Wagdy ElAshmawy

Stable flies (Stomoxys calcitrans) are blood-sucking insects commonly associated with cattle production systems worldwide and are known to cause severe irritation to cattle due to painful bites. Cattle react to biting stable flies with an aggregating behavior known as bunching. Bunching behavior reduces grazing or feed consumption and thus reduces cattle productivity and welfare. Cattle's fly-repelling behaviors include foot stomping, head tossing, tail switching and skin twitching. A longitudinal study was conducted in 2017 on 20 California dairies (average lactating herd size = 2,466 (SE±28.392)) during the stable fly season from April to July. The study objectives were to estimate the association between environmental factors and dairy characteristics including facility design, feed and manure management, total mixed ration (TMR) components fed to cattle, and operational pest management procedures and the outcome stable fly activity on California dairies. Stable fly activity was measured by counting stable flies on cow forelimbs (leg count) and on Alsynite traps (trap count) over the 13-week study period. Weekly leg counts were performed for cattle in lactating cow pens (31 pens from 10 study dairies) with counts made during the morning (AM) and again during the afternoon (PM). Trap counts were performed on all 20 study dairies. Data were analyzed using linear mixed models which revealed temporal variation in the average leg and trap counts with stable fly activity increasing from May to June and then decreasing to the lowest activity in July. Leg counts were higher during the afternoon compared to morning. Ambient temperatures ≤30⁰C and relative humidity (RH) measurements <50% were associated with higher leg and trap counts. Traps located at the periphery of study dairies had higher stable fly counts compared to traps located in the interior of the dairy. Cow pens with trees on the periphery had higher leg counts in comparison to pens away from trees. Specific TMR components were associated with both leg and trap counts. Dairies feeding by-products including almond hulls, wet distillers' grain, fruits, and vegetables had higher trap counts compared to dairies that did not feed these ingredients. At the pen level, pens with rations that contained straw had lower average leg counts compared to pens fed with rations that did not contain straw. A similar association was observed for pens with rations that contained wheat silage when ambient temperatures were ≤30⁰C. In contrast, pens with water added to the TMR while the RH was ≥50% had higher average leg counts compared to pens without water added to the TMR. Dairies that applied insecticides for fly control to their entire facility had lower trap counts compared to dairies that did not apply insecticides. Stable fly activity measured on California dairies using leg and trap counts varied according to the month, environmental factors, pen surroundings, trap location, TMR components, and insecticide use.

In this study serum samples were collected from 4 different groups of cattle, Group I (non-vaccinated Brucella infected group), Group II (Vaccinated Brucella infected group), Group III (Non-vaccinated Brucella free group) and Group IV (vaccinated Brucella free group). These samples were subjected to the different serological tests including Rose Bengal plate antigen test, Tube Agglutination test, Rivanol test, Indirect Enzyme Linked Immunosorbent Assay and Competitive Enzyme Linked Immunosorbent Assay. Statistical analysis of the obtained results in different cattle groups was carried out using Latent Class Analysis (Lem model). The prevalence of brucellosis was 6.4%, the sensitivity of RBPT was 96.1% while its specificity was 99.3%, the sensitivity of Rivanol test was 85% while its specificity was 100%, the sensitivity of Indirect Enzyme Linked Immunosorbent assay was 100% while its specificity was 98.3 % and the sensitivity of Competitive Enzyme Linked Immunosorbent assay was 97.1% while its specificity was 100%. The results proved that, the most sensitive test was Indirect Enzyme Linked Immunosorbent assay while the most specific test was Competitive Enzyme Linked Immunosorbent assay. This study therefore, recommends the use of Indirect Enzyme Linked Immunosorbent assay as a screening test and Competitive Enzyme Linked Immunosorbent assay as a confirmatory test. Bacteriological examination was carried out on supramammary lymph nodes and spleen of some slaughtered seropositive cattle, the rate of isolation was 25% from non-vaccinated infected group and 10% from vaccinated infected group. Brucella melitensis biovar3 was recovered only from supramammary lymph nodes.