The objective of this study was to determine the effect of treatment with additional progesterone (P4) or 17 beta-oestradiol (E2) at the end of a period of P4 treatment on ovarian follicular development, ovulation time, and plasma gonadotrophin and steroid hormone concentrations of Bos indicus cows. Initially, two injections of PGF2 alpha were given 14 days apart, and at the time of the second injection (Day 0) all cows received a single P4-releasing controlled internal drug release (CIDR) device that was removed 10 days later. Control cows (Group 1, n = 8) received no other treatment. On Day 8, cows in Group 2 (n = 8) and Group 3 (n = 8) received either a s.c. implant containing E2, or a second CIDR device, respectively. All CIDR devices and E2 implants were removed at a similar time on Day 10. Treatment with E2 or P4 delayed mean (+/- SD) time of ovulation (113.1 +/- 25.6 h, 153.4 +/- 44.5 h and 150.8 +/- 25.1 h for Groups 1, 2 and 3, respectively; P < 0.05) and the mean time (+/- SD) of the luteinising hormone (LH) peak (87.4 +/- 24.5 h, 124.3 +/- 45.0 h and 122.3 +/- 25.04 h for Groups 1, 2 and 3, respectively; P < 0.05). Both treatments delayed the mean (+/- SD) day of emergence of the ovulatory follicle (7.7 +/- 3.6 days, 11.3 +/- 1.7 days and 11.1 +/- 1.5 days for Groups 1, 2 and 3, respectively; P < 0.05), and reduced the variability in the day of emergence of the ovulatory follicle (P < 0.05) compared with the control cows. Variability in age and duration of dominance of the ovulatory follicle was greater in control animals compared with treated animals (P < 0.05). Treatment with E2 on Days 9 and 10 did not alter mean concentrations of gonadotrophins in the cows in Group 2 compared with control cows (P > 0.05), whereas treatment of cows with an additional CIDR device resulted in greater mean concentrations of FSH and lesser concentrations of LH on Day 9 (P < 0.05) compared with cows in Groups 1 and 2. By Day 10 mean concentrations of gonadotrophins were similar among cows in all three groups. Concentrations of E2 were less in cows in Group 3 compared with cows in Groups 1 and 2 from Day 9 to Day 11 (P < 0.05). We conclude that treatment with either E2 or P4 can influence the pattern of ovarian follicular development and ovulation in cattle; however, the mechanism of action of the two treatments may differ. Atretogenic treatments for ovarian follicles applied at the end of a period of progesterone treatment did not improve synchrony of ovulation.

Milk composition and the rates of milk consumption by pouch young were examined in free-living allied rock-wallabies, Petrogale assimilis. Milk solids concentrations were approximately 16% (w/w) at 70 days post-partum and increased to about 22% by 170 days when young first left the pouch. By permanent pouch emergence (about 200 days), concentrations had declined and stabilised at about 19%. Milk carbohydrate peaked at 12% (w/v) at 150 days; lipid concentrations averaged 8% (w/w) at 200 days. The subsequent decline in carbohydrates was the main cause of the fall in milk solids. Protein concentrations increased gradually from about 3% (w/v) at 70 days to plateau at 5.5% at about 200 days. Milk consumption rates were measured from 72 to 159 days post-partum with Na-22 turnover. Milk consumption, about 3 mL day(-1) initially, increased to an average of about 15 mL day(-1) by 150 days. The mass gained by a pouch young between 72 and 159 days for each millilitre of milk consumed was not correlated with lactational stage and averaged 0.21 +/- 0.014 (s.e.)g mL(-1).

The aims of the current study were to determine if the pattern of ovarian follicular growth and development in Bos indicus heifers is different to that reported in Bos taurus breeds, and to examine the factors that determine which dominant follicle will ovulate. In addition, the extent to which variation in follicular dynamics is attributable to variation between animals and over time was evaluated. The ovaries of 17 Brahman heifers were examined daily by transrectal ultrasonography using a 7.5 MHz transducer for a total of 117 interovulatory intervals over a period of 10 months. Size and position of individual follicles ⪖5 mm in diameter, and size of corpora lutea (CL) were recorded. Circulating progesterone concentrations were determined from plasma samples obtained twice weekly. Although size of dominant follicles and CL within the ovaries of Bos indicus heifers were smaller than reported for Bos taurus breeds, the overall patterns of dominant follicle growth were similar. There were significant correlations between number of dominant follicles occurring prior to ovulation and time of appearance of the second dominant follicle, duration of detection of CL and size of the ovulatory follicle in the preceding oestrous cycle (P < 0.05). There were significant animal effects on a number of ovarian characteristics including number of dominant follicles per oestrous cycle (P < 0.001), with one heifer having four dominant follicles in more than a third of oestrous cycles observed. In addition, changes in daylength over the 10 month period were related to changes in duration of the interovulatory interval, persistence and maximum diameter of CL and size of ovulatory follicles. Liveweight change over the same period was related to changes in maximum diameter of the first dominant follicle.

This study examined the effects of live mass on ovarian follicular dynamics in heifers before and after the onset of nutritional anoestrus. The effects of decreased live mass on secretion of progesterone, LH and FSH were also investigated. Ovarian characteristics were monitored in 16 postpubertal Brahman heifers using daily transrectal ultrasonography. After two normal oestrous cycles, 11 heifers (treatment group) were allocated to a restricted diet, until the cessation of their oestrous cycles, that resulted in a decrease in live mass of 0.8 kg day-1. Heifers were then fed an ad libitum diet, resulting in increasing live mass until resumption of oestrous cycles. Five heifers (control group) were fed an unrestricted diet throughout the experimental period. The concentrations of progesterone in plasma were monitored twice a week and the concentrations of LH and FSH were determined on day 6 after ovulation, before initiation of dietary restriction, after a 17% decrease in live mass and after the onset of anoestrus in the treatment group. Onset of anoestrus was preceded by linear decreases in the size of ovarian follicles and corpora lutea, and in the persistence of the first dominant follicles of oestrous cycles. These changes were proportional to the decrease in live mass (P < 0.001). The frequency of pulses of LH or mean concentration of FSH on day 6 of the oestrous cycle were not changed after a 17% decrease in live mass, and did not increase following the onset of anoestrus, although concentrations of progesterone were < 0.2 ng ml-1, suggesting that release of LH was suppressed at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

The precise nature of the allometric relationships between body size and body mass, water content and solid matter was derived from a sample of over 700 lizards of the agamid species Amphibolurus nuchalis (= Ctenophorus inermis), collected during 1969-82 at Shark Bay in Western Australia. Three condition indices relating each variable to body size, as expressed by snout-vent length, were derived from these allometric relationships for male, female and juvenile lizards. The formation of condition indices was compared to analysis of covariance as a method of analysis of such data. Variation in these indices with weather and season over the period of the study were investigated by means of regression models. Variation between days within trips was relatively small, suggesting a time scale for physiological change of greater than 3-4 days. Ascribing cause to specific weather and seasonal factors was difficult, due to the high colinearity of the explanatory variables. The influence of temperature and rainfall on the condition indices was evident in the model, however, and accords well with physiological data for this species. The extent to which the condition indices could be predicted by a combination of weather and seasonal variables was encouraging, and suggests that the method may have general utility in the study of changes in body composition and condition of free-ranging animals.

Generation time of S. sacchari females reared on potted cane ranged from 107 days at 20-degrees-C to 25 days at 30-degrees-C. Three models were fitted to developmental data. The linear model indicated a minimum threshold temperature of 17-degrees-C and the inverse polynomial model a maximum development rate at 30.4-degrees-C. Developmental response to temperature varied from that previously reported in Egypt and the Philippines. The largest and most fecund females were produced at 30-degrees-C. Net reproductive rate varied from 82.0 and 79.7 at 20 and 33-degrees-C respectively to 205.5 at 30-degrees-C. The intrinsic rate of natural increase (r(m) increased from 0.038 at 20-degrees-C to 0.186 at 30-degrees-C. The value of the common shape parameter of the Weibull distribution used to describe adult survivorship curves was 3.5, indicating type I survivorship curves. The ovipositional threshold (V0) was estimated as 16.5-degrees-C. The rate of development of individuals had a major influence on fecundity, both directly and indirectly, through adult female size and the duration of the oviposition period. The ability of S. sacchari to produce large individuals with high fecundities when corresponding rates of development were highest give this tropical species a capacity for rapid population growth at high temperature.

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SummaryThe lateral spread of Gigaspora calospora (Nicol. and Gerd.) Gerdemann & Trappe was examined in Trifolium subterraneum L. (subterranean clover) grown on a steamed lateritic podsol. Plants were sown in a sward in pots 29 cm long × 12 cm wide and inoculum of G. calospora was placed at one end. Mycorrhizal infection was estimated 21, 35, 63, 91 and 119 d after sowing at points 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 and 26 cm from the inoculum. The lateral spread of Glotnusfasciculatum (Thaxter sensu Gerd.) through roots of T. subterraneum was measured 35 d after sowing.The percentage root length infected by G. calospora declined exponentially with distance from the inoculum. In contrast, infection by G. fasciculatum spread with a distinct front and hence was best described by a Gompertz curve.The number of spores of G. calospora recovered at increasing distances from the point of inoculation at the final harvest was correlated with the proportion of roots infected at an earlier harvest, and therefore provided a useful measure of the pattern of spread of G. calospora within roots.