Characterization and evaluation of reproductive performance in Bapedi sheep breed
Reproduction is an important field of animal production, as it ensures continuation and maintenance of different animal species and their production. Bapedi sheep are indigenous to South Africa and predominantly found in the Limpopo province. They are reared for lean meat production and as a source of income to resource limited farmers. However, there is limited documented information on the morphometric characteristics and reproductive performance of the breed. The objectives of this study were to (i) determine the relationship between Bapedi rams morphometric characteristics with semen parameters, (ii) evaluate the effect of age and body condition on oestrous synchronization response of Bapedi ewes, (iii) assess the conception, and lambing rate following synchronization and natural mating and (iv) validate the genetic structure of Bapedi sheep using microsatellite markers to relate to each farm’s reproductive performance. Body measurements and semen data were collected from 31 rams conserved in situ (Mara Research Station, Madzivhandila and Tompi Seleka Agricultural Colleges) and ex situ in vivo (Agricultural Research Council). Rams aged 1-5 years, grazing on natural pastures with free access to water and shade were used for semen collection by means of an electro-ejaculator. Parameters measured were body condition scores (BCS), frame size (FS), body weight (BW), scrotal circumference (SC), semen volume, semen pH, spermatozoa concentration (X109), motility (%), viability and morphology. Live weight was measured with an animal weighing scale, SC was measured with a flexible measuring tape, semen volume was measured using a graduated tubes (mL), semen pH was measured using a microprocessor pH/mV/°C, and spermatozoa concentration was measured with spectrophotomer (X109). Computer aided sperm analysis (CASA®) was used for analysis of spermatozoa motility rate. Spermatozoa morphology was determined using an eosin-nigrosin stain. Experiment 2; Ninety-one Bapedi ewes (aged <2 and 3-6 years) were synchronized for oestrous and the influence of age and BCS on the oestrous response of these ewes were measured, water was provided ad libitum. Ewes were assigned to (BCS) <3 and BCS≥3 on a scale of 1–5. For oestrous synchronization, controlled intravaginal drug release (CIDR®) dispensers were inserted for 9 days and 300 IU of equine chorionic gonadotrophin was injected intramuscularly after CIDR removal. Oestrus detection was done for a period of 72 h, from CIDRs withdrawal with a vasectomized ram. All ewes observed to be on heat were exposed to fertile rams for mating. Assessment of the genetic variation within and between Bapedi sheep was conducted using 14 microsatellite markers were used. Blood samples were collected from 174 unrelated Bapedi sheep in 6 farms in different districts of Limpopo and one conservation farm in Gauteng. Other South African sheep breeds such as Zulu, Damara, Dorper and Namaqua were included to assess the genetic relationship between these breeds and the Bapedi sheep as reference populations. There were no significant difference when the body weight of Bapedi rams was compared in all the farms (P>0.05). Moreover, there was uniformity in all body measurements of Bapedi sheep regardless of conservation method. There were no significant differences in body temperature during semen collection, SC, semen volume, pH, and concentration, sperm total motility and sperm kinematics in Bapedi rams in both methods of conservation (P>0.05). Pearson correlations revealed significant positive relationships between BW, BCS and SC (r = 0.315; r = 0.638; r = 0.381 respectively) with semen volume in Bapedi rams. Rump length was also found to positively influence sperm normality. There were no significant differences observed in oestrus response of ewes regardless of age (P>0.05) and method of conservation. Oestrus response was higher when ewes with BCS≥3 (91%) compared to lower BCS group (71%) (P< 0.05). Old and lower BCS ewes showed estrus signs earlier (23 ± 2.8; 21 ± 4.1); (22 ± 4.1; 20 ±5.3) and with a shorter duration (23 ± 8.2; 20 ±6.2); (22 ± 4.0; 23 ± 3.2) compared to young and ewes with higher BCS groups (onset of estrus: 34 ± 2.0; 32 ± 2.4); (36 ± 1.3; 35± 2.3) duration (30 ± 1.3; 29 ±1.5);(33 ± 5.0; 32 ± 6.0) (P<0.05). Conception rate was 65, 67, 53, and 70% for ARC, Towoomba, Tompi Seleka and Mara farms respectively. Toowoomba had a significantly lower litter size recorded compared to all the other farms. There were no significant difference (P<0.05) between the two conservation methods on the gestation length of Bapedi sheep. Prolificacy of Bapedi sheep was 1.30±0.6 1.28±1.3; 1.29±0.8 and 1.31±0.5 for ARC, Towoomba, Tompi Seleka and Mara farms respectively. To assess the genetic variation between and within populations the results obtained showed a mean number of alleles (MNA) to be 9, indicating that the panel of used markers were highly informative, however, no private alleles were obtained. Observed heterozygosity (Ho) and expected heterozygosity (He) values were ranged between (0,555±0.03 to 0,827± 0,027) and (0,754±0.02 to 0,883±0.004) respectively. These heterozygosities are indicative of a considerable genetic diversity among the Bapedi sheep populations. Within population inbreeding estimates (FIS =0,173±0,029) did not the influence heterozygosities obtained as it was high supported low rate of inbreeding, most likely as a result of the mating structure of Bapedi sheep. Both the unweighted pair group method with arithmetic mean (UPGMA) tree and Principal component analysis (PCA) results were in agreement and revealed that Bapedi sheep from Mopani commercial farm, Sekhukhune communal farm, ARC and Mara research station clustered together and share common genetic material. Towoomba population of Bapedi sheep did not cluster with the Bapedi sheep or any other reference population. Based on the findings it was concluded that Bapedi sheep are still a uniform breed, regardless of decreasing numbers. Higher oestrus was observed on ewes with BCS≥3. Young ewes with high BCS showed a delayed onset of estrus that lasted longer compared to old ewes with lower BCS. Conservation methods did not affect the reproductive performance of Bapedi sheep. It is recommended that BW, BCS and SC should be included in the selection of criteria to improve reproductive performance of breeding rams. Bapedi ewes can be synchronized successfully with an acceptable conception rate without supplementary feeding. Based on the currents results it was identified that there is a need for sustainable breeding and conservation programs to control inbreeding and gene flow of Bapedi sheep, in order to stop possible genetic dilution of Bapedi sheep. It is recommended that flush feeding should be considered to improve the fecundity and prolificacy of this breed. More research is required to assess correlation of body measurements, testicular morphometry and semen parameters in this breed.