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N B Williamson

Publications and source records attributed to N B Williamson.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of a camera - software system and typical farm management for detecting oestrus in dairy cattle at pasture.

AIM: To compare the sensitivity, specificity, predictive values and accuracy of detection of oestrus using a novel oestrus detection strip (ODS) and a camera-software device (CSD) with typical farm management practices of visual observation and use of tail paint in dairy cattle at pasture. METHODS: Dairy cows (n = 480) in a seasonal-calving herd managed at pasture under typical commercial conditions in New Zealand were stratified by age, body condition score and days in milk, then randomly allocated to one of two groups prior to the planned start of mating (PSM). Tail paint was applied to all cows and oestrus detected by visual observation of oestrous behaviour and removal of paint, by farm staff. One group (n = 240) was fitted with ODS and also monitored for signs of oestrus using a CSD, while the Control group (n = 240) was monitored using tail paint and visual observations only. Cows detected in oestrus were artificially inseminated (AI), and pregnancy status determined using rectal palpation and ultrasonography, 51-52 days after the end of a 55-day A period. Results of pregnancy diagnosis were used to confirm the occurrence of oestrus, and the sensitivity, specificity, predictive value and accuracy of detection of oestrus compared between oestrus detection methods. RESULTS: The sensitivity and accuracy of oestrus detection in the Control group, using visual observation and tail paint, were low. Compared with the Control group, detection of oestrus using the ODS and CSD resulted in greater sensitivity (85% vs 78%; p = 0.006), specificity (99.6% vs 98.0%; p < 0.001), positive predictive value (PPV; 88% vs 51%; p < 0.001) and overall accuracy (99.0% vs 98.0%; p < 0.001). Negative predictive value (NPV) did not differ significantly between groups (99.4% vs 99.3%; p = 0.28). Pregnancy rate to first service was higher in the CSD group than in the Control group (72% vs 39%; p < 0.05). Use of the CSD significantly increased the cumulative proportion of cows pregnant to AI over the breeding period (p = 0.044). CONCLUSION AND CLINICAL RELEVANCE: The ODS and CSD was satisfactory for detection of oestrus in seasonal calving dairy herds grazing on pasture and could improve the sensitivity and accuracy of detection of oestrus in herds where these are low.

Animals↗
PubMed2005

Neospora caninum: quantification of DNA in the blood of naturally infected aborted and pregnant cows using real-time PCR.

This study quantified Neospora caninum DNA in the blood and brain of pregnant and aborted heifers by monitoring PCR product formation in real-time using SYBR Green I, a double-stranded DNA-binding dye. Primers were designed to amplify a 188 bp product specific to N. caninum from the Nc-5 gene fragment of N. caninum. Similarly, a 71 bp product was amplified from the 28S rRNA gene of bovine genomic DNA that served as a control. Agarose gel electrophoresis and analysis of the melting curve for PCR products showed that both primer pairs were specific to their targets. Standard curves were generated for both bovine and N. caninum genomic DNA, and were used to compute the relative concentration of parasite to bovine DNA in the test samples. The concentration of N. caninum DNA in 1 ng of bovine genomic DNA obtained from blood ranged between 0.097 ng at the 1st week of the observation and 0 ng at the 15th week in aborted cows. In pregnant cows, the values ranged between 0.080 ng at the 1st week and 0.155 ng at the 15th week of observation. There was a sustained decrease of DNA concentration in the aborted group after abortion and an increase in DNA concentration in the pregnant group. Comparison of parasite DNA in blood and brain of infected heifers showed a higher DNA concentration in brain than in blood. This study shows that N. caninum DNA can be quantified to obtain the relative concentration of parasite DNA to host genomic DNA in blood. This technique allows testing of a large number of samples at one time and can be done without the need for slaughter of tested animals.

Abortion, Veterinary↗
PubMed2005

Associations between pregnancy outcome and serological response to Neospora caninum among a group of dairy heifers.

AIM: To monitor pregnancy in a group of rising 2-year-old dairy heifers on a farm on which abortion due to Neospora caninum was known to occur in previous years. METHODS: A prospective cohort study group of 164 rising 2-year-old heifers was pregnancy-tested and blood-sampled at 4-5-week intervals throughout gestation. Sera were tested for antibodies to N. caninum at 3-4-month intervals, using an enzyme-linked immunosorbent assay (ELISA). When loss of pregnancy was detected, an N. caninum indirect fluorescent antibody test (IFAT) was conducted retrospectively on stored sera collected the month before abortion, the month abortion was detected, and for the following 2 months, from heifers that aborted. All fetal and placental material detected following abortion was subjected to gross post-mortem and histopathological examination. RESULTS: Eleven of 18 (61%) heifers that were seropositive and 4/146 (3%) heifers that were seronegative to N. caninum by ELISA, aborted. The relative risk for abortion among ELISA-positive heifers was 23.6. Abortion occurred predominantly between Days 120 and 152 gestation among the ELISA-positive heifers and throughout gestation among the ELISA-negative heifers. IFAT titres rose around the time of abortion in most of the heifers that were previously seropositive by ELISA, but dropped rapidly again in post-abortion samples. IFAT titres among 4/6 ELISA-positive heifers that did not abort increased, but later in gestation than the time other heifers aborted. IFAT titres remained negative in heifers that aborted that were ELISA negative. CONCLUSIONS: Heifers that were seropositive to N. caninum by ELISA had a much greater risk of abortion than seronegative heifers. Most seropositive heifers showed evidence of a reactivation of infection during pregnancy. High (> or =1:2,000) N. caninum IFAT titres also occurred in non-aborting heifers. CLINICAL RELEVANCE: Culling of replacement heifers seropositive to N. caninum may be a cost-effective strategy for minimising risk of abortion. Pregnancy testing heifers before 5 months gestation may overestimate the number that calve in N. caninum-infected herds, but would assist in documenting the occurrence of abortion. Reliance on a high (>1:2,000) IFAT titre to rule-in N. caninum as a cause of abortion is likely to produce false-positive results.

Abortion, Veterinary↗
PubMed2004

The use of PCR to detect Neospora caninum DNA in the blood of naturally infected cows.

Twelve 2-year old heifers in their fifth month of gestation when pregnancy tested were used in this study. Six heifers aborted at approximately 4 months of gestation and had blood samples drawn less than 6 weeks after the abortions were identified. Blood samples were also drawn from three sero-positive pregnant and three sero-negative pregnant heifers. DNA was isolated from the samples and a 350 bp fragment of the Nc-5 gene was PCR amplified using primer pair Np21+ and Np6+. Also, the Internal Transcribed Spacer 1 (ITS1) was PCR amplified using Tim 3 and Tim 11 primer pair. The Nc-5 gene fragment was cloned, sequenced and the sequence BLAST-tested. Similarly, the ITS1 product was sequenced and BLAST-tested. The BLAST test results revealed that Neospora caninum DNA was present in these blood samples indicating that polymerase chain reaction can be used in the detection of N. caninum DNA in the blood of sero-positive cows.

Abortion, Veterinary↗
PubMed2004

Isolation and molecular characterisation of Neospora caninum in cattle in New Zealand.

AIM: To isolate Neospora caninum from the brains of naturally infected cattle and use molecular techniques to characterise the isolates. METHODS: Neospora caninum tachyzoites were isolated in Vero cell culture from the brains of a cow and two calves. The isolates were characterised using polymerase chain reaction (PCR) methods, DNA sequencing, an immunofluorescent antibody test (IFAT), transmission electron microscopy (TEM), and immunohistochemistry (IHC). The brains of the three cattle were subjected to histopathological examination. A pathogenicity study was conducted in 120 BALB/c mice. RESULTS: Neospora caninum tachyzoites were isolated from all three cases and first observed in vitro between 14 and 17 days post-inoculation. Parasites were sub-cultured and maintained in Vero cell culture for more than 6 months. PCR products were generated for all three isolates, using two different primers. Sequencing of the PCR products and a subsequent BLAST search identified the isolates as N. caninum. In addition, the isolates tested positive using IFAT and IHC, and ultrastructure revealed by TEM was characteristic of N. caninum. Histopathological examination revealed lesions characteristic of N. caninum in 1/3 brains. In the pathogenicity study using BALB/c mice, the mortality rate was 3-7%. CONCLUSION: This was the first successful isolation of N. caninum in New Zealand confirmed using molecular characterisation tests.

Journal Article↗
PubMed2004

Recognition patterns of Neospora caninum tachyzoite antigens by bovine IgG at different IFAT titres.

This study describes qualitative and quantitative antibody response in cows naturally infected with Neospora caninum. The study was carried out with 269 serum samples obtained from 24 cows over a period of 15 weeks. Prior to sample collection, the cows were tested with ELISA. The 269 samples were screened with IFAT and categorized into seven IFAT titre groups (< 1 : 80, 1 : 80, 1 : 200, 1 : 600, 1 : 1000, 1 : 2000, > 1 : 2000). The samples were finally analysed by Western blotting. Seven immunodominant antigens (approximately 18-, approximately 25-, approximately 33-, approximately 35-36-, approximately 45-46-, approximately 47-, approximately 60-62 kDa) and five minor antigens (approximately 25, approximately 51, approximately 64, approximately 77, approximately 116 kDa) were recognized by cow sera. The recognition of approximately 46 kDa antigen by cow sera was common to samples with IFAT titre 1 : 80 and above. Another common antigen was the approximately 18 kDa antigen, which was recognized by samples with IFAT titre 1 : 200 and above. The most remarkable observation was the presence of the 45-46 kDa, the 77 kDa, and absence of the 18 kDa antigenic bands in samples with IFAT titre 1 : 80. This observation was consistent even in the face of fluctuating antibody titre where serum antibody titres from an animal exceeded then failed to reach 1 : 80. Antibody fluctuation was observed across all cows (pregnant and aborted) with no discernible fluctuation pattern. However, the fluctuation in antibody titre observed appeared to be most remarkable in initially ELISA-negative pregnant cows, and to a lesser extent in ELISA-positive pregnant cows, and ELISA-positive aborted cows. Although there was fluctuation in antibody titre, the banding patterns of N. caninum tachyzoite antigens by cows within the same IFAT titre group remained similar.

Abortion, Veterinary↗
PubMed2003

Nutrient balance in the diet of spring calving, pasture-fed dairy cows.

AIMS: To report the nutrient composition of pastures fed to spring-calving dairy cows in the Manawatu region of New Zealand, and describe changes in the nutrient composition of these pastures over a 12-month period. Having done this we sought to: (1) compare the nutrient composition of the pasture offered with the nutrient requirements of spring-calving dairy cows; (2) identify periods when individual nutrient surpluses and deficits are likely; and, (3) identify nutrients that demonstrate a high level of variability between sampling occasions. METHODS: Seven farms took part in the study. Each farm was visited monthly from August 1996 to July 1997. Samples of pasture were taken at each visit and submitted for estimation of dry matter (DM), metabolisable energy (ME), crude protein (CP), non-structural carbohydrate (NSC), neutral detergent fibre (NDF), acid detergent fibre (ADF), calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), chlorine (Cl), sulphur (S), iron (Fe), copper (Cu) and zinc (Zn), and dietary cation-anion differences (DCAD). RESULTS: Sampled pastures were characterised by low to marginal ME, NSC, Ca, Mg, and Zn concentrations when compared with recommended dietary nutrient concentrations for lactating and non-lactating dairy cattle in New Zealand. Analyses revealed relatively high CP, NDF and K concentrations, and DCAD. CONCLUSIONS: These analyses identify broad trends in the nutrient balance of a pasture-only feeding regime and provide a useful reference for planning feed strategies for spring-calving, pasture-fed dairy herds in this region. Recommended changes to on-farm practice should be made after considering the whole farm system, rather than being made solely on the basis of perceived deficiencies or excesses of individual nutrients.

Journal Article↗
PubMed2003

Prevalence of antibodies to Neospora caninum in dogs of rural or urban origin in central New Zealand.

AIM: To investigate the seroprevalence of Neospora caninum infection in populations of dogs from dairy farms, sheep/beef farms and urban areas in the central part of New Zealand. It was postulated seroprevalence would be higher for farm dogs than urban dogs if the life-cycle of this parasite involves transmission between dogs and cattle. METHODS: Serum samples were obtained from dogs that lived on dairy farms (n=161), sheep/beef farms (n=154) and in urban situations (n=150). The relative risk of detecting antibodies to N. caninum using an immunofluorescent antibody test (IFAT) was compared between farm and urban dogs. RESULTS: The relative risk of having a titre of > or = 1:200 to N. caninum was 2.43 (95% CI=1.88-3.14) for dairy-farm dogs and 3.16 (95% CI=2.48-4.02) for sheep/beef-farm dogs, compared with urban dogs. At this titre, which is currently used in New Zealand to indicate seropositivity, seroprevalence of N. caninum infection was 30.7% in urban dogs, 74.5% in dairy-farm dogs and 96.8% in sheep/beef-farm dogs. CONCLUSION: This observation is consistent with a cycling of this disease between cattle and dogs on farms in New Zealand and with higher exposure of dogs to N. caninum on farms than occurs in urban environments. The prevalence of antibodies in all three groups of dogs tested in this study (dairy-farm dogs, sheep/beef-farm dogs and urban dogs) is higher than has generally been reported elsewhere. New Zealand farm dogs have a higher serological prevalence of N. caninum infection than urban dogs. CLINICAL RELEVANCE: Management and disease control practices that break the life-cycle of transmission between cattle and dogs should assist in controlling cattle abortion due to N. caninum.

Journal Article↗
PubMed2002

A longitudinal study of Neospora caninum infection on a dairy farm in New Zealand.

A 600-cow New Zealand dairy herd experienced an abortion storm in 1997 and was monitored (blood sampling at about 3-month intervals) from May 1997 until January 1999. Abortion risk reached 9% in 1997 and was highest in heifers at 19%. The abortion risk decreased in 1998 to 3.2% (still somewhat higher than during the years prior to the outbreak). The serological reaction pattern for Neospora caninum showed an association with abortion risk only around the time of the 1997 outbreak when seropositive cows were 4.2 times more likely to abort than negative ones. Over the whole study period, only 27% of cows that were sampled on all nine visits always tested negative. Offspring from dams which had positive tests for Neospora caninum were 2.4 times more likely to abort than those from dams testing consistently negative. Controlling for age and breed, seropositive cows produced more milk than those that were consistently negative. Infection might have been present endemically within this herd prior to the epidemic, but in 1997 an additional factor appeared to have triggered the outbreak.

Abortion, Veterinary↗
PubMed2002

A serosurvey for antibodies to Leptospira in dogs in the lower North Island of New Zealand.

AIMS: To investigate the prevalence of antibodies to endemic and exotic Leptospira serovars in samples from a serum bank, collected from dogs in the lower North Island of New Zealand. METHODS: Sera (n=466), which had been collected from apparently healthy dogs, were screened using the microscopic agglutination test (MAT) for antibodies to serovars L. borgpeterseni serovar hardjo, L. interrogans serovars pomona, copenhageni and canicola, and L. kirschneri serovar grippotyphosa. RESULTS: Antibody to Leptospiral antigen was found in 14.2% of dogs tested. The highest level of reactivity was with serovar copenhageni, to which 9.5% (41/433) of sera were positive. Antibodies to serovars grippotyphosa and canicola were not detected in this population of dogs. CONCLUSIONS: Leptospira infection is relatively common in dogs in the lower North Island . CLINICAL RELEVANCE: Vaccination of dogs against leptospirosis should be considered using vaccine containing antigen to serovars hardjo, pomona and copenhageni. The presence of moderate levels of copenhageni antibody in dogs in the lower North Island raises the possibility that this serovar has become established in rodent populations in this region.

Journal Article↗
PubMed2001

Recent advances in understanding the epidemiology of Neospora caninum in cattle.

INTRODUCTION: Neospora caninum is the most frequently diagnosed cause of cattle abortion in New Zealand and is an important pathogen worldwide. The parasite has been found in aborted bovine foetuses and in puppies with neurological disease. Recent developments have provided new insights into the epidemiology of the disease that are reviewed in this article. TRANSMISSION: Transplacental infection is of major importance in the spread of N. caninum overseas. Most congenital infections result in the birth of apparently healthy calves. Seroepidemiological studies indicate introduced point-source infections are also likely, as do investigations of abortion outbreaks in cattle herds attributed to N. caninum. Horizontal transmission is an important determinant of the stability of infection prevalence in a herd. Two potential sources of horizontal transmission that have recently been reported are: via a canine definitive host and; cow-to-calf transmission through pooled colostrum or milk. Transmission parameters for the organism have been estimated using mathematical modeling, to explore the epidemiology and options for control of N. caninum infection in dairy cattle in the absence of precise epidemiological data. LIFE-CYCLE: Seroepidemiologic studies, combined with the knowledge that dogs can be a definitive host, provide evidence supporting a dog-cattle life-cycle. The importance of dogs in the epidemiology of bovine neosporosis is not yet clear. It is likely that N. caninum oocysts in dog faeces could serve as a source of infection for cattle and recent studies have shown that the canine and bovine isolatesflare the same organism. Infection of cattle orally exposed to oocysts has been demonstrated experimentally but not in nature. It is not known if other wild carnivores may serve as definitive hosts of N. caninum. CONCLUSION: Despite active research for over a decade, very little is known about the mechanisms of transmission of N. caninum. Vertical transmission is well documented but horizontal spread and the pathogenesis of abortion from this disease need further investigation. It is evident that, even with a very high probability of vertical transmission, some form of horizontal transmission is required for the disease to persist in a herd.

Journal Article↗
PubMed2001

Comparison of oestrus synchronisation programmes in dairy cattle using oestradiol benzoate, short-acting progesterone and cloprostenol, or buserelin and cloprostenol.

AIM: To evaluate the efficacy of a programme using oestradiol benzoate, progesterone and the prostaglandin-F2 (PG) analogue, cloprostenol, to synchronise oestrus and ovulation in dairy cows, compared with a programme using a gonadotropinreleasing hormone (GnRH) agonist, buserelin, and cloprostenol. METHODS: Twenty non-lactating dairy cows, at random stages of the oestrus cycle, were randomly assigned to 1 of 2 treatments. In Treatment 1 ( OPPG; n=10), cows were injected with 2 mg oestradiol benzoate intramuscularly (IM) plus 200 mg progesterone subcutaneously (SC) on Day 0, followed by 500 microg cloprostenol IM on Day 9 and 1 mg oestradiol benzoate on Day 10. In Treatment 2 (GPG; n=10), cows were injected with 10 microg buserelin IM on Day 0, 500 microg cloprostenol IM on Day 7 and 10 microg buserelin on Day 9. The ovaries of all cows were examined by ultrasonography, using an 8 MHz probe, from 5 days before the initial treatment until ovulation. Cows were observed for oestrus 3 times daily for 7 days after cloprostenol treatment. Blood samples were collected daily for determination of progesterone, and 6-hourly for 36 h after the second oestradiol or buserelin injection for the determination of follicle stimulating hormone (FSH) and luteinising hormone (LH) concentrations. RESULTS: The percentage of cows observed in oestrus was higher in the OPPG group than in the GPG group (100% vs 55.6%, p=0.018). Treatment with either short-acting progesterone plus oestradiol benzoate or buserelin was followed by atresia or ovulation of the dominant follicle. Emergence of a new follicular wave occurred earlier (p>0.001) in the GPG group (2.2+/-0.2 days) than in the OPPG group (3.6+/-0.2 days). There was no significant difference between treatment groups in the variation of time of follicular wave emergence or size of the largest follicles at either the time of initial treatment (10.8+/-1.4 mm vs 11.1+/-0.8 mm), cloprostenol treatment (13.8+/-0.7 mm vs 14.0+/-1.3 mm) or of ovulation (15.4+/-0.7 mm vs 17.6+/-1.1 mm; p=0.10). The LH surge occurred sooner after the second injection of buserelin (4.0+/-1.0 h) than after the second injection of oestradiol benzoate (22.8+/-1.2 h; p>0.001). The interval between the second injection of oestradiol benzoate or buserelin and ovulation did not differ significantly between treatment groups (1.7+/-0.3 days vs 1.6+/-0.2 days; p=0.69). CONCLUSIONS: The use of short-term progesterone treatment, combined with oestradiol benzoate for follicular wave synchronisation, and cloprostenol to cause lysis of residual luteal tissue, is a promising alternative to established methods of oestrus synchronisation in cows.

Journal Article↗
PubMed2000

Genomic typing of Streptococcus uberis isolates from cases of mastitis, in New Zealand dairy cows, using pulsed-field gel electrophoresis.

Three hundred and forty-two Streptococcus uberis isolates were cultured from milk samples from subclinical and clinical cases of dairy cattle mastitis. The samples were collected from 15 different New Zealand farming regions, including eight specific farms, during field research trials and veterinary diagnostic investigations. Pulsed-field gel electrophoresis was used to determine and compare the degree of genetic dissimilarity between the restriction endonuclease fragment pattern of the 342 New Zealand and a single United States S. uberis isolate. The 343 isolates exhibited 330 different restriction endonuclease fragment patterns. The United States isolate had a pattern unlike any of the New Zealand isolates. Most of the isolates were genetically different strains (pattern deferred by at least 33%), but identical patterns were noted within the same or different quarters of an individual cow, different cows within the same farm, and from different cows from the same or different districts, farming regions or islands. Seven of the eight selected farms had at most only one pair of isolates with banding patterns, which differed by less than 33%. A high degree of dissimilarity was noted in individual herds in which all the samples were collected on the same day or over a 2-year period. The high degree of dissimilar isolates is an indication that S. uberis infections in New Zealand dairy cattle are largely due to the opportunistic nature of the organism in the cows' environment. Prevention and treatment of S. uberis mastitis will therefore need to be directed at a multitude of different strains present throughout the country as well as in individual herds.

Animals↗
PubMed1999

The effects of calcium supplementation of dairy cattle after calving on milk, milk fat and protein production, and fertility.

AIM: To determine the effect of calcium supplementation of dairy cattle after calving on serum concentrations of calcium, magnesium, and phosphorous after calving, and on reproductive and productive performance in the following lactation. METHODS: This was a double-blind randomised clinical trial using 356 dairy cows of parity 3 or greater from six seasonally calving commercial dairy herds. Cows were randomly assigned to a treatment and control group. The treatment group received two doses of 380 ml of calcium chloride in oil (49 g of elemental calcium); the first dose was given as soon as practical after calving and the second 12 hours later. Control cows received 380 ml of a placebo using the same treatment regime. Treatment and control cows had blood samples taken during the first 7 days after calving to determine serum calcium, magnesium and phosphorous levels. Treatment and control cows were monitored throughout the lactation to measure production and reproductive performance. RESULTS: Treatment had no effect on PSM to first service intervals. Treatment significantly reduced PSM to conception intervals in only one of the four herds with data available for analysis (p = 0.09). There was no difference between treatment groups for adjusted corrected milk yield calculated from the first herd test milk yield (p = 0.93) or 305-day milk solids production (p = 0.19). CONCLUSION: Further studies are required to identify reasons for the between-herd effectiveness of calcium chloride treatment in improving fertility.

Journal Article↗
PubMed1997

Ovulatory responses and plasma luteinizing hormone concentrations in dairy heifers after treatment with exogenous progesterone and estradiol benzoate.

The objectives of this experiment were to determine the effects of 0.5 mg estradiol benzoate, administered intramuscularly 24 h after removal of CIDR-B progesterone containing intravaginal devices, on the time to estrus, ovulation and peak LH concentration in dairy heifers. Ovulatory responses and plasma LH concentrations were examined using 14 Friesian dairy heifers in 2 separate treatment periods. All heifers received a CIDR-B progesterone-containing intravaginal device with an attached 10-mg estradiol benzoate capsule for 12 d. Within each period, 24 h after CIDR-B removal, 7 heifers received an intramuscular injection of 0.5 mg estradiol benzoate while the remaining 7 heifers received an intramuscular injection of a placebo. Blood samples for LH assay were collected at 0, 6 and 12 h, and then every 4 h for 60 h after estradiol injection. Detection of estrus was conducted at 4-h intervals, and ultrasonographical examination to detect ovulation was conducted every 8 h for 88 h after removal of the CIDR-B device. Treatment with estradiol benzoate tended to reduce the time from device removal to the LH peak in Period 1 (median time to LH peak 40.1 vs 63.9 h; P = 6.07). In Period 2, treatment with estradiol had no significant effect on the time to the LH peak, standing estrus or ovulation. We hypothesize that the period effect was due to the stage of cycle at the time of treatment. For heifers treated in Period 1, the stage of cycle was random. However, because of the prior synchronization of estrus, which was implicit in the experimental design, heifers in Period 2 tended to be in late diestrus. The administration of estradiol benzoate after treatment with exogenous progesterone appears to overcome the variability in timing of LH peaks typically occurring in a herd of synchronized heifers due to different stages of follicular development.

Journal Article↗
PubMed1997

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.

Journal Article↗
PubMed1996

The effect of estradiol benzoate administration on estrous response and synchronized pregnancy rate in dairy heifers after treatment with exogenous progesterone.

The objectives of this trial were to determine the effects of 0.5 mg estradiol benzoate administered intramuscularly 24 h after the removal of progesterone-containing intravaginal devices on the occurrence and timing of estrus, synchronized pregnancy rate and synchronized conception rate in dairy heifers. A clinical trial was conducted involving 750 dairy heifers in 13 herds. Within each herd heifers were randomly allocated to 1 of 2 estrus synchronization treatments. All heifers received a CIDR-B progesterone-containing intravaginal device containing a 10 mg estradiol benzoate capsule for 12 d. Twenty-four hours after CIDR-B removal one group received 0.5 mg, im estradiol benzoate while the other group received an intramuscular injection of a placebo. Estrus detection was performed at 48 and 72 h after intravaginal device removal, and heifers detected in estrus at those times were inseminated. Administration of estradiol benzoate 24 h after removal of CIDR-B devices significantly increased the number of heifers exhibiting estrus within the observation period (96.1 vs 90.5%; P < 0.01). It also altered the onset of estrus so that significantly more heifers were in estrus (86.6 vs 72.3%; P < 0.01) and conceived (47.1 vs 37.5%; P < 0.05) by 48 h after CIDR-B device removal. The synchronized conception rate was unaffected by treatment. The distribution of estrus was such that fixed-time insemination after estrus synchronization with this treatment program may be recommended.

Journal Article↗