Vascular pattern of the developing intertarsal joint in the domestic fowl

The origin and nature of vascular canals in the distal tibiotarsus and proximal tarsometatarsus of the fowl have been described. The vascular pattern was modified at different stages of growth and there were anastomoses between epiphyseal vascular canals in the proximal tarsometatarsus. Such anastomoses are not seen in other bone extremities of the fowl and their presence may be a consequence of the incorporation of tarsal elements in proximal tarsometatarsi. In all the distal tibiotarsi examined, a third epiphyseal ossification centre was present. The pattern of metaphyseal vessels in the distal tibiotarsus and proximal tarsometatarsus was altered in some young chicks. This finding may be the result of abnormal angulation of the intertarsal joint which would result in uneven joint loading.     

Immune exclusion of Haemonchus contortus larvae in sheep: dose dependency, steroid sensitivity and persistence of the response

Naive and immune sheep, treated with anthelmintic, challenged directly into the abomasum and killed 48 hours later were used to examine the steroid sensitivity, persistence and dose dependency of immune mechanisms which result in the failure of incoming Haemonchus contortus larvae to establish (immune exclusion). Immune exclusion was almost totally abolished by corticosteroid treatment, the mean percentage of larvae establishing in the mucosa of immune sheep was 1.4 per cent of the challenge infection whereas in those treated with dexamethasone it was 24.4 per cent and in naive sheep 27.3 per cent. Immune animals challenged after seven and 42 days without antigenic experience excluded more than 90 per cent of the challenge larvae from their mucosae, whereas those challenged after 84 days without antigenic experience were as susceptible as naive animals. Immune exclusion was dose dependent, animals challenged with 10(6) and 10(5) larvae excluded 93 per cent and 82.5 per cent of the challenge dose whereas those challenged with 10(4) larvae failed to exclude larvae.     

An analysis of cellular proliferation, and synthesis of lymphokines and specific antibody in vitro by leucocytes from immunized cattle

The relationships between the production of lymphokines, cellular proliferation and antibody synthesis by immune bovine PBL in vitro was examined to identify the cellular reactions responsible for differences in the titres of serum antibodies in calves from selected sire lines and MHC Class I phenotypes. Leucocytes from 22 calves immunized with ovalbumin and DNP-BSA proliferated specifically in vitro in the presence of 1-10 micrograms/ml ovalbumin 7-28 days after the second vaccination. Significant correlations between the production of IL-2, IFN-gamma and maximum proliferation were observed for the total group. The quantity of specific antibody produced when PBL were incubated alone or with 10(-1)-10(-2) micrograms/ml ovalbumin was also correlated significantly with the maximum proliferation and the serum antibody titre between 7 and 14 days. Anti-ovalbumin IgG was also synthesized in MLRs where the quantity of antibody was significantly correlated with the magnitude of proliferation. The responses in vitro to DNP-BSA were too low to provide meaningful comparisons. The results indicate that at intervals during the period of increasing serum titres, events in the bovine antibody response in vivo can be replicated in vitro. In addition, assays for proliferation, IL-2 or gamma-IFN, or specific antibody can be used to assess the magnitude of the immune response in vivo in experimental groups of cattle. Significant sire line differences in the serological responses to ovalbumin were observed but DNP-BSA was a poorer antigen and differences in the responses to this antigen were not significant. However, the sire line differences in vivo were not reflected in vitro in proliferative and lymphokine assays; only the production of antibody in vitro was significantly correlated with the in vivo serum titre.     

In vitro evaluation of metacarpophalangeal joint loading during simulated walk

Reasons for performing study: Insight into the loading pattern of the articular cartilage surface during the complete stride is important as biomechanical factors play a pivotal role in the pathogenesis of joint trauma and osteoarthritis (OA). Objectives: To determine the loading pattern in the equine MCP articulation in vitro during simulated walk. Methods: Eight cadaveric limbs from mature Dutch Warmblood horses were loaded in a pneumatic loading device in 6 different positions (A1‐A6). The pressure distribution on the articular surface of the proximal phalanx (P1) was measured at 7 sites (S1‐7) using intra‐articularly placed pressure sensitive films, which were analysed by scanning and densitometry. Results: Pressures recorded after mid‐stance (A4, 5, 6) were significantly (P<0.05) higher than those before (A1, 2, 3) and showed the biphasic loading pattern of the walk at all sites, except for the site halfway along the sagittal groove (S7). At S7, there was a linear increase in pressure during the progress of the stance phase of the stride in most horses. Medially (S4, 5, 6) the pressure was significantly higher than laterally (S1, 2, 3) (P<0.05). Conclusions and potential relevance: The heavier medial loading coincides with the location where articular cartilage degeneration in the process of OA in the equine MCP joint is known to start. The discrepancy between the loading of the central groove and the other parts of the joint may result in large stress differences at the end of the stance phase, which might be related to the pathogenesis of stress fractures in the first phalanx and distal third metacarpal bone.     

Veterinary aspects of ecological monitoring: the natural history of emerging infectious diseases of humans,domestic animals and wildlife

Proliferation of disease pathogens capable of affecting humans, domestic livestock and wildlife increasingly threatens environmental security and biodiversity. Livestock and wild animals in proximity to human beings are often in the chain of transmission and infection. Globalization of industrial livestock production (especially poultry upon which so much of the burgeoning human population depends) often permits transcontinental disease spread. Rapidly expanding (and often illegal) international trade in wild and domestic animals and their products are increasingly involved in the emergence of new diseases that may have the ability to transmit among humans, livestock and wildlife. Rapidly increasing urbanization has led in many places to overcrowded townships that rely on “bushmeat” for sustenance and has contributed to the emergence of virulent zoonotic pathogens. The emergence and proliferation of pathogens are exacerbated by anthropogenic transformation of natural landscapes in order to increase agricultural and livestock production. This paper posits that data gathered by veterinary ecologists should be interpreted and used by other disciplines. The importance of a thorough knowledge of the “natural history” (ecology) of the disease agent and its human, domestic and wild hosts is stressed.     

The effects of low levels of dietary trace minerals on the plasma levels, faecal excretion, health and performance of pigs in a hot African climate

The present study was performed in order to evaluate the effects of lower than usual industry levels of dietary trace minerals on plasma levels, faecal excretion, performance, mortality and morbidity in growing-finishing pigs in a hot African climate. Group 1 (n = 100 pigs) received a diet with common industry levels of trace minerals. Group 2 (n = 100 pigs) received reduced dietary trace mineral levels but were fed the same basic diet as Group 1. Mortality, morbidity, pig performance and carcass measurements were evaluated. Two pigs in Group 1 and three pigs in Group 2 died. Thirteen pigs in Group 1 and 27 pigs in Group 2 were medically treated (P < 0.05). Carcass masses, back fat depth, loin depth, and lean percent were not significantly different between the groups. However, the carcasses when evaluated revealed a non-significant higher back fat thickness, lower loin eye area and percentage of fat-free lean in barrows compared to gilts within each group. Despite lower initial masses, pigs fed diets containing industry levels of trace minerals were heavier (P < 0.05) and had a higher (P< 0.05) than average daily gains compared to those that received a diet containing lower levels of trace minerals. Faecal zinc excretion was significantly lower (P < 0.05) in pigs fed with lower dietary zinc levels. Copper, manganese and iron excretion were not affected (P > 0.05) by the dietary levels of these trace minerals. Plasma trace mineral concentrations were not affected by the dietary treatment.     

Utilization of nitrogen and energy by Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silage at two intakes

Our objective was to measure the utilization of energy (E) and N by Holstein steers when fed alfalfa and orchardgrass silages offered at 65 and 90 g DM/kg live weight (LW).75 daily. Twelve steers adapted to the Beltsville respiration chambers were assigned to three Latin squares with 42-d periods. Steers in one square had permanent catheters in the portal and two mesenteric veins. Energy and N balance were measured during a 7-d collection of feces and urine that included a 3-d measurement of respiratory exchange. Energy and N variables were not different between catheterized and uncatheterized steers. Apparent digestibilities of DM, OM, CP, neutral detergent solubles and permanganate lignin were higher (P less than .01) and digestibilities of NDF and ADF, hemicellulose and cellulose were lower (P less than .01) for steers consuming alfalfa compared to orchardgrass silage. When fed alfalfa, steers' daily gross energy intake, DE, urine energy, ME, heat production and tissue energy retention were greater (P less than .01) and fecal energy losses were less (P less than .01) than when they were fed orchardgrass. Partial efficiency of ME use for tissue energy (TE) was greater (P less than .01) for steers when fed alfalfa (46.1%) than when fed orchardgrass (35.6%). Apparent ME (kcal/LW.75) required for maintenance of TE was similar for steers when fed alfalfa (133.9) and orchardgrass (131.2) silages. Nitrogen retention (g/d) was 48% greater (P less than .01) for steers when fed alfalfa (30.6) than when fed orchardgrass (20.7). This study demonstrates that steers used ME from alfalfa more efficiently for TE deposition than ME from orchardgrass.