Postpartum Interval Research Articles

Prepartum supplementation effects on growth and fertility in Bos indicus-cross cows

Summary. Three experiments were conducted in the dry tropics of north Australia using Bos indicus-cross cows. Cows in mid–late pregnancy were either unsupplemented during the late dry season or offered ad libitum (2 kg/day) molasses with 7.4% urea (w/w) (M8U) or cottonseed meal (1 kg/day) for up to 54 days commencing 2 months before the start of the calving season. Supplementation reduced weight loss in experiments 1 and 2 (P<0.05), but had no significant effect on weight or body condition in experiment 3. Supplementation had no effect on subsequent calf growth or cow lactation yields. Following early wet season rains in experiment 1, 9 and 49% of cows were ovulating 40 and 80 days post-partum, respectively, with no effect of supplementation. In experiment 2, 10 and 100% of cows had ovulated by 60 and 200 days post-partum, respectively. At any time between 80 and 180 days post-partum, supplemented cows were more likely to be cycling (P<0.05), independent of supplementation effects on weight or body condition. The average post-partum interval to oestrus was 30 days less in cows supplemented for 42 days (P = 0.08). In experiment 3, pregnancy rates in 1/2 and 3/4 Brahmans supplemented with M8U for 54 days (MU54) or whose calves were weaned at 2–3 months of age (WEAN) were 14% higher in the latter 2 months of mating than in cows supplemented for less than 40 days. Good seasonal conditions resulted in high pregnancy rates in all mature 5/8 Brahmans; when not weaned early, their average calving to conception interval (CCI) was 54 days (s.e. = 8.5 days). Pregnancy rates of first-lactation 5/8 Brahmans (average CCI of 125 days) supplemented for 39 days or less and weaned when calves averaged 6 months of age were 14–32% lower between 2 and 9 months post-partum than in contemporaries in the MU54 or WEAN treatment groups. It was concluded that dry-season supplementation of mid- to late-pregnant Bos indicus-cross cows with an energy concentrate for 42–54 days (‘spike’ feeding) may reduce post-partum anoestrus intervals via a mechanism which is not dependent on the effects on weight or body condition.

Effects of porcine relaxin on induced parturition in beef heifers

Two-year-old crossbred beef heifers were used to test the effects of porcine relaxin (pRelaxin) alone, or in combination with dexamethasone, on the induction of parturition, the incidence of dystocia, and retained placentas. Effects of treatment on pelvic area, postpartum interval, milk production, colostrum quality, calf birth weight, calf vigor, and calf performance were also evaluated. On Day 275 of gestation, heifers from two fetal-sire groups were randomly assigned to one of four groups in a 2 × 2 factorial design and received: no treatment (controls, n = 19), 20 mg of dexamethasone intramuscularly (im) (n = 22), 5 mg of pRelaxin (3,000 U/mg) im (n = 19), or 20 mg of dexamethasone plus 5 mg of pRelaxin (n = 17). Length of gestation (in days) was less (P < 0.05) in heifers treated with dexamethasone (279.8 ± 1.0) than in controls (286.6 ± 0.9), but was not influenced (P > 0.05) by treatment with pRelaxin. The incidence of retained placentas in heifers treated only with dexamethasone (27.3%) was not reduced by concomitant treatment with pRelaxin (35.3%). Retained placentas were not observed in any control heifers and in only one heifer (5.2%) treated solely with pRelaxin. Ease of calving (1 = unassisted, 5 = abnormal presentation) was not influenced by treatment (P > 0.05), even though birth weights (in kilograms) of calves from heifers treated with dexamethasone (36.4 ± 0.8) were less (P < .01) than those of calves from nondexamethasone-treated heifers (39.2 ± 0.8). Dexamethasone tended to reduce (P < 0.07) calf vigor (1 = healthy and strong, 5 = dead on arrival; 1.48 ± 0.11 vs. 1.18 ± 0.11), but was not (P > 0.05) influenced by pRelaxin. The duration of the postpartum anestrous interval (73.1 ± 1.8 d across groups) and pelvic areas following treatment and parturition were not influenced (P > 0.05) by dexamethasone or pRelaxin. Although determinants of colostrum quality (P < 0.01) and quantity (P < 0.08) of milk produced were influenced by dexamethasone, adjusted 205-d weights of calves did not differ (P > 0.05) among groups. In conclusion, treatment with pRelaxin alone failed to induce parturition or, when combined with dexamethasone, to reduce the incidence of retained placentas.

Effect of Protein Level During Late Gestation on Weight Change and Calving Characteristics of First Calf Heifers

AbstractSixty-six Angus x Gelbvieh heifers were used to determine the effects of protein intake during the last one-third of gestation on heifer weight change, body condition score, and calving characteristics. Heifers were randomized to 1 of 12 groups of either five or six animals, then groups were randomized to one of four dietary protein levels with three replications of each diet. Diets were calculated to be isocaloric and to supply either 75, 100, 150, or 200% of NRC protein requirements for heifers in the last one-third of gestation. Experimental diets were fed for 77 d. At 1 wk before the first estimated calving date, all heifers were grouped in one lot and fed a diet calculated to meet NRC requirements for lactating heifers. Heifer weights and body condition scores (1 to 9 scale) were recorded at the beginning and end of the experimental feeding period after 16-h feed removal. Replicate means were analyzed using a general linear model. Protein intake level had no effect (p>0.10) on calf birth weight, weaning weight, adjusted 205-d weight, calving ease score, calf vigor score, or postpartum interval to estrus. Birth weights were 37, 39, 38, and 40 ± 1lb for 75, 100, 150, and 200% protein intake levels (p=0.28), respectively. Dietary protein intake level did not affect heifer weight change (p=0.27) during the study (22, 44, 43, and 36 ± 8lb for 75, 100, 150, and 200% protein intake levels, respectively). Dietary protein treatments also did not affect dystocia (p=0.58) or postpartum interval (P=0.93). In summary, protein intake levels as high as 200% of recommended NRC requirements during late gestation did not affect calving difficulty, birth weight, or postpartum interval to estrus in first-calf heifers.

Effects of post-partum energy intake and calf isolation on follicle dynamics and post-partum interval of beef cows

Reproduction is the main factor limiting the production efficiency of beef suckler cows and the prolonged post-partum interval is a major factor contributing to this poor reproductive performance. This interval is determined by a number of factors of which nutrition and the suckling effects of a calf are the most important. The aims of this experiment were to determine the effects of energy level post-partum and suckling on the PPI of cows in a low to moderate body condition at calving

Effects of post-partum energy intake and calf isolation on follicle dynamics and post-partum interval of beef cows

Reproduction is the main factor limiting the production efficiency of beef suckler cows and the prolonged post-partum interval is a major factor contributing to this poor reproductive performance. This interval is determined by a number of factors of which nutrition and the suckling effects of a calf are the most important. The aims of this experiment were to determine the effects of energy level post-partum and suckling on the PPI of cows in a low to moderate body condition at calving

Relationships between energy balance and post-partum ovarian activity and fertility in first lactation dairy cows

AbstractForty primiparous Holstein dairy cows were monitored from calving through 100 days in milk to evaluate the effect of energy balance in the early post-partum period on subsequent fertility. The post-partum interval to first ovulation (R2 = 0·41; P &lt; 0·005) was lengthened by greater negative energy balance, and reduced by greater body weight at parturition or decreased body-weight loss during the experimental period. Luteal activity (R2 = 0·58; P &lt; 0·0001), measured by plasma progesterone area under curve, was increased in the first cycle post partum by a shorter interval to first ovulation, improved energy balance during the 1st week of lactation and by decreased body-weight loss. Pregnancy status following first artificial insemination was related positively to the number of ovulations before insemination, improved energy balance during the 1st month post partum, fewer days to first ovulation and greater body weight at calving. These data suggest that energy balance and body weight are important in determining the post-partum interval to first ovulation and the subsequent fertility of first lactation dairy cotes.

Reducing post-partum anoestrous interval in first-calf Bos indicus crossbred beef heifers. III. Effect of nutrition on responses to weaning and associated variation in metabolic hormone levels

Interactions between effects of undernutrition and weaning on the duration of post-partum anoestrus and associated variation in milk yield, suckling behaviour, and metabolic hormone levels in Droughtmaster [Bos indicus x Bos taurus (518, 3/8)] first-calf cows were studied in 2 successive years. Low body condition score at calving (3.5f 0.1, scale 1-9) was associated with prolonged post-partum anoestrous intervals in suckled cows, but provided cows were maintaining liveweight, ovarian cyclicity resumed within 50 days if calves were weaned 70 days post-partum. This response to weaning was totally inhibited in cows that calved in low body condition that lost liveweight post-partum (Year 1). In contrast, marked levels of post-partum liveweight loss (23%) did not affect resumption of ovarian cyclicity in response to weaning (at 50 days post-parturn), or time to conception, among cows that calved with high body condition scores (5.8 � 0.2, Year 2). Reduced milk yields and calf weight gains among underfed cows were associated with higher suckling frequencies and durations ( P &lt; 0.05). Acyclic interval after weaning was negatively related to body condition score at weaning (P &lt; 0.01), and positively related to preweaning suckling intensity (P &lt; 0.01). The time taken to resume ovarian cyclicity after weaning increased by a factor of 1.2 for every half unit decrease in body condition score at weaning, and by a factor of 1.3 for every 30-min increase in time suckled per day prior to weaning. Within level of nutrition, higher frequencies and durations of suckling were associated with higher plasma prolactin levels. Plasma IGF-1 levels were consistently depressed in underfed cows, whereas plasma insulin and GH levels were less affected by nutritional treatments. Effects of undernutrition in suckled cows appear to operate at least partly through interactions with milk yield and suckling intensity. Management of post-partum anoestrus in Bos indicus cows should focus on the conservation of cow body condition and on the strategic use of early weaning.

Ewe fertility in the STAR accelerated lambing system.

Effects of environmental factors such as ewe age, season of exposure, and time from lambing to exposure on fertility were evaluated using records on 1,084 Dorset ewes in the STAR accelerated lambing system. The STAR program consisted of five 30-d concurrent breeding and lambing periods per year beginning on January 1, March 15, May 27, August 8, and October 20. Fertility in the flock changed in a cyclic and predictable fashion during the year. Changes in prolificacy were less consistent but also tended to show cyclic variation. Matings that occurred within the typical breeding season (August, October, and January) were more fertile than those occurring in March and June. However, fertility also varied with the age of the ewe and the time since the ewe's last lambing. Except in June, fertility at the first postpartum mating increased as ewes aged. In March and June matings, adult ewes that had just weaned lambs were less fertile than ewes that had failed to conceive in the previous season and therefore had longer postpartum intervals. However, in October and January, ewes that had just weaned lambs were more fertile. A matrix of expected pregnancy rates, or probabilities of fertility, was constructed using a mixed GLM to describe the combined effect of season, ewe age, and time since lambing on ewe fertility in accelerated lambing.

Acute and chronic changes in luteinizing hormone secretion and postpartum interval to estrus in first-calf suckled beef cows exposed continuously or intermittently to mature bulls.

The objective of this study was to determine whether patterns of LH secretion are acutely or chronically affected by the presence of mature bulls in postpartum first-calf suckled beef cows exposed to bulls either continuously or intermittently beginning on d 30 after birth. Crossbred cows were assigned randomly to be either continuously exposed to (BE; n = 20) or isolated from bulls (NE; n = 32) at calving, or exposed continuously (NEBE; n = 10) or intermittently (BEI; n = 21) to bulls beginning on d 30. The BEI cows were exposed to bulls for 2 h every 3rd d for 18 d. Ten cows from the NEBE, BEI, and NE treatments only were fitted with indwelling jugular catheters. Intensive blood sampling of NEBE and BEI cows began within 45 min after they were placed with bulls for 2 h on d 30, and for BEI cows on each d after 2 h exposure. Samples were collected at 15-min intervals for 6 h beginning on d 30 for NEBE, BEI, and NE cows; sampling continued at 3-d intervals until d 48. Samples were assayed for LH by RIA. Cows were observed twice daily (am:pm) for estrus. More (P = .07) BE and NEBE (75%) cows showed estrus by the end of the study than BEI and NE cows (48%). Interval to estrus was longer (P < .05) in BEI and NE cows (95.6 +/- 6.1 d) than in BE and NEBE cows (75.9 +/- 6.1 d). Baseline LH and amplitude and interpeak interval of LH peaks during the first 6 h after 2 h of bull exposure did not differ (P > .10) among treatments on d 30 after birth. However, mean LH and LH pulse frequency were higher (P = .06) for NEBE and BEI cows than in NE cows. Baseline LH and amplitude and duration of LH peaks did not differ (P > .10) over the seven sampling periods among NEBE, BEI, or NE cows. Mean LH and LH pulse frequency were higher (P < .05) in NEBE and BEI cows than in NE cows on each sampling period. Exposing first-calf suckled beef cows to bulls on d 30 after birth increased mean LH concentrations by increasing pulse frequency within a short period after a 2-h exposure. Thereafter, mean LH concentrations were higher in cows that were either continuously or intermittently exposed to bulls. Although mean LH and LH pulse frequency in NEBE and BEI cows were similar, intervals to estrus after bull exposure differed between treatments. The mechanism whereby bulls alter postpartum interval to estrus seems to involve other factors that may be related to but not directly linked with LH secretion.

Alterations in hypophysial responsiveness to synthetic GnRH at different postpartum intervals in Murrah buffalo ( [formula omitted

The objective of this study was to investigate the hypophysial responsiveness to GnRH at different intervals post partum in Murrah buffalo. Plasma LH and FSH levels were measured at 1 h before and upto 6 h subsequent to the administration of GnRH (1 ug/kg body weight) or saline on Days 2, 20 and 35 post partum in 2 groups of buffalo (n=4 each). Plasma progesterone levels were measured in samples collected once daily from Day 3 to Day 46 post partum. Pretreatment basal LH levels exhibited a progressive increase from Day 2 through Day 35 post partum, while the basal FSH levels increased only until Day 20 post partum. Following a highly subdued LH response to GnRH on Day 2 post partum, a 408% increase (P < 0.01) was observed in the total LH released in response to GnRH on Day 20 post partum, followed by a 20% reduction (non-significant) over Days 20 to 35 post partum. The interval from parturition was highly correlated with total LH released (r = 0.711, P < 0.01). Unlike LH, a substantial amount of FSH was released following GnRH treatment on Day 2 post partum, which was not significantly different from the FSH response on Days 20 and 35 post partum. The LH and FSH response to GnRH was not significantly different between animals in which luteal activity resumed and in those which showed no luteal activity post partum. While pointing to a dramatic enhancement in the hypophysial responsiveness to GnRH between Days 2 and 20 post partum, these results suggest that pituitary responsiveness to GnRH does not appear to be the limiting factor for resumption of estrous cycles by Day 35 post partum in Murrah buffalo.

Assessment of selenium status in mares and foals under practical management conditions

Summary Thirty gravid mares of different breeds and in steady-state selenium (Se) nutrition were used to demonstrate a significant positive correlation between blood Se concentration and glutathione peroxidase (GSH-Px) activity. The relationship between blood Se and GSH-Px activity was higher in mares than in foals at parturition. The Se status of foals was also significantly correlated with that of the respective mares at parturition under practical management conditions where wide variations in dietary Se during gestation were present. Selenium concentration of milk was less than one-fourth of that in colostrum within one day postpartum and was considered a minor source of Se for the foals regardless of Se status of the mares during gestation. There were no significant differences in blood Se concentration between mares and foals of low Se status at parturition or during a 4-week postpartum interval. For mare/foal pairs of adequate Se status, however, the differences were significant throughout the experimental period. Foals in this group had higher blood Se concentration than either foals or mares of low Se status. Plasma vitamin E concentration was elevated 3–4 fold in all foals by 1 day postpartum, following colostrum ingestion, and was independent of the Se status of their dams. We did not observe clinical signs of white muscle disease during a 4-week postpartum period or differences in serum enzymes indicative of muscle damage in any of the foals regardless of their Se status.

Factors influencing the success of transcervical insemination in Merino ewes

The experiments described examined the effects of a number of factors on the level of uterine insemination achieved in Merino ewes by a transcervical insemination technique (Guelph system for transcervical artificial insemination; GST-AI). Cervical penetration rate is an important limitation to the use of such methods in Merinos. Simulated insemination was performed to estimate the proportion of ewes in which a pipette could be passed through the cervix to the uterus. In Experiment 1, cervical penetration rate (n = 14 to 30)was unaffected by an increase in postpartum interval at AI from 12 to 26 wk. The results of cervical penetration for individual ewes were found to be repeatable (P < 0.05). Experiment 2 (197 ewes) revealed a clear effect of ewe parity on penetration rates in hormonally synchronized ewes during the nonbreeding season (P < 0.05). In Experiment 3, estrus synchronization using progestagen (n = 51) or prostaglandin (n = 50) did not affect penetration rate. The penetration rate was slightly higher in the naturally cycling ewes, but the difference was not significant. Comparison of ewes from Experiments 2 and 3 suggests the possibility of a major effect of stage of the breeding season on the penetration rate (P < 0.05). It is concluded that ewe selection and management techniques may be used to increase the proportion of transcervical insemination attempts resulting in uterine insemination. However, fertility testing will be required to determine whether such improvements translate into correspondingly increased pregnancy rates.

Follicular development in long-term anoestrous suckler beef cows fed two levels of energy postpartum

Follicular growth patterns were monitored daily by ultrasonography, from calving until completion of the first ovarian cycle postpartum in beef cows fed either a low (L; n = 11) or high (H; n = 12) energy diet. Mean cow body condition score at calving was 2.1 (range 1.75–2.25). The mean (± standard error of the mean) number of days postpartum to detection of the first follicle wave was 10.4±0.9 and 9.6±0.9 days for the L and H groups respectively ( P>0.10). L diet cows tended to have more ( P=0.09) medium-dominant follicle waves before first ovulation than H diet cows. Because the first two follicle waves postpartum consisted of the medium follicles, this resulted in a slightly longer ( P>0.10) interval to detection of the first dominant follicle wave in the L cows than in the H cows. The total number of follicle waves before first ovulation was 10.6±1.2 anand 6.8±1.2 ( P<0.05) for L and H cows, respectively. The growth rate, maximum diameter, persistence and regression rate of anovulatory dominant or medium-dominant follicles were not affected by level of diet ( P>0.10) but did change ( P<0.05) as wave number postpartum increased. Peripheral concentrations of oestrogen were low and were not related to follicular growth during the non-ovulatory period. The oestrogen concentrations were significantly higher immediately before first and second ovulations, and paralleled the growth of the first and second ovulatory follicles. The mean interval from calving to first ovulation was longer ( P<0.05) for the L cows (95 ± 12 days) than for H (70 ± 12 days) cows. All of the cows on the L diet (11/11) had a short cycle following first ovulation while 8/12 of the H cows had a short cycle, 3/12 had a normal cycle and 1/12 had a long cycle after first ovulation. In summary, beef suckler cows with a prolonged postpartum interval to first ovulation have an early resumption of the development of dominant follicles whose growth characteristics are largely unaffected by plane of nutrition; these dominant follicles undergo recurrent development and atresia. In conclusion, the problem of prolonged postpartum anoestrus in beef cows is due to failure of ovulation of dominant follicles rather than a lack of development of dominant follicles.

Prostaglandin F2α and naloxone therapy in the anestrous postpartum beef cow

Three experiments were conducted, using multiparous crossbred beef cows, to test the ability of exogenous prostaglandin F2α (PGF) and/or naloxone to reduce the duration of the postpartum interval to estrus and to improve subsequent reproductive performance. In each experiment, postpartum cows were assigned to treatments by calving date. In Experiment 1, cows (n=44) were assigned to 1 of 4 treatment groups: 1) control, 2) PGF on Day 25 post partum, 3) 400 mg naloxone (3 doses) at 12-h intervals on Day 30 post partum, and 4) PGF on Day 25 followed by 3 400-mg doses naloxone at 12-h intervals on Day 30 post partum. In Experiment 2, cows (n=126) were assigned either to 1) control or 2) PGF on Day 30 post partum In Experiment 3, cows (n=67) were again assigned to 1 of 4 treatments 1) control, 2) PGF on Day 30 post partum, 3) PGF on Day 40 post partum, and 4) PGF on Day 30 and 40 post partum. Serum progesterone was used to determine the postpartum interval to estrus in Experiments 1 and 3. In all 3 experiments, serum progesterone was used to determine the proportion of cows that had reestablished estrous cycles at the start of breeding. Pregnancy rate and calving interval were analyzed for all trials. Naloxone had no effect (P > 0.20) on any reproductive variable measured. The postpartum interval to estrus was similar (P > 0.30) for PGF-treated and control cows in Experiments 1 and 3. The proportion of cows cycling at the start of breeding and the calving interval were not affected (P > 0.20) by PGF treatment in any of the experiments. Only the administration of PGF on Day 40 post partum in Experiment 3 improved (P=0.04) the subsequent pregnancy rate. Analysis of data pooled across experiments showed that the pregnancy rate was higher (P=0.03) for cows treated with PGF than for control cows (91.4 and 72.9%, respectively). It was concluded that administration of PGF during the early postpartum period improves subsequent reproductive function in beef cows.

Preweaning growth of Angus- (Bos taurus), Brahman- (Bos indicus), and Tuli- (Sanga) sired calves and reproductive performance of their Brahman dams.

Calves born to Angus (A), Brahman (B), or Tuli (T) bulls and B cows were evaluated to determine sire breed of calf effects on preweaning calf growth and reproductive performance of their dams. Records from 242 cow-calf pairs over 2 yr were used to assess birth weight, calf ADG, weaning weight, gestation length, and postpartum interval to estrus (PPI). The sire breed x sex of calf interaction was important (P < .05) for birth weight, weaning weight, and gestation length. Birth weights of BB males (32.8 +/- .8 kg) were significantly heavier than for AB and TB males (30.1 +/- .9 and 28.6 +/- .7 kg, respectively) and BB females (29.4 +/- .7 kg). As a main effect, sire breed of calf affected (P < .05) calf ADG, weaning weight, gestation length, and PPI. Calf ADG and weaning weights were greater for AB (.90 +/- .01 kg/d; 220.9 +/- 3.5 kg) than for TB (.81 +/- .01 kg/d; 200.4 +/- 3.0 kg) and BB calves (.78 +/- .01 kg/d; 198.8 +/- 3.5 kg). Gestation lengths differed (P < .01) among all calf genotypes (284, 288, and 294 +/- 1 d for AB, TB, and BB, respectively). Postpartum intervals were shorter (P < .05) for cows nursing BB calves (83 +/- 4 d) than for cows nursing AB (95 +/- 5 d) and TB calves (97 +/- 4 d). Tuli-sired F1 calves were inferior to Angus-sired F1 calves and similar to straightbred Brahman calves in preweaning growth. Crossbred calves had shorter gestations but longer postpartum intervals than purebred calves.

黒毛和種双胎妊娠牛における妊娠末期の濃厚飼料給与が発情回帰日数と分娩前後のボディコンディションスコアおよび背脂肪厚に及ぼす影響

黒毛和種双胎妊娠牛における妊娠末期の濃厚飼料給与が発情回帰日数と分娩前後のボディコンディションスコアおよび背脂肪厚に及ぼす影響

Effect of post-partum mating interval of rabbits on progesterone level through pregnancy

Effect of post-partum mating interval of rabbits on progesterone level through pregnancy

Intrauterine transfer of bovine trophoblast vesicles during dioestrus after breeding to increase pregnancy rates in dairy cows

Early embryonic mortality postbreeding is a major contributing factor to impaired reproductive performance in the dairy cow and is a limiting factor in maintaining a compact calving period in the dairy herd. The objectives of these experiments were (1) to measure the effect of intrauterine transfer of bovine trophoblast vesicles (bTV) during dioestrus on luteal function in dairy cows and (2) to identify if there was an effect of postpartum interval in dairy cows on the pregnancy rate response to bTV transfer between 5 and 7 days after artificial insemination (Al). In Experiment 1, 36 dairy cows were allocated for transfer of three bTV ( n = 18) or carrier medium ( n = 18) to the ipsilateral uterine horn on Day 7 of the oestrous cycle. In Experiment 11, 410 cows calved ⩽ 55 days were allocated at random for transfer of three bTV ( n = 205) or carrier vehicle ( n = 205) to the ipsilateral uterine horn on Day 5–7 after AI. In Experiment III, 410 cows calved > 55 days were allocated at random to receive three bTV ( n = 205) or carrier vehicle ( n = 205) as in Experiment II. In Experiment I, the mean interoestrous interval was 21.4 ± 0.63 days for cows receiving bTV and not different ( P > 0.10) from 21.1 ± 0.66 days for controls. Similarly, serum progesterone concentrations during the oestrous cycle were not affected ( P > 0.10) by bTV transfer. In Experiment II, the pregnancy rate for cows receiving bTV was 43.4% (89/205) and was greater ( P < 0.05) than 30.7% (63/205) for controls. In Experiment III, the pregnancy rate for cows receiving bTV was 54.6% (112/205) and was not different ( P > 0.10) than 51.7% (105/205) for controls. In summary, the transfer of bTV to the ipsilateral uterine horn during dioestrus did not extend the interoestrous interval, increased pregnancy rates in cows bred during the early postpartum period, but not in cows bred beyond 55 days postpartum.

Reproductive Endocrinology of Llamas and Alpacas

The physiology of reproduction with emphasis in endocrinology of llamas and alpacas is addressed. Basic concepts of ovarian follicular dynamics, endocrine events associated with induction of ovulation, corpus luteum formation, pregnancy, parturition, postpartum interval, puberty, and sexual behavior on the female are reviewed. Pathologic conditions of the reproductive process are also reviewed.

???Timing of the Postpartum Papanicolaou Smear.???

Objective To study the relation between the timing of the postpartum examination and the postpartum Papanicolaou smear. Methods One hundred eighty-four women in labor at Arlington Community Hospital were randomized to receive their postpartum Papanicolaou smear at 4, 6, or 8 weeks after delivery. Samples from the exocervix and endocervix were obtained and submitted to the pathology department, which was unaware of the study. Results Twenty-three women were lost to follow-up. Among 161 women who had a postpartum examination, 48 (30%) had it at 4 weeks, 61 (38%) at 6 weeks, and 52 (32%) at 8 weeks. The groups were similar with respect to age, ethnicity, gravidity, parity, marital status, number of sexual partners, age at first intercourse, history of cervical infections, previous history of abnormal Papanicolaou smears, and cervical surgery. Among the 139 women who had a normal prenatal smear, 26 (59%) had an abnormal smear at 4 weeks (24 [92%] had inflammation, one [4%] had inflammation with nuclear atypia, and one [4%] had cervical intraepithelial neoplasia [CIN] III), 17 (32%) were abnormal at 6 weeks (15 [88%] had inflammation, one [6%] had inflammation with nuclear atypia, and one [6%] had CIN III), and 12 (28%) were abnormal at 8 weeks (11 [92%] had inflammation and one [8%] had inflammation with nuclear atypia). There were no differences in the distribution of abnormal Papanicolaou smears at the repeat smear done 3 months after the postpartum examination. Conclusion The incidence of abnormal Papanicolaou smears increased as the postpartum interval decreased from 8 to 4 weeks.