[A pig farm with chronic fertility problems]. / Een varkensbedrijf met jarenlange fertiliteitsproblemen.

A herd with 320 sows with chronic fertility problems is described. About 20 to 30% of the inseminated sows returned to oestrus, for unknown reasons. When the interval from insemination to return to oestrus was analysed, it appeared that 20% of the sows returned between 24 and 28 days. A thorough and extensive control of the pig-farmer's oestrus detection technique revealed that nearly all sows were inseminated between 4 to 6 days post-weaning. However, this was too early for a number of sows. These sows showed optimal oestrus symptoms 6-8 days post-weaning. This was also the explanation for the high number of sows returning to oestrus 'irregularly' between 24 and 28 days. Thus when analysing insemination intervals, the interval between 24 and 35 days should not be considered as one period but should be divided into the periods, 24-28 days and 29-35 days. In this way it is possible to distinguish between sows inseminated too early and sows returning to oestrus irregularly.

Oestrus detection techniques and insemination strategies in Bos indicus heifers synchronised with norgestomet-oestradiol.

Oestrus was synchronised in 57 Bos indicus heifers using norgestomet-oestradiol and pregnant mare serum gonadotrophin. Oestrus was detected by observations made at six-hourly intervals, using oestrogen-treated and chin-ball harnessed steers, heatmount detectors, tail-paint and visual observation. Heifers were inseminated once at either a fixed time of 49.2 +/- 0.4 h (mean +/- SE; n = 29) after implant removal or 12.6 +/- 1.5 h (n = 28) after oestrus was detected. The mean (+/- SE) time to the onset of oestrus was 47.1 +/- 1.9 h, while 90% of heifers recorded in oestrus were detected within 66 h of implant removal. Heatmount detectors were significantly more efficient at detecting oestrus than chin-ball harnessed steers, tail paint or visual observation (P < 0.001). A higher pregnancy rate was obtained in heifers inseminated after oestrus detection compared with heifers inseminated at a fixed-time (57.1 vs 34.5%; P = 0.043) and a higher pregnancy rate was obtained in heifers classified as easy to inseminate compared with heifers classified as difficult to inseminate (57.8 vs 0%, P < 0.001). We conclude that heatmount detectors are an efficient means of detecting oestrus in synchronised B indicus heifers and that pregnancy rates can be increased when insemination follows oestrus detection compared with a fixed-time insemination regimen.

Acceleration and timing of fertile ovulation in cyclic mares with a deslorelin implant.

In a blinded trial, the effectiveness and safety of 2.2 mg of the GnRH analog deslorelin acetate, administered in a short-term implant (STI) to normally cycling mares in estrus with a dominant ovarian follicle of 30 mm in diameter or larger, were evaluated, using a placebo implant as a negative control. A total of 39 mares received treatments at admittance with pre-randomized implants containing either 2.2 mg or 0 mg deslorelin. Mares were teased daily and examined rectally with ultrasound at 24 h intervals to determine time to ovulation and duration of estrus. The number of breedings and the pregnancy rate at 18 (+/- 3) and 38 (+/- 3) days were recorded, as were systemic side effects and local reactions at the implantation sites. Pregnancies resulting from breedings during the treatment estrus and/or from breedings during the next estrus were followed and the early and late pregnancy loss rate, the number of pregnancies going to term and of live-born foals was recorded. Mean follicle diameter at treatment was not significantly different between the deslorelin and placebo treatment group with 41.6 mm and 40.8 mm, respectively. Treatment with deslorelin STI reduced the time interval to ovulation significantly from 69.5 +/- 25.48 h to 42.7 +/- 12.35 h (p < 0.001). The percentage of mares having ovulated within 48 h rose from 26.3% to 95.0%, respectively, for placebo and deslorelin STI (p < 0.001). As a consequence, the duration of estrus in days and the percent of animals requiring more than 1 breeding were significantly reduced in deslorelin treated animals from 5.4 days to 4.6 days, and from 55.6% to 5.0%, respectively (p = 0.009 and = 0.001). The percent of mares pregnant from breedings at the treatment estrus (65.0% versus 44.4%) or the next estrus (83.3% versus 92.3%) was satisfactory and similar for deslorelin and placebo treated mares (p > 0.005), and in 70.0% and 66.7% of these once or twice bred mares did pregnancies go to term and live foals were born.

Towards a shorter calving interval in South African dairy herds.

The effects of a progestagen treatment regimen on the calving-to-conception period and number of inseminations per conception in a Holstein-Friesland herd [n = 60] were investigated. No significant (P > 0.05) differences were observed in days from calving to conception (80.5 vs. 82.3) and inseminations per conception (1.52 vs. 1.41) between the treatment and the control groups, although the treatment possibly contributed to an improved oestrus detection rate.

Relationship between herd calving to conception interval and culling rate for failure to conceive.

The factors affecting herd calving to conception intervals and culling rate are the interval to first service, the efficiency of heat detection, the pregnancy rate and the maximum number of oestrous cycles allowed to occur before the cow is considered to be so far into lactation that even if it does conceive, the length of the dry period and the delay to the next calving will make its production uneconomic. Depending on the fertility factor (the product of the average herd pregnancy rate and the oestrus detection rate) it is the maximum number of oestrous cycles, usually dictated by the length of the calving interval desired, that decides the outcome. A graphical representation of these mathematical relationships demonstrates methods for achieving different economic and other objectives.

Estrous behavior and detection in cattle.

Hormonal events determine the timing and maximum duration of estrous behavior, whereas environmental and social factors modulate or completely inhibit the expression of estrus. The efficiency of estrous detection can be improved on most livestock farms if more effort is given to visual observations of estrous behavior. Heat detection aids can be of value if used as a supplement to visual observations. Knowledge of factors that inhibit estrus can help producers avoid or minimize situations that make estrous detection difficult or impossible. Each livestock enterprise should have a customized heat detection program in place because blanket recommendations often fail when applied to many operations.

Piglets born after transcervical transfer of embryos into recipient gilts.

A method is described for the non-surgical transfer of embryos in pigs. Embryos at the 8-cell to the hatched blastocyst stage, recovered on days 4 to 7 of the oestrous cycle by flushing the oviducts and uteri of superovulated donors, were transferred transcervically into the uterine body of anaesthetised recipient gilts using a sterile disposable plastic spiral catheter and an embryo transfer cannula. Fifty-eight non-surgical transfers have been performed and six pregnancies were established. Eight and three normal fetuses were recovered from two recipients slaughtered between 35 and 45 days after embryo transfer. Three recipients came to term and gave birth to litters of two, six and seven living piglets. One recipient aborted between 45 and 60 days of gestation.

Ovarian activity and fertility during the first breeding season of Friesland ewe lambs.

The onset and duration of ovarian activity was assessed in 19 March-born, pure bred Friesland ewe lambs. Blood samples were collected for progesterone assay from 6 August-27 March when the lambs were 5-12 months of age. From 23 January a harnessed vasectomised ram was introduced. Colour marks on the rumps were taken as presumptive evidence of oestrus. During 1-25 March the vasectomised ram was replaced by a harnessed entire ram in order to assess fertility. The mean onset of the first normal luteal cycle, when progesterone levels exceeded 2 ng/ml-1 for two consecutive plasma samples, was on 7 October. The mean age and weight at this time were 29.9 +/- 2.73 weeks and 36.71 +/- 1.39 kg respectively. One ewe lamb became pregnant and lambed on 27 July. The mean date for cessation of ovarian activity (n = 18) was 1 March and the mean number of normal cycles monitored was 8.8 +/- 0.38. Few short luteal cycles were recorded (7/18 lambs) when only transient increases in progesterone levels were detected. The average duration of the breeding season was 142.6 +/- 4.95 days. It is concluded that pure bred Friesland ewe lambs, born during March, will reach puberty around 30 weeks of age and continue regular cyclic activity for approximately 5 months. Entire rams should be joined during January or February to ensure successful matings for lambing and milk production in late summer/early autumn.

Oestrus in the British white goat: timing of plasma luteinizing hormone surge and changes in behavioural and vaginal traits in relationship to onset of oestrus.

Length of oestrus and timing of the LH surge was measured in six British White does, housed with a vasectomized buck (experiment 1). The following breeding season, pulsatile LH release during the cycle was measured in eight does and the pattern of behavioural and vaginal traits in relation to onset of oestrus (time 0) determined (experiment 2). In experiment 1, the interval to first oestrus after introduction of the buck on 1st October was 10.3 +/- 3.0 days (n = 6) but in experiment 2, when the buck was put in on 1st September, first oestrus occurred after 39.3 +/- 3.4 days in 7/8 does and 7 days in 1/8 does indicating that adequate exposure to short days is needed before the buck can initiate ovarian activity. LH pulse frequency increased from 0-1 pulses/8 h to 3 pulses/8 h after luteolysis, with no change in pulse amplitude, suggesting that progesterone regulates LH pulse frequency. Mean LH values rose from basal to 102.1 +/- 7.8 ng/ml, 12 +/- 1.5 h after the onset of oestrus, which was 16.3 +/- 1.7 h in length. Does sought out the buck and displayed tail wagging, bleating and restlessness from -60 h to +36 h relative to the onset of oestrus (time 0). The incidence of these activities rose at -12 h and peaked at 0 h. Tail wagging, but not bleating or restlessness, also increased in intensity at 0 h, as did the intensity with which the doe actively sought out the buck. Vulval redness and swelling and onset of a clear thin vaginal discharge were first observed 1-2 days before oestrus, becoming maximal on day 0. It was concluded that onset of frequent tail wagging was the most useful trait for detecting onset of oestrus.

Evaluación de diferentes fluidos corporales de la vaca, como inducores del reflejo e Flehmen en toros Holstein / Evaluation of different cow corporal fluids as Flehmen's reflex inductors in Holstein bulls

Los objetivos del presente trabajo fueron: 1) Conocer el patrón (duración y frecuencia) del reflejo de Flehmen (RF) del toro en respuesta a mustras de moco cérvicovaginal obtenidas el día 0 del ciclo estral. 2) Conocer el patrón del RF del toro en respuesta a improntas cérvicovaginales obtenidas los días 3, 6, 9, 12, 15, 16, 17, 18, 19, 20 y 21 posestro y determinar si existen diferencias entre estos días. 3) Conocer el patrón del RF del toro en espuesta a muestras de leche obtenidas los días 0, 3, 6, 9, 12, 15, 16, 17, 18, 19, 20, 21, posestro y determinar si existían diferencias entre dichos días. En cada experimento se registró con un cronómetro la duración y frecuencia con que se daba el RF en un tiempo de exposición a la muesta de dos minutos. Se encontró una diferencia estadística significativa (P < 0.05) entre los valores promedio obtenidos respeto a la duración y frecuenia del RF durante los días del ciclo estral evaluados con muesras de moco e impronta cervicovaginal, así como con las muestras de leche. Los resultados obtenidos sugieren que la capacidad de estos fluidos para inducir el RF en el toro varía según la etapa del ciclo estral en que se encuentran las vacas y que en consecuencia las características olorosas de dichos fluidos varían según la ciclicidad ovárica. Este trabajo concuerda con estudios previos en el sentido de que el toro es capaz de predecir el inicio del estro de la vaca, incluso con varios días de anticipación, por medio del análisis olfativo de olor característico de las excreciones de la hembra.

Measurements of faecal oestradiol and progesterone in non-pregnant and pregnant domestic and exotic cats.

Faecal samples collected for variable periods from 12 animals and five species of cats were assayed for progesterone and oestradiol content by application of standard radioimmunoassays to aliquots (50 microliters) of methanol extracts (4 ml) of a mixture of 0.5 g sample, 0.5 ml water and 1 g aluminium oxide, following partitioning of the total extract with petroleum ether (3 ml), further dilution of assay aliquots and drying. Recoveries averaged 100 and 72% for oestradiol and progesterone, respectively. Results included increases in progesterone during luteal phases or pregnancies to 7688 ng g-1 (tiger, Panthera tigris), 2594 ng g-1 (lion, P. leo), 3000 ng g-1 (cheetah, Acinonyx jubatus) and 4915 ng g-1 (caracal, Felis caracal). Faecal oestradiol peaks near oestrus included 246 ng g-1 (tiger), 175 ng g-1 (lion) 190 ng g-1 (cheetah), 23 ng g-1 (caracal) and 190 ng g-1 (domestic cat, F. catus).

Comparison of induction of oestrus in dogs using metergoline, metergoline plus human chorionic gonadotrophin, or pregnant mares' serum gonadotrophin.

Twenty beagle bitches were treated with metergoline (groups I and II), ten with pregnant mares' serum gonadotrophin (PMSG; group III) and ten served as an untreated control group. Metergoline (12.5 mg per bitch) was injected intramuscularly (i.m.) every 3 days, starting between days 78 and 161 after the previous pro-oestrus. In 18 of the metergoline-treated bitches the interpro-oestrous interval (144 +/- 29 days) was significantly shorter (P < 0.01) than that of the control group (206.7 +/- 29.7 days). Of these 18 responder bitches, ten had not received human chorionic gonadotrophin (hCG) whereas eight had received 500 iu hCG i.m. in late pro-oestrus (group II). The durations of pro-oestrus and oestrus of the ten responding bitches not given hCG (6.8 +/- 5.5 and 11.7 +/- 4.5 days, respectively) did not differ (P > 0.05) from those of the control group (7.8 +/- 3.6 and 11.2 +/- 3.2 days). All ten bitches ovulated and nine became pregnant. Two of eight bitches responding to metergoline in group II exhibited a prolonged pro-oestrus after injection of hCG. In the remaining six bitches, the average duration of pro-oestrus and oestrus was 4.8 +/- 1.7 and 6.5 +/- 2.8 days, respectively, which was significantly shorter (P < 0.05) than in bitches not given hCG. The incidences of ovulation (6/8) and gestation (4/8) were lower than in bitches that received metergoline alone, or in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Mating management.

The mating management of pigs is conducted under a wide spectrum of management techniques because females are variously hand-mated, pen-mated, or artificially inseminated. Factors that may affect the onset of estrus when hand-mating are boar exposure, method of housing females after weaning, season, type of facilities, and parity. The expression of sexual behavior in both male and female pigs can be influenced by a variety of physiologic, psychological, and environmental factors. To optimize the efficiency of estrous detection, females should not receive boar stimuli just prior to estrous detection when either hand-mated or artificially inseminated. When females are pen-mated, management procedures need to be employed to prevent an excessive number of estrous females from accumulating, which leads to a decrease in boar fertility.

Use of melengestrol acetate and gonadotropins to induce fertile estrus in seasonally anestrous ewes.

Ewes of three genotypes (Hampshire, n = 59; Rambouillet, n = 36; crossbred, n = 57) were used to determine the efficiency of melengestrol acetate (MGA) and(or) PG-600 (a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin) in inducing fertile estrus in seasonally anestrus ewes. Ewes were assigned randomly, within genotype, to treatments in a 2 x 2 factorial arrangement. Treatments were control, .125 mg of MGA given twice per day for 9 d (MGA), a single 5-mL injection of PG-600 (PG-600), and the combination of treatments MGA and PG-600 (MGA/PG-600). Feeding of MGA began on May 14, 1990, and ended on May 23. Injections of PG-600 were given immediately after the last feeding of MGA or vehicle on May 23. All ewes were exposed to fertile, brisket-painted rams on May 24 (d 0) for 40 d. Ewes were checked for estrus twice daily for 9 d. Laparoscopy was performed, to assess ovulation rate (OR), on d 6 for ewes that were not detected in estrus and on d 12 for ewes that exhibited estrus. Percentage of ewes mated was increased by MGA (P less than .001). Ovulation rate of ewes exposed to rams was increased by PG-600 (P less than .01) and this effect was enhanced by MGA (P less than .05), whereas MGA alone tended to decrease OR (P less than .10). Melengestrol acetate decreased the interval to lambing by 6.5 d (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of parasite control on fertility in beef heifers.

The effect of anthelmintic treatment on the growth and conception rate in beef heifers was studied in southwestern Virginia, USA. Forty mixed-breed heifers were divided into two groups at weaning and placed on experimental pastures. Control heifers did not receive anthelmintic treatment, while animals in the treatment group were given ivermectin (200 micrograms kg-1) at the time of allocation to groups in October and again in April the following year. Supplemental feed was provided throughout the winter to ensure adequate weight gains. In May, the heifers were exposed to bulls for natural breeding for a period of 6 weeks. Weight gains, fecal egg counts, serum pepsinogen levels and pasture larvae counts were monitored throughout the experiment. No difference in conception rate was observed between the two groups, although the cumulative weight gain was significantly greater in treated than non-treated animals. Serum pepsinogen levels and fecal egg counts were also generally lower in treated than non-treated heifers.

[Menstrual cycle lengths and the estimated time of ovulation in the cynomolgus monkey (Macaca fascicularis)].

Establishing of an efficient system for the judgement of an optimal mating time is an important prerequisite for the successful development of a large scale breeding of macaques as laboratory animals. In general, an optimal mating time has been judged on the basis of individual records of menstruation. The length of the previous menstrual cycle has usually been used for the prediction of the next cycle length. In the present study, the lengths of 240 menstrual cycles of 60 cynomolgus monkeys of our breeding colony were statistically analysed. The mean and the standard deviation of those cycle-lengths were 29.4 and 4.3 days, respectively. Correlationship between the length of a menstrual cycle and the length of its previous cycle was statistically significant (p less than 0.05). However, practically the correlation was not meaningful because the correlation coefficient (r) was very small even if the length of the second one of two successive cycles (r = 0.26) or the average length of three successive cycles (r = 0.36) is selected as a reference length. In other words, a cycle length can not be predicted on the basis of the length of the previous menstrual cycle. However, a marked increase of serum follicle stimulating hormone (FSH) concentration was observed from 8 to 15 days after menstruation. In 60 per cent of the animals observed, FSH increased 10 to 11 days after menstruation. Ovulation was observed one or two days later than the day of FSH increase. Therefore, the optimal mating time is judged to be between 11 and 14 days after menstruation regardless of the menstrual cycle length.