The ability to predict peak fertility and optimal mating time of females is an

Transcription

1 The use of Progesterone and Luteinizing Hormone Assays to predict Ovulation and peak fertility timing in small animal breeding management programs. Jennifer Littke Bio 3850 Dr. John Kastelic University of Lethbridge The ability to predict peak fertility and optimal mating time of females is an important part of the efficient management of breeding programs of any kind. This paper will focus on methods used in canine breeding management programs and be specific to predicting ovulation in the bitch. The knowledge of optimal mating time helps a breeder to minimize a common cause of apparent infertility in bitches, inappropriate mating time (1). There are many considerations and methods used to predict time of ovulation in the bitch including assessment of physical and behavioral changes, changes in vaginal epithelium and fluid and the use of hormone assays. The most effective and preferred method of estimating the day of ovulation is the measurement of serum progesterone levels (2). The assay of serum or plasma progesterone every 1-3 days has been proven effective in estimation and confirmation of ovulation in bitches (3). Due to a poor correlation between physical and behavioral changes in estrus and time of ovulation in bitches, daily measurement by quantitative assay beginning in proestrus can detect the initial rise in progesterone allowing accurate determination within ±0.5 to 1.0 days (3). Accurate timing of pre and ovulatory events during breeding management programs is a very useful tool in small animal breeding management especially due to the need of often preplanned matings with studs to accommodate the meeting of the two animals or artificial insemination processes (1). Failure to accurately detect ovulation time resulting in no pregnancy occurring during an ovarian cycle can be costly to a breeding

2 2 management program as canines have a mono-estrus cycle where the inter- estrus interval average about 7 months but can last 13 months or longer in some bitches (1). Figure 1. An diagrammatic outline of canine proestrus and estrus, showing the periods of peak fertility and period of fertilization for natural matings. Depicts synchronization of preovulatory LH surge, ovulation and oocyte maturation (1). The estrus cycle of the bitch has four stages: proestrus, estrus (standing heat), diestrus and anestrus (Figure 1.) (2). Serum progesterone concentration rises in sync with a decrease in proestrus estrogen concentrations and the preovulatory LH peak immediately prior to ovulation (4). The decline in estrogen and subsequent increase in progesterone signals the onset of behavioral estrus, known as standing heat; in the bitch but can happen anywhere from 2-6 days following ovulation (5). This is one of the consequences of relying on behavioural changes in estrus to accurately predict optimal mating time (2). Each bitch is different and no breed ovulates consistently a defined number of days from the onset of proestrus (1). Behavioral and physical changes in the bitch during estrus are largely variable between bitches and breeds which should be

3 3 considered when estimating the ovulation event(6). The specificity of LH and progesterone assay gives a more accurate estimation for each bitch individually increasing the likelihood of a successful pregnancy (1). As stated previously use of a hormone assay is the most accurate measurement of ovulation time in bitches (2). The two most commonly assayed hormones for breeding management programs are LH and progesterone (2). Both hormones can be tested for and measured using commercial in-home assays as well as by veterinary clinics or service laboratories (1, 2). LH assays measuring serum or plasma concentration is a proven and reliable method for determining optimal time to mate, with the main concern being that it must be used daily to accurately detect the day of the LH surge (1). The Status-LH test kit (Status-LH, Synbiotics, San Diego CA) for luteinizing hormone is an example of an available commercial in-house assay kit for measuring LH concentrations (1). The manufacturer includes instructions for performing the test and these should be followed exactly for accurate collection and testing of the sample (1). The test must be stored at room temperature and it is important to be aware of the short-shelf life of this test as it may not be accurate if expired (1). The preferred sample for this specific kit is serum and the sample should not be lipemic (high in lipid concentration causing cloudiness of the sample (7)) or hemolyzed (1) (red-blood cells burst causing pink color of the serum (7)). The rapid increase in progesterone serum concentration begins approximately 2 days before ovulation, during the LH surge. Monitoring the progesterone levels therefore allows estimation of ovulation, and if continued conformation of ovulation and fertilization period detection (1). Measurement of progesterone by using an in-house,

4 4 semi-quantitative ELISA test, especially when used in conjunction with LH assay tests, is very accurate at estimating timing of the LH surge, ovulation, and onset and termination of fertilization (1). When using a progesterone assay the initial increase in progesterone, if confirmed by subsequent increases, should be considered to have occurred on the day of the LH surge (3). Bitches ovulate an immature oocyte which unlike most domestic animals requires about 2 days of maturation before successful fertilization (8). The optimal breeding day is can be between 2-6 days following ovulation, the difference depends on the type of mating whether it be natural or artificial insemination (8). Pregnancy rates are increased if the bitch is bred more than once in the fertile period following ovulation (8). The primary advantage of using the progesterone hormone assay is the short-turn around time for results which can be available in as quickly as 20 minutes (9). An example of a commercially available in-house assay kit for the measurement of progesterone in canine serum is the K-9 Proges-Check test (Endocrine Technologies, Inc., Newark CA) (1). This test requires refrigeration storage but must be used at room temperature (1). Either serum or plasma may be used but like the LH assays the samples must not be lipemic, hemolyzed or icteric (1). The use of hormone assays has become an effective tool for small animal breeders (8). As previous stated the ability to predict peak fertility and optimal mating time of females is an important part of efficient management of breeding programs of any kind. The focus of this paper was on methods used in canine breeding management programs and specifically accurate determination of ovulation in the bitch. The knowledge of optimal mating time helps a breeder to minimize mating bitches outside the peak fertility timing following ovulation (1). The most commonly used methods of predicting time of

5 5 ovulation in the bitch including assessment of physical and behavioral changes, changes in vaginal epithelium and fluid and the use for hormone assays. Hormone assays provide the most accurate estimation of the day of ovulation (2). Both the hormone LH and progesterone concentration levels can be assessed by assay. The assay of serum or plasma progesterone every 1-3 days is very effective for estimating time of and confirming ovulation (3). The use of other methods often is inaccurate and can lead to decreases in pregnancy rate, due to the poor correlation between physical and behavioral changes in estrus and time of ovulation in bitches (3). Measurement by quantitative assay provides more accurate detection of the initial rise in progesterone allowing determination of ovulation within ±0.5 to 1.0 days (3). Accurate timing becomes very useful when breeders are planning and need to arrange meeting of the two animals (1). Failure to accurately detect ovulation time resulting in no pregnancy occurring during an ovarian cycle can be costly to a breeding management program as canines have a monoestrus cycle where the inter- estrus interval varies largely between bitches (1). Making the use of accurate methods such as hormone assays an excellent tool for management of canine breeding programs. Literature Cited (1) England, G. and P.W. Concannon. (2002). Determination of the optimal breeding time in the bitch: basic considerations. International Veterinary Information Service ( New York, USA. (2) Kustritz, M.V. (2001) Use of commercial luteinizing hormone and progesterone assay kits in canine breeding management. International Veterinary Information Service ( New York, USA.

6 6 (3) Concannon, P.W. (2002). Canine breeding management and artificial insemination: techniques and caveats. International Veterinary Information Service ( New York, USA. (4) Hadley, J.C. (1975) Total unconjugated estrogen and progesterone concentrations in peripheral blood during the estrus cycle of the dog. Journal of Reproductive Fertility; 44: (5) Concannon, P., Hansel, W., and K. McEntee. (1977). Changes in LH, progesterone and sexual behaviour associated with perovulatory luteinization in the bitch. Biological Reproduction; 17: (6) Hewitt, D. and G. England. (2000). Assessment of optimal mating time in the bitch. In Practice; 22: (7) Specimen collection, preparation and handling. (2001). Laboratory Corporation of America Holdings and Lexi-Comp Inc. col.htm (8) VanHaaften, B., Dieleman, S.J., and A.C. Okken. (1989). Timing the mating of dogs on the basis of blood progesterone concentrations. Veterinary Rec; 125: (9) Manothaiudom, K., Johnston, S.D. and R.L. Hegstad. (1995). Evaluation of the icagen-target canine ovulation timing diagnostic test in detecting canine plasma progesterone concentrations. Journal of American Animal Hospital Association; 31:57-64.