圈养条件下狍发情配种模式的研究

通过在吉林农业科技学院左家校区动物实习基地进行试验,研究了野生狍(中国亚种)在人工驯化饲养条件下的发情配种模式.研究结果表明:狍属于短日照繁殖动物,发情和配种在秋季进行,每年有一个发情周期,性成熟是14±2月龄;雄狍在整个发情配种期始终保持兴奋状态,随时可以与达到发情旺期的雌狍进行交配,发情的雌狍外观没有明显表现,当对雄狍表现好感、主动亲近雄狍时,就是交配的最好时机;狍配种方式采用单雄群雌的同期复配方式,性别比例为雄性狍∶雌性狍=1∶4.     

室内条件下云斑天牛成虫相遇行为反应

为了探索云斑天牛Batocera lineolata Chevrolat雌雄成虫的交配机制, 采用室内饲养观察和视频轨迹捕捉系统(EthoVision 3.1)自动记录分析相结合的方法, 对云斑天牛的两性相遇行为进行了研究。行为仪分析结果表明, 雌雌、 雄雄与雌雄相遇过程中, 雌雄在轨迹相交时间和净相对运动上显著长于雌雌和雄雄(P<0.05), 而在反应前时间上显著短于雌雌和雄雄相遇情况(P<0.05)。室内试验观察表明, 云斑天牛成虫相遇包括避让、 打斗和交配3种行为。雌雌相遇发生避让的频率最高为80.98%(P<0.05)。雄雄相遇发生避让的频率为78.03%, 显著高于发生打斗的频率21.96%(P<0.05); 雌、 雄成虫与正在交配的一对成虫相遇发生避让的频率显著高于另外3种行为［打斗(继续交配)、 打斗(结束交配)、 打斗(与后来者交配)］(P<0.05), 雌、 雄成虫发生避让、 打斗(继续交配)和打斗(结束交配)3种行为的发生频率存在性别差异(P<0.05); 当雄雄相遇中成虫是初次相遇时, 在发生打斗的频率上显著高于再次相遇(P<0.05), 成虫在雄雄相遇发生避让的频率上, 再次相遇显著高于初次相遇(P<0.05), 雌雄成虫初次相遇发生交配的频率显著高于再次相遇的频率(P<0.05)。云斑天牛成虫相遇行为的研究为研究云斑天牛召唤机制、 性信息素的生物合成及成虫繁殖行为学提供了依据。     

亲缘关系与布氏田鼠双亲行为和杀婴行为关系的初探

根据幼仔发育的 5个阶段 :新生 (1～ 5日龄 )、耳立 (6～ 9日龄 )、睁眼 (10～14日龄 )、出巢 (15～ 2 0日龄 )和断奶 (2 1～2 4日龄 ) ,通过观察布氏田鼠对自己幼仔 (r=0 5 0 )和非亲缘幼仔 (r <0 12 5 )的行为反应 ,研究亲缘关系对布氏田鼠双亲和杀婴行为的影响。结果表明 :1)新生阶段 ,雄鼠抚育亲仔的时间显著多于非亲缘幼仔 ;断奶阶段 ,雄鼠与亲仔相触及在巢内活动的时间也显著多于非亲缘幼仔 ;雄鼠在耳立、出巢和断奶阶段嗅闻非亲缘幼仔 ,以及在新生和睁眼阶段修饰非亲缘幼仔的时间都显著多于亲仔。 2 )断奶阶段 ,雌鼠与亲仔相触的时间显著多于非亲缘幼仔 ,但在睁眼阶段修饰非亲缘幼仔 ,以及在新生、耳立和出巢阶段嗅闻非亲缘幼仔的时间显著多于亲仔。 3)雌雄鼠在15日龄前没有杀婴行为 ,15日龄后 ,开始对非亲缘幼仔发生杀婴行为 ;雌鼠杀婴行为受幼仔发育的显著影响 ,且杀婴频次显著高于雄鼠 ;雌鼠在断奶阶段对非亲缘幼仔的杀婴频次显著高于亲仔。综上所述 ,亲缘关系对布氏田鼠的双亲和杀婴行为有显著影响 ,这可能与个体间的已往经历 (熟悉性等 )或表现性匹配等辨别机制有关。     

雌性黄山短尾猴回避近亲交配

本研究分别在交配期(2006年9月-2006年12月)和产仔期(2007年1月-2007年4月)对黄山短尾猴鱼鳞坑YA1群中5只雄猴和5只雌猴成年个体采用目标动物法、随机取样法和连续记录法记录行为参数。研究期间记录交配行为336例:母子交配0例;母系兄妹交配7例(占2.1%),其中强行交配4例;非亲缘关系交配329例(占97.9%),非亲缘关系交配频次显著高于亲缘关系。在交配期,雄猴对亲缘雌猴跟随、性检查频次均低于非亲缘雌猴,接近指数(PMI)在亲缘和非亲缘雌猴间无显著性差异;雌猴对亲缘雄猴交配拒绝率显著高于非亲缘雄猴,接近指数在交配期显著低于非亲缘雄猴,产仔期接近指数在亲缘和非亲缘雄猴间无显著性差异。尽管雄猴在交配选择上趋于避免与亲缘雌猴交配,但某些雄猴仍会主动对有亲缘关系的雌猴邀配或强行交配,雌猴则主动回避。这些结果表明:黄山短尾猴母系亲属间可以通过行为倾向抑制近亲交配发生,且雌猴更主动回避交配,支持了近交回避的双亲投资理论。     

布氏田鼠的双亲行为比较

在实验室对布氏田鼠双亲行为和幼仔发育的研究表明, 雌性布氏田鼠的修饰、筑巢和摄食行为显著地多于雄鼠, 且这些差异多集中在幼仔发育的最初9 d 内。雌鼠的修饰、筑巢行为以及在巢内的时间与幼仔发育日龄呈显著地负相关, 而雄鼠的这些行为无显著变化。但雌雄的衔回行为却与幼仔发育日龄呈显著地正相关。据此认为雌性布氏田鼠的双亲行为多于雄鼠, 符合双亲投资的理论。     

罗汉松雌雄株叶形态结构的比较研究

该研究以雌雄异株植物罗汉松(Podocarpus macrophyllus)成熟叶为研究材料,采用光学显微镜、扫描电镜和透射电镜观察比较罗汉松雌、雄植株叶在形态、显微结构和超显微结构的差异,以明确罗汉松雌、雄株在进化过程中叶对环境功能的适应性。结果显示:(1)罗汉松雌株的叶片大于雄株,且两者的叶长、叶宽和叶柄长差异极显著,而叶柄厚、叶面积、叶体积、叶质量、比叶重(SLW)、面积与体积之比(A/V)等性状无显著差异。(2)雌株叶片的气孔相对较大,密度较高,且雌株气孔宽度极显著大于雄株;雌株叶片的上表皮长细胞宽度和下表皮短细胞宽度均显著大于雄株,但雌株叶片的上表皮长细胞和短细胞的长度则显著小于雄株。(3)罗汉松雌株叶片的栅栏组织厚度、海绵组织厚度、传输组织长度和宽度、上下角质层厚度、维管束厚度、叶片紧密度(CTR)及疏松度(SR)均极显著大于雄株,而雌株的下表皮厚度极显著小于雄株,但雌雄株叶片的上表皮细胞厚度和栅海比差异不显著;雌株叶片的栅栏组织细胞、叶绿体和线粒体均较雄株的长而细,且雌株的线粒体宽度极显著小于雄株。(4)罗汉松雌株叶片上表皮蜡质饰纹、下表皮角质层纹饰、气孔外拱盖纹饰及内缘类型等4个微形态特征与雄株差异明显。(5)叶表皮蜡质层能谱分析表明,罗汉松雌株叶片含有9种元素,而雄株叶片仅有8种(缺少K元素);且雌株的Si元素含量高于雄株,而雄株的C、O、Na、Mg、Al、Ca和Au元素含量均高于雌株。研究表明,罗汉松雌、雄植株之间存在明显的第二性征,雌株叶片结构有助于提高光合等性能以满足生殖需求;罗汉松雌、雄株叶形态结构的差异是其长期进化形成的有利于物种繁衍的适应策略。     

低盐度海水和淡水对中华绒螯蟹性腺发育及交配行为的影响

研究了低盐度海水(盐度为15)和淡水(盐度为0)对中华绒螯蟹(Eriocheir sinensis,以下简称河蟹)性腺发育及交配行为的影响,并比较了河蟹交配和产卵前后的性腺指数及肝胰腺指数的变化。实验分为4组,分别为低盐度海水雌蟹组、淡水雌蟹组、低盐度海水雄蟹组和淡水雄蟹组。结果表明,(1)各组河蟹的成活率均在80%左右,无显著差异(P>0.05);(2)实验第15天、30天和45天时,低盐度海水雌蟹组的卵巢指数显著高于淡水雌蟹组(P<0.05),低盐度海水雄蟹组的性腺指数也略高于淡水雄蟹组,但差异不显著(P>0.05);(3)实验第30天时,低盐度海水雌蟹组的肝胰腺指数显著低于淡水雌蟹组(P<0.05),其余采样时间两组雌体间或两组雄体间的肝胰腺指数差异不显著(P>0.05),实验期间,两组雌体的肝胰腺指数均显著下降(P<0.05);(4)实验第45天,低盐度海水雌蟹组和雄蟹组实验个体全部能够交配,有66.7%的低盐度海水雌蟹组的个体交配后2 d内产卵,淡水雄蟹组有部分个体在低盐度海水中有发情行为;(5)低盐度海水组,雌蟹产卵后和雄蟹交配后的性腺指数均显著下降(P<0.05),但肝胰腺指数下降不显著(P>0.05)。     

薜荔榕小蜂对薜荔和爱玉子雌花期榕果挥发物的行为反应

薜荔和爱玉子均属雌雄异株桑科榕属植物,两者互为原变种与变种的关系,分别与薜荔传粉小蜂和爱玉子传粉小蜂(二者互为隐存种)建立了专性共生关系,榕树榕果挥发物在维系传粉小蜂与其寄主的共生关系上起着重要作用。利用Y型嗅觉仪测定薜荔榕小蜂(薜荔和爱玉子的传粉小蜂)对薜荔和爱玉子雌花期榕果挥发物的行为反应。结果表明:(1)雌花期果型的大小对薜荔榕小蜂行为反应无显著影响,薜荔大、小果型雌花期雌(雄)榕果挥发物对其传粉小蜂均具有强烈的吸引作用;(2)榕果挥发物浓度影响薜荔榕小蜂行为反应,薜荔、爱玉子雌花期雌(雄)榕果挥发物对其传粉小蜂的吸引作用均可能存在阈值反应,即榕果挥发物浓度未超过阈值时,雌花期榕果挥发物对传粉小蜂的吸引作用与挥发物浓度成正相关关系,而一旦超过阈值,榕果挥发物对传粉蜂的吸引作用显著下降,表明寄主榕果挥发物浓度影响传粉小蜂的寄主定位;(3)薜荔传粉小蜂对低浓度爱玉子雌花期雌(雄)榕果挥发物、爱玉子传粉小蜂对低浓度薜荔雌花期雌(雄)榕果挥发物均既无趋向也无驱避行为;薜荔传粉小蜂对高浓度的爱玉子雌花期雌(雄)榕果挥发物表现为显著的驱避行为,而爱玉子传粉小蜂对高浓度薜荔雌(雄)雌花期榕果挥发物表现为显著的趋向行为,因此,薜荔传粉小蜂与爱玉子传粉小蜂存在寄主专一性不对称现象,爱玉子传粉小蜂进入薜荔雌(雄)果内传粉或产卵的可能性较大,而福州地区的薜荔传粉小蜂可能难以进入爱玉子雌(雄)果内传粉或产卵。本研究结果将为榕-蜂共生体系的化学生态学理论研究以及爱玉子栽培提供科学依据。     

南滑蜥繁殖行为和繁殖策略的研究

南滑蜥Scincella reevesii 系温暖气候区卵胎生蜥蜴,每年繁殖1次,繁殖季节为5月下旬到6月上旬.平均每只繁殖雌蜥产仔6(3～9)条.雌蜥分娩持续时间为30～ 60 min,仔蜥在产出时包被卵膜.南滑蜥雌体采取高投入的繁殖策略,平均繁殖投入为0.359,平均窝仔投人为0.247.相关性回归分析表明,窝仔数、窝仔重与雌蜥体长呈正相关关系,幼仔重与雌蜥体长不相关;窝仔数与雌蜥的繁殖投入及窝仔投入均成正相关,与分娩时的能耗投入不相关,与幼仔投入成显著负相关.     

白头鹤孵卵后期的行为节律观察

作者于2003~2004年连续2年的4月末至5月初在黑龙江大沾河湿地自然保护区,对3对野生白头鹤(Grus monacha)的孵卵过程进行了定点观察,结果表明,白头鹤的卧巢行为(t=-4.92,P=0.00)和护巢行为(t=3.09,P=0.007)在雌、雄个体间存在极显著差异;不同孵卵阶段的卧巢行为(t=2.95,P<0.01)、护巢行为(t=4.29,P<0.01)和育雏行为(t=-6.79,P<0.01)表现出不同的节律性。天气状况是影响白头鹤孵卵期各行为的重要因素,晴天时的凉卵行为(t=1.55,P<0.01)和育雏行为(t=4.06,P>0.01)时间明显多于阴雨天。对雌、雄个体行为同时进行观察的结果表明,雌(雄)鹤卧巢行为的时间与雄(雌)鹤护巢行为的时间呈显著正相关(相关系数分别为R=0.94和R=0.86)。     

LHRH - Induced ovulation and fertility of anestrous goats

Seventeen female mature anestrous does were used to study the effect of luteinizing hormone-releasing hormone (LHRH) on ovulation (Experiment I) and on fertility rate and blood estrogen/progesterone concentrations (Experiment II). Laparotomy after day 8 of treatment with a single injection of LHRH (300 ug) and estradiol cypionate (0.2 mg/kg) revealed evidence of ovulation in two out of three and a developed follicle in the third. Similar treatment to six does in Experiment II, when followed by natural mating with a fertile buck, produced pregnancy in two does, pseudopregnancy in two and no effect (nonpregnancy) in the remaining two animals. The pregnant does had normal parturition after 148 to 150 days of gestation. In pregnant does, blood progesterone levels first showed a gradual increase until day 130 (10.07 ng/ml) and then declined sharply at 48 hours before parturition. Estrogen concentration, on the other hand, failed to increase until day 80, and thereafter it reached a peak (1800 pg/ml) at 24 hours prior to parturition; the level declined sharply at 24 hours after parturition. In pseudopregnant does, progesterone levels remained in close proximity with those of pregnant does until day 90, when they started to decline.     

圈养小熊猫繁殖行为变化及繁殖行为对策

In order to investigate the change of reproductive behaviors and understand reproductive strategies of both male and female red pandas, one-year behavioral observation was conducted through the focal sampling method in the Chengdu Research Base of Giant Panda Breeding from December 1999 to November 2000. Our results indicated that reproductive behaviors showed significant differences between the estrous and non-estrous seasons. Frequencies of the rubbing anogenital, sniffing and licking marking were much higher in estrus than in non-estrus. Bleating only appeared in the estrus and can be regarded as an estrous indicator.The result also demonstrated that both male and females applied different reproductive behavioral strategies. Frequencies of activity, rubbing anogenital, licking and sniffing marking, and bleat were much higher in the male than in the female. However, those of resting and investigating were much lower in the male than in the female. This indicated that the male was more active than the female during the estrus and might imply that the male acts mainly as an estrous message sender, and the female as a message receiver in the estrous season.     

Sexual behaviour and its olfactory control in the desert woodrat (Neotoma lepida lepida)

In studies 1 and 2 nine pairs of desert woodrats (Neotoma lepida lepida) were observed for copulatory behaviour when the female was in a state of naturally occurring oestrus (study 1) and following ovariectomy and oestrogen and progesterone replacement (study 2). Males and females respond in a similar way under conditions of natural and hormone-induced oestrus. Males show a consummatory pattern involving multiple mounts and ejaculations, with ejaculations occurring after single intromissions. Females show the lordosis reflex accompanied by hop-and-dart and ear-wiggling responses. In addition, both sexes show appetitive precopulatory behaviours; the male emits an audible rasping vocalization as he trails and mounts the female, following a period of intense sniffing of the female's anogenital region. The female also frequently approaches and sniffs the male. In study 3, the role of female odours in the sexual behaviour of the male was examined in eight of the nine pairs used in studies 1 and 2. This was done by applying to the anogenital region of ovariectomized females a combination of urine and vaginal secretions taken from familiar and unfamiliar, and oestrogen-primed or non-oestrogen-primed females. The results show that odours from oestrogen-primed females are not sufficient to elicit male sexual behaviour, if the female is not sexually active. In study 4 the eight males were tested for their preferences for urine and vaginal secretion odours taken from females in different reproductive states and applied to cotton swabs. These males spent more time sniffing unfamiliar oestrous odours than unfamiliar non-oestrous odours and more time sniffing oestrous odours from a familiar female over those taken from an unfamiliar female.In study 5, 12 sexually active males were tested with oestrogen-primed females before and after either olfactory bulb removal or sham-surgery. Bulbectomized animals ceased copulating with females although females showed precopulatory approaches.Taken together, these studies suggest that normal sexual behaviour in the male woodrat requires that the female both possess the attractive odours (of oestrus) and that she engage in appetitive precopulatory behaviour.     

半散放东北虎产仔行为的初步观察

1999年4月至2003年6月,采用随机取样法、扫描取样法和目标取样法对黑龙江东北虎林园半散放条件12只成年雌性东北虎的产仔行为进行观察。结果表明,半散放雌性东北虎的产仔行为可分为9种:站立、行走、躺卧、嗅闻、努责、梳理、生产、亲仔和舔食。雌性东北虎的躺卧和亲仔行为时间最长,分别为42.9% 和34.5% ;躺卧、努责和亲仔行为发生频率较高,分别为21.1%、16. 9% 和24.6%。单因素方差分析表明,不同雌性东北虎个体间躺卧、亲仔等行为有显著差异;不同年份雌性成年东北虎的站立、躺卧、梳理等产仔行为也具有显著差异。相关分析显示,躺卧行为与亲子行为(r_s= 0.602, P<0.05)、梳理行为(r_s=0.589,P<0.05)均呈负相关。     

Pre- and post-farrowing behaviour in primiparous domesticated pigs

The pre- and post-farrowing behaviour in 8 free and 7 tethered Dutch Landrace gilts was studied and recorded by time-lapse video and focal observations from 6 days before until 6 days after parturition. Farrowing strongly influenced behaviours such as rooting, sniffing, foraging and chewing (Group 1). In tethered gilts, rooting at, sniffing at, head on bars, grinding and biting at (Group 2) were also influenced by farrowing. It is argued that Group 2 behaviours are re-directed Group 1 behaviours and should therefore be evaluated as abnormal. On certain days before and after farrowing, significant differences between free and tethered gilts existed for nest-building behaviour, comfort behaviour and maternal attention.Results indicate that large and persistent individual differences exist in activity levels between gilts. It is proposed that the observed large individual differences for Group 2 behaviours in tethered gilts may indicate that in the same housing conditions, some animals suffer more than others.     

Evidence of ovulation in goats (Capra hircus ) with short estrous cycle and its occurrence in the tropics

The influence of season and exposure to buck on the length of the estrous cycle were determined in 32 normally cycling native goats of different ages and parity. The estrous cycle durations were classified as short, medium and long. Ten goats (31%) exhibited medium length estrous cycles; 22 animals (69%) exhibited a combination of short, medium and long estrous cycles. Of the 155 estrous cycles studied, 15% were short, 72% were medium and 13% were long. Short estrous cycles were significantly shorter (P < 0.01) in estrus duration than medium or long estrous cycles. Significant differences (P < 0.05) for estrous cycle length and estrus duration were found between does but not within does. The presence of a buck for 8 to 16 h showed no significant effect on the length of the estrous cycle or on estrus duration, but a 24-h exposure period to a buck yielded shorter estrous cycles and estrus duration than found in the unexposed control group. Estrous cycles were significantly shorter (P < 0.01) in October, when rainfall is 57.9% of the annual total, and significantly longer (P < 0.01) in February, when rainfall is low at 0.2% of the annual total. A negative linear relationship (r = -0.87) was observed between estrous cycle and rainfall. Twenty-eight (90.3 %) of the short estrous cycles were ovulatory. The short cycles had a relatively lower ovulation rate than medium and long estrous cycles. The results indicate that the short estrous cycle in goats is associated with ovulation, and its occurrence in the tropics is related to rainfall.     

Controlled doe exposure as biostimulation of buck rabbits

Female exposure of males could be a low-cost biostimulation option that benefits AI in commercial rabbit operations by improving buck rabbits reproductive performance. The objective of the study was to evaluate exposure of buck rabbits to females as a biostimulation option to improve reproductive potential. Treatments were: exposure (biostimulated) or not (control) of bucks to does. Bucks were New Zealand White, 15-month-old, sexually experienced and fertile. Experimental design was completely random with nine replications, experimental unit was one buck. Doe exposure was permanent using replacement pubertal does housed in an adjacent wire-mesh cage and changed for new ones every other week. Semen collection lasted 14 weeks (late winter and early spring) twice a week with two ejaculates at each collection. Analyses of variance were under a mixed model: treatments, ejaculate number and season were fixed and rabbit random effects and buck weight at each collection as covariable. Biostimulated bucks showed greater (P<0.05) reproductive potential due to: 7% lesser reaction time (greater libido); and increased semen volume (40%), sperm motility (29%), sperm per ejaculate (31%), normal alive motile sperm (65%) and number of semen doses (64%). Semen characteristics differed by season in control bucks but not in doe exposed bucks (treatment × ejaculate number, P<0.05). Reproductive potential in spring was greater (P<0.05) than in winter in both treatments. Doe exposure is a biostimulation method that improves sexual drive and sperm production and quality of buck rabbits.     

Decline of sexual behavior in castrated male rats: Effects of female precopulatory behavior

From the population of 89 adult sexually inexperienced Wistar male rats 20 animals that initiated copulatory behavior with females exhibiting low intensity of precopulatory behavior (presenting females) were preselected. Prior to castration all 20 males had the same sexual experience: three ejaculatory series in four weekly sessions with females exhibiting high intensity of precopulatory behavior (darting females). Following castration, the decline of copulatory behavior was much slower for the nine males tested with darting females as compared to the 11 males tested with presenting females. Male precopulatory behaviors (anogenital sniffing, touching flanks, etc) outlasted the loss of copulatory behavior and seem to be less dependent on both external and internal determinants. It is concluded that intensive external sexual stimuli can function to compensate, and therefore mask, the subnormal operation of androgen-dependent mechanisms in initiating the copulatory behavior.     

Maturation of sexual behavior in laboratory male mice: a role of genotype

Sexual behaviour and testosterone output in response to a receptive female were investigated in male mice of three inbred strains BALB/cLac, CBA/Lac and PT at puberty (45 days of age) and in adulthood (90 days of age). The animals were exposed for 10 min to a receptive female separated by a plastic grill, which would not allow contact between male and female. Male and female behaviour was recorded by measuring the time the male or female spent at the grill and the number of approaches to it (sexual motivation). The grill was then removed and the number of mounts and chemoinvestigatory behavior towards a female (nasal and anogenital sniffing) was recorded for each male. An increase in serum concentration and testicular content of testosterone was used as an endocrine index of the sensitivity to female pheromones. It has been shown the significant genotype and developmental effects on sexual behaviour and the hormonal response to sexual stimuli. The pubertal BALB/cLac males were characterised by the adult pattern of sexual motivation, chemoinvestigatory behaviour and the evident testosterone respond to a female. Males of the strain PT showed the lowest sexual motivation, chemoinvestigatory behavior towards a receptive female and no testosterone responses at both ages. This is a very different situation with the CBA/Lac's who showed the developmental increase in the sexual motivation, sniffing behaviour and the endocrine reflex, and the highest level of sexual behaviour but the moderate testosterone respond to a female at adulthood. The data obtained suggest genotype related asynchrony in maturation of the olfactory system, pituitary-gonadal axis and neural circuits of sexual behavior, and their independent genetic control. So, the set of mice strains investigated represents a useful tool for genetic and endocrine study of sexual behavior and the chemosensory control of testicular steroidogenesis.     

Dexamethasone and estradiol benzoate induced parturition in dairy cattle

Fifteen 2-year-old Holstein cows and 21 mature Holstein cows were assigned to one of three groups. Cows in Group I calved spontaneously. Cows in Groups II and III received single intramuscular injections of 20 mg dexamethasone and 25 mg estradiol benzoate to induce parturition prematurely. In addition, cows in Group III received a single intramuscular injection of 12.5 mg estradiol benzoate 48 hr prior to dexamethasone and estradiol benzoate. The objective of the experiment was to determine the effectiveness of estradiol benzoate in combination with dexamethasone on traits at parturition and on productive and reproductive characteristics following parturition. Induction of parturition shortened gestation length and increased the incidence of retained placentas (both P < .01). All induced cows calved between 21 and 59 hr postinjection with less (P < .05) udder edema when compared to control cows. Mean plasma estrogen concentrations, using an assay system which does not measure estradiol benzoate, were not different among groups following injections of estradiol benzoate. Mean estradiol-17β concentrations in induced cows, however, using an assay system which does recognize estradiol benzoate (70.8% crossreactivity), were higher (P < .01) following estradiol benzoate injection, tended to be higher through parturition, and remained elevated (P < .01) at 12 and 24 hr following parturition when compared to cows calving spontaneously. Mean monthly milk production and the 2x, 305-ME records for milk, fat and FCM were not different among groups.