Body growth and testicular characteristics of boars fed a synthetic progestogen, altrenogest

A synthetic progestogen (altrenogest) was fed to 24 Yorkshire X Duroc boars to determine effects on body growth, serum testosterone, and testicular characteristics. Boars from six litters (blocks) were allotted randomly to one of four treatment groups at 12 wk of age. Treatment groups were: controls, altrenogest fed for 3 wk, altrenogest fed for 6 wk and altrenogest fed for 9 wk. Treatment began at 15 wk of age at a daily dose of 20 mg X boar-1. Although there were no differences among treatment groups for gain and feed intake, boars fed altrenogest for 6 and 9 wk tended to consume more feed and were less (P less than .05) efficient than boars fed altrenogest for 3 wk or controls. Boars fed altrenogest for 3, 6 and 9 wk maintained lower (P less than .05) peripheral serum testosterone concentrations than controls from 15 to 24 wk of age. However, serum testosterone increased after altrenogest withdrawal in the 3- and 6-wk treatment groups but did not reach control concentrations by 24 wk. Boars fed altrenogest for 9 wk maintained serum testosterone below 1 ng/ml during the treatment period. Despite lower concentrations of serum testosterone in altrenogest-treated boars, backfat thickness was similar to controls, perhaps suggesting a slight anabolic effect of altrenogest on nutrient partitioning. Testicular weights and volumes at 24 wk decreased (P less than .001) linearly with increased duration of altrenogest feeding. Serum testosterone and estradiol in testicular venous effluent at castration were lower (P less than .01) in altrenogest-treated boars than in controls. These data demonstrate that feeding altrenogest inhibits both testicular growth and steroidogenesis of boars without altering body growth or backfat thickness.     

Growth, carcass traits, boar odor and testicular and endocrine functions of male pigs fed a progestogen, altrenogest

Crossbred (Chester White X Yorkshire X Duroc) boars were used to evaluate the effects of feeding a progestogen (altrenogest) on body growth, endocrine function (determined during feeding and after withdrawal of altrenogest), carcass composition, boar odor and testicular function (determined after a 30-d withdrawal from altrenogest). Boars from 18 litters were assigned at 12 wk of age to three treatments: 1) 18 control boars; 2) 18 boars fed altrenogest (20 mg/day) for 6 wk from 15 to 21 wk of age, followed by 30 d with no treatment; and 3) 18 boars castrated at 2 wk of age (barrows). Daily gains were greater (P less than .05) in boars fed altrenogest than in barrows through 21 wk of age but were lower (P less than .05) than those of control boars and barrows during the 30-d withdrawal period. Boars fed altrenogest weighed less (P less than .05) than control boars and barrows at 25 wk of age (at slaughter). Both groups of boars were similar in percentage of muscle and had less (P less than .05) backfat than barrows, whereas control boars had the largest (P less than .05) loineye areas. Based on evaluations by a trained sensory panel, intensity of boar odor in fat samples was similar for both groups of boars and was greater (P less than .05) than that for barrows. Weights of accessory reproductive glands and weight and sperm content of testes and epididymides were reduced (P less than .05) in boars fed altrenogest.(ABSTRACT TRUNCATED AT 250 WORDS)     

Apparent decline in fertility in heifers after repeated oestrus synchronisation with cloprostenol.

Over several years groups of heifers which were repeatedly treated with the PGF2 alpha analogue, cloprostenol, to synchronise oestrus were artificially inseminated. When sperm treatment was optimised, a reduction in conception rate was observed which was related to the number of synchronisation treatments the animals had received. Although factors such as a seasonal reduction in fertility may have contributed to the effect, there appeared to be a decrease in the proportion of animals becoming pregnant after successive synchronisations. Possible explanations for this observation are suggested.     

复合麻醉剂对小型猪血流动力学及一氧化氮和内皮素的影响

小型猪复合麻醉剂(XFM)由噻环乙胺、噻拉嗪、强痛灵等药物组成.该合剂的研制主要是为了满足医学、兽医学、生物工程及畜牧学等领域以小型猪为实验动物,开展相关科研工作及临床外科诊疗在麻醉保障方面的迫切需要[1].     

Effects of oestrus synchronisation and fixed-time artificial insemination on the reproductive performance of dairy heifers

AIM: To compare the reproductive performance of heifers after oestrus synchronisation and fixed-time artificial insemination with non-synchronised heifers bred by herd sires. METHODS: Heifers from 10 spring-calving herds were randomly divided into two groups by herd, breed and age. Heifers in one group (the synchronised group, n = 478) were synchronised with a combination of progesterone, oestradiol benzoate and PGF2alpha, and inseminated 50-54 hours after progesterone treatment. Returns to first service were resynchronised with progesterone treatment 16-21 days after the fixed-time artificial insemination. Heifers in the other group (the control group, n = 470) did not receive any treatment and were bred by herd sires. RESULTS: The conception rate of synchronised heifers to the fixed-time artificial insemination was 51.2% and to the artificial insemination after resynchronisation 40.4%. The pregnancy rate at the end of the breeding season was lower (p<0.001) for the synchronised (92.9%) than for the control (97.2%) group. The interval from start of breeding to calving was earlier for synchronised (295.9 +/- 22.5 days, mean +/- s.d.) than for control (298.5 +/- 17.3 days) heifers. CONCLUSION: Results from this study indicate that the oestrus synchronisation programme used in the present study can reduce reproductive performance by increasing the empty rate compared with natural mating.     

小型猪复合麻醉剂对小型猪血浆心钠素降钙素基因相关肽神经肽Y和神经降压素含量的影响

小型猪复合麻醉剂(XFM)由噻环乙胺、噻拉嗪、强痛灵等药物组成.该合剂的研制主要是为了满足医学、兽医学及生物工程等领域以小型猪为实验动物,开展相关科研工作及临床诊疗在麻醉保障方面的迫切需要.血浆心纳素(ANP)、降钙素基因相关肽(CGRP)、神经肽Y(NPY)和神经降压素(NT)是4种与血管舒缩功能密切相关的血管活性肽.本研究旨在通过观察注射XFM后小型猪无创血压(NIBP)、心率(HR)、ANP、CGRP、NPY和NT的变化,探讨XFM对小型猪血流动力学的影响及其作用机制.     

Synchronisation of oestrus and fertility in buffaloes using a prostaglandin analogue

Cloprostenol, a prostaglandin analogue, was administered intramuscularly to a total of 35 cycling buffalo cows and heifers in two doses, each of 0.5 mg, given 11 days apart. Out of five cows and 12 heifers subjected to observations after the second injection of cloprostenol (day 0), all except one heifer responded. Signs of oestrus were most marked on days 3 or 4. Eighteen treated heifers were kept with buffalo bulls for four days after the second injection while a control group of nine heifers was kept with bulls for 21 days. The first-service conception rate, diagnosed by rectal palpation at 60 days, was 33 1/3 per cent in both groups. Twelve treated heifers were artificially inseminated at 72 and 96 hours after the second injection of cloprostenol, using fresh semen diluted in egg yolk--citrate extender. The first service conception rate at 60 days was 30 per cent.     

Reproductive performance of lactating dairy cows following oestrus synchronisation with progesterone, oestradiol and prostaglandin

The ability to synchronise onset of oestrus, and hence the time of breeding and calving, offers potential economic and management benefits to dairy farmers, especially in herds with seasonally concentrated calving patterns. A trial involving 2681 cows in 11 seasonal herds was conducted to evaluate the reproductive performance of lactating dairy cows following oestrus synchronisation with a combination of progesterone, oestradiol and prostaglandin. Cows were randomly assigned within herds to synchronised and control groups, balanced for age, date of calving, body condition and breed. Cows in the synchronised group were treated with an intravaginal progesterone-releasing device containing 1.9 g of progesterone and a gelatin capsule containing 10 mg of oestradiol benzoate 10 days prior to the planned start of the breeding season (Day 0). The device was removed 8 days later on Day -2 and a luteolytic dose of prostaglandin F2alpha was administered 2 days prior to removal of the progesterone-releasing device. Returns to service for cows in the synchronised group were synchronised by inserting a previously used intravaginal device during Days 16-21 after the start of the breeding season. Cows in the control group were left untreated. The percentage of cows being inseminated during the first 5 days was 89.0% for the synchronised group compared to 29.7% for the control group. Compared to cows in the control group, those in the synchronised group had a lower conception rate to the first insemination (52.9% v. 64.3%, p<0.001), a lower conception rate to the second insemination (51.8% v. 62.5%, p<0.001), a higher percentage of empty cows at the end of the breeding season (7.3% v. 5.1%, p<0.05), and more insemination services per pregnancy to artificial insemination (2.0 v. 1.6, p<0.001). There was no difference between the synchronised and control groups in the percentage of cows pregnant to artificial insemination (81.8% v. 85.5%, p>0.10). The mean day of conception from the start of the breeding season was advanced (p>0.0 1) by 1.3 days in synchronised cows (19.9 +/- 0.7 days; mean +/- SEM) compared to control cows (21.2 +/- 0.5 days). It is concluded that the oestrus synchronisation regime used in the present study caused a reduction in fertility, which reduced the potential gains from using such a programme to increase reproductive efficiency in dairy cows.     

Fertility in buffaloes after oestrus synchronisation with cloprostenol and fixed time insemination.

Fifty-seven cycling buffalo cows of the river type were treated with two doses of 0.5 mg cloprostenol intramuscularly given 11 days apart. Each animal was inseminated twice at 72 and 96 hours after the second injection of cloprostenol. The first service conception rate diagnosed by rectal palpation at 90 days was 38.6 per cent. At the time of insemination the cervix was easily penetrable on both days in only 39 (68.4 per cent) of the animals. They were inseminated at or beyond the internal cervical os, while the others were inseminated in the cervical canal. There was a marked difference in conception rate between those receiving deep inseminations (48.7 per cent) and the others (16.7 per cent). In relation to the interval from calving to insemination the conception rates for those which had calved 60 to 90, 90 to 120 and 120 to 150 days earlier were 16.6, 36.4 and 55.5 per cent respectively. The use of cloprostenol treatment and fixed-time insemination is a useful method of overcoming the problem of oestrus detection in buffaloes. Acceptable levels of fertility can be obtained in those animals which have a sufficiently relaxed cervix to permit semen deposition at the internal os, provided the interval from calving to insemination is more than 90 days.     

Effects of breeding at the second oestrus or after post-weaning hormonal treatment with altrenogest on subsequent reproductive performance of primiparous sows

This study investigated the effects of breeding at the second oestrus after weaning or after feeding an orally active progestagen (altrenogest) on the subsequent reproductive performance of primiparous sows. After 3 weeks of lactation, 663 weaned sows of two genotypes were allocated into three groups: G1--breeding at the first oestrus after weaning; G2--breeding at the second oestrus after weaning and G3--treatment with altrenogest for 5 days after weaning and breeding at the first oestrus after the end of the treatment. Body weight at breeding was lower in G1 and G3 than in G2 sows (p < 0.05). The interval to show oestrus was similar for G1 and G2 groups (p > 0.05) but higher (p < 0.05) than that observed in G3 group. Within genotype A, percentages of females in oestrus within 10 days were not different (p > 0.05) among groups, whereas in genotype B, more G1 and G2 sows (p < 0.05) showed oestrus than G3 sows. In both genotypes, lower farrowing rates were observed in G3 than in G1 and G2 sows (p < 0.05) and a greater litter size (p < 0.05) was observed in G2 sows. In genotype A, the number of total born piglets was similar for G1 and G3 groups (p > 0.05), whereas in genotype B, G1 sows had a greater litter size than G3 sows (p < 0.05). Body weight at weaning and at breeding was similar (p > 0.05) between farrowed and non-farrowed sows in all groups. Reproductive performance is not improved in primiparous sows treated with altrenogest during 5 days after weaning. The reproductive performance of genotype B sows is compromised in Control and Altrenogest-treated sows but not in those bred at the second oestrus after mating. Breeding at the second oestrus after weaning allows primiparous sows to gain weight between weaning and service, and increases their farrowing rate and subsequent litter size.     

Plasma progesterone and luteinising hormone levels in cattle after synchronisation of oestrus with dinoprost

The plasma levels of progesterone and luteinising hormone (LH) were monitored in a group of cattle after pretreatment with two injections of 25 mg dinoprost. Close groupings of preovulatory LH peaks were observed and the possible significance of this is discussed. Based on the findings of this study, supporting evidence is provided for the timing of insemination after injection of cattle which have been synchronised for oestrus with dinoprost.     

Efficacy of altrenogest administration to postpone ovulation and subsequent fertility in mares

A recent report suggested administration of altrenogest during the follicular phase could postpone ovulation. Based on these results, two questions were generated. We first hypothesized that by initiating a altrenogest treatment earlier in the estrous cycle, a greater and/or more consistent delay in ovulation would result. Second, we hypothesized that exposure to elevated progestin concentrations might alter viability of the ovulatory follicle and oocyte. The focus of the first experiment was to determine if initiation of altrenogest treatment at different stages of the estrous cycle would yield a more predictable time to ovulation, whereas the second experiment was designed to determine whether mares receiving altrenogest during estrus had compromised fertility. In the first experiment thirty mares of mixed light breed, ranging in age from 5-15 years, were randomly assigned to one of three groups. The two treated groups received altrenogest (0.088 mg/kg of body weight) for two days once a follicle of 30 or 35 mm in diameter was detected. Control mares were not treated. Mares treated with altrenogest whether initiated at the detection of a 30 or 35 mm follicle demonstrated similar (P>.05) day to ovulation interval when adjusted to 35 mm (5.4 and 5.6 days, respectively). Both treated groups demonstrated a delayed interval (P<.05) when compared to control (3.9 days). Thirty-six mares of similar breed and age, were randomly assigned to two groups for use in the second experiment. All mares were monitored daily via transrectal ultrasonography from the time a 35 mm or greater follicle was detected until ovulation. Treated mares received daily doses of altrenogest (0.088 mg/kg of body weight) for two days once a follicle of 35 mm or greater was detected. Control mares received no treatment. Fertility data were collected from mares inseminated every other day with 500 million motile spermatozoa from one of two stallions with proven fertility. Pregnancy data were collected via transrectal ultrasonography at days 12, 14 and 16 post-ovulation. Ovulation data were collected from 27 control cycles and 26 treated cycles. Contrary to previous reports and Experiment 1, no difference (P=0.35) was noted between groups with respect to days to ovulation. Control mares averaged 4.14 days and treated mares averaged 4.7 days to ovulation from initial detection of a 35 mm follicle. Fertility data were also similar (P=0.8) between control and treated mares (66.6% and 61.5% per cycle, respectively). Interestingly, a greater number (P=0.017) of treated cycles (5/26) resulted in follicular regression than did control cycles (0/27). While these data suggest that this dosage of altrenogest may not postpone ovulation, it did appear related to increased incidence of follicular regression. Fertility was unaffected, however, in those mares that ovulated. Further studies are needed in which initiation at different stages of estrus and different doses of altrenogest are used.     

Multiple use of progesterone releasing intravaginal devices for synchronisation of oestrus and ovulation in cattle

Experiments were conducted to investigate the possibility of using progesterone releasing intravaginal devices (PRIDs) more than once, for the purpose of synchronising oestrus and ovulation in dairy cows. In an initial study, PRIDs were inserted into 6 ovariectomised cows for 12 days on 3 separate occasions and blood samples were collected for progresterone assay. After removal, 3 PRIDs were sterilised by autoclaving and the other 3 by gassing with ethylene oxide. After PRID insertion progesterone concentration in plasma rose rapidly. Autoclaved PRIDs which were reused once and then twice, maintained blood progesterone profiles which were comparable to the release of progesterone from a new PRID. This was not the case when PRIDs were re-used after gas sterilisation. In a second study, PRIDs were inserted into 41 dairy cows for 9 days and an injection of prostaglandin F2o was given one day before PRID removal. Onset of oestrus was determined by observation at intervals of 3 h for 30 min and time of ovulation was determined by endoscopy approximately 30 h after onset of oestrus. PRIDs were autoclaved after removal and re-used twice. In cows which received new PRIDs, 85% came into oestrus between 30 and 60 h after removal. When PRIDs were used for the second time, 100% of cows showed oestrus within 30 to 60 h. When PRIDs were used for the third time the interval between PRID removal and onset of oestrus was highly variable. Only 29% of cows showed oestrus within 30 to 60 h whereas 59% showed oestrus between 12 and 42 h after PRID removal. The distribution in estimated time between PRID removal and ovulation followed closely the distribution of onset of oestrus for each insertion of PRIDs. The synchrony of ovulation was most concentrated for the second use of PRIDs and least for the third use. A few cows did not follow the general pattern of response. Indications that the PRID may be used more than once for synchronising oestrus and ovulation in the dairy cow, and the adoption of a 9-day PRID insertion interval in any synchronisation schedule should result in a significant reduction in the cost of this technology.     

氯胺酮与咪达唑仑对巴马猪脑组织cAMP信号通路的影响

为探讨氯胺酮与咪达唑仑对巴马猪中枢神经系统cAMP信号通路的影响及影响情况,研究其中枢作用机制,试验将35头健康巴马猪随机分为对照组、麻醉诱导期、麻醉期和苏醒期四组,在每一期处死取脑组织,用ELISA法分别测定大脑皮质、小脑、丘脑、海马和脑干内cAMP含量。结果:氯胺酮和咪达唑仑分别能够一定程度的降低大脑皮质和小脑中cAMP含量。表明:氯胺酮、咪达唑仑的作用可能通过中枢神经系统cAMP信号通路产生作用,为今后进一步研究提供依据。