Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2018
Publication Date: 5/1/2018
Citation: Miska, K.B., Fetterer, R.H. 2018. The effect of Eimeria maxima infection on the expression of amino acid and sugar transporters aminopeptidase, as well as the di- and tri-peptide transporter PepT1, is not solely due to decreased feed intake. Poultry Science. 97(5):1712-1721.
Interpretive Summary: Coccidiosis is responsible for causing large economic losses to the poultry industry worldwide. This disease is caused by a single celled parasite Eimeria. Several species of Eimeria are responsible for causing coccidiosis. Eimeria infect gut epithelial cells that line the inside of the intestine and different species of Eimeria are partial to infection of specific portions of the gut. At the height of infection the parasites cause damage to the intestine, resulting in loss of appetite, decrease in weight gain, increase in feed conversion, diarrhea, and sometimes death. The goal of the present study was to determine how decreased feed intake in combination with Eimeria infection affect the expression of molecules involved with breakdown and uptake of nutrients like proteins and sugars. Since Eimeria infection negatively affects weight gain it is likely that it also interferes with nutrient uptake and that decreased feed intake associated with coccidiosis plays a component in the changes in expression of molecules involved in nutrient uptake and processing. The results indicate that while decrease in feed decreases weight gain, increases feed conversion, and changes the expression of nutrient transporter, the changes are different than the ones observed in Eimeria infected birds. The changes in growth parameters of birds on feed restriction are less severe than seen in Eimeria infected birds and they recover more rapidly than infected birds. Most of the changes in expression are observed in molecules that are located at the brush border of the gut epithelium, or the side of which faces the inside of the gut. Eimeria infection predominantly results in decrease in expression of nutrient transporters while decrease in feed causes an increase in expression of the same molecules. Therefore, while decrease in feed intake does play in decrease in weight gain, feed conversion, as well as nutrient transporter expression it doe not account for the magnitude of decrease in weight gain and increase in feed conversion, and results in different change in nutrient transporter expression.
Technical Abstract: Coccidiosis caused by Eimeria in poultry is endemic to poultry operations and results in decreased feed intake, diarrhea, and decreased weight gain. The goal was to determine the effect infection Eimeria maxima on the expression of genes that encode peptide and amino acid transporters (AATs), and also to determine whether decreased feed intake contributes to the change in gene expression by including a pair fed group of broilers. Three groups of male Ross broilers: 1. not infected, 2. infected, and 3. not infected pair fed group were used. Chicks were infected with 1,000 oocysts of E. maxima at 21 days of age. Feed consumption was obtained daily, and at days 0, 3, 5, 7, 10 and 14 post-infection (PI) six birds were euthanized, and a portion of the ileum was removed for qRT-PCR. Infected birds had significantly decreased feed consumption between days 6-9 PI. At day 7 PI infected birds had a 45% reduction in weight gain, and pair fed birds had a 32% reduction in weight gain. The feed conversion ratio at day 7 PI of infected birds was 2.2 while that of pair fed birds was 1.7, compared to 1.5 in uninfected birds. Growth parameters were more affected in infected birds than in pair fed birds. By measuring expression levels of nutrient uptake and processing genes via qRT-PCR it was determined that genes encoding proteins located at the brush border of the gut epithelium was most affected by infection as well as change in feed intake. The expression of AATs: BOAT, b0,+AT, EAAT3, PepT1 in infected birds decreased sharply at the height of infection, however in birds that were pair fed an increase in expression of bo,+AT,and PepT1 was observed, and little change was seen in expression of BoAT and EAAT3. In summary, the changes in expression of digestive enzymes and nutrient transporters are distinct between coccidia infected birds compared to healthy pair fed birds.