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In the Northern Hemisphere, from June to September and in the Southern Hemisphere from December to March, there are periods of reduced fertility (sub-fertility) in dairy cows that are described as summer infertility. Several factors contribute to sub-fertility during this time, such as ambient temperature, humidity and photoperiod. During the warm season there is a reduction in feed intake that may compromise the energy balance of the cow and/or induce an imbalance in the activity of the hypothalamo-hypophyseal-ovarian axis. These factors reduce the reproductive performance of the cow and compromise the quality of oocytes, embryos and corpora lutea. This paper reviews current knowledge on the metabolic and endocrine mechanisms that induce summer infertility and describe their effects on follicle, oocyte and embryo development in dairy cows.

We have previously demonstrated that a constant intravenous infusion of kisspeptin (Kp) for 48 h in anestrous ewes induces a preovulatory luteinizing hormone (LH) surge followed by ovulation in approximately 75% of animals. The mechanisms underlying this effect are unknown. In this study, we investigated whether Kp-induced preovulatory LH surges in anestrous ewes were the result of the general activation of the whole gonadotropic axis or of the direct activation of central GnRH neurons required for the GnRH/LH surge. In the first experiment, a constant iv infusion of ovine kisspeptin 10 (Kp; 15.2 nmol/h) was given to 11 seasonally acyclic ewes over 43 h. Blood samples were taken every 10 min for 15 h, starting 5 h before the infusion, and then hourly until the end of the infusion. We found that the infusion of Kp induced a well-synchronized LH surge (around 22 h after the start of the Kp infusion) in 82% of the animals. In all ewes with an LH surge, there was an immediate but transient increase in the plasma concentrations of LH, follicle-stimulating hormone (FSH), and growth hormone (GH) at the start of the Kp infusion. Mean (+/- SEM) concentrations for the 5-h periods preceding and following the start of the Kp infusion were, respectively, 0.33 +/- 0.09 vs 2.83 +/- 0.49 ng/mL (P = 0.004) for LH, 0.43 +/- 0.05 vs 0.55 +/- 0.03 ng/mL (P = 0.015) for FSH, and 9.34 +/- 1.01 vs 11.51 +/- 0.92 ng/mL (P = 0.004) for GH. In the first experiment, surges of LH were observed only in ewes that also had a sustained rise in plasma concentrations of estradiol (E(2)) in response to Kp. Therefore, a second experiment was undertaken to determine the minimum duration of Kp infusion necessary to induce such a pronounced and prolonged increase in plasma E(2) concentration. Kisspeptin (15.2 nmol/h) was infused for 6, 12, or 24 h in seasonally acyclic ewes (N = 8), and blood samples were collected hourly for 28 h (beginning 5 h before the start of infusion), then every 2 h for the following 22 h. Kisspeptin infused for 24 h induced LH surges in 75% of animals, and this percentage decreased with the duration of the infusion (12 h = 50%; 6 h = 12.5%). The plasma concentration of E(2) was greater in ewes with an LH surge compared to those without LH surges; mean (+/- SEM) concentrations for the 5-h period following the Kp infusion were, respectively, 2.23 +/- 0.16 vs 1.27 +/- 0.13 pg/mL (P < 0.001). Collectively, our results strongly suggest that the systemic delivery of Kp induced LH surges by activating E(2)-positive feedback on gonadotropin secretion in acyclic ewes.

International audience; Two experiments were conducted to determine if nutritional supplementation improved ovulation and pregnancy rates in female goats managed under grazing conditions and submitted to the male effect. In Experiment 1, one group of does did not receive nutritional supplementation, while the other group was supplemented daily for 7 days starting at the time when the males were introduced to the females. The ovulation rate at the second male-induced ovulation was greater(P < 0.05) in supplemented (2.0 +/- 0.1) than in non-supplemented (1.6 +/- 0.1) does. For Experiment 2, female goats were supplemented for 0, 7,14 or 28 days, starting 9 days following buck introduction. The proportion of does that were pregnant in the group supplemented for 28 days was greater (P < 0.05) than in the non-supplemented group. but did not differ from 14-day and the 7-day supplemented groups. The proportion of pregnant does was greater (P < 0.05) in the group supplemented for 14 days compared to the group supplemented for 7 days and the non-supplemented group. These latter two groups did not differ (P > 0.05). In conclusion, feed supplementation for 7 days, starting at the time when males were introduced increased ovulation rate and feed supplementation for 14 or 28 days starting 9 days after males were introduced improved pregnancy rates in goats managed under grazing conditions and exposed to males. (C) 2009 Elsevier BY. All rights reserved.

Arterio-venous (A-V) difference techniques were used in cattle to examine ovarian energy metabolism, cholesterol uptake and steroid hormone outputs. Catheters were inserted into the ovarian vein and facial artery, and Transonic flow transducers were placed around the ovarian A-V plexus. Further, in some cows, the effects of a challenge with GnRH were examined. Glucose uptake and lactate output were significant in most individual cows. Nonesterified fatty acids (NEFA) uptake were not significant in any cow in dioestrus. Ovarian uptake of β-Hydroxy-butyrate (3-OHB) was significant in 4 cows in dioestrus. Cholesterol uptake was significant in only 1 cow. Oxygen uptake was significant in all cows at all stages of the oestrous cycle. All cows had significant output of progesterone and oestradiol-17β. These data show that the bovine ovary utilises significant amounts of glucose, and Respiratory quotient (RQ) estimates demonstrated that glucose was the primary fuel used by the ovary. The significant output of lactate suggested that anaerobic pathways were mainly used for glucose oxidation. The observed uptakes of 3-OHB indicated that the ovary utilises 3-OHB as a source of energy. Cholesterol uptake was not a rate-limiting factor for steroid hormone production in the ovary. Despite the high metabolic rate in the luteal ovary, the small difference in PO2 between arterial and ovarian venous blood indicated that the ovary consumes only a small proportion of available oxygen. GnRH had no significant effect on the uptake of metabolites and energy metabolism, but it increased OBF and the output of progesterone and oestradiol-17β. The use of A-V methods to determine the metabolic needs of the ovary is useful in understanding the means by which nutrition can influence fertility.

Ewes were actively immunized against androstenedione-11-BSA, androstenedione-7-HSA and testoster-one-3-BSA. Antibody titre was monitored and, when necessary, maintained by booster immunizations. The effects of these immunizations on ovulation and oestrous cycles were investigated. Immunization against androstenedione-11-BSA or androstenedione-7-HSA increased ovulation rate (2.2 and 1.6, respectively) compared to control ewes (1.2). Immunization against testosterone-3-BSA produced an anovulatory state in most ewes, but increased ovulation rate in those ewes still ovulating. The oestrous cycle was not significantly altered by immunization against androstenedione, but was abolished in 4/5 ewes immunized against testosterone. Gonadotrophins were measured in jugular venous plasma taken from ewes immunized against androstenedione-11-BSA and testosterone-3-BSA. The circulating levels of LH were elevated in all immunized ewes, while FSH levels were either reduced (androstene-dione-immunized) or unchanged (testosterone-immunized). These results suggest that neutralization of most of the biological activity of androgens produces alterations in hypothalamic-pituitary-ovarian relationships, and/or in the incidence of follicular atresia. These changes can increase ovulation rate, but in their more extreme form they can also cause anovulation. It appears that ovarian androgens, acting either directly or indirectly as oestrogen precursors, are important components of the hypothal-amic-pituitary-ovarian axis in the ewe.

Summary Sheep immunized with Fecundin and mated in the autumn have increased ovulation and lambing rates. The use of Fecundin immunization in association with other techniques for the control of reproduction was evaluated in a series of experiments. Ovulation rates can also be increased by exogenous gonadotrophins, and this effect was found to be additive with the effect of Fecundin on ovulation rate. Combined treatment of Fecundin and superovulatory doses of exogenous gonadotrophin did not, however, increase the number of ‘healthy’ embryos recovered from Merino ewes when compared to the use of gonadotrophins alone. Fecundin was shown to improve the lambing performance of spring-mated Border Leicester x Merino ewes, induced to ovulate using a combined progestagen-PMSG treatment. The time interval between booster immunization and ovulation should be about 3 weeks for optimum results. Three methods of oestrous synchronization were compared in Fecundin-treated ewes and found to have no influence on the ovulation rate response to fecundin. The use of Fecundin in conjunction with methods of oestrous synchronization and progestagen-PMSG treatment would appear compatible. However the use of Fecundin to enhance the superovulatory response to exogenous gonadotrophins requires additional evaluation in view of apparent breed effects.

The secretion rate of oestradiol and the peripheral concentration of luteinizing hormone (LH) were measured during anoestrus in six Merino cross ewes. The basal concentration of LH remained low (

This chapter discusses active immunization against steroid hormones for increasing fecundity. The use of immunological methods to modify normal physiological states by inducing autoimmunity has been attempted with varying degrees of success for a number of hormones. The scope for using the immune system to modify animal production is already quite wide, and will probably increase as knowledge of endocrine function increases. The techniques of immunophysiological regulation of animal production developed at present are capable of considerable refinement; nevertheless their potential justifies the current widespread interest in them. The chapter focuses on studies of the immunophysiological manipulation of ovulation rate and lambing rate by steroid immunity. It considers some practical aspects of fecundity stimulation. A review of mechanistic aspects of the response is given to describe effects of steroid immunity on: (1) follicle growth and development, (2) circulating hormones, (3) periovulatory events, and (4) embryo wastage and sex ratio phenomena.

This paper is concerned with the effect of androgen immunity on the expression of ovulation rate in the two important domestic ruminants, sheep and cattle. In the case of sheep the paper will review the development of a commercial vaccine (Fecundin®; Polyandroalbumin, Glaxo (Australia) Pty. Ltd.) which increases the numbers of lambs born to treated ewes. In the case of cattle, three experiments that have explored the ovulation rate response to active androgen immunity will be reported. The data will allow for some important comparisons to be made between the two species.