The Australian redclaw crayfish has great potential for aquaculture intensification and global market expansion. However, traditional production methods, subfertility, and high embryo mortality could curtail industry growth. Successful embryonic and post-embryonic development also depends on the paternal genetic contribution. Direct assessment of sperm quality can potentially determine the status of male fertility in decapod crustaceans. This study evaluated redclaw crayfish sperm quality using optimized conventional and advanced functional tools. Sexually mature male redclaw (n = 33) were collected from Ross River Dam in North Queensland, Australia, and subjected to electroejaculation to yield spermatophores for sperm quality assessment. Sperm concentration and count (haemocytometer), morphology (phase contrast), viability (Hoechst 33342/PI), DNA fragmentation (TUNEL), and total potential fertile sperm concentration (TPFSC) were determined. Spermatozoa had an elliptical shape of varying sizes and a presumptive fertilization-spike structure. The mean f SEM sperm viability, DNA fragmentation, concentration, and TPFSC were 65.2 f 3.9 %, 17.2 f 2.5 %, 42.5 f 5.1 x 10(4) cells/mL, and 23.6 f 3.4 x 10(4) cells/mL, respectively. Spermatophore weight showed a positive association with sperm concentration (p = 0.001) and total potential fertile sperm concentration (TPFSC; p < 0.001), and a negative association with sperm DNA fragmentation (p = 0.022). Conversely, sperm viability showed no significant relationship with spermatophore weight (p = 0.188) but was negatively associated with body mass (p = 0.010). In conclusion, this study reported the first quantitative data on sperm morphometry and functional traits, validated species-specific diagnostic tools for sperm quality assessment, and provided insight into the relationships between sperm quality parameters and body or spermatophore weights. Our approach may inform the selection of fertile male broodstock and enhanced strategies for sperm harvesting in order to facilitate selective breeding programs for commercial redclaw aquaculture.

Redclaw crayfish Cherax quadricarinatus, a tropical freshwater species, native to Northern Australia and is regarded as a promising species for global expansion of aquaculture. However, poor female fertility is a hin-drance towards the commercial production of redclaw. The present study investigated if dissociated; pre -exposure of female redclaw to males can stimulate spawning and increase reproductive efficiency. The study was conducted in dissociated (111 days) and associated (34 days) phases. Redclaw were held in vertical recir-culating aquaculture systems with each system consisting of 42 individual compartments (45 cm length x 33 cm width x 25 cm height) arranged as six compartments horizontally and seven compartments vertically. The average body weight of females was 66 +/- 2.2 g. In the dissociated phase, females were either kept alone (0M, n = 36) or were exposed to either 1 (1M, n = 36) or 2 (2M, n = 36) males suspended in the uppermost row of the system. During the associated phase, females (n = 108) were maintained at a sex ratio of 1M:1F. During the dissociated phase, the spawning rate was less in the control compared to the male exposed groups (2.8%, 1/36, 18.1%, 13/72 respectively; p = 0.026). However, the moulting rate was greater in the control compared to the male exposed groups (22.2%, 8/36; 5.6%, 4/72 respectively; p = 0.009). During the associated phase, there were no significant differences in spawning rate (22.2%, 8/36 and 33.3%, 24/72), mean days to spawning (21.88 +/- 3.06 and 16.38 +/- 2.35), moulting rate (11.1%, 4/36 and 6.9%, 5/72) and mean days to moulting (24.50 +/- 3.97 and 22.40 +/- 3.93) in the control and male exposed groups, respectively (p > 0.05). However, the mean total number of eggs (670.9 +/- 26.0 and 507.0 +/- 29.36), fecundity (11.00 +/- 0.59 and 6.14 +/- 0.47), the hatching rate (89.70 +/- 1.31% and 77.50 +/- 9.24%) and the total number of juveniles produced (545.70 +/- 42.50 and 343.30 +/- 37.47) during the associated phase were greater in the male exposed groups compared to the control group respectively; p < 0.05). It was concluded that pre-exposure of redclaw females to males in a dissociated recir-culation system, increases spawning rate during a dissociated phase, and after exposure to males improves egg and juvenile production during an associated phase. Such a breeding strategy has potential to increase hatchery productivity.

There is a need for a safe, effective and practical method of oestrus suppression in the mare. The aim of this study was to monitor ovarian activity in mares exposed to either 9.4 or 28.2 mg deslorelin acetate, a GnRH agonist, in the form of a sustained-release implant. Following oestrus synchronisation, mares were randomly assigned to one of three groups (n = 4 per group) and administered either one (Des1 group; 9.4 mg) or three (Des3 group; 28.2 mg) implants of deslorelin acetate (Suprelorin-12, Virbac Australia) or one blank implant (Control group; Virbac Australia). Mares underwent weekly blood sampling for 12 weeks following implant placement (Day 0-Day 84), with transrectal palpation and ultrasonography of the reproductive tract at all sampling timepoints except Days 56, 70 and 77. All mares showed baseline serum progesterone concentrations (SPC; ≤1.3 nmol/L or 0.4 ng/ml) on Day 0. Cycling Control mares showed typical oestrous cyclicity characterised by peaks and troughs in SPC over time. Four of eight treated mares demonstrated a sustained elevation in SPC after the initial ovulation after implant placement; SPC declined to baseline levels (Des1 group; 2 mares) or remained elevated (Des3 group; 2 mares) at the final sampling timepoint on Day 84. Oestrous cyclicity was erratic in three of the remaining four treated mares. In total, 87.5% (7 of 8) of treated mares showed atypical oestrous cyclicity after implant placement. These results suggest that deslorelin acetate disrupts oestrous cyclicity in the mare, which warrants further research.

Use and reuse of animals for educational purposes could adversely affect animal welfare. Guidelines for quantifying, monitoring, and planning the use and reuse of animals have been developed. Within this framework, animals are assigned points for usage, with more points being allocated to procedures that may have a greater adverse effect on animal welfare. Usage of individual animals is limited to a maximum of 8 points in a calendar week, 24 points in a month, or 60 points within a 16-week study period and any associated examination period. Advantages and disadvantages of the system are discussed, while modifications are expected as knowledge emerges on the impacts of procedures on animal welfare.

Context Poor nutrition of late-pregnant cows is highly prevalent in the dry tropics and associated with high levels of calf mortality. Aims It was hypothesised that supplementation with protein to prepartum cows would restore the normal decline in progesterone prepartum and increase the transfer of passive immunity to calves, with this being further enhanced by inclusion of yeast fermentation products. Methods In total, 84 heifers and 45 cows were selected for a completely randomised block design, with the following three dietary treatments: unsupplemented, receiving ad libitum low-protein hay only; hay supplemented with 1 kg/day of protein; and supplementation with both protein and 14 g/day of a Saccharomyces cerevisiae fermentation product. Supplementation occurred for an average of 14 days before calving. Cow plasma samples in the week before parturition, and the first plasma sample after parturition, were analysed for progesterone and metabolites. Newborn calves were weighed and blood-sampled three times per week during the first 2 weeks after birth. The first two calf plasma samples were analysed for total protein, albumin, and globulin concentrations. Data were analysed using a mixed-effects model and the decline of progesterone concentration over time was modelled using a non-linear segmented model. Key results Prepartum supplementation reduced cow liveweight loss, increased glucose, reduced fat mobilisation metabolites and tended to increase average daily weight gain of calves. Including yeast fermentation products in the supplement tended to increase the transfer of passive immunity to calves. Supplementation decreased plasma progesterone before parturition and including yeast fermentation products further advanced the initiation of progesterone decline. Conclusion Protein supplementation of protein-deficient beef cows during late pregnancy helps restore the normal decrease in progesterone before parturition. Implications This study identified a plausible hormonal mechanism explaining how poor nutrition around birth can increase calf loss, opening new possibilities for short-term diet management strategies to reduce calf mortality and improve calf health.

OBJECTIVE:To investigate if modification of a gonadotrophin-releasing hormone (GnRH) based protocol to synchronise oestrus in Bos indicus cattle will improve response rates to the first administration of GnRH and improve pregnancy rates to artificial insemination (AI).DESIGN:Randomised control study.METHODS:Bos indicus heifers, nonlactating and lactating cows allocated to a GnRH-18 treatment (n = 237) were treated with an intravaginal device (IVD) and cloprostenol (0.5 mg IM) on day -11 and on day 0 remaining animals in the GnRH-7 treatment (n = 222) were administered an IVD and every animal was treated with GnRH (100 μg IM). On day 7, equine chorionic gonadotrophin (400 IU IM) and cloprostenol were administered and IVD's were removed. Animals detected in oestrus on day 9 were artificially inseminated while those not detected in oestrus were administered GnRH (100 μg IM) at 1700 hours and inseminated on day 10. Bulls were inserted 2 weeks after completion of AI and remained until day 65.RESULTS:The GnRH-18 protocol increased the diameter of the largest follicle in the ovary on day 0, increased the percentage of new CL's induced after day 0 (46.3% vs 36.1%, for GnRH-18 and GnRH-7; P = 0.022), decreased circulating concentrations of progesterone on day 7 and increased odds of pregnancy to AI in heifers but not in nonlactating and lactating cows.CONCLUSION:Treatment with the GnRH-18 compared to the GnRH-7 protocol increased pregnancy rates to AI in heifers but not in nonlactating or lactating cows.

ObjectiveThis study investigated the effects of administering saline, 100 or 250 μg of gonadotrophin releasing hormone (GnRH) on ovarian response, synchrony of oestrus and ovulation and chronic stress response in Bos indicus cattle.DesignRandomised control.MethodsAnimals were either left untreated (n = 20) or on day 0 treated with an intravaginal progesterone releasing device and either saline (n = 24), 100 μg (n = 35), or 250 (n = 35) μg of GnRH, intramuscular (IM). Blood was sampled 1.4 h after administration of treatment to monitor concentrations of luteinising hormone (LH) and P4 in serum and again 5 days later. On day 5 intravaginal P4 releasing device were removed, cloprostenol was administered IM and again 8 h later. Oestrus and ovulation were then monitored with ultrasonography for 6.5 days. Hair was clipped on day 55 for analysis of hair cortisol concentrations (HCC).ResultsNo significant differences were found between Saline and GnRH treatments in the odds of inducing a new corpus luteum (CL) and the synchrony of oestrus or ovulation. HCC did not differ significantly between treatments. Mean concentrations of LH in serum on day 0 were less in the Saline compared to 100 and 250 μg GnRH treatments but did not differ between different doses of GnRH.ConclusionMean concentrations of LH and the odds of inducing a new CL were not increased after administering 250 μg compared to 100 μg of GnRH. Animal handling events in the study did not influence HCC. Further research is needed to better optimise responses to GnRH in B. indicus cattle.

OBJECTIVE:The primary aim of this study was to investigate the contraceptive efficacy of a self-assembling uterine device (iUPOD™) in the mare. In addition, the effects of iUPODs on oestrous cyclicity, uterine health and circulating concentrations of cortisol were evaluated.METHODS:Domestic mares underwent oestrous monitoring and artificial insemination. After subsequent ovulation, mares underwent either placement (n = 7) or sham placement (n = 7; controls) of an iUPOD device. Devices were left in place for at least 3 months. Pregnancy diagnoses were carried out 14 days post-ovulation, with any pregnancies terminated at 28 days post-ovulation. All mares underwent weekly blood sampling with or without reproductive examinations throughout the study. Towards the end of the study, multiple serum samples collected over three consecutive days were analysed for concentrations of cortisol. Endometrial biopsies were collected before artificial insemination and during the subsequent breeding season. Endometrial cytology and bacterial cultures were performed before device removal (iUPOD mares) or at the end of the study (control mares).RESULTS:Pregnancies were diagnosed in 0 of 7 iUPOD mares versus 7 of 7 control mares. Placement of iUPODs was associated with extended luteal phases and variable accumulations of intra-uterine fluid. Bacterial culture results suggested that the mild endometritis associated with iUPODs was sterile in six of seven mares. Short-term placement of iUPODs had no detrimental effects on endometrial architecture. Mean serum cortisol concentrations were significantly lower in iUPOD mares than control mares.CONCLUSION:iUPODs represent a promising means of fertility control in the mare.

Concentrations of progesterone before AI have had variable effects on fertility in both Bos indicus and Bos taurus cattle. The aim of this study was to determine if fertility and concentrations of progesterone after AI were affected in Bos indicus females when pre-ovulatory follicles develop in the absence or presence of a corpus luteum (CL). Between 6.5-7.5 days after a synchronised oestrus, all follicles >= 4 mm in diameter were aspirated (Day 0) and cloprostenol was administered on Days 0 and 1 (LP4, n = 36) or on Days 4 and 5 (HP4, n = 40). Animals were inseminated on detection of oestrus until Day 9. Breeding continued using natural mating between Days 9 and 19, AI on detection of oestrus between Day 19 and 29 and natural mating between Days 29-90. Mean concentrations of progesterone were less on Days 2-4 in the LP4 compared to the HP4-treated animals but similar on Days 14 and 20. In the LP4- compared to the HP4-treated animals, the odds of being detected in oestrus and ovulating close to the first AI were similar, but odds of pregnancy to first AI (OR = 0.19, 95% CI 0.07 - 0.52) and after 1, 4 and 13 weeks of breeding were less (P <= 0.051). Absence of a CL and relatively lesser concentrations of progesterone during emergence of pre-ovulatory follicles resulted in lesser pregnancy rates to AI in Bos indicus cattle but did not affect concentrations of P4 after ovulation.

Plastic sanitary sheaths over artificial insemination (AI) guns have been used at the time of AI to improve hygiene at AI and fertility in cattle, but fertility responses have been variable in studies when AI was performed by professional inseminators. The aims of this study were to investigate whether the use of a sanitary sheath at the time of AI carried out by nonprofessional (do-it-yourself, or DIY) inseminators improves pregnancy rates to AI in pasture-based dairy cows and whether effects of sheaths are greater in cows with contaminated vulvas and in cows at increased risk of extended calving to conception intervals. Lactating dairy cows located in 10 pasture-based herds in a subtropical region of northern Australia were inseminated by herd-based DIY inseminators and assigned to be inseminated with (n = 3,655) or without (n = 3,969) a sanitary sheath, with potential effects assessed using multivariable logistic regression. Overall, use of a sheath at the time of AI did not significantly affect pregnancy rates to AI (36.3% for those inseminated without a sheath vs. 36.8% for those inseminated with a sheath; odds ratio: 1.02; 95% confidence interval: 0.92-1.11). Effects of using a sheath on pregnancy rates to AI varied by herd, with lower pregnancy rates with the use of sheaths in 1 herd and some evidence of increases in 3 herds. Unexpectedly, there was evidence that the effect of sheath on pregnancy rates was less positive (or more negative) when the vulva was classified as dirty before any cleaning of the vulva before insemination compared with when the vulva was classified as clean (interaction odds ratio: 0.75; 95% CI: 0.56-1.00). Interactions between sheath and other explanatory variables that could affect fertility were not significant; thus, there was no compelling evidence that the effect of using a sheath was modified by any of these variables. We conclude that the use of sheaths during AI of pasture-based dairy cows by DIY inseminators does not, on average, markedly improve pregnancy rates to AI. However, responses may vary between herds, and the response to sheaths may be inferior (i.e., less positive or more negative) when a cow's vulva is contaminated with feces or discharge at the time of AI compared with when the vulva is clean.

Omega-3 polyunsaturated fatty acids (n-3 PUFA) are termed essential fatty acids because they cannot be synthesized de novo by humans due to the lack of delta-12 and delta-15 desaturase enzymes and must therefore be acquired from the diet. n-3 PUFA include α-linolenic acid (ALA, 18:3n-3), eicosapentaenoic (EPA, 20:5n-3), docosahexaenoic (DHA, 22:6n-3), and the less recognized docosapentaenoic acid (DPA, 22:5n-3). The three long-chain (≥C20) n-3 PUFA (n-3 LC-PUFA), EPA, DHA, and DPA play an important role in human health by reducing the risk of chronic diseases. Up to the present time, seafood, and in particular, fish oil-derived products, have been the richest sources of n-3 LC-PUFA. The human diet generally contains insufficient amounts of these essential FA due largely to the low consumption of seafood. This issue provides opportunities to enrich the content of n-3 PUFA in other common food groups. Milk and milk products have traditionally been a major component of human diets, but are also among some of the poorest sources of n-3 PUFA. Consideration of the high consumption of milk and its processed products worldwide and the human health benefits has led to a large number of studies targeting the enhancement of n-3 PUFA content in dairy products. The main objective of this review was to evaluate the major strategies that have been employed to enhance n-3 PUFA content in dairy products and to unravel potential knowledge gaps for further research on this topic. Nutritional manipulation to date has been the main approach for altering milk fatty acids (FA) in ruminants. However, the main challenge is ruminal biohydrogenation in which dietary PUFA are hydrogenated into monounsaturated FA and/or ultimately, saturated FA, due to rumen microbial activities. The inclusion of oil seed and vegetable oil in dairy animal diets significantly elevates ALA content, while the addition of rumen-protected marine-derived supplements is the most effective way to increase the concentration of EPA, DHA, and DPA in dairy products. In our view, the mechanisms of n-3 LC-PUFA biosynthesis pathway from ALA and the biohydrogenation of individual n-3 LC-PUFA in ruminants need to be better elucidated. Identified knowledge gaps regarding the activities of candidate genes regulating the concentrations of n-3 PUFA and the responses of ruminants to specific lipid supplementation regimes are also critical to a greater understanding of nutrition-genetics interactions driving lipid metabolism.

Late pregnant cows often experience nutritional stress in northern Australia, which reduces colostrum secretion, health, and likelihood of survival of neonatal calves. The effect of prepartum supplementation on the transfer of passive immunity and growth of calves was investigated. The decline in prepartum progesterone was the hypothesised mechanism regulating the transfer of passive immunity. Ninety pregnant Droughtmaster heifers and 45 Brahman cows were used. Animals were stratified by body weight and expected calving date, and separated into two blocks of heifers and one block of cows. Animals were randomly allocated into nutritional treatments, where all were fed low quality Rhodes-grass hay: (1) Control hay only; (2) Protein (PRO), supplemented with 1 kg/d of protein supplement; and (3) Yeast fermentation products (YFP), protein supplement plus 14 g Saccharomyces cerevisiae fermentation product (NaturSafeTM). Data for final analyses was available from 92 calves on transfer of passive immunity and from 59 cow/calf pairs on prepartum progesterone decline. Treatment means were compared via orthogonal contrasts for the effect of supplementation PRO and YFP. Protein supplementation for an average of 14 d hastened the decline in the concentration of serum progesterone before parturition (p < 0.01) and tended (p = 0.09) to increase growth rate of calves during the first 10 d (1.0 vs. 0.9 kg/d). However, there was no effect of PRO on neonatal calves plasma immunoglobulin-G1 (IgG1) concentration (p = 0.43). Adding YFP further hastened the progesterone decline before parturition (p < 0.05) and tended to increase plasma IgG1 (p = 0.08). Short term nutritional supplementation prepartum may improve transfer of passive immunity and neonatal calf growth.

This study evaluated the effect of equine chorionic gonadotropin (eCG) on reproductive performance, when incorporated into the first Ovsynch + P4 synchronization following planned start mating (PSM) in pasture-based lactating dairy cows. Two synchrony programs were compared in a randomized controlled trial in Queensland, Australia. Lactating cows from a single dairy herd (n = 782) were randomly allocated to Control and eCG groups. Control cows had their estrous cycles synchronized by treatment with 100 mu g gonadotropin releasing hormone (GnRH; im) and insertion of a progesterone (P4) releasing intravaginal device that contained 1.0 g of P4 on Day 0; removal of P4 device and administration of 500 mu g of an analogue of PGF2 alpha on Day 7 (cloprostenol; im); 100 lig im of GnRH on Day 9, and fixed-time artificial insemination (FTAI) on Day 10. The eCG group were treated the same as the Control group except for the addition of 400 IU of eCG, im on Day 7 of the first synchronized estrous cycle. Following the first insemination, non-pregnant cows from both groups had their estrous cycles synchronized with the same treatment protocol without using eCG. The effects of eCG on 42d cumulative incidence of pregnancy and pregnancy per AI (P/AI) were determined using logistic regression models. The effect of eCG on time to pregnancy was determined using Kaplan-Meier survival analysis and Cox proportional hazards models. Adjusted 42 d cumulative incidence of pregnancy for eCG and control groups were 47.2 and 393% respectively (Odds ratio [OR] = 1.38, 95% CI: 1.01-1.88). Hazard of pregnancy tended to be higher in eCG cows overall (Hazard ratio [HR] = 1.18, 95% CI: 0.99-1.41) and was significantly higher when restricting to the first 42 days after PSM (HR = 131, 95% CI: 1.04-1.64). Hazards of pregnancy were not different between groups when restricting to > Day 42 post PSM (HR = 1.00, 95% CI: 0.77-1.31). P/AI tended to be higher in eCG treated cows at the first AI (44.0 vs 37.7%, OR = 130, 95% CI: 0.94-1.78). P/AI for second and third AN were not significantly different between groups. In this herd, a single treatment of eCG at the first synchronized estrus after PSM improved reproductive performance in the short term, but not at subsequent inseminations. Crown Copyright (C) 2018 Published by Elsevier Inc. All rights reserved.

In this report, an overview of the health benefits of omega-3 long-chain (≥C20) polyunsaturated fatty acids (n-3 LC-PUFA) and recent progress in using alpha linolenic acid (ALA) rich sources derived from oilseeds to enhance productive performance, n-3 PUFA profiles and sensory properties of lamb for human consumption is reviewed. Omega-3 LC-PUFA can prevent mental health issues and chronic human disorders including cancer, cardiovascular and inflammatory diseases. The median amount of n-3 LC-PUFA consumption is generally lacking in Western diets. More attention is now being paid to the use of innovative nutritional strategies to improve PUFA content in ruminants, which could subsequently increase the content of health-benefitting n-3 LC-PUFA for human consumption. The richest sources of dietary n-3 LC-PUFA are derived from marine products, while forage and oilseeds such as flaxseed, canola, and their oils are abundant in ALA. Numerous studies have shown that dietary ALA increases n-3 LC-PUFA levels of edible tissues. However, other studies concluded that ALA rich supplementation led to no differences in tissue FA profiles because of extensive biohydrogenation of dietary ALA, limited conversion from ALA to n-3 LC-PUFA and low incorporation of n-3 LC-PUFA into edible tissues. Generally, the inclusion of ALA rich sources in lamb diets potentially increases ALA content in lamb. It is proposed that supplementing ruminants with ALA-rich sources at or below 6% can promote n-3 PUFA profiles in lamb and is unlikely to have negative effects on feed intake, growth, carcass and sensory properties.

OBJECTIVE:To investigate the effect of concentration of progesterone (P4) before artificial insemination (AI) on fertility in ovulatory or anovulatory Bos indicus cattle.DESIGN:Randomised control study METHODS: The study included 162 heifers and 96 lactating cows. On days -10 to -12, animals were examined using transrectal ultrasound, administered PG and examined for a corpus luteum (CL). Those with a CL were allocated to Experiment 1. On day 0 they were administered an intravaginal progesterone-releasing device (IVD) containing progesterone (P4) (0.78 g), oestrodiol benzoate (ODB) and either saline or PG to induce high and low circulating P4 concentrations, respectively. Those without a CL were re-examined on day 0 and those without a CL at both examinations were allocated to Experiment 2. Cows and heifers were treated with an IVD containing P4 at 0.78 g or 1.56 g to induce low or high P4 concentrations, respectively. IVDs were removed on day 7 and PG and equine chorionic gonadotrophin (eCG) were administered. Females in oestrus on day 9 were inseminated; others were administered ODB and inseminated 22-26 h later.RESULTS:Greater concentrations of circulating P4 increased the odds of pregnancy to AI in anovulatory females (P = 0.008), but decreased the odds of pregnancy in one year but not another in ovulatory animals (P × year, P = 0.019).CONCLUSION:Manipulating P4 concentrations before AI has the potential to improve pregnancy outcomes to AI in B. indicus females, but treatment may need to vary between animals classified as anovulatory or ovulatory.

Synchronisation of wave emergence is used to synchronise oestrus in cattle. The aim of this study was to determine if treatment with high concentrations of progesterone in Bos indicus heifers for 3 days would synchronise new wave emergence when treatment commenced at early, mid and late stages of follicular development. Heifers were treated with a sc silicone implant containing norgestomet from Days -7 to 9 and cloprostenol (IM) on Days -7 and -2. All follicles > 4 mm in diameter were removed by transvaginal follicular aspiration either on Days 0 (Experiment 1), 3 (Experiment 2) or 6 (Experiment 3). From Days 6 to 9 every heifer was treated with two intravaginal progesterone releasing inserts that each contained either no progesterone (Control, n = 8/experiment) or 3.12 g of progesterone (n = 8/experiment). Ovarian follicular development was monitored at least once daily following aspiration until oestrus and ovulation. In each experiment, treatment with progesterone significantly increased concentrations of progesterone in plasma from Days 6 to 9 compared to Control heifers. It also significantly delayed the day of emergence of the ovulatory follicle (1.6 +/- 0.6 vs 8.6 +/- 0.3; 4.1 +/- 0.1 vs 8.6 +/- 0.2; 7.0 +/- 0.0 vs 9.3 +/- 0.4, for Control vs progesterone treated heifers, respectively in Experiments 1 to 3) and the interval from implant removal to oestrus and ovulation. In conclusion, treatment with high concentrations of progesterone can synchronise wave emergence in Bos indicus heifers when administered at early, mid and late stages of follicular development.

OBJECTIVE:To investigate if administration of potential chemosterilants by transvaginal, ultrasound-guided intraovarian injection is an alternative to surgical sterilisation.DESIGN:Randomised control study.METHODS:Bos indicus heifers were treated with intraovarian injections of saline (n = 10), CaCl2 (n = 10), zinc gluconate (ZG; n = 10) or a combination of CaCl2 and ZG (CaCl2 + ZG; n = 10). Heifers were exposed to a bull from 82 to 84 days after treatment and slaughtered between 364 and 396 days after treatment.RESULTS:After treatment administration, the concentrations of haptoglobin and anti-Müllerian hormone and the total oocyte counts did not differ (P > 0.150) between treatments. Pain responses were observed in heifers treated with ZG and CaCl2 + ZG but not in heifers treated with saline or CaCl2 . Total ovarian mass at slaughter was less in heifers treated with CaCl2 compared with the other treatments (P < 0.05). Complete regression of one ovary was observed in 40% (4/10) of the heifers treated with CaCl2 . Pregnancies were recorded in ≥ 70% of heifers administered each treatment.CONCLUSION:Treatments used in this study were not able to sterilise most of the B. indicus heifers, but treatment with CaCl2 has the potential to cause complete ovarian atrophy without causing detectable pain.