Longevity traits of Shami and Holstein Cows in Syria

This research aimed to study the effect of age at rst calving (AFC) and rst lactation milk yield (FLMY) on the longevity traits of Shami and Holstein cows under the Syrian environment and estimate longevity traits for both breeds. The complete records from birth to voluntary culling were collected for 569 Shami cows and 1699 Holstein cows during the period from 1982 to 2014 at two experimental stations, Ministry of Agriculture and Land Reclamation, Syria. Data were analyzed using the General Linear Model (XLSTAT, 2020). The least square means of lifespan (LS), productive life (PL), a number of calvings (NC), lifetime milk production (LMP), and lifetime daily milk production (LDMP) were 93.7±0.14 months, 63.2±34 months, 4.2±0.14, 7683±0.14 kg, 2.6±0.14 kg for Shami cows, respectively. The corresponding values for Holstein cows were: 61.9±0.14 months, 31.6±34 months, 2.6±0.14, 10246±0.14 kg, 4.4±0.14 kg, respectively. The effect of AFC was signicant on all studied traits except LS trait. Whereas, FLMY effect was signicant only on LMP and LDMP traits. It was concluded that Shami cows had longer LS, PL, NC traits than Holstein ones, but their LMP and DLMY were lower. Reduction of AFC for Shami and Holstein cows to less than or equals to 25 months could be a proper management policy to improve each of PL, NC, LMP and LDMY. FLMY was found as an indicator for LMP and LDMY of Shami and Holstein cows.


Introduction
Cattle play an important role in meeting the people's demand for milk and meat in Syria. During the last decades, the number of imported Holstein and crossbred cows in Syria increased and the number of local cows reduced, especially Shami cows. According to the Annual Agricultural Statistical Group (2010), the total cattle population in Syria was estimated as about one million heads and produced about 66% of the total milk consumed. However, the total number of Shami cows was 964 heads, representing about 0.1 % of the total cattle population in Syria.
Shami cows have been known as a distinct and important breed for 500 years ago or more. Mature cows were of medium size 484 kg. Shami cows showed a high genetic potential for milk yield and appeared to be the most highly developed milk producing local animal in the middle east (Brown, 1964). Alawa (1965) reported that Shami cows are characterized by their good adaptation with local environmental conditions, and their resistance to Brucella and foot and mouth diseases, and its reduced incidence of reproductive problems such as placental retention, uterine infection and lethargy of the ovaries, and they can give birth every year. AL-Dakkak (2008) indicated that sexual maturity in the heifers of Shami cows occurs at the age of 13.33 months and weight of 250 kg.
In general, the indigenous breeds are lower in milk and meat production compared to the Holstein breed (Belay et al., 2012). However, local breeds are not only important for the conservation of genetic diversity, but also for increasing the income of small farmers, because of their long lifespan and adaptation with harsh environmental conditions (Jonkus et al., 2020).
Holstein cows had lower 40-60% milk production under tropical and subtropical environments compared to temperate conditions, this is due to the exposure of Holstein cows to the different stress factors in the adverse environments (Mekonnen et al., 2020).
The lifespan and productive life of cows are complex and essential traits for selection and genetic improvement (Kamaldinov et al., 2021), therefore, increasing productive life leads to achieving higher economic return from cows through reducing herd replacement costs and increasing both numbers of calvings and lifetime milk yield (Dallago et al., 2021).
Age at rst calving (AFC) is one of the crucial factors in determining the economic income because AFC declares the beginning of a cow's productive life and it is in uenced by a lot of factors such as breed, management systems, and cow health (Wu et al., 2012).
First lactation milk yield (FLMY) might re ect the production capacity in subsequent lactations of cows.
Dairy cows that yielded greater FLMY may suffer from health problems which may lead to the early culling from the herd (Janus and Borkowska, 2004). Therefore, the main objectives of this research were 1) to study the effect of AFC and FLMY on the longevity traits of Shami and Holstein cows with considering other environmental factors, and 2) to compare the longevity traits between both breeds under the Syrian conditions.

Data collection
Data used in the present study were collected from two Syrian farms and covered 33 years .
The rst set of data was 569 complete records of Shami cows belonging to the Deir al Hajar station. The second set of data contained 1699 complete records of Holstein cows and belonging to the Fedio station.
Each record contained the data of age at rst calving, rst lactation milk yield, lifespan, productive life, lifetime milk production, lifetime daily milk production and the number of calvings for each cow under study.

Herd management
Animals in the two farms were kept under almost the same management systems. Cows were kept under a free housing system in semi-closed sheds.
Cows were fed commercial concentrates, hay and fresh fodders whenever available. Roughages were provided to the cows twice a day.
Water was available all the time. On the rst farm, Shami heifers have naturally inseminated for the rst time at 18 months of age taking into account the weight of the heifer. On the second farm, Holstein heifers have arti cially inseminated when they reached 13-15 months of age taking into account the heifer weight. All cows in the two farms were machine milked twice daily. Recording of milk yield was conducted twice monthly to calculate the monthly and aggregated total milk production for each cow. Holstein cows were dried for about 60 days before calving, while Shami cows were dried spontaneously.
Pregnancy was detected in both breeds by rectal palpation. Cows underwent a regular vaccination program speci ed by the Animal Health Directorate at the Ministry of Agriculture and Land Reclamation, Syria. summer and 4= autumn, and e ijklmn = the random error assumed N I D (0, s 2 e).
The interactions among all factors studied were not signi cant, so we excluded the interactions from the statistical analysis model. To quantify the relationships between AFC and FLMY with the studied traits, simple correlation coe cients were estimated using the XLSTAT 2020.3.1.27 software.

1-Lifespan (LS)
Least squares means and standard errors of means for the studied traits are shown in tables (1) and (2).
The results of  (2020) reported that Holstein cows calved for the rst time at less than 24 months had the littlest LS (6.11 years), and the cows calved for the rst time between 34-36 months had the longest LS (7.36 years) in Bulgaria. The authors explained that inappropriate nutrition of young heifers leads to insu cient body development for conception at an earlier age (14-15 months).
The LS wasn't affected signi cantly by the rst lactation milk yield (FLMY) ( Table 1). This is in agreement with Brzozowski et al. (2003) on Polish cows. Otherwise, Jankowska et al. (2014) in Poland demonstrated that Holstein Friesian cows produced from 5000 to 10000 kg in the rst lactation had a higher LS (5.25 years) compared to 4.95 and 4.43 years of cows produced milk in the rst lactation less than 5000 kg and more than 10000 kg, respectively. They explained that cows that produced high milk had fertility problems, so they were culled early and their lifespan was short. The effect of the season of rst calving on LS was not signi cant (Table 1). This may be attributed to the resemblance of feedstuffs in their quality and quantity as well as may be due to the uniform management practices between different seasons. This result is in accordance with Salem and Hammoud (2019) of Friesian cows in Egypt.  (2021) reported that the PL of Chinese Holstein cows was short (27 months). The authors attributed that to many reasons such as a downtrend of genetic merit on longevity traits, no direct selection for longevity and, the intensive selection for milk yield traits that had negative genetic correlations with the longevity traits.
The effect of AFC on PL was highly signi cant (p< 0.01). The PL was decreased with progressing AFC. Cows calved at less than or equal 25.4 months had the longest PL (55.5 months), while the cows calved lately (more than or equal 34.8 months) had the shortest PL (39.6 months) (Table 1). This is because of cows that calved at early age began their productive life earlier which resulting in longer their productive life than cows that calved lately. Moreover, it might be attributed to that, cows with older ages at rst calving a icted from a reduction in fertility performance and less milk yield, and therefore, they have more susceptible to culling and have a shorter productive life (Nilforooshan and Edriss, 2004). The current nding agrees with Kučević et al. (2020) on Holstein cows in Serbia. On the other side, Adamczyk et al. (2017) reported that the PL of cows that calved before 24 months at the rst time had a lower PL (5.4 years) than those calved at more than 31 months (5.9 years) in Holstein-Friesian cows. Valchev et al. (2020) reported that Holstein cows in Bulgaria calved for the rst time at less than 24 months or more than 37 months, had the littlest PL (4.03 and 3.9 months, respectively) while cows calved for the rst time between 28 and 30 months had the greatest PL (4.84 months). The authors explained that heifers at this age have mature and healthy bodies for life.
The effect of the FLMY on the PL was not signi cant (Table 1). This result agreed with the nding of Brzozowski et al. (2003) on Polish cows. On the contrary, Januś and Borkowska (2012) pointed out that increasing milk yield in the rst lactation led to reducing the PL of Holstein Friesian cows in Poland. The authors attributed that to the negative correlation between milk production and fertility traits, so cows that produced high milk production at rst lactation suffered from reproductive problems and culled early.
The effect of the year of calving on PL was highly signi cant (p< 0.01). The longest PL was 53.7 months for cows calved during the period from 1982 to 1990 and the shortest one was 36.1 months for cows calved during the period from 2006 to 2014. This may be due to differences in management conditions over years. Singh et al. (2018) obtained the same results on crossbred Frieswal cows (Friesian × Sahiwal) in India.
The PL was not affected signi cantly by the season of the rst calving (Table 1), which is in accordance with Kučević et al. (2020) on Holstein cows in Serbia.  .7), because of the negative genetic correlations between the longevity parameters and milk production of Chinese Holstein cows.

3-Number of calvings (NC)
AFC affected signi cantly the NC (p<0.01). It was to be reduced with increasing age at rst calving. The highest value of NC (3.9 calvings) was for cows calved at less than or equal to 25.4 months for the rst time, and the lowest value (3 calvings) was found for cows calved at more than or equal to 34.8 months for the rst time (Table 1). This is because of cows that delivered at lower AFC had longer PL and consequently more NC than cows that calved lately. Similar results were found by Eastham et al., (2018) and Sawa et al. (2018) on Holstein Friesian cows in UK and Poland, respectively. The authors found that the reduction of age at rst calving had a positive impact on reproductive performance which resulting in more NC throughout the productive life.
The effect of FLMY on the NC was not signi cant (Table 1). This result was consistent with Sawa and Krezel-Czopek (2009) in Polish Holstein Friesian cows. On contrary to our nding, Sawa and Bogucki (2017) found a signi cant effect for FLMY on NC in Holstein Friesian cows. The authors concluded that cows produced 7001-9000 kg milk in their rst lactation had the highest NC (3.09) compared to cows that yielded greater than 11000 kg milk which had the lowest NC (2.30). The authors attributed this to the negative genetic correlation between milk production and fertility traits.
Year of calving had a highly signi cant effect on the NC. The NC was the lowest (2.6) during the period from 2006 to 2014 compared to other periods (Table 1). This effect could be attributed to changes in environment and management conditions over years. The signi cant effect of the year of calving on NC was also recorded by Singh et al. (2018) on Frieswal cows in India. The effect of the season of rst calving on the NC was not signi cant. This is in agreement with Salem and Hammoud (2019) on Friesian cows in Egypt.

4-Lifetime milk production (LMP)
Despite of Shami cows had a longer lifespan than Holstein ones (about, 1.5 times), results in table (2) showed Holstein cows produced lifetime milk production (LMP) greater signi cantly (p<0.01) than that of Shami ones by about 33 %. This could be due to the genetic differences between the two diverse breeds. This result agreed with Cielava et al. (2017) who reported that Holstein black and white cows produced LMP (37916.4 kg) higher than Latvian local Brown and crossbred Latvian Brown cows (35188.6 and 34407.9 kg, respectively) in Latvia. Table (2) indicated that cows calved early at an age less or equal to 25.4 months, produced LMP greater signi cantly (p<0.01) than cows calved lately. This might be attributed to cows that calved at an early age had longer productive life than those cows that calved at age lately, so their LMP was higher. This result agreed with that of Sawa et al. (2018) who reported that Holstein Friesian in Poland calved at an age early between (22.1-26 months) had LMP (more than 25 000 kg) higher than cows calved at an age more than 32 months (19095 kg). The authors explained that cows calved at age more than 28 months had udder diseases and their milk yield was low, therefore those cows culled early. Hutchison et al. (2017) demonstrated that LMP of cows that calved for the rst time at less than 24 months was (25184 kg) higher than cows that calved at the rst time at more than 30 months (20783 kg). Otherwise, Kučević et al. (2020) reported that the age at rst calving had no signi cant effect on LMP on Holstein cows in Serbia.
This study showed that the LMP was increased by increasing the rst lactation milk yield (FLMY), where cows that produced higher than 3229 kg milk yield in their rst lactation scored LMP equals to 12243 kg compared to 7725 kg for cows that produced less than or equal 800 kg in the rst lactation ( Table 2). As a result, FLMY could be used as a predictor tool for LMP of a cow. Tekerli and Kocak (2009) reached to close conclusion for Holstein cows under subtropical conditions. This study pointed out that LDMY increased by increasing the rst lactation milk yield (FLMY). Cows that produced greater than 3229 kg milk yield in their rst lactation had LDMY equals 5.1 kg. Whereas, cows that produced lower than 800 kg milk yield in their rst lactation had LDMY equals 2.4 kg ( Table 2).
Based on the current nding, FLMY could be used as an effective tool to predict LDMY of a cow throughout its productive life. Sawa and Krezel-Czopek (2009) reached almost the same conclusion.
The results of the present study indicated the effect of the year of calving on LDMY was not signi cant (Table 2). This result disagreed with Berihulay and Mekasha (2016) on Holstein Friesian cows in Ethiopia.
Also, the effect of the season of rst calving on LDMY was not signi cant (Table 2), which is in accordance with that reported by Kučević et al. (2020) on Holstein cows in Serbia.

Correlation Coe cients
The estimated values of correlation coe cients between each of AFC and FLMY with LS, PL, LMP and LDMY are shown in Table (3). The calculated correlation coe cients between AFC and each of LS (0.166) and PL (0.042) were positive and highly signi cant (p<0.01). Also, a low positive correlation between AFC and NC was recorded (0.038); however, it was not statistically signi cant. On the other side, highly signi cant negative correlations were estimated between AFC and each of LMP and LDMY (-0.217 and -0.364, respectively). The current results were in accordance with those of Sawa et al. (2018) who estimated a highly signi cant positive correlation between AFC and LS (0.062) in Polish Holstein Friesian cattle. As well as, the authors found negative and highly signi cant correlations between AFC and each of LMP (-0.11) and LDMY (-0.09). However, contrary to our nding, the authors recorded highly signi cant negative correlations between AFC and each of PL (-0.08) and NC (-0.098).
The estimated values of correlation coe cients between FLMY and each of LS, PL and NC were negative and showed a highly signi cant (p<0.01) inverse relationship among each other. Otherwise, Sawa and Krezel-Czopek (2009)

Conclusion
It could be concluded from this study that Shami cows had a longer lifespan, productive life and number of calvings than those of Holstein ones under the Syrian conditions. Shami cows were found as promising local genetic resources that should be exposure to genetic improvement for their productive and reproductive performance. Declarations