The objective of the current study is to evaluate the impact of induced starvation on horn fly susceptibility to permethrin and general reproduction using filter paper and manure bioassays, respectively. Incorporating push-pull systems for horn fly control has recently gained much attention for use in managing this pest. However, the consequences of temporary starvation associated with the relocation of horn flies from one host to another have yet to be fully explored. Susceptible (SS) and permethrin resistant (PR) horn flies were randomly allocated to one of four treatment groups: 1- blood fed, 2- partially starved (4hr), 3- moderately starved (8hr), and 4- severely starved (12hr). Permethrin resistant flies were 1,227 times more (P < 0.05) tolerant to permethrin in comparison to SS flies. Furthermore, SS blood fed flies were 1.18, 1.89, and 3.12 times more tolerant to permethrin than SS flies starved for 4, 8, and 12 hours, respectively. Egg hatching rates decreased (P < 0.04) for 8hr and 12hr starved flies in comparison to blood fed flies. Larval development, as measured through manure bioassays was lower (P = 0.02) in severely starved flies in comparison to blood fed flies. Pupae sizes were unaffected (P = 0.58) by starvation and fly strain. These results indicate that susceptibility to permethrin increases as time without a blood meal increases and furthermore, offspring success is reduced specifically through egg viability. Findings from this work will help further expand current integrated pest management options for animal producers by increasing our understanding and implementation of push-pull strategies in animal production systems.

Increased salivary cortisol in cattle may be detrimental to rumen bacterial diversity. Effects of transportation and diet before transportation on plasma and salivary cortisol and on rumen conditions of 20 ruminal-cannulated heifers (346 ± 16 kg BW) were evaluated. Heifers were fed ad libitum 40% Sorghum Sudan grass hay and 60% commercial pellet (64% TDN, 12.4% CP, DM basis) for 13 d before study initiation. Heifers were randomly assigned to a 2 × 2 factorial arrangement of 8-h transportation (TR) vs. no transportation (NT) and 100% Sorghum Sudan grass hay (HAY) vs. 30% hay and 70% pellets (H+P) fed ad libitum for 3 d before transportation. All groups were fasted during the 8-h transit period. Upon feedlot arrival at 8 h, cattle were fasted an additional 4 h. At 12 h, cattle were fed 30% wheat hay and 70% commercial feed (69% TDN, 16.6% CP, DM basis). Blood and ruminal fluid were sampled at 0, 8, 12, 24, 28 and 72 h. No diet × transport interactions were observed for any variable. Plasma cortisol was decreased for HAY vs. H+P heifers at 72 h (P < 0.05, diet × hour). Rumen pH and total volatile fatty acid concentrations did not differ between groups. Molar percentages of acetate increased, molar percentages of propionate decreased, and acetate-to-propionate ratios increased at 0 and 12 h for HAY compared to H+P (P < 0.05, diet × hour). At 0 h, molar percentages of butyrate were less for HAY vs. H+P (P < 0.05, diet × hour). Bacterial phyla richness was decreased for NT/HAY compared to NT/H+P and was increased for TR/HAY compared to TR/H+P heifers (P < 0.05, diet × transport). Proteobacteria relative abundances were less at 0 h for heifers fed HAY vs H+P (P < 0.05, diet × hour). Genera evenness was increased at 8 h for TR compared to NT cattle (P < 0.05, transport × hour). Genera Shannon-wiener indices were greater at 0 and 8 h for cattle consuming HAY compared to H+P (P < 0.05, diet × hour). Genera richness was increased at 0 h for cattle fed HAY compared to H+P (P < 0.05, diet × hour). Prevotella relative abundances were less for cattle fed HAY compared to H+P at 0 and 8 h (P < 0.05, diet × hour). In summary, due to negligible response to transportation, salivary cortisol effect on bacteria population and diversity were presumably minimal.

This study evaluated the effects of preconditioning diet management and transportation on performance, rumen pH, and rectal temperature of feedlot receiving cattle. Twenty rumen cannulated angus heifers (758 ± 50.7 lb) were used in a complete randomized design with a 2×2 factorial arrangement of treatments with repeated measures related to time of transportation. One factor was the preconditioning diet management consisting on offering a preconditioning diet for the 30 days prior to transportation (diet), or offer the same diet for 27 days and the last 3 days prior to transportation received only hay (hay). The second factor was transportation and consisted of transporting or not transporting the heifers for 12 hours. All heifers received a commercial feedlot receiving diet at arrival and for 14 days. Measurements were obtained at 92 and 20 h before transportation, at 0 (right before loading for transportation), 6, 12, 78, 76, 172, 340 h after transportation. All the sampling points but 0, 6 and 12 h were 4 h after feeding or around peak of fermentation. Performance, rectal temperature and ruminal pH were analyzed using MIXED procedures. Rectal temperature, rumen pH, intake presented diet×time interactions. Rectal temperature was greater (P = 0.02) for hay at time 0 and no effects at other times (P > 0.10). Rumen pH was greater (P = 0.01) at 20 h prior and at 76 h after, and lower (P = 0.05) at 340 h after transportation for hay than diet and no effects at the rest of the time points. Intake was lower (P ≤ 0.05) at 20 h prior and 76 and 172 h after transportation for hay than for diet. In conclusion, changing the preconditioning diet to hay only prior transportation had detrimental effects on rumen fermentation characteristics and intake of the receiving diet. Such dietary changes might have switched the rumen bacterial population to more cellulolytic bacteria. Findings of this experiment suggest the needs of further research that assesses the effect of manipulating the diet right before transportation.