Mucosa obtained from the cecum of healthy horses and incubated in vitro with 0.1 mM cycloleucine could accumulate this amino acid against an apparent concentration gradient after 60 and 120 minutes. Accumulation by the serosal (antiluminal) surface of the tissue was 3 times greater than accumulation by the mucosal (luminal) surface after 120 minutes (P < 0.001). Cycloleucine accumulation was significantly reduced by Na deprivation after 60 minutes (P < 0.05) and 120 minutes (P < 0.01) and by anoxic conditions after 120 minutes (P < 0.05). Transmucosal flux from mucosal to serosal surface of the tissue was significantly (P < 0.05) greater than the opposing flux, but both unidirectional fluxes were small and were largely attributed to passive processes. It was concluded that the most avid transport system for cycloleucine was on the serosal surface of the horse's cecal mucosa, and an active transport system was not evident on the mucosal surface. An active transport system for amino acids on the serosal surface could be explained by the need for crypt cells, the predominant epithelial cell type in the cecum, to obtain nutrients from blood, rather than from the intestinal lumen.

Ten colostrum-deprived calves were assigned to 1 of 2 treatment groups (5 calves/group), and fed colostrum that had either low (naturally infected cows) or high (immunized cows) antibody titers to bovine coronavirus (BCV). All calves were inoculated orally and intranasally with virulent BCV when they were 24 to 48 hours old and challenge exposed 21 days later. Blood, feces, nasal secretions, tears, saliva, and bronchoalveolar lavage (BAL) fluids were collected weekly from each calf for 5 weeks after inoculation. The titers to whole BCV or the relative amounts of isotype-specific antibodies to BCV structural proteins were evaluated in these samples by ELISA or immunoblotting, respectively. Both pools of colostrum contained primarily IgG1, IgG2, and IgA antibodies to the E2 and E3 BCV proteins. Calves fed the high-titer colostrum had correspondingly higher amounts of passive IgG1 and IgA antibodies to whole BCV and to the E2 and E3 BCV proteins in serum, feces, and BAL fluid at postinoculation week 1 than those calves fed low-titer colostrum. Active IgG1, IgA and IgM antibody responses in serum and active IgA and IgM antibody responses in most mucosal secretions to whole BCV and to the E2 and E3 proteins were lower or delayed in calves fed high-titer colostrum, compared with responses in calves fed low-titer colostrum. In contrast, increased responses to the BCV N protein were observed in all samples (except in serum and BAL fluid) in the calves fed high-titer colostrum, compared with calves fed low-titer colostrum. Upon challenge exposure, responses to E2 and E3 BCV proteins in serum and BAL fluid were lower in the group fed high-titer colostrum, compared with those in the group fed low-titer colostrum. Our findings indicate that the level of passive immunity in calves at the time of BCV inoculation can influence the development of active antibody responses in serum, feces, and mucosal secretions to whole BCV and to some BCV proteins individually.

The ability of pseudorabies virus (PRV) to infect and establish latency in pigs with passively acquired (maternal) antibody for PRV was tested by exposing such pigs to the virus and subsequently attempting to reactivate latent virus by administering large doses of dexamethasone. Pigs of each of 4 litters that had nursed gilts with relatively high (512, gilts 1 and 2), moderate (32, gilt 3), and no (less than 2, gilt 4) serum titers of virus-neutralizing (VN) antibodies for PRV were allotted to 3 treatment groups (A, B, C) when they were 2 weeks old. Group-A pigs were separated from littermates and dam and thereafter kept in isolation; group-B pigs were experimentally exposed oronasally to PRV and 1 hour later returned to their dam; group-C pigs were kept with their dam and potentially exposed to PRV by contact with littermates of group B. Sera obtained from pigs at selected intervals until they were 17 weeks old were tested for VN activity and for precipitating activity for radiolabeled viral proteins. All group-A pigs remained clinically normal throughout the experiment. Depending on the initial amount of passively acquired antibody, little or no serum VN or precipitating activity remained by the time these pigs were 17 weeks old. Group-B and -C pigs, with relatively high amounts of passively acquired antibody when exposed to PRV, also remained clinically normal. However, most became latently infected as subsequently evidenced by either dexamethasone-induced or noninduced virus reactivation. Noninduced reactivation may have been initiated by weaning the pigs when they were about 8 weeks old. Group-B and -C pigs with no or moderate amounts of passively acquired antibody when exposed to PRV, had severe clinical signs. These pigs either died or recovered but remained stunted in growth. Virus was reactivated in all of the recovered pigs by treatment with dexamethasone. Quantitative and qualitative changes in serum precipitating activity, especially for viral proteins of relatively low molecular weight (less than 46,000), were a more consistent indication of virus reactivation than were either increased VN titers or virus isolation. Results with litters 1 and 2 clearly indicate that latent infection of young pigs with highly virulent PRV can develop in the absence of clinical signs.

Two experiments were carried out to evaluate the efficacy of the administration of active dry yeast and/or lactobacillus preparation (AVI-BAC), either before or after the infection with antibiotic resistant field strain of Escherichia coli O127 (E. coli O127) in controlling the severity of infection in quail chicks. The quail chicks of the different experimental groups were infected orally for two successive days with 3x107 CFU of E. coli O-127 as an individual dose. The used field strain proved to be highly pathogenic for quails. Probiotics were supplemented in the drinking water for the different treatment groups at a dose level of 0.5 gm/L. The results revealed that the inclusion of lactobacilli or active dry yeast before E. coli infection has been highly effective in reducing mortality rate, organ invasion and the number of E. coli positive quail chicks. In addition, it decreased the severity of macroscopic and microscopic lesions in different organs in the probiotic treated groups as compared to the infected controls. Lactobacilli preparations were more efficient in controlling the severity of the infection. On the other hand, the administration of yeast and /or lactobacilli after inducing E. coli infection reduced the mortality rate and the severity of lesion score in different organs but probiotics failed to protect quail chicks against the infection. It has been proved that the two probiotics have synergistic effect in controlling collibacillosis in quails.

In contrast to the net absorption of Na and Cl ions observed in vivo, porcine small intestine had a net secretion of these ions in vitro. These discrepancies between in vivo and in vitro results have led to difficulties in interpretation of studies investigating mechanisms of intestinal secretion and diarrhea in this species. To examine the influence of endogenous prostanoids on ion transport in neonatal porcine ileum in vitro, tissues were prepared and studied in indomethacin. Net absorption of Na, reversal of net Cl secretion to net absorption, and decreased short circuit current were observed. Conversely, addition of prostaglandins to indomethacin-treated tissues reversed these effects and reestablished conditions similar to those observed in control tissues. Control tissue was essentially refractory to the effects of exogenous prostaglandins. Results indicate that under in vitro conditions, ion transport in neonatal porcine ileum is tightly regulated by endogenous prostanoids that abolish the neutral NaCl absorptive mechanism and elicit electrogenic Cl secretion. However, concentrations of these prostanoids may have been artificially high as a result of tissue preparation for in vitro study.