Expression and detection of oestrus in cattle

For herds using AI heat detection rate and calving rate are the two major determinants of compactness of calving, of the proportion of cows that fail to conceive in a defined breeding season. Numerous factors affect the expression of heat including, housing arrangement, floor surface, feet and leg problems and status of herd mates. The number of mounts a cow receives increases with the number of cows that are in heat simultaneously up to about 3-4 cows in heat. Generally, cows that are themselves in heat, coming into heat or were recently in heat are most likely to mount a cow that is in heat. Cows that are at the mid-stages of their cycles (day 5 to about day 16) are least likely to mount a cow that is in heat and consequently could be termed "poor heat detectors". Similarly, cows that are pregnant show less interest in mounting other cows that are in heat. In smaller herds and as more cows become pregnant the likelihood of more than one cow being heat on any given day becomes less, consequently, making heat detection more difficult. The single most important factor affecting heat detection efficiency is that those responsible for checking for heat should fully understand the signs of heat and be fully committed to heat detection for as long as it is planned to use Al. Technological aids to improve heat detection include the use of tail paint, oestrous synchronisation, vasectomised bulls, pressure activated heat mount detectors, radio telemetric devices, pressure sensitive mount count devices and pedometers. As herd size increases and labour become more expensive there will be a greater adoption of some of these technological aids.     

Oestrous synchronization in cattle using progesterone and a PGF analogue

A regime consisting of in jections of 150mg and 100mg of progesterone subcutaneously (s.c.) 3 days apart, followed 2 days later by a single injection intramuscularly (i.m.) of a PGF analogue (ICI 80996), and after further 12 hr interval, 1000 i.u. PMSG s.c. was used to synchronize oestrous periods in 16 cows. Eight cows (50%) conceived after insemination with frozen semen after synchronized oestrus; 14 cows came into oestrus over a 36-hr period.     

Control of oestrus in primiparous sows

The weaning to service records were analysed for 69 primiparous sows in the University College herd. More large white sows had returned to service within 7 days of weaning than crossbreds (O<0.05). However, there was no significant difference in the mean interval from weaning to heat in Large White or crossbred animals (10.5 vs 13.3 days). Sows with a weaning to service interval of less than 12 days had an average litter size of 10.3 piglets compared with 10.9 piglets when the interval was greater than 12 days. In attempts to gain control over the interval from weaning to oestrus 63 primiparous sows were allocated to either control or 20 mg allyl trenbolone per head per day for either 3 or 7 days starting on the day of weaning. Following a 7-day allyl trenbolone regime, no sow showed signs of oestrus prior to day 6 post-withdrawal, but 82% of sows were in oestrus 6–8 days post treatment, compared with 17% of controls. Results indicate that oestrus can be synchronized in about 80% of treated animals in the period of 3–8 days post-treatment. Pregnancy rates and average litter sizes were 82.9, 88.2, 88.9 and 10.5, 10.7 and 11.0 for the three treatments, respectively.     

Induction of oestrus and ovulation in anoestrous fallow deer (Dama dama) by using progesterone and GnRH treatment

Fourteen seasonally anoestrous, non-lactating fallow does were each treated with an intravaginal progesterone device for 14 days followed by a subcutaneously implanted osmotic minipump delivering synthetic GnRH at doses of 125 ng/h (7 does) or 250 ng/h (7 does) for up to 7 days, about 6 weeks before the natural breeding season. One doe (low delivery rate) lost its intravaginal device and 6 of the remaining does (46.2%) exhibited oestrus between 71 and 120 h after progesterone withdrawal/minipump insertion. Only one of these does received the low GnRH delivery rate and 5 received the high rate. Serum progesterone profiles indicated that an induced oestrus was followed by apparently normal luteal development. Does which did not exhibit oestrus failed to show a luteal response. Only 1 doe conceived at induced oestrus, producing a viable female fawn 6 weeks before the start of the natural fawning season. The remaining does returned to an anoestrous state until the onset of the natural breeding season.     

Control of parturition in the sow using progesterone and prostaglandin

The effect of progesterone and prostaglandin administration on the timing of farrowing was studied in three groups of 25 sows each. Progesterone treatment (100 mg/day) on days 112, 113 and 114 of gestation (group I) significantly prolonged the gestation length to 116.4 +/- 0.4 (mean +/- s.e.) days compared to the control sows (group III; 115.5 +/- 0.2; P less than 0.05). Administration of prostaglandin (200 micrograms Cloprostanol intramuscularly) on day 115 of gestation following progesterone treatment (group II) resulted in a gestation length of 116.0 +/- 0.1 days, with the sows farrowing 25.4 +/- 1.0 h after the prostaglandin injection. 80% of the sows farrowed between 0800 and 1700 h of day 116 of gestation. Plasma progesterone levels were maintained by the exogenous progesterone during treatment. At farrowing, higher levels of progesterone were observed in groups I and II compared to controls. Prostaglandin treatment did not significantly alter withdrawal of progesterone in progesterone treated sows, suggesting that the actions of exogenous prostaglandin is primarily on the myometrium and the cervix. Hormonal treatment in late pregnancy did not have any adverse effects on piglet viability and growth rate, or subsequent reproductive performances of sows. Lactation was initiated normally, and the concentrations of lactose, protein, fat, IgG, Na+, Ca2+ and K+ in colostrum and milk were similar in all groups during the first 5 days of lactation.     

Synchronisation of oestrus in cattle using a potent progestin (SC21009) and PGF2a

Two experiments are described in which the time relationships of oestrus and ovulation and fertility to artificial insemination in sexually mature Friesian heifers are compared with similar animals treated with PGF₂a alone or in combination with SC21009. It is concluded that neither treatment adversely affects the parameters studied but that the combined treatment will lead to an enhanced oestrous response; and offers a practical method of oestrous synchronisation at farm level.     

Some factors affecting the behavioural manifestation of oestrus in cattle: a review

The development of more efficient and cost-effective oestrous detection techniques for cattle depends on a thorough understanding of the changes in behaviour and physiology of the female during its oestrous cycle. Variability in the expression of oestrous behaviours both between individuals and over successive oestrous cycles complicates this process. This review considers many of the biological and environmental factors that influence the intensity and duration of oestrous behaviours in domestic cattle. Topics discussed include dominant-subordinate relationships, social facilitation, animal density, oestrous synchronisation, nutritional status, age and physiological state, presence of the bull and breed differences. Facility design, cattle management and various techniques used to detect oestrus (e.g. frequency, duration and timing of observations) directly influence the efficiency of oestrous detection programs. Environmental phenomena such as weather, day length, photoperiod and ambient temperature also affect the expression of oestrous behaviours.     

Induction of lactation in cattle with estradiol 17-beta and progesterone primed with progesterone

Five parous non-pregnant, non-lactating cows were injected (sc) with progesterone (50 mg/day for 7 consecutive days) followed by estradiol (0.1 mg) plus progesterone (0.25 mg) per kg body wt/day on day 12 to 14 and with reserpine / 2 mg twice a day on day 19 to 22. All the 5 cows were successfully induced into lactation. Animals exhibiting estrus following hormonal therapy were artificially inseminated and one cow became pregnant and exhibited normal parturition. Jugular blood collected was used for estimation of progesterone by RIA technique and considerable individual variation was observed in progesterone concentration.     

LC-MS/MS quantitation of plasma progesterone in cattle

Quantitation of progesterone (P₄) in biological fluids is often performed by radioimmunoassay (RIA), whereas liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) has been used much less often. Due to its autoconfirmatory nature, LC-MS/MS greatly minimizes false positives and interference. Herein we report and compare with RIA an optimized LC-MS/MS method for rapid, efficient, and cost-effective quantitation of P₄ in plasma of cattle with no sample derivatization. The quantitation of plasma P₄ released from three nonbiodegradable, commercial, intravaginal P₄-releasing devices (IPRD) over 192 h in six ovariectomized cows was compared in a pairwise study as a test case. Both techniques showed similar P₄ kinetics (P > 0.05) whereas results of P₄ quantitation by RIA were consistently higher compared with LC-MS/MS (P < 0.05) due to interference and matrix effects. The LC-MS/MS method was validated according to the recommended analytical standards and displayed P₄ limits of detection (LOD) and quantitation (LOQ) of 0.08 and a 0.25 ng/mL, respectively. The high selective LC-MS/MS method proposed herein for P₄ quantitation eliminates the risks associated with radioactive handling; it also requires no sample derivatization, which is a common requirement for LC-MS/MS quantitation of steroid hormones. Its application to multisteroid assays is also viable, and it is envisaged that it may provide a gold standard technique for hormone quantitation in animal reproductive science studies.     

Oxytocin infusion from day 10 after oestrus extends the luteal phase in non-pregnant cattle

Oestrus was synchronized in 8 cyclic heifers by progesterone treatment (PRID), after which the animals were monitored for one control cycle to measure the inter-oestrous interval. Osmotic minipumps containing saline (controls, N = 3) or oxytocin (N = 5) were implanted subcutaneously on Day 10 of the second cycle, and removed 12 days later. Jugular venous blood samples were collected daily for measurement of progesterone, and every 2 days for oxytocin. In addition, blood samples were taken every 10 min from 1 h before to 3 h after minipump insertion for measurement of plasma 15-keto-13,14-dihydroprostaglandin-F-2 alpha (PGFM) and every 30 min over the same period for measurement of progesterone and oxytocin. The lengths of the first untreated cycle in both groups of heifers were 20.2 +/- 0.56 (mean +/- s.e.m.) days compared with 25.4 +/- 0.81 days after oxytocin treatment (P less than 0.001). Oxytocin plasma concentrations in treated animals rose from less than 10 pg/ml to 70-500 pg/ml by 2 h after the start of oxytocin infusion and remained elevated until treatment was withdrawn. There was no increase in PGFM concentrations immediately after minipump insertion. Plasma progesterone concentrations were similar in treated and control animals but remained at mid-luteal levels for an average of 5 days longer in treated heifers. It is concluded that continuous administration of oxytocin can extend the luteal life-span in cattle.     

Factors affecting conception and expression of oestrus in anoestrous cows treated with progesterone and oestradiol benzoate

Nutrient balance affects the resumption of ovarian cyclic activity following calving in dairy cattle. However, few data are available about the relationships between nutrient balance and expression of oestrus or conception. It was hypothesised that previously anoestrous cows that conceived to first insemination and cows that expressed oestrus at the subsequent expected return to oestrus would be less likely to be in negative energy balance (i.e. would have higher body condition score, higher glucose, insulin-like growth factor (IGF), leptin or insulin concentrations, and lower non-esterified fatty acids (NEFA), blood urea nitrogen (BUN), beta hydroxy butyrate (BOH) concentrations 12-15 days after insemination) than herd mates not conceiving or expressing oestrus. Anoestrous cows were treated with progesterone and oestradiol benzoate (Day 0 = end of treatment period) and retrospectively categorised as conceiving (n = 108) or not conceiving (n = 108) to insemination. A subset of cows not conceiving to insemination were categorised as expressing (n = 44) or not expressing (n = 44) oestrus between Days 14 and 28 after initial insemination. Cows conceiving had a lower NEFA concentration (P = 0.014) than non-conceiving cows. Cows subsequently detected in oestrus had higher body condition scores (P = 0.016), IGF concentrations (P = 0.008) and milk protein percentages (P = 0.038), and lower BOH concentrations (P = 0.018) than cows not expressing oestrus. No difference in concentrations of leptin, insulin, glucose, blood urea nitrogen or milk yield were found between cows conceiving or not conceiving and those detected in oestrus or not detected in oestrus (P > 0.1). It is concluded that some measures of metabolic status at the time of pregnancy recognition affects the probability of pregnancy and of subsequent expression of oestrus in those treated, anoestrous cows not conceiving.     

Influence of pregnancy on the onset of oestrus and luteal function after prostaglandin-induced luteolysis in cattle

Luteolysis was induced by an injection of 500 micrograms cloprostenol (a prostaglandin (PG) analogue) in pregnant (P) Holstein heifers on Days 17 or 24 of gestation and in non-pregnant (NP) Holstein heifers on Day 17 of the oestrous cycle (oestrus = Day 0). Heifers in Groups P-17 (N = 8) and P-24 (N = 8) were inseminated twice whereas those in Group NP-17 (N = 8) were not inseminated. Immediately after PG injection, embryos were recovered by uterine flushing (400 ml) to confirm pregnancy in Groups P-17 and P-24. Uterine flushing with an equivalent volume of physiological saline was also done in Group NP-17. The interval from PG injection to oestrus and to the peak of luteinizing hormone (LH) as well as profile of increase in plasma oestradiol concentrations during that period did not differ (P greater than 0.1) among the groups. However, the proportion of heifers exhibiting abnormal luteal phases (primarily of short duration) during the oestrous cycle after PG injection was greater (P less than 0.01) in Group P-24 than in Groups NP-17 + P-17 pooled (6/8 vs 3/16). These results suggest that the previous presence of a conceptus did not have any effect on the onset of oestrus, or on plasma concentrations of oestradiol and LH after PG-induced luteolysis on Days 17 or 24 of gestation. However, luteal function during the subsequent oestrous cycle was impaired if heifers were 24 days pregnant when luteolysis was induced.     

The effectiveness of steers and heifers treated with oestrogen or testosterone to detect oestrus in cattle

Two experiments were carried out to determine the effectiveness of steers and heifers, treated with oestrogen or testosterone, in the detection of oestrus in cattle.In the first experiment 17 steers castrated at birth and 16 castrated at 6 months of age were randomly allocated to three groups and received an 800 mg subcutaneous implant of testosterone, subcutaneous injections of 10 mg oestradiol benzoate per week for 16 weeks or no hormone (controls). In addition, six heifers were injected subcutaneously with 10 mg oestradiol benzoate per week for 16 weeks while six untreated heifers served as controls. Animals were observed in a standardised libido test 2, 4, 8, 16, 20 and 24 weeks after treatment commenced. The time to first mount and the number of mounts per animal responding in the presence of oestrous heifers were recorded. Both steers and heifers treated with oestradiol benzoate were superior at detection of oestrus in cattle than animals treated with testosterone or those receiving no hormone. Oestrogen-treated animals generally detected heifers in oestrus in less than 3 min after introduction and mounted these animals between 20 and 30 times in one hour. This response was consistent throughout the duration of the experiment. There was no effect of age at castration of steers on development of male behaviour.The second experiment determined the rate and degree of development of male behaviour in steers in response to weekly subcutaneous injections of 0, 2, 4, 8 or 16 mg oestradiol benzoate per 250 kg body weight, 250 mg testosterone or 150 mg dihydrotestosterone for a period of 15 weeks. Steers treated with oestradiol benzoate again proved to be more successful than untreated or testosterone-treated steers at consistently detecting and mounting oestrous heifers. The best response was obtained from steers treated with 8 mg/250 kg body weight per week. The practical application of this work is discussed.     

Oestrogen and progesterone concentrations in plasma and oviductal tissue of ewes exhibiting a natural or induced oestrus

Synchronisation of oestrus in Karagouniki ewes by administration of the standard dose of progesterone results in lower fertility than observed when these ewes ovulate naturally. This suggests that the optimum dose of progesterone may be breed dependent. The exogenous progesterone may perturb the concentrations of oestradiol-17beta and progesterone in blood plasma and the oviductal wall. This possibility was investigated using Karagouniki ewes allocated at random to three treatments (n=4 per treatment). Ewes were allowed to exhibit natural oestrus (N) or oestrus was synchronised by administration of 250 mg (LP) or 375 mg (HP) progesterone (subcutaneous implants) followed by PMSG at 8 mg/kg live weight i.m. 14 days later. Oestrus was observed using teaser rams. Blood samples were collected for plasma oestradiol-17beta and progesterone assay from the onset to the end of oestrus at 2 h intervals. The uterus of each ewe was recovered at the end of oestrus and samples of the oviductal wall were taken from both oviducts and prepared, separately, for progesterone and oestradiol-17beta assay. Statistical analysis was performed using univariate analysis of variance. Plasma oestradiol-17beta concentrations from the onset to the end of oestrus were highest for N ewes and lowest for HP ewes with the values for LP ewes occupying an intermediate position. The differences were significant (P<0.05) between HP and the other two treatments from 4 to 12 h after the onset of oestrus and then between all treatments until the end of oestrus. Plasma progesterone levels were similar and fairly constant from the onset to the end of oestrus for N and LP. The plasma progesterone levels for HP were significantly (P<0.05) higher than for the other two treatments throughout oestrus. In oviductal wall samples, the oestradiol-17beta concentration was significantly (P<0.05) higher for N ewes than for synchronised ewes and the levels were similar for LP and HP ewes. The concentration of oestradiol-17beta differed (P<0.05) between right and left oviducts for N ewes but not for ewes of either of the synchronised oestrus treatments. Progesterone concentrations in oviductal wall samples were highest (P<0.05) for HP ewes and the values for N and LP ewes were similar. The concentration of progesterone did not differ between right and left oviductal wall samples within treatments. It was concluded that the higher dose of exogenous progesterone perturbed the levels of oestradiol-17beta and progesterone in blood plasma and the oviductal wall, and this could explain the lower levels of fertility (relative to naturally occurring oestrus) observed when this protocol is used for Karagouniki ewes in practice.     

Characteristics of oestrus measured using visual observation and radiotelemetry

The aim of this study was to measure the level of agreement between characteristics of oestrus measured using visual observation and radiotelemetry. Oestrous cycles in 20 non-lactating Holstein cows were synchronised by treatment with an intravaginal progesterone releasing inserts and injections of oestradiol benzoate for a first oestrus (Round 1) and then re-synchronised for two subsequent and successive oestrous cycles (Rounds 2 and 3). Cows were ovariectomised following the third synchronised oestrus and then retreated to induce oestrus (Round 4). Oestrus was monitored by continuous visual observation and radiotelemetry between 24 and at least 60 h after removal of inserts at Rounds 1-4. Significant differences (P<0.001) were obtained between the mean number of mounts (42.7 versus 17.8), duration of oestrus (14.4h versus 10.9h), total duration of mounts (223.9s versus 33.1s), mean duration per mount (5.6s versus 1.9s), the number of mounts per hour (3.5 versus 2.0) and the interval to oestrus (41.2h versus 42.8h) between values determined by visual observation compared with radiotelemetry, respectively. The 95% limits of agreement for all the characteristics of oestrus measured were wide although the efficiency of detection of oestrus for both methods of recording oestrus were high (97.5% (78/80) versus 93.8% (75/80), for visual observation and radiotelemetry, respectively; P=0.25). We conclude that there is poor agreement between characteristics of oestrus measured with visual observation and radiotelemetry in Holstein cows following monitoring of synchronised oestrous cycles, although both methods were equally efficient for the detection of oestrus.