The behavior under single penning and group penning condition was compared to evaluate whether group penning was stressful on pigs. Four hogs weighed 81-87kg were introduced to exprimental pens from four different farms, and penned individually. Then the hogs were mixed and kept in a same pen for 7 days. Three behavior patterns, resting, eating and fighting were observed. Each ratio of three patterns of behavior became stable on the 4th day after the hogs mixed. On the 6th and 7th day each behavior of three patterns was compared between individual penning and group penning. Percentage of resting time a day of individual penning was slightly less than that of group penning (84% and around 86%, respectively). Percentage of eating time a day of individual penning was more than that of group penning (10% and 7%, respectively). The number of daily feed intake was smaller in group penning condition, and the length of each feed intake was longer in group penning (P<0.05). Those results show that group penning pigs rest more and eat more intensively. The group penning suggests no significant stress on pigs.

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A study was conducted to examine the response of ovaries in sows receiving gonadotropin (PMSG, hCG) during treatment with Altrenogest. Nineteen sows just after lactation were randomly assigned to the following four groups. Group 1: Altrenogest (-), PMSG (+) hCG (+); Groups 2 and 3: Altrenogest (+), PMSG (+), hCG (-); Group 4: Altrenogest (+), PMSG (+), hCG (+). The sows were subjected to laparoscopic examination on the fifth day after PMSG injection in Group 2, and between eight and ten days after PMSG injection in the other groups.
(1) All the sows in Group 1 exhibited estrus, whereas strong estrus was not recongnized in any of the sows in Groups 2, 3 and 4.
(2) Corpora lutea were induced in all the sows in Groups 1 and 4 (32.8±11.8, 24.0±7.4), and at the same time eggs were recovered in all the sows (23.8±13.7, 18.3±7.6). Three out of four sows in Group 2 had large follicles (21.7±6.5), although the sows in Group 3 had neither corpora lutea nor large follicles.
The sows injected with only PMSG during Altrenogest treatment did not ovulate even though they showed follicular growth. However, ovulation was induced during Altrenogest treatment in sows injected with PMSG and hCG. These results indicate that Altrenogest treatment does not interfere with the follicular ability to respond to exogenous gonadotropins (PMSG, hCG).

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