.20mg of carbetocin group compared with 25IU of oxytocin group at 0.5 to 1.5 hour after each injection. There was significant difference in wave length between the group treated with 25IU of oxytocin and 0.40mg of carbetocin at 1.5 hour after the injection. A significant difference in wave length was found also between the group treated with 25IU of oxytocin and 0.60mg of carbetocin at 1.5 hour after each injection.
4. The duration of the effect of 25IU oxytocin on uterine contraction was 57.6 minutes. On the group of carbetocin, the durations were 93.9 minutes for 0.05mg, 43.1 minutes for 0.10mg, 213.2 minutes for 0.20mg, 225.3 minutes for 0.40mg and 280.6 minutes for 0.60mg. They were 1.6 times, 0.8 times, 3.7 times, 3.9 times, 4.9 times longer than that of 25IU oxytocin.

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The birth time and body weight of each new born piglet were recorded on 93 parturitions observed in some middle scale pig farms during the period from September to November in 1990. The sows delivered successive two piglets with longer interval than 30 minutes were treated with one of the intramuscular injections of oxitocin (25IU), 0.4mg, 0.2mg or 0.1mg of carbetocin.
The following results were obtained.
1. The rate of treated sows was high and reached about 50%. All the sows treated with carbetocin (25IU) restarted to deliver by 30 minutes after the injection but four sows in ten treated with oxytocin required the second injection to restart the delivery.
2. On the sows treated with oxytocin, the mean intervals of delivery before and after the injection were 30.7 and 22.8 minutes, respectively. However the difference between these two intervals was not statistically significant. On the other hand, the mean delivery intervals were significantly reduced with 0.4mg, 0.2mg and 0.1mg of carbetocin from 48.8 to 19.7 minutes, 34.8 to 9.8 minutes and 34.0 to 11.2 minutes, respectively. The mean delivery intervals after the carbetocin treatments were significantly shorter than that after oxytocin treatment.
3. The rate of stillbirth per sow was highest (60%) for the oxytocin group and the rates decreased in order 0.4mg, 0.2mg of carbetocin group, untreated control and 0.1mg of carbetocin group. The rates of stillbirth per piglet for the groups showed similar tendency as that per sow.
4. The piglets of cabetocin group tended to show the larger daily body weight gain than those of oxytocin group during the period from 7 to 21 days of age.
5. The rate of raising at 7 and 21 days of age was 92.7% for untreated control and the rates decreased in order 0.2mg, 0.1mg of carbetocin group, oxytocin group and 0.4mg of carbetocin group.

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The effects of carbetocin (a long-acting oxytocin analogue) and oxytocin on contractile and electromyogram actions of porcine uterus were comparatively evaluated in vivo. Six healthy postweaning sows, weighing between 200kg and 300kg, were given 25IU of oxytocin and 0.2mg of carbetocin on the first and third day, respectively, by intramuscular administration.
These drugs induced appreciable increase in uterine contraction and action potential of metrium soon after their administration, and the frequency of uterine contraction was also increased.
The mean duration of the responding contraction and electromyogram were 213.2 minutes to carbetocin and 57.6 minutes to oxytocin. The duration of response to carbetocin proved to be approx. 3.7 times longer than that to oxytocin. No adverse effect was caused by the drugs administered upon the uterine contraction and electromyogram, but both drugs induced a transient increases of the amplitude of the contraction. The patterns of electromyogram were similar to those of uterine contractile pressure, and the electromyogram might be used for monitoring the uterine contraction.

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The purpose of a present paper is to estimate the genetic trends of growing performance and backfat thickness of the Duroc pigs raised in a farm which has been using a selection system based on the selection index method developed by the authors.
The performance data on age in days (DAY) and average backfat thickness (BF) at 105kg from 8, 859 Duroc pigs born between June 1985 to July 1990 were collected at a breeding farm in Gunma prefecture. Their parents of 324 pigs whose individual performance had not been recorded were added to the data set to evaluate the genetic relationship among the pigs. An animal model used for the analysis included the fixed effects of the birth-year and the sex and the random effects of the litter nested within the birth-year and the additive genetic value (breeding value) nested within the litter.
The mixed model equations (MME) were solved by SOR iteration called the indirect approach. The rounds of iteration in DAY and BF were 359 and 238, respectively. Annual genetic progress for DAY was -7.4 days from 1985 to 1990. No clear annual genetic change in BF was found.
In genetic improvement, it is essential to establish a solid selection program based on accurate estimates of breeding values and is important to realize an amount of genetic progress of a population in a time period.

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