Feed intake of grazing calves exposed to trichostrongyle infection and treated with the morantel sustained release bolus

Herbage intake was measured in two groups of 20 first-year grazing cattle. The animals in one group each received a morantel sustained release bolus at turnout to control nematode parasitism and the animals in the other group remained untreated. The latter group showed a mean peak faecal egg count of 655 eggs per gram (e.p.g.) in October associated with high serum pepsinogen concentration and clinical signs of ostertagiasis, compared with a peak of 119 e.p.g. in the treated group which remained in good health. In September the daily voluntary feed intake of the untreated animals was significantly depressed (94 g kg-1 body weight vs. 77 g kg-1 P less than 0.001), but no difference in digestive efficiency was recorded between the two groups. This difference in feed intake was associated with a 47 kg mean live weight advantage of the treated animals at housing.     

Effect of strategic treatments with invermectin on parasitism of set-stocked calves exposed to natural trichostrongyle infection in Lithuania

The effect of strategic treatments with ivermectin in first-season calves exposed to trichostrongyle nematodes on naturally contaminated pasture was studied. Twenty first season heifer calves were divided into 2 groups, according to live weight, and on 22nd May each group was turned out onto a 1 hectare pasture. Group A (Plot A) was treated with ivermectin at weeks 3, 8 and 13 after turn out, while group B (Plot B) served as an untreated control group. The study showed that control calves exhibited increase in trichostrongyle egg counts in August, while treated calves were excreting low numbers of trichostrongyle eggs. Pasture larval counts on Plot B (control animals) were low during the first part of the grazing season, followed by a steep rise towards the end of July. In contrast, the numbers of infective larvae recovered from Plot A remained low throughout the season. Both groups showed comparable weight gains from May up to the middle of July. However, from then on, Group B (controls) had lower weight gains than ivermectin treated Group A. From the end of July onwards, most untreated calves (Group B) showed clinical signs of parasitic gastroenteritis. It can be concluded that the strategical ivermectin treatments were successful, and faecal egg counts, pepsinogen levels and herbage larval counts clearly demonstrated that this was accomplished through suppression of pasture contamination with nematode eggs and subsequent reduction of pasture infectivity.     

The spring-rise phenomenon: Seasonal changes in the worm burdens of breeding ewes and in the availability of pasture infection

Extract

A Mastitis control programme is essentially a biological regulatory system involving the three essential components of any control mechanism:

• A signal from a detector indicating departure from normality

• The interpretation of the signal (diagnosis)

• A feed-back signal to the origin of the detection signal indicating corrective action.

     

The significane of Nematodirus helvetianus eggs which have survived on a pasture throughout the winter in the transmission of infection to calves.

A field experiment was carried out to determine the significance of Nematodirus helvetianus eggs which had survived throughout the winter in the transmission of infection to calves turned on to a pasture in the early summer. The calves became infected but did not exhibit symptoms of clinical disease. It was concluded that eggs which survive the winter are unlikely to be associated with outbreaks of disease.     

Forms of bovine pepsinogen in plasma from cattle with three different 'syndromes' of Ostertagia ostertagi infection

Calves infected orally with third stage larvae of Ostertagia ostertagi or infected with adult O ostertagi by direct transplantation into the abomasum had raised plasma pepsinogen activity, as did four-year-old dairy cattle challenged with O ostertagi third stage larvae on five occasions. Using fast protein liquid chromatography two forms of pepsinogen; pepsinogen 1 (PG1) and pepsinogen 2 (PG2) were identified in each of the parasitic infection regimes.     

The diagnostic value of plasma proteins and non-protein nitrogen substances in birds

This paper summarises current knowledge of the diagnostic value of avian plasma proteins and non-protein nitrogen substances. Reference values for total protein, the albumin: globulin ratio, uric acid, creatinine, and urea for various avian species are presented. The importance of the albumin:globulin ratio and the urea:uric acid ratio is emphasised.     

Evaluation of the diagnostic value of plasma copper levels in cattle

Copper (Cu) is an essential trace element. Depletion of liver-Cu stores leads to clinical or sub-clinical Cu deficiency. Our objective was to evaluate plasma-Cu levels as a diagnostic test for the assessment of Cu status in cattle. We used liver-Cu levels as the gold standard. The chosen cutoff for plasma Cu was 9 mmol/l; two different cutoffs were chosen for liver-Cu: 20 and 10 microg/g dry matter (DM). When 20 microg/g DM of liver Cu was the cutoff, plasma Cu had sensitivity=69% (58, 79) and specificity=84% (74, 93). The same values if the cutoff in liver was 10 microg/g were 92 (82, 100) and 73% (64, 82), respectively. ROC curves showed that the best cutoff to be used for plasma Cu was 8.26 mmol/l; however, no significant improvement was found in sensitivity or specificity. We concluded that interpretation of plasma-Cu levels significantly varies with the liver-Cu cutoff.     

Relative contributions of late dry-season and early rains pasture contaminations with trichostrongyle eggs to the wet-season herbage infestation in eastern Nigeria

Two worm-free grass paddocks, P1 and P2, were artificially contaminated in March and April-May, respectively, with bovine faeces containing known numbers of trichostrongyle (mainly Cooperia, Haemonchus and Trichostrongylus spp.) eggs in order to determine the relative contributions of late dry-season and early rains pasture contaminations to the wet-season herbage larval infestation in Nsukka, eastern Nigeria. The resulting herbage infestation was assessed by means of larval counts and tracer studies. A sudden rise in herbage infestation occurred simultaneously in both paddocks in late April, this apparently being determined by the onset of the first substantial rainfall of the wet season. Peak infestations in both paddocks also occurred simultaneously in May. The infestation in P1 was much larger, and the larval population persisted longer, than that in P2 and later gave rise to a second smaller peak in June. No L3 were recovered in herbage samples from either of the paddocks after the third week of July. Both paddocks were infective to goats in May-June, while P2 was also infective in July-August. The results suggest that in the Nigerian derived savanna the initial wet-season herbage infestation in pastures grazed by infected cattle during the dry and wet seasons will consist of L3 from late dry-season and early rains pasture contaminations, the former being the major contributor to the infestation. Consequently, pastures contaminated during the late dry season may not be safe for susceptible animals to graze at the start of the succeeding rainy season.     

A comparison of three rapid diagnostic methods for the detection of rotavirus infection in calves

Three techniques for the detection of rotavirus in faecal samples from calves with neonatal gastroenteritis were compared. A preliminary study indicated that reverse passive haemagglutination (RPHA) was at least as sensitive as the enzyme-linked immunosorbent assay (ELISA). These two immunoassays were compared with the detection of viral RNA by polyacrylamide gel electrophoresis (PAGE) on 209 field samples. Of the 77 samples in which at least one test gave a positive result, 69 were positive by both RPHA and PAGE, but only 49 were also positive by ELISA, indicating a lower sensitivity for the latter test. The overall agreement between RPHA and PAGE was 96%. The reasons for the discrepancies between the tests are discussed.