The Effect of In Ovo Oocyst or Sporocyst Inoculation on Response to Subsequent Coccidial Challenge

Abstract

A trial was conducted to investigate the effects of in ovo Eimeria maxima inoculation on response to subsequent posthatch challenge with E. maxima. The in ovo treatments were arranged in a 4 x 2 factorial with four in ovo inoculation sites (air cell, amnion, yolk sac, and allantois) and two parasite forms (oocyst and sporocyst). Four control treatments included an uninoculated (naive) unchallenged group, a naive challenged group, and two posthatch inoculated challenged groups. Chicks were challenged by crop intubation with 50,000 sporulated E. maxima oocysts 10 d posthatch. On Day 8 postchallenge, feed intake was determined and birds were weighed and lesions scored. During the brooding period, oocysts were isolated from the fecal material of chicks receiving in ovo administration of sporocysts in the amnion and sporocysts or oocysts in the yolk sac. Posthatch inoculated chicks had gain and feed:gain ratios similar to those of naive unchallenged chicks. Gain, feed:gain ratio, lesion scores, and oocyst shedding of chicks inoculated in ovo were similar to those of naive, challenged chicks. Although there was some indication that parasites introduced in ovo may complete their life-cycle within the developing chick, this experiment provided no evidence that in ovo administration of either E. maxima oocysts or sporocysts will protect birds from subsequent coccidial challenge. Contrarily, inoculating chicks on day of hatch with a single oral dose of E. maxima oocysts provided significant protection against subsequent coccidial challenge.