The study was conducted in Hawassa city, Sidama Regional sate, Southern Ethiopia. The area is situated at 275 km south of Addis Ababa at a latitude of 7°04'N and a longitude 38°31'E on the escarpment of the Great Rift Valley. The altitude ranges from 1650 to 1700 m above sea level. The mean annual rainfall and temperature are 900-1100 mm and 27°C, respectively. The total livestock population of Sidama zone is estimated to constitute 1,721,341 cattle, 228,941 goats, 457,465 sheep, 204,460 equines, 725,540 poultry and 44,492 beehives. Specifically, Hawassa city administration has 155 small to large scale dairy farms with total population of 40,163 animals (Hawassa city administration, 2021).

There were one hundred fifty five (155) dairy cattle farms in six sub cities of Hawassa. The study animals were Holstein Fresian cross breed owned by both privates and government in Hawassa city. All study farms were grouped under intensive dairy farming system. The sources of feed for animals include grass, crop residue, concentrates and agro industrial byproducts. The animals are given feed and water three and two times per day respectively. Treatment, vaccination and management of health problems were done by veterinarians that have employed in each sub-city. Culling in the farms was practiced as a result of aging, decreased production and reproduction as well as incurable diseases. All the farms have space for exercising for the animals. Both AI and natural service methods are used in the area for breeding.

A cross-sectional study was used to collect information with observational and questionnaire survey from December 2021 to June 2022. Questionnaire survey was conducted at eighty four (84) dairy farms in six sub cities of Hawassa, namely: Tula, Haykdar, Meneharia, Mehal-ketema, Tabor and Misrak.

Semi-structured questionnaire was prepared and used to interview 84 farm owners. The questionnaire was prepared in English language and translated to Amharic language for easy understating by respondents. During the interview, the respondents included in the study were briefed about the objective of study before presenting the actual questions. Different farm records were used for collections of individual animals related data.

In the survey, data like address of owner, breed, parity, body condition score, heat detection, time of insemination, number of services pre-conception, sex of previous newborn, average milk yield, reproductive performances indicators, management factors and reproductive health problems were included. The animals body condition score were recorded on the scale of 1-5 based on criteria set by 55. Age of animals was recorded per year that was collected from farm records as well as by interview of owners and individual animal examination. Further, age classified as <4, 4-6 and > 6 years. Parity number and daily milk yield/cow/day were recorded from data of the farm in addition to questioning owners.

The sample size was determined by using the formula described by Yamane, (1973) as follows.

Sample size n=N/1+N (e)², N=total population, e=allowable error (5% precision).

The total number of animals found in 155 farms of Hawassa city was 40,163. Therefore sample size was calculated as 396 animals; but 409 animals data were collected to represent all farms proportionally. In individual animal selection, sampling was done proportionally in which female cows that previously have at least one parity and having calves with the age of less than six months to collect clear data in determining sex of newborn. Therefore, 2-6 animals were sampled proportionally based on herd size from selected farm.

All owners of selected farms were interviewed for questionnaire data collections. For this sample size were calculated by using the formula given by 15 which is = 0.25/SE2, Where: N= sample size, SE (standard error) = 5%. Therefore, by using the above formula, the sample size was calculated as 100 farm owners to be interviewed. However, based on owners interest and easy of accessibility with available time and resources, only 84 farms out of 155 were examined for this study.

All data were entered in to Ms-Excel spread sheet, coded and analyzed using STATA version 12. The data were summarized using descriptive statistics of percentage and mean to determine status of reproductive performances in the study area. The variation between different factors and its effect on rate of conception after services was analyzed by using Chi-square test (χ²) and odd ratio (OR) with confidence level of 95%, whereas P < 0.05 were considered for significant value.

Reproductive performances of dairy cows in the current study was evaluated by age at onset of puberty, age at first service, post-partum period, calving interval and number of service per conception (NSPC) (Table 1). This research indicated that the mean age at first services of study animals was 17.53+0.035 with difference of relatively one month from onset of puberty. The postpartum period/days was more than standard with mean +SE of 84.35+0.819. The NSPC was higher in animals breed naturally (1.87+0.056) as compared to using AI (1.69+0.049).

In the result of this study, the relationship between animal related factors (such as age, parity, BCS, average milk yield per day, previous history of reproductive health problems as well as methods of breeding) with conception to first service was assessed. Accordingly, age, parity and history of reproductive health problems were significantly (P<0.05) affect the conception to the first service, whereas BCS, average daily milk yield and breeding mothods have non-significant effect on conception to first service (p>0.05). Conception to first service was decreasing with increasing age of animals significantly. Female cows with parity 2 and 3 have more success rate as compared to parity 1 (Table 2). Animals with reproductive health problems were significantly affected (P=0.001) in conception to first service than animals with absence of previous history of reproductive health problems.

Age and parity of animals showed strong relationship with NSPC. An increase in age of animal in year cause increase NSPC significantly with odds of 1.39. Similarly, the NSPC increases as number of party increases with odds 0.56. (Table 3).

The percentage of animals conceived to the first service differs among different sub-cities. However there is no significant difference (P>0.05). Mehal-ketema and Meneharia sub-cities showed higher conception rate as compared to others (Figure 1). From the figure the lower conception rate to first service in Misrak and Tula (Figure 1a) resulted in higher number of service per conception with in the same sub-cities (Figure 1b).

This study indicated, the rate of conception was increased with increasing number of services in both natural services and AI. Higher conception rate to first services of 44.61% were reported when AI used than natural services with 37.07% (Table 4).

There was no significant effect of study area and breeding methods on sex ratio of newborn calves (P>0.05). However, a slight difference in producing female newborn when a natural service used with 53.17% as compared to AI with 51.47% of female newborn were reported (Table 5).

In this study, reproductive performances of dairy cows were assessed in terms of age at onset of puberty, age at first service, post-partum period, calving interval and NSPC. The mean+SE of ages at onset of puberty of heifers, age at first service, post-partum period and calving interval in this study were 16.67+0.036 months, 17.53+0.035 months, 84.35+0.819 days, 12.88+0.046 months respectively. An average NSPC under AI and natural services were 1.69+0.049 and 1.87+0.056 respectively. The overall mean of age at first service is lower than the previous studies of 36.8±0.8, 24.3±8.01, 24 ±4.16 and 26.8 ± 0.34 months reported by 154217 respectively in different study areas of Ethiopia. On the other hand, the current report of age at first service was higher than the results that has been shown in previous studies in well-nourished temperate heifer that have potential to conceive at 14-15 months of age 2527. The variation between current study and previous report will be due to breed differences, study area, management of animals, nutrition, environmental stress, herd size and social interactions as scientifically confirmed to affect the age at first onset of puberty in heifers 36431. In this study, urban dairy farming practices, cross breed animals of the study and improved management as compared to some rural areas were the major suggested factors for early onset of puberty as compared to different study areas of Ethiopia.

The postpartum period of cows assessed in this study was lower than previous study of 32 which was 141 days. The mean+SE of calving interval of cows in this study was 12.88+0.046 months which was shorter than previous studies of 21.36±3.84 14, 13.4 ±5.1 months 41 and 14.64±2.2 2 in different study areas of Ethiopia. On the other hand the current finding was slightly longer than 12.4 months reported by 24. Age and parity of individual cows, as well as transition cows managements will bring difference in postpartum recovery period and further calving interval as well 31.The difference of calving interval might be due to poor heat detection skills of farmers, improper timing and techniques of breeding/service, season of insemination, breeding system, and milk yield level, nutrition and climate conditions may also affect the success of breeding/services that extend calving intervals 3651.

In the present study age of the cows significantly (P<0.05) affect conception to first service with high conception rate of 74.26% in animal age group of <4 years than older cows. This was fairly agreed with the result obtained by 29 and Mufti et al. (2010) who reported 77.8% and 72.73% respectively in similar age groups. The decline in fertility with advancing age might be due to a decrease in ovulation rate as a result of lack of gonadotropin release from the pituitary, a deterioration in the quality of eggs ovulated with subsequent fertilization, resulting in embryonic loss or uterine failure due to hormonal imbalance or deficiency 4711.

The rate of conception to first service was significantly (P=0.001) increased with parity number from 1-3. However, conception to the first service becomes decrease as parity increase to 4 and more which was decline from 51.35% to 25%. This is in agreement with 52 which was reported as an increased conception rate with advancing parity from 2 to 6, and then declined with more parities and 29 was reported increased conception rate significantly in both parity 2 and 3 (P≤ 0.05). The decreased conception rate in advanced parity of the cows might be due to the aforementioned factors related to age. Furthermore, an increase in parity brings reproductive problems and can also lead to serious locomotive, mammary and metabolic disorders 8.

In present study, the presence of reproductive health problems significantly affect first service to conception rate P=0.001. This might be due to the disturbance of metabolic and hormonal processes of the cow due to health problems. This problem is more prevalent when age and parity number of cows increasing that affect rate of conceptions as it was confirmed in this study. Age and parity of animals showed strong relationship with NSPC. An increase in age of animal in year cause increase NSPC significantly with odds of 1.39. Similarly, the NSPC increases as number of party increases with odds of 0.56. This was confirmed by the study of 1853 and 48 that reported an increase in age and parity of cows, and presence of reproductive problems affect conception rate to services and further increase number of services per-conception which resulted in calving-to-conception interval.

The NSPC in the present study was 1.69 for AI and 1.87 for NS. The NSPC in this study while using AI was lower than 1.95 ±0.41 28 and 2.1 ±1.3 30 while the NSPC with NS was higher than 1.7±0.9 30. Even nutritional status of animals mainly affect success in breeding, NSPC might be influenced by breeding system, estrous detection and time of insemination, environmental heat stress and health problems 50, as well as herd size, housing, level of production, age and parity 26. In the current study area, the major practices in selecting breeding method was primarily AI for genetic improvement and only animals with suspected different health problems and repeat breading were allowed for natural services. This makes higher average number of services for individual animals during natural services than AI.

In both natural services and AI, conception rate was increased with increase in number of services. This is disagreed with studies of 1042 who reported that cows that were artificially inseminated several times were found to be less likely to conceive than cows inseminated once. The current study was again supported by previous study of 40 who states that heifers and cows allocated to bulls for natural mating needed fewer services to conceive than those under AI. The difference in the current findings from previous studies might be due to limited number of bulls and high female to male ratio for natural services. In addition to this, general practices in use of natural services in the study area were done when female animals were suspected of certain reproductive problems and previous history of repeat breading.

There was no significant difference between breeding methods (AI and NS) on sex ratio of new born (P>0.05). However, slightly more female calves (53.17%) were born with NS and 51.47% with AI. This finding agreed with previous study of 6 who was found 55.4% female calves from NS and lower when AI used. It was different from the reports which states, there is a greater probability of male calves being born when conceived through AI 56746. This difference might be due to time of insemination with regard to estrous onset. In the present study area, AI was given early after onset of behavioral estrus that will give probability to have female newborn. Therefore, AI given early or late relative to time of ovulation changes sex ratio as late insemination gives chance to have male and early insemination to have female newborns. Sex ratio has no significant difference among study sites (sub-cities). However, slight difference in percentage might be due to overall management and breeding time difference.