ANIMAL MODELS FOR THE STUDY OF LEISHMANIASIS IMMUNOLOGY

Leishmaniasis remains a major public health problem worldwide and is classified as Category I by the TDR/WHO, mainly due to the absence of control. Many experimental models like rodents, dogs and monkeys have been developed, each with specific features, in order to characterize the immune response to Leishmania species, but none reproduces the pathology observed in human disease. Conflicting data may arise in part because different parasite strains or species are being examined, different tissue targets (mice footpad, ear, or base of tail) are being infected, and different numbers (“low” 1×102 and “high” 1×106) of metacyclic promastigotes have been inoculated. Recently, new approaches have been proposed to provide more meaningful data regarding the host response and pathogenesis that parallels human disease. The use of sand fly saliva and low numbers of parasites in experimental infections has led to mimic natural transmission and find new molecules and immune mechanisms which should be considered when designing vaccines and control strategies. Moreover, the use of wild rodents as experimental models has been proposed as a good alternative for studying the host-pathogen relationships and for testing candidate vaccines. To date, using natural reservoirs to study Leishmania infection has been challenging because immunologic reagents for use in wild rodents are lacking. This review discusses the principal immunological findings against Leishmania infection in different animal models highlighting the importance of using experimental conditions similar to natural transmission and reservoir species as experimental models to study the immunopathology of the disease

Influence of supplemental tocopherol level (0, 250 and 500 IU RRR-α-tocopherol/d/steer) and injectable retinol form (retinyl propionate vs retinyl palmitate) on growth performance, carcass characteristics and plasma concentration in calf-fed Holstein steers

The influence of supplemental tocopherol level (0, 250 and 500 IU RRR-α-tocopherol/d/steer) and injectable retinol form (retinyl propionate vs retinyl palmitate) on growth performance, carcass characteristics and plasma tocopherol and retinol concentrations were evaluated in 108 Holstein steers fed a steam flaked corn-based finishing diet during 314-d feeding period. There were no treatment interactions (P > 0.10). During the initial 112-d period, dietary supplemental tocopherol tended to increase ADG (linear, P = 0.07) and DMI (linear, P = 0.06). Overall 314-d ADG, DMI, gain efficiency and carcass characteristics were not affected (P > 0.10) by dietary supplemental tocopherol. Overall DMI tended to be greater (3%, P ≤ 0.10) for steers injected with retinyl palmitate vs retinyl propionate. It is concluded that vitamin E supplementation above basal requirements may enhance growth performance during the initial 112-d phase. However, the overall effect on growth performance and carcass characteristics was not appreciable. Injectable retinol ester form did not affect overall ADG, gain efficiency, or dietary NE. Based on plasma retinol concentrations, the bioavailability of retinyl palmitate is greater than that of retinyl propionate

Influence of mixing supplements (dry or liquid) with monensin or soluble protein on the feeding value of finishing diets for feedlot cattle

The influence of supplement form (dry vs. liquid) on the feeding value of diets for feedlot cattle was evaluated. Treatments were: (1) dry supplement (DS); (2) liquid supplement (LS, all supplemental macro- and micro-minerals, salt, monensin and urea provided as a uniform blend with cane molasses; (3) LS minus monensin, that was provided in a 3% premix with dried distillers grains plus solubles before combination into a complete mixed diet (LS-MON) and (4) LS, except that condensed molasses solubles replaced 41% (DM basis) of the cane molasses solids (LSUF). In a 112-day trial involving 160 Holstein steers (473 ± 32 kg) cattle fed DS, LS, LS-MON and LSUF diets had similar (P > .10) ADG, DMI, feed efficiency and estimated dietary NE. The effects on characteristics of digestion were evaluate using four Holstein steers with cannulas in rumen and proximal duodenum. There were no treatment effects (P > .10) on ruminal digestion of OM, and feed N, microbial efficiency and ruminal N efficiency. It is concluded that the form of incorporation of minor dietary ingredients during batch mixing (dry premix or in combination with a liquid carrier) will not appreciably affect the feeding value of growing-finishing diets for feedlot cattle