Szent István University Postgraduate School of Veterinary Science ...
Szent István University Postgraduate School of Veterinary Science ...
Szent István University Postgraduate School of Veterinary Science ...
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1. Introduction<br />
In traditional technologies, sheep' dairy products are typically seasonal goods. Due to the<br />
race’s inherent seasonal reproduction activity, their manufacturing is restricted to early<br />
summer. However, great commercial interest is attached to the continuous milk production. In<br />
small ruminants, gestagen+eCG (equine chorionic gonadotropin) treatment is widely used for<br />
cycle induction to get out-<strong>of</strong>-season fertility. Although these protocols are permitted in dairy<br />
flocks, in view <strong>of</strong> the increasing consumer requirements, it is better to refrain from the use <strong>of</strong><br />
sexual steroids in reproduction management <strong>of</strong> milked livestock. An alternative solution for<br />
the future is to try to form flocks, where most <strong>of</strong> the ewes are cyclic during the whole year –<br />
also out <strong>of</strong> the traditional autumn breeding season – allowing fertilization also in spring<br />
besides autumn. Based on researches concerning primarily different merino lines, we know<br />
that the ability <strong>of</strong> perennial cyclicity is genetically determined in sheep, and is in connection<br />
with melatonin receptor 1a (MT1) polymorphism, although the underlying mechanism is not<br />
known in details at the moment (Pelletier et al. 2000, Notter et al. 2003). At the same time<br />
numerous preconditions can influence the manifestation <strong>of</strong> this capacity: such as age, body<br />
condition (BC), and pheromone-exposure. In genotypes which are genetically capable <strong>of</strong> year-<br />
long ovarian cylicity, the use <strong>of</strong> long-known natural or near-natural breeding technologies<br />
(e.g. few days increased energy supplementation; flushing, pheromone exposure by<br />
introduction <strong>of</strong> vasectomized rams to ewes, photoperiodic and/or melatonin treatment) might<br />
gain new dimension, and contribute to clean, green and ethical animal breeding.<br />
The growing demand for clean technologies in animal breeding led to the development <strong>of</strong><br />
novel management tools also in dairy cow. Better understanding <strong>of</strong> the physiology <strong>of</strong><br />
seasonality and the importance <strong>of</strong> the photoperiodic signal in its regulation led to the<br />
emergence <strong>of</strong> technologies which use long-day photoperiodic treatment to increase milk yield<br />
in dairy cow (Dahl et al. 2000). Later the positive link between long-day photoperiodic<br />
treatment and increased milk yield was also proven in goat (Mabjeesh et al. 2007). This drew<br />
our attention to a possible limitation <strong>of</strong> using melatonin implants for cycle induction in sheep.<br />
Treatments acting through the melatonin pathway to induce cycle in the short-day breeder<br />
sheep may negatively influence milk production in lactating dams.<br />
Although seasonality <strong>of</strong> reproductive activity is less expressed in males compared to females<br />
rams also show year-round variation in sexual behaviour, testicular size, and quality <strong>of</strong> semen.<br />
To maximize the out-<strong>of</strong>-season reproductive performance not only ewes but also rams should<br />
be treated accordingly. Administration <strong>of</strong> melatonin in the non-breeding season was shown to<br />
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