الملخص الإنجليزي
ABSTRACT
There are three major breeds of goats in Oman, namely Jabal Akhdar (JA), Batina (BT) and Dhofari (DF). Previous studies have shown breed differences in mature body weight, carcass yield, meat quality, susceptibility to stress, susceptibility to cobalt deficiency and differences in serological responses to foot and mouth disease (FMD) vaccine. Infectious diseases are a limiting factor in goat production. This study is, therefore an attempt to compare the immunological responses of the three breeds by comparing the oxidative respiratory burst occurring during phagocytosis and the mitogenic responses of their mononuclear cells.
Five four months old goats from each breed were selected randomly for this study. These animals were kept at the Agricultural Experiments Station at Sultan Qaboos University, and were fed general ruminant concentrate and chopped Rhodesgrass hay. Blood samples for chemiluminescence (CL) and mitogenesis assays were collected monthly from the jugular vein in 7 ml heparin vacutainer tubes. Enriched preparations of polymorphonuclear and mononuclear leukocytes were prepared by density centrifugation. The oxidative respiratory burst of polymorphonuclear leukocytes (PMNS) was measured using a CL assay. Reaction mixtures contained 100 ul PMNs (5 X10R/ ml), 100 ul opsonized zymosan, and 100 ul luminol. CL response was measured as mean relative light units (RLU), and was expressed as average counts per minute, peak CL response, and area under the curve (AUC). The mitogenic responses of mononuclear leukocytes to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) mitogens were assayed using a WST-8 assay and read spectrophotometrically at 450 nm
Although JA goats exhibited higher levels of CL in four (April, May, July and September of the six months (April-October), these differences were not statistically different. However there was a seasonal variation in the CL response of PMNs, where the CL response was significantly higher in May, June and July (hot months) than that in April, September and October (cooler months). Moreover, there was no significant breed difference in the mitogenic response of B and T lymphocytes to PHA or PWM.
The seasonal variation in CL response may be a partial explanation why there is a higher incidence of a number of infectious diseases during the cooler months of the year..
