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Dairy cattle fertility and the role of estrus induction in improving reproductive performance of cows with no history of estrus after calving

Wedajo Muleta Tadeg, Alemayehu Lemma Biru1, Tefera Yilma Mekonnen1 and Abadi Amare Reda2

Kombolcha college of Agriculture, P O Box 56, Kombolcha, Ethiopia
1 Addis Ababa University College of Veterinary Medicine and Agriculture, Bishoftu, Ethiopia
2 School of Veterinary Medicine, Wollo University, Dessie, Ethiopia


The fertility of dairy cattle is an increasing concern of dairy farms worldwide, as it affects the productivity and sustainability of dairy farming. The aim of this study was to assess the status of cow fertility and evaluate the efficacy of mass estrus induction with PGF2α on reproductive performance of cows with no history of estrus after parturition. Observational study (N = 121), cross sectional investigation (N = 246) and estrus induction experiment (N = 79) were the type of studies employed to prove the aforementioned objectives. The mean (SD) days to first estrus after calving and days open were 97.347.7 and 169.4113.3 days, respectively. The number of services per conception and calving interval were 2.79 1.19 days and 458.9117.3 days, respectively. For estrus induction experiments, the estrus response rate improved from 62 to 73%, while pregnancy improved from 28 to 30%, by performing a second injection. On a single injection 27 calves were obtained, whereas through double injection 38 calves were obtained, which means 11 calves were lost because of failing to give the second injection. In the compression of estrus response and conception or pregnancy rates rates among the mass estrus synchronization program held by the government, the experiment done in this research and naturally induced estrus there was statistical significant difference in conception rates with higher conception rate(92.1%) in naturally induced dairy cattle followed by the estrus induction done in the experiment ( 56.3%) and the lowest conception rate was in the mass estrus induction program done by the government campaign. The fertility parameters assessed for reproductive performance were below the standard in dairy cattle breeding program and the improvement practice by using mass estrus induction and mass artificial insemination used was not effective and had been practiced out of the proper protocol. However, the experiment in this study confirmed that proper application of estrus induction protocol could help early estrus induction and conception of dairy cattle with better performance. It was concluded that dairy farmers should be advised to manage dairy cattle properly and the estrus induction program should be practiced in the right protocol for a particular hormone.

Keywords: breeding, hormone, pgf2α, protocol, reproduction, synchronization


In Ethiopia, like in other developing countries, dairy farming plays a vital economic role (Getabalew et al 2019). The higher nutritional content of milk and milk products coupled with the highly rising human population and increasing urban dwellers significantly increase the demand for milk and milk product consumption (Centre 2017; Yilma et al 2011). This change in the demand requires increasing production of milk either by increasing productivity per animal or increasing the number of animals. But as the later requires greater land resource, improving productivity of individual cow is the best option (Centre 2017).

The two most important determinants, which should be considered in dairy economy are milk productivity of dairy cows and their reproductive performance (Alemyehu and Moges 2014). Accurate and timely heat detection of dairy cattle affects achieving the expected productive and reproductive performance in many of dairy farms (Graves 2009). A proper managerial practice on genetic upgrading and fertility control is required to utilize the complete milk yield prospective of this genotype (Getabalew et al 2019). One of the important factors affecting the efficiency of the dairy industry is the reproductive performance of dairy cattle. Most important traits of reproductive performance in postpartum dairy cattle include days to first service, days to conception, calving interval, and services per conception, conception rate, estrus detection rate, and pregnancy rate. Repeat breeding and anestrus cases are most important parameters affecting the reproductive performance of dairy cattle (Gezu and Azage 2018).

Accurate detection of estrus is crucial for good husbandry practice of cows. Because of new scientific inventions estrus and ovulation have been manipulated through the use of hormones. Better utilization of AI, calf uniformity shortening of calving interval are the advantages of manipulating estrus cycle by the use of estrus induction and synchronizing hormones (Ashvinkumar et al 2018). There are reports on estrus synchronization in some other sites in Ethiopia with estrus response of 74.5% (Gatew et al 2018), 72.2% (Abiyot and Eyob 2019) in local and crossbred dairy cattle in Sodo, 75.6% in local and crossbred dairy cattle in East Welega. However, reported conception rates were very poor including 30% in Boran and cross breed dairy cattle (Gezu and Azage 2018) and 10.7% in cross breed and local cattle (Dereje 2018).

There have been frequent complaints on reproductive performance problems in dairy cattle especially in smallholder farmers such as long calving interval and anestrus cases. There was also complaining about the success of using hormones as reproductive management tool in Ethiopia. Significant proportions of farmers in different sites gave negative feedback on the use of estrus synchronization program. Previous studies showed that about 88.3%, 6.98%, and 4.65% farmers were responded for poor pregnancy rate, poor heat response, and unavailability of the service, respectively (Gatew et al 2018). Furthermore, about 66.7% of the people had low perception on the use of estrus synchronization technology in West Shewa zone (Binesagn 2015). Similarly, there was a complaint on the use of mass-estrus induction and mass AI program in the study area. It was hypothesized that two injections of PGF2α at 14 days interval alongside estrus detection and AI between injections could be better than the single injections alone. Re-injection of PGF2α after 14 days for cows without any manifestations of estrus might be a proper method to solve the above mentioned problems. This procedure could be cost effective than the single-injection protocol and improve effectiveness of heat induction and ensure the success of AI. The aim of this study was to assess the status of cow fertility and evaluate the efficacy of mass estrus induction with PGF2α in improving fertility for cows showing no signs of any estrus after parturition.

Materials and methods

Study area

This study was conducted in Dessie and Kombolcha districts of South Wollo Zone in Amhara region, Ethiopia from September 2016 to August 2019. The capital city of South Wollo zone, which is named as Dessie town, is situated 401 km to the north of Addis Ababa. It has a scope/longitude: North11 7' 59.99" East 39 37' 59.99" and with a normal rise: 2,494 m and elevation of between 2400-2800 m above the ocean level in Amhara National Regional State. The yearly downpour fall of the territory is going from1100 -1200 mm and the mean yearly least and greatest temperature is 15 and 270 C, individually. Kombolcha is found 380 km upper east of Addis Ababa at the scope of 11 4′ N 39 44 E, longitude of 11.067 N 39.733 E, and height somewhere in the range of 1842 and 1915 m above the ocean level. The locality has a yearly mean temperature of 11.7-24.9 C and gets the most limited precipitation from March to May and the longest precipitation from June to September (750–900 mm). The town is situated in a scope of heights somewhere in the range of 1,500 and 1,840 m above ocean level with normal precipitation of 750 to 900 ml during the examination period. Its yearly temperature ranges from 25 to 30 C and the overall moistness of the locale shifts from 23.9 to 79 (NMSA 2013).

Study animals

A total of 246 animals, which had been included in the mass-estrus synchronization and mass AI campaign were included in this study. This was to evaluate the status of mass estrus induction program held by the government. Out of which 121 dairy cattle (103 cows and 18 heifers) were selected for a follow up study to gather data on key reproductive performance indicators to evaluate their reproductive performance. Out of the 121 dairy cattle, 79 dairy cattle were selected for the experiment. From these 79 dairy cattle, 43 were local and 36 were crossbred (Holstein*Zebu) dairy cows. The cows were non-pregnant, had CL, and were >60 days postpartum with body condition score (BCS) of 2.5 (on 1-5 scale). Animals were examined for general health and were subject to gynecological examination to avoid cows with abnormalities. Among those animals selected, 21 were managed under pasture extensive management system and the remaining 48 were housed under intensive system. A total of 73 farmers were beneficiaries of mass estrus induction and were interviewed to gather information for their perception on mass estrus induction program and information on estrus response and pregnancy rate after estrus induction were gathered on 246 dairy animals owned by these farmers.

Study design
Observational study

The study was conducted from September 2016 to August 2019. A periodical record of reproductive performance parameters of the dairy cattle within the two districts was carried out using a predesigned data collection sheet. Data included were age at first estrus, age at first breeding, age at first calving, days open, calving interval, number of service per conception, length of estrus and duration from calving to first estrus. Response variables were studied based on location, breed, BCS, and parity number. Other parameters such as 100 days in calf rate, 200 days not in calf rate, 80 day submission rates, and conception rate to first service were also recorded.

Cross sectional study

A structured questionnaire was used based on personal interview to collect data from a group of dairy farm owners and /or attendants. Contents of the questionnaire included estrus and pregnancy rates of their dairy cattle after estrus induction program and perception of farmers on the estrus synchronization program in the districts.

Experimental study

The 79 cows selected for this experiment were given an intramuscular injection of 25 mg (2 ml) of PGF2α (Synchromate, BREMER PHARMA, Warburg, GERMANY). Estrus was observed every day starting day 2 post treatment three times a day (morning, noon, early evening) for the next 5 to 9 days. Observation was carried out for 30 minutes each day and, cows that showed estrus were inseminated at standing estrus based on the AM-PM rule. Cows that did not come into estrus were subjected to a second PGF2α treatment 14 days later and were bred at standing estrus the same manner. Pregnancy was diagnosed 60 days post AI by rectal palpation. The experiment was done to evaluate estrus response and pregnancy rate by the first and second hormone injection and decide the best protocol in this study. On the other hand the estrus response and pregnancy rates found by the experiment were compared with the responses from mass estrus induction and mass AI program held by the government campaign. Similarly estrus response and pregnancy rates from the result of the experiment were compared with the estrus responses and pregnancy rates from natural estrus from animals without intervention (naturally estrus induced animals and their pregnancy).

Data analysis

The collected data were coded and entered into Microsoft-Excel 2010 spread sheet. After, the coded data were entered into SPSS version 20 where descriptive statistics were obtained for days open, NSPC, CI, and the other reproductive performance traits. The descriptive statistics was also used to determine estrus and conception rate. Chi-square test was carried out to assess the statistical significance among the outcome variables and risk factors in the three studies.

Status of Reproductive Performance

The age at first service ranged from 18 to 28 months with a mean of 21 3.1 months. The age at first service and age at first calving were 21.42.7 and 31.3 3.7.

In this study the days open was found to be 170.2, the number of service per conception was 2.8 and the calving interval was 458.9 days, which are very long (Table 1).

Table 1. Descriptive parameters of some reproductive traits in local and cross breed dairy cattle





Mean SD

Days open (days)










Calving interval(days)





Calving to first service (days)





NSPC = Number of service per conception, min. = Minimum, Max. = Maximum

In calfrate and submission rate

The percentage of the cows those turn out to be pregnant by 100 days after calving was 36.7% (n=44). This implies that 36.7 % cows will give birth within around 13 months of their preceding calving. The 200 days not in calf rate was 28.1% (n = 34). This indicates that dairy cows, which did not get pregnant within 200 days after calving, were 28.1 %. The 80 days submission rate and conception rate by the first estrus were 24.8% and 27.9%, respectively.

Mass estrus induction

The information from interview indicated that artificial insemination was carried out to all cattle at the third day of hormone injection without heat detection. Most of the respondents, around 60.3% who were beneficiaries of mass estrus synchronization and artificial insemination (AI) for their dairy cattle, were not informed to detect heat after prostaglandin injection. Around 74% of respondents were not satisfied in the mass synchronization and AI program, the reason for not satisfied being the absence of estrus response after hormone injection by 35.6% of respondents and due to the absence of pregnancy by around 38% of respondents.

The total estrus response rate and pregnancy rate of animals after mass estrus induction as of the information from owners interview on individual animals was very low (Table 2).

Table 2. Dairy cattle response to mass PGF2α based estrus induction and mass AI



Estrus response
N (%)

 N (%)

Gave birth
N (%)

N (%)




15 (14.5)







36 (26.2)

3 (2.0)







N=number of animals included in the study

Experiment on the use of prostaglandin F2α

The experiment was done on a comparison of single injection with reinjection (double injection) of PGF2α and the comparison of mass estrus synchronization and mass AI held by the government program with the experiment done on the result of the experiment and natural esters and response to insemination (Tables 3 and 4).

Single and double injection of PGF2α

In this experiment the estrus response rate was improved from 62 to 73%, while the pregnancy rate was improved from 28 to 30% from performing a second injection of PGF2α for the non-responded animals for the first injection. The normal program is a single injection, which means 11 calves were lost because of failing to give the second injection; 27calves instead of 38 calves were obtained (Table 3).

Table 3. The impact of protocols on the success of estrus synchronization on local and dairy cattle



N (%)

N (%)

Gave birth
N (%)

Sex of calves N (%)

N (%)



Sigle PGF2α






14 (51.8)


Double PGF2α











40 (56.3)





* Added value by second injection to the total result

Estrus response and pregnancy rates between categories

Table 4. Chi –square comparison of estrus and pregnancy responses in dairy cattle









Synchronization Mass






synchronization Experiment




Without intervention (Natural)





synchronization Mass






synchronization Experiment




Without intervention (Natural)




N= Number of animals injected PGF2α, N responded = Animals came to estrus or pregnant

The estrus response rate and conception rate/pregnancy rate were compared among groups of mass estrus induction program, the experiment employed, and when no intervention was made in dairy cattle. The estrus response rate was significantly higher (p<0.05) in dairy cattle when the experiment was done and the lowest response to estrus being in mass estrus synchronization. While the conception rate was higher in dairy cattle when not intervention by hormone treatment was done with significant difference (p< 0.05) and the lowest conception rate was when mass estrus induction and mass AI were employed (Table 4).


Reproductive performance

The mean age at first service of heifers in this study was slightly higher than the finding of 20.35 (Blen et al 2016) in Bishoftu town in Ethiopia. Moreover, lower mean age at first service of 18.73.7 and 18.73.5 months (range 13 - 26 months) for crossbred cattle reared in Bishoftu and Aakaki, respectively, were also reported (Genzebu et al 2016). However, there were also findings with higher age at first service of heifers which was reported 26.8.54 months in crossbred and indigenous breeds in West Shewa, Ethiopia (Abera 2016), and 24.9 months in Assela town, Ethiopia (Hunduma 2012). These differences in the result might be due to different factors like management factors, the breed of the animal, and season of the year and other related factors. However, the age at first estrus, age at first service and age at first calving in this study were within the most acceptable range in the context of the country.

The length of days open (DO) in this study was longer than the previous findings of 122.4 days for crossbred cows in West Shewa, Ethiopia (Abera 2016), 5.19 months in Jima town Oromia (Belay et al 2012), 85.6 days in Asella town (Hunduma 2012) and 113.9066.01 of days open (Raymond 2009) in Bishoftu, Oromia Ethiopia. On the other hand longer calving to conception interval or days open was also reported to be 257days (Ali et al 2013), 285 days in and around Nazareth town (Gizaw 2011) in Andassa ranch Northwestern Ethiopia and 176.8 days in market-oriented urban dairy farms in and around Addis Ababa (Kebede and Lemma 2011). The difference in the value of these days open might be due to the difference in the study area, sampling, and sample size and statistics used in the analysis of the data.

The long days open in this study shows, the problem is very series when it is assessed by representative management goals for days Open that should be used as benchmarks in the evaluation of herd’s reproductive performance in which it pronounces the days open 85- 110 days is excellent but over 145 days is sever series problem (Raymond 2009) . The mean SD number of services per conception (NSPC) in the present study was higher than the previous reports of 1.55 NSPC for dairy cattle in southern and north western part of Ethiopia, 1.750.07 around Addis Ababa (Kebede and Lemma 2011), 1.67 NSPC in Crossbred dairy cattle in Zeway (Yifat et al 2009) and 1.75 in Bishoftu (Abunna 2018 ). The extremely increased value of NSPC in the present study indicates that there are frequent unsuccessful AI services. This might be due to problems in the supply of liquid nitrogen, which may result in inseminating dead or poor quality semen, inappropriate insemination technique because of poor skills of AI technicians, poor heat detection or infections of cow reproductive tract. Comparing the present finding with previous studies in crossbred dairy cattle in Ethiopia shorter calving intervals, of 12.76 – 14.7 months (Ibrahim et al 2011) were registered. And longer mean calving intervals ranging from 16.06 – 21.36 months were also reported by (Asfaw 1999; Shiferaw et al 2013; Mureda and Mekuriaw 2007). The differences might be due to variations in feeding and/or breeding management in the research area. All these findings including the result of the present study indicate dairy cattle in Ethiopia have prolonged intervals of calving between successive calving, which implies reduced fertility affecting productivity and profitability of the dairy sector of the country.

This study showed that the percentage of the cows those turn out to be pregnant by 100 days after calving was lower than the expected and the lower limit of the standard in which farmers expected to achieve 58% and below 45% seeks advice. The percentage of animals that did not get pregnant within 200 days after calving in this study was very much higher than expected standards 13% implying the need for improvement in less than 19% (National Milk Laboratory (NML n.d). All of these values indicate that reproductive performance is very poor and therefore there is a need for assistance to have better performance based on the achievable measures of reproductive performance in year-round calving herds.

The role of mass estrus synchronization as reproductive management role

The respondents for the success of mass-estrus synchronization in this study indicated that most of the respondents were not informed to detect heat after hormone injection and were not satisfied by the service. The reason for no satisfaction mentioned were the absence of pregnancy and the absence of estrus induction by the hormone injection. Although there was variation in percentage, there were other findings that reported people’s dissatisfaction on the use of estrus synchronizations and mass AI program. Similar findings include that the majority (67.15%) of estrus synchronization users had low perception towards estrus synchronization and mass AI and the major reasons were the absence of estrus and pregnancy (Berry and Cromie 2006). On the other hand greater percentages of respondents were satisfied, indicating that the program has to be continued (Gizaw 2019). The higher satisfaction in the previous study might be due to the awareness created on heat detection to the people and use of the write protocol recommended for PGF2α which not practiced in this study area.

This low response rate of estrus and pregnancy rate in this study was due to the protocol used in the mass-breeding program. The protocol used by mass-estrus induction program was PGF2α injection at day zero (day 0) followed by blind insemination of all hormone injected in dairy cattle at the third day of hormone injection. This indicates that the program was out of the prescribed protocol. All the literature and the manufacturer of the hormone approved the use of prostaglandin should follow the protocol either one-shot PGF2 or two shots of PGF2α and AI is made on the bases of heat detection after hormone treatment (Tiwari 2019). Therefore, the mass-estrus induction and mass AI used were not properly implemented. Although it had been said that a single injection of PGF2α is preferable than double treatment due to having the same estrus response and less cost (Ejigayehu and Alemayehu 2018). This finding confirmed that a better result can be achieved with reasonable cost by using combinations of single and double injections with estrus detection between treatments which result in better response in estrus and regency with still reasonable cost. Although single injection of PGF2α was not that much successful in estrus induction, double injection of those animals not responding to the first injection boosts the estrus response rate by using PGF2α. This modified use of two-shot PGF2α is advantageous to optimize the efficiency of estrus synchronization than the use of only single shot PGF2α also supported by (Zewude 2018). The use of PGF2α in the experiment resulted significantly better estrus response rate than mass estrus induction program held by government campaign program and natural estrus response. However, the conception rate was significantly higher when the estrus was natural than any of interventions. This was due to the experiment followed the exact protocol on the application of the hormone PGF2 while mass estrus and mass AI program were done without heat detection and without selection of appropriate body conditions and reproductive status which resulted in significantly lower estrus and conception rates. This is supported by the idea describing that a good management practice and selecting cows that have good body condition are the two most indispensable necessities for successful estrous synchronization and AI (Getabalew M and Alemneh 2018).

Conclusion and Recommendations

The reproductive performance of dairy cows here studied had extended calving interval, due to long days open as a result of repeat breeding and long anestrus periods of dairy cattle. The important and achievable measures of reproductive performance in year-round calving herds here used reveal below standard 100 days in calf rate, 80 days-submission rate and conception rate, and above the recommended 200 days not in calf rate. The use of PGF2α by mass estrus synchronization and mass AI program was not effective and was very disappointing. In the mass estrus induction program animals were not selected properly in their body condition and reproductive status and AI after hormone injection was given without confirmation that the animals is in heat. Although the farmers reported the problem is on the hormone, it had been proved the cause to be a misuse of the hormone by the mass program and proved by the experiment. The experiment in this study proved that PGF2α given at 14 days apart with heat detection and artificial insemination after each treatment to animals showed better performance and cost-effective reproductive management tool. To overcome the challenge in reproductive performance of dairy cattle there is a need to include other determinant factors like appropriate feeding, management nutrition, heat detection in addition to appropriated use of reproductive hormones to induce estrus.


The authors gratefully acknowledge Wise team PLC for providing AI kit and PGF2 α hormone for synchronization experimental study.


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