| Livestock Research for Rural Development 22 (3) 2010 | Notes to Authors | LRRD Newsletter | Citation of this paper |
Retrospective and prospective follow-up studiers were conducted during November 2004 to April 2005 in and around Arsi-Negelle, to evaluate the reproductive performance and efficiency of Artificial Insemination (AI) service in field condition. A total of 2944 dairy cows/heifers were included in the retrospective study whereas 168 dairy cows were used in field follow-up study.
The first service non return rate (NRR) in the retrospective study was found to be 86.6% (n= 2511), which was much higher than the NRR (48.2%; n=81) recorded in the field follow-up study. The first service NRR of 48.2% recorded in the follow-up study which is supposed to be due to pregnancy was much lower than first service pregnancy rate (34.5%). This may be attributed to factors including failure of return to estrus or farmers choice of natural mating in cases of insemination failure. Analysis of the breeding records of 622 dairy cows indicated that the mean duration of calving to first service (CFS) in local breed cows (mean±SD: 241±18.5 days; n=205) was significantly higher (P<0.01) than those of crossbreed cows (mean±SD: 182.0 ± 9.87 days; n=417) indicating the low reproductive efficiency of local breed cows. Only 4.5% of dairy cows (n=28) had CFS less than 80 days.
The average inter service interval (ISI) recorded in the retrospective study was (39.8 ± 3.39 days) which was a bit higher than that of the field follow-up study (33.5± 4.66 days). The proportion of cows/heifers (26.3%; n=23) that had ISI lying within the normal range of 18 - 24 days was much lower than the recommended 60%. Problems associated with management, heat detection, timing of insemination and semen quality were identified as the probable causes of the low efficiency of AI obtained in the field study.
Key words: Calving to first service, inter-service-interval, non-return rate
The grand total food production from livestock in sub-Saharan Africa is estimated at about 35 million gain equivalent tones, of which cattle only account 50% (Jahnke 1982). The population of cattle in Ethiopia is estimated at 41.5 million comprising 99.4% indigenous (zebu), 0.5% cross and 0.1% exotic breeds which are mainly kept under smallholder subsistence farming (EASE 2003). Zebu (Bos indicus) cattle are multipurpose animals with low potential for meat and milk production which is estimated to meet only 35% of the requirements (Landiver et al 1985, Mukasa-Mugerewa1989). In order to improve the low productivity of local cattle, selection of the most promising breeds and cross breeding of these indigenous breed with highly productive exotic cattle has been considered a practical solutions (Tadesse 2002). Thus, the need for clear strategies on the improvement and maintenance of indigenous cattle genetic resources is required along with clear breeding programs for sustainable genetic improvement. To date, artificial insemination (AI) is recognized as the best biotechnological technique for increasing reproductive capacity and has received widespread application in farm animals (Landiver et al 1985, Mukasa-Mugerewa 1989). Despite the wide application of AI and its success throughout the developed world, as a matter of fact, the success rate in Ethiopia is still low owing to a number of technical, financial, infrastructural and managerial problems.
Reproductive efficiency is thus poor in most cattle production systems, mainly
because cows either fail to become pregnant primarily due to management
problems, shortage of feed and high prevalence rate of reproductive diseases as
well as high calf mortality. Conservative stocking rate, a sensible year round
feeding and herd health plan and adequate AI service are is important to
improve reproductive efficiency, and hence, economically benefit from the dairy
enterprise. Moreover, the extension service must ensure that farmers get
adequate information on the input required to benefit from cross breed dairy
cows and from those of higher genetic merit.
Environmental stress and the challenge of high disease risk in cross breed cows contribute for late age at first calving and first service, high number of services per conception, and longer calving interval which are all the major areas of reproductive loss in cattle (Tegegne et al 1981, Albero 1983 and Mukasa-Mugerewa 1989). Among the management problems, poor heat detection skill by farmers and timing of insemination are the major factors that determine the success and failure of AI programme (Mukasa-Mugerewa 1989).
The measures of the level of reproductive efficiency directly or indirectly specify the magnitude of profit and highlight the problems of reproductive efficiency. Although decades have been passed since AI started in Ethiopia, there are few field studies made to evaluate the reproductive performance of cows/heifers subsequent to AI (Mukasa-Mugerewa 1989). This particular study is, therefore, conducted to evaluate the efficiency of AI programme from retrospective data and field study as well as determine reproductive performance of smallholder dairy cows managed under AI system in and around Arsi-Negelle, Southern Ethiopia where there is a widespread use of AI.
The study was conducted from November 2004 to April 2005 in Arsi Negelle, Eastern Shoa Zone of Oromia region, 225 km South East of Addis Ababa, located in the central Rift Valley of Ethiopia. Arsi Negelle district is 139,600km2 wide with an altitude ranging from 1500 to 2010 mm above sea level. The minimum and maximum temperature is 100 and 250C, respectively. Generally, the climate of the area is divided into sub humid (32%), Semi-arid (42%), and arid (26%) zones with an average annual rainfall ranging from 500mm to 1150mm.
Of the total human population, 80.0% of them depend on agriculture, while the remaining depends on market and salary based incomes.
A total of 2944 dairy cows/heifers under AI service in the district were included in a retrospective study whereas 23 local and 145 crossbreed (Friesian x other local breeds) dairy cows and heifers belonging to different small holder farms were used for a field follow-up study. Of the total cows used in the retrospective study, calving to first service (CFS) and inter service interval (ISI) were determined in 622 and 164 dairy cows, respectively. The age of the animals varied from two to ten years and all were under AI service in and around Arsi Negelle town. All local cows were managed extensively and depend on grazing, while crossbreed cows were housed and fed with cut and carry system. The by product of locally made alcohol was also used as supplement feed for dairy cows. Some dairy owners occasionally provide additional straw and Noug Cake (Guizota Abyssinica). Artificial Insemination was carried out using semen obtained from four Friesian, one Jersey and one cross breed bulls collected and distributed by the artificial insemination centre located at Kaliti and Asella.
The study comprised retrospective and field follow-up study of inseminated cows to evaluate the efficiency of AI service and reproductive performance of dairy cattle in the study site.
In the retrospective study, data were collected from records of AI service covering the period from 2001 to 2004. Artificial insemination records were obtained from AI certificates and from inseminator’s recording book. Data on the date of last calving, date of fist service and subsequent services, breed of AI bull and cows/heifers, parity number, observed heat signs and the time of insemination were collected and analyzed.
In the field follow-up study, a total of 168 cows (n=134) and heifers (n=34) were selected on the basis of postpartum first service. Animals in heat were inseminated based on the date and time of the first physical and/or behavioural heat signs. The study animals were observed by their owners or attendants two times a day during feeding for any signs of heat. There was no any follow-up during the night time. Pregnancy diagnosis was conducted about 60 days post insemination by using the rectal palpation method according to Robert (1986) and Arthur et al (1989). All Artificial inseminations were carried out by a single inseminator, who had four years of experience.
Reproductive indices including non-return rate (NRR), first service pregnancy rate, calving to first service (CFS) and inter-service interval (ISI) were determined to evaluate the efficiency of AI service and the reproductive performance of the cows in both retrospective as well as field follow-up studies according to Gaines (1989).
Non-return rate (NRR) was determined by computing the percentage of inseminated cows/heifers at a particular period of time that did not return for second insemination and which are assumed to be pregnant.
First service pregnancy rate was obtained by determining the percentage of cows/heifers that become pregnant at the first insemination after calving while calving to first service (CFS) was the average number of days from the most recent calving to the day of first insemination service. Inter-service interval (ISI) was obtained by determining the interval of days between two successive services which could be less than 3, between 3 and 17, 18 and 24, 35 and 48 or longer than 48 days (Gaines 1989).
Descriptive statistics such as percentages, averages, ranges and standard deviations were used in summarizing the data. Pair-wise comparison of the means was made employing the T-test to see for significant differences.
In the retrospective study carried out on a total of 2944 dairy cows/heifers inseminated for first time, the NRR for first service was 86.6 % while the return rate was 13.1 % (n= 390), 2.4% (n= 41), 0.07% (n=2), for the 2nd, 3rd and 4th AI services, respectively. The duration of CFS ranged from 40 to 760 days. The overall mean and standard deviation for CFS in local breed cows (n=205) and cross breed dairy cows (n=417) was 241 + 18.5 days and 182 + 9.87 days, respectively (Table 1). Of all local and crossbred cows, only 4.5% had CFS less than 80 days.
|
Table 1. Reproductive parameters recorded in smallholder cross and local breed dairy cows in and around Arsi-Negelle |
||||||
|
Study method |
Breed |
variable |
No of animals included in the study |
Mean, days |
Standard deviation, days |
Coefficient of variation, % |
|
Retrospective study |
Crossbreed
|
CFS |
417 |
182 |
9.87 |
5.42 |
|
ISI |
164 |
39.8 |
3.39 |
8.53 |
||
|
Local breed |
CFS |
205 |
241 |
18.5 |
7.68 |
|
|
Follow-up study |
Crossbreed |
ISI |
168 |
33.5 |
4.66 |
13.9 |
Comparison of the mean CFS between crossbreed and local breed cows revealed significant difference (P<0.01) with the mean CFS of local breed cows being higher than those of cross breed dairy cows.
Of the total of 164 cross breed cows in which ISI was determined in the retrospective study, the ISI ranged from 10 to 100 days with overall mean and standard deviation of ISI being 39.8 + 3.39 days. Cows and/or heifers that had ISI lying within the normal range of 18-24 days were 39 % (n=64).
In field follow-up study, although all dairy owners included in the study were found to have good knowledge of the important heat signs, such as bellowing, mounting and vaginal discharge, it was observed that dairy owners consider continuous bellowing and mounting as indicators of the proper time for insemination. Of 168 first inseminated cows/heifers included in the follow-up study, the first service pregnancy rate was found to be 34.5% while the return rate was 51.78% (n=87), 17.2% (n=15) and 3.33% (n=5) for the 2nd, 3rd, and 4th AI services, respectively. Pregnancy diagnosis in non-returned cows/heifers revealed that 58 (71.6%) cows/heifers were pregnant while 18 (22.2%) were not pregnant while the remaining were sold, died or aborted. First service pregnancy rate was the lowest in high producing dairy cows (n=9) that were at early lactation.
The average ISI between first and second AI service in the field follow-up study was 33.5+ 4.66. Only 26.4% (n=23) cows/heifers had ISI lying within the recommended range of 18-24 days and there were no cows with ISI less than 3 days. Of those cows that returned for second AI service (n=87), 62.1% (n=54) came for AI service after 24 days of the preceding service.
Of the 168 inseminated cows/heifers29.8% (n=50) got AI service before 12 hours and 20.8% (n=40) after 18 hr of the first heat sign observed. Only 46.4% (n=78) cows were served within the recommended 12-18 hours after the first heat sign.
The proportion of NRR recorded in the retrospective study (86.6%) was higher than the previous findings where 65-72% NRR was reported within 60-90 days (Garner 1991; Vanderplassche 1982). However, the NRR obtained in the field follow-up study (48.2%) was lower than the 74.78-78.5% NRR reported by the National Artificial Insemination Centre between 1991/92 and 1993/94 and the 70.8% found by Samsson (2001). These differences between the findings of the current and previous works may be attributed to factors associated with timing of insemination, feeding management, efficiency of heat detection, early embryonic mortality and presence of ovarian cyst which are all known to negatively affect fertility. The higher proportion of NNR recorded in the retrospective study (86.6%) than those recorded in the field follow-up study (48.2%) may not necessarily indicate higher insemination success or conception. This may be due to the fact that farmers usually do not return their cows for second service in case of insemination failure but rather consider natural mating.
Calving to first service obtained in the retrospective study (40 to 760 days) is by far higher than the recommended 45-60 days (Gaines 1989), which may be attributed to the poor management, feeding and failure of heat detection. The significant difference in CFS between local (241± 18.5 days) and cross breed (182 + 9.87 days) cows may suggest that dairy owners have less attention to local cows regarding feeding, housing and heat detection owing to their less economic benefit and poor behaviour in the manifestation of heat signs.
The CFS obtained for cross breed cows in this study (182 + 9.87days) is almost similar to the previous report of 184 + 68.3 days (Fikru 1994). However, it is much lower than the 276 + 10.3 days in mixed crop livestock production system at Hollota (Shiferaw et al 2003) and is a bit higher than 175 + 6.5 days reported by Samsson (2001). These variations may be due to differences in the particular management and feeding practices under which the study animals are kept. The CFS obtained in local cows (241 ±18.5 days) is, however, in line with the previous report where longer than 240 days of CFS was recorded (Tegegne 1989). The finding of only a small proportion of cows (4.5%) with CFS lying within the recommended value indicate inadequate supervision of dairy cows in heat detection, poor feeding and management of dairy cows in the study area.
The ISI (10 to 100 days) as well as the average ISI (39.8 + 3.39 days) obtained in the retrospective study is higher than the recommended 18-24 days and 21 days, respectively (Gaines 1989). The average ISI (33.5+ 4.66 days) obtained in the field follow-up study is also higher than the previous findings of 29.2+18.7 days (Fikru 1994) and 25.1+ 6 days (Albero 1983). However, it is shorter than the value reported by Samsson (2001) which was 35.8 + 3.75 days at Addis Ababa. The higher values of ISI may be due to poor management associated with heat detection and insemination technique and/or presence of ovarian cyst.
The overall first service pregnancy rate (34.5%) obtained in this study, is much lower than the recommended 45-60% (Gaines 1989) indicating the inefficiency of AI service in the study area which could be associated to several factors. The current figure is also lower than previously reported values of 46.7% (Samsson 2001), 44-45% (Shiferaw et al 2003), 46.7% (Belachew 2003) and 71.8-82.2% in Debre Zeit (Bekana 1988). However, it lies within the range of 22-46% reported by Tegegne (1989) during the dry period in Boran breed cows. Such differences may be attributed to the fact that the above mentioned previous studies were all conducted in government and research centre dairy farms where cows are kept under better feeding and management conditions.
The finding of a small proportion of cows (26.34%) that had ISI within the normal range of 18-24 days recorded in the present study is lower than the recommended 60% by Gaines (1989) and the 28.9% reported by Samsson (2001). However it is higher than the previous report of 24% (Mukasa-Mugerewa and Tegegne 1991). Moreover, about half (50.6%) of cows in this study had ISI that is out of the expected range of 18-24 days. These all variation from the normal range suggest follicular cyst or insemination at the wrong time due to incorrect heat detection in cases of short ISI while the long ISI may be due to improper heat detection, missed or silent heat, the presence of luteal cyst or embryonic mortality (Arthur et al 1989 ).
The other important factor for the failure of AI service is male infertility which may be either due to poor semen quality or poor insemination technique. In this study, one of the six bulls had poor semen quality. This may be one of the factors responsible for the lowest first service pregnancy rate observed in cows/heifers served by this particular bull. Improper insemination technique might also be a reason for the failure of AI service. It has been recommended that depositing semen in the bifurcation of uterine body just inside the internal cervical opening might help for better success rates in AI service (Seguin 1986).
Low blood glucose level due to shortage of energy in cows used for draught work during early lactation has been incriminated as a cause of infertility resulting in failure of implantation (Matthewman et al 1993). Similarly, the poor first service conception rate recorded in high yielding cows in the current study may also be related to the high-energy required for milk secretion which may lower blood glucose level causing implantation failure.
The practice of inseminating cows/heifers before 12 hrs (29.7%; n=50) and after 18 hours (20.8%; n=40) of the first heat sign in the current study shows that too early and too late insemination may also be responsible for the failure of AI in the area. Too early service has been shown to be very common cause of infertility resulting in longer herd calving interval because early conception is frequently followed by early embryonic death (Radostitis and Blood 1985; Wolfe 1993; Fetrow 1994, Bekana et al 1996).
In both retrospective and field follow-up studies, the duration of CFS and ISI were all higher than the recommended ranges of 45-60 days and 18-24 days, respectively indicating the in-efficient AI service in and around Arsi-Negelle area. The lower proportion of first service pregnancy rate recorded in this study than the recommended normal range of 45-60% further substantiates the above conclusion.
Inadequate recording system, absence of heat detection aids, improper AI technique, absence of insemination service on holidays, shortage of experienced inseminators, poor management (feeding, housing, and heat detection) of dairy cows/heifers and early embryonic mortality could be factors implicated for the poor AI efficiency found in this study.
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Received 16 August 2009; Accepted 20 January 2010; Published 1 March 2010