This study examined the short- and long-term effects on the reproductive performance of sheep by subjecting them to varieties of subterranean clover (Trifolium subterraneum) with a low content of total phytoestrogens and formononetin. In a first trial, 30 ewe lambs of the Sarda breed (initial mean live weight of 16.35 kg) were divided into three groups of 10 animals each and maintained on pasture for 60 days, with alfalfa (Medicago sativa L.), oats (Avena sativa), and subterranean clover with a phytoestrogen content ranging from 10.21 mg/g on a dry matter basis (DM) at the onset of the trial to 0.90 mg/g DM at the end, respectively. The three pastures were adequately integrated to make them isoproteic and isoenergetic. At the end of the grazing period, the animals were pooled into one group and fed the same phytoestrogen-free diet. No differences were found between the groups with regard to development of the reproductive system - checked by transvaginal ultrasonography - fertility, fecundity, or breeding performance of the ewes, or with regard to the birth weight and conformation of the lambs. Puberty was attained earlier by the animals fed on subterranean clover and they also weighed more. In the second trial, 24 ewe lambs of the Comisana breed (initial mean live weight of 25.0 kg) were divided into two groups of 12 animals each and fed ad libitum in a sheepfold for 20 months with fresh-cut or dried subterranean clover with a phytoestrogen content of 0.88 and 0.81 mg/g DM, respectively, or with a control non-estrogenic diet, based on freshcut or dried Italian ryegrass (Lolium multiflorum Lam.). The two diets were integrated so that they were isoenergetic and isoproteic. No differences were recorded between the groups with regard to the attainment of puberty, - even though the animals fed with clover were heavier at puberty - development of the reproductive system, fertility, fecundity, or breeding performance of the animals, either at the first or the second lambing, regarding the interval between lambings, or in the weight and conformation of the lambs born. In both trials, neither non degraded phytoestrogens nor equol were recorded in the blood of the ewes, with the only metabolite present being p-ethylphenol. All animals fed on subterranean clover-based diets showed a significantly greater ADG than those fed with the control diets. The results of this study indicate that levels of total phytoestrogens and formononetin in the new varieties of subterranean clover do not negatively affect the reproduction of sheep and appear to improve the growth of the animals.
|Autori:||Pace, V.;Contò, G.;Carfì, F.;Chiariotti, A.;Catillo, G.|
|Data di pubblicazione:||2011|
|Titolo:||Short- and long-term effects of low estrogenic subterranean clover on ewe reproductive performance|
|Rivista:||SMALL RUMINANT RESEARCH|
|Appare nelle tipologie:||1.1 Articolo in rivista|