Induction of sexual activity in lactating anovulatory female goats using male goats treated only with artificially long days

Two experiments were conducted to determine the response of Creole male goats treated with long days and melatonin implants, and the response of the anovulatory does to male effect using males treated only with artificially long days. All animals were allocated to open sheds. In Exp. 1, one group of males was under natural photoperiod (CG; n = 7); the second group was submitted to 2.5 mo of long days followed by the insertion of two s.c. melatonin implants (LD+MEL; n = 7); the third group was subjected only to 2.5 mo of long days (LD; n = 7). Testicular weight was measured every 2 wk. Plasma testosterone concentrations were determined weekly. A treatment x time interaction was detected (P < 0.001) for testicular weight and plasma testosterone concentration. In the LD+MEL and LD groups, testicular size and plasma testosterone levels varied in a similar way, but differed from those observed in CG (P < 0.001). In this latter group, testicular weight displayed seasonal variations and peaked in June, whereas in treated groups this peak occurred in March. In CG, testosterone varied in a seasonal manner and plasma concentrations increased in June and remained elevated throughout the study. In experimental groups, testosterone increased in February and peaked in March. In Exp. 2, one group of males was left under natural photoperiod (CG, n = 5) and the other one was submitted to 2.5 mo of artificially long days (LD, n = 4). On March 16, two control and two treated males were put in contact with 20 and 19 females, respectively. Sexual behavior of the bucks was observed during the 5 d following male introduction. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. The anogenital sniffing, nudging, and mount instances registered in LD-treated males were greater than those observed in CG (P < 0.05). Of the does exposed to CG, none ovulated and only two of 20 females displayed estrous behavior. All does in contact with LD-treated males ovulated and showed at least one estrous behavior during the 15 d following joining (P < 0.001). These results indicate that the sexual activity of male goats from subtropical latitudes can be induced using only artificially long days. In addition, males treated in this way are capable of stimulating sexual activity in anovulatory females by the male effect.     

Effect of prolonged exposure to exogenous melatonin on the onset and end of the breeding season and on the growth rate of ewe lambs

The effect of prolonged exposure to exogenous melatonin on the reproductive status and growth rate of ewe lambs was investigated. Ewe lambs (born late March) were given intravaginal melatonin implants on 4 July (group J, n = 10) during anoestrus, or 20 December (group D, n = 10) during the breeding season. A third group (group C, n = 7) received empty implants on 4 July. Plasma progesterone concentrations were used to assess reproductive status. In the control group cyclic ovarian activity began on November 15 +/- 4 days, and ceased on January 28 +/- 8 days. In group J the onset of the breeding season was advanced by 4.9 weeks (occurring on October 12 +/- 4 days; P less than 0.001). The onset of anoestrus was also advanced in this group with 9 out of 10 of the ewes ceasing ovarian activity at least 3.4 weeks in advance of the control ewes (P less than 0.01). In contrast the timing of anoestrus was unchanged in group D, occurring on February 14 +/- 6 days. Melatonin treatment of ewe lambs from early July had no effect on growth rate, whereas treatment from mid-December had a depressive effect. Ewes therefore become refractory to the inductive effects of exogenous melatonin after long-term exposure. The results are consistent with the view that photorefractoriness is due to changes in the processing rather than the generation of the melatonin signal.     

褪黑激素对内蒙古白绒山羊产绒性能的影响

试验选用24只,平均年龄(15±1.5)月龄、平均活重(32.92±2.33)kg半同胞羯羊,随机分为4组,分别埋植0、2、4、8 mg/kg BW褪黑激素(MT),研究MT对内蒙古白绒山羊生绒期产绒性能的影响。结果表明:绒萌发前约一个月(夏至)埋植MT显著提高了血浆MT浓度,使羊绒萌发时间提前,绒长度增加、产绒量提高,而对绒纤维细度和粗毛生长没有影响,同时确定MT适宜剂量为2mg/kg BW。     

Annual changes in testicular size and serum and fecal testosterone concentrations in male bharals, Pseudois nayaur

The serum and fecal testosterone (T) concentrations and testicular sizes of two male bharals (Pseudois nayaur) were determined for approximately one year. The profiles of the fecal T concentrations showed a similar tendency as the profiles of serum T concentrations, and there was a significant correlation between serum and fecal T concentrations (r=0.72). T concentrations rose drastically in October and decreased gradually until January. The maximum testicular size was observed between November and January. Semen collected between December and January was excellent in quality and comparable to domestic sheep and goats. The active periods of the testes were synchronized with the early breeding season of females.     

Effects of melatonin implantation on cashmere yield,fibre characteristics,duration of cashmere growth as well as growth and reproductive performance of Inner Mongolian cashmere goats

Background

Exogenous melatonin could induce cashmere growth. However, induced growth of cashmere fleece by melatonin implants cannot be combined with the typical growth, resulting in earlier shedding followed by another cycle of cashmere growth. To address this issue, we examine the effects on the cashmere yield, fibre characteristics, and the growth and reproductive performance of cashmere goats of planned administration of melatonin.

Methods

Eighteen half-sib, female goats were assigned to two treatments (n = 9) including a control and a treatment where melatonin (2 mg/kg BW) was implanted at the end of April and end of June. Cashmere growth and shedding were observed for approximately 1 year following implantation. Fibre samples were collected monthly to determine cumulative cashmere length. Initiation and cessation dates for cashmere growth as well as the rate of cashmere growth were calculated. Cashmere yield, weight gain of dam, kidding date, litter size, and birth weight were also recorded.

Results

Melatonin implantation increased cashmere yield by 34.5 % (control 553.7 g vs. melatonin 745.0 g; P < 0.01), cashmere length by 21.3 % (control 95.2 mm vs. melatonin 115.4 mm; P < 0.01), and decreased fibre diameter by 4.4 % (control 14.6 μm vs. melatonin 14.0 μm; P < 0.03). In melatonin-treated goats, the average initiation date was earlier than in control goats (May 18, 2013 vs. July 2, 2013; P < 0.01) but there was a similar cessation date (March 22, 2014 vs. March 27, 2014). Consequently, the duration of cashmere growth was longer in melatonin-treated goats than in control goats (307 vs.270 days; P < 0.01). The final BW, average daily gain, kidding date, litter size, and birth weight were not influenced by melatonin implantation.

Conclusions

These data indicate that melatonin implantation (2 mg/kg BW) on two occasions (late April and June) increased cashmere yield by combining the induced growth of cashmere fleece with the typical growth and decreased the fibre diameter without changing dam growth rate or reproductive performance.     

Synchronization of estrus in dairy goats given norgestomet and estradiol valerate at various stages of the estrous cycle.

Dairy goats were given subcutaneous implants with 3 mg of norgestomet (NOR) and IM injections of 0.625 mg of estradiol valerate and 0.375 mg of norgestomet on day 0 of the estrous cycle (estrus; NOR 0, n = 18), on postestrus day 4 (NOR 4, n = 18), or on postestrus day 11 (NOR 11, n = 15). Ear implants were removed after 9 days. Mean (+/- SE) hours from removal of ear implants to onset of estrus and proportion of goats responding were 36 +/- 3.8 and 83%, 33 +/- 4.0 and 61%, and 36 +/- 2.7 and 93% for groups NOR 0, NOR 4, and NOR 11, respectively. There were no significant differences between treatment groups in time to onset of estrus. The percentage of goats in group NOR 11 that had signs of estrus was significantly greater than the percentage of goats in group NOR 4. Of the goats in groups NOR 0, NOR 4, and NOR 11 that had signs of estrus, 53, 55, and 86%, respectively, had onset of behavioral estrus between 24 and 48 hours after implant removal. All goats that had signs of estrus had onset of behavioral estrus between 12 and 72 hours after implant removal. Mean (+/- SE) hours from removal of ear implants to time of peak concentrations of luteinizing hormone (LH) were 49 +/- 4.1, 49 +/- 3.8, and 49 +/- 4.0 for groups NOR 0, NOR 4, NOR 11, respectively (not different). The percentage of goats in group NOR 11 that had LH peaks was significantly greater than the percentage of goats in group NOR 4.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of urea-molasses block supplementation on grazing weaner goats naturally infected with gastrointestinal nematodes

The influence of feeding urea-molasses blocks (UMB) on growth and gastrointestinal (GI) nematode parasitism of weaner goats grazing the same pasture was investigated on a farm in Nyandarua District, Kenya. Thirty female Small East African goat kids at an average age of 5 months were initially treated with albendazole orally (5 mg kg(-1) body mass) and randomly assigned into one of two groups: group I were fed UMB prepared using a cold process and group II kids (controls) received no block supplementation (NBS). The UMB were given in the evening when the animals returned from grazing and were consumed during the night at a rate of 95.0 g head(-1) day(-1). Supplementation was undertaken for 3 consecutive months from July to September 2001 and January to March 2002. Body mass of the kids and faecal egg counts were measured monthly and larval cultures were performed on positive faecal samples of kids of each group. Five goats from each group were randomly selected for slaughter and total counts and identification of worms at the end of June 2002. Significant differences (P < 0.05) were found in cumulative mass gains of kids in group I from September compared with those in group II. On termination of the study kids in group I had gained an average of (+/- SD) 20.4 +/- 1.4 kg while those in group II had gained 11.8 +/- 1.1 kg. From January 2002, faecal egg counts of the kids in the UMB group differed significantly (P < 0.05) from those of the NBS group and at slaughter, the mean (+/- SD) worm counts for the UMB group was 482 +/- 299 while that of the NBS group was 1 302 +/- 410. In all the goats, Haemonchus contortus was the predominant nematode recovered. These results indicate that UMB had significant effects in the control of GI nematode parasitism and enhanced growth of the young goats.     

Enhancement of the male effect on reproductive performance in female Mediterranean goats with long day and/or melatonin treatment

The aim of this study was to determine whether the male effect on reproductive performance in female Mediterranean goats could be enhanced if used in combination with long day and/or melatonin treatments. Thirty-two does were exposed to long days (16 h of light/day) for 95 days. At the end of this period, 16 received one melatonin implant (group LD-M) and 16 did not (group LD). Simultaneously, 16 does under natural photoperiod were implanted with melatonin (group M) or given no treatment (group C, n=16). On April 14th, after 49 days of isolation from males, all does were exposed to bucks fitted with marking harnesses. Oestrous activity, as detected by visual observation, was recorded daily. Transrectal ultrasonography was used to record ovulation, and ovarian activity confirmed by determining plasma progesterone concentration. Oestrous activity, ovulation and fertility were greater in all treatment groups compared with group C (P<0.05), but no differences in ovulation rate or litter size were observed (P>0.05). Productivity (mean number of kids per female) of the LD-M and M groups was significantly greater than in group C (1.50 ± 0.01 and 1.37 ± 0.01 vs. 0.69 ± 0.01 kids, respectively) (P<0.05). Combining melatonin treatment with natural or artificial long days adds to the impact of the male effect.     

Melatonin improves testicular haemodynamics,echotexture and testosterone production in Ossimi rams during the breeding season

The objective was to determine effects of a single parenteral dose of melatonin on testicular blood flow indices, testicular echogenicity and plasma testosterone concentrations in rams during the physiological breeding season. We hypothesized that melatonin enhances testicular blood flow, echogenicity and plasma testosterone concentrations during the breeding season in rams. During the breeding season, 12 sexually mature Ossimi rams were randomly allocated to either a melatonin group (n = 8) that received 18 mg of melatonin in 1 ml of corn oil (injected SC) or a control group (n = 4) that received 1 ml corn oil only. Blood collection and ultrasonographic assessment of the testes and supratesticular arteries were conducted immediately before treatment (W0) and once weekly for 6 weeks after melatonin injection (W1-W6). Mean plasma testosterone concentrations were greater (p < .05; at least 1 ng/ml) in the melatonin-treated group compared to the control group from W4 to W6 after treatment. A decrease (p < .05) in both resistive index (RI) and pulsatility index (PI) began 1 week after melatonin injection (W1) and persisted until the end of the experiment, with mean RI and PI values in the melatonin group lower (p < .05) than those in the control group on W3 and W4. Furthermore, plasma testosterone concentrations in melatonin-treated rams were inversely correlated to both RI and PI (r = −.7 and −.6, respectively, p < .01). Testicular echogenicity decreased (p < .05) 1 week after melatonin injection (W1) and remained lower (p < .05) in the melatonin-treated group compared to the control group until the end of the study (W6). In conclusion, melatonin administration significantly altered testicular blood flow and echogenicity and increased plasma testosterone concentrations in Ossimi rams during the breeding season.     

Out-of-season breeding of milk goats--the effect of light treatment,melatonin and breed

The purpose of this study was to evaluate the effectivity of melatonin in addition to light treatment (exposure to 2 hours of light during the night = a long-day photoperiod) to modify the breeding season of Saanen and cross-bred milk goats and to compare the difference between the breeds. Twenty-two Saanen and 22 cross-bred does were randomly divided into 3 treatment groups. Group 1 (controls) received no treatment, Group 2 received light treatment for 37 days and Group 3 received light treatment plus melatonin implants after the light treatment. After a further 35 days the 3 groups were brought together and a billy goat that had also been exposed to the extra light at night, had received a melatonin implant and had been isolated from the does during the treatment period, was introduced to the does for natural mating. Ultrasound scanning was used to diagnose pregnancy and all the pregnant goats kidded. Significantly more Saanen does compared to cross-bred does (P = 0.018) became pregnant and kidded after natural mating, when the group that received melatonin as well as light treatment was compared to the group that received light treatment only. Compared to light treatment only, the addition of melatonin to light treatment improved (P = 0.0028) conception after natural mating, in both the Saanen and the cross-bred does.     

Effects of dietary phytoestrogens on plasma testosterone and triiodothyronine (T3) levels in male goat kids

Background

Exposure to xenoestrogens in humans and animals has gained increasing attention due to the effects of these compounds on reproduction. The present study was undertaken to investigate the influence of low-dose dietary phytoestrogen exposure, i.e. a mixture of genistein, daidzein, biochanin A and formononetin, on the establishment of testosterone production during puberty in male goat kids.

Methods

Goat kids at the age of 3 months received either a standard diet or a diet supplemented with phytoestrogens (3 - 4 mg/kg/day) for ~3 months. Plasma testosterone and total and free triiodothyronine (T₃) concentrations were determined weekly. Testicular levels of testosterone and cAMP were measured at the end of the experiment. Repeated measurement analysis of variance using the MIXED procedure on the generated averages, according to the Statistical Analysis System program package (Release 6.12, 1996, SAS Institute Inc., Cary, NC, USA) was carried out.

Results

No significant difference in plasma testosterone concentration between the groups was detected during the first 7 weeks. However, at the age of 5 months (i.e. October 1, week 8) phytoestrogen-treated animals showed significantly higher testosterone concentrations than control animals (37.5 nmol/l vs 19.1 nmol/l). This elevation was preceded by a rise in plasma total T₃ that occurred on September 17 (week 6). A slightly higher concentration of free T₃ was detected in the phytoestrogen group at the same time point, but it was not until October 8 and 15 (week 9 and 10) that a significant difference was found between the groups. At the termination of the experiment, testicular cAMP levels were significantly lower in goats fed a phytoestrogen-supplemented diet. Phytoestrogen-fed animals also had lower plasma and testicular testosterone concentrations, but these differences were not statistically significant.

Conclusion

Our findings suggest that phytoestrogens can stimulate testosterone synthesis during puberty in male goats by increasing the secretion of T₃; a hormone known to stimulate Leydig cell steroidogenesis. It is possible that feedback signalling underlies the tendency towards decreased steroid production at the end of the experiment.     

埋植外源褪黑激素对不同年龄内蒙古绒山羊产绒性能的影响

为研究非长绒期埋植外源褪黑激素对不同年龄内蒙古绒山羊产绒性能的影响,本试验选择2～6岁能繁母羊150只,每个年龄段根据产绒量和体重将母羊随机分为对照组和试验组,试验组于2014年4月30日和6月30日埋植2 mg/kg BW褪黑激素于耳部皮下。自埋植开始至试验结束(2015年4月底抓绒),逐月观察山羊绒生长情况,并于抓绒时采集绒样,分析埋植对山羊绒生长的影响。结果表明:与对照组相比,试验组所有年龄段山羊绒产量和绒长度均显著提高,绒细度显著降低(P<0.05),其中5岁埋植组山羊的产绒量提高幅度和细度下降幅度最大,分别达到28.75%、4.94%,6岁埋植组山羊绒长度增加幅度最大,为29.27%。综上,不同年龄内蒙古绒山羊埋植外源褪黑激素均有促进山羊绒生长和提高产量作用,但不同年龄绒山羊增产效果不一致,并且褪黑激素对于提高内蒙古绒山羊后期的生产力作用更大。     

Effects of photoperiod on the secretion of growth hormone in female goats

The aim of the present study was to clarify the effect of photoperiod on the secretion of growth hormone (GH) in goats. Adult female goats were kept at 20°C with an 8‐h or 16‐h photoperiod, and secretory patterns of GH for 4 h (12.00 to 16.00 hours) were compared. In addition, the goats were kept under a 16‐h photoperiod and orally administered saline (controls) or melatonin, and the effects of melatonin on the secretion of GH were examined. GH was secreted in a pulsatile manner. There were no significant differences in pulse frequency between the 8‐ and 16‐h photoperiods; however, GH pulse amplitude tended to be greater in the group with the 16‐h photoperiod (P = 0.1), and mean GH concentrations were significantly greater in the 16‐h photoperiod (P < 0.05). The GH‐releasing response to GH‐releasing hormone (GHRH) was also significantly greater for the 16‐h photoperiod (P < 0.05). There were no significant differences in GH pulse frequency between the saline‐ and melatonin‐treated groups. However, GH pulse amplitude and mean GH concentrations were significantly greater in the saline‐treated group (P < 0.05). The present results show that a long photoperiod enhances the secretion of GH, and melatonin modifies GH secretion in female goats.     

Seasonal changes of testicular weight, sperm production, serum testosterone, and in vitro testosterone release in Korean ring-necked pheasants (Phasianus colchicus karpowi)

To study the biology of reproduction of male Korean ring-necked pheasants kept under natural conditions of temperature and photoperiod, testicular weight, serum testosterone concentrations, testosterone release from the luteinizing hormone (LH)-stimulated testis in vitro and sperm production were measured. Significant changes associated with seasonal cycles were found. Testis weight decreased dramatically in August, remained low until February, rapidly increased from March to high levels to June, and decreased subsequently. Serum testosterone concentrations remained little from August until February, but increased sharply in March to reach the highest levels in April. Thereafter, the concentrations decreased significantly from June. The testosterone release was low from August to February, increased abruptly in March to reach the highest levels in May, and showed rapid decrease thereafter. Sperm production decreased to nondetectable levels from August to February, increased markedly in March, reached a peak in May, and sharply decreased thereafter. Thus, the pheasants breed from late March to late June. These results indicate that the Korean ring-necked pheasant, under natural conditions, exhibits characteristics of a seasonal cycle in reproduction.     

Reproductive performance is improved during seasonal anoestrus when female and male Murciano-Granadina goats receive melatonin implants and in Payoya goats when females are thus treated

This work investigates whether the reproductive performance of Mediterranean goats achieved using melatonin implants at around the spring equinox is affected by the protocol followed, i.e. implanting females only, males only, both sexes or neither sex. In a first experiment, Murciano-Granadina females (n = 419, 510 and 631 for three consecutive years) were divided into four groups: treated with melatonin (FM) and not treated with melatonin (FC), mounted by males treated with melatonin (MM) or not (MC). In a second experiment, performed during 2009, the same protocols were used with 635 Payoya females and the results compared with those obtained for the same year for the Murciano-Granadina breed. Fertility (percentage of goats kidding), litter size (number of kids born per female kidded) and productivity (number of kids per female in each mating group) were calculated. In the first experiment, better reproductive performances were obtained when females (overall fertility: 71.1% vs 57.0% for the FM and FC animals; productivity 1.37 ± 0.04 kids per female vs 1.12 ± 0.03 kids per female for the FM and FC animals; p < 0.01) or males (overall fertility: 65.9% vs 58.4 for the MM and MC animals; productivity 1.28 ± 0.03 kids per female vs 1.13 ± 0.04 kids per female for MM and MC groups, respectively; p < 0.01) were implanted with melatonin. Moreover, the interaction sex × melatonin treatment had a significant effect (p < 0.05) on productivity. In the second experiment, for the Murciano-Granadina breed, the greatest increase in the number of kids born per female was obtained when the females were treated with melatonin, in either the FM/MC or FM/MM protocols (0.54 extra kids and 0.53 extra kids per female, respectively) (p < 0.01). In the Payoya breed, the greatest increase was obtained using the FM/MC protocol (0.19 extra kids per female). Thus, improved reproductive performances are obtained when female Murciano-Granadina and Payoya goats are implanted with melatonin, although important differences in reproductive performance are seen between the breeds.     

光照和埋植褪黑激素对非生绒期内蒙古白绒山羊体成分的影响及应用

本文从体成分的角度研究了褪黑激素对内蒙古白绒山羊营养分配的影响,研究结果显示光照时间和埋植褪黑激素显著影响绒山羊的有关激素水平,进而影响体成分组成。随着光照时间的缩短,绒山羊的体脂肪含量增加,体蛋白含量减少;光照相同条件下,埋植褪黑激素组的体脂肪含量高于不埋植组,体蛋白含量低于不埋植组,短光照和埋植褪黑激素之间有显著(P<0.01)的互作效应。证明了光照和褪黑激素在动物营养分配中的作用,为褪黑激素在生产实践中的合理应用提供理论依据。     

Reproductive seasonality in female goats adapted to a subtropical environment persists independently of food availability

The aim of this study was to determine whether the seasonal change in food availability provides a predictive cue that synchronizes the breeding season in goats adapted to the subtropical conditions of Northern Mexico. Groups of multiparous intact (n = 7) and ovariectomized does bearing a subcutaneous implant constantly releasing estradiol-l7β (OVX+E; n = 12) were allocated in two pens and received a constant amount of feed. Another group of OVX+E does (n = 10) was incorporated into a flock raised under natural grazing conditions with seasonal fluctuations in food availability. Blood samples were taken twice weekly. Ovulation of intact goats was inferred from plasma progesterone levels. In OVX+E does plasma levels of LH were measured. Intact does displayed seasonal variations in ovulation and the breeding season lasted from September to February. OVX+E goats displayed large seasonal variations in LH secretion regardless of whether they were fed constantly indoors or kept under natural grazing conditions (P < 0.0001). The mean date of increase in LH secretion varied between years (P < 0.0001) but did not differ between groups (naturally grazed: August 13 ± 10 days; constantly fed: August 26 ± 10 days). In contrast, the seasonal decline in LH secretion differed between groups: it was consistently delayed in constantly fed animals compared to those feeding naturally (naturally grazed: January 28 ± 4 days; constantly fed: February 24 ± 6 days, group effect, P < 0.01). These results show that local female goats from subtropical Mexico display large reproductive seasonality independently of food availability.     

Subtropical goats ovulate in response to the male effect after a prolonged treatment of artificial long days to stimulate their milk yield

The objectives of this study were to determine (i) if in subtropical goats that gave birth during mid‐December, the exposition to an artificial long‐day photoperiod consisting in only 14 hr of light per day can increase the milk yield and (ii) to test whether these females can respond to the male effect at the end of the prolonged photoperiodic treatment. In experiment 1, 17 lactating goats were maintained under natural short days (control group), while another 22 goats were maintained under artificial long days (treated group) consisting in 14 hr light and 10 hr darkness starting at day 10 of lactation. The continuous exposition to an artificial long‐day photoperiod produced an increase in the milk yield level during the first 110 days of lactation (time × treatment interaction; p = .01), while none of the milk components were modified due to the photoperiodic treatment (p > .05). In experiment 2, all control and treated anovulatory goats were submitted to the male effect using photostimulated males. All females showed oestrous behaviour within the first 10 days that were in contact with males (100% in both groups; p > .05). Thus, the latency to onset of oestrus did not differ between females from control (58.2 ± 3.0 hr) and treated (62 ± 4.6 hr) groups. Male exposition provoked ovulation independently if females were previously under long days or natural photoperiod (96 vs 100%, respectively; p = .79). It was concluded that exposure to 14 hr of light per day in subtropical goats that gave birth in late autumn stimulates milk yield without preventing the ovulation in response to the male effect at the end of the prolonged photoperiodic treatment.     

The effect of testosterone and rutting on the metabolism and pharmacokinetics of sulphadimidine in goats

After testosterone pretreatment of castrated goats and during the rutting season of adult entire male goats, the oxidative metabolism of sulphadimidine (SDM) was inhibited markedly compared with the castrated control state of these animals. The oxidation of the 5 position (yielding 5-hydroxysulphadimidine) and of the 6-hydroxymethyl group (yielding 6-carboxysulphadimidine) was decreased equally, with that of the methyl group at the pyrimidine side chain itself being 6-hydroxymethylsulphadimidine (CH2OH), whereas the acetylation pathway was unaffected by testosterone. The consequence of altered metabolism by testosterone was a prolongation of SDM presence in the body. Effects on protein binding of the CH2OH metabolite and on the renal clearance of SDM were also investigated.     

Effects of melatonin treatment on the attainment of puberty in heifers.

This experiment determined the effect of treatment of 3- to 4-mo-old heifer calves with exogenous melatonin, in early summer, on the attainment of puberty the following spring. Hereford heifers, born between February 22, and March 16, were paired by age and BW and assigned at random within pair to receive an ear implant of melatonin (MEL, n = 12) or to serve as controls (C, n = 12). The implant period was 5 wk, starting June 10 at a mean age of 105 +/- 5 d and 134.4 +/- 3.5 kg BW. Puberty was evaluated the following year on four occasions: January 26, March 19, May 2, and June 1. One each date, rectal palpation of the ovaries was performed, blood samples were taken to assess concentrations of progesterone (P4), and BW was determined. Puberty was considered to have occurred when concentrations of P4 were greater than or equal to .5 ng/mL concomitant with a palpable corpus luteum (CL), or when concentrations of P4 were greater than or equal to 1 ng/mL and a CL was present on the next date. At implant removal, concentrations of melatonin in plasma collected at 1000 to 1400 were 69.5 +/- 6.3 and 16.7 +/- 2.4 pg/mL for MEL and C heifers, respectively. On that and subsequent occasions, neither BW nor ADG differed between MEL and C heifers. Treatment with melatonin increased the incidence of heifers pubertal by the second observation date (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)