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Sample records for hoggets

  1. Some epizootiological and clinical aspects of ovine babesiosis caused by Babesia ovis--a review.

    PubMed

    Yeruham, I; Hadani, A; Galker, F

    1998-01-31

    The study shows a close relationship between incidence of ovine babesiosis caused by Babesia ovis and the activity period and distribution area of the vector tick Rhipicephalus bursa. The most important factor limiting the distribution of this tick is a decrease in humidity. In general, it is absent from areas with an average annual rainfall of less than about 300 mm. The rate of parasitaemia and the degree of anaemia were not correlated. Decrease of the packed-cell volume ranged from 30 to 40%. Parasitized erythrocytes were not observed to block capillaries in the brain, which explained the absence of nervous symptoms in acute babesiosis. The kidney was the most severely affected organ, exhibiting acute glomerulonephritis. The lesions observed were suggestive of vascular alteration and vascular stasis, leading to anoxia of the tissues. A disseminated intravascular coagulation (DIC) syndrome was recorded in sheep infected with babesiosis. Biochemical studies revealed possible damage to the liver and kidneys. Most of the lambs (85%) that were infested with larvae, and all lambs infested with adult R. bursa ticks reacted serologically to B. ovis antigen. The serological reactions following infestation with the larvae occurred much later than those following infestation with the adult stage. Both transovarial and transstadial transmission of the parasite were demonstrated. A study of antibodies to B. ovis using IFAT in hoggets and ewes revealed high serological prevalence, i.e., 88.9% in ewes and 84.5% in hoggets. No marked seasonal fluctuation was observed. The serological findings, in addition to the fact that one splenectomised lamb reacted to larval infestation with acute ovine babesiosis, show that the preimaginal stages of R. bursa occurring in the winter can transmit B. ovis, usually causing a sub-clinical disease. This might play a major role in pre-immunizing and strengthening the premunition of the sheep against the main spring challenge by the adult ticks

  2. Towards evenly distributed grazing patterns: including social context in sheep management strategies

    PubMed Central

    Morales, Juan Manuel

    2016-01-01

    Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals’ foraging behaviour is highly selective at different spatial scales. The assessment of the ecological mechanisms modulating the spatial distribution of grazing and how to control it has critical implications for long term conservation of resources and the sustainability of livestock production. Considering the relevance of social interactions on animals’ space use patterns, our aim was to explore the potential effects of including animals’ social context into management strategies using domestic sheep grazing in rangelands as case study. Methods. We used GPS data from 19 Merino sheep (approximately 10% of the flock) grazing on three different paddocks (with sizes from 80 to 1000 Ha) during a year, to estimate resource selection functions of sheep grazing in flocks of different levels of heterogeneity. We assessed the effects of sheep class (i.e., ewes, wethers, and hoggets), age, body condition and time since release on habitat selection patterns. Results. We found that social rank was reflected on sheep habitat use, where dominant individuals (i.e., reproductive females) used more intensively the most preferred areas and low-ranked (i.e., yearlings) used less preferred areas. Our results showed that when sheep grazed on more heterogeneous flocks, grazing patterns were more evenly distributed at all the paddocks considered in this study. On the other hand, when high-ranked individuals were removed from the flock, low-ranked sheep shifted their selection patterns by increasing the use of the most preferred areas and strongly avoided to use less preferred sites (i.e., a highly selective grazing behaviour). Discussion. Although homogenization and segregation of flocks by

  3. Towards evenly distributed grazing patterns: including social context in sheep management strategies.

    PubMed

    di Virgilio, Agustina; Morales, Juan Manuel

    2016-01-01

    Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals' foraging behaviour is highly selective at different spatial scales. The assessment of the ecological mechanisms modulating the spatial distribution of grazing and how to control it has critical implications for long term conservation of resources and the sustainability of livestock production. Considering the relevance of social interactions on animals' space use patterns, our aim was to explore the potential effects of including animals' social context into management strategies using domestic sheep grazing in rangelands as case study. Methods. We used GPS data from 19 Merino sheep (approximately 10% of the flock) grazing on three different paddocks (with sizes from 80 to 1000 Ha) during a year, to estimate resource selection functions of sheep grazing in flocks of different levels of heterogeneity. We assessed the effects of sheep class (i.e., ewes, wethers, and hoggets), age, body condition and time since release on habitat selection patterns. Results. We found that social rank was reflected on sheep habitat use, where dominant individuals (i.e., reproductive females) used more intensively the most preferred areas and low-ranked (i.e., yearlings) used less preferred areas. Our results showed that when sheep grazed on more heterogeneous flocks, grazing patterns were more evenly distributed at all the paddocks considered in this study. On the other hand, when high-ranked individuals were removed from the flock, low-ranked sheep shifted their selection patterns by increasing the use of the most preferred areas and strongly avoided to use less preferred sites (i.e., a highly selective grazing behaviour). Discussion. Although homogenization and segregation of flocks by classes