Forty-two piglet free of antibcdy against pseudorabies virus (PrV) aged 7-10 days and each weightei 1 to 2kg were divided into six groups. Five groups of piglet were suhoutaneouslyincoilatlwith2,4, 8, l6and32mlofPrVpDrcineantiserumwitha titer of 1:1024 respectively. Each group contained 4 piglet except two groups receiving 4 and 32rn1 of antiserum having 12 piglet in each. Another group contained six piglet served as control. Four of each tested group and 2 of control group sepsratl into even numirer were challenged with lccal isolate of virulent PrV (1(0) TCDJ-50) via intanasally and contact infection respectively in & following day. The rest of 8 piglet in each group receiving 4 and 32 ml of antiserum were also challenged at one and two weeks poet incculation with antiserum. Pre-incxoulation and prechallenge serum were collectl. Clinical signs and rectal temperature were recorded daily. All dead piglet were suboted to virus isolation and brain lnstothology examination in order to prove their causative agent. Piglet receiving same amount of antiserum showed varied levels of serum neutralizing antibody titers in different individuals. In average, level of 1:4, 1:10,1:18, 1:3Oandl:70werefoundrespeotivelyinthepiglet receiving2,4, 8, l6and 32m1 of antiserum in the following day after inoculation, Two groups of 8 piglet in each receiving 4 and 32 mlof antiserum showed an average titer of 1:10 and 1:13 espeotively at one week after inoculation with antiserum. However, some piglet in these two groups died from severe diarrhea result! in insufficient numirer of pilget to keeptwoweeks longforthet Oneofeachin2, 4, and 8mlofantiseruminoculatl piglet died from PrV infection after intanasal challenge. Their serum antibody titers Wore challenge were 1:16,1:12 and 1:12. Although some othere piglet indifferent groups died after challenge. PrV infection was not deeot!. 4 piglet in each receiving 4 and 32 ml antiserum respectively and 1 control piglet challenged with virulent PrV 1 week poist incailation with antiserum survived normally except one receiving 4ml of antiserum having a titer of 1:8. All control piglet died from PrV infection.

Conclusively, piglet receiving hyerimmune serum showed good protection against PrV challenge even with a low titer of 1:3. However, prototion rate varier! from one piglet to another. The data did not dearly indicate that certain levels of serum antibody titer would poGitively pa-oat the piglet from challenge. But all piglet reciving 16m1 or more antiserum showed a titer higher than 1:30, and did not die after challenge. Piglet having antibody titer of 1:10 showed gototion against PrV at least longer one week.