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

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

Doppler sonography of uterine blood flow at mid‐oestrus during different degree of clinical endometritis in dairy cows

The present study was aimed at analysing the mid‐oestrous uterine blood flow parameters during varying degree of endometritis in dairy cows. Degree of clinical endometritis was adjudged on the basis of visual examination of uterine discharge collected from cows at mid‐oestrus, that is mild (slightly turbid; n = 13), moderate (turbid with pus flakes; n = 14) and severe (milky; n = 13). Pulsatility and resistance indices (PI and RI), time average mean velocity (TAMEAN), time average maximum velocity (TAMAX), diameter of the artery, volume of blood flow, Doppler pulse duration (DPD) and systolic upstroke/acceleration time (AT) were measured to study the spectral waveforms at mid‐oestrus. Significantly higher (p < .01) PI and RI were found in cows diagnosed with mild degree in comparison with cows diagnosed with moderate and severe degrees of clinical endometritis. There was significantly higher (p < .01) velocity (TAMEAN and TAMAX), volume of blood flow (BFV‐TAMEAN, BFV‐TAMAX) and DPD in both the middle uterine arteries during moderate and severe degrees of clinical endometritis as compared to mild endometritis. However, significantly higher (p < .01) AT was recorded in cows diagnosed with mild degree as compared to moderate and severe degrees of clinical endometritis. Pearson's correlation analysis has shown that RI was positively correlated with PI and AT in all the groups under study (mild degree, r = .72 and .49; moderate degree, r = .54 and .38; severe degree, r = .90 and .42; p < .05). However, there found significantly negative correlation (p < .05) with other parameters in all the cows irrespective of degree of inflammation. Therefore, it may be deducted that assessment of uterine inflammation can be done with a non‐invasive technique known as Doppler sonography which can be useful in adjudging the hemodynamic changes inside uterus and future fertility of dairy cows.     

Effect of subluteal concentrations of progesterone on luteinizing hormone and ovulation in lactating dairy cows

Two experiments were conducted to determine if administration of progesterone within a low, subluteal range (0.1-1.0 ng/mL) blocks the luteinizing hormone (LH) surge (experiments 1 and 2) and ovulation (experiment 2) in lactating dairy cows. In experiment 1, progesterone was administered to cycling, lactating dairy cows during the luteal phase of the estrous cycle using a controlled internal drug release (CIDR) device. CIDRs were pre-incubated in other cows for either 0 (CIDR-0), 14 (CIDR-14) or 28 days (CIDR-28). One group of cows received no CIDRs and served as controls. One day after CIDR insertion, luteolysis was induced by two injections of prostaglandin (PG) F(2alpha) (25 mg) at 12 h intervals. Two days after the first injection, estradiol cypionate (ECP; 3 mg) was injected to induce a LH surge. Concentrations of progesterone after luteolysis were 0.11, 0.45, 0.78 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14, and CIDR-0, respectively. LH surges were detected in 4/4 controls, 4/5 CIDR-28, 2/5 CIDR-14 and 0/5 CIDR-0 cows following ECP. In experiment 2, progesterone was administered to cycling, lactating, Holstein cows during the luteal phase of the estrous cycle as in experiment 1. Luteolysis was induced as in experiment 1. The occurrence of an endogenous LH surge and ovulation were monitored for 7 days. Concentrations of progesterone after luteolysis were 0.13, 0.30, 0.70 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14 and CIDR-0, respectively. LH surges and ovulation were detected in 5/5 controls, 3/7 CIDR-28, 0/5 CIDR-14 and 0/5 CIDR-0 cows. It was concluded that low concentrations of progesterone can reduce the ability of either endogenous or exogenous estradiol to induce a preovulatory surge of LH and ovulation.     

The value of progesterone, oestradiol benzoate and cloprostenol in controlling the timing of oestrus and ovulation in dairy cows and allowing successful fixed-time insemination

The relative merits of three hormone treatments of dairy cows: (1) intravaginally administered progesterone and oestradiol benzoate; (2) intravaginally administered progesterone and injected cloprostenol; and (3) injected cloprostenol; begun 35-75 days after calving and designed to synchronize oestrus and ovulation and allow successful artificial insemination (AI) at fixed times, have been assessed utilizing information from progesterone concentrations in milk. From this it was concluded that 89% of the cows had ovulated one to three times between calving and the beginning of treatment. Treatment (2) was more effective than (1) in synchronizing ovulation. This was due to the fact that when treatments began early in the ovulation cycle, the requirement for a rapidly effective luteolytic agent was provided by cloprostenol but not by oestradiol benzoate. Treatment (2) was also more effective than (3) in synchronizing ovulation. This is interpreted as meaning that progesterone treatment for 12 days had a beneficial effect in restoring normal cyclic ovarian function in the cows after calving. Whilst cloprostenol administered alone did not have this beneficial effect, there is no evidence that it had a detrimental effect. Based on all cows in treatment groups, the proportion that became pregnant to the fixed-time AI was significantly greater after treatment (2) than after (1), but when based on numbers of cows with synchronized ovulation, there were no significant differences among treatments in the proportions becoming pregnant. The progesterone/cloprostenol treatment had a disadvantage in that when begun during the 11-22 day period of the ovulation cycle, so resulting in a long, total period of suppression of ovulation (mean, 32.1 days), fertility to the fixed-time AI was poor despite effective synchronization of ovulation. Ovulation cycles immediately following the failed, fixed-time AI were normal, both in length and in maximum, luteal-phase progesterone concentration and indicated normal corpus luteum function. Thus the infertility could be ascribed neither to poor timing of AI nor to gross degeneration of follicles prior to their synchronized ovulation following the prolonged suppression of ovulation. The 12-day progesterone treatments when given to anovulatory cows gave, within 5.5 h of their beginning, a concentration of progesterone in milk that was not significantly different from the maximum reached. This concentration declined during the 12 days of the treatment but remained above pretreatment level until 5.5 h after treatment withdrawal; the maximum reached was about half that in normal ovulation cycles.(ABSTRACT TRUNCATED AT 400 WORDS)     

The reproductive performance of anoestrous dairy cows following treatment with progesterone and oestradiol prior to the start of mating

Aims: To determine the reproductive performance of cows diagnosed as anoestrus prior to the planned start of mating (PSM) when they were either treated when first diagnosed, or left untreated until 16 days after the PSM.

Methods: A clinical trial was conducted during the 1996/97 and 1997/98 breeding seasons involving 823 anoestrous dairy cows in 14 herds. On Day-8 (PSM = Day 0), cows in one group (Treated) were each treated with an intravaginal device containing 1.9 g of progesterone (CIDR).The CIDR device was removed on Day-2, and on Day-1 each cow was injected intramuscularly with 1 mg oestradiol benzoate. Cows in the second group (Control) remained untreated at the time of first examination. All cows detected in oestrus after the PSM were mated by artificial insemination (AI) or a bull. Sixteen days after the PSM, all cows that had not been mated were presented for veterinary examination, and those which were still classified as anoestrus were treated with the previously described CIDR regimen. Pregnancy status and approximate date of conception were determined by palpation per rectum 10-13 weeks after the PSM or 6 weeks after the end of the mating period.

Results: Treatment of anoestrous cows 8 days before the PSM significantly increased the number of cows detected in oestrus (95.0% vs 63.1%;p < 0.001) and conceiving (59.5% vs 38.8%;p < 0.001) during the first 21 days of mating, and reduced the interval from PSM to conception by 7.5 days (p < 0.001). There was no significant difference between the conception rate of cows mated following the CIDR treatment regimen compared to cows mated at their first spontaneous oestrus after calving (52.4% vs 58.3%; p = 0.143).

Conclusion: Diagnosis and treatment of anoestrous dairy cows prior to the start of mating significantly improves their reproductive performance under the seasonal mating conditions typical of spring-calving New Zealand dairy herds.     

Ovarian and uterine arteries blood flow waveform response in the first two cycles following superstimulation in cows

To investigate the ovarian and uterine blood flow responses, hemodynamic, circulating ovarian hormones and nitric oxide (NO) after end of treatment by Folltropin. Holstein Friesian (12) cows previously synchronized with CIDR underwent Doppler ultrasound after administrating of FSH daily for 4 days in eight injections started on day 10 of the second ovulation (day −5). Oestradiol (E2), progesterone (P4) and nitric oxide (NOMs) were measured. During the follicular phase, follicle area and antrum area of the second cycle reached maximum value on the day of ovulation compared with that in the first cycle, while during the luteal phase, both showed a pattern of increase and decrease. The luteal area and total coloured area increased till day 10 in the first and second cycle. The first cycle ipsilateral ovarian artery (Ov.A) had higher pulsatility (PI) (p = .001), resistance (RI) (p = .001), peak velocity (PSV) (p = .009) and lower end-diastolic velocity (EDV) (p = .003) compared with the second cycle. The increased ipsilateral Ov.A PSV (p = .009) was accompanied by lower EDV. The first cycle ipsilateral middle uterine artery (MUA) had higher PI (p = .001) and RI (p = .001), with lower PSV (p = .001) and EDV (p = .001). It was concluded that blood flow of ovarian and middle uterine arteries changed after the end of superstimulation as the increased ipsilateral Ov. A and MUA PSVs accompanied by lower EDV and both Doppler indices that reflect the amount of ovarian and uterine blood flow waveform.     

Effect of oxytocin infusion on luteal blood flow and progesterone secretion in dairy cattle

The objective of this study was to investigate the effects of oxytocin infusion on corpus luteum (CL) function during early to mid-diestrus by measuring luteal size (LS) and luteal blood flow (LBF) along with plasma levels of progesterone (P4) and prostaglandin metabolites (13,14-dihydro-15-keto-prostaglandin F_2α, PGFM). On day (D) 7 of the estrus cycle (D1 = ovulation), seven cows received 100 IU of oxytocin (OXY) or placebo (PL) following a Latin square design. LS and LBF increased in both groups over time and no differences were observed between the groups. PGFM did not differ either within the groups over time or between the groups at any time point. P4 of the OXY group was higher compared to that of the the PL group 360 min after the infusion (p = 0.01) and tended to be higher at the time points 450 min, 48 h, and 72 h (all p = 0.08). Results from this study support the hypothesis that OXY is not directly involved in the mechanism(s) governing blood flow of the CL and has no remarkable effects either on luteal size or P4 and PGFM plasma levels. Further investigation is needed to elucidate the role of OXY in CL blood flow during early and late luteal phases.     

一氧化氮自由基在奶山羊氟病机理中的作用

以奶山羊为试验动物,按体重灌服氟化钠复制奶山羊氟病模型,通过对一氧化氮自由基代谢的检测,进一步深入地探讨氟病的发生机理.结果表明:氟可促进机体生成一氧化氮自由基,对机体造成一系列损伤,构成了氟损伤机体的病理学基础.     

Effects of induced endometritis on uterine blood flow in cows as evaluated by transrectal Doppler sonography

This study was conducted to evaluate the effects of induced endometritis on uterine blood flow in cows. Transrectal Doppler sonography was performed on uterine arteries of six cyclic cows before and for 4 days after inducing acute endometritis by intrauterine infusion of 720 mg of policresulen, and for 4 days of the following estrous cycle. Time-averaged maximum velocity (TAMV) increased (p < 0.001) and pulsatility index (PI) decreased (p < 0.0001) within 1 h of policresulen administration, and did not change (p > 0.05) in the next 4 days of the same cycle. TAMV and PI values in the subsequent cycle did not differ (p > 0.05) from the values measured before infusion and showed no changes (p > 0.05) within the cycle. Blood flow parameters were not related (p > 0.05) to plasma concentrations of progesterone and estrogen. All cows showed an acute endometritis determined by histopathological findings of biopsy samples taken 1 day after infusion and fibrotic endometrial alterations detected in the subsequent cycle. No relationships were observed between fibrotic changes of the endometrium and uterine blood flow during either cycle. In conclusion, acute inflammation is accompanied by a rise in uterine blood flow, but fibrotic alterations do not seem to be related to Doppler sonographic findings.     

Effect of seasonal thermal stress on oxidative status,immune response and stress hormones of lactating dairy cows

This study aimed to assess the impact of seasonal thermal stress on oxidative stress, immune response, and stress hormones of lactating dairy cows in subtropical regions with different levels of temperature-humidity index (THI). A total of 32 healthy lactating Holstein dairy cows experienced 4 seasons (8 cows/season). The physiological parameters were categorized into low THI (LTHI, THI = 42.97 ± 0.95) in winter, moderate THI (MTHI, THI = 61.84 ± 0.42) in spring and autumn, and high THI period (HTHI, THI = 86.09 ± 0.23) in summer. The blood samples were collected twice in each season to measure oxidative stress, inflammatory and hormonal parameters. Our results showed THI had a positive correlation with the rectal temperature (R² = 0.821, P < 0.001) and respiratory rate (R² = 0.816, P < 0.001). Dry matter intake, milk yield and fat percentage also significantly differed among groups (P < 0.05). Compared with the MTHI group, the LTHI group exhibited a significant increase in malondialdehyde (MDA) level (P < 0.001), and the HTHI group displayed a significant increase in levels of cortisol, interleukin (IL)-10, IL-1β and tumor necrosis factor-α (P < 0.001). Opposite changes in serum endotoxin and immunoglobulin G levels were observed with the increasing THI (P < 0.001). LTHI notably increased the triiodothyronine level, although the thyroxine level was reduced by LTHI and HTHI compared with the MTHI group. In conclusion, LTHI and HTHI conditions may induce different degrees of oxidative stress, inflammation response, and stress hormone imbalances on lactating dairy cows, therefore environmental management is necessary for the health of dairy cows in extreme weather conditions.     

Effects of selenium yeast on rumen fermentation, lactation performance and feed digestibilities in lactating dairy cows

The objective was to evaluate the effects of selenium-yeast (SY) supplementation on rumen fermentation, lactation performance and feed digestibilities in dairy cows. Twenty-eight multiparous (2.5 ± 0.3 parity) Holstein dairy cows, averaging 625 ± 18.2 kg of BW, 63 ± 3.0 days in milk and average daily milk production of 26.2 ± 0.5 kg/cow were used in a replicated 4 × 4 Latin square experiment. Treatments were: control, LSY, MSY and HSY with 0, 150, 300 and 450 mg selenium yeast (Sel-Plex®, 1 g/kg selenium, produced from Saccharomyces cerevisiae CNCM I-3060) per kg of diet dry matter (DM), respectively. Experimental periods were 45 days with 30 days of adaptation and 15 days of sampling. Ruminal pH was lower for MSY than for control and was linearly (P = 0.03) decreased, whereas total VFA concentration was linearly and quadratically (P ≤ 0.01) increased with increasing SY supplementation, with the least for control, followed by LSY and HSY, and the highest for MSY. Ratio of acetate to propionate was lower for LSY, MSY and HSY than for control, and was linearly and quadratically (P ≤ 0.01) decreased as SY supplementation increased due to an increase in molar proportion of propionate. Ruminal ammonia N content was lower (P ≤ 0.01) for MSY and HSY than for control and was linearly decreased (P ≤ 0.01) with increasing SY supplementation. Dry matter intake, proportions and yields of milk fat, protein and lactose were not affected (P > 0.05). Milk yields and 4% FCM were higher (P ≤ 0.05) for LSY and MSY than for HSY and control. Milk selenium content was linearly and quadratically (P ≤ 0.01) increased as increasing SY supplementation, with the least for control, followed by LSY and MSY, and the highest for HSY. Digestibilities of DM, organic matter (OM), crude protein (CP), ether extract (EE), aNDF and ADF in the total tract were higher (P < 0.01) for LSY and MSY than for control and HSY. The results indicate that supplementation of diet with SY improved rumen fermentation, milk yields, milk selenium, and feed digestion. It was suggested that the SY stimulated the digestive microorganisms or enzymes in a dose-dependent manner. In the experimental conditions of this trial, the optimum selenium-yeast dose was about 300 mg per kg diet DM.     

Effect of tannins and saponins in Samanea saman on rumen environment,milk yield and milk composition in lactating dairy cows

The objective of this study was to investigate the effects of tannins and saponins in Samanea saman on rumen fermentation, milk yield and milk composition in lactating dairy cows. Four multiparous early‐lactating dairy cows (Holstein‐Friesian cross‐bred, 75%) with an initial body weight (BW) of 405 ± 40 kg and 36 ± 8 day in milk were randomly assigned to receive dietary treatments according to a 4 × 4 Latin square design. The four dietary treatments were unsupplemented (control), supplemented with rain tree pod (S. saman) meal (RPM) at 60 g/kg, supplemented with palm oil (PO) at 20 g/kg, and supplemented with RPM at 60 g/kg and PO at 20 g/kg (RPO), of total dry matter (DM) intake. Cows were fed with concentrate diets at a ratio of concentrate to milk yield of 1:2, and chopped 30 g/kg of urea‐treated rice straw was fed ad libitum. The RPM contained condensed tannins and crude saponins at 88 and 141 g/kg of DM respectively. It was found that s upplementation with RPM and/or PO to dairy cows diets did not show negative effect on ruminal pH, blood urea nitrogen and milk urea nitrogen concentration (p > 0.05). However, supplementation with RPM resulted in lower ammonia nitrogen (NH₃‐N) concentration (p < 0.05). In addition, propionic acid and milk production increased while acetic acid, acetic to propionic ratio, methane production, methanogens and protozoal population decreased with RPM and/or PO supplementation. Furthermore, addition of PO and RPO in the diets increased milk fat while supplementation of RPM resulted in greater milk protein and Fibrobacter succinogenes numbers (p < 0.05). The population of Ruminococcus flavefaciens and Ruminococcus albus were not affected by any treatments. The findings on the present study showed that supplementation with RPM and RPO to diets of cows improved the rumen environment and increased milk yield, content of milk protein and milk fat.     

Melatonin and CIDR improved the follicular and luteal haemodynamics,uterine and ovarian arteries vascular perfusion,ovarian hormones and nitric oxide in cyclic cows

This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat-stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat-stressed cow's fertility.     

Comparison of the effects of gonadotropin-releasing hormone, human chorionic gonadotropin or progesterone on pregnancy per artificial insemination in repeat-breeder dairy cows

Three different treatments were compared to improve pregnancy per artificial insemination (P/AI) in repeat-breeder (RB) dairy cows. All cows (n = 103) were assigned to one of four groups: (1) gonadotropin-releasing hormone (GnRH); (2) human chorionic gonadotropin (hCG); (3) once-used controlled internal drug release (CIDR) device; and (4) control. All treatments performed 5-6 days after artificial insemination (AI) and milk samples were collected just before treatment for progesterone assays. There were no significant differences in milk fat progesterone concentration among trial groups. Cows were observed for estrus signs thrice daily. Pregnancy per AI on day 45 in hCG and CIDR groups were significantly higher than GnRH and control groups (60.0% and 56.0% vs. 26.9% and 29.6%, respectively), but there were no differences in P/AI between GnRH and control groups. There were also no significant differences between hCG and CIDR groups. Milk fat progesterone concentrations were compared between pregnant and non-pregnant cows in each group and only in the hCG group it was significantly lower in pregnant cows. In conclusion, treating repeat-breeder cows with hCG or once-used CIDR 5-6 days after AI improved P/AI.     

Effect of superovulation on uterine and serum biochemical parameters and its potential association with transferable embryos in Holstein dairy cows

The objective of this study was to determine the effects of superovulation (SOV) on serum and uterine biochemical parameters, uterine bacteriology and cytology and number of transferable embryos (TE). Dairy cows were placed on a Presynch/CIDR Synch protocol. The SOV group was superovulated, induced in estrus, and inseminated, whereas the control group was induced in estrus and inseminated without SOV. Uterine bacteriology and cytology and uterine and serum biochemical parameters were measured at day 7 of the estrous cycle to start the SOV protocol, as well as on the day of embryo recovery (DER). The SOV group produced 7.5 ± 6.7 oocytes/embryos, of which 3.4 ± 4.7 were TE. Serum urea and E2 and uterine Glu, CK, LDH, TP, P4 and PGFM in the control group and serum P4 and PGFM and uterine LDH and PGFM in the SOV group were significantly higher (p < 0.01) at DER than day 7. At DER, uterine urea, LDH, PGFM and TP and serum urea, LDH, PGFM, and P4 concentrations were higher (p < 0.01) in the SOV group than the control. There was no significant variation in uterine bacteriology or cytology. Overall, these results infer that SOV affects both serum profile and uterine secretions, and that these changes may influence the number of TE.     

Effects of GnRH or progesterone treatment on day 5 post-AI on plasma progesterone, luteal blood flow and leucocyte counts during the luteal phase in dairy cows

This study was designed to test the effects of progesterone or GnRH treatment on day 5 post-AI on fertility and luteal function in dairy cows and heifers. Five days after AI, 32 animals were randomly assigned to a control, intravaginal progesterone for 14 days progesterone releasing intravaginal device (PRID) or GnRH treatment group. On days 5, 7, 12, 14, 17 and 19 post-AI, each animal underwent colour Doppler ultrasonography of the corpus luteum and blood samples were collected for cell counts and plasma progesterone determination. Through general linear model repeated measures analysis of variance, significant effects were observed of treatment, parity, inseminating bull, reduced vascularization of the CL and pregnancy on plasma progesterone concentrations, whereas mean plasma progesterone and time luteal phase day, and treatment and plasma progesterone concentration on day 5 post-AI were found to, respectively, affect neutrophil and lymphocyte counts throughout the luteal phase. Moreover, two binary logistic regression analyses were performed. Based on the odds ratio, the likelihood of pregnancy by days 26-32 post-AI was 23.4 times higher in animals with high mean progesterone levels throughout the study period, compared with animals with low mean progesterone. The likelihood of reduced CL vascularization was 14 times higher in animals treated with PRID, compared with control and GnRH-treated animals. In conclusion, our results indicate that treatment on day 5 post-AI with PRID reduced subsequent CL vascularization, whereas GnRH treatment increased plasma progesterone concentrations on day 12 post-AI, although an effect was identified of the inseminating bull on plasma progesterone levels. Pregnant animals showed higher mean plasma progesterone concentrations than in nonpregnant ones and heifers higher than in lactating cows, whereas blood cell counts differed depending on the treatment and on the mean plasma progesterone concentration on day 5 post-AI.     

Effect of thiabendazole treatment on feed intake, digestibility and selected blood values in lactating dairy cows

Observations of feed intake, digestibility, production and selected blood values were made during the winter housing period on 10 lactating dairy cows, naturally infected with gastrointestinal roundworms, which were either left untreated or dosed on two occasions with thiabendazole in-feed. While treatment had no significant effect on appetite or production, there was a 9.8 per cent improvement in cellulose digestibility (P less than 0.05). An increase in circulating cholesterol in treated cows was associated with the improved utilisation of cellulose. It is considered unlikely that thiabendazole's primary anthelmintic activity was responsible for this effect. Treated cattle also exhibited a significant improvement in thyroid function during the course of the study compared with control animals. This might account for the increase in milk production reported in several trials following anthelmintic treatment of dairy cows.     

Effects of topical nitroglycerine patches and ointment on digital venous plasma nitric oxide concentrations and digital blood flow in healthy conscious horses

OBJECTIVE: To measure and compare palmar digital venous plasma nitric oxide (NO) concentrations and digital arterial blood flow after application of topical nitroglycerine (NTG). STUDY DESIGN: Experimental study. ANIMALS: Healthy adult horses (n=8). METHODS: Digital blood flow was measured by an ultrasonic Doppler flow probe surgically implanted around the medial palmar digital artery. Blood was collected from a catheter placed in the medial palmar digital vein for quantification of NO. NTG patches, NTG ointment or control patches were placed over the palmar digital vessels at the level of the fetlock. Two horses had an intra-arterial infusion of an NTG solution into the medial palmar digital artery in a pilot study. RESULTS: Digital arterial blood flow did not change significantly with application of the NTG patches, NTG ointment, or control patches. There were no statistically significant or biologically important changes in digital venous NO concentrations across time or between treated and control horses. In the pilot study, digital arterial blood flow and palmar digital venous NO concentrations increased with intra-arterial infusion of NTG. CONCLUSIONS: In clinically healthy horses, digital arterial blood flow and digital venous plasma NO concentrations did not change significantly with application of the NTG patches/ointment. These treatments are unlikely to have an effect on the digital vasculature of laminitic horses, however, further investigation is warranted. CLINICAL RELEVANCE: Although NTG patches have been used as a method of decreasing vasomotor tone and improving digital blood flow in horses with laminitis, this study provides evidence in healthy conscious horses that this treatment is not effective in altering digital blood flow.     

L-硝基精氨酸对阿尔茨海默症小鼠脑海马nNOS阳性神经元分布、NOS活性及NO含量变化的影响

为了研究D-半乳糖联合铝诱导的小鼠阿尔茨海默症(AD)脑海马一氧化氮合酶(NOS)活性和一氧化氮(NO)含量的变化及L-NNA和盐酸多奈哌齐对其变化的影响,探讨NO在阿尔茨海默症中的作用机制及2种药物对脑神经元的保护作用。选取2月龄健康昆明小鼠160只,体质量(20±2)g,随机分为正常对照组、模型组、盐酸多奈哌齐治疗组及L-NNA治疗组,利用D-半乳糖联合三氯化铝建立小鼠AD模型,应用生化检测技术测定各组脑海马在造模后每周NOS活性及NO含量。结果表明,模型组海马内NOS活性开始呈缓慢升高,从第4周开始呈显著升高,保持较高含量至12w造模结束;两治疗组脑海马NOS活性在各时间点极显著或显著低于模型组(P0.01或P0.05),并且L-NNA在4~8周时降低脑海马NOS活性的程度好于盐酸多奈哌齐治疗组(P0.05);NO含量的变化随着NOS活性的变化而变化;利用SABC免疫组织化学方法检测各组脑海马神经型NOS(nNOS)阳性神经元,发现模型组脑海马nNOS阳性神经元密度降低,细胞着色变淡,胞体截面积和最长突起长度变小,经过治疗后神经元密度增加,胞体截面积和最长突起长度显著改善(P0.05)。结果提示NO参与了AD形成过程,高浓度的NO能发挥神经毒性作用损害脑组织;L-NNA通过抑制NOS的活性,降低了脑海马NO的含量,对阿尔茨海默症中海马神经元具有明显的保护作用。     

Effects of rice conservation methods on lactation,blood metabolites,and rumen fermentation in dairy cows

We investigated the effect of rice grain conservation methods on feed intake, milk production, blood metabolites, and rumen fermentation in dairy cows. Raw rice grain was dried before crushing (DRY), ensiled after crushing (ENS‐A), or ensiled before crushing (ENS‐B). Twelve multiparous Holstein cows were used in a replicated 3 × 3 Latin square design with three dietary treatments comprising ad libitum access to one of three total mixed rations (TMRs; containing DRY, ENS‐A, or ENS‐B at 17% of dietary dry matter) plus a standard allowance of 2.0 kg/day of dairy concentrates. The dietary treatments did not affect the feed intake, milk yield, or milk composition. The selected blood constituents were not influenced by the rice conservation method. The ruminal lactic acid and total volatile fatty acid (VFA) concentrations and the VFA proportion in the cows were not influenced by the rice conservation method. These results demonstrate that the rice grain conservation method has little impact on lactation performance when cows are fed a TMR containing 17% treated rice grain (dry matter basis).