Reproductive and productive performance of Dorper sheep and their crossbreds with local highland sheep at Debre Birhan agricultural research center, Ethiopia

S Goshme, S Besufekad, A Abebe, A Bisrat and A Abebe

Debre Birhan Agricultural Research Center, P O BOX 112, Debre Birhan, Ethiopia
shenkutegoshme@yahoo.com

Abstract

The study was conducted at Debre Birhan Agricultural Research Center, with the aim of evaluate the reproductive and productive performance of Dorper and its crossbred ewes and lambs. A total of 1304 ewes of pure Dorper and its crossbreds were considered. The experimental animals sucked their dams for 90 days, and then were separated from their mothers. After six months weight, females were joined to ram groups for mating and stayed in the flock for 3-5 years. Reproductive and live weight data were collected from pure Dorper and its crossbreds from 2014 to 2019/2020. The data were analyzed using general linear models. The lambing rate of F1 Dorper cross was higher than for pure Dorper and Menz ewes, which was about 85%. Lambing rate was higher during dry seasons. The age at the first lambing of Dorper ewes (570 days) was shortest than Dorper 50% F_2 and Dorper F1 first generation50%F_1 crossbred ewes. Dry season lambed ewes had higher AFL (990) days. The lambing interval of Dorper ewes (398) days was higher than Dorper 50%F_2 crossbreds ewes (331) days and dry season lambed ewes had slightly higher lambing interval than short and long rain seasons. The birth weight of Dorper (3.33kg) higher than Dorper 50% F_2 (2.84kg) and Dorper 50% F_1 (2.51kg) crossbred lambs. To minimize AFL and lambing interval as well as to increase lambing rate; flushing and mating should be taking during dry season to produce more lambs in short and long rain.

Key words: Dorper, Dorper 50% F1, Dorper 50% F2, season

Introduction

Ethiopia is home of about 31.30 million sheep, and meat production is the most important function of those animals in the country (Central Statistical Agency, 2019). The economic contribution of the livestock sub sector in Ethiopia is also about 12% of the total and 33% of agricultural gross domestic product, which provides livelihood for 65% of the human population (Central Statistical Agency 2019). Traditionally the sheep are selected for their adaptive traits, which compromised their productive and, reproductive functions under prevailing environment. However, available indigenous sheep breeds are unimproved, less productive and reared under traditional systems. The improvement within breed selection is a slow and tedious process and so, crossbreeding by using fast growing temperate sire lines has been suggested. However over the years many attempts of crossbreeding have not met the desired goal. In order to improve the productivity of native sheep breeds of the Central Highlands) of Ethiopia, exotic breeds such as Dorper were introduced since 2011 from South Africa. However, over the period of time several sheep breeds have been introduced in the country. Currently, nucleus stock of Dorper sheep are maintained at DBARC research center (Goshme et al 2020).

Reproductive performance is determinant in efficiency of sheep production so, crossbreeding is essential. Crossbreeding has proved to be a rapid way of increasing productivity by means of producing better combination of different traits than could get in one breed and optimizing heterosis or hybrid vigor. If crossbreeding is the mating plan chosen, one needs to have a good evaluation of the existing breeds to know, which breeds excel for specific traits. Using improved or better performance local dam breeds for crossbreeding is important for optimization of heterosis (Goshme et al 2014). About 14 sheep breeds are identified in Ethiopia and there is large amount of variation among breeds for economically important traits that can be exploited, in well-designed crossbreeding programs. Menz and Wollo ewe of small size and poor twining rate have been evaluated by crossing with Awassi rams (Gizaw & Getachew, 2009).

According to Tesfaye et al (2013), age at first lambing is affected by location/genotype combined, year and season. Age at first lambing for local ewes (472.7 days) was lower than the Awassi crossbred ewes (553.2 days) Wollo ewes had lower age at first lambing than ewes in Chacha (461.6 vs 501.4 days). Evaluation the performances of Awassi and Dorper crossbreds besides evaluating the performance of Menz sheep for traits such as yearling weight, survival and fertility related traits (Tesfaye et al 2013: Shenkute et al 2020). Over the years it has been observed that the fertility of the Awassi crossbred rams are lower when compared to their Menz counter parts. Awassi x local crossbred ewes had less productivity measurements than indigenous local ewes while the highest productivity improvement was obtained from Awassi cross rams x local ewes mating due to the combined effects of heavier body weights of crossbred lambs and shorter parturition intervals in small sized indigenous ewes (Gizaw & Getachew, 2009).

The performance of the crossbreds are even inferior (compared to the station) at the farmers end however, the fertility traits varied across locations (Getachew et al 2013). reproductive level observed for Awassi breed in Ethiopia are lower than those reported from the Middle eastern countries by (Ababneh et al, 2017: Mozo et al 2015) while the fertility of the rams of Menz breed raised at DBARC is significantly higher (Getachew et al 2013). The productivity of the farmers is much more dependent upon how well adapted and how productive the ewes are than the rams. It is the ewes more than the rams that determine the conception rate, how many lambs will be born, and whether the lambs get started off with a good milk supply. Increasing the number of lambs marked per ewe per year is major way to improve the efficiency of meat production in sheep. Evaluating the performance particularly, related to reproductive of different indigenous and exotic ewe breeds at each stage is essential. Reproductive performance is one of the main factors that determine the efficiency of sheep flock production in cool highland of north Shewa, Ethiopia in which sheep production is important activity.

The objective was to evaluate the reproductive and productive performance of Dorper and its crosses.

Materials and methods

Description of the study area

The study was conducted at Debre Birhan Agricultural Research Center (DBARC) in the cool highland of central northern of Ethiopia, which is located at 9^ᵒ 36’N latitude and 39^ᵒ 38’E longitude. The Center is located at 120 km northeast from Addis Ababa with the altitude of 2780 m above sea level and the mean annual rainfall of the area ranges from 781-1279 mm, and minimum, maximum and mean range temperatures of 7.3ᵒc, 23.7ᵒc and 2.21-28 ᵒC, respectively, and 60% relative humidity (Center data). The climate is characterized by bimodal rainfall consists of a long rain season (June-September), short rain season (February-May) and dry season (October-January) (Fekadu 2015).

Animals and management

A total of 1304 pure Dorper ewes and its crossbred were considered for the study. The ewes were flushed 21 days before joining to mating groups. The lambs sucked their dams for 90 days, and kept until six months of age. After six months weight females were separated from males and keep with ewes and the ram lambs also mixed with rams. Thus six months age ewe lambs were joined to ram groups for mating and staying for 3-5 years to know the age at first lambing, lambing interval, lambing rate, conception rate, and litter size. Animals were grazed in the day on natural pasture and supplement commercial concentrate and hay in the middle of the day and the night based on their body weight. Strategic deworming, vaccination and regular follow-up of treatments on cases were practiced in the flock.

Data collection

Reproductive and growth data were collected from pure Dorper and its crossbred staring from 2014-2019/2020. Data collection includes; pedigree, reproductive, growth (birth date, birth weight, weaning date, weaning weight, six month date, six month weight, yearling date, yearling weight) and postpartum weight. Age at the first lambing (AFL) was defined as the age of a female sheep giving birth in the first time; lambing interval= number of days between successive parturition Lambing rate = number of ewes kidded / number of ewes joined Conception rate =number of does conceived / number of does joined Litter size at birth = numbers of kids born per ewe per time.

Statistical Analysis

The effects of ewe breed group and seasons were determined for lambing interval, age at the first lambing, lambing rate, conception and litter size by using by the general linear model using SAS 9.0 program. The significance of fixed effects (ewe breeds, seasons and lamb breeds) was tested by least squares under Tukey’ HSD.

The model for lambing interval, age at the first lambing and lambing rate was as follows,

Y_ijm = µ + B_i + S_j + E_ijm

Y_ijm =Dependent variable

µ=Overall mean

B_i= Effect of i^th ewe breed ( Dorper, Dorper 50% F_1,Dorper 50%F_2 and Menz)

S_j= Effect of j^th seasons (Dry, short and long rain)

E_ijm= Residual error

The statistical model used for body weight analysis was,

Y_ijmk= µ + B_i + S_j + Wm + Qk+ E_ijmk

Y_ijmk =Dependent variable

µ=Overall mean

B_i=Effect of i^th lamb breeds (Dorper, Dorper 50% F_1, Dorper 50%F_2)

S_j= Effect of j^th seasons (Dry, short and long rain)

Wm=Effect of m^th birth type (twin and single)

Qk= Effect of k^th sex (male and femal)

E_ijkm= Residual error

Results

Lambing rate of different ewe breeds

Least square means of ewe breeds and seasons on lambing rate are presented in table1. There was a significant differences (p<0.001) in lambing rate of different ewe breeds and breeding seasons. Dorper 50% cross ewes had higher lambing rate (p<0.001) than Dorper and Menz ewe breeds. Dorper and Menz ewe breeds had lower lambing rate and there were no differences in lambing rate of Dorper and Menz ewe breeds. There were significant differences (p<0.001) in lambing rate across different seasons. Dry seasons had higher lambing rate (p<0.001) than long and short rain seasons. The short and long rain seasons had lower lambing rate and there were no significant differences.

Age at the first lambing (AFL) of different ewe breeds

Least square means of ewe breeds and seasons on age at the first lambing are presented in table2. There was a significant differences (p<0.001) in age at the first lambing of different ewe genotypes and breeding seasons. Dorper 50% F_2 cross ewes had higher age at the first lambing (p<0.001) than Dorper and Dorper 50% F_1 ewe genotypes. Dorper ewe breed had lower age at the first lambing. Dorper 50% F_1 ewe genotypes had higher age at the first lambing when comparing with Dorper ewes. There were significant differences (p<0.001) in age at the first lambing across different seasons. Dry seasons had higher lambing rate (p<0.001) than long and short rain seasons. The short and long rain seasons had lower age at the first lambing and there were no significant differences.

Lambing interval of different ewe breeds

Least square means of ewe breeds and seasons on lambing interval are presented in table3. There was a significant differences (p<0.001) in lambing interval of different ewe genotypes and breeding seasons. Dorper ewes had higher lambing interval (p<0.001) than Dorper 50% F_2 and Dorper 50% F_1 ewe genotypes. Dorper 50% F_2 ewe breed had lower lambing interval. There were no differences in lambing interval of Dorper 50% F_1 and Dorper 50% F_2 ewe genotypes. Dorper and Dorper 50% F-1 cross breed ewes had no difference in lambing interval. There was significant differences (p>0.001) in lambing interval across different seasons. Among the seasons dry season had relatively higher lambing interval than long and short rain seasons. The short and long rain seasons had lower lambing interval.

Birth weight of different lamb breeds

Least square means of ewe breeds and seasons on growth performance of different lamb breeds are presented in table4. There was a significant differences (p<0.001) in body weight of different lamb breeds and birth seasons. Dorper lambs had higher birth weight (p<0.001) than Dorper 50% F_2 and Dorper 50% F_1 lambs. Dorper 50% F_1 lambs had lower birth weight when comparing with Dorper and Dorper 50% F_2 lambs. There were significant differences (p<0.001) in birth weight across different seasons. Dry and long rain seasons had higher birth weight (p<0.001) short rain seasons. There were a significant difference (p<0.001) in birth weight of single and twin birth type. Single birth type had higher birth weight than twins. There was no significant difference in lamb sex on birth weight.

Discussion

The results in the study indicated that the lambing rate of ewes varied by genotypes of ewes which can be attributed to many factors the genetic variation as well as the seasonal nature of the breeding seasons (Goshme et al 2020: Afolayan et al 2014). The difference in lambing rate of ewe breeds which can be ascribed to several factors. Among these factors mating of the same genotype is the main factors which influence lambing rate. The current finding showed that the lambing rate of Dorper 50% cross was higher than Dorper and Menz ewes which were about 85% ewes were lambed. The current result comparable with (Horn, 2014: Schoeman & Burger, 1992) the lambing rate of Dorper 84% and 85% ewes were lambed while the current finding on Dorper was lower than the finding of (Dinu & Cziszter, 2015: Schoeman & Burger, 1992) on Dorper ewes lambing rate at South Africa. According to (Goshme et al 2020: Dinu & Cziszter, 2015) lambing rate of ewes influenced by breed, age and seasons these due to the fact that the interaction effects of environment and gene. The current result is in contrary with the find of (Dinu & Cziszter, 2015) which most of laming were during short rain while the current results showed most lambing were during dry seasons. The current finding showed that dry season had higher lambing rate than the short and long rain seasons which can be ascribed to the mating season of the ewes were during long rain seasons. Feed availability is influencing by seasons as a natural mating underway. Most ewes are coming to estrus when the natural grazing land is good during rainy seasons(Schoeman & Burger, 1992). According to (Dinu & Cziszter, 2015) ewes had higher conception rate during rainy seasons which can be due to the fact that grazing land had better standing grass during rainy seasons. According to (Afolayan et al 2014: Moghaddam et al., 2012) lambing rate in ewes is influenced by numerous factors; these factors encompass genetic potential nutritional status, environmental factors, day length, health status and other factors. According to (Getachew et al 2013) local ewes had better lambing rate than Awassi x local crossbred ewes in different locations.

The results in the study indicated that the age at the first lambing of ewes varied by genotypes of ewes seasons which can be attributed to many factors the genetic variation as well as the seasonal nature of the breeding seasons (Getachew et al 2013: Afolayan et al 2014). The difference in age at the first lambing of ewe breeds which can be ascribed to several factors. Among the factors, genetic potential nutritional status, environmental factors, day length, health status and other factors are the main factors which influencing age at the first lambing. According to (Getachew et al 2013) age at the first lambing is affected by ewe breeds and age at the first lambing for Awassi crossbred ewes were (553.2) days which lower than the current result age at the first lambing of Dorper (570) days and higher than local ewes (472.7) days. The current finding showed that age at the first lambing of Dorper ewes (570) days were in agreement with age at the first lambing of Dorper ewes (588) days by (Schoeman & Burger, 1992) and age at the first lambing of Dorper ewes (346) by (Dinu & Cziszter, 2015). The current finding on Dorper 50% F_2 and Dorper 50%F_1 crossbred ewes had higher age at the first lambing compare with Dorper ewes which were in agreement with (Schoeman & Burger, 1992,Dinu & Cziszter, 2015) on age at the first lambing of Dorper ewes. The current study showed that age at the first lambing was influenced by seasons and dry season lambed ewes had higher age at the first lambing (990) days comparing short rain (676) days and long rain (653) days seasons lambed ewes. According to (Mozo et al., 2015,Dinu & Cziszter, 2015) seasons had a significant influence of age at the first lambing.

The result of the current study indicated that the lambing interval of ewes varied across genotypes of ewes’ and birth seasons which can be attributed to many factors the genetic variation as well as the seasonal nature of the breeding seasons. Thus several factors include genetic potential nutritional status, environmental factors, day length, health status and other factors. According to (Getachew et al 2013) lambing interval was significantly affected by location/genotype combined level, year of birth, season of lambing and parity of ewes. The lambing interval of Dorper ewes (398) days was higher than Dorper 50%F_2 crossbreds ewes (331) days which was in contrary with (Getachew et al 2013) lambing interval of local ewes (247.6) days and lambing interval of Awassi crossbred ewes (286.3) days in on-farm study. The current finding showed that the lambing interval of three ewes genotypes (Dorper, Dorper 50% F_1, Dorper 50% F_2) higher than the finding of (Getachew et al 2013) lambing interval of local and Awassi crossbred ewes. The current finding showed that lambing interval was slightly influenced by seasons and dry season ewes lambed was higher lambing interval.

The current finding showed that birth weight was affected by lamb breeds and lambing seasons. Least square mean of birth weight of Dorper (3.33kg) higher than least square mean of birth weight of Dorper 50% F_2 (2.84kg) and Dorper 50% F_1 (2.51kg) crossbred lambs. Type of birth made the biggest contribution in birth weight of lambs. Singles were heavier than twins with an average of (3.1kg) and (2.68kg) respectively. The current result showed that birth weight of Dorper lambs and its crossbred lambs were lower than birth weight of Dorper lambs (3.8kg) by (Csizmar et al., 2013) and birth weight of Dorper lambs (4.1kg) by (Schoeman & Burger, 1992). Sex did not affect birth weight of lambs and average birth weight of male lambs was (2.95kg) while birth weight of female lambs was (2.83kg). The study obtained by (Csizmar et al., 2013) birth weight of male lambs were 4.36kg while female lambs 3.54kg which were higher in comparisons with the current finding. Similar findings (Csizmar et al., 2013) and (Dinu & Cziszter, 2015) support the current finding sex did not affect the birth weight of lambs. Birth weight of lambs were influenced by seasons and dry season lambed had higher birth weight in comparisons with short and long rain seasons.

Conclusion

• The lambing rate of Dorper 50% cross was higher than Dorper and Menz ewes,
  
  
• Lambing rate of ewes were higher during dry seasons,
  
  
• The age at the first lambing of Dorper ewes (570) days was shortest than Dorper 50% F_2 and Dorper 50%F_1 crossbred ewes.
  
  
• The age at the first lambing was influenced by seasons and dry season lambed ewes had higher age at the first lambing (990) days comparing short rain (676) days and long rain (653) days seasons lambed ewes.
  
  
• The lambing interval of Dorper ewes (398) days was higher than Dorper 50%F_2 crossbreds ewes (331) days.
  
  
• The lambing interval of ewes was slightly influenced by seasons and dry season ewes lambed was higher lambing interval than short and long rain seasons.
  
  
• The birth weight of Dorper (3.33kg) higher than the birth weight of Dorper 50% F_2 (2.84kg) and Dorper 50% F_1 (2.51kg) crossbred lambs.
  
  
• Singles birth was heavier than twins with an average of weight of (3.1kg) and (2.68kg) respectively.

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