Reproduction

Comparison of Two Estrus Synchronization Protocols for Fixed-Time Breeding to Increase Pregnancy in Lactating Dairy Cows (2008)

Cow Comfort at Calving (2015)

Click here for this report in pdf format.

Anyone who works in the dairy industry will be aware that there is tremendous variation in maternity pen design. Part of the reason for this variability is a lack of research on what types of environments are best for the cow while she is giving birth. Research at UBC has now recruited the cows’ help in designing more appropriate maternity pens, by conducting a series of ‘preference’ experiments in which we allow the cows to vote with their feet. Below we describe the results of three different preference experiments designed to determine what features are important in the design of maternity pens.

Earlier work on feral and extensively managed cattle tells us about the choices cows make in the natural environment. Cows typically will leave the herd to find a secluded area to give birth; for example, an area of tall grass, or bushes with soft ground cover. From these observations, we hypothesized that indoor-housed cows are motivated to seek seclusion from herd mates (and other perceived threats), and will use a ‘hide’ if given the choice.

To test if cows are motivated to ‘hide’ at calving, we reconfigured our pens at the UBC Dairy Centre in Agassiz, BC. The experimental maternity pens gave cows the choice between an 18 m2 open sawdust bedded pack, and 15 m2 sawdust bedded pack surrounded by 1.5 m high wall that provided a visual barrier between the cow and the rest of the barn (Photo 1). This design was not intended to be practical (we will get to that question later), but to provide a test of the idea that cows want to ‘hide’ around the time of calving.

 barn

Photo 1: The experimental maternity pen that gave cows the option between a hide and open pack.

Cows entered the experimental maternity pen at least 2 days before calving to ensure that they were familiar with both areas. Using video cameras, we recorded where the cows spent their time before and during calving (24 hours per day). Cows calving at night, when the lights in the barn were off and no staff were present, showed no preference between the two packs. However, cows calving during the daytime showed a strong preference for calving inside the hide. Of the 16 cows that gave birth during daylight hours, 13 chose the seclusion of the hide. Cows that calved in the hide started to use it about 8 hours before calving, likely near the start of labour.

Given these promising results, we wanted to test if cows would seclude themselves from herd mates when housed under more practical conditions. We used more conventionally sized individual maternity pens that were directly adjacent to a close-up group pen (this study was in collaboration with researchers at the University of Arhus, and took place in Denmark). To create both a ‘covered’ and ‘uncovered’ side to the maternity pen, we attached a 1.5 m high piece of plywood to half of the front of the pen (facing the close-up group), as well as to both sides (Photo 2). Again we video recorded where cows chose to calve, and again, the preference was clear: of the 19 cows used in this experiment, 15 (79%) calved in the covered side of the pen and only four calved on the uncovered side.

 maternity pen

Photo 2: Individual maternity pen retrofitted with a covered ‘corner’ that gave cows the option to hide. 

The final preference study examined flooring properties that are important to cows at the time of calving. More than a decade of research, much conducted at UBC, has shown that the bedding surface is the most important determinant of cow comfort for lactating cows. Cows strongly prefer dry, deep-bedded surfaces, regardless of the type of bedding used. Dry, deep-bedding is also the most powerful protective design feature in reducing lameness and especially hock lesions on dairy farms. Based on this information, we decided to ask indoor-housed Holstein dairy cows which surface they preferred during calving.

In this experiment, we created a maternity pen with three flooring options: 1) concrete, 2) pebble-top rubber mats, and 3) 10 cm of sand, each covered with a 15 cm layer of straw. We made a large maternity pen that was divided into three sections partitioned with wooden boards; each section had a different flooring surface. Cows were moved into this pen at least 2 d before calving to ensure that they had previous experience with each of the flooring types. After every third cow, the location of each surface was alternated to control for the chance that cows had a preferred side of the pen. Using video cameras, we recorded where cows spent their time the day before calving, and where they chose to calve.

Of the 17 cows in the study, 10 calved on sand, six calved on concrete and one calved on the rubber mats. Cows also generally avoided the rubber mats on the day before calving. These results tell us that rubber mats were the least preferred flooring option for dairy cows when housed in the maternity pen, despite being bedded with a thick layer of straw.

The results of our preference tests indicate that even our modern, indoor housed dairy cows are looking for a secluded place to calve, perhaps especially in busy barns and during busy times of the day. It was also clear that rubber flooring is not preferred by cows at calving. The next steps are to determine if there are other benefits to allowing cows to have a preferred maternity pen, such as reduced calving problems like dystocia or stillbirths. For now, we encourage producers to look with fresh eyes at their maternity housing, keeping cow preferences for seclusion in mind.

We are grateful to Magnus Campler and Katy Proudfoot for their help in preparing this report. For further information please Email marina.vonkeyserlingk@ubc.ca or dan.weary@ubc.ca. This report is based on research published in the Journal of Dairy Science and the Journal of Animal Science. We thank the researchers and staff of the UBC Dairy Education and Research Centre and Aarhus University who collaborated in the work described in this report.  The research by members of UBC’s Animal Welfare Program was funded by NSERC, the Canadian Dairy Commission, Dairy Farmers of Canada and many others listed at http://awp.landfood.ubc.ca/.    

Decreased Fertility with Increasing Parity in Lactating Dairy Cows (2005)

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Anusha Balendran, Jeff Nimmo, Nelson Dinn, and Raja Rajamahendran

Fertility has become a major problem for many dairy producers. Researchers in the UK and USA have reported very low pregnancy rates (PR) in high producing dairy cows. Moreover, high incidences of reproductive abnormalities such as cystic ovarian disease, delayed ovulation, and reduced length and/or intensity of behavioural estrus have been observed in high producing cows.

The PR for heifers bred by AI have not markedly changed during the past 50 years. However, reproductive statistics for heifers have not been published recently and would be a valuable tool for assessing changes in PR associated with parity that occur independent of lactation.

Reduced PR have been associated with low, or abnormal progesterone levels after AI. Progesterone is a hormone necessary for uterine function and embryonic development. It also influences maternal recognition of the embryo. The landmark events in progesterone production after AI include the beginning of the luteal phase with the formation of the corpus luteum (CL) and associated initial rise in progesterone levels. This is followed by either the end of the luteal phase (in the case of an unsuccessful AI) with a decline in progesterone production or prolongation of the luteal phase (if the AI is successful and the embryo is recognized) and continued elevated progesterone levels. A positive relationship between progesterone levels at the beginning of the luteal phase and pregnancy has been observed. Progesterone levels at the end of the luteal phase have also been reported as differing between pregnant and non-pregnant cows. Parity's effect on peripheral progesterone production is as yet unclear.

Therefore, the objectives of this study were to a) compare PR between cows of different parity and heifers and b) describe differences between cow’s and heifer’s progesterone levels as a means of examining reasons for decreased PR with increasing parity.

Beginning in April of 2004, pregnancy rates for 163 Holstein cows and heifers bred at the UBC Dairy Education and Research Centre in Agassiz were recorded. AI services and pregnancy diagnosis results were recorded until at least 30 animals were included in each of four groups; heifers (14 to 16 months), 1st parity, 2nd parity, and 3rd or 4th parity. In addition, the luteal function (progesterone levels) of 10 heifers, and 10 cows in each of three parity groups; 1st parity, 2nd parity and 3rd or 4th parities were assessed. The experimental time period spanned April until mid-September, 2004.

Animals were housed in free stall barns and fed a total mixed ration of corn silage, hay and concentrates. Animals were bred as part of the routine management of the herd, and pregnancy diagnosis was performed around 35 days post AI by ultrasonography. Progesterone levels in blood from heifers and whole milk from cows were measured to assess luteal function among animals.

In total, 11 samples were taken every other day from each animal, from the day of AI (day 0) until 22 days post AI. Blood samples were taken from the tail vein, centrifuged, and the plasma frozen for subsequent progesterone analysis. Milk samples were obtained during milking time in the parlour and frozen for subsequent progesterone analysis.

Pregnancy rate following first insemination was 67.9%, 42.9%, 20.0%, and 11.9% among heifers, and 1st parity, 2nd parity, and 3rd/4th parity cows, respectively (Figure.1). Statistical analysis showed that PR was greater in heifers following first insemination (p

Figure 1. Pregnancy Rates following first insemination. Columns with different superscripts differ significantly (p

Figure 2. Pregnancy Rates Following second insemination. Columns with different superscripts differ significantly (p

Our study clearly demonstrates that parity has a significant effect on PR. Markedly lower PR was observed in animals of higher parity. Progesterone levels were not affected by parity, and therefore are likely not directly involved in the mechanism of parity's influence on PR. Areas that could be further researched to learn why PR is reduced in animals with higher parity are parity’s effect on egg quality and uterine environment.


This research was conducted at the UBC Dairy Education and Research Centre in Agassiz. Anusha Balendran is a graduate student in Animal Science at UBC. Jeff Nimmo was a NSERC undergraduate summer student in Dr. Rajamahendran’s lab. Nelson Dinn is the Manager of the Dairy Centre in Agassiz and, Dr. Raja Rajamahendran is a Professor of Animal Science at UBC.

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Estrus Synchronization and Timed Breeding (Heat Detection Not Required) (2001)

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by: M. Hirad and R. Rajamahendran *

Dairy producers are well aware that reproductive efficiency in their herds has a marked influence on profitability. A calving interval of 12 to 13 months is generally considered to be economically optimal, but often difficult to achieve. Key factors in achieving this goal are the incorporation of efficient and accurate heat detection, proper semen handling and servicing techniques, and timely insemination relative to ovulation of the egg. Estrus (heat) detection has been cited as the most important factor affecting the reproductive success of artificial insemination programs. However, proper control of the time of estrus is difficult, since peak estrus activity often occurs at night, and determination of the actual onset of standing estrus may be difficult without 24 hour observation. In work underway at the UBC Dairy Education & Research Centre at Agassiz, we have demonstrated estrus synchronization and timed breeding as a method that could eliminate the need for estrus detection altogether.

To understand estrus synchronization, we need to review the hormonal control of reproduction. During a normal estrous cycle, gonadotropin releasing hormone (GnRH) is produced by the hypothalamus resulting in the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH). These hormones act to cause the growth and development of follicles, which are structures on the ovary housing the developing eggs. Most of the follicles will regress, but one will become dominant and eventually ovulate. After ovulation, a corpus luteum (CL) is formed in place of the follicle. The CL is responsible for the production of progesterone, which is a hormone necessary to maintain pregnancy. If pregnancy does not occur, another hormone, prostaglandin, is released and acts to regress the CL, thereby initiating another cycle. By understanding these events, it is possible to develop ways to control the estrus phase of the cycle. For instance, various methods to synchronize estrus have been developed. If the approximate time of estrus is known, then estrus detection rates will be higher. Estrus synchronization followed by timed inseminations, can even avoid the need for estrus detection.

We recently compared two such protocols, "Ovsynch" vs "Prostaglandin". Forty-six cows in the "Ovsynch" group were given an injection of GnRH followed by an injection of prostaglandin after 7 days. Kamar heat detectors were placed on the tail-head to aid in estrus detection. Forty-eight hours after prostaglandin, the animals were again treated with GnRH. Timed artificial insemination was done 12 and 36 hours later. Cows in the "Prostaglandin" group (also 46) received two injections of prostaglandin 14 days apart and Kamar heat detectors were put in place at the time of the second injection. Timed AI was done 60 and 84 hours after the second injection.

For both groups, milk samples were obtained on the day of breeding and 7, 14, and 21 days after breeding. The concentration of progesterone in the milk was measured over time using a technique called radioimmunoassay. Progesterone levels, which are low during estrus, can be used to confirm whether the animal was in estrus on the day of breeding. Progesterone levels will rise if ovulation and the formation of the CL occurred but will decrease again if conception did not occur. Pregnancy diagnosis was done on all animals using ultrasound 35 days after insemination.

Our work showed that estrus synchrony was equally good in both groups. In addition, we found that milk progesterone concentrations were a much more reliable indicator of estrus than the Kamar heat detectors. Milk progesterone levels 7, 14, and 21 days after breeding were not different between the two groups, indication that the estrus synchronization method did not affect the function of the CL. Most improtantly, we found that animals in the "Ovsynch" group had a significantly higher pregnancy rate than those in the "Prostaglandin" group (62% vs 40%).

Therefore, although both methods of estrus synchronization resulted in the same degree of synchrony, the "Ovsynch" method resulted in higher pregnancy rates in lactating cows. This method also eliminates the need for estrus detection. It could help to improve reproductive management of dairy cattle and achieve that optimum 12 to 13 month calving interval.

Watch this newsletter for further information about this research and other work from the Animal Reproduction and Reproductive Technologies Program at the UBC Dairy Education & Research Centre, located in Agassiz.

* Dr R. Rajamahendran, Professor in charge of the Animal Reproduction and Reproductive Technologies Program

* M. Hirad, Masters of Science student - thesis research project.

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New Protocols for Fixed - Time Breeding in Dairy Heifers (2003)

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Dairy heifers must be inseminated at 14 to 15 months of age in order to achieve the target age of 24 months at calving. Sure sounds easy, but is this always possible in real life? Dairy producers have many chores involving the milking herd leaving little time for reproductive management of replacement heifers. As a result, timely detection of estrus and insemination do not occur in many heifers. A controlled breeding protocol that allows fixed-time breeding without estrus detection is therefore desirable.

The Ovsynch protocol for synchronizing ovulation is popular and effective for fixed-time breeding programs in dairy cows. In this 10-day protocol, GnRH (gonadotropin releasing hormone) is given on Day 0 (e.g. Monday), followed by Prostaglandin F2a (PGF) a week later on Day 7, (next Monday). A second GnRH is given two days later (on Day 9, Wednesday) and the cows are bred 16 hours later (on Day 10, Thursday). Despite being effective in cows, the average pregnancy rate is only around 40% in heifers, considerably lower than what could be achieved with breeding at detected estrus. In addition, some heifers display estrus during the period of the Ovsynch protocol. Consequently, timed-breeding is often performed after ovulation has occurred, thereby reducing the chances of pregnancy.

A practical method of preventing the early onset of estrus in heifers is to include progesterone in the Ovsynch protocol. An intravaginal progesterone device, known as the Controlled Internal Drug Release device (CIDR, Vetrepharm Inc.), is currently on the market but little information is available on the efficacy of CIDR-based protocols for fixed-time breeding in dairy heifers.

We have recently completed a research project to determine if cheaper or more efficient alternatives to GnRH are available for use in CIDR-based controlled breeding protocols. We compared pregnancy rates in heifers treated with: GnRH (Fertiline, Vetoquinol NA Inc.), porcine luteinizing hormone (pLH; Lutropin-V, Vetrepharm Inc.), estradiol cypionate (ECP, Pharmacia Animal Health), or a GnRH/ECP combination in a CIDR-based Ovsynch protocol.

We used 240 13-14 month old cycling heifers in two research herds, to compare pregnancy rates in the four different CIDR-based fixed-time breeding protocols as described in Table 1. Results are presented in Figure 1.

Table 1. Protocol schedule for the four experimental treatments.

Treatment (no. of heifers) Day of Protocol
0 7 8 9 10
GnRH/GnRH(63) CIDR insertedGnRH, 100mg PGF, 25 mg CIDR removed GnRH, 100mg A.I.
ECP/ECP(56) CIDR inserted ECP, 0.5 mg PGF, 25 mg CIDR removed ECP 0.5 mg None A.I.
GnRH/ECP(60) CIDR insertedGnRH, 100mg PGF, 25 mg CIDR removed ECP 0.5 mg None A.I.
pLH/pLH(61) CIDR insertedpLH,12.5 mg PGF, 25 mg CIDR removed pLH, 12.5 mg A.I.

Though a greater proportion of heifers assigned to the ECP/ECP protocol was determined pregnant, the pregnancy rate did not differ significantly from that of the GnRH/GnRH treated heifers. However, pregnancy rate of heifers in the ECP/ECP group was higher than that in the GnRH/ECP (P=0.05) and pLH/pLH (P=0.02) groups.

Under our experimental conditions, a CIDR-based Ovsynch/fixed-time breeding protocol using ECP at a low dose of 0.5 mg yielded pregnancy rates comparable to those obtained with GnRH, with lower costs and with heifers handled four times instead of five. Though the incorporating of a CIDR device into the Ovsynch protocol looks attractive, it adds significantly to the cost of the protocol. There is a cost advantage to using ECP, but extreme caution must be exercised with this product because in doses higher than the 0.5 to 1.0 mg range, it could lead to excessive (and prolonged) estrogen levels in the blood of heifers. This could impair reproductive function, at least temporarily. This new protocol needs further testing with a larger number of heifers.

Figure 1. Pregnancy rates to fixed-time insemination of dairy heifers after synchronization of ovulation with four different CIDR-based protocols.

This research was conducted simultaneously at the Dairy Research and Technology Centre, Edmonton and at the UBC Dairy Education and Research Centre, Agassiz. Dr. Divakar Ambrose is a Dairy Research Scientist with Alberta Agriculture, Food and Rural Development in Edmonton. Dr. John Kastelic is a Research Scientist at the Lethbridge Research Centre of Agriculture and Agri-Food Canada. Muhammad Aali is a graduate student in Animal Science at UBC, Nelson Dinn is the Manager of the Dairy Centre and Dr. Raja Rajamahendran is a Professor of Animal Science at UBC.

Financial support for this research was provided by Alberta Milk Producers and Alberta Agricultural Research Institute. In kind contributions by Pharmacia Animal Health (Lutalyse, ECP), Vetoquinol NA Inc. (Fertiline) and Vetrepharm Inc. (CIDR, Lutropin-V) are acknowledged.

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Ovulation Synchronization and Fixed-time Artificial Insemination in Dairy Cows (2004)

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Raja Rajamahendran, Jeff Nimmo, Divakar Ambrose, Muhammad Aali, and Nelson Dinn

Improved reproduction in dairy herds has a marked effect on profitability. Many recent studies have shown that, under modern management and housing systems, delay in the onset of postpartum cycling, inaccurate detection of estrus, and early embryonic mortality are the major reproductive problems. It is generally agreed that estrus detection efficiency is around 50% in most dairy herds. Therefore, there is an urgent need to develop and apply new technology that will eliminate the need for estrus detection.

Recent research findings have provided a greater understanding of ovarian follicular and corpus luteum (CL) dynamics, and based on this understanding, new protocols to synchronize ovulation that allow fixed-time artificial insemination without the need for estrus detection have been developed. In the Ovsynch protocol, two injections of gonadotropin releasing hormone (GnRH) are given 9 days apart, with a Prostaglandin F2a (PGF2a) injection given 7 days after the first GnRH treatment. The first GnRH treatment initiates the growth of a new follicular wave, and potentially ovulates a large follicle that is present. The PGF2a injection causes corpus luteum regression, and the second GnRH synchronizes ovulation. Fixed-time artificial insemination is performed about 16 h after the second GnRH injection. Although pregnancy rates after Ovsynch and fixed-time insemination have been shown to be comparable to that after artificial insemination at detected estrus, premature ovulation has been reported to negatively affect pregnancy rates in some trials.

The inclusion of a Controlled Intra-vaginal Drug Release (CIDR) device, releasing Progesterone (P), in Ovsynch-type protocols can prevent premature ovulation. A CIDR-based protocol that allows fixed-time insemination has been successfully used in beef cattle and dairy heifers and approved for commercial use. This protocol consists of initial injections of estrogens (ECP) and progesterone to cause regression of large follicles present and to initiate the growth of a new follicular wave, with concurrent insertion of a CIDR device. Seven days later PGF2a is injected to cause the regression of an existing or induced corpus luteum. The CIDR, which has acted as an artificial corpus luteum, blocking ovulation, is removed after the PGF2a injection. A second estrogen injection is given 2 days after the PGF2a to synchronize ovulation. Fixed-time artificial insemination is performed approximately 28 h after the second injection. See Table 1 for a detailed schedule of the Ovsynch and CIDR-based protocols adopted for the present study.

At the UBC Dairy Education and Research Centre in Agassiz, we used 227 postpartum lactating Holstein cows to compare ovulation synchronization rate, corpus luteum function and pregnancy rates of the two different timed breeding protocols described above. Ovulation was determined to have occurred in cows with milk progesterone levels less than 1ng/ml on day of insemination, and greater than 1ng/ml on Day 7 post insemination. Milk progesterone levels were used to assess response rate to ovulation synchronization protocols and corpus luteum function. Pregnancy rate was determined by ultrasound on Day 35, and then verified by rectal palpation on Day 60. The treatments were initiated regardless of the stage of the oestrous cycles of the experimental animals.

Table 1. Ovulation Synchronization Protocol Schedules

Protocol

Day -10

Day -3

Day -2

Day -1

Day 0

Ovsynch

100 micrograms GnRH injection

25mg PGF2a injection

None

100 micrograms GnRH injection

AI

CIDR

100mg P injection
0.5mg ECP injection
CIDR inserted

25mg PGF2a injection

CIDR removed

0.5mg ECP injection

AI

The results of our study are shown in Figure 1. The data show that ovulation in cows receiving CIDR-based protocol tended to be more synchronized than in cows receiving the Ovsynch protocol. Similarly, the overall pregnancy rate and the pregnancy rate among cows that responded to ovulation synchronization treatment were also greater in the cows receiving the CIDR-based protocol. Among the multiparous cows studied, the pregnancy rates obtained were higher (P

Even though both protocols were effective for ovulation synchronization and fixed-time artificial insemination, the CIDR-based protocol numerically outperformed Ovsynch in this experiment. Both protocols can be initiated regardless of the stage of the oestrous cycle of the animals. Although the overall pregnancy rates of 31% and 41% obtained for Ovsynch and CIDR- based protocols, respectively, were comparable to those seen in lactating cows in many dairy herds today, pregnancy rates were higher (P

This research was conducted at the UBC Dairy Education and Research Centre in Agassiz. Dr. Raja Rajamahendran is a Professor of Animal Science at UBC, and Jeff Nimmo is Dr. Rajamahendran’s undergraduate research assistant. Dr. Divakar Ambrose is a Dairy Research Scientist with Alberta Agriculture, Food and Rural Development in Edmonton. Dr. Muhammad Aali was a graduate student in Animal Science at UBC, and Nelson Dinn is the Manager of the Dairy Centre in Agassiz.

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Preserving Superior Genetics from Culled Cows (2001)

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An inexpensive laboratory technique has been developed at the UBC Dairy Education & Research Centre to produce embryos from eggs obtained from culled cows headed to slaughter. On a typical dairy farm, it is estimated that up to 30% of cows are culled every year and sent to the slaughter house. Although their milk production days are over, culled cows are still potential embryo donors. This is especially significant with cows of superior genetics.

In order to extend the genetics of superior dairy cows beyond the 5 or 6 calves a typical cow will produce in her lifetime, a number of reproduction technologies have been developed to increase the number of calves. The in-vivo embryo production technique has become practically feasible at the farm level. It involves hormone treatment to increase the number of eggs released and artificial insemination, followed by embryo removal and transfer to host recipients. But this technique is expensive and the number of embryos obtained is quite variable.

In the past decade, work in our lab at UBC and elsewhere has perfected an inexpensive technique to produce embryos in the laboratory from eggs obtained from slaughterhouse ovaries. The procedure involves maturation, fertilization and embryo culture in the laboratory. (Figure 1)

An important factor is to determine the optimal time for ovary removal to maximize the number of eggs aspirated for embryo production from culled cows. Eggs grow and develop in fluid-filled structures on the ovary called follicles. During each estrous cycle (21 days), a certain number of follicles are stimulated to grow by follicle stimulating hormone (FSH), which is produced by the pituitary gland in the brain. Normally one of these follicles is selected for ovulation and the rest will regress. By using ultrasound to follow the growth of follicles, we have shown that a higher number of follicles are present in the ovaries approximately 2 days after standing estrus. We have also shown that treatment with additional FSH at estrus can increase the number of follicles in the ovaries.

The present study was designed to investigate the feasibility of producing transferable embryos in the laboratory from ovaries removed from culled cows, before they are sent for slaughter. We also tested the hypothesis that removing ovaries from culled cows 2 days after standing estrus would result in a greater number of eggs being recovered and that treatment with FSH would increase this yield resulting in a greater number of embryos being produced.

Twenty-one cows earmarked for culling by the UBC Dairy Education & Research Centre were randomly assigned to three treatment groups. In Treatment !, seven cows were treated with prostaglandin to induce estrus, and ovaries were removed 2 days after standing estrus. Seven cows in Treatment 2 were treated with prostaglandin and given FSH at standing estrus. The ovaries were removed 2 days later. The seven cows in Treatment 3 were not treated and the ovaries were removed irrespective of the day of the cycle. In all cases, ovaries were surgically removed through the cow's vagina. Within 4 hours of collection, the ovaries were brought to the embryo biotechnology lab at UBC in a thermos flask containing sterile physiological saline at 30-35 degrees Celsius. The eggs were removed from the follicles, graded by quality, and only good quality eggs were used for maturation. After maturing for 24 hours, eggs were transferred to semen droplets for fertilization. Successful fertilization was recorded at 72 hours, and embryo production rates recorded on the 8th day of culture.

Based on this study, using our laboratory technique 6 to 8 transferable embryos can be economically obtained from ovaries removed from culled cows, irrespective of the stage of the cycle. The benefit to the dairy industry is the extending of genetic value to future generations.

* Dr. R. Rajamahendran, Professor in charge of the Animal Reproduction and Reproductive Technologies Program.

* G. Giritharan, Masters of Science student - thesis research project.

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Strategies to Improve Ovulation and Pregnancy in Ovsynch treated Cows and Heifers (2010)

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In response to poor estrus detection and low fertility in lactating dairy cows, reproductive management tools such as estrus synchronization programs are increasingly used on dairy farms. One tool, the Ovsynch timed artificial insemination (AI) protocol offers producers potential freedom from estrus detection difficulties. The Ovsynch protocol involves injecting gonadotropin-releasing hormone (GnRH), followed 7 days later by injecting prostaglandin F2a (PGF2a), and then 48 hours later by a second injection of GnRH. Animals are then inseminated 14 to 16 hours later. The economical benefits of Ovsynch are based on reducing the interval from calving to first AI, reducing the number of days animals are open, and reducing culling of cows because of reproductive problems. While cows treated with Ovsynch have similar pregnancy results to cows bred at natural estrus (~30%), this is still far from satisfactory.

Strategies to Improve Ovulation and Pregnancy in Ovsynch treated Cows and Heifers (entire article in pdf format)

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