This experiment was carried out to reexamine the effects of grouping of piglets on the concentration of plasma cortisol, total and differential leukocyte counts, the phagocytic functions of monocytes and the function of lymphocytes in vivo and in vitro. Twelve specific-pathogen-free piglets from 8 piglets/litter and 4 piglets/litter were used. At 63 days of age, 4 piglets of 8 piglets of a litter (Group A) were moved to the pen where 4 piglets of the other litter (Group B) were housed, and they were reared together for 13 days. The remaining 4 piglets of 8 piglets were not moved but reared for 13 days as control piglets. After grouping, all piglets of Group B attacked violently the piglets of Group A and bited their shoulders and ears for 2 hours. The concentrations of plasma cortisol at 2 hours after grouping were significantly higher as compared with those on 3rd day before grouping. After then, the plasma cortisol concentrations dropped to the normal and base-line levels at 24 hours after grouping. A significant difference in plasma cortisol concentration was not observed between Groups A and B. The numbers of total and differential leukocytes were almost same throughout the experiment. The proliferative responses of peripheral blood mononuclear cells induced with the mitogens such as phytohemagglutinin (PHA) and pokeweed mitogen in vitro were significantly decreased on 3rd day after grouping compared with those on 3rd day before grouping in Group B. The intradermal response to PHA in vivo and the Phagocytotic function of monocytes were significantly reduced in all piglets until 14 days after grouping. In control piglets, a slight increase of plasma cortisol was also found, and the suppression of intradermal response to PHA was observed for 13 days.
These data suggested that grouping puts piglets under stress and suppresses the functions of lymphocytes and monocytes at least for 13 days after grouping.

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Three rearing tests were conducted to determine the effectiveness and to identify the problems of applying wet/dry feeding to 113 postweaning pigs whose feed was changed, one week after the weaning, from the starter milk A to the starter milk B. The effects of wet/dry feeding for postweaning pigs were observed on growth, feed intake, water consumption and eating behavior. Five types of feeders were tested: Conventional ad libitum feeders for growing pigs with five feeding spaces (Control Section); ledge type wet/dry feeders with one feeding space and two feeding spaces (Wet Feeder Section 1-1 and 1-2 respectively); nose operated flap type wet/dry feeders with one feeding space and two feeding spaces (Wet Feeder Section 2-1 and 2-2 respectively). After the postweaning pigs for the test were introduced to each section and reared for 2 to 7 days for preliminary rearing (adapting period), they were supplied with the starter milk B for the first three weeks, then with formula feed for growing pigs for the next three weeks.
Effects of the feeder type on the average daily gain of the postweaning pigs were not significantly different across the sections, although the pigs in the wet feeder sections tended to show rather poor growth in 1-1, 2-1 and 2-2 in the adapting period, while they indicated the superior one through the experimental period, compared with those in the control section. The feed intake was increased in wet feeder sections from 5 to 8% compared with the control section. As for the feed conversion, no difference was shown between the sections. The water consumption varied according to the types of wet/dry feeders, showing the water saving effect of 3 to 31%. In the eating behavior, the total eating time of a day and the average eating time were significantly reduced in the wet feeding sections compared with the control section. The feeding trough usage rate, when the number of pigs per feeding space was 10 in the wet feeding sections, was significantly increased compared with the control section.

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One hundred and sixty-five Landrace×Large White gilts from 51 litters were randomly slaughtered between 152 and 260 days of age (liveweight of 82 to 137kg) to study the growth of genital organs before and after the attainment of puberty. They were housed in groups of six to ten per pen (about 1m² per pig) and had an ad libitum access to 70.1% total digestible nutrient and 12.7% digestible crude protein diet from approximately 25kg live weight to slaughter, which was almost the same rearing condition as fattening pigs in our experiment station. The rate of gilts already attained puberty was just twenty percent of all. The genital organs of these pigs were significantly larger (P<0.01) than those of prepubertal ones. In prepubertal gilts, the genital organs grew with advance of age (P<0.01), whereas those of postpubertal gilts grew according to increase in the body weight (P<0.05).

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The peptide (derived from cow milk casein) addition to milk replacer was conducted to research the effect of weight performance and blood condition of colostrum-free piglets by artificially nursing from birth to 1 week.
Eleven piglets from one litter were randomly divided into control group (n=5) and peptide added group (n=6). Both of the two group piglets were fed 60g of milk replacer (CP 28.7% as ADM) with or without addition of 3.7% peptide (CP 86.8% as ADM) per head per day through the experimental period. Blood samples were taken at birth, 12, 24, 72 hours and 1 week.
Serum protein concentration in both group was increased from birth to 72 hours, and then decreased slightly. Serum albumin concentration, which supplies amino acid to body tissue, was increased linerly in peptide added group as time progressed and significantly higher than that of control group at 24 and 72 hours after birth (P<0.05). The body weights of control and peptide added group were increased from 1.25kg and 1.24kg at birth to 1.82kg and 1.96kg at 1 week of age, respectively.
As a result, average daily gain (102g) of peptide added group was significantly Niger than that (81.4g) of control group (P<0.05).
In conclusion the results of this study indicate that peptide is efficiently utilized for body protein synthesis and improves weight performance of colostrum-free piglets by artificially nursing.

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