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Accueil du site → Doctorat → États-Unis → 1989 → Management and productivity of sheep flocks in Meknes province, Morocco, with especial reference to abortion and lamb mortality

University of Minnesota (1989)

Management and productivity of sheep flocks in Meknes province, Morocco, with especial reference to abortion and lamb mortality

Chaarani, Bahija

Titre : Management and productivity of sheep flocks in Meknes province, Morocco, with especial reference to abortion and lamb mortality

Auteur : Chaarani, Bahija

Etablissement de soutenance : University of Minnesota

Grade : Doctor of Philosophy (PhD) 1989

Résumé
Losses in sheep flocks may occur during various stages of the productive processes. The determination of the factors involved in these losses is an essential step toward the improvement of sheep production systems. Two studies were carried out ; one extensive study based upon 220 flocks selected from six counties in Meknes province, Morocco and a second intensive two years (1984-86) study was carried out in 16 of the 220 flocks in one county. The objectives of this study were : (1) To define the effect of seasonality and flock management on flock productivity. (2) To investigate the causes of lamb mortality using a standardized necropsy method and carrying out microbiological analyses. (3) To investigate the causes of abortion and infertility in ewes by retrospective serological analyses. The results of the intensive study showed that the lambing rate, the dam weight at lambing and the weight of lambs increased with higher levels of supplemental feeding. Mean lambing rate was 81.3% (1984-85) and 79% (85-86). There was large variation among flocks in lambing rate and reproductive efficiency. Mean lamb mortality rates were 17.6% (84-85) and 31.3% (85-86). Lamb mortality also varied according to nutrition and lambing season. Of the lambs necropsied the starvation/exposure complex contributed most to lamb mortality followed by enteritis and septicemia. The microbiological agents isolated from lambs with evidence of infection were E. coli, Salmonella, P. multocida and P. hemolytica. The reported abortion rate was 6% for both years. Of the 16 study flocks examined only one was positive for bluetongue virus, one for Brucella sp and one for Coxiella burnetii. Six flocks had evidence of serological infection with Chlamydia psittaci. Twelve flocks were positive for Toxoplasma gondii. Eleven flocks were positive for L. pomona, one for L. hardjo and none for L. canicola, L. grippotyphosa and L. icterohemorragiae. Considering the results of this study, sheep losses can be controlled by improvement of nutrition and health care in many of these flocks through extension and more careful monitoring of performances.

Présentation (PROQUEST)

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