Reproductive performance of crossbred dairy cows in Eastern Lowlands of Ethiopia

Emebet Mureda and Zeleke Mekuriaw Zeleke*

Agricultural College, ATVET, Holleta, Ethiopia
*Bair Dar University, P.O.Box 1866, Bahir Dar, Ethiopia
Zeleke_Mekuriaw@yahoo.co.uk

Abstract

A study was conducted to assess reproductive performances of 304 crossbred (Holstein Friesian x Zebu) dairy cows kept in small (SSDP), medium (MSDP) and large scale dairy production (LSDP) systems in Eastern lowland of Ethiopia.

The overall mean age at first service (AFS) and at first calving (AFC) across all production systems were 25.6 (n=283) and 36.2 (n=210) months, respectively. The AFS and AFC were significantly longer (P≤0.05) in the MSDP than in the SSDP and LSDP systems. The overall mean intervals from calving to first service (CFSI) and from calving to conception (CCI) were 162.5 (n=149) and 218.5 (n=108) days, respectively. The crossbred cows under SSDP management system had shorter (P≤0.05) CFSI and CCI than those managed under MSDP and LSDP. The CFSI and CCI were the longest (P≤0.05) for the first and beyond 6^th parities as compared to 2^nd, 3^rd and 4^th parities. The mean calving interval (CI) across all production systems was 17.8 (n=155) months. Cows managed under SSDP system had significantly shorter (P≤0.05) CI as compared to cows managed under MSDP and LSDP. The overall pregnancy, calving and conception to first service rates were 72.8%, 63.4% and 45.9%, respectively with no significant difference (P≥ 0.05) among production systems.

In conclusion, crossbred cows under the SSDP management systems had better reproductive performance followed by cows in LSDP. Developing feed resource, effective reproductive health management and reliable AI service could be management options to mitigate some of the prevailing problems.

Key words: crossbred cows, production system, reproduction

Introduction

Ethiopia is known for its huge cattle population. However, the country’s per capita milk consumption is estimated to be about 19.2kg per year, which is far below the average per capita consumption of Africa, 37.2kg per year (FAO 2000). This low per capita milk consumption is mainly emanated from poor genetic potential of local cattle for dairy traits. Accordingly, enormous efforts have been made to improve the genetic potential of local cattle through cross breeding with exotic breeds, mainly Holstein Friesian. Even though milk yields of crossbreds are believed to be higher than that of local zebu, the reproductive performances of the crossbreds under prevailing local conditions of hot lowland areas of Ethiopia was not documented. Thus, the current study was initiated to assess reproductive performances of crossbred (Holstein Friesian X Zebu) cattle kept in hot lowland part of Eastern Ethiopia under different production systems.
 

Materials and methods

The study was conducted in Dire-Dawa administrative Region located in eastern part of Ethiopia between 9⁰27'E and 49'N latitude and 41⁰38' N and 19'E longitude occupying about 133,000ha of land. The area comprises of diversified topography features with altitude varying from 950 masl in the Northeast lowlands to 2,260 masl in the Southeast highlands (DDACADO 1998). The study area has a bimodal rainfall with the mean annual rainfall varying from 550 mm in the Northern lowlands to about 850 mm in the Southern mountains. The short rainy season is from April to May whereas the main rainy season is from July to September. The mean monthly maximum and minimum temperatures are 28.1 and 14.5⁰C (DDACAO 1998). Short-cycle annuals dominate the herbaceous layer, however, there are also perennials among which acacia is dominant and provides dry-season forage.

A cross-sectional survey was carried out across the farms and then pre-designed structured questionnaires were developed, tested and administered to farm owners and attendants of all farms considered for the study. The farms were categorised into defined strata based on herd size. These were small scale dairy production (SSDP), medium scale dairy production (MSDP) and large scale dairy production (LSDP) having 5 or less, 6 to 30 and 72 to 171 dairy cattle, respectively. The number of herds under SSDP, MSDP and LSDP were 33, 21 and 3, respectively. Regardless of the production system, animals were stall fed. Animals in SSDP system depend more on non-conventional feeds such as local brewery byproduct, crop residues, household waste and backyard grown forages, whereas in MSDP and LSDP systems, animals entirely depend on crop-resides and agro-industrial byproducts (wheat bran, brewery by product). Regardless of the production system, all cows were milked by hand twice daily (morning and evening). The mating system used across all production systems was AI.

Purposive sampling method was then employed to select study farms that possessed crossbred dairy cows, kept individual cow reproductive history and willing to be part of the study. In addition to interview, farm records were used to calculate age at first service, age at first calving, calving intervals, days open, pregnancy rate, conception rate to first service and number of services per conception. For analytical purpose, cows were categorized into four parity groups, i.e., group one (cows in first parity), group two (cows in the 2^nd and 3^rd parity) and group three (cow in 4^th & 5^th parity) and group four (cow in 6^th parity and beyond).

The effects of production systems and parity group on AFS, AFC, CFSI, CCI, CI and number of services per conception (NSC) were analyzed using General Linear Procedures (SAS 1999). Pregnancy and calving rates and conception to first service were analyzed using the categorical modeling (CATMOD) procedures of SAS.
 

Results and discussion

Age at first service and Age at first calving

The least square means (± SE) of AFS and AFC for the SSDP, MSDP and LSDP systems are summarized in Table 1.

The overall mean for AFS and AFC across all systems was 25.6 months (n=283) and 36.2 months (n=210), respectively. These overall mean values for AFS and AFC obtained in this study were within the range reported by many authors on exotic and indigenous crosses. Estimates for AFC in Ethiopian cattle were reported to be longer for Zebu (Mekonnen and Goshu 1987; Mukasa-Mugerwa 1989) than for crossbreds (Alberro 1983; Mekonnen and Goshu 1987). Similarly, in the work done in the central high lands and in Addis Ababa milk shed, the overall means for AFS and AFC were found to be 29.6 and 40.6 months (Yoseph et al 2003) and 20.1 and 29.0 months (Yoseph 1999), respectively. Kiwuwa et al (1983) reported mean AFC of 33.8 months with a range of 31.3 to 35.7 months for crosses of Friesian and Jersey sire breed with Zebu dams in the Arsi region of Ethiopia.

Different factors advance or delay AFS and AFC. Environmental factors, especially nutrition, determine pre-pubertal growth rates, reproductive organ development, and onset of puberty and subsequent fertility. Substantial evidence exists that dietary supplementation of heifers during their growth will reduce the interval from birth to first services and calving (Kayongo-Male et al1982; Azage 1989), probably because heifers that grow faster cycle earlier and express overt estrus.

The AFS for crossbred cows under MSDP was the longest (p≤ 0.05) as compared to SSDP and LSDP Systems. It was extended by 2.7 and 3.3 months as compared to AFS of cows kept under LSDP and SSDP systems. However, there was no significant difference (p > 0.05) in the AFS between LSDP and SSDP systems.

Similarly, the AFC under MSDP was significantly longer (p≤0.05) when compared with the other two systems. It was delayed by 3.3 and 3.3 months from SSDP and LSDP systems. There was no significant difference (p> 0.05) in AFC between SSDP and LSDP systems. The significant variations in AFS and AFC between MSDP and the rest two production systems is probably due to the difference in management and feeding systems. The SSDP keep only few animals that are affordable for proper feeding and closer management. The LSDP have also good management and feeding practices as they are fully engaged in the dairy business. The LSDP considered in this study had full or part time veterinary or animal science professional employees. On the other hand, MSDP had relatively inadequate management and feeding practices. This was probably due to the fact that they were neither fully engaged in the business nor had few dairy animals to manage well.

Intervals from calving to first service and calving to conception

The overall mean value for CFSI was 162.5 (n=149) days (Table 1). The CFSI was significantly different (P≤0.05) among cows managed under SSDP, MSDP and LSDP systems. The cows under SSDP had the shortest CFSI when compared with cows in MSDP and LSDP. There was no significant difference (P>0.05) in CFSI of cows maintained in MSDP and LSDP systems.

The overall mean value for CCI across all production systems was 218.5 days (n=108). Again, crossbred cows under SSDP had shorter (p≤ 0.05) CCI than those in LSDP and MSDP. The difference in intervals between LSDP and MSDP was not significant (p> 0.05).

Parity of cows also imparted significant (p≤0.05) effects on CFSI and CCI. The CFSI and CCI were the longest (p≤ 0.05) for parity group four (6^th and beyond parity) followed by parity group one (1^st parity) as compared to parity group two (parity 2+3) and parity group three (parity 4 + 5). Least square means (± SE) of CFSI for parity group one, two, three and four were 156.2 ± 8.8, 135.3 ± 9.8, 154.1 ± 10.9 and 242.5 ± 13.5 days, respectively and CCI for the same groups were 202.3 ± 15.3, 185.9 ± 16.7, 210.8 ± 17.3 and 343.7 ± 23.6 days, respectively. Dairy cows categorized in parity group two had lower CFSI and CCI. The values for parity group four were significantly higher (p≤0.05) when compared with the other parity groups. Causes of this parity related differences on CFSI and CCI could be lactation stress in young growing cows (parity one) and the ability of mid parity cows (parity group two and three) to gain body weight and condition quicker post calving. On the other hand, mature cows delay in gaining weight and perhaps as they get older the probability of being exposed to reproductive disorders may also increase.

Controversial values are reported in the literature. Tesfu et al (1993) who worked on crossbred cows and Zebu in the central highlands of Ethiopia reported mean values for both CFSI and CCI of 110.4 and 199.8 days for Zebu and 97.5 and 157.8 days for crossbred cows, respectively. The overall mean CFSI and open days for crossbred cows in large peri-urban and intra urban dairy farms in Addis Ababa area was estimated to be 88 and 124 days, respectively (Yoseph 1999). Whereas, in West Shewa zone, the mean value reported for CFSI and CCI were 141.9 and 185.0 days (Yoseph et al 2003). Similarly, estimates of CFSI and days open have been reported to range between 130 to 300 days in Zebu and crossbred cows under management conditions of research centers in Ethiopia (Azage et al1981).

Like elsewhere in the tropics, in Dire-Dawa Administrative Region, several factors could contribute to these long CFSI and CCI as compared to central highland dairy production of Ethiopia where there is relatively better feed resources and optimum ambient temperature. According to personal observation, animals experience year round nutritional deficiencies and some how heat stress in the study area. Most of dairy operations were intensive and had no pasture or grazing field of their own. Moreover, there were limited or no pasture producing areas in Dire-Dawa Administrative Region and its vicinity. Hence SSDP tend to rely more heavily on non-conventional feeds and MSDP and LSDP tend to rely on crop residue and industrial byproducts. Nutritional deficiencies coupled with heat stress probably might have contributed to the long CFSI and CCI.

Number of services per conception

The overall mean value of NSC was 2.16 (n=108). Similar estimates were reported by other investigators in Ethiopia for crossbred cows, all in the range of 1.5 to 2.5 (Beyene 1992; Yoseph 1999; Yoseph et al 2003).The NSC was not significantly different (p > 0.05) among the production systems (Table 1) but significantly different (P≤0.05) among parity groups (Table 2).

Dairy cows categorized in parity group four (parity 6 and beyond) required significantly higher (p ≤0.05) NSC as compared to cows categorized in the other parity groups. Though there was no statistically significant difference in the NSC, fewer NSC was recorded in SSDP system as compared to other production systems. This may be due to ease of close supervision and better heat detection by owners as the herd size is manageable. In fact, the overall mean NSC was found to be higher when compared with other the NSC in modern dairy farms elsewhere which may be due to poor heat detection, less availability of AI service or bull, quality and timing of insemination and environmental stress. Frequent complaint of farmers in study area was returning to estrus of cows after long time of insemination which implies likely occurrence of embryonic mortality.

Calving interval

The estimates of CI for SSDP, MSDP and LSDP are presented in Table 2. The overall mean value of the CI was 17.8 months (n=155). The respective values for each production system were 16.2 ± 0.7, 18.3 ± 0.5 and 18.1 ± 0.4 months, respectively. The CI of cows in SSDP was significantly lower (p ≤0.05) as compared to the other two production systems. There was no significant difference in the CI between MSDP and LSDP systems. The parity of cows significantly affected (P≤0.05) the CI (Table 3). The CI was found to be significantly longer (P≤0.05) in cows beyond fifth party as compared to the rest parity groups.

Results obtained in the present study are in agreement with earlier reports. Kiwuwa et al (1983) reported the mean CI for crossbred cattle in the Arsi region of Ethiopia to be 15.1 ± 0.1 months. Similarly, Mekonnen and Goshu (1987) found overall mean CI of 16.7 ± 0.5 months for Fogera breed of Ethiopia and their crosses. Factors such as the age of cows, breed, year of calving and forage availability in any particular year are important considerations to bear in mind.

Generally, the variation in reproductive performance among SSDP, MSDP and LSDP may be due to management effects, including nutrition and health conditions. Several factors, which could not be explicitly indicated in this study, might have contributed to extend CI as compared to central highland dairy productions where there is relatively better feed resources and cooler ambient temperature. Dairy cattle in Dire-Dawa Administrative Region, generally, were known to experience year round nutritional deficiencies. On top of that because of high ambient temperature, there might have been heat stress that may have negative effect on reproductive performance. Crossbred cows under the SSDP system performed better which could be due to better nutrition since animals under the SSDP usually were fed well than in the other production systems, as they tend to rely more on non-conventional feeds.

Pregnancy, conception to first service and calving rates

Pregnancy, conception to first service and calving rates for each production systems are summarized in Table 3. The conception to first service, pregnancy and calving rates across all production systems were 72.8%, 45.9%, 63.4%, respectively with no significant difference.

Different authors reported variable figures regarding pregnancy, conception to first service and calving rates. For instance, Geleto (1991) found out pregnancy rate of 62% by 120 days postpartum, and 68% by 150 days in Boran cows at ILRI Debre Zeit Research Station, Ethiopia. Galal et al (1981) also reported calving rates of 70%, 75% and 85% for local cows in dry, wet and humid region research stations, respectively. Yoseph et al (2003) working on crossbred cows in West Shewa reported the overall pregnancy rate of 79.3%. The conception rate to first services of Horo and Borana crosses with Bos taurus breed at the Bako and Holetta Research Centers, Ethiopia, was estimated to be 41 to 45% (Yoseph et al 2003). Body condition of animal at the time of insemination or natural mating is known to affect conception rate. Pregnancy rates for Boran cows that calved during the dry season and had poor body condition ranged between 22 and 46% (Azage 1989). By providing supplements in the dry season (1.5 kg per head per day of noug cake and wheat bran mixture), the pregnancy rates of Boran and Boran x Friesian heifers increased by 15% (Azage 1989). In general, low fertility rates of cattle in the tropics compared to temperate regions are probably related to environmental differences including inadequate nutrition, prevalence of diseases and parasites as well as the interaction between genotype and environment (Mukasa-Mugerwa 1989).
 

Conclusion

• Relatively better reproductive performances of crossbred cows in SSDP as compared to MSDP and LSDP systems implies the necessity of improving feed resource and herd management capability of the owners prior to expanding herd size. 
   

References

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Yoseph S, Tenhagen  B A, Merga B  and  Tesfu  K  2003 Reproductive performance of crossbred dairy cows managed under different production systems in central highlands of Ethiopia. Journal of Tropical Animal Health and Production, 35 (6): 551-561

Received 27 February 2007; Accepted 1 April 2007; Published 1 November 2007

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