Effect of long-term feeding with graded levels of low glucosinolate rapeseed meal on endocrine status of gilts and their piglets

Abstract Seventy-two crossbred gilts of approximately 30 kg initial weight were used in this study. The gilts were divided into three groups and fed with graded levels of low glucosinolate rapeseed meal (RSM) over grower–finisher, gestation and lactation periods as follows C (control: no RSM in diet during growth/pregnancy/lactation), M-RSM (medium RSM levels: 7/2.5/7% RSM in diet equivalent to 0.45/0.16/0.45 mM glucosinolates/kg diet) and H-RSM (high RSM levels: 12/5/12% RSM in diet equivalent to 0.78/0.32/0.78 mM glucosinolates/kg diet). In experiment 1, the jugular veins of six gilts taken randomly from each group were cannulated. Blood was sampled every 4 h over 2 days during the midluteal phase of the first oestrous cycle. Plasma concentrations of free thyroxine (FT 4 ), triiodothyronine (T 3 ), luteinizing hormone (LH), prolactin (PRL), progesterone (P 4 ) and androstenedione (A 4 ) were determined. After sacrificing, thyroid glands, ovaries and uteri were dissected and weighed, the lengths of the uterine horns were measured, and the numbers of corpora lutea (CL) were counted. Thyroid glands of gilts fed H-RSM diet were heavier ( P 4 decreased as the content of RSM in the diet increased. Plasma T 3 was lower ( P 4 was higher ( P 4 and PRL in gilts fed diets containing RSM were significantly lower than those in controls. There were no significant differences in mean levels of LH among groups. In experiment 2, the remaining 54 gilts were mated to study the reproductive performance and endocrine status of their offspring. Thirty female piglets were randomly chosen from different litters in each of the three groups on the 2nd and 35th day of lactation (five piglets/per group/per day). The piglets were sacrificed and blood was sampled from the heart. Thyroids, ovaries and uteri were dissected and weighed. Samples of blood serum were assayed for FT 4 , T 3 , LH and PRL. The weights of thyroids, ovaries and uteri in female piglets were similar in all groups. The serum concentrations of FT 4 , T 3 , LH and PRL were not affected by the treatment, irrespective of the age of piglets (2nd or 35th day). In summary, long-term feeding with graded levels of low glucosinolate rapeseed meal did not result in significant alterations in reproductive performance of gilts. The RSM diets, however, did affect the mean concentrations of plasma FT 4 , T 3 , PRL P 4 and A 4 in gilts during the midluteal phase of the first oestrus cycle. In contrast, no significant differences in serum concentrations of examined hormones were found in piglets originating from control and RSM groups.