Experimental and natural infection with the enzootic leukosis virus of cattle

A trial was performed with heifers at the age of six to seven months. The animals were experimentally infected with the lymphocytes of a virus-productive donor. Infection was produced in all the nine cases, as demonstrated by means of the positive syncytial test. As indicated by the results of the trial, the antibodies to the enzootic bovine leucosis virus (BLV) were produced soon after experimental infection. A high sensitivity of the serum-neutralization test and the ELISA method was demonstrated in this connection: by these methods, the antibodies were identified already two to three weeks after experimental infection whereas by the immunodiffusion test they could be detected only after five weeks. Twenty-four animals were exposed to natural contact infection. Within 270 days of the trial, the disease after contact was recorded only in one heifer out of the four that were in close contact with the experimentally infected animals. In this case, as compared with experimental infection, the antibodies were produced much later--after 85 to 93 days. Leucosis was recorded in none of the remaining animals. The reasons why such a favourable result was obtained were the thorough disinfection of the stables after blood collections and the strict observance of the aseptic conditions. The results of experimental infection in three cows were identical with those obtained in young cattle. In the experimentally infected dairy cows, antibodies in milk were determined by the ELISA method. As found, in milk the antibodies to BLV appear two to three weeks later than they do in serum. The ELISA method of BLV antibody detection can be used for the identification of infected animals in herds where enzootic bovine leucosis occurs.     

Estrus and ovulation synchronization in Merino meat sheep. 2. Fertility outcome after estrus and ovulation synchronization with Cloprostenol "Jenapharm" and Gonovet "Berlin-Chemie" and term-oriented artificial insemination]

49 of 102 sheep of one production herd, which had returned to oestrus once or twice within the 1985 breeding season, were treated twice in a nine-day interval with the PGF2 alpha analogue Cloprostenol "Jenapharm". 53 animals received an additional dose of 10 micrograms of Gonavet "Berlin-Chemie". A lambing rate of merely 15% was achieved by subsequent term-oriented artificial insemination. 31 sheep still in oestrus one day after term-oriented artificial insemination were served, bringing the lambing rate from synchronisation of oestrus and ovulation to 26% and the lambing result to 154%. Serving of the remaining sheep in 2 subsequent oestric cycles, on balance, yielded lambing rates and results of the remaining sheep in 2 subsequent oestric cycles, on balance, yielded lambing rates and results which were higher with significance than those recorded from untreated sheep in the same herd.     

Correct equations for comparing models in diallel analysis

SUMMARY: Correct equations are given to express the parameter estimates of four models for complete diallels as a function of the parameter estimates in the model of Eisen et al. (1983). In recent literature these equations have been partly incorrect. ZUSAMMENFASSUNG: Korrekte Gleichungen für den Vergleich von Modellen in der Diallelanalyse Für die Darstellung der Parametersch?tzwerte von vier Modellen für vollst?ndige Diallele als Funktion der Parametersch?tzwerte des Modells von Eisen et al. (1983), die in der Literatur teilweise fehlerhaft erfolgte, werden korrekte Formeln angegeben.     

Breeding objectives for beef cattle used in different production systems: 2. Model application to production systems with the Charolais breed

A general bio-economic model for beef cattle production was used to define breeding objectives for Charolais cattle to be utilized in a variety of linked production systems. Economic weights were calculated for 16 traits (some with both direct and maternal components) in three production systems (pure-breeding and terminal crossing with beef or dairy cows) and two marketing strategies (sale or fattening of weaned surplus calves). Economic weights for the total breeding objective were calculated as weighted averages, where weights were numbers of cows expected to be mated with Charolais bulls in each production system and marketing strategy. Results suggest that the direct component of calving performance and cow longevity were of primary economic importance in all systems. Conception rate of cows and weaning weight reached about 50% of the standardized economic weight of calving performance in purebred systems with sale of weaned calves, whereas in purebred systems with fattening the economic importance of the direct component of cow conception rate, losses at calving, mature weight of cows, weaning weight, and fattening traits were of equal importance (each approximately about 20% that of calving performance). In terminal crossing systems, weaning weight was important when calves were sold at weaning, and fattening traits were important for systems selling fattened animals. The bio-economic model performed well under the conditions of this demonstration and could easily be customized for other applications.     

Ecotonal changes and altered tree spatial patterns in lower mixed-conifer forests, Grand Canyon National Park, Arizona, U.S.A.

This research analyzes patch development and determines tree spatial patterns along the lower mixed-conifer ecotone on the North Rim of Grand Canyon National Park in Arizona (U.S.A.). Patterns of patch development were interpreted from spatial analyses, based on tree age and size, and past records of disturbance and climate. Five plots in the ecotone between mixed conifer forests and monospecific stands of ponderosa pine (Pinus ponderosa) were studied for patterns of patch development. The methods used include: (1) size-structure analyses, to compare species patch development; (2) dendrochronological dating of tree establishment; (3) tree ring master chronology, to determine periods of suppressed growth, compared to a Palmer Drought Severity Index; and (4) spatial analyses by species composition, size and age, with univariate and bivariate analyses of spatial association and spatial autocorrelation. We found an increased density of shade-tolerant and fire-intolerant species namely clusters of pole-sized white fir, and fewer large ponderosa pine. This revised version was published online in May 2005 with corrections to the Cover Date. This revised version was published online in July 2006 with corrections to the Cover Date.     

Efficacy of a mephentermine‐based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle

The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY^® INJETÁVEL (POT), a mephentermine‐based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized‐complete‐block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume‐matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six‐day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end‐tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady‐state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post‐treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dt_max: +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dt_min: +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo‐control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection.