Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2alpha in combination with melengestrol acetate

Nonlactating Bos indicus x Bos taurus cows were used in three herds to determine the efficacy of different PGF2alpha treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 microg of GnRH. Cows were fed MGA (0.5 x mg x cow(-1) x d(-1)) on d 1 to 7. On d 7, cows received either a single injection of PGF2alpha (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 microg; n = 297), or half the recommended dose of PGF2alpha (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 microg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment x herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment x herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2alpha treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus x Bos taurus cows.     

The reproductive performance of dairy cows with anovulatory anoestrus that were injected with either gonadotrophin-releasing hormone or oestradiol benzoate as part of a re-treatment process after insemination

This experiment compared the reproductive performance of synchronised anoestrous dairy cows that were treated initially with a combination of progesterone and oestradiol benzoate and then with either gonadotrophin-releasing hormone (GnRH) or oestradiol benzoate to resynchronise returns to service. It was hypothesised that injecting anoestrous dairy cows with GnRH 12-15 days after insemination and coinciding with the time of insertion of a controlled intravaginal progesterone-releasing (CIDR) device would increase conception rates to the preceding 1st insemination compared with oestradiol benzoate treated cows; both GnRH and oestradiol benzoate would resynchronising the returns to service of those cows that did not conceive to the preceding insemination. Groups of cows in 11 herds were presented for a veterinary examination after they had not been seen in oestrus postpartum. Those cows diagnosed with anovulatory anoestrus (n = 1112) by manual rectal palpation and/or ultrasonography were enrolled in the trial. Each enrolled cow was injected with 2 mg oestradiol benzoate i.m. on Day -10, (where Day 0 was the 1st day of the planned insemination) concurrently with vaginal insertion of a CIDR device. The device inserted was withdrawn on Day -2 and then each cow injected i.m. with 1 mg of oestradiol benzoate on Day -1 unless it was in oestrus. Observation for oestrus preceded each insemination. Every cow that had been inseminated on Days -1,0,1 or 2 was presented for treatment for resynchrony on Day 14 (n = 891). They were divided into 2 groups; those with an even number were each injected i.m. with 250 microg of a GnRH agonist (Treatment group n = 477); each of the cows with an odd number injected i.m. with 1 mg of oestradiol benzoate (control group, n = 414). Each GnRH or oestradiol benzoate injection preceded reinsertion of a CIDR device previously inserted from Days -10 to -2. It was withdrawn on Day 22, 24 hours before injecting 1 mg oestradiol benzoate. Cows observed in oestrus were submitted for a 2nd insemination. Every enrolled cow still present in the herd was pregnancy tested by palpation of uterine contents per rectum about 6 weeks later and again at the end of a herd's seasonal breeding programme. The alternative use of GnRH instead of oestradiol benzoate did not affect the percentage of cows conceiving within 3 days of the mating start date (MSD) (35.6 % vs 35.3 %, P = 0.90), resubmission rates for a 2nd insemination among cows not pregnant to the 1st insemination (81.6 % vs 83.5 %, P = 0.41), 6-week pregnancy rate (59.3 % vs 60.6 %, P = 0.65), 21-weekpregnancy rate (86.6 vs 85.0, P = 0.36), mean interval from MSD to conception (32.5 +/- 1.8 days vs 29.9 +/- 1.8 days, P = 0.26) or conception rate of cows reinseminated by Day 28 (43.3 % vs 38.8 %, P = 0.39). When GnRH was compared with oestradiol benzoate, it did not increase conception rates to the 1st service; it was as effective as oestradiol benzoate in synchronising returns to service in previously treated anoestrous cows that did not conceive to the 1st service. Its use affected neither conception rates to the preceding 1st inseminations nor to the following 2nd inseminations.     

Evaluation of a fixed-time artificial insemination protocol for postpartum suckled beef cows

Treatment with melengestrol acetate (MGA), an oral progestin, prior to administration of gonadotropin-releasing hormone (GnRH) and prostaglandin F2alpha (PG) effectively synchronizes estrus and maintains high fertility in postpartum beef cows. The objective of this experiment was to determine whether treatment with MGA prior to a GnRH-PG-GnRH protocol would improve pregnancy rates resulting from fixed-time artificial insemination (AI). Multiparous crossbred beef cows at two University of Missouri-Columbia farms (n = 90 and n = 137) were assigned by age and days postpartum to one of two treatments. Cows were fed carrier (1.8 kg x animal(-1) x d(-1)) with or without MGA (0.278 mg x kg(-1)) for 14 d. All cows were administered GnRH (100 microg; intramuscularly) on d 12 after MGA or carrier withdrawal and 7 d before PG (25 mg; intramuscularly). All cows received a second injection of GnRH and AI 72 h after PG. Mean days postpartum for MGA and control cows at the initiation of treatment were 39.6 and 38.9 d for herd 1; and 51.9 and 50.9 d for herd 2, respectively (P > 0.70 within herds). Blood samples were collected from all cows at 10 and 1 d before the feeding of MGA or carrier began and at the times GnRH and PG were administered. Concentrations of progesterone in serum at the initiation of treatment were elevated (>1 ng/mL) in 0% of MGA and 7% of control cows in herd 1, and 54% of MGA and 49% of control cows in herd 2 (P > 0.05 within herds). Pregnancy rates to fixed-time AI were determined by transrectal ultrasonography 50 d after AI. Pregnancy rates in herd 1 were 58% (26/45) and 51% (23/45) for MGA-treated and control cows, respectively (P = 0.52), and 63% (44/70) and 45% (30/67) for MGA-treated and control cows in herd 2, respectively (P = 0.03). Differences in pregnancy rates to fixed-time AI were significant (P = 0.04) when data from the two herds were combined (with MGA = 70/115 [61%]; control = 53/112 [47%]). There was no difference (P > 0.20) in final pregnancy rates (timed AI plus 45 d exposure to bulls) between treatments, within herds, or when herds were combined. In summary, pregnancy rates resulting from fixed-time AI may be improved with treatment of MGA prior to a GnRH-PG-GnRH protocol.     

Influence of cornual insemination on conception in dairy cattle

The objective of this study was to compare conception to artificial insemination (AI) services in dairy cattle when semen was deposited into the uterine body or into both uterine horns (cornual insemination). Nine herdsman inseminators (HI) in four commercial dairy herds in Washington constituted the experimental units. Herds ranged in size from 393 cows to 964 cows. The duration of the experiment was 12 mo in three herds and 18 mo in the fourth herd. At the beginning of the experiment all inseminators were trained to deposit semen in the body of the uterus. Inseminators were instructed to use this method for 6 mo. Following employment of body deposition, the same inseminators were retrained to deposit one-half of the semen into the right uterine horn and one-half into the left uterine horn. Cornual inseminations were performed for 6 mo. A total of 4,178 services constituted the data set. Milk samples were collected from cows on the day of insemination and later were assayed for progesterone (P4). There was variation (P less than .01) in conception associated with month of insemination and insemination method (P less than .001). The monthly variation was not associated with season of the year. Least squares means for conception when semen was deposited in the uterine body was 44.7%, compared with 64.6% when cornual insemination was employed. The insemination treatment X inseminator interaction was not significant. Results suggest that cornual insemination provides an alternative to deposition of semen in the uterine body.     

Synchronising ovulation in dairy cows with either two treatments of gonadotropin-releasing hormone and one of prostaglandin, or two treatments of prostaglandin

OBJECTIVE: To compare oestrus synchronisation using two treatments of gonadotropin-releasing hormone (GnRH) and one of prostaglandin F2 alpha (PG) with a double prostaglandin synchronisation protocol under southern Australian conditions. DESIGN: A clinical trial. PROCEDURE: Eight hundred and forty, seasonally calving, lactating dairy cows within nine herds in the Tallangatta district of northeast Victoria were randomly allocated to treatment and control groups. The treatment (GnRH) group received gonadotropin-releasing hormone followed by prostaglandin F2 alpha and then a second treatment with gonadotropin-releasing hormone. These cows were inseminated at a fixed time after the second gonadotropin-releasing hormone treatment. Cows in the control (PG) group received two injections of prostaglandin F2 alpha, 14 days apart, and were inseminated according to detected oestrus. RESULTS: The effect of GnRH treatment on first service conception rate (CRS1) and 30 day pregnancy rate (PR30) varied between herd (P < 0.001 and P < 0.02, respectively). A significant difference in CRS1 between treatment (GnRH) and control (PG) groups existed in pooled data from eight of the nine herds (38.1% vs 65.9%, P < 0.001). A significant difference also existed in PR30 between treatment (GnRH) and control (PG) groups in pooled data from eight of the nine herds (64.1% vs 72.4%, P = 0.03). Pregnancy rates after 56 days of mating for both groups were not significantly different (79.8% vs 84.1%, P = 0.13 for treatment (GnRH) and control (PG) groups, respectively). Submission rates (proportion of cows submitted for insemination) for the treatment (GnRH) groups were 100%. There was significant variation in submission rates in the control (PG) groups. CONCLUSION: The GnRH protocol may be of benefit in herds where a poor response to the double prostaglandin program is anticipated. However, in the majority of herds in this trial, the double prostaglandin program achieved better results with fewer inseminations.     

Optimizing breeding decisions for Finnish dairy herds

The purpose of this study was to determine the effect of reproductive performance on profitability and optimal breeding decisions for Finnish dairy herds. We used a dynamic programming model to optimize dairy cow insemination and replacement decisions. This optimization model maximizes the expected net revenues from a given cow and her replacements over a decision horizon. Input values and prices reflecting the situation in 1998 in Finland were used in the study. Reproductive performance was reflected in the model by overall pregnancy rate, which was a function of heat detection and conception rate. Seasonality was included in conception rate. The base run had a pregnancy rate of 0.49 (both heat detection and conception rate of 0.7). Different scenarios were modeled by changing levels of conception rate, heat detection, and seasonality in fertility. Reproductive performance had a considerable impact on profitability of a herd; good heat detection and conception rates provided an opportunity for management control. When heat detection rate decreased from 0.7 to 0.5, and everything else was held constant, net revenues decreased approximately 2.6%. If the conception rate also decreased to 0.5 (resulting in a pregnancy rate of 0.25), net revenues were approximately 5% lower than with a pregnancy rate of 0.49. With lower fertility, replacement percentage was higher and the financial losses were mainly from higher replacement costs. Under Finnish conditions, it is not optimal to start breeding cows calving in spring and early summer immediately after the voluntary waiting period. Instead, it is preferable to allow the calving interval to lengthen for these cows so that their next calving is in the fall. However, cows calving in the fall should be bred immediately after the voluntary waiting period. Across all scenarios, optimal solutions predicted most calvings should occur in fall and the most profitable time to bring a replacement heifer into a herd was in the fall. It was economically justifiable to keep breeding high producing cows longer than low producing cows.     

Culling on low milk yield and its economic consequences for the dairy herd

Voluntary culling on low milk yield and the economic returns for herds with a stable number of milk cows was investigated for spring calving dairy herds in the Republic of Ireland. The analysis was conducted at annual involuntary removal rates: 15, 20 and 25% and replacement costs as percent of beef value 94, 126, 157%. Varying cow replacement rate above involuntary removal rate by voluntary culling increased milk sold per cow in year 16 to a maximum of +5 to +10% after practicing a fixed strategy for 16 years. Greatest absolute and relative gains in yield occur from voluntary culling at the lowest involuntary replacement rate. Voluntary culling up to 3 to 8 percentage units above involuntary cow replacement rate maximizes economic returns per cow in herd when the market price for replacement heifers exceeds 150% of their beef value. Maximum voluntary culling may be practiced for prices near or below beef value.     

Parameters to monitor dairy herd fertility and their relation to financial loss from reproductive failure

Relationships between herd fertility measurements and financial loss from reproductive failure in dairy herds were studied. Financial losses attributable to prolonged calving interval and forced replacement from reproductive failure were considered. Herd fertility parameters were calculated from artificial insemination and calving data (i.e. calving to first service interval, non-return rate 56 days after first service, percentage of correct inseminations carried out in the interval 18–24 days, fertility status, calving interval, an oestrus index and number of insemination per average cow present in the herd.

The herd fertility parameters were moderately-highly related to loss due to suboptimal calving interval (r=0.20−0.79 in absolute values), but only slightly related to losses due to forced replacement (r<0.17 in absolute values).

Repeatabilities, calculated over a 3-year period, were high for the interval to first service, non-return rate and the oestrus index (0.52−0.67) and moderate for percentage correct reinseminations, fertility status, calving interval and loss due to suboptimal calving interval (0.38−0.48). Repeatability of loss due to forced replacement was low (0.20).

In a regression analysis no herd fertility parameter was fitted with respect to loss from forced replacement. Loss due to suboptimal calving interval at herd level was best estimated by the oestrus index (R²=0.63), the addition of the interval to first service to the regression equation explained a further 10% of the variation between herds. It is suggested that the oestrus index and the interval to first service should be presented as management aids to monitor herd fertility.     

Failure of an intramuscular injection of an analogue of gonadotrophin-releasing hormone 11 to 13 days after insemination to increase pregnancy rates in dairy cattle

At 11 to 13 d after insemination, 1028 dairy cows on 19 farms were given an intramuscular injection of 10 micrograms of the GnRH analogue buserelin. Their reproductive performance was compared to 1022 control cows receiving a placebo. The GnRH analogue-treated cows had fewer short interoestrous intervals compared to the control cows, but there were no significant differences in pregnancy rates to either the insemination preceding or following treatment, in calving to conception interval, or to percent pregnant by the end of mating. There were no differences between treatments in herds of high, average or low pregnancy rate, in 2-year-old cows or cows greater than 2-years-old and in cows calved 40 d or less, or greater than 40 d. The use of 10 micrograms of the GnRH analogue, buserelin, 11 to 13 d after insemination, cannot be recommended as a method of improving reproductive performance in dairy herds.     

Comparison of effects of GnRH and prostaglandin in combination, and prostaglandin on conception rates and time to conception in dairy cows

OBJECTIVE: To assess the effectiveness of a gonadotrophin-releasing hormone (GnRH) / prostaglandin program (GnRH-PG-GnRH, Ovsynch) on conception rates and time to conception of lactating dairy cows compared with a PG program (double prostaglandin injection). DESIGN: A randomised multi-centre cohort study was conducted with 778 cows from nine dairy herds. Cows at different stages of lactation were randomly assigned, after matching for days open at the time of treatment, to either the PG or Ovsynch program. PROCEDURE: Cows on the PG program received two intramuscular injections of prostaglandin (2 mL, Prosolvin) 11 days apart. The Ovsynch program consisted of two intramuscular injections of GnRH (1 mL, Fertagyl) 9 days apart, separated by one injection of prostaglandin 40 h before the second GnRH injection. Milk samples were taken at the time of artificial insemination and assayed for progesterone by radioimmunoassay. RESULTS: The Ovsynch program was not significantly different to PG in achieving conception, with overall conception rates of 37.6% and 41.4%, respectively, for each program. There was, however, a significant interaction between the effects of parity and treatment (P = 0.03), because conception rates were higher in older cows (parity 5 or more) on the PG program than for older cows on the Ovsynch program. There was no significant effect of treatment (P > 0.5) on time to conception after treatment, but older cows were slower to conceive (P < 0.0001). Conception rates differed (P < 0.0001) among herds. CONCLUSION: The median days to conception for both groups was 22 and mean days from treatment to conception were 36.3 +/- 3.3 and 31.6 +/- 2.7 for the Ovsynch and PG programs respectively, indicating that reproductive performance of cows was not significantly different with Ovsynch program or PG program. There appears to be a need to evaluate causes of reproductive failure in older cows.     

Prostaglandin responses in dairy herd breeding programmes

A re-evaluation of results from ten trials conducted in commercial dairy herds between 1974 and 1981 in which lactating dairy cows were injected once or twice with either of two forms of prostaglandin F2alpha (PGF) showed that: the variation in the post-injection interval to oestrus was influenced by the stage of the oestrous cycle at which treatment was administered; this variation was sufficient to reduce pregnancy rates to set-time inseminations; an accurate aid for oestrus detection, such as tail painting, should be used routinely with PGF; if PGF-treated cows were detected in oestrus before being inseminated, the pregnancy rates to first insemination were usually 10% higher than in untreated herd mates. The results show that PGF systems in dairy herds should not be used as au alternative to accurate oestrus detection. These systems can be used to condense the breeding programme and increase pregnancy rates to first insemination. The exploitation of this fertility effect justifies the reassessment of PGF usage in New Zealand dairy herds.     

Fertility of dairy cows in Northern Ireland

A comprehensive database was established on the milk production and reproductive performance of dairy cows in 19 selected herds in Northern Ireland, varying in size, management system and genetic merit. Data were obtained for 2471 cows, 1775 of which calved in a second year, and 693 were culled from the herd for specific reasons. The estimated mean rate of heat detection (assessed by the interheat interval during the main breeding season) in all the herds was 71 per cent, with a range from 53 to 92 per cent The average conception rate to first insemination was 37.1 per cent (range 21 to 66 per cent). The average calving interval for the retained cows was 407.2 days (range 359 to 448 days). Twenty-eight per cent of the cows that calved were culled, with infertility being the largest single reason (26.8 per cent of the cows culled). There were major differences in reproductive performance between the herds, but heat detection rate, conception rate and calving interval did not appear to be affeded by a herd's genetic merit. The herds with shorter calving intervals were characterised by better heat detection efficiency (83 v 61 per cent, P<0.01), a shorter interval from calving to first insemination (74 v 97 days; P<0.05), a higher conception rate to first insemination (45 v 34 per cent, P>0.10) and a lower removal rate (23 v 37 per cent, P<0.01). Furthermore, the cows in these herds had lower body condition scores (BCS) in the dry period (3.0 v 3.3; P<0.05) but lost less body condition in early lactation (0.3 v 0.6 BCS units, P<0.05). These results show that dairy herd fertility in Northern Ireland is generally low and similar to that previously reported for England and the USA, but that in some herds changes in herd management practices improved the cows' fertility.     

Reproductive efficiency and calf survival in Ontario beef cow-calf herds: a cross-sectional mail survey.

A survey of the efficiency of production of Ontario beef cow-calf herds was conducted using a stratified systematic random sample of Ontario producers. In general, about 87% of females exposed to breeding produced a live calf and 6% of these died before reaching four weeks of age. The herd to herd variation in these rates was quite large, the coefficient of variation being about 17%. The stillbirth rate was 1.7% and the abortion rate 1.2%. In general, herds in northern Ontario and herds whose owners kept breeding and calving records, had reduced livebirth rates, the latter probably reflecting accuracy of data. Herds with a restricted (less than three months) breeding season had increased livebirth rates. Herds using injectable vitamins ADE, and prophylactic antibiotics, had increased neonatal losses. Herds with a restricted calving season (less than or equal to 3 months) and/or feeding free choice salt to cows had decreased neonatal losses. Herdsize and calf mortality rate were directly related, but this did not appear to be due to increased density of cows at calving time. In herds, where calving occurred during the spring, using scour vaccines in calves was associated with increased calf mortality.     

Bulk milk urea concentrations and their relationship with cow fertility in grazing dairy herds in southern Chile

Milk urea determination is being used as a broad indicator of protein/energy imbalance in dairy herds. The main purpose of this study was to compare blood and bulk milk urea values in grazing herds, to evaluate their seasonal variation under South Chilean conditions, and to examine their potential relationships with herd fertility. The association between herd blood urea concentration (mean of seven lactating cows) and bulk milk urea concentration (tank containing milk from the previous 24 h) was determined in 21 diary herds. Reference values, seasonal and herd variance, and the frequency of herds with values outside a range of 2.5 to 7.3 mmol/l were determined in bulk milk samples obtained monthly for a period of one year from 82 suppliers at two creameries located in southern Chile. Finally, bulk milk urea was measured every two weeks in samples from 24 herds, and the first service conception rate (FSCR) from 2153 dairy cows was determined. Mean bulk urea concentration was highly correlated with mean herd blood urea concentration (r = 0.95; p < 0.01). Mean urea concentration in the bulk milk samples obtained during one year from 82 herds was 4.9 +/- 1.2 mmol/l, with a range of 1.5 to 11.6 mmol/l. The highest values were found during spring and the lowest values during the summer. There was a high seasonal variation (CV = 13-47%) and between-herd variation (CV = 20-31%). Out of a total of 984 samples, 5.4% had urea values > 7.3 mmol/l and 3.8% had values < 2.5 mmol/l. Of the 82 herds, 27% had values outside the reference interval (2.5-7.3 mmol/l) on two or more occasions. FSCR was lower in herds when the bulk milk urea was > 7.3 mmol/l (50.7%) than in cows, where the urea concentration was < 5.0 mmol/l (73.8%) at the time of insemination. The study concluded that bulk milk urea concentrations provided information similar to herd blood urea concentrations in local grazing dairy herds. There was a high frequency of herds with abnormal values, with large variations between herds and between seasons. Increased milk urea concentrations during spring were associated with lower conception rates.     

Effects of gonadotrophin releasing hormone on reproductive performance of dairy cows with retained placenta.

The effects of gonadotrophin releasing hormone (GnRH) on the reproductive performance of dairy cows with retained placenta were studied. Three hundred and seventy-eight cows diagnosed as having retained placenta received intramuscular injections of either 2 mL sterile water or 200 micrograms of GnRH in 2 mL sterile water between day 8 and day 14 postpartum. Rectal palpation was performed at the time of treatment and ten to 20 days after treatment in order to determine the rate of uterine involution. Thereafter, monthly rectal examinations were carried out until insemination. Pregnancy diagnosis was made by rectal palpation at 40 days or more after breeding. Using the entire experimental population, there were no significant differences between GnRH-treated and control cows for the rate of uterine involution, the occurrence of reproductive problems, the interval from parturition to first observed estrus, the interval from parturition to first insemination, the interval from parturition to conception, the number of services per conception, the total number of services per cow regardless of conception and the incidence of culling for infertility. When the data for herds in which breeding began earlier in the postpartum period (herds having a mean less than or equal to 80 days from parturition to first service for retained placenta cows) were considered, the GnRH treatment resulted in a significantly shorter (p less than or equal to 0.01) calving to conception interval as compared to control cows. Also, there was a significant reduction (p less than or equal to 0.05) in the total number of services per cow regardless of conception and a significant reduction in the interval from parturition to first service.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alternative Herdenparameter beim Milchvieh zur Beurteilung des Herdenfruchtbarkeitsmanagements

Inhalt: Anhand der Fruchtbarkeitsdaten von 330 Milchviehbeständen wurden Herdenparameter zur Beurteilung des Fruchtbarkeitsmanagements abgeleitet. Durch Gegenüberstellung dieser Merkmale in verschiedenen Betriebskategorien sollten Aussagen über Verhaltensmuster und Entscheidungskriterien des Managements im Hinblick auf eine Fruchtbarkeitsberatung gemacht werden. Aus jedem der Parameter “Verrögerungszeit” (VZ) und “Besamungsindex” (BSI) wurden Merkmalspaare abgeleitet und direkt sowie über ihre jeweiligen Quotienten berücksichtigt. Zudem wurden Abgänge wegen schlechter Fruchtbarkeit sowie wegen ungenügender Leistung herangerogen. Tiere ohne Konzeptionserfolg, ds. abgegangene Kühe, wiesen eine um 10 Tage höhere VZ auf als Kühe mit anschlieβender Kalbung und wurden 0.13 mal häufiger als diese besamt. Anders als in der Anbindestallhaltung und in kleineren Herden spielte die reitliche Dimension verlängerter Konreptionsperioden (VZ) in Laufstallbeständen und in gröβeren Herden eine geringere Rolle bei der Selektionsentscheidung als die Besamungshäufigkeit. Gleichreitig wurde in groβen gegenüber kleineren Beständen stärker aufgrund ungenügender Leistung als auf mangelhafte Fruchtbarkeit selektiert. In Herden mit hoher Durchschnittsleistung wurden offenbar gröβere Anstrengungen unternommen, die Tiere tragend zu bekommen: sowohl VZ als auch BSI abgegangener Kühe liegen deutlich über den Werten in leistungsschwächeren Beständen. Eine ungenügende Fruchtbarkeit stellt eher ein Problem in leistungsschwächeren Herden dar. Keine gravierenden Verschiebungen in den Merkmalspaaren zu VZ und BSI wurden mit ungünstigerer Vorjahreszwischenkalbezeit festgestellt, Merzungen wegen ungenügender Fruchtbarkeit waren deutlich häufiger als leistungsbedingte Abgänge. Demgegenüber verringerten sich VZ und BSI bei abgegangenen Kühen mit steigendem mittleren Besamungsindex. Von der Erhebung der beschriebenen Parameter wird ein Informationsgewinn für die Beratung in Milchviehherden erwartet. Im Sinne einer effirienten Bestandsanalyse erscheint es notwendig, diese Informationen bereits zum Betriebsbesuch vorliegen zu haben. Contents: Use of alternative herd parameters for appraisal of fertility management in dairy herds Using fertility data of 330 dairy herds herd parameters were formed to appraise fertility management. Comparing these parameters within classes of different farm categories references should be acquired about patterns of behaviour and selection strategies in fertility management. These parameters were checked for their usefulness for consulting services in milk production. From the fertility traits “service period” (first insemination — conception, VZ) and “insemination frequency”(BSI) couples of parameters were derived and were included both, directly and as their ratio. Additionally the parameters “culling for bad fertility” and “culling for insufficient milk performance” were included. The computations led to the following results: VZ occurred to be 10 days higher in culled cows than in those remaining in the herd. Further insemination index of culled cows exceeded that of cows with conception for 0.13. Differently from tied stall barns and herds of small size the temporal aspect of prolonged periods of conception (represented by VZ) was of lower importance in loose house systems and large dairy herds than frequency of insemination. At the same time culling for insufficient milk performance predominated in larger herds whereas bad fertility caused higher culling rates in small herds. Greater efforts to achieve conception were made in herds showing high milk performance: Values for VZ as well as for BSI for culled cows by far exceeded those of lower yielding herds. Bad fertility tended to be a problem especially in lower yielding herds. No evident changes in parameter couples of VZ and BSI were detected when comparing these results between classes of calving intervals of the preceeding year. Culling for bad fertility occurred to be more frequent than selection for insufficient milk performance. On the other hand values of VZ and BSI increased, when arranging herds according to rising insemination index. It is expected that calculating the parameters described above may give a gain in information for the fertility consultation in dairy herds. However, to obtain an efficient herd analysis these information should be prepared already before visiting the farm.     

Management practices used by white-tailed deer farms in Pennsylvania and herd health problems

OBJECTIVE: To determine current management practices used by white-tailed deer farms in Pennsylvania and identify animal health problems that exist in these herds. DESIGN: Cross-sectional study. STUDY POPULATION: Owners and managers of 233 farms in Pennsylvania that raised white-tailed deer. PROCEDURES: A self-administered questionnaire was mailed to participants. RESULTS: Herds ranged in size from 1 to 350 deer. Land holdings ranged from 0.07 to 607 hectares (0.17 to 1,500 acres). Stocking density ranged from 0.1 to 118.6 deer/hectare (0.04 to 48 deer/acre). Most (84%) respondents raised deer for breeding or hunting stock; 13% raised deer exclusively as pets or for hobby purposes, and purpose varied by herd size. Multiple associations were identified between management or disease factors and herd size. The use of vaccines, use of veterinary and diagnostic services, use of pasture, and use of artificial insemination increased as herd size increased. The most common conditions in herds of all sizes were respiratory tract disease, diarrhea, parasitism, and sudden death. The prevalence of respiratory tract disease increased as herd size increased. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that many aspects of herd management for white-tailed deer farms in Pennsylvania were associated with herd size, but that regardless of herd size, many preventive medicine practices were improperly used or underused in many herds.     

Re-insertion of a progesterone-containing intravaginal device to synchronise returns to oestrus in dairy heifers

Recommendations for oestrus synchronisation of dairy heifers using progesterone-containing intravaginal devices suggest re-insertion of used devices 16 days after first insemination for a period of 5 days to allow a second opportunity for artificial insemination. Controlled studies on the effectiveness of re-using intravaginal devices to synchronise returns to oestrus in non-pregnant dairy heifers are lacking. A clinical trial was conducted involving 750 Friesian heifers in 13 herds. After an initial synchronisation programme, the used intravaginal devices were re-inserted 14 or 16 days after first insemination into half of the heifers in each herd for a period of 5 days. After the first synchronisation programme, 47.5% of heifers remained non-pregnant. Re-insertion of used intravaginal devices for 5 days significantly increased the number of non-pregnant heifers detected in oestrus and inseminated by 48 hours after device removal compared to heifers in which devices were not re-inserted (45.2% v. 27.3%, p < 0.05, in herds where intravaginal devices were re-inserted on day 14; 48.8% v. 13.6%, p < 0.05, in herds where intravaginal devices were re-inserted on day 16). Re-insertion at 14 or 16 days after first insemination was equally effective in increasing visible returns to service. However, the number of non-pregnant heifers synchronised for a second round of artificial insemination was less than expected. Conception rate to the re-synchronised oestrus was unaffected by the treatment. It is concluded that the additional procedures of CIDR re-insertion, removal, tailpainting and insemination involved in there-synchrony programme, and the relatively low in-calf rate to the re-synchronised round of insemination, reduced the potential benefits of re-synchronisation.     

Field trial of a planned breeding regimen for dairy cows, using gonadotrophin-releasing hormone and prostagladin F2alpha

A planned breeding regimen, using gondadotrophin-releasing hormone (GnRH), prostaglandin F2alpha, and a second dose of GnRH, followed by a fixed time insemination, was evaluated in comparison with a negative control on eight commercial dairy farms in the south of England. Fertility data were collected from the 220 cows in the planned breeding group and from 220 matched control cows inseminated at observed oestrus. The planned regimen induced visible oestrus in the vast majority of the cows, and serving the cows at this oestrus reduced the calving to conception interval by 15 days, resulting in 12 per cent more cows being pregnant by 125 days after calving, and 6 per cent more by 150 days. The results from the individual farms suggested that more benefit may be derived from using the regimen in herds with only average fertility indices. There was also evidence to suggest that the second GnRH injection was important, even in cows that came on heat and were served before the fixed time insemination.     

Frequency of ovarian follicular cysts, reasons for culling, and fertility in Holstein-Friesian cows given gonadotropin-releasing hormone at two weeks after parturition.

Holstein-Friesian cows (n=204) were given saline solution or 200 microgram of gonadotropin-releasing hormone (GnRH) by intramuscular injection at 8 to 23 days after parturition. Of cows culled, fewer GnRH-treated cows were culled for infertility, compared with number of cows given saline solution (26 vs 57%; P less than 0.05). Frequency of ovarian follicular cysts was reduced from 15.2% in controls to 5.7% for cows given GnRH (P less than 0.01). The interval to 1st insemination, interval to conception, and inseminations per conception did not differ among saline solution or GnRH-treated cows which remained in the herds. These data provide evidence for reduction in infertility and reproductive disorders in early postpartum dairy cows given GnRH as a prophylactic.