In this study we examined the estrous synchronization by administering prostaglandin F_2α (PGF_2α) in a miniature pig. In the first experiment, a single injection of PGF_2α was administered in the muscle and in the vestibule of vagina 7 days after ovulation. In the second experiment, as gonadotropin (GTH), equine chorionic gonadotropin (eCG) and PG600 (contained a low does of eCG 400IU and hCG 200IU) were injected into the muscle on day3 (early luteal phase) and then PGF_α were injected into the vestibule of the vagina on day7. Plasma progesterone concentration did not change after a single injection of PGF_2α. However, a P concentration decreased rapidly after PGF_2α was administered twice. It appeared that the shortening of the estrous cycle (16.3±1.5 days) resulted after a combined administration of GTH and PGF_2α in three of the six animals. This suggests that the synchronization of the estrous cycle in a miniature pig can result from the combined administration of both GTH and PGF_2α.

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We studied the effects of buckwheat-flour milling byproduct feeding on the growth, carcass characteristics, fatty acid composition in lipid tissues, and amino acid composition in the longissimus muscle in pigs. In the digestion experiment, no significant differences were observed in the digestibility of dry matter and organic matter as well as in total digestible nutrition (TDN) between the control group and the experimental group fed 30% buckwheat-flour milling byproduct (BMB) and 100% BMB.
The digestibility of BMB feed was significantly higher than that of the control group (P<0.05), whereas the digestibility of crude protein did not show any significant difference between the control and the 30% BMB diet. Moreover, a significant difference was observed between the control, 30% BMB diet and BMB (P<0.05) regarding the digestibility of crude fat. In the feeding experiment, the growing stage period of fattening pigs in the experimental group was longer than that in the control group (P<0.05). However, no significantly differences were observed between the 2 groups in daily weight gain, food conversion rate, food intake during the growing stage, finishing stage, and total stage, and days required to complete the finishing stage and total stage. As for carcass performance, back fat thickness in both the shoulder and loin was significantly thinner in the experimental group than that in the control group (P<0.05). As for the fatty acid composition of lipid tissues, intermuscular fat of C14:0 and C16:0 was significantly higher in the experimental group than in the control group (P<0.05). In contrast, the intermuscular fat of C18:1 was significantly lower in the experimental group than the control group (P<0.05). As for the free amino acid composition of the loin, γ-amino butyric acid (GABA) was significantly lower in the experimental group than in the control group (P<0.05). However, no significant differences were seen between the groups for the other amino acids.

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PSE (pale, soft and exudative)-like muscle was prepared from ordinary pork under conditions of incubation and low pH. For assessment of PSE quality of the meat, transmission (TM) value of the extracted sarcoplasmic protein was measured. Water holding capacity (WHC), sausage cooking loss (CL) and texture were then determined for comparison with the control sample prepared without incubation or reduced pH. The color of the cooked sample cured with nitrite was examined for possible relation with PSE. With decrease in pH for PSE-simulation, TM value was noted to increase, thus indicating denaturation of the sarcoplasmic protein to take place. WHC (M/T value with filter-paper method) decreased gradually with PSE quality. A negative relationship was noted between WHC and CL. WHC and CL of the PSE-like meat were less than those of the control sample. The Hunter value for color appeared to enhance as L- and b-, and decrease as a-value. L*a* and b* showed essentially the same behavior. Meat sample color was a pale weak red. With increase in PSE, reduction in texture quality became apparent. The sausage under consideration would thus have little market.

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[in Japanese]

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