Abstract
ABSTRACT. The objective of this study was characterize some productive and reproductive parameters in Syrian Awassi ewe lambs during different age stages. Thirty Syrian Awassi ewe lambs aged around 3 months were divided equally into 2 groups, high and low growing to identify productive and reproductive parameters during different stages. Blood samples were collected to determine progesterone and leptin concentrations. Daily milk samples were collected to determine the average daily production. At puberty, average body weight of higher growing was higher (48.4 kg) than de crescimento low growing (42.8 kg). Average age at puberty was 359.5 and 394.9 days for high and low groups, respectively with no differences. Mating, lambing and fecundity rates were similar among groups. Progesterone concentration was very low and increased rapidly at puberty with a sharp increase during pregnancy, followed by a noticeable decrease post lambing. There were individual variations in leptin concentration with no clear trend in groups. Average leptin concentration at puberty was 2.42 and 2.50 ng mL-1 for higher and low groups, respectively with no difference. Average daily milk production was higher for the higher group (1.495 g day-1) compared to 1.077 g day-1 for low grups. Thus, the lambs growing alter produtive and reproductive parameters.
Highlights
Puberty is an important reproductive trait and extreme delay in reaching puberty will have a negative effect on breeding efficiency (Esmailizadeh, 2014)
The onset of puberty is linked to the attainment of critical body mass (Rosales Nieto et al, 2013), and when body weight was below that threshold, first ovulation in Mouflon and Manchega ewe lambs did not occur until the beginning of the breeding season (Moreno, Brunet, Debulines, Villar, & Sebastian, 2000)
Puberty is associated with increasing pulsatile secretion of the hypothalamic gonadotropin releasing hormone (GnRH), which stimulates the release of gonadotropins and in turn gonadal activity (Delemarre, Felius, & Delemarre-Van Waal, 2008)
Summary
Puberty is an important reproductive trait and extreme delay in reaching puberty will have a negative effect on breeding efficiency (Esmailizadeh, 2014). The onset of puberty is linked to the attainment of critical body mass (Rosales Nieto et al, 2013), and when body weight was below that threshold, first ovulation in Mouflon and Manchega ewe lambs did not occur until the beginning of the breeding season (Moreno, Brunet, Debulines, Villar, & Sebastian, 2000). Carcangiu, Mura, Vacca, and Bini (2005) reported that body weight is the most important factor for the onset of puberty in the Sarda female lambs. Blood progesterone concentrations have been extensively used in the studies of animal reproduction to determine the onset of puberty in female sheep such as Suffolk in Brazil (Ferra et al, 2010) Ramboullet and Suffolk in the USA. Progesterone concentrations have been used during the oestrous cycle (Jarquin, Roldan, Zarco, Berruecos, & Valencia, 2014), during pregnancy (Alwan, Amin, & Ibrahim, 2010), in early diagnosis of pregnancy (Adama, Chiezy, Ajanusi, & Lawal, 2013), and other reproductive parameters (GrazulBilska et al, 2014) in female sheep
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