الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
In practice, the most commonly used definition of retained fetal
membranes (RFM) is the presence of fetal membranes 24 hours or longer
postpartum (Markusfeld, 1987). The reported incidence of RFM ranges
from 1.3 to 39.2% with a median of 8.6% in dairy cattle (Kelton,
Lissemore and Martin, 1998). Many RFM cows have reduced milk yield
and develop metritis and reduced subsequent fertility (Eiler, 1997;
Joosten, Stelwagen and Dijkhuizen, 1988; Laven and Peters, 1996) as well as increased incidence of mastitis and increased culling rate (Halpern, Erb and Smith, 1985).
The mechanism of both placental expulsion and RFM are still not
clearly understood. Various factors such as age, breed, heredity,
environment, season, gestation length, abnormal parturition, hormonal
imbalance, nutrition and decreased neutrophil function have been
suggested as causative factors in RFM (Laven and Peters, 1996; Eiler,
1997; Han and Kim, 2005; Kimura, Goff, Kehrli and Reinhardt, 2002).
Various altered prepartum hormonal patterns have been associated with
RFM (Chew, Keller, Erb and Malven, 1977; Pimental, Evans and
Wagner, 1987). Moreover, selenium deficiency and other disease
condition such as milk fever have been shown to increase the risk of
retained fetal membranes (Olsen, 1993). RFM is a direct risk factor for
postpartum reproductive and metabolic disorders (Chassagne, Barnouin
and Faye, 1996) which may affect subsequent reproductive capability of
dairy cows. In fact, a negative impact of retained fetal membranes on
reproductive performance of dairy cows has been widely documented
(Thompson, Pollak and Pelissier, 1983; Loeffler, de Vries and
Schukken, 1999). Lower estrogen concentrations (Grunert, Ahlers and
Heuwieser, 1989), higher PGFM and cortisol concentrations (Peter and
8
Introduction
Bosu, 1987) and increased progesterone and decreased estradiol-17β and prolactin concentrations (Chew et al., 1977) have been reported in different studies. There are also few studies which determine blood metabolites and haematological changes as indicators for RFM in dairy cows (Chassagne and Chacornac, 1994).
RFM is a reproductive abnormality which causes serious economic problems in the cattle industry. The cost for RFM cows treated by veterinarians was estimated as about $244 per affected cow or about 154 million US dollars per year (Eiler, 1997). Furthermore, Kossaibati and Esslemont (1997) calculated the direct cost of a case of retained fetal membranes to be about 83 USD with an overall cost of retained fetal membranes 298 .29 USD (1995 prices) in England.
This study in dairy cattle was aimed to:
• Investigate factors affecting the placental DROP and its related
reproductive parameters.
• Determine the most effective treatment of placental retention.
• Assess of some trials to prevent or at least minimize its incidence.