Chemical changes and influences of rapeseed antinutritional factors on gestating and lactating ewes 1. Animal performances and plasma hormones and glucose

An experiment was carried out in order to study the effects of high levels of low-glucosinolates (LG)-rapeseed meal of two varieties (Apex or Synergy) on ewes and lambs performances and circulating hormones (progesterone-P4, estradiol-E2,-prolactin-PRL, cortisol, insulin, tri-iodothyronin-T3, thyroxin-T4) and glucose. On the 100th day of gestation, 90 ewes bearing at least two foetuses were divided into 3 groups. Control, Apex and Synergy groups received concentrates with 0, 40 and 40% of LG-rapeseed meal obtained with either Apex (13.77 mumol of glucosinolates/g DM seed) or Synergy (18.19 mumol) variety. Apart from the distribution of pasture hay ad libitum, the ewes received 500 and 1200 g of concentrates/animal per day during gestation and lactation, respectively. Concentrates were offered till the 47th day of lactation, and thereafter, the ewes were fed only with hay during 3 weeks. The lambs received ad libitum concentrates without rapeseed meal from 10 days of age till slaughtering. They were weaned at 65 days of age and were slaughtered when their fattening state was optimal. The performances of ewes (food intake and liveweight profiles) and of lambs (birth liveweight, mortality at birth, weight gains, slaughtering parameters) were not reduced by 40% of LG-rapeseed meal except a decrease in the liveweight for ewes in the Apex group after lambing. The profiles and levels of plasma metabolic (T3, T4, cortisol, insulin) and reproductive (PRL, P4) hormones were not modified by the rapeseed meal. In contrast, the estradiol concentration was lower (P < 0.05) in the two groups of ewes which received rapeseed meal than in the controls as an index of an eventual disturbance in the reproductive functions. In conclusion, large amounts of LG-rapeseed meal may be used as protein supplement in the diet of ewes at the end of gestation and during lactation without negative effects on animal performances and physiology. (c( 2002 Published by Elsevier Science B.V.