Alabart Alvarez, José Luis

Folch Pera, José

Lahoz Crespo, Belén

Mermillod, Pascal

Monniaux, Danielle

citaREA Repositorio Electrónico Agroalimentario

EAAP – 62nd Annual Meeting, Stavanger 2011 199The management of replacement ewe and ram lambs for breeding in IcelandDýrmundsson, Ó.R. and Jónmundsson, J.V., Farmers Association of Iceland, Bændahöllin,Hagatorg, IS-107 Reykjavík, Iceland; ord@bondi.isIn Iceland approximately 12-16% of the weaned lambs are kept for flock replacement and these lambs constitute nearly 20% of the national winterfed sheep population of 470.000. They are all of the Nordic short-tailed Iceland bred, both females and males being early sexually maturing, however, normally not used for breeding in former times. Improved winterfeeding after the middle of the 20th century enabled sheep farmers to include the lambs in their breeding flocks. There was a considerable variation in the application of this practice, both between flocks and regions, until it became adopted on most farms some 20 years ago. This coincided with the general adoption of pre-mating shearing in autumn, known to improve fertility in mated ewe lambs. After weaning in September, when most of the lambs are 120-130 days of age, they are normally kept on enclosed rangelands or cultivated pastures close to the farm buildings until indoor feeding begins, often 2-3 weeks before the adults ewes. As a rule ewe lambs and ram lambs, respectively, are kept separately from other sheep during the winter. Ram lambs are used for both ewes and ewe lambs. For ewe lambs polled rather than horned tups are often used. Most of the lambs weigh 40-50 kg when mating takes place. Although both lambing and prolificacy rates are lower in ewe lambs than ewes, good progress has been made on most farms, both due to better management and genetic selection for improved reproductive performance. Ultrasonic scanning has become a common practice. The best results seem to be achieved when the lambs are maintaining good body condition, both before and during the winterfeeding period, with special attention to the nutritional requirements of pregnant ewe lambs throughout gestation. Breeding of properly managed 7 month old lambs does not compromise their adult reproductive performance.Anti-Müllerian hormone (AMH) plasma concentration and eCG-induced ovulation rate in prepubertal ewe lambs as predictors of fertility at the first matingLahoz, B.1, Alabart, J.L.1, Monniaux, D.2, Mermillod, P.2 and Folch, J.1, 1CITA, Av. de Montañana 930, 50059 Zaragoza, Spain, 2INRA UMR 6175 - CNRS - Univ. Tours - Haras Nationaux, PRC, 37380 Nouzilly, France; blahozc@aragon.esIn sheep, delays in the age at first lambing give rise to unproductive periods and important economic losses. The objective of this work was to determine if the AMH plasma concentrations and the ovarian response to eCG before puberty is related to sexual precocity in sheep. Plasma samples were taken from 76 Rasa Aragonesa ewe lambs aged 109±18 days (Mean±SD) for AMH determination by ELISA. At the same time 600 IU of eCG was applied and ovulation rate (OR) recorded by laparoscopy 6 days later. Ewes were first joined to rams at 312±18 days. Correlations among OR, AMH, age and weight were assessed (Spearman’s; ρ). Differences in AMH were tested by ANOVA and percentages by generalised linear models for categorical variables. A logistic model was fitted and the ROC curve analysed to evaluate AMH as a predictor of ovulation. AMH plasma concentrations were highly correlated with OR (ρ=0.37; P<0.001), but not with age or weight. Differences in AMH were highly significant between non-ovulating ewe lambs (43.0 pg/ml) and ewes presenting an OR of either 1-2 (111.9 pg/ml) or >2 (163.1 pg/ml; P<0.0005 for both). Ewes with AMH concentrations before puberty higher than 23 pg/ml (optimum cut-off point to predict ovulation) displayed higher fertility at the first mating opportunity than ewes with AMH levels of ≤23 pg/ml (+27.9%, P<0.005). Similarly, fertility was higher in ovulating than in non-ovulating prepubertal ewes (+31.5%, P<0.0001). The present data suggest that both the ovarian response to eCG and the AMH plasma concentration could be reliable markers of the ovarian maturity status in ewe lambs. These results may be useful in the selection of replacement ewes at a very precocious age in terms of predicted fertility at the first mating. Financed by MICINN (PET 2008-76). B. Lahoz was supported by an INIA fellowship.Session 32 Theatre 4Session 32 Theatre 3

Anti-Mülleriam hormone (AMH) plasma concentration and eCG-induced ovulation rate in prepubertal ewe lambs as predictors of fertility at the first mating

http://citarea.cita-aragon.es/citarea/bitstream/10532/1696/1/2011_308.pdf

Anti-Mülleriam hormone (AMH) plasma concentration and eCG-induced ovulation rate in prepubertal ewe lambs as predictors of fertility at the first mating

Abstract

Similar works

Full text

Available Versions

citaREA Repositorio Electrónico Agroalimentario