Jean-Loup Bister

Influence of season and age on sexual maturation parameters of Texel, Suffolk and Ile-de-France rams: 1. Testicular size, semen quality and reproductive capacity.

Scrotal diameter, quantity and quality of semen and serving capacity of rams were compared using Texel, (Tx, n=6); Suffolk, (S, n=9) and Ile-de-France, (IDF, n=9), throughout the 2nd and 3rd years of age. Scrotal diameter increased rapidly during the 2nd year of age and grew slowly over the 3rd year, significantly (P<0.05) increasing in autumn and decreasing in winter and in spring during the 2nd and 3rd years of age. They were higher in IDF than in Tx (P<0.05), with S rams being intermediate. Volume and spermatozoa concentration of the first ejaculate were similar in rams of different ages and breeds. Unlike spermatozoa concentration, volume increased slightly in autumn and decreased in winter and spring in Tx and S, but not in IDF rams. The percentages of dead and abnormal spermatozoa decreased (P<0.01) with age of rams. Concentrations were lower in autumn and increased in winter and spring over the 3rd year of age for S and IDF rams (P<0.05). Sperm motility fluctuated independently of age and seasons. Semen quality, evaluated by both motility score and percentages of dead and abnormal spermatozoa, was better in IDF and S than in Tx rams, until the 27th month of age. Serving capacity increased (P<0.05) with age of rams and varied throughout the year, the lowest values being observed in spring and summer. Spermatozoa production evaluated by exhaustion test during the 3rd year of age was higher (P<0.05) in IDF than in the two other breeds on the days of spring equinox. In contrast, semen yield of Tx rams was the highest (P<0.05) on the days of autumn equinox and winter solstice. Frequent ejaculations lowered semen quantity and this effect varied among breeds throughout the seasons. In conclusion, scrotal diameter, serving capacity and dead or abnormal spermatozoa were better and seasonal changes more pronounced during the 3rd than during the 2nd year of age. An efficient spermatogenesis is established later in highly seasonal breeds, such as Texel, which seems related more to breed traits than to environmental factors.

Effects of FGA and PMSG on follicular growth and LH secretion in Suffolk ewes

The effects of fluorogestone acetate (FGA) and/or pregnant mare serum gonadotrophin (PMSG) on follicular growth and LH secretion in cyclic ewes were determined. Suffolk ewes (n=40), previously synchronized with cloprostenol were divided into 4 experimental groups (n=10 ewes per group). Group I served as the control, while groups II, III and IV received FGA, PMSG, FGA and PMSG respectively. Four ewes of each group underwent daily laparascopy for 17 d. All the ovarian follicles>or=2 mm were measured, and their relative locations were recorded on an ovarian map in order to follow the sequential development of each individual follicle. Comparisons were made of the mean day of emergence and the mean number of small, medium and large follicles, the atresia rate and the ovulation rate. For each group, 3 waves of follicular growth and atresia were observed during the cycle. During luteal phase, FGA treatment accelerated the mechanisms of follicular growth but reduced the number of large follicles and increased the atresia rate. In the follicular phase, FGA treatment was detrimental to both the number of large follicles and the ovulation rate. By contrast, PMSG enhanced recruitment of small follicles and the ovulation rate. Serial blood samples were collected during the luteal and follicular phases to study LH secretion. None of the treatments had any effect on LH secretion patterns.

Body weight, oestrous and ovarian activity in local Burundian ewes and goats after parturition in the dry season

To compare body weight losses and post-partum anoestrus, twelve local Burundian ewes and twelve goats which had lambed or kidded at the middle of the dry season were followed from parturition until eight months. Each dam was weighed every month and bled three times a week to assess the ovarian activity resumption by plasma progesterone (P4) profiles. For the two species, the body weight decreased significantly (P < 0.05) compared to the body weight at parturition. The mean time during which the body weight decreased was longer (P < 0.05) for the ewes (3.2 +/- 1.2 months) than for the goats (2.3 +/- 1.4 months), however, the relative body weight losses did not significantly differ. The time to oestrous and ovarian activity resumption was highly correlated to the body weight losses for the ewes (r = 0.81; P < 0.01 and r = 0.58; P < 0.05) not for the goats. The first oestrus preceded the first ovarian activity by 4 days in the goats, but occurred 36 days later in the ewes. Nevertheless, after the first luteal function, the subsequent ovarian activity was regular and normal in the ewes but not in the goats and in some cases a return to anoestrus could be observed. These data indicate that in the ewe, not in the goat, the body weight losses are one of the major limiting factors of the oestrous and ovarian resumption after parturition during the dry season. Moreover, the occurrence of luteal function does not initiate a regular reproductive cyclicity in the goat in contrast to the ewes.

Effects of suckling mode on endocrine control of reproductive activity resumption in Texel ewes lambing in July or November.

To study the effects of the overlapping of seasonal and lactation anestrus and the influence of the suckling mode on the resumption of reproductive activity in Texel ewes, two experiments were carried out after the July and November lambings. The frequency and the duration of suckling decreased with the age of the lambs, and the suckling intensity in the lambs that were allowed to suck unrestrictedly was three times higher than in lambs restricted to sucking three times a day. The overlapping of seasonal anestrus and lactation delayed the resumption of ovarian and estrus activity, but no difference was observed between dams suckling single lambs and twins. The resumption of ovarian and estrus activity was much earlier after the November lambing than after the July lambing. Weaning after the November lambing shortened the interval between parturition to first estrus but not to the first luteal function. The reduction of suckling intensity by suckling management had no effect on the resumption of ovarian and estrus activity. In early postpartum, suckling inhibited the luteinizing hormone (LH) pulsatile secretion and consequently the first LH discharge. However, the earlier restoration of gonadotropin stimulation in dry ewes was not immediately followed by ovarian activity. The suckling inhibition may be due to a temporary disturbance in hormonal balance, the rise in prolactin (PRL) and cortisol secretions. Plasma estradiol 17beta (E2) concentrations were higher in dry than in suckling ewes in early postpartum. Follicle stimulating hormone (FSH) secretion was not involved in the process of delaying the resumption of reproductive activity after lambing.

Chemical changes and influences of rapeseed antinutritional factors on lamb physiology and performance - 2. Plasma substances and activity of the thyroid

In order to study the effects of a high level of rapeseed meal in the diet on endocrine function and thyroid activity, sixty six Texel, Suffolk or crossbred lambs allocated to three groups were fed ad libitum with concentrates containing 0% (Control) or 25% of rapeseed meal obtained with either Samourai (Samourai) or Honk (Honk) rapeseed varieties. Lambs were weaned at 88 8 days of age and 24 5 kg of live weight and were slaughtered when their fattening state was estimated to be satisfactory. Blood samples were taken fortnightly for the determinations of hormones, glucose and transaminases (GOT and GPT). To evaluate the capacity of hormone production, the thyroid glands were collected at slaughter and the in-vitro release of thyroid hormones was recorded. The plasma concentrations in triiodothyronine (T3) and thyroxine (T4) decreased (P <0.05) with the age of lambs and were lower (P <0.05) in the Samourai and Honk groups than in the Control. Moreover, the capacity of T3 and T4 production by the thyroid gland shown by the in-vitro T3 and T4 accumulation in the thyroid tissues was higher (P <0.05) in the Control than in the two rapeseed groups. In contrast, the concentrate with rapeseed meal had no effect on the plasma concentrations in GH, cortisol and insulin nor on other substances (glucose, GOT and GPT). These results indicate that the ingestion of rapeseed meal induces a low functional disorder of the thyroid without affecting the animal performance of lambs, as we reported previously. This is because the thyroid hormones do not appear to play a major role in the processes of growth and

Chemical changes and influences of rapeseed antinutritional factors on lamb physiology and performance 1. Animal performance and thyroid histology

Sixty six Texel, Suffolk or crossbred lambs allocated to three groups were used. From the end of their first month of age till slaughtering, they were fed ad libitum with concentrates containing 0% (Control) or 25% of rapeseed meal obtained from either Samourai (Samourai) or Honk (Honk) variety. The Samourai and Honk concentrates contained 1.95 and 4.22 mmoles/g DM of glucosinolates, respectively. Lambs were weaned at 88 8 days of age and 24 5k g of live weight and were slaughtered when their fattening state was estimated to be optimal. Apart from low concentrate intake for suckling lambs at the beginning of the experiment in the Honk, no negative effect of low glucosinolates (LG)-rapeseed meal was noted concerning animal performance. The quality of perirenal fat was better for lambs which received rapeseed meal since lower (P < 0.5) proportions of saturated fatty acids (C10 : 0 ,C 12 : 0 ,C 14 : 0) and higher contents (P < 0.05) of some unsaturated fatty acids (C18 : 1trans ,C 22 : 2) were determined. The thyroid weight was significantly higher (P < 0.05) for the Honk (3.04 0.8 g) than in the Control (2.6 0.5 g) and the Samourai (2.7 0.6 g). Moreover, the percentages of small thyroid follicles were lower (P < 0.05) in the Honk than in the Control and Samourai groups. Conversely, the percentages of large thyroid follicles were higher (P < 0.05) in the Honk than in the two other groups. These results suggest that rapeseed meal can be used as the only protein supplement for fattening lambs despite the

Pre-ovulatory follicular characteristics and ovulation rates in different breed crosses, carriers or non-carriers of the Booroola or Cambridge fecundity gene

Terminal follicular dynamics and ovulation rates (OR) were compared in different local breeds after introducing fecundity genes of different origin. Crossbred ewes which were carriers (F+) or non-carriers (++) of Booroola (BFec) or Cambridge genes (CFec) were included: CambridgexCambridge (CC), CambridgexSuffolk (CS), CambridgexTexel (CT), BooroolaxTexel (BT) and BooroolaxGerman Mutton Merino (BGM). The numbers of small (diameter 2-3.5 mm), medium (diameter >3.5-5.0 mm) and large (diameter >5.0 mm) growing follicles, the maximum diameter before ovulation and the regression and artesia rates of ovarian follicles >/=2 mm in diameter were studied laparoscopically and repeatedly during the last 5 days of an induced oestrous cycle. The ORs were determined one cycle before and two cycles after the repeated laparoscopy. BFec and CFec significantly enhanced the OR of all crossbreeds. Carriers of BFec or CFec did not have significantly different ORs due to any crossbreeding effect. The same observation was made for non-carriers of both Fec gene types. Whatever the crossbreed, the number of small, medium and large growing follicles were similar between carriers and non-carriers in spite of a higher number of ovulating follicles in carriers of both Fec gene types. The diameter of ovulatory follicles did not differ among crossbreds, or between carriers and non-carriers except in the BT (5.2+/-0.2 vs. 6.5+/-0.8 mm, respectively) and CC (6.6+/-0.2 vs. 5.6+/-0.3 mm) ewes.The higher OR in the presence of the Booroola gene was associated with a low atresia rate of large follicles in all crossbreeds (BT: 52+/-8% (F+) vs. 61+/-7% (++); BGM: 51+/-6% vs. 75+/-5%). The high OR of the carriers of the CFec gene seemed to be associated with a lower number of large growing follicles with a lower (P<0.05) atresia rate as compared with Booroola crossbreeds. In conclusion, follicular features were similar between purebred Cambridge and its crossbred CS and CT. In ewes carrying the BFec or CFec gene, the reduction in follicular atresia seemed to be one of the main follicular features implicated in the higher OR.

Influence of season and age on sexual maturation parameters in Texel, Suffolk and Ile-de-France rams: 2. Circulating concentrations of follicle stimulating hormone, luteinizing hormone, prolactine and testosterone

Abstract Follicle stimulating hormone (FSH), prolactin (PRL), luteinizing hormone (LH) and testosterone (T) secretions were studied in six Texel (Tx), nine Suffolk (S), and nine Ile-de-France (IDF) rams throughout the second and third years of life. The weekly mean concentrations of plasma T and FSH were higher ( P P P P P P P P P

Effects of season and phase of the estrous cycle on steroidogenesis and LH-FSH sensitivity of large ovine follicles perfused in vitro

The aims of this study were to compare steroïdogenesis (progesterone, androstenedione and estradiol production) and response to LH and FSH challenge by whole perifused follicles 4 to 5.5 mm in diameter, obtained at different periods of the breeding season (onset, middle, end), during anestrus and the luteal phase. We have observed that all follicles do not have the same steroïdogenetic potential and do not respond with the same intensity to LH and FSH. At the middle of the breeding season, LH and FSH supplementation was ineffective in increasing progesterone secretion by follicles (0.19+/-0.05 vs. 0.20+/-0.03 ng/mL). In contrast, gonadotrophin challenge elicited significant (P<0.05) increases in androstenedione (0.94+/-0.34 vs. 0.35+/-0.09 ng/mL) and estradiol (120+/-11 vs. 49+/-10 pg/mL) production immediately after its administration. At the onset of the breeding season, steroidogenesis was identical under both basal and gonadotrophin-stimulated conditions unlike that in middle of the breeding season. However follicles were more sensitive to the gonadotrophin challenge in terms of estradiol production than those collected at the middle of the breeding season (220+/-45 vs. 120+/-11 pg/mL). Follicles obtained at the end of the breeding season featured higher progesterone (2.61+/-0.81 vs. 0.19+/-0.05 ng/mL; P<0.05) and lower estradiol production (10+/-3 vs. 49+/-10 pg/mL; P<0.05) that was not influenced by LH and FSH. Basal androstenedione secretion was comparable to that observed at the middle of the breeding season (0.42+/-0.10 vs. 0.35+/-0.09 ng/mL), but the response to stimulation was significantly higher (1.82+/-0.61 vs. 0.94+/-0.34 ng/mL; P<0.05). In anoestrus and the luteal phase, follicles presented higher progesterone and androstenedione and lower estradiol concentrations (P<0.05) compared with those obtained during the follicular phase at the middle of the breeding season. In the luteal phase, follicles remained capable of responding to LH-FSH challenge by increasing estradiol secretion (9+/-1 before and 21+/-6 pg/mL after LH-FSH; P<0.05). In contrast, in the luteal phase, estradiol production was not increased by LH-FSH challenge (7+/-2 vs. 12+/-4 pg/mL).

Effects of progesterone treatment on ovarian and estrous activity and on LH pulsatility and PGF2α concentration in suckling and non-suckling Texel ewes

Two experiments investigated the effects of low amounts of exogenous progesterone (P4) on the resumption of estrous and ovarian activity and on luteinizing hormone (LH) pulsatility and prostaglandin F2α (measured as 13,14-dihydro-15-keto-PGF2α, PGFM) concentrations in postpartum Texel ewes early after lambing. In Expt. 1, six single-suckling ewes received intravaginal devices containing 210 mg of native P4, from d 4 ± 2 to d 16 ± 2 after parturition during the breeding season, and six others served as controls. The P4 supplementation induced earlier return to estrus in single-suckling ewes (23 ± 7 vs. 37 ± 3 d, P < 0.01) and was not associated with subsequent inadequate luteal function. Duration of the first luteal function was shorter in three of the six control ewes. LH pulse frequency (per 6 h) was decreased during the period of P4 supplementation and increased 1 d after removal of P4 devices (P < 0.01). Concentrations of PGFM were lower in P4-treated ewes than in the control group (P < 0.01). In Expt. 2, ewes either suckled one lamb or weaned soon after parturition and received intravaginal devices containing 210 mg of native P4 from d 16 ± 3 to d 28 ± 3 post partum. The incidence of estrous behavior after P4 supplementation was lower in suckling than in dry ewes (P < 0.01), while ovarian activity resumed to the same extent in both groups and was not associated with inadequate luteal function as in Expt. 1. The P4 treatment raised circulating P4 to higher levels in weaned than suckling ewes (P < 0.01). In both categories, LH pulse frequency was suppressed during the P4 treatment and increased 1 d after the P4 withdrawal (P < 0.01). Weaning reduced significantly plasma PGFM concentrations (P < 0.01). These results indicate that the positive effect of P4 on the re-establishment of hypothalamo-pituitary functions prevents the premature regression of the CL after lambing. They strongly suggest that P4 treatment reduces the interval between parturition and return to estrus and is more effective in dry than in suckling ewes.