School of Agriculture, Food and Ecosystem Sciences - Theses

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Start date: 2000 × End date: 2009 × Type: Masters Research thesis × Author: Eagles, Vicki Maree. ×

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    Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows
    Eagles, Vicki Maree. (University of Melbourne, 2000)
    Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.
  • Item
    No Preview Available
    Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows
    Eagles, Vicki Maree. (University of Melbourne, 2000)
    Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.