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2010, Vol. 5 No. 2, Article 65

 

Ultrasonographic Study of Ovarian Cyclicity in
Zebu Cows of Bangladesh

Z. Akter1, A. K. Talukder1, T. Akter1, M. S. Kabir, M. M. Kamal*2,
F. Y. Bari3 and M. Shamsuddin3

 

Department of Surgery and Obstetrics,
Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh

1Research Fellow, Department of Surgery and Obstetrics, BAU, Mymensingh.
2Upazila Livestock Officer, Department of Livestock Services, Dhaka.
3Professor, Department of Surgery and Obstetrics, BAU, Mymensingh

 

*Corresponding Author; e-mail address: dmmkamal1@gmail.com

 


ABSTRACT

A study was undertaken to examine the cyclicity in (N=10) zebu cows by transrectal-ultrasonography. Ultrasonography was done daily for two consecutive inter-ovulatory cycles of each cow. Follicles 4 mm or greater than that were measured, follicular dynamics, maximum sizes of the dominant follicles and corpus luteum, days of attaining maximum diameters were recorded. Changes in the uterus were also evaluated. The inter-ovulatory cycle length was 21.8±0.8 days. All ten cows had two waves of follicular growth. The first wave emerged on Day 3.3±1.0. The maximum diameter of the first wave dominant follicle was 12.1±1.1 mm on Day 9.3±1.0 of the cycle. Onset of atresia of first wave dominant follicle began on Day 12.3±1.0, while the second wave (ovulatory) emerged on day 12.3±1.0. The maximum diameter of second wave dominant follicle (ovulatory follicle) was 18.1±0.6 mm on Day 18.7±1.3. The diameter of corpus luteum was 23.2±1.6 mm on Day 13.1±1.5. The mean number of medium sized follicles (6-8 mm) was higher than that of small sized follicles (4-5 mm) throughout the inter-ovulatory cycle. The corpus luteum reached maximal diameter of 23.2±1.6 mm at 13.1±1.5 days. Edematous fluid in the lumen of uterus appeared dark in color with increased uterine diameter in all ten cows during Day 0 (Day of oestrus) to Day 3. Maximal uterine diameter was observed on Day 0 resulting from edematous anechoic fluid in the lumen in all cows. But from Day 6-15, the uterine diameter decreased and showed comparatively less darkness. The results indicated that indigenous zebu cows of Bangladesh seem to have follicular dynamics and cyclicity similar to other breeds of cattle.

KEY WORDS

Bangladeshi zebu cows, ovarian cyclicity, follicular dynamics, ultrasonography.

INTRODUCTION

Majority of the cattle in Bangladesh are non-descriptive indigenous zebu type. They are poor performers with regard to body growth, fertility, calving rates and disease resistance (Jabber and Green, 1983; Shamsuddin et al., 2001). Various techniques that are currently in practice for monitoring the reproductive status of the cows and heifers in Bangladesh include rectal palpation and hormonal analysis (ELISA and RIA) (Shamsuddin et al., 2006). Hormonal examination needs a specialized laboratory and is considered expensive and time consuming. Rectal palpation could be an accurate method for diagnosing pregnancy, however; it requires a highly skilled person to determine the status of the reproductive organs throughout a cycle. A complete study of inter-ovulatory cycle was needed for determining the reproductive status of the poor performing zebu cows in Bangladesh.
Apart from pregnancy diagnosis, ultrasonography could be an accurate and useful aid in evaluating the reproductive cycle, identifying the pathological conditions of reproductive organs, studying reproductive organs & tissues, characterizing reproductive events like ovulation, transition of the uterus from a diestrous to an estrous echotexture and detection of heat in cows (Ginther, 1995) The present study was therefore performed to examine the cyclicity in zebu cows by transrectal-ultrasonography.

MATERIALS AND METHODS

Study was conducted on cycling non-descript(n=10) zebu cows, aged between 4 and 6 years belonging to the Department of Surgery and Obstetrics and Veterinary Clinics of Bangladesh Agricultural University (BAU), Mymensingh. The cows were maintained under uniform conditions of feeding and management in a concrete, well-ventilated and tin-roofed shed. Animals were allowed to graze for about four hours besides feeding with green fodder, fresh straw and concentrate two times a day. Body weight and body condition score (BCS) of the cows ranged from 170-220 kg and 2.5-3.5 (1 to 5 scale), respectively.
Day 0 was considered as the day of estrus The ovarian structures were studied daily by real time B-mode ultrasonography for two consecutive estrous cycles by using a transrectal 5 MHz frequency transducer according to the method described by Ginther (1995). The ultrasound machine (PharVision MicroV10, Classic Medical Supply, Inc., USA) was set near the animal. Transducer and a video recorder (Archos 605 wifi, China) were attached to the scanner. The video recorder was connected to the electrical point. The transducer was lubricated with a ultrasound transmission gel (Aquasonic®, Parker Laboratories, Inc., USA). The cows were restrained in a squeeze chute to minimize the stress and risk of injury. Fecal material was evacuated from the rectum and the perineum was washed with clean water. The anal area was lubricated with soap and water. The transducer was inserted into the rectum and was moved forward to place it lateral to the cervix. The ovary was brought in front of the transducer face and the entire ovary was scanned. Numbers and sizes of ovarian follicles were determined at every three days and follicles were categorized as small (4-5 mm), medium (6 to 8 mm) or large (≥9 mm in diameter) (Alvarez et al., 2000). The largest follicles that were subsequently seen at Day 18 to Day 0 (day of ovulation) were considered to be ovulatory follicles. Ovulation was determined by the disappearance of the dominant follicles. Onset of atresia of follicles was considered as the day from which follicles began regressing in size. The development and regression of the corpus luteum and follicle development were carefully recorded. The changes in uterus were also recorded on the same day. Images were transferred to a computer from video recorder and static images were obtained through the computer.
Statistical analysis
The data were entered into Microsoft Excel worksheet 2000. The mean and standard deviation of onset of follicular wave, maximum diameter of first and second wave dominant follicles, day of attaining maximum diameter, day of atresia of first wave dominant follicles, maximum diameter of corpus luteum were calculated.

RESULTS

The average length of inter-ovulatory cycle was 21.8±0.8 days with two waves of follicular growth; the first wave started on Day 3.3±1.0 followed by second wave emerged on Day 12.3±1.0 (Table 1).The dominant follicle of first wave reached maximum diameter (12.1±1.1 mm) on Day 9.3±1.0 in all the ten cows (Table 1). Onset of atresia of the dominant follicle began on Day 12.3±1.0. First wave was followed by second wave that emerged on Day 12.3±1.0 with dominant (ovulatory) follicle having maximum diameter of 18.1±0.6 mm on Day 18.7±1.3 (Table 1). Small (4-5 mm) and medium (6-8 mm) follicles were found throughout the inter-ovulatory cycle. Mean number of medium follicles increased on Day 6-12, then gradually decreased from Day 15-18. On average small follicles were almost equal in numbers throughout the cycle. Dominant follicles were present from Day 9 to Day 15. Ovulatory follicles were present on Day 18 to Day 0 of the next cycle (Figure 1). The maximum follicular diameter was observed on Day 0, and then decreased on Day 3 to Day 6. Diameter again increased on Day 9 but slightly decreased on Day 12 and gradually increased from 15-18 days (Figure 2).
The corpus luteum attained maximum diameter of 23±1.6 mm at 13.1±1.5 days. Edematous fluid, appearing dark in colour was observed in the lumen of uterus with increased uterine diameter in all ten cows during Day 0 to Day 3. Maximal uterine diameter, resulting from edematous anechoic fluid in the lumen was observed on Day 0. From Day 6 to Day 15, the uterine diameter decreased and uterine fluid showed less darkness.

DISCUSSION

Results of the present study defined the interval between ovulation, size of ovulatory follicle and number of follicular waves in inter-ovulatory cycles of zebu cows. All cows were with two follicular waves with inter-ovulatory cycle length 21.8±0.8 days. Inter-ovulatory cycle length of 21.0±3 days was earlier reported in Zebu cows (Ruiz et al., 1999). In European breeds too, the inter-ovulatory cycle length was similar to that of zebu cows (Vaca et al., 1985; Vale-Filho et al., 1986.
In the present study, the first wave emerged on Day 3.3±1.0 and the second wave emerged on Day 12.3±1.0. However, Savio et al.( 1988) and Sirois and Fortune(1988) observed that the first and second (ovulatory) waves in a two-wave cycle commence on Day 2-4 and Day 10-11, respectively. Ovarian follicular development in cattle occurs in waves (Sirois and Fortune, 1988). A wave of follicular growth involves the synchronous development of a group of follicles, one of which become dominant and achieves the greatest diameter suppressing the growth of the subordinate smaller follicles (Pierson and Ginther, 1987b). More than 95% of inter-ovulatory cycles in cattle are composed of either two or three follicular waves (Adams, 1999). Several studies showed the prevalence of two wave follicular activity during an inter-ovulatory cycle in cattle (Knopf et al, 1989; Ginther et al., 1989a). On the contrary, a higher prevalence of cycles with three follicular waves was observed by many authors in European (Savio et al., 1988; Sirois and Fortune, 1988) and in Zebu cows (Viana et al., 2000).
The follicular waves are first detectable as 4–5 mm follicles on Day 0 and 10 for two-wave inter-ovulatory intervals and on Day 0, 9 and 16 for three-wave inter-ovulatory intervals (Ginther et al., 1989a). The day of onset of follicular wave was defined as the day on which the dominant follicle was retrospectively traced to be 4 to 5 mm in diameter (Burke et al 2000). The main characteristics of follicular growth and atresia are affected by wave order (Savio et al., 1988; Ginther et al., 1989a) and can also change among animals due to many factors such as breed (Figueiredo et al., 1997), reproductive stage (Roche and Boland, 1991), season (Badinga et al., 1994), energy balance (Rhodes et al., 1995), etc.
During present trial first wave dominant follicle attained maximum diameter of12.1±1.1 mm on Day 9.3±1.0. Gaur and Purohit (2007) reported that first wave dominant follicle in a two-wave cycle in zebu cattle reached maximum diameter of 11.75 mm on Day 5.0, whereas the dominant follicle of the first wave in the three-wave cycle emerged on day 4.13±0.99 and reached maximum diameter on day 6.5 ± 0.88.
Each estrous cycle has two or three waves of follicular development if the second or third dominant follicle ovulated (Burke et al., 2000). Onset of first wave dominant follicle atresia was observed on day 12.3±1.0. Similar findings were reported by Ginther et al (1989a) and Knopf et al (1989) who observed that the first dominant follicle regression occurred only after day 11 or 13. These findings however differ from reports of Gaur and Purohit (2007) wherein the onset of atresia was on the Day 10.5±1.1 in zebu cows.
The second wave emerged on day 12.3±1.0. The dominant follicle of the second wave reached its maximum diameter on Day 18.7±1.3 with dominant follicle maximum diameter of 18.1±0.4 mm. This dominant follicle ovulated. These observations were in close agreement with those of Savio et al., (1988) Sirois and Fortune (1988). Ginther et al. (1989b) and Gaur and Purohit ( 2007).
The corpus luteum reached maximal diameter of 23.2±1.6 mm at 13.1±1.5 days. Corpora lutea have been reported to range in size from 10 to 35 mm with maximum size being reached around Day 12 of the estrous cycle in non-pregnant animals (Pierson and Ginther, 1984).
The mean number of medium sized follicles was higher than small sized follicles throughout the inter-ovulatory cycle. It was contrary to earlier reports where-in the mean number of medium sized follicles was lower than small sized follicles throughout the estrous cycle (Gaur and Purohit, 2007). Lucy et al. (1992) observed that during the early stage of estrous cycle (1-5 days), the number of small follicles (3-5 mm) decreases, while the number of medium follicles (6-9 mm) increases. Alvarez et al (2000) had recorded a greater number of small and medium follicles in Brahman cows adapted to the tropics.
The largest follicles present on the ovaries between 6 to 9 days and15-18 days were considered as the first dominant and second dominant follicles of the inter-ovulatory cycle respectively. Gaur and Purohit (2007) assumed the largest follicle present on the ovaries at 5-7 days to be the first dominant follicle of the inter-ovulatory cycle and the largest follicle that was subsequently seen was defined as the second dominant follicle.
Ultrasonic characteristic of edematous endometrium appeared as dark during estrus period, grayish during diestrus. Maximal uterine diameter was observed on Day 0 (Day of estrus) resulting from edematous anechoic fluid in the lumen in all animals but from Day 6 to Day 15, the uterine diameter decreased and uterus showed less darkness. There is conformity with reports of Pierson and Ginther (1987a) and Bonafos et al (1995). Transrectal ultrasonic imaging has permitted assessment of changes in shape of the uterus during various reproductive states in heifers (Pierson and Ginther, 1987b). In cows, maximal uterine diameter occurred during estrus, when uterine tone was highly turgid.
Ultrasonography was proved to be a valid technique for determining the uterine activity. The sizes of dominant follicles, ovulatory follicles and corpus luteum recorded in zebu cows during the present study were comparable to those of other breeds. Although ultrasound is more accurate than rectal palpation for assessing ovarian follicles, it is however difficult to distinguish between developing corpora lutea and older regressing corpora lutea by either technique (Pieterse et al., 1990).

ACKNOWLEDGEMENTS

The authors are grateful to United States Department of Agriculture (USDA) for funding the research through ‘Introduction of Herd Health Services for Sustainable Improvement of Dairy Production and Marketing Through Farmers Association in Bangladesh’ project that is being implemented at the Department of Surgery and Obstetrics of Bangladesh Agricultural University.

REFERENCES

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  2. Alvarez P, Spicer LJ, Chase CC, Payton ME, Hamilton TD, Stewart RE, Hammond C, Olson TA and Wettemann RP (2000) Ovarian and endocrine events during an estrous cycle in Angus, Brahman and Senepol cows in a sub-tropical environment. Journal of Animal Science 78: 1291-1302.

  3. Badinga L, Thatcher WW, Wilcox CJ, Morris G, Entwistle K and Wolfenson D (1994) Effect of season on follicular dynamics and plasma concentration of stradiol-17β, progesterone and luteinizing hormone in lactating Holstein cows. Theriogenology 2: 1263-1274.

  4. Bonafos LD, Kot K and Ginther OJ (1995) Physical characteristics of the uterus during the bovine estrous cycle and early pregnancy. Theriogenology 43: 713-721.

  5. Burke CR, Day ML, Bunt CR and Macmillan KL (2000) Use of a small dose of estradiol benzoate during diestrus to synchronize development of the ovulatory follicle in cattle. Journal of Animal Science 78: 145-151.

  6. Figueiredo RA, Barros CM, Pinheiro OL and Soler JKP (1997) Ovarian follicular dynamics in Nellore breed (Bos indicus) cattle, Theriogenology 47:1489-1505.

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TABLES

Table 1. Characteristics of interovulatory cycle in zebu cows with two waves of follicular growth.

Parameters

Value

Interovulatory cycle length (day)

21.8 ± 0.8

Onset of first  follicular wave (day)

3.3 ± 1.0

Day of attaining maximum diameter of dominant follicle of first  follicular wave

9.3 ± 1.0

Maximum diameter of dominant follicle of first follicular wave  (mm)

12.1±1.1

Onset of atresia of dominant follicle of first  follicular wave (day)

12.3 ± 1.0

Onset of  second  follicular wave (day)

12.3 ± 1.0

Day of attaining maximum diameter of dominant follicle of second follicular wave

18.7 ± 1.3

Maximum diameter of dominant follicle of second follicular wave (mm)

18.1 ± 0.6

Day of attaining maximum diameter of corpus luteum

13.1 ± 1.5

Maximum diameter of corpus luteum (mm)

23.2 ± 1.6

Data are generated from eight interovulatory cycles in four cows. Values are expressed as Mean±SD  

FIGURES



Figure 1. Number of small, medium, dominant and ovulatory follicles with regard to day of interovulatory cycle in zebu cows
Ultrasonographic Study of Ovarian Cyclicity in Zebu Cows of Bangladesh


Figure 2. Mean diameter with regard to interovulatory cycle in zebu cows
Ultrasonographic Study of Ovarian Cyclicity in Zebu Cows of Bangladesh



Figure 3. A dominant follicle (18 mm) and a corpus luteum (25 mm) of zebu cows

Ovarian Follicle Corpus Luteum

Ovarian Follicle                                                                   Corpus Luteum

 

 

 


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