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

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 grade d levels of low glucosinolate rapeseed meal (RSM) over grower-finisher, ges tation and lactation periods as follows C (control: no RSM in diet during g rowth/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 thigh RS M levels: 12/5/12% RSM in diet equivalent to 0.78/0.32/0.78 mM glucosinolat es/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 d uring the midluteal phase of the first oestrous cycle. Plasma concentration s of free thyroxine (FT4), triiodothyronine (T-3), luteinizing hormone (LH) , prolactin (PRL), progesterone (P-4) and androstenedione (A(4)) were deter mined. After sacrificing, thyroid glands, ovaries and uteri were dissected and weighed, the lengths of the uterine horns were measured, and the number s of corpora lutea (CL) were counted. Thyroid glands of gilts fed H-RSM die t were heavier (P < 0.01) than those of control gilts. Diets: containing RS M did not affect ovarian and uterine weights, CL numbers or uterine horn le ngths. The mean plasma concentration of FT4 decreased as the content of RSM in the diet increased. Plasma T-3 was lower (P < 0.001) in gilts fed M-RSM diet and plasma P-4 was higher (P < 0.01) in gilts fed H-RSM diet compared to control animals. The concentrations of A(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 random ly 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 s acrificed and blood was sampled from the heart. Thyroids, ovaries and uteri were dissected and weighed. Samples of blood serum were assayed for FT4, T -3, LH and PRL. The weights of thyroids, ovaries and uteri in female piglet s were similar in all groups. The serum concentrations of FT4, 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 r eproductive performance of gilts. The RSM diets, however, did affect the me an concentrations of plasma FT4, T-3, PRL P-4 and A(4) in gilts during the midluteal phase of the first oestrus cycle. In contrast, no significant dif ferences in serum concentrations of examined hormones were found in piglets originating from control and RSM groups. (C) 2001 Elsevier Science B.V. Al l rights reserved.