Interpretive summary: Responses of pregnant ewes and young lambs to ovalbumin immunization, antiovalbumin antibody transfer to lambs, and temporal changes in antiovalbumin antibody
By: Surely Wallace
In a study published in Translational Animal Science in December 2017, researchers investigated immunity in lambs by measuring anti-ovalbumin antibody (OV-IgG). The antibody IgG is important in humoral immunity. Maternal IgG provides passive immunity to the newborn, lowers mortality, and provides protection from pathogens. Lambs have low IgG at birth and in the weeks after birth. Therefore, IgG from maternal colostrum is vital. The objective of this study was to determine how vaccinating ewe or lamb would affect lamb immunity, using ovalbumin (OV) as the reference protein, and quantifying blood OV-IgG levels in treated vs. untreated animals.
Three experiments were performed: (1) pregnant ewes received OV inoculation at 42 and 14 days prepartum and lambs were not inoculated, (2) lambs born to inoculated ewes were also inoculated with OV at birth and 15 days, and (3) lambs born to uninoculated (naïve) ewes were inoculated at birth and 15 days, or 28 and 42 days, with additional inoculation at weaning (159 days). Treatment groups were matched with controls receiving inoculation of sterile saline with adjuvant, but no OV. Different animals were used for each experiment. In all experiments, blood samples were collected at weekly intervals to quantify OV-IgG (via ELISA).
In the first experiment, OV with adjuvant was administered to the treatment group (10 ewes/group). Results indicated ewes given OV had increased OV-IgG in colostrum (1.47 odu vs. 0.98 odu), reflected also in their lambs (serum OV-IgG 1.48 odu vs. 0.69 odu in controls). In the second experiment (20 lambs/group), serum OV-IgG was lower in treated lambs compared to controls, until after day 15, when it increased. In the third experiment, lambs were separated into 2 control and 2 treatment groups (20 lambs/group), receiving inoculations of OV or saline at different intervals (birth and 15 days or 28 and 42 days). Serum OV-IgG increased in all treatment groups compared to controls (1.38 odu vs. 0.93 odu). An additional inoculation with OV at 159 days provided increased the protective effect, but only to previously inoculated lambs.
Overall, inoculation of pregnant ewes in the 6 weeks before lambing resulted in increased OV-IgG in their colostrum and their lambs compared to controls, supporting passive transfer of maternal IgG in colostrum. Administration of OV to lambs born to inoculated ewes at birth and 15 days decreased immunity during the two weeks after birth, compared to controls. The authors explained that the interaction between maternal IgG and IgG produced by the lamb in response to OV likely reduced total OV-IgG. In lambs born to naïve ewes, inoculation with OV at birth and 15 days, or 28 and 42 days followed by an additional inoculation at time of weaning provided increased protective antibodies compared to controls. The authors conclude that their study supports the importance of vaccinating ewes against pathogens in the weeks before lambing, and of colostrum to newborn lambs in IgG transfer for passive immunity. The authors do not recommend vaccinations of newborn lambs based on the results of their study.
To view the full article, "Responses of pregnant ewes and young lambs to ovalbumin immunization, antiovalbumin antibody transfer to lambs, and temporal changes in antiovalbumin antibody," visit Translational Animal Science.