Alterations to the metabolic environment in utero can have an impact on subsequent female reproductive performance. Here, we used a model of rabbits receiving a high-fat diet (H diet; 7.7% fat and 0.2% cholesterol) or a control diet (C diet; 1.8% fat, no cholesterol) from 10 weeks of age up to mating at 27 weeks and throughout gestation and lactation. At weaning at 5 weeks of age, F1 female offspring were placed on either C or H diet, resulting in a total of four groups C/C, C/H, H/C and H/H diet. Female offspring were mated between 18 and 22 weeks of age and euthanized at 28 days of gestation. A few days before mating and/or just before euthanasia, F1 female rabbits were fasted overnight, weighed, and blood sampled for steroids and biochemistry. Organs were weighed at euthanasia and the ovaries were collected. C/H and H/H F1 offspring had higher cholesterol and high-density lipoprotein plasma concentrations, together with a higher fat mass compared with C/C does, reflecting the effect of the postnatal diet; however, no effect of the antenatal diet was observed on most parameters. The number of primordial, primary and secondary follicles were not different between the groups, but a significantly higher number of atretic follicles was observed in the C/H (P<0.001) and in the H/C (P<0.001) compared with control C/C ovaries, demonstrating both an effect of prenatal and postnatal maternal nutrition. These data indicated that both maternal and postnatal high-fat diet may induce follicular apoptosis; however, in this model, the reproduction was not affected.

Nerve growth factor (NGF) is a prototype member of the neurotrophins family and has important functions in the maintenance of viability and proliferation of neuronal and non-neuronal cells, such as certain ovarian cells. The present review highlights the role of NGF and its receptors on ovarian follicle development. NGF initiates its multiple actions through binding to two classes of receptors: the high affinity receptor tyrosine kinase A (TrkA) and the low-affinity receptor p75. Different intracytoplasmic signalling pathways may be activated through binding to NGF due to variation in the receptors. The TrkA receptor activates predominantly phosphatidylinositol-3-kinase (PI3K) and mitogenic activated protein kinase (MAPK) to promote cell survival and proliferation. The activation of the phospholipase type Cγ (PLCγ) pathway, which results in the production of diacylglycerol (DAG) and inositol triphosphate (IP3), culminates in the release of calcium from the intracytoplasmic cellular stocks. However, the details of activation through p75 receptor are less well known. Expression of NGF and its receptors is localized in ovarian cells (oocyte, granulosa, theca and interstitial cells) from several species, which suggests that NGF and its receptors may regulate some ovarian functions such as follicular survival or development. Thus, the use of NGF in culture medium for ovarian follicles may be of critical importance for researchers who want to promote follicular development in vitro in the future.

Relatively little information is available on the local factors that regulate folliculogenesis in goats. To examine the possibility that the Kit ligand (KL) system is expressed throughout the folliculogenesis, we studied the presence and distribution of KL and its receptor, c-Kit, in goat ovaries. Ovaries of goats were collected and either fixed in paraformaldehyde for immunohistochemical localization of KL and c-Kit proteins, or used for the isolation of follicles, luteal cells, surface epithelium and medullary samples to study mRNA expression for KL and c-Kit, using the reverse transcriptase polymerase chain reaction (RT-PCR). KL protein and mRNA were found in follicles at all stages of development, i.e. primordial, primary, secondary, small and large antral follicles, as well as in corpora lutea, surface epithelium and medullary tissue. Antral follicles expressed both KL-1 and KL-2 mRNAs, while earlier staged follicles expressed KL-1 transcript only. KL protein was demonstrated in granulosa cells from the primordial follicle onward. Its mRNA could be detected in granulosa cells isolated from antral follicles and occasionally in their theca cells. c-Kit mRNA was expressed in all antral follicular compartments and at all stages of follicular development. c-Kit protein was predominantly found in oocytes from the primordial follicle stage onwards, in theca cells of antral follicles, as well as in corpora lutea, surface epithelium and medullary tissue, particularly in the wall of blood vessels, which may indicate these cells as the main sites of action of KL. It is concluded that the KL/c-Kit system, in goat ovaries, is widespread and that it may be involved in the regulation of various local processes, including folliculogenesis and luteal activity.

To examine the possibility that epidermal growth factor (EGF) and its receptor (EGF-R) are expressed throughout folliculogenesis, we studied the presence and distribution of EGF and EGF-R in goat ovaries. Ovaries of goats were collected and either fixed in paraformaldehyde for immunohistochemical localization of proteins, or used for the isolation of follicles, luteal cells and ovarian surface epithelium to study mRNA expression for EGF and EGF-R, using the reverse transcriptase polymerase chain reaction. EGF protein and mRNA were found in primordial, primary and secondary follicles as well as in small and large antral follicles and in surface epithelium, but in corpora lutea only the protein could be detected. Antral follicles expressed EGF mRNA in oocyte, cumulus, mural granulosa and theca cells. For EGF-R, both protein and mRNA were present at all stages of follicular development and in all antral follicular compartments. EGF-R protein and mRNA were also found in corpora lutea and surface epithelium. It is concluded that EGF and its receptor are expressed in goat ovarian follicles at all stages of follicle development, in corpora lutea, and in ovarian surface epithelium.

In this investigation we tested the hypothesis that static body condition (BC) of the ewe affects oestradiol and FSH with implications for subsequent follicular growth and turn-over. Sixteen Polwarth ewes were selected from a flock according to their BC score (scale: 1 emaciated; 5 obese). High BC (HBC) ewes (no. = 8) had a BC score of 4·1 (s.e. 0·1) and low BC (LBC) ewes (no. = 8) had a BC score of 1·9 (s.e. 0·1). Daily ultrasound examinations were performed and blood samples for progesterone, oestradiol and follicle-stimulating hormone (FSH) determination were collected. All HBC ewes (8/8) exhibited three waves of follicular development, while four LBC ewes (4/8) had two waves and the other four (4/8) had three waves of follicular development (P ≤ 0·05) during the interovulatory period. Overall, the emergences of 33 out of 44 follicular waves were preceded by significant increases in FSH concentrations. Maximum FSH concentrations were detected 0·9 ± 0·2 days before wave emergence. Oestradiol concentrations increased significantly during the growing phase in 38 out of 44 large follicles. A negative correlation between oestradiol and FSH was observed in HBC ewes. A similar inhibitory effect of oestradiol on FSH was observed in LBC ewes, irrespective of whether they developed two or three follicular waves. However, a longer period with high FSH was needed to promote the emergence of the second follicular wave in two-wave LBC ewes. Four HBC ewes had twin ovulations but no LBC ewes did (P ≤ 0·05). In HBC ewes, the follicular phase was characterized by lower oestradiol (6·5 (s.e. 1·0) pmol/l) but higher mean FSH concentrations (2·4 (s.e.0·4) μg/l) than in LBC ewes (8·9 (s.e. 1·2) pmol/l and 2·0 (s.e. 0·3) μg/l, respectively; P ≤ 0·05). The present results suggest that BC influences the pattern of follicular dynamics through changes in the endocrine milieu. Higher FSH concentrations during the follicular phase in HBC ewes, which allowed an extended period of follicular recruitment from a significantly larger pool of small antral follicles could explain the higher ovulation rate observed in this group.

A comparison was made of various devices to obtain preantral follicles from bovine ovaries. The most productive collection methods in terms of number of follicles obtained were the tissue chopper and the grinder method, with an average number of 122·25 (s.e. 5·06) and 120·45 (s.e. 6·89) preantral follicles, respectively. These were followed by ficoll gradation (119·90, s.e. 7·95), mincer (101·75, s.e. 3·98), cell dissociation sieve (100·50, s.e. 3·42) and homogenizer (95·75, s.e. 6·38). For enzymatic digestion, more time was needed and the method was less productive. Microdissection could supply good quality (80% live when collected), larger sized follicles (120 to 220 µm) but with the lowest yield (10·65, s.e. 0·94) per ovary. The isolated follicles did not show any difference (P > 0·05) in viability until day 7 of in-vitro culture irrespective of method used to harvest follicles. Accordingly the new grinding device can be recommended as a replacement for the existing mechanical devices as it can yield the same percentage (47%) of live preantral follicles but of a wider diameter range (40 to 180 µm) per ovary.

The aim was to examine statistically the changes among days in the numbers of follicles relative to the growth of large follicles to test the hypothesis that follicular development occurs in a wave-like fashion in anoestrous ewes. The relationships among the patterns of circulating concentrations of FSH, oestradiol and inhibin-A and the pattern of follicular growth as well as relationships among follicular fluid steroid and inhibin-A concentrations were also studied. The ovaries of 11 ewes were examined daily using transrectal ultrasonography for 14 days and blood samples were collected every 8 h for 9 days. Five ewes were ovariectomized on the last day of ultrasound scanning. One to three identified follicles (a cohort) emerged every 2 to 5 days (mean 2·9 (s.e. 0·2) days) in individual ewes. The numbers of 4 and 5 mm follicles were fewest (P < 0·05) before and greatest (P < 0·05) 1 day after cohort emergence. This change in the numbers of follicles indicates a wave-like pattern of follicular growth. FSH concentrations were greatest (P < 0·05) on the day before wave emergence and lowest (P < 0·05) on the day of wave emergence. Peripheral concentrations of oestradiol and inhibin-A did not fluctuate (P > 0·05) in association with the emergence of follicular waves. The follicles that were collected at ovariectomy originated from one of three different waves. Oestradiol and inhibin-A concentrations in follicular fluid and the oestradiol-to-progesterone ratio were not different among the largest follicles of successive waves, when follicles were collected at the same time, indicating that new waves of follicles developed before the demise of old waves.

In conclusion, waves of follicles emerged about every 3 days in anoestrous ewes (defined as significant changes in numbers of follicles) and were associated with fluctuations in FSH concentrations but not peripheral oestradiol or inhibin-A concentrations. New follicular waves also emerged in the presence of steroidogenically active (positive oestradiol-to-progesterone ratio), inhibin-A producing follicles from a previous wave suggesting that follicles do not exert functional dominance during the non-breeding season.

The effect of recombinant bovine FSH (rbFSH) administration on serum FSH and follicular growth was determined in 16 GnRH-immunized heifers (primary day 0 and booster day 28 using 0·4 mg human serum albumin (HSA) – Cys-Gly-GnRH in DEAE-dextran). All heifers produced GnRH antibody titres (mean 58·8 (s.e. 2·8)% binding at 1: 640 serum dilution on day 42), follicular growth ceased (follicles ≤ 4 mm) between days 33 and 49, progesterone concentrations were ≤ 0·5 ng/ml in all heifers by day 53, and pulsatile LH secretion was markedly reduced (v. luteal phase control heifers) on day 63. Heifers were blocked by antibody titre and LH concentrations on day 63 and assigned (no. = five or six per treatment) on day 78 to: (1) control (saline given i.m. four times per day for 4 days), (2) 0·5 mg equivalent (USDA bFSH BP 1) of rbFSH (Granada Biosciences, TX) given i.m. four times per day for 6 days (12 mg in total) or 3) 1·5 mg rbFSH given i.m. four times per day for 4 days (24 mg in total). Ovaries of heifers were examined by ultrasound and blood samples were collected at 3- to 6-h intervals from days –1 to 10 and then twice a day until follicles ≥ 5 mm were no longer detectable. The increase in serum FSH concentrations was different (P < 0·05) between treatments (mean peak FSH above pre-treatment baseline concentrations at 102 h after first rbFSH were 1·4 (s.e. 0·8), 14·5 (s.e. 3·3) and 33·6 (s.e. 5·3) ng/ml for treatments 1 to 3, respectively). The rate of decline in FSH from 102 to 302 h was not different between treatments 2 and 3. There was no detectable follicular growth in heifers given saline injections. Following either rbFSH treatment, medium (MF; 5 to 9 mm) and large (LF; ≥ 10 mm) follicles grew. For heifers in treatments 2 and 3, there was no difference in the interval from start of rbFSH until the first appearance of MF (4·2 (s.e. 0·7) v. 3·3 (s.e. 0·3) days) or LF (5·3 (s.e. 0·3) v. 4·8 (s.e. 0·8) days) or in the duration of the presence of MF and/or LF (13·2 (s.e. 4·5) v. 16·6 (s.e. 2·6) days). Increasing dose of rbFSH increased (P < 0·05) the mean maximum number of MF (4·3 (s.e. 1·1) and 9·2 (s.e.0·9) for treatments 2 and 3) and LF (2·0 (s.e. 1·1) and 8·4 (s.e. 1·2)). In summary, low doses of rbFSH induced a small cohort of follicles to grow and develop without selection or development of a single dominant follicle, whereas high doses of rbFSH resulted in large numbers of both MF and LF.

The rôle of various classes of nutrients (energy substrates, vitamins, minerals, amino acids) in the production of wool and hair from follicles, is considered for a variety of animal species. The wool and hair follicle have evolved a number of interesting features of carbohydrate metabolism including glutaminolysis, aerobic glycolysis, significant activity of the pentose phosphate pathway, and storage and mobilisation of glycogen. Presumably the necessity to continue to produce fibre despite fluctuations in the supply of oxygen and nutrients has resulted in some of these unique features, while others reflect the high level of DNA and protein synthesis occurring in the follicle. While it is considered that energy does not normally limit fibre growth, the relative contributions of aerobic and anerobic metabolism will greatly influence the amount of ATP available for follicle activity, such that energy availability may at times alter fibre growth. Alopecia and deficient fibre growth are consistent outcomes of deficiencies of biotin, riboflavin, pyridoxine, folate and pantothenic acid, but the precise rôles of these vitamins in follicle function await elucidation. Folate, in particular appears to play an important rôle in wool production, presumably reflecting its involvement in methionine metabolism. Cholecalciferol (vitamin D) significantly alters fibre growth in cultured follicles; vitamin D receptors are located in the outer root sheath, bulb, and dermal papilla of the follicle; and alopecia occurs in humans with defects in the vitamin D receptor. Retinol (vitamin A), too, appears to influence follicle function by altering keratinocyte proliferation and differentiation, with direct effects on the expression of keratin genes. The receptors for the retinoids are present in the keratogenous zone, the outer root sheath, the bulb, and the sebaceous glands. Vitamin A may also act indirectly on follicle function by influencing the activity of the insulin-like and epidermal growth factors and by altering vitamin D activity. At present there is little evidence implicating alpha-tocopherol (vitamin E) or phytylmenaquinone (vitamin K) in follicular events. Of the minerals, only copper and zinc have been shown to have direct effects on follicle function, independent of effects on food intake. Copper has direct effects on the activity of an unidentified enzyme on oxidation of thiol groups to form disulphide linkages. Wool produced by copper-deficient sheep lacks crimp, is weak and lustrous. Copper is also necessary for the activity of tyrosinase and the tyrosinase-related proteins involved in melanin synthesis. Zinc, like copper, is required for the normal keratinization of fibres but again, the precise rôle has yet to be elucidated. While the importance of amino acid supply for wool growth has long been established, there are still some unaswered questions such as; what are the effects of amino acids on fibre growth in animals other than sheep; what are the characteristics of the amino acid transport genes and proteins operating in the wool and hair follicle; and what are the specific rôles for amino acids in follicle function.

Development of all follicles with antral diameter ≥2 mm during the oestrous cycle was characterized in goats of the Murciana-Granadina dairy breed by daily transrectal ultrasonography. Of nine does initially synchronized in oestrus, six returned to oestrus and three did not. In the first six does, mean cycle length was 21·2 (s.e. 2-3) days. There were mean total numbers of 6·2 (s.e. 0·6) small (2 to 3 mm), 1·9 (s.e. 0·3) medium (4 to 5 mm), and 1·0 (s.e. 0·2) large follicles (≥6 mm) each day but only numbers of large follicles differed with day of cycle (P < 0·01). The diameters of the largest follicle (LF1), the second largest (LF2) and the remaining follicles (RF) varied with day of cycle (P < 0·01). The LF1 and LF2 varied with day in similar patterns but the difference in diameter between them (P < 0·05) was greatest on days 7 and 9 (2·3 mm) and days 19 to 23 (2·2 to 3·8 mm), and least on days 2, 15, 16 and 18 (0·5 to 0·8 mm). The relationship between the LF1 and LF2 to the RF differed only early or late in the cycle when concentrations of progesterone were low (P < 0.05). There was some evidence to support follicular growth in waves. Although the number of apparently new follicles detected (4·8 (s.e. 0·4) per day) did not vary with day of cycle, follicles emerging at 3 mm over a 48-h period that grew to a diameter of ≥6 mm were distributed non-randomly in three of six cyclic does. The three cystic does that did not return to oestrus by day 25 had large follicles (16 to 28 mm), fewer new follicles (3·3 (s.e. 1-1) per day; P < 0·01) than cyclic does (4·8 (s.e. 0·4) per day) and fewer follicles that became largest (4·0 v. 8·8 in cyclic does; P < 0·01).

Artificial insemination, superovulation and embryo transfer have had beneficial impacts on animal production but a limiting factor to realizing the full potential of these techniques and of other reproductive technologies is the availability of fertile oocytes. To overcome this problem, methods for maturing oocytes in vitro (IVM) have been developed. The production of bovine embryos by IVM is in commercial use but the rate of success and quality of embryos is low. The lack of success may be due to the quality of oocytes that are being matured and it would be preferable to utilize the abundant source of immature oocytes from preantral and primordial follicles by developing systems for in vitro growth (IVG). Several culture systems that utilize early growing follicles as a source of oocytes have been developed for laboratory species and these have been successful in producing live young. IVG in association with IVM and cryopreservation have the potential to maximize the genetic potential of high genetic merit females and shorten generation intervals. This paper presents the current status of technology for the in vitro growth and development of immature oocytes, in vitro maturation and cryopreservation of germ cells in domestic ruminants.

This review addresses the reasons for the lack of progress in the control of superovulation and highlights the importance of understanding the mechanisms underlying follicular development. The present inability to provide large numbers of viable embryos from selected females still restricts genetic improvement, whilst variability in ovarian response to hormones limit the present capacity for increasing reproductive efficiency.

Females are born with a large store of eggs which rapidly declines as puberty approaches. If these oocytes are normal then there is scope for increasing the reproductive potential of selected females. Oocytes must reach a certain size before they can complete all stages of development and the final changes that occur late in follicular development. It is likely that oocytes that do not produce specific factors at precise stages of development will not be viable. Hence, it is important to characterize oocyte secreted factors since there are potential indicators of oocyte quality.

The mechanisms that determine ovulation rate have still not been fully elucidated. Indeed follicular atresia, the process whereby follicles regress, is still not known. A better understanding of these processes should prove pivotal for the synchronization of follicular growth, for more precise oestrous synchronization and improved superovulatory response.

Nutrition can influence a whole range of reproductive parameters however, the pathways through which nutrition acts have not been fully elucidated. Metabolic hormones, particularly insulin and IGFs, appear to interact with gonadotrophins at the level of the gonads. Certainly gonadotropins provide the primary drive for the growth of follicles in the later stages of development and both insulin and IGF-1, possibly IGF-2, synergize with gonadotrophins to stimulate cell proliferation and hormone production. More research is required to determine the effects of other growth factors and their interaction with gonadotropins.

There is evidence, particularly from studies with rodents, that steroids can also modulate follicular growth and development, although information is very limited for ruminants. There may be a rôle for oestrogens in synchronizing follicular waves, to aid in oestrous synchronization regimes and for removing the dominant follicle to achieve improved superovulatory responses. However more information is required to determine whether these are feasible approaches.

Heritability for litter size is higher in sheep than in cattle. Exogenous gonadotropins are a commercially ineffective means of inducing twinning in sheep and cattle. Although there are differences in circulating gonadotropin concentrations, the mechanism(s) responsible for the high ovulation appear to reside essentially within the ovaries. The locus of the Booroola gene, a major gene for ovulation rate, has been established but not specifically identified. However sheep possessing major genes do provide extremely valuable models for investigating the mechanisms controlling ovulation rate, including a direct contrast to mono-ovulatory species such as cattle.

In conclusion, the relationship between oocyte quality, in both healthy follicles and those follicles destined for atresia, must be resolved before the future potential for increasing embryo yield can be predicted. In addition, a greater understanding of the factors affecting folliculogenesis in ruminants should ensure that the full benefits ensuing from the precise control of ovarian function are achieved. The improved use of artificial insemination and embryo transfer that would ensue from a greater understanding of the processes of folliculo genesis, coupled with the new technologies of genome and linkage mapping, should ensure a more rapid rate of genetic gain.

L'examen macroscopique, histologique et cytologique des ovaires de Barbus holotaenia adultes récoltés dans le bassin de la Luki entre juillet 1986 et septembre 1988 a permis de décrire six stades de développement des ovaires et sept stades au niveau des ovocytes et des follicules. Quelques conclusions biologiques et écologiques sont tirées de ces différentes observations. La fécondité individuelle partielle est comprise entre 0,005 et 0,018 ovocytes par kg de la masse du poisson.

Four groups of 20 Simmental cross heifers were actively immunized against human serum albumin (control, (C), androstenedione (A), a 30 amino acid synthetic fragment of porcine inhibin alpha (I) or A and I in combination (AI). At the time of the third and final antigen injection and again 2 weeks later, all animals were injected with synthetic prostaglandin F2α (PG) to synchronize oestrus. Concentrations of LH, FSH, insulin-like growth factor-1 (IGF-1) and inhibin (C and A heifers only) in serum samples collected twice daily during 3 days before the second PG injection and at 15-min intervals from 24 to 32 h after PG injection were determined. Two weeks later, all heifers were administered PG and ovariectomized 24 h later. Ovarian follicles were dissected from the stroma, measured and cultured in medium 199 for 2h at 37°C. Numbers of small (3·0 to 7·9 mm diameter) and large (>8·0 mm diameter) follicles were not significantly altered by any of the immunization treatments. Intrafollicular concentrations and secretion rates of oestradiol, testosterone, progesterone and inhibin, determined in vitro, were not affected by immunization. Intrafollicular IGF-1 concentrations were not affected; this hormone was not detectable in the culture medium. Intrafollicular concentrations of oestrogen and testosterone and secretion rates of all three steroids were greater (P < 0·05) in animals which had regressing corpora lutea at the time of ovariectomy. Of the animals that had dominant follicles, one of 17, one of 13, four of 19 and six of 15 in the C, A, I and AI groups, respectively, had two or more. Only the difference between AI and C cows in the incidence of dominant follicles was statistically significant (P < 0·05). Mean circulating concentrations of LH, and inhibin (C and A groups only) and mean LH pulse frequency and pulse amplitude were unaffected by treatment but FSH concentrations were higher in A (P < 0·001) and lower in AI and I heifers (P < 0·001) compared with C animals while IGF-1 concentrations were lower in A heifers (P < 0·001) and higher in AI heifers (P < 0·05) compared with C heifers. It is concluded that immunization against inhibin, either alone or in combination with immunization against androstenedione increased the incidence of multiple dominant follicles in heifers but did not increase their ovulation rate.

The histological characteristics of the skin of docked and undocked fat-tailed sheep were studied at 15-day intervals between birth and 90 days of age, then every 30 days until 180 days and every 3 months until 1 year of age. Data presented in this paper were recorded at birth, 30, 60, 120,180 and 360 days of age. The fleece characteristics were studied at 1·0,1·5 and 2·0 years of age.

The skin structure was similar in docked and undocked Rahmani sheep and did not differ from that of other breeds of sheep.

The effect of docking was significant at most ages of the study on internal diameter of primary follicles and on the external and internal diameters of secondary and on average diameters of wool follicles (P < 0·05). The effect of docking was highly significant on each of staple length and wool diameter.

The effect of recombinantly derived bovine somatotropin (bST) administration on wool follicle populations, wool growth and body growth was examined in young lambs. Romney × (Border Leicester × Romney) lambs were treated with bST at doses of 0·1 or 0·3 mg/kg live weight per day, or with excipient, commencing on the day of birth and continuing at weekly intervals until the last injection was given at 11 weeks of age. Concentrations of immunoreactive somatotropin in plasma were 19·2 (s.e. 2·1), 65·2 (s.e. 2·8) and 74·7 (s.e. 4·8) μgll in the control, low dose bST and high dose bST groups, respectively. Somatotropin treatment did not alter the density of primary (P) or secondary (S) follicles in the skin, or the S/P ratio, as measured by histological examination of mid-side skin biopsy samples at 14 weeks of age. Mid-side greasy and clean wool growth during weeks 2 to 14 of the study were increased (P < 0·05) in bST-treated lambs but treatment had no effect on wool growth during the immediate post-treatment period (weeks 14 to 22), or on yearling fleece weight or wool quality characteristics. Body growth was not altered by bST administration. It is concluded that bST treatment stimulates wool growth even in very young lambs but, contrary to the results of a previous study, does not alter the development of wool follicle populations.

One hundred and thirty crossbred gilts (Yorkshire × Duroc × Hampshire) were exposed to either natural (40 lux) or supplemental lighting (700 lux) beginning at 8 weeks of age. Gilts received supplemental lighting from 40-W flourescent bulbs from 05·15 to 09·00 h and 16·30 to 20·15 h from 9 September to 22 April. At 4 months of age, all gilts were exposed daily for 15 min to mature boars five times weekly. Twelve gilts from each group were slaughtered at 4, 5, 6 and 7 months of age. All gilts were bled from indwelling cannulas at 20-min intervals for 4 h the day preceding slaughter. In addition, blood samples were drawn weekly from 17 gilts in each group from 7 to 9 months of age and analysed for progesterone to determine age of puberty. Twelve of 17 gilts that received supplemental lighting reached puberty at 228 (s.e. 11) days of age whereas 11 of 16 gilts that received natural lighting reached puberty at 252 (s.e. 7) days of age (P = 0·07). No significant differences occurred in anterior pituitary gland weight or pituitary concentration of LH, mean concentrations of serum LH or number of LH secretory spikes between natural and supplemental-lighted gilts at each month (all P > 005). Concentration of oestradiol-17β and progesterone in follicular fluid was similar between treatment groups within months and follicular size (P > 0·05). Content of GnRH in the stalk-median eminence, preoptic area and hypothalamus proper were also similar between treatment groups (P > 0·05). In summary, supplemental lighting reduced the age of puberty in gilts without a detectable change in pituitary, hypothalamic or ovarian parameters.

Some factors affecting oviposition by Plodia interpunctella (Hubner) were studied under various controlled conditions in the laboratory. The effect of temperature, relative humidity, light and mating on oviposition were investigated.

Temperatures of 25 and 30°C were optimal for oviposition. The best condition was 30°C and 80% r.h. at which an average of 315.3 eggs were laid per female during its lifetime. The least favourable temperatures investigated were 15 and 35°C. Relative humidity did not have significant effect on the number of eggs laid at 15 and 25°C but at higher temperatures of 30 and 35°C, high r.h. increased the number of eggs laid by individual moths.

Light regimes of 12 hr light and 12hr darkness (LD) and 24 hr darkness (DD) were more favourable than 24 hr light (LL) for oviposition.

Virgin females laid fewer eggs than mated females while prolonged virginity reduced the number of eggs laid and caused resorption of immature oocytes and retention of ripe eggs in the ovaries.