ARTIFICIAL INSEMINATION IN FARM ANIMALS - Phenix-Vet

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170Artificial Insemination in Farm Animalsrapidly to the onset of the breeding season and continue to respond with an increase inovulation rate (Keisler & Buckrell, 1997). Flushing is understood as the rapid increase inovulation rate of ewes receiving a nutrient supplementation before mating. Under harshernutritional conditions in the semi-arid southern Mediterranean region, where regular foodsupply is not guaranteed, lambing and twinning rates were shown to be boosted followingnutritional flushing (Younis, et al., 1978; Landau & Molle, 1997; Branca, et al., 2000) or whenthe live weights of the ewes were higher at mating (Gunn & Doney, 1979, Thomson &Bahhady, 1988).However, Lassoued et al. (2004), showed important interactions between genotype and levelof nutrition. In this sense, in highly prolific ewes like D’Man breed, higher levels of nutritionprior to and during mating were associated with improved reproductive performance, butin low prolific breeds such as Queue Fine de l'Ouest, neither ovulation rate nor lambing ratewere affected by the dietary treatment. In a recent work by Fukui et al. (2010) body weightdid not significantly affect fertility.Body condition score (BCS) has proved useful as a management tool for subjectivelyassessing the nutritional status of ewes. In this way, body condition directly affectshypothalamic activity and GnRH secretion, but not pituitary sensitivity to GnRH, and theseeffects on reproductive performance are also mediated through changes in ovarianhormones or in hypothalamo-pituitary sensitivity to ovarian hormones (Rhind, et al., 1989).The effect of body condition on the ovulation rate of ewes has been extensively reported(Ducker & Boyd, 1977; Morley, et al., 1978; Adalsteinsson, 1979; Gunn & Doney, 1979;Gonzalez, et al., 1997). High body condition score has been associated with an increase ofovulation (Rhind, et al., 1989; Xu, et al., 1989), especially in Mediterranean breeds at thebeginning of the breeding season (Forcada, et al., 1992). Most authors recommend a BCS of2.5 to 3.0 either for natural or artificially breeding (Contreras-Solis, et al., 2009; Husein &Ababneh, 2008). In a study carried out in inseminated Rasa Aragonesa ewes (Bru, et al.,1995), the lowest pregnancy rates (32,7 %) were obtained in sheep with a BCS3.The importance of BCS in fertility has been also reported in Spanish Manchega breed(Montoro, 1995).Fukui et al. (2010), , concluded that body nutritional condition is an important factor, next toewe age, influencing the fertility of ewes after AI regardless of body weight. Nulliparousewes less than 3 years old and with a BCS of more than 3.0 are expected to have higherfertility than other types of ewes.2.6 Farm/HerdDifferent ewe farms have different management practices and this may have an impact onfertility after AI. Reproductive planning (intervals between lambings, season, age of firstmating, AI technique, etc.) and animal handling (feeding, health, preparation of AI lots, etc.)have a great effect on fertility results (Anel, et al., 2005). The significant effect of the farm hasbeen described in several studies (Anel, et al., 2005, Fantova, et al., 1999, Paulenz, et al.,2002).Thus, in order to improve fertility results, handling conditions on farms must beimproved, along with more widespread use of AI techniques.The geographical area where the farm is located may also have an influence on the successof AI. In a recent study carried out in north-eastern Spain (Palacin et al., 2011), data from18.528 AI in Rasa Aragonesa ewes belonging to a selection scheme with similar management
Management Factors Affecting Fertility in Sheep 171were recorded in order to analyse the effect of farm geographical location and thetheoretical time distance between the farm and insemination centre on the fertility aftercervical AI. An average fertility of 54.3% was observed, with significant differences amongthe 14 regions studied. Fertility rates higher than 60% were found in the northern regionsnear the Pyrenees Mountains and the lowest results (38.5-48.3%) were obtained in thesouthern regions. The average time distance of these regions did not differ. The regionsnearest to the insemination centre, with similar climatic conditions, showed medium fertilityrate (54.0-57.8%). These results showed a huge variability after insemination, taking intoaccount the geographical location of the farm.2.7 Heat stressIt has been reported than in tropical and sub-tropical areas the local sheep show restrictedsexual activity in the summer months (Marai et al., 2004). Marai et al., 2007 reviewed howexposure to high ambient temperature causes impairment of reproductive functions insheep. The heat effect is aggravated when heat stress is accompanied with high ambienthumidity (Marai et al., 2000, 2004, 2006, 2007). Heat stress evokes a series of drastic changesin animal biological functions, which include a decrease in feed intake efficiency and use,disturbances in the metabolism of water, protein, energy and mineral balances, enzymaticreactions, hormonal secretions and blood metabolites. (Shelton, 2000; Marai et al., 2006).2.8 Synchronization treatmentOestrous synchronisation and ovulation induction treatments are widely spread in AI inorder to control the optimum insemination time. Oestrous behaviour in small ruminants isnot clearly shown, so treatments are needed to prevent an asynchrony between ovulationand insemination time, which may be the commonest cause of failure of artificialinsemination programmes (Jabbour & Evans, 1991).Synchronisation treatments are a useful tool not only for AI programmes but also in naturalmating, particularly to ensure lambing in anoestrous season. However, many studies reportthat synchronisation causes reduced fertility after cervical AI (Robinson, et al., 1970; Hawk,1971) and after natural mating (Quinliva.Td & Robinson, 1969; Hawk & Conley, 1975;Allison & Kelly, 1978). Different hormonal treatments have been used in the control of sheepreproduction, but progestagen analogues (fluorogestone acetate and medroxyprogesteroneacetate) are the most commonly used to induce and synchronise oestrus in natural mating orAI of small ruminants (Lunstra & Christenson, 1981; Pearce & Robinson, 1985; Langford, etal., 1982; Baril, et al., 1993, Greyling, et al., 1997). Progestagens produce a mimetic effect ofthe luteal phase of the oestrous cycle and a sudden progestagen removal followed byadministration of an equine chorionic gonadotropin (eCG) dose (FSH- and LH-likestimulation) induces oestrous activity. Currently, intravaginal progestagen-impregnateddevices (sponges or CIDR) for 12-14days followed by administration of 250-500IU eCG hasbeen proposed (Abecia, et al., 2011) as a synchronised treatment in sheep, in whichinsemination can be performed from 47h (intrauterine) to 55 (cervical) hours after deviceremoval.Although long-term progestagen treatment results in efficient oestrous synchronisation,high variability has been reported in fertility (Vinoles, et al., 2001; Menchaca & Rubianes,2004;). Progestagen treatment appears to result in an asynchrony between oestrus andovulation (Scaramuzzi, et al., 1988; Sirois & Fortune, 1990) and reduce sperm transport
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VIContentsChapter 9Evaluation of a
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ARTIFICIAL INSEMINATION IN FARM ANIMALS - Phenix-Vet

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