Genetic and Non-Genetic Analysis for Milk Production and Reproductive Traits in Holstein Cattle in Egypt

Faid-Allah E. 2015. Genetic and non-genetic analysis for milk production and reproductive traits in Holstein cattle in Egypt. JITV 20(1): 10-17. DOI: http://dx.doi.org/10.14334/jitv.v20i1.1111 This study was carried out to investigate genetic, non-genetic affecting factors and estimate genetic parameters for milk production and reproductive traits of Holstein cows via animal model. The data was obtained from a commercial farm (Safi Masr for Developing the Animal Resources), located in the Nile Delta, Dakahlia, Egypt. Data included 4791 records of 1797 cows, 794 dams and 76 sires that represented the period from 2002 to 2012. The means and coefficient of variability (CV%) of milk traits as total milk yield (TMY), 305 days milk yield (305-dMY), lactation period (LP) and dry period (DP) were 5787.8 kg (31.1%), 4695 kg (22.1%), 332 days (14.9%) and 72.3 days (27.7%), respectively. Also, the means (CV%) of reproductive traits as days open (DO) and age at first calving (AFC) were 157.9 days (22.6%) and 30.5 month (16.8%), respectively. Sire, dam, parity of cow, year and season of calving had significant effects on traits studied. Heritability estimated were 0.223, 0.184, 0.112, 0.118, 0.105 and 0.285 for TMY, 305-dMY, LP, DP, DO and AFC, respectively. Estimated rG and rP among milk production traits were positive but it takes negative trend with DP and DO. Moderate heritability estimates and positive genetic correlation for most of traits studied suggested that genetic improvement of these traits would be achieved via multi-trait selection.


INTRODUCTION
Friesian cattle are the most reputed dairy cattle in Egypt.In livestock population under computerized recording system, a large size of phenotypic observations is available at low cost and it is worthwhile to use them in estimation of genetic parameters for economic traits.Milk production and reproductive traits are the most important economic traits as sources of income for dairy farmers where high producing and fertile cows are usually profitable.Heritability is the key of genetic parameter which determines the amount of possible genetic progress for selected traits (Usman et al. 2012).Milk yield and adaptability of Holstein are factors of major concern under tropical and subtropical conditions.Under these conditions the focus had always been on milk production, adaptability and survival, they were often overlooked (Usman et al. 2013).
In dairy breeding, selection for the milk yield has been mostly made on the basis of 305-days milk yield (Seyedsharifi et al. 2008;Bilal & Khan 2009).Dry period is one of the important management strategies.Previous studies reported that to maximize milk yield in the next lactation in dairy cows, a 50 to 60 d dry period is necessary (Safa et al. 2013).Reducing dry period length may affect fertility efficiency (Watters et al. 2009).This study was carried out to investigate genetic, non-genetic factors affecting and estimate genetic parameters for milk production and reproductive traits of Holstein cows in Egypt via animal model.

Data
The data obtained from a commercial farm (Safi Masr for Developing the Animal Resources), located at the Nile Delta, Dakahlia, Egypt.Data were comprised from 4791 records of 76 sires and 794 dam during the year 2002 to 2012.Genetic and non-genetic factors as sire, parity (1 st to ≥6 th ), year of calving (2002 to 2012) and calving season (winter from 22/12 to 21/3, spring form 22/3 to 21/6, summer from 22/6 to 21/9 and autumn from 22/9 to 21/12).

Feeding and management
Animals were housed free in shaded open yards, grouped according to average daily milk yield, and fed on TMR system a round year as recommended by NRC (1989).Heifers were artificially inseminated (imported semen of Holstein sires) for the first time when reaching 350 : 370 kg of weight and pregnancy was detected by rectal palpation at 60 days after service.The cows were machine milked three times per day.

Traits studied
Traits studied are total milk yield (TMY), 305-days milk yield (305-dMY), lactation period (LP) and dry period (DP) as milk production traits and days open (DO) and age at first calving (AFC) as reproductive traits.

Statistical model
Factors affecting traits studied were analyzed by general linear model (GLM) using SAS computer program (SAS 2002)

Genetic parameters
The genetic parameters were estimated by derivative free REML with a simplex algorithm using the Multiple Trait Derivative-Free Restricted Maximum Likelihood (MTDFREML) program of Boldman et al. (1995)
The mean (CV%) of reproductive traits as days open and age at first calving (Table 1) are 157.93day (22.62%) and 30.51 month (16.79%), respectively.The low age at first calving in a particular dairy cattle herd is a reflection of the good managerial strategy adopted in that herd.High level of management allows the growing heifers to reach the suitable body weight for breeding earlier and this in turn leads to lower age at first calving.Osman et al. (2013a) reported that in the first parity the average of days open and age at first calving in Holstein cows in Egypt were 185.9±131.7 day (CV%=70.8)and 33.38±5.48month (CV%=16.41),respectively.Furthermore, the mean of the days open for the second parity was 155.5±120.0day (CV%=77.17) Table (1) shows the mean of TMY and 305-dMY were lower than those found by Abou-Bakr et al. (2006) being 13172 and 10847 kg, respectively and those reported by Salem et al. (2006) being 12054 and 9038 kg, respectively Holstein cows in Egypt.The mean of LP was lower than the mean of 370 and 407 days obtained by Abou-Bakr et al. (2006) and Salem et al. (2006), respectively.The estimate of DO obtained in this study was shorter than that of 255 days found by Abou-Bakr et al. (2000), but was similar to 154 days obtained by Abou-Bakr et al. (2006).

Genetic factors
Table (2) shows that sires and dams as a random factors (P≤0.05)significantly affected the milk production and reproductive traits in dairy cattle.This is in agreement with Hamed & Soliman (1994) and Hammoud (2013) for 305-dMY and in agreement with Hamed & Soliman (1994), Hammoud (2013) and Osman et al. (2013a) for LP and DP.Also, the same trend shows for age at first calving as reported by Mokhtar et al. (1993) and Osman et al. (2013a).Osman et al. (2013a) reported that sire as a random effect was significantly affected TMY, and DO.On the contrary, Mokhtar et al. (1993) evidenced that the effect of sire on the dry period was not significant.This means that there are genetic variations for traits studied and the estimations of genetic parameters were high in its accuracy and the possibility in selection was found to get genetic progress for traits studied.

Non-genetic factors
The parity effect was significant (P≤0.01) on milk production and reproductive traits in Holstein cows (Table 3).Similar results reported by Usman et al. (2012).Table (3) also revealed that cows in the first and the second parity had almost the lightest means of 305dMY and TMY in general and it increased with advance of parity and mostly reached its maximum in the 4th and 5th parities.Trend of means for LP, DP and DO increased significantly from first to sixth parity.Also, AFC tend to have a similar trend.Usman et al. (2012) found significant effect of parity on milk yield (P<0.05) while the effect of season  3) represent the significant effect of year of calving on the milk production and reproductive traits in Holstein cows and the cows vary in their milk production and reproductive traits from year to year.El-Arian & Shalaby (2001) and Hammoud (2013) came to the same results for 305-days milk yield.The same results found by Kassab (1995) for lactation period.Moreover, Osman et al. (2013a) reported that year of calving as a fixed effect was significantly affected TMY, LP, DP and DO.This effect was attributed by different investigators to fluctuations in environmental conditions particularly those associated with managerial procedures, weather conditions, nutritional level and feeding practices which would change over years (Mokhtar et al. 1993).In addition, the cows in 2007 were the highest values for 305-days milk yield and TMY in general compared to the other years that may be due to good management decisions in that year.
The effect of season of calving on milk production and reproductive traits were significant (Table 3).The present results are in agreement with those reported by El-Arian & Shalaby (2001) and Usman et al. (2012).On contrary, insignificant effect shown by El-Barbary et al. (1999) for 305-days milk yield.In addition, Kassab (1995) reported a significant season of calving effect on LP.On the contrary, an insignificant difference in LP due to season of calving was reported by Salem & Omar (1994).Significant season of calving effect on DP was reported by Hamed & Soliman (1994) and Kassab (1995).However, season of calving had nonsignificant effect on DP (Kassab 1995).Moreover, Osman et al. (2013a) reported that that season as a fixed effect was significantly affected TMY, LP and DO except DP was not affected significantly.
Table (3) shows that the cows vary (P≤0.01) in their milk production and reproductive traits due to season of year and shows high mean values in spring and winter for 305-dMY and TMY.Kaygisiz (2013) came to the same conclusion that year and season of calving significantly influenced 305-dMY (P<0.01).Endris et al. (2013) reported that the effect of year-season of calving had a very highly significant (P<0.001)effect on total milk yield, and 305d milk yield of Holstein crossbred cows.In contrary, Usman et al. (2011) found non-significant effect of season of calving on milk yield.In addition, significant effect of season of calving on age at first calving was found by Sandhu et al. (2011) and Sahin et al. (2012).Sandhu et al. (2011) and Usman et al. (2011) found higher lactation milk yield in spring and lower in the summer.Abdel-Gader et al. (2007) reported that milk production was highest in winter than the other seasons.Javed et al. (2004) reported that milk production was highest in the autumn and spring seasons and lowest in hot summer.
The discrepancy in milk yield, especially lower milk production in the summer, may be due to heat stress, lower metabolism, poor quality and inadequate quantity of feed and high parasitic load in this weather that suffered the cattle to the extent that the animals could not maintain their production.Overcoming the environmental barriers the production can be intensified in these conditions, which can be achieved by management interventions by providing suitable environment and balanced ration in the hot summer.A number of methods are been used by dairy farmers to cool lactating cows during summer, but the most common is use of water spray and fans to facilitate evaporative cooling.Appropriate housing that assists in dissipating heat might bring about reduction in the severity of the problems (Usman et al. 2013).
The previous investigations revealed a substantial variation in heritability estimates of AFC.High estimates were 0.48 and 0.42 as reported by Suhail et al. (2010) and Ayied et al. (2011), respectively.On the contrary, low heritability estimate of AFC was 0.098 that mentioned by Abdel-Gader et al. (2007).

Genetic and phenotypic correlation coefficients
Table (4) represents coefficients of genetic correlation (rG) and phenotypic correlation (rP) among milk production and reproductive traits.All coefficients were positive, except that between DP and each of TMY, 305-dMY and LP were negative.Moreover, 305-dMY with DO had also negative correlation.
Positive genetic correlation between 305-dMY in dairy cattle and LP were reported by El-Arian et al. (2003), Salem et al. (2006) and Hammoud (2013).Also, genetic and phenotypic correlations of 305-dMY and DP were negative as reported by EL-Arian et al. (2003) and Salem et al. (2006).Genetic correlation between 305-dMY and DP were positive (rG=0.54 and 0.29) as mentioned by Ojango & Pollott (2001) and Hammoud (2013), respectively. Table (4) shows that genetic correlation coefficients between LP and DP were negatively correlated.Similar results reported by El-Arian et al. (2003) and Salem et al. (2006).The positive genetic correlations between traits especially productive ones clarified that these traits could be improved simultaneously via multi-trait selection breeding program.
Elshalmani (2011) depicted positive genetic correlations of 0.23 to 0.98 among TMY, LP and DO of Holstein cows.Moreover, Zink et al. (2012) obtained genetic correlation of 0.39 between TMY and DO.

CONCLUSION
According to the present study indicated that Holstein breed in Egypt can show high milk production and good reproductive traits under adequate circumstances.
Moderate heritability estimates and positive genetic correlation for most of traits studied suggested that genetic improvement of these traits would be achieved via multi-trait selection.The high positive genetic correlations between traits especially productive ones clarified that these traits could be improved simultaneously via multi-trait selection breeding program.

Table 1 .
Descriptive statistics of milk production and reproductive traits in Holstein cows

Table 2 .
Genetic factors affecting milk production and reproductive traits in Holstein cows

Table 3 .
Non-genetic factors affecting milk production and reproductive traits in Holstein cows

Table 4 .
Heritability estimates (diagonal), genetic (below) and phenotypic (above) correlation coefficients for milk production and reproductive traits in Holstein cows