Effect of treatment with oral Ca boluses following calving on concentrations of Ca in serum in pasture-based dairy cows.

AIMS To assess the effect of the administration of two oral Ca boluses on concentrations of total Ca, ß-hydoxybutyrate (BHB) and non-esterified fatty acids (NEFA) in serum, and urine pH, in recently calved pasture-fed dairy cows. METHODS Friesian or Friesian cross Jersey cows from one dairy farm were blocked by age and randomly assigned to no treatment (control; n=14), or treatment (n=13) with two oral Ca boluses administered approximately 12 hours apart, with the first bolus being given within 14 hours of calving. Each bolus weighed 198 g and contained 43 g of Ca; 31 g of Ca from calcium chloride and 12 g of Ca from calcium sulfate. Cows were enrolled over three calendar days, and all cows were managed in one group during the 24-hour study period. Blood samples were collected at 0, 1, 2, 4, 8, 12, 13, 14, 16, 20 and 24 hours after the initial treatment. Serum from each time point was analysed for concentrations of total Ca, and from 0, 12, and 24 hours for NEFA and BHB. Urine was collected at 0, 12 and 24 hours for pH measurement and pH was categorised as <7 or ≥7. The effect of treatment on percentage change in concentrations of Ca in serum relative to 0 hours, and concentrations of NEFA, BHB and urine pH, was examined using multivariable repeated measures mixed models with cow as a random effect. RESULTS In the final multivariable model for percentage change in concentrations of Ca, there was an interaction between time and treatment (p=0.004), with the percentage increase being higher in treatment than control cows at 1, 2, 4, 8 and 13 hours. At 12 hours, 5/13 (41%) treated cows had a urine pH <7compared to 0/12 (0%) control cows (p<0.001), and at 24 hours 13/13 (100%) treated cows had urine pH <7 compared to 0/12 (0%) control cows (p<0.001). Over the 24-hour period, mean concentrations of NEFA or BHB in serum were similar in treated and control cows (p>0.3). CONCLUSIONS AND CLINICAL RELEVANCE Oral treatment with two Ca boluses increased concentrations of total Ca in serum and decreased urine pH in pasture-fed cows. This bolus has the potential to reduce the prevalence and duration of subclinical hypocalcaemia in recently calved cows.

The detection of Tomato spotted wilt virus (TSWV) in individual thrips using real time fluorescent RT-PCR (TaqMan).

Tomato spotted wilt virus (TSWV) is an important virus, economically in the UK, causing damaging disease in ornamental and vegetable crops. The virus is vectored by several species of thrips, most importantly the western flower thrips (Frankliniella occidentalis Pergande [Thysanoptera: Thripidae]). The vector thrips themselves constitute a damaging pest and are difficult to control completely. Monitoring thrips numbers is an important part of the control of virus, but does not give information on how many of the thrips are viruliferous. Monitoring the presence of viruliferous thrips at an early stage of an epidemic may lead to improved disease control, since virus can be spread effectively whilst vector pressure is low and symptoms may take several weeks to appear on some hosts. This paper describes the development of a sensitive and robust, high-throughput method for the detection of TSWV in individual insects based on TaqMan chemistry. The method incorporates a novel RNA specific internal control to increase the reliability of the results. Results are also presented on comparisons of different extraction methods, including insects taken from sticky traps, for high-throughout testing. Implementation of a method such as this for the reliable detection of TSWV in individual thrips would aid the understanding of the progress of TSWV epidemics, and offer an early disease warning system for growers.

Haematological changes in N'Dama and Gobra Zebu bulls during Trypanosoma congolense infection maintained under a controlled feeding regimen.

Haematological changes were monitored in Gobra-Zebu and N'Dama bulls following infection with Trypanosoma congolense. The cattle were offered a diet which provided levels of protein and energy above maintenance requirement and a pair feeding regimen was used in order to eliminate the confounding anorexic effects of trypanosomosis on the traits studied. Packed red cell volume (PCV), red blood cells (RBC) and haemoglobin (Hb) were monitored weekly. Mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), and mean corpuscular volume (MCV) were derived by computation. Significant breed differences (P < 0.001) were observed in the baseline data collected with N'Dama bulls having higher (P < 0.001) values for RBC and Hb. PCV levels were similar in both breeds pre-infection. Post-infection, there was a significant (P < 0.001) infection effect on the RBC, Hb and PCV in both breeds. The pathogenic effects were more severe in the Gobra-Zebu bulls where three out of ten bulls compared with only one out of eight infected N'Dama bulls attained the low PCV threshold, treated and withdrawn from the study along with their pair mates. Throughout the infection in N'Dama cattle and during the first 6 weeks of infection in the Gobra-Zebu bulls, the infection presented a normochromic normocytic anaemia. However, in the chronic phase, the Gobra-Zebu bulls became macrocytic. The infection reduced total dry matter intake in both breeds although this persisted longer in the Gobra-Zebus. However, their pair-fed controls showed no haematological changes indicating that the anorexia was not compounding the effects of the infection. The severity and type anaemia in N'Dama correlates with their innate ability to resist the effects of trypanosome infection compared to the Gobra-Zebu bulls.

The effect of zinc oxide and elemental zinc boluses on the concentrations of Zn in serum and faeces, and on providing protection from natural Pithomyces chartarum challenge in calves.

AIM: To investigate the efficacy of intra-ruminal Zn boluses as aids in providing protection from natural Pithomyces chartarum challenge in calves. METHODS: Sixty-two calves (mean weight 187 (SEM 3.25) kg) were divided into three groups. Commencing on Day 0, they received either a proprietary bolus containing 83% ZnO (ZnO group), a prototype Zn bolus containing 88% elemental Zn (Zn group), or remained untreated (Control group). Concentrations of Zn in serum and faeces were measured weekly between Days 6 and 34, activities of gamma-glutamyl transferase (GGT) in serum on Days -8, 20, 34 and 41, and faecal spore counts between Days 13 and 41. RESULTS: Between Days 6 and 34, mean concentrations of Zn in serum increased in both Zn treatment groups compared with Controls (p<0.001), but were lower in Zn than ZnO animals between Days 6 and 28 (p=0.05). Concentrations of Zn in faeces were increased in both groups following treatment with Zn. Mean concentrations of Zn in faeces in ZnO animals was higher than Zn animals on Days 13 and 20 (p<0.001), but decreased by Day 34, whereas for Zn animals they were still elevated on Day 34. Faecal spore counts were 354,000 and 183,000 on Days 13 and 20, respectively, 610,500 on Day 28, and 115,500 spores/g on Day 34. There were no clinical signs of facial eczema, but based on the activities of GGT on Day 41, 17/20 (85%) Controls were moderately or severely affected (GGT >250 IU/L) compared with 1/21 (5%) ZnO and 3/21 (14%) Zn animals. Mean activities of GGT on Day 41 for ZnO and Zn animals were not different (35 (95% CI=23-54) and 54 (95% CI=32-92) IU/L, respectively; p=0.18), but were below those of the Controls (502 (95% CI=296-850) IU/L), confirming efficacy of both bolus treatments. In both ZnO and Zn animals, there was no significant relationship between concentration of Zn in serum and activity of GGT, but in Zn animals there was a significant relationship between the concentration of Zn in faeces and activity of GGT 21 days later. The regression equation y=2.136-0.002197x (where y is log10GGT activity, and x the concentration of Zn in faeces) provided an estimate of the threshold level of concentration of Zn in faeces. CONCLUSION: The study confirmed efficacy of elemental Zn boluses in providing protection from natural P. chartarum challenge in young cattle.

The effect of zinc oxide and elemental zinc boluses on the concentrations of Zn in serum and faeces, and on providing protection from natural Pithomyces chartarum challenge in sheep.

AIM: To investigate the efficacy of intra-ruminal Zn boluses as aids in providing protection from natural Pithomyces chartarum challenge in sheep. METHODS: Seventy-two adult sheep (mean weight 59 (SEM 0.5) kg) were divided into four groups. Commencing on Day 0, they received either a proprietary bolus containing 67 g ZnO (equivalent to 54 g Zn) (ZnO group), two different levels of elemental Zn (81 and 108 g) delivered in boluses each containing 27 g Zn (Zn81 and Zn108 groups, respectively), or remained untreated (control). Concentrations of Zn in serum, activities of gamma-glutamyl transferase (GGT) in serum, and spore counts on pasture were measured weekly from Day -6, and concentrations of Zn in faeces weekly from Day 21, until Day 77. RESULTS: Mean concentrations of Zn in serum between Days 14 and 42 were significantly higher in ZnO animals (15.4 (SEM 0.70) micromol/L) than the other groups. Mean concentrations in Zn108 animals (11.1 (SEM 0.26) micromol/L) were significantly higher than controls, but there were no differences between Zn81 and the controls (9.9 (SEM 0.20) and 9.4 (SEM 0.26) micromol/L, respectively). Between Days 21 and 49, there was no significant difference in mean concentrations of Zn in faeces between ZnO and Zn81 animals (307 (SEM 28) and 281 (SEM 29) mg/kg fresh weight (FW), respectively), but concentrations were significantly higher in Zn108 animals (500 (SEM 40) mg/kg FW). Spore counts exceeded 70,000/g on Days 14, 28, 49, 56 and 63 but there were no clinical signs of facial eczema. In controls, activities of GGT were unchanged until Day 21, then increased to 637 IU/L at Day 70; for ZnO animals, activities remained <75 IU/L until Day 14, then increased to 200 IU/L at Day 70; for Zn81 and Zn108, they remained <75 IU/L until Day 35, and then increased at Day 70 to 369 IU/L and 293 IU/L, respectively. From Day 56 activities were significantly lower in all treated groups compared with controls, but there was no significant difference between the three Zn bolus treatments. There were significant negative correlations between activities of GGT and concentrations of Zn in serum in Zn108 animals, and with concentrations of Zn in faeces for both Zn81 and Zn108 groups. CONCLUSION: Elemental Zn boluses can reduce activities of GGT associated with elevated spore counts. The association between concentrations of Zn in faeces and activities of GGT suggests that a minimum concentration of Zn in the gastrointestinal tract may be important in providing protection against sporidesmin.

Impact of nutrition on the pathophysiology of bovine trypanosomiasis.

Trypanosomiasis is a major veterinary problem over much of sub-Saharan Africa and is frequently associated with under-nutrition. There is growing evidence that nutrition can have a profound effect on the pathophysiological features of animal trypanosomiasis. These features include anaemia, pyrexia, body weight changes, reduced feed intake and diminished productivity including reduced draught work output, milk yield and reproductive capacity. Anaemia is a principal characteristic of trypanosomiasis and the rate at which it develops is influenced by both protein and energy intakes. Pyrexia is associated with increased energy demands for maintenance which is ultimately manifested by reductions in voluntary activity levels and productivity. Weight changes in trypanosomiasis are markedly influenced by the levels of protein intake. High intakes allow infected animals to grow at the same rate as uninfected controls providing energy intake is adequate whilst low energy levels can exacerbate the adverse effects of trypanosomiasis on body weight. Reductions in feed intake are less apparent in animals which are provided with high protein diets and where intake is limited by the disease animals will often exhibit preferential selection of higher quality browse. Further studies are required to evaluate the minimum levels of protein and energy supplementation required to ameliorate the adverse effect of trypanosomiasis, the nature and quality of protein supplement to achieve these benefits and the influence these have on digestive physiology.