Genetic Parameters For Milk Traits In Egyptian Native Cows

The aim of this study is to estimate the genetic parameters and the effect of non-genetic factors for some milk traits including total milk yield (TMY/kg), Lactation period (LP/day), number of services per conception (NSC), days open (DO), calving interval (CI) and dry period (DP). Data were collected from two farms. Experimental Farm belonging to (APRI) data included 1829 records. The statistical analysis has been adopted using animal models. Actual means of TMY/kg, LP/day, NSC/services, DO/day, CI/day and DP/day were 791.3, 171.1, 1.8, 109, 402.7 and 79.3 respectively. Estimated heritability (h 2 ) of TMY, LP, NSC, DO, CI, and DP were 0.18± 0.01, 0.18± 0.001, 0.07± 0.016, 0.09± 0.041 and 0.09±0.001 respectively. The ranges of breeding values BV of cows for TMY/kg, LP/day, NSC, /services, DO/day, CI/day and DP/day were 776.5, 26.7, 6.7, 13.4, 77.1 and 11.5 respectively. The estimated Predicted Breeding Value PBV for all traits varied widely. The genetic trends of cow breeding values were signicant for all studied traits. This conrms that the genetic improvement of these traits leads to increased milk production traits. The study recommends preserving the Native Egyptian dairy cattle because they represent a national wealth that must be preserved from extinction through inventorying the genetic resources, characterization and evaluation of this local breed to benet from it in improving animal breeds of high economic value. Due to the distinction of Egyptian domestic cows for their resistance to various environmental conditions.


Introduction
Egyptian cows are one of the local milk and meat producing breeds in Egypt. They have adapted to environmental conditions, but are threatened by extinction. The Native Egyptian dairy cattle differ in their traits and genetic breeding from global cattle and are kept for preservation of genetic assets. Native cows are a national wealth that must be preserved from extinction. In Egypt, the total Domiati cattle (Native Egyptian dairy cattle) is approximately 2.5million. Proper management is crucial to determine the most important environmental factors affecting the productivity of the herd. Several investigators have screened some of the non-genetic and genetic factors of productive and reproductive traits of that breed under the Egyptian conditions (Abd-Elhamid (2018). The increase of production and reproduction e ciency is implemented by improving the environmental conditions of the animals and the breeding values of the herd. (Katkasame et al., 1996). Genetic trend is de ned as a change in performance per unit of time, which is due to a change in the average breeding values and the direction of change indicates the extent of progress or decline that can be achieved as a result of the breeding plan used. (Ojango and Pollott, 2001).There is a need for continuous evaluation of the effect of genetics on the parameters and trends in Egyptian cows (Amimo et al., 2007). The aim of the study is to address the effect of environmental conditions on milk traits and estimate the heritability, breeding value and genetic trends of Domiati (Native Egyptian dairy cattle). Based on the results of the study, appropriate decisions will be taken to improve herd performance with the goal of genetic improvement of these traits in the future.

Materials And Methods
Data source: The study applies a number of lactations 1829, records of 311 cows, daughters of 118 dams and 69 sires for eight parity during a period from 1996 to 2020 in pure native Egyptian herd of Sids and El-Serw , two farms belonging to (APRI), Egypt as shown in The following statistical mixed model was used.
Y ifjklm = μ + S i + L F +P j + SE k + YR l + L F *SE k + YR l *SE k + P j *SE k + e itFjklm where, Y ifjklm = individual (observation), μ = overall means, Si= arandom effect of i th sire, L F =the xed effect of f th farm lacation, Pj= the xed effect of j th parity of calving, SEk= xed effect of k th season of calving, YR l = the xed effect of l th year of calving, L F *SE k= the xed effect of interaction between the f th farm lacation and the k th season of calving , Y Rl * SE k = the xed effect of interaction between the l th year of calving and the k th season of calving, P j *SE k = the xed effect of interaction between the j th parity of calving and the k th season of calving and e itFjklm = the residual effect with Y ifjklm ~ N (0 , σ2e).

Genetic parameters:
Estimates of (h 2 ) and BV of studied traits were estimated procedures using the single-trait Animal Model (STAM). Boldmanet al.,  The values of the CV% were generally higher for all traits under this study. This re ects a large deal of variations among cows.
Therefore we expect genetic improvement during selection program. These differences among the study estimates and those of other studies may be due to one or more of these reasons: different managerial conditions and climatic, phenotypic and Genetic differences, different models and methods of analysis used and whether some animals were locally produced or imported. Safaa Sanad (2016) who reported that the farm had a highly signi cant effect on milk production traits. These differences among farms may be due to the difference in genetic structure among herds, management practices applied, and the different environmental and climatic conditions due to different regions that affect the adaptation of the cows. The present data in table 3, indicate that winter (December, January and February) were the highest compared to the previous year. Results also indicate that the longer CI and DO were found in cows calving in winter. According to El-Awady and Oudah (2012) the highest yield was in spring and winter because green fodder such as Egyptian clover is available during (December through May) in addition to proper management, which is followed by increased productivity, while in summer and autumn the milk yield decreases due to the inappropriate environmental conditions (heat, humidity) and the decrease in feed intake (green fodder) during this period. With Domiati, Arafa, Samira (1987) found that the least squares mean of LP for winter, spring, summer and autumn were 277, 296, 390 and 287/day respectively. The effect of year of calving on studying traits could be due to different nutritional and managerial practices present within different years. In the current study, year of calving and genotype groups had a highly signi cant effect on all traits (P<0.01). The difference between the authors in estimating the traits of the milk may be due to the following reasons (different number of herds, genetic potentiality changes and management practices, variability of climatic . Proper dairy herd management include an increase in the herd (farm size), and in the use of the technologies (insemination) to aid in improving fertility management, and genetic selection (breeding programs and phenotypes of animals). Nutritional management should be accompanied by the control of infectious diseases, rapid reproductivity diagnostics, fertility improvements, and improved breeding protocols. These factors should facilitate and improve performance, productivity, reproductivity and health of Baladi cows in the future. Egyptian cattle (Native Egyptian dairy cattle) need to be selected and improved to become highly productive, in addition to the importance of care (cleanliness, convenient housing, healthy proper milking, concentrate feeding to compensate for the nutrients lost from the body through milking, pregnancy fetus, calving and etc.) Sig. *** ns *** ns ** ns *= p<0.05 or **= p<0.01or ***= p<0.001and ns= non signi cant .
Genetic parameters: Variance components and heritability: Variance components and estimated heritability genetic covariances for productive and reproductive traits are shown in Table 4

Estimates of breeding values(BV):
The breeding values and genetic trend are presented in Table 5 and Figure 1 and 2 respectively. The estimates of breeding values (BVs) of the studied traits vary widely. Also, the genetic trend of cow breeding value (CBV) are signi cant for all study traits shown in ( gures 1 and 2), which indicated that the selection programs were applied for these herds. Safaa

Genetic trend
The purpose of the genetic trend (GT) study was to increase genetic merit for total milk yield and to determine the effectiveness of using breeding and genetic programs. Thus, the genetic trends in Native Egyptian dairy cattle must be monitored. The annual genetic trends for TMY, LP, NSC, DO, CI, and DP are shown in Figures 1-6.
Total milk yield trait was found to be affected by from year to year due to generation differences throughout the years; there was a negative trend during the 1998, 1999, 2015, 2016 and 2020, while the remaining years gave positive genetic trend at most Genetic trends of cows for TMY, relatively highly compared to their sires and dams gure 1. This indicates the absence of a clear genetic trend of the in uence of years on the TMY for cows, their dams, and their Sirs. The same trend was reported by Safaa Sanad and Hassananen (2019) and Safaa Sanad and Gharib(2020). Total milk production is affected by the year of birth, and this is due to the difference in environmental conditions from year to year. It is noticed that the genetic direction of cows and sires has been determined for TMY and it has been evident that Inter-bull trend validation methods were used to verify that estimates of GT based on traditional PBV were accurate and that BV was not over-estimated. Boichard et al (1995). The rst test compares the GT in o cial evaluations that include data from multiple lactation with evaluations that include TMY traits data, and estimates of GT should be similar for both. The second method compares estimates from subsequent evaluations to determine that BV. The PBV for milk traits is calculated without bias, and the addition of daughter data overtime should not change the average PBV. Adriana et al (2016).
This decline may be attributed to the use of natural insemination and the lack of clear genetic improvement and plans for breeding. The genetic trends of cow breeding values (CBV) were signi cant for all studied traits. This con rms that the genetic improvement of these traits leads to increase milk production traits.
Genetic progress in Native Egyptian dairy cattle has been considerable, although it is so slow compared with previous reports.
I suggest that genetic improvement programs and proper management practices be implemented. There is the need of tracking the results to evaluate their progress to achieve the desired goal of optimizing genetic gain and increasing farm animal pro tability in the future.

Conclusion
In conclusion, Egyptian cows are low in milk production (791 kg) with a short lactation period (171day). The amount of milk varies during the production years, which means the need to implement an effective breeding program. The positive signi cance of the genetic trend of cow breeding value for milk traits indicates the possibility of carrying out the genetic improvement of this trait.
The study recommends preserving the Egyptian cattle (Native Egyptian dairy cattle) because they represent a national wealth that must be preserved from extinction through inventorying the genetic resources, characterization, and evaluation of this local breed to bene t from it in improving animal breeds of high economic value. This is due to the distinction of Egyptian domestic cows for their resistance to various environmental conditions.

Declarations Con ict of interest disclosure
There is no con ict of interest, as the author did not receive any research grants from companies or private or government agencies, and the study was conducted at farm belonging to (APRI), Egypt. Agriculture Research Centre (ARC), Egypt. That does not receive grants. The authors declare that they have no con ict of interest.
Consent for publication: I agree to publish the ndings in your esteemed scienti c journal. Genetic trend of breeding values (Dam, Sire and Cow) for DP in Native Egyptian dairy cattle