Proteic diet and transcriptomic associated with immune response of infected sheep tissues by Haemonchus contortus

The aim of this work was to evaluate the effects of dietary protein on animal performance, diet digestibility, enteric methane production, nitrogen balance, hematological and biochemical profile, IgG detection, faecal egg counts (FEC), carcass yield and lymph node transcriptome for sheep artificially infected with Haemonchus contortus. Thirty-two Santa Ines lambs, randomly distributed in two diets (low content with 12% and high content with 19% of crude protein) and two different conditions (with and without H. contortus infection), leading to four treatments: high protein control (HC , n = 7), low protein control (LC, n = 7), high protein infected with H. contortus (HI, n = 9) and low protein infected with H. contortus (LI, n = 9), with sex effect tested. The experiment was carried out for 89 days. The artificial infection composed by 10,000 infectious larvae of H. contortus was taken 34 days after diets introduction beginning. After 42 days of infection, 24 animals were slaughtered to obtain tissues samples for abomasum histomorphometric analysis, also count and measurement of endoparasites present in abomasum. Transcriptomic analysis was performed using 19 samples of sheep\'s abomasal lymph node. For the results obtained, the HC lambs showed the highest consumption of dry matter and metabolic weight, and the HI presented the lowest values (P < 0.05). The treatments showed no difference in initial live weight, final live weight, average daily weight gain (ADG) and total weight gain (TG) (P > 0.05) during the post infection performance period. The CP digestibility was higher for HI animals compared to LI (P = 0.0007). The enteric methane production (g day-1) was higher for LI lambs (P < 0,05). Purine derivatives in urine were higher for control animals when compared to infected ones. The nitrogen consumed and retained was higher for high protein fed lambs (P < 0.05), and the HC lambs showed higher value for excreted nitrogen when compared to HI (P < 0.05). In the blood count, the LI treatment was the most affected with lower values compared to the others, mainly for packed cell volume, red blood cells, haemoglobin and platelet values (P < 0.05). In serum biochemistry parameters, the LI lambs were the most affected with lower values for total proteins and albumin (P < 0.05). The FEC was not different among treatments, but the average was higher for male than female sheep. There was no difference for the establishment of infection and count of endoparasites presents in the abomasum. For histomorphometric analysis of the abomasum, treatments with low protein showed thicker mucosa when compared to treatments with high protein (P < 0.05). Blood IgG values did not differ. A total of 95 and 75 genes were differently expressed between animals fed with high and low protein diet, and control animals and infected with H. contortus, respectively, as response to primary infection. Therefore, the high protein level of the diet promoted the immune system genes expression and allowed lambs resilience express during H. contortus infection. (AU)