Based on the data collected from fifty nine local hog farms in 1989, the factors affecting marketing techniques were analyzed.
The following conclusions were obtained;
1) There is a close relationship between the mode of carcass weight and the ratio of “Excellent (Jo)”. It is necessary to market within a given range of the carcass weight.
2) It is necessary to accord with the mode of number of deliveries per year and ratio of “Excellent” by carcass weight.
3) It is necessary to improve the ratio of “Jo” as a basis to control the marketing weight and technical improvement.
4) The sales amount consists of the marketing conditions, the loss of carcass unit of price, the yield rate of carcass, and so on. These factors' analysis shows economic effect for the improvement of marketing techniques.
5) The control of marketing weight is the most important factor for the improvement of marketing techniques.

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The process of development of reproductive organs was investigated in 39 Beijing Black gilts from 60 to 210 days of age.
(1) The total weight of the vaginal vestibule, vagina, cervical canal and uterine body increased rapidly between 60 and 90 days of age and then increased slowly between 90 and 195-210 days of age. The total length of these organs increased rapidly between 60 and 75 days of age(P<0.05) and then increased gradually between 75 and 195-210 days of age. The weight and length of the uterine horn increased slowly between 90 and 165 days of age, and then increased markedly between 165 and 180 days of age (P<0.05, P<0.05).
(2) The weight of the ovaries increased between 60 and 90 days of age and then remained relatively constant until the appearance of corpora lutea. Morphological observations revealed that 33.3% of ovaries (2/6) had less than 4 protruding follicles on the surface at 60 days of age, and that 100% (6/6) had more than 5 protruding follicles at 90 days of age. The corpora lutea appeared in 71.4% (10/14) and 100% (8/8) of ovaries at 180 and 195-210 days age, respectively.
(3) Hisological observations revealed many primordial follicles, primary follicles, secondary follicles and vesicular follicles in all ovarian sections at 60 days of age. The diameter of the vesicular follicles increased from 60 to 90 days of age, and the number of vesicular follicles increased between 60 and 120 days of age. Many vesicular follicles were observed in ovarian sections at 120 days of age. There were no histological changes in ovaries from 120 days of age to puberty.
(4) These results indicate that Beijing Black gilts attain puberty between 165 and 180 days age.

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Enzyme immunoassay kits, Ovucheck Plasma/Serum Progesterone EIA Kit (EIA, Cambridge Veterinary Science Ltd) and Ovucheck Cow Side W (Cow Side W, Cambridge Veterinary Science Ltd), were applied to determination of pigs plasma progesterone (P) levels.
We tried to study the modification of EIA assay system for pig P measurement; ie., examined for best dilution methodes with castrated serum/plasma, boar/sow serum and normal saline as dilution solution with 2, 5 and 10 times dilution.
All solutions have no effect on the plasma P levels, but castrated serum/plasma and boar serum showed much more suitable for plasma dilution in 2 and 5 times dilution.
Porcine plasma P levels assyed by EIA with and without dilution showed significant positive correlation with those by RIA.
Cow Side W is used as a qualitative assay system, but it seems to be usable for a semiquantitative assay when using known value solution as standard. Plasma dilution with pigs serum have no effect on Cow Side W assay system too.
We demonstrated that modification in assay methods of commercial EIA kits developed for cow were applicable for the determination of pig plasma P levels.
Then these system would supply a suitable tool for the diagnosis of pregnancy and ovarian function in pigs.

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Correlation between the length of suckling after farrowing and effect of intrauterine infusion of 2% PVP-I solution 100ml in post-farrowing sows to the reproductive performance were observed in 2 commercial pig breeding farms (F and K) with different suckling periods.
A total of 142 sows of the 2 farms were randomly assigned to 2 groups, treated with PVP-I within 8 days postpartum and non-treated (control).
The suckling periods were 28.3±2.9 days (average±SD) (n=80) in F farm and 20.9±3.0 days (n=62) in K farm, the latter being significantly shorter (p<0.01). The interval from weaning to the first estrus were 6.3±3.4 days (n=39) in the treatment group of F farm, 6.9±4.4 days (n=41) in the control group of F farm, 5.5±2.0 days (n=30) in the treatment group of K farm and 8.5±5.2 days (n=32) in the control group of K farm, the difference between the two groups of K farm being significant (p<0.01). The litter size after treatment significantly increased in the treated group of K farm (p<0.01). However, no significant differences were obtained in the conception rate and farrowing rate among groups.
These results suggest that uterine infusion of PVP-I in early postparturient sows would be more effective on the reproductive performance in sows with a shorter suckling period.

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