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1.
This study's objective was to determine if nutrient restriction during late gestation affected beef heifer feed intake, body weight (BW) gain and endocrine regulation during a 10‐week feeding trial. During the last 100 days of gestation, control (CON) dams were fed to increase body condition score (BCS). Whereas, nutrient‐restricted dams (NR) and NR dams protein supplemented 3 days/week (NRS) were fed to decrease BCS by 1.2. After parturition, all cow‐calf pairs were moved to a common pasture and fed in excess of requirements until weaning. At 15 months of age, heifers were randomly sorted into two pens and adjusted to a commercial total mixed ration over a 2‐week period. Blood samples and BW were taken at the initiation of feeding and on a biweekly basis for the duration of the feeding trial. Feed intake was monitored for 10 weeks using a GrowSafe System. After 10 weeks, an intravenous glucose tolerance test (IVGTT) was performed on 21 randomly subsampled heifers. During the feeding trial, NR heifers consumed more feed than CON and NRS heifers. Heifers from NR dams tended to increase BW compared to NRS and CON heifers when adjusted for initial BW. Heifers from NR and NRS dams had a greater increase in BCS compared to heifers from CON dams. Plasma glucose and insulin concentrations during the feeding trial increased in NR heifers compared to the other groups beginning at 2 and 4 weeks respectively. Plasma leptin concentrations were increased in the NR and NRS heifers compared to the CON heifers beginning at week 4 of feeding. During the IVGTT at the conclusion of the feeding challenge, plasma glucose and insulin were increased in NR heifers compared to other treatment groups. These results show that nutrient restriction during late gestation alters appetite and endocrine regulation in heifer offspring.  相似文献   

2.
In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F‐F fasted‐fed). One day after the completion of the oestrous induction protocol, group F and F‐F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F‐F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F‐F, while in response to GnRH, LH surge was significantly attenuated in groups F and F‐F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid‐luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving‐induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers.  相似文献   

3.
The objective of this study was to examine the impact of a bovine respiratory disease complex (BRDC) vaccine with a temperature‐sensitive modified live vaccine (MLV) infectious bovine rhinotracheitis (IBR) component on oestrous cycle parameters and the follicular pool. Twenty‐four Holstein heifers (12.4 ± 0.5 months) previously calfhood vaccinated with an IBR MLV component were enrolled in two replicates (Spring; n = 10 and Fall; n = 14) and were blocked by pre‐vaccination bovine viral diarrhoea (BVD) serum neutralizing (SN) titres. Upon enrolment, heifers were oestrous synchronized with sampling beginning at detected oestrus. At their second heat, heifers were vaccinated with a BRDC calfhood vaccine with a MLV (MLV; n = 12) or killed (K; n = 12) IBR component and sampled for two additional cycles. Serum samples for oestrogen (E2) and progesterone (P4) as well as ultrasound data of ovarian structures were collected every other day. Serum samples for anti‐Müllerian hormone (AMH) were collected at oestrus and mid‐cycle for each cycle, and serum for titres was collected prior to and following vaccination. Data were analysed with the PROC MIXED and GLM procedures of SAS. There was no difference in pre‐ or post‐vaccination titres between MLV and K heifers (p > .5). Vaccination had no impact on P4 concentrations, P4 area under the curve, luteal tissue area, peak E2 production or oestrous cycle length (p > .05). Cycle number did impact AMH concentration (p < .05). In MLV heifers, AMH concentration was highest in cycle 1 (p < .05) while cycles 2 and 3 did not differ (p > .05). This was also true for the K heifers in the Fall replicate (p < .05). Within cycle 2, AMH concentrations were numerically lower between vaccine types (K = 308.22 ± 33.3 pg/ml, MLV = 181.13 ± 32.9 pg/ml; p > .05). Although no differences were seen in overall cycle parameters, differences in AMH concentrations may indicate a reduction of the follicular pool following vaccination and requires further investigation.  相似文献   

4.

Background

Declining fertility is a major concern for dairy farmers today. One explanation is shorter and weaker expression of oestrus in dairy cows making it difficult to determine optimal time for artificial insemination (AI). Chemical communication is of interest in the search for tools to detect oestrus or to synchronise or enhance oestrous periods. Pheromones, used in chemical communication within species, can influence reproduction in different ways. The aim here was to investigate whether oestrous cycle length, and duration and intensity of oestrous expression in dairy heifers could be manipulated through exposure to pheromones in oestrual substances from other females.

Methods

Beginning on day 16 of two consecutive control oestrous cycles, ten heifers of the Swedish Red Breed (SRB) were exposed to water. During the two following cycles the heifers were exposed to urine and vaginal mucus, obtained from cows in oestrus. Cyclicity parameters were monitored through hormone measurements, oestrus detection and ultrasonographic examination.

Results

We found no difference in cycle length or in duration of standing oestrus between control and treatment. We did, however, find a tendency of interaction between type of exposure (control or treatment) and cycle number within type of exposure for cycle length (p = 0.068), with the length differing less between the treatment cycles. We also found a tendency of effect of type of exposure on maximal concentration (p = 0.073) and sum of concentrations (p = 0.063) of LH during the LH surge, with values being higher for the control cycles. There were also significant differences in when the different signs of oestrus occurred and in the intensity of oestrous expression. The score for oedema and hyperaemia of external genitalia was significantly higher (p = 0.004) for the control cycles and there was also a significant interaction between type of exposure and time period for restlessness (p = 0.011), with maximum score occurring earlier for treatment cycles.

Conclusions

No evidence of altered oestrous cycle length or duration of oestrus after exposure of females to oestrous substances from other females was found. Expression of oestrus, and maybe also LH secretion, however, seemed influenced by the exposure, with the effect of treatment being suppressive rather than enhancing.  相似文献   

5.
The aim of this study was to evaluate the influence of two different concentrations of plasma progesterone at the time of FSH-P treatment on the superovulatory response in dairy heifers. Sixteen reproductively sound Holstein heifers (13-15 months of age) were used in this study. Superovulatory treatment was commenced at mid-dioestrus (Day 10 ± 2 of the oestrous cycle) of the synchronized (using two injections of PGF2α, 11 days apart) oestrous cycles. Blood samples were collected on the day and the day after commencing FSH-P treatment and at oestrus for plasma progesterone determination. Heifers were grouped based on two levels of plasma progesterone; Group low progesterone (LP; ranging from 2 to 4.5 ng /ml; n = 7) and Group high progesterone (HP; ≥ 4.6 ng /ml; n = 8) at the beginning of FSH-P treatment (one heifer was excluded from the statistical analysis because of the abnormal progesterone level at oestrus). The superovulatory response in terms of mean numbers of palpable corpora lutea (ovulation rate) was significantly higher (p < 0.05) in group LP than group HP. Ovulation rate was negatively correlated (r = -0.51) with the progesterone concentration at the time of commencing FSH-P treatment (p < 0.05). Data suggest that varying concentrations of plasma progesterone at the time of FSH-P treatment may have a different effect on the outcome of superovulatory response in dairy heifers.  相似文献   

6.
The aims of the current study were to illustrate figures for the characteristics of oestrous cycles especially on follicular dynamics, corpus luteum and changes in progesterone and prostaglandin F2alpha, in the Holstein cross-bred dairy heifers. Twenty six healthy and sexual-mature virgin heifers were monitored for signs of oestrus. Their ovaries were sonically examined and the numbers and the sizes of the follicles as well as of the corpus luteum were documented. In our study, no difference in ratio of the 2-wave and 3-wave patterned cycle was evident. Seasons' change did not affect on characteristics oestrous cycles as well as on dynamics of follicles and corpus luteum. The heifers showed high variation in manifesting oestrus especially on a number of hours. The ‘bodily’ oestrous signs lasted longer than did ‘behavioural’ signs and connection of lowering of the back to standing oestrus was established. Certain diversities comparing to of existed dairy breeds were drawn for follicular dynamics, corpus luteum and its progesterone: 1) the 1st an-ovulatory dominant follicles showed higher growth rate and earlier exceeded dominant diameter; 2) the follicle tended to quicker ovulate but with a smaller diameter at ovulation; 3) the corpus luteum exhibited 4−16.5 mm in diameter of central cavity. Connecting to the levels of progesterone, 4) the corpus luteum turned into active, as well as mid-luteal, period quite late, and 5) the duration of the active period of the corpus luteum was shorter, but 6) at the end of the cycle –around the day of oestrus, progesterone remained certain low but significant levels. In conclusion, the Holstein cross-bred dairy heifers in our study faced a problem of delayed post-ovulatory progesterone rise of which underlying causes are needed to be further scrutinised either at endocrine or at cell levels.  相似文献   

7.
With an objective to evaluate the follicular dynamics and vascularity changes in follicles and corpus luteum, the ovaries of cyclic Surti buffaloes (n = 9) were examined daily sequentially by transrectal B‐mode and colour flow mode (CFM) ultrasonography starting from the day of oestrus till the onset of next oestrus. Higher proportion of buffaloes evidenced one‐wave cycle (66.66%) compared to two‐wave cycle (33.34%) with none showing a three‐wave cycle. The dominant follicle of the first follicular wave was the ovulatory follicle and persisted for 19.70 ± 0.50 days compared to its persistence for 16.5 ± 1.45 days in a two‐wave cycle. The maximum diameter of the ovulatory follicle in a one‐wave and two‐wave cycle did not differ yet their linear growth rates were significantly lower (p < 0.01) in a one‐wave cycle. Colour flow mode examination of follicles revealed that the percentage of follicles with detectable blood flow in the subsequently determined largest follicle (dominant follicle) was not different from that in the second largest follicle before follicle deviation. The blood flow in the dominant follicle increased significantly on the day of oestrus. The mean diameter and blood flow to the corpus luteum (CL) increased linearly and significantly from Day 5 of oestrus till Day 13 after which both parameters started declining. At or around Day 16, there was precipitous fall in the blood supply to the CL and CL diameter that continued declining thereafter to reach the lowest around Day 20 of the oestrous cycle. Rise in plasma progesterone concentrations was synchronous to CL diameter and vascularity and showed significant and positive correlations. It was concluded that Surti buffaloes evidence a preponderance of one‐wave follicular growth pattern with a significant increase in the vascularity of ovulatory follicle on the day of oestrus and corpus luteum on Day 13 of the oestrous cycle.  相似文献   

8.
The present study was performed to test fertility in single‐ovulating and superovulated dairy heifers after insemination with low dose sex‐sorted sperm under field conditions. Some parameters, including the dosage, deposition site and timing, were assessed with the pregnancy rates after artificial insemination (AI). Moreover, the use of oestrus synchronization in combination with sorted sperm was evaluated. Besides that, we also improved the embryo production efficiency in superovulated dairy heifers by optimizing the timing of inseminations and repartitioning the sexed sperm dosage among multiple inseminations. The conception rate (52.8%) in heifers after low dose (2 × 106) insemination with sorted sperm deep into the uterine horn did not differ (p > 0.05) from that (59.6%) of conventional AI (1 × 107 non‐sorted sperm) and that of deep insemination with low dose non‐sorted sperm (57.7%). There was also no difference (p > 0.05) between conception rates after single (51.7%) and double (53.8%) deep insemination with sorted semen. Heifers inseminated with sorted sperm at synchronous oestrus had a lower pregnancy rate (48.1%) than heifers at spontaneous oestrus (53.6%), but this did not reach statistical difference (p > 0.05). The average number of transferable embryos collected in vivo from heifers inseminated with sorted sperm (4.81 ± 2.04) did not differ (p > 0.05) from that obtained from heifers after insemination with non‐sorted sperm (5.36 ± 2.74). Thus, we concluded that the pregnancy rate after deep intra‐uterine insemination with low dose sorted sperm was similar to that of non‐sorted sperm, which was either also deposited at a low dose deep intra‐uterine or into the uterine body. Sychronization of oestrus can be beneficial in combination with sorted sperm to optimize the organization and management of dairy herds. The results from superovulated heifers demonstrated that our insemination regime can be used to obtain a comparable embryo production efficiency with sorted sperm than with non‐sorted sperm.  相似文献   

9.
This study aims to characterize the reproductive patterns in Asinina de Miranda jennies during the non‐breeding season. Reproductive activity was surveyed in 12 females, aged between 3 and 18 years old, using ultrasound and teasing with a jack. The animals were monitored from September to April, six in each consecutive year. Of these 12 females, nine showed disruption to the normal pattern of ovarian activity during the non‐breeding season. Loss of normal cyclicity included anoestrus (41.7%), silent ovulatory oestrus (25%), and persistence of corpus luteum (8.3%). Only three females maintained a regular cyclic pattern with oestrous behaviour during the non‐breeding season. Anoestrus began in early November and lasted for an average of 147 ± 28 days (113–191 days), ending near to the spring equinox. Onset of silent oestrous cycles began more erratically, between October and February. In both groups the first behavioural ovulation of the year occurred around the time of the spring equinox. Disrupted reproductive activity was preceded by a shorter oestrous cycle only in females entering anoestrus. The mean follicle size in the first ovulation of the year was larger than in the reproductive season (44.7 ± 2.45 mm vs 39.2 ± 3.60 mm) in anoestrous jennies with protracted oestrus. Though age and body condition score (BCS) were associated, changes in BCS below a threshold of four points (for anoestrus) and five points (for silent oestrus) contributed greatly to disruption of reproductive cycles. BCS in females with regular oestrous cycles during the winter season remained unchanged or exceeded five points prior to the winter solstice.  相似文献   

10.
Accurate detection of oestrus is important for artificial insemination. The aim of this study was to identify oestrous‐specific bovine cervical mucus proteins that could be used to determine the optimal time for artificial insemination. Non‐oestrous and controlled internal drug release (CIDR)‐induced oestrous‐stage mucus proteins were purified and subjected to surface‐enhanced laser desorption/ionization time‐of‐flight mass spectrometry, sodium dodecyl sulphate polyacrylamide gel electrophoresis and MALDI‐TOF/TOF. Among differentially expressed proteins, lactoferrin (LF) and glutamate receptor‐interacting protein 1 (GRIP1) showed a twofold increase during the CIDR‐induced oestrous stage compared to the levels in non‐oestrous stage in bovine cervical mucus. The RT‐PCR, Western blotting and immunohistochemistry results showed that LF and GRIP1 expression was significantly increased during the oestrous stage in the uterus. This study demonstrated that bovine LF and GRIP1 exist during the oestrous stage, but not during the non‐oestrous stage, suggesting that cervical mucus LF and GRIP1 are useful oestrous detection markers in cattle.  相似文献   

11.
Eight heifers, aged 16–17 months and showing normal oestrous cycles, were immunized against a recombinant porcine inhibin α subunit immunogen, together with another 10 heifers of the same age as controls and treated with placebo immunogen. Primary (1 mg immunogen) and two booster (0.5 mg immunogen each) immunizations were administered at 28‐day intervals. Ten days after the second booster immunization, both groups of heifers underwent a superovulation treatment. Each animal was given an intravaginal progesterone releasing sponge, which was withdrawn 7 days following an i.m. injection of 0.5 mg cloprostenol. Heifers were treated with FSH for 4 days and artificially inseminated after oestrus occurred. The embryos were flushed and evaluated 7 days after insemination. Immunization significantly (p < 0.01) increased blood antibody titres against recombinant porcine inhibin α subunit, from pre‐immunizaion and control values of approximately 0.06 of ELISA 450 nm reading to 0.6 to 0.7 after two or three immunizations. The immunized heifers produced on average 15.8 ± 2.8 embryos, significantly (p < 0.05) higher than the yield of 8.3 ± 1.5 in the controls. The number of transferable embryos were non‐significantly higher in immunized than in control heifers (9.6 ± 3.1 vs 5.8 ± 1.6, p > 0.05). The peak plasma oestradiol concentrations were significantly higher in immunized than in control heifers, both immediately after FSH treatment and 20 days thereafter. Plasma P4 concentrations after superovulation were in the range of 20 ng / ml in the immunized heifers, significantly (p < 0.05) higher than the values approximately 15 ng / ml in control heifers. These results indicated that prior immunization against inhibin α subunit stimulated production of antibodies against inhibin, which enhanced follicular developmental response to superovulation and lead to higher yield of total and transferable embryos. Therefore immunization combined with the conventional superovulatory gonadotrophin treatment, can be a simple and efficient method to produce low cost bovine embryos.  相似文献   

12.
OBJECTIVE: To compare the reproductive performance and pattern of onset of oestrus in dairy heifers in which oestrous cycles were synchronised with two doses of prostaglandin (PG) F2alpha and oestrus was synchronised with oestradiol benzoate (ODB). PROCEDURE: Dairy heifers in two herds (herd A, n = 192; herd B, n = 267) were treated with two doses of an analogue of PGF2alpha (cloprostenol, 375 microg, IM) 12 days apart. Heifers not detected in oestrus 48 h after the last dose of PGF2alpha were either left untreated (No ODB, n = 147) or treated with ODB (0.75 mg IM, n = 126). Onset of oestrus was monitored at 0, 24, 48, 80, 96 and 120 h after the last dose of PGF2alpha Heifers were inseminated on detection of oestrus. RESULTS: After the last dose of PGF2alpha, oestrous detection rates at 80 h (43.5 vs 72.6%, P < 0.001), 96 h (74.1 vs 84.9%, P =0.025) and 120 h (78.2 vs 86.3%, P = 0.082) were less in the No ODB compared to the ODB heifers, respectively. Conception rates (percentage pregnant that were inseminated) were greater in the No ODB compared to the ODB heifers (64.3% vs 47.6%, respectively; P = 0.006), while pregnancy rates (percentage pregnant that were treated) were also greater in the No ODB compared to the ODB heifers, but differences were not significant (50.3% vs 41.1%, respectively; P = 0.068). CONCLUSION: Administration of ODB to heifers not in oestrus 48 h after a two-dose PGF2alpha treatment increases the percentage of heifers detected in oestrus by 80 h, 96 h and 120 h after treatment, by an estimated 29%, 11% and 8%, respectively. However, administration of ODB decreases conception rates by an estimated 17%, and may decrease pregnancy rates (estimated 9% difference). Results are consistent with the hypothesis that ODB can increase submission rates but reduce conception rates following a two dose treatment with PGF2alpha.  相似文献   

13.
The primary objective of this study was to determine whether a single measurement of intravaginal electrical resistance (VER), using the commercially available Ovatec® probe, can discriminate between dioestrus and oestrus in Bos indicus females, which had been treated to synchronize oestrus. Santa Gertrudis heifers (n = 226) received one of three oestrous synchronization treatments: double PGF2α 10 days apart, 8‐day controlled internal drug release (CIDR) treatment or CIDR pre‐synchronization + PGF2α 10 days after CIDR removal. The heifers were inseminated within 12 h following observed oestrus, or, if not observed, at a fixed time approximately 80 h, following the last synchronization treatment. They were palpated per rectum for signs of pregnancy 9 weeks after artificial insemination (AI). Vaginal electrical resistance measurements were taken at the completion of synchronization treatments (presumed dioestrus), immediately prior to AI (oestrus), and then at 3 and 9 weeks post‐AI. Mean VER differed between presumed dioestrus and oestrus (113.7 vs 87.4, p < 0.001). The area under the receiver operating characteristics (ROC) curve was 0.925, indicating that VER was highly discriminatory between dioestrus and oestrus. Vaginal electrical resistance at time of AI was negatively associated with odds of conception when all inseminations were included in the analyses [odds ratio (OR) = 0.97; 95% CI 0.95–1.00; p = 0.018], but not when fixed time AIs were excluded (OR = 1.00; 95% CI 0.97–1.03; p = 0.982). Mean VER readings differed between pregnant and non‐pregnant animals at both 3 weeks (120.5 vs 96.7, p < 0.001) and 9 weeks (124.0 vs 100.3, p < 0.001) post‐AI. However, 3‐ and 9‐week VER measurements were not highly discriminatory between pregnancy and non‐pregnancy (area under ROC curve = 0.791 and 0.736, respectively). Mean VER at time of AI for animals diagnosed in oestrus differed between each of the oestrous synchronization treatments (84.7, 73.6 and 78.9, groups 1–3 respectively, p < 0.001). These findings suggest that measurement of VER may improve accuracy of oestrus diagnoses when selecting cattle for AI following oestrous synchronization programmes involving tropically adapted cattle.  相似文献   

14.
Silent oestrus is an unsurmountable problem in the management of buffalo reproduction. In addressing this issue, we have earlier reported variation in the levels of urinary luteinizing hormone (LH) through the different phases of oestrous cycle with an extended window during the mid-oestrous phase. Based on this report, the present study is designed to assess the salivary LH levels in buffalo during the different phases of oestrous cycle. Bovine LH ELISA kit was used to determine the level of salivary LH. We observed a notable variation in salivary LH levels during the different phases of oestrous cycle. The maximum LH level, 39.07 mIU/ml, observed during oestrus, which was significantly (p < .05) higher than other consecutive phases. Altogether, the results showed a significant (p < .05) fold variation during oestrus compared with other phases. Therefore, the study convincingly shows that salivary LH has the potential of application in development of a modality for non-invasive oestrous detection in buffalo.  相似文献   

15.
The objective of the present study was to determine whether oestrous detection with the help of oestrous detection aids during the Heatsynch without timed AI protocol is equally effective with the progesterone‐combined protocol in dairy heifers. A total of 148 heifers were randomly assigned to one of the two groups. A group of heifers treated with Heatsynch with heat detection aids (n = 72) received GnRH on day 0, prostaglandin F2α (PGF2α) on day 7 and oestradiol benzoate (EB) on day 8, while in controlled internal drug release (CIDR)‐Heatsynch group (n = 76), CIDR was included during a period from GnRH to PGF2α. Heifers were checked for oestrus twice daily, i.e. from 09:00 to 10:00 hours and from 15:00 to 16:00 hours starting on day 2 for Heatsynch group and on day 8 in CIDR‐Heatsynch group, and continued up to day 12. KAMAR®heat mount detector (KAMAR® Inc., Steamboat Springs, CO, USA) and ALL‐WEATHER® PAINTSTIK® (LA‐CO Industries Inc., Elk Grove Village, IL, USA) were used as heat detection aids. AI was conducted within 1 h after confirming oestrus in 72 heifers, while 19 animals were transferred with embryo 7 days after oestrus according to the request of the owners. Premature oestrus before PGF2α injection occurred in 18% of Heatsynch group. Of 13 heifers which showed premature oestrus, six were inseminated and two of them conceived. Oestrus detection rate within 12 days after initiation of the protocols did not differ between the two groups (94% vs 95%). There was no difference in the conception rate after first AI (including heifers that were inseminated before PGF2α injection) and embryo transfer between Heatsynch with heat detection aids and CIDR‐Heatsynch groups (36% vs 44% and 70% vs 56%). It is concluded that the use of heat detection aids to monitor the occurrence of premature oestrus prior to PGF2α injection in Heatsynch protocol in dairy heifers was equally effective to the inclusion of CIDR.  相似文献   

16.
The objective of the study was to evaluate the interval from onset of oestrus to time of artificial insemination (AI) to obtain the optimum pregnancy rate with sex-sorted semen in Holstein heifers. Heifers in oestrus were detected and inseminated only by using heat–rumination neck collar comprised electronic identification tag at the age of 13–14 months. Heifers (n = 283) were randomly assigned to one of three groups according to the timing of insemination at 12–16 hr (G1, n = 97), at 16.1–20 hr (G2, n = 94) and at 20.1–24 hr (G3, n = 92) after reaching the activity threshold. The mean duration of oestrus was 18.6 ± 0.1 hr, and mean peak activity was found at 7.5 ± 0.1 hr after activity threshold. The mean interval from activity threshold to ovulation was 29.4 ± 0.4 hr. The overall pregnancy per AI (P/AI) was 53.0% at 29–35 days and 50.9% at 60–66 days after AI. There was a significant reduction between G1 (13.8 ± 1.4 hr) and G3 (7.9 ± 1.4 hr) related to the intervals from AI to ovulation time. Sex-sorted semen resulted in significantly higher P/AI at 29–35 days when heifers inseminated in G3 (60.9%) after oestrus than those inseminated in G1 (49.5%) and G2 (48.9%). In terms of fertility, when the temperature–humidity index (THI) was below the threshold value (THI ≤65) at the time of AI, there was a tendency (≤65; 57.2% vs. > 65; 47.1%) for high pregnancy rate. There was no effect of sire on P/AI. In addition, the interaction of the technician with the time of AI was found significant, and three-way interaction of technician, sire and time of AI was tended to be significant on pregnancy rate. Thus, in addition to delaying the time of insemination (between 20.1 and 24 hr) after oestrous detection, THI and experienced technician were also found to be critical factors in increasing fertility with the use of sex-sorted semen in Holstein heifers.  相似文献   

17.
This study compared artificial insemination pregnancy rate (AI‐PR) between 14‐day CIDR‐GnRH‐PGF2α‐GnRH and CIDR‐PGF2α‐GnRH synchronization protocol with two fixed AI times (56 or 72 hr after PGF2α). On day 0, heifers (n = 1311) from nine locations assigned body condition score (BCS: 1, emaciated; 9, obese), reproductive tract score (RTS: 1, immature, acyclic; 5, mature, cyclic) and temperament score (0, calm; and 1, excited) and fitted with a controlled internal drug release (CIDR, 1.38 g of progesterone) insert for 14 days. Within herd, heifers were randomly assigned either to no‐GnRH group (n = 635) or to GnRH group (n = 676), and heifers in GnRH group received 100 μg of GnRH (gonadorelin hydrochloride, IM) on day 23. All heifers received 25 mg of PGF2α (dinoprost, IM) on day 30 and oestrous detection aids at the same time. Heifers were observed for oestrus thrice daily until AI. Within GnRH groups, heifers were randomly assigned to either AI‐56 or AI‐72 groups. Heifers in AI‐56 group (n = 667) were inseminated at 56 hr (day 32 PM), and heifers in AI‐72 group (n = 644) were inseminated at 72 hr (day 33 AM) after PGF2α administration. All heifers were given 100 μg of GnRH concurrently at the time AI. Controlling for BCS (p < .05), RTS (p < .05), oestrous expression (p < .001), temperament (p < .001) and GnRH treatment by time of insemination (p < .001), the AI‐PR differed between GnRH treatment [GnRH (Yes – 60.9% (412/676) vs. No – 55.1% (350/635); p < .05)] and insemination time [AI‐56 – 54.6% (364/667) vs. AI‐72 – 61.8% (398/644); (p < .01)] groups. The GnRH treatment by AI time interaction influenced AI‐PR (GnRH56 – 61.0% (208/341); GnRH72 – 60.9% (204/335); No‐GnRH56 – 47.9% (156/326); No‐GnRH72 – 62.8% (194/309); p < .001). In conclusion, 14‐day CIDR synchronization protocol for FTAI required inclusion of GnRH on day 23 if inseminations were to be performed at 56 hr after PGF2α in order to achieve greater AI‐PR.  相似文献   

18.
Oestrous signs affect timely mating and reproductive efficiency in swine breeding herds. To study the genetic difference of oestrous signs between Chinese and European pigs, 100 Landrace‐Large White (LLW) cross gilts and 50 Chinese Mi gilts were assessed for oestrous signs and the concentrations of serum estradiol‐17β and progesterone were determined. The genotype of 39 single nucleotide polymorphisms (SNPs) in 11 oestrogen metabolism and function‐related genes was determined by Sequenom iPLEX platform. Compared with LLW gilts, Mi gilts had longer time of standing reflex (p < .001), higher scores of vulva reddening (p = .001) and greater serum estradiol‐17β concentration (p < .01). Gilts with greater serum estradiol‐17β concentrations also had greater (p < .05) scores for oestrous signs. Genetic polymorphisms of nine genes in oestrogen metabolism pathways had significant differences (p < .05) between LLW and Mi gilts. There were three and six haploblocks of SNPs in LLW and Mi, respectively. Compared with LLW, the distribution of haplotypes was more centralized in Mi pigs. Genetic polymorphisms of oestrogen metabolism‐related genes have considerable differences between Chinese Mi and European LLW pigs. Because of the important roles of oestrogen during the oestrus, some genes of oestrogen metabolism pathway could be considered as candidate genes for oestrous signs.  相似文献   

19.
Metabolic adaptation during feed deprivation was determined in five Kamphaengsaen (KPS) and six crossbred Brahman (Crossbred Bra) heifers. All heifers were fed at the rate of 85% of the metabolizable energy requirement for maintenance. At the end of 20 days of restricted feeding, the Crossbred Bra heifers lost more bodyweight than the KPS heifers (12.0 vs. 7.2 kg) (P < 0.05). In both groups of heifers there was a similar depletion of back‐fat thickness, however, the loin eye area of the Crossbred Bra heifers decreased more than KPS heifers (8.43 vs. 0.92%; P < 0.05). Feed restriction elevated the rate of lipolysis in adipose tissue, resulting in increased nonesterified fatty acids concentrations in plasma. The Crossbred Bra heifers had a greater serum high density lipoprotein triacylglycerol concentration than the KPS heifers (17.02 vs. 9.53 mg/dL; P < 0.05). This would suggest that the hepatic tissues in the Crossbred Bra heifers exported more triacylglycerols as very low density lipoprotein than in the KPS heifers. During the feed restriction period, the plasma β‐hydroxybutyrate concentration for the heifers was elevated; however, Crossbred Bra heifers shown less plasma β‐hydroxybutyrate concentration than KPS heifers (242 vs. 326 µmol/L; P < 0.05). This may be due to the difference in very low density lipoprotein secretion between the two groups of heifers. There were significant differences in plasma urea‐nitrogen and plasma glucose concentrations (P < 0.05), with the KPS heifers showing less extensive plasma urea‐nitrogen concentration and hypoglycemia, whereas the Crossbred Bra heifers had more extensive plasma urea‐nitrogen concentration and euglycemia. These two metabolites were suggestive of a ketogenic effect on muscle protein catabolism. In conclusion, it was found that the underfed KPS heifers utilized ketone bodies as their energy source, thus limiting body protein degradation, whereas the Crossbred Bra adapted to feed deprivation by exhibiting an auto‐regulation mechanism for ketogenesis and broke down body protein extensively to satisfy their demand for glucose.  相似文献   

20.
The aim of this study was to develop a resynchronization strategy before the return of oestrus in cows diagnosed as not pregnant after fixed‐time artificial insemination (TAI). A total of 839 cows, approximately 45 days post‐partum, were synchronized using TAI. On day 0, intravaginal progesterone‐releasing devices were inserted and 2 mg of oestradiol benzoate was administered. Eight days later (D8), the progesterone‐releasing devices were removed and oestradiol cypionate (0.5 mg, eCG [300 IU]) and prostaglandin (7.5 mg) were administered. All cows were inseminated between 48 and 56 hr after device removal (D10). Thirty days after TAI, cows that were not diagnosed as pregnant by ultrasound were immediately resynchronized and again inseminated at a fixed time. The hormonal protocol used in the first and second rounds of TAI was the same. The pregnancy rate after the first TAI was 52%, and after the second TAI, it was 49%. The increase in the total pregnancy rate (synchronization + second oestrous synchronization) compared to a single synchronization was 23.5%. In conclusion, resynchronization of oestrus and ovulation in zebu cows that had previously undergone TAI protocols is effective in increasing the reproductive efficiency.  相似文献   

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