Genetic parameters for Friesian cows were estimated from 9155 lactation records for 3635 cows sired by 184 bulls. Multi-trait repeated animal models were employed using the REML procedure to estimate covariance components of total milk yield (TMY), service period (SP) and calving interval (CI). There is sufficient genetic variation (indicated by the coefficient of genetic variation) in total milk yield, service period and calving interval traits (15.6, 3.6 and 3.7%, respectively). Estimates of heritability for TMY, SP and CI traits were 0.170, 0.010 and 0.044, respectively. Permanent environmental variance ratios were 0.162, 0.017 and 0.048 for TMY, SP, and CI, respectively. Genetic correlations among SP and CI traits were high (0.998), however genetic correlations of reproductive with productive traits were unfavorable (0.512-0.661). The results indicated the possibility of continued selection for increased milk production which has deleterious effects on reproductive traits. The annual genetic changes were positive for TMY, SP, and CI (7.76 kg/yr, 0.076, and 0.24 d/yr, respectively). These positive trends indicate that there has been success in choosing better sires.The corresponding annual phenotypic changes for the same traits were positive (13.9 kg/yr, 0.029 and 0.82 d/yr, respectively). Positive annual genetic and phenotypic changes for SP and CI indicated that with improving milk yield the SP and CI will be increased. The financial situation of the farm is affected by the extension of the calving interval. The lower the calving interval, the more profitable the farm becomes, and prolonging this period for one day causes a financial loss for the farm.

The purpose of this study was to estimate the genetic and phenotypic parameters in order to obtain the trends of 305˗day milk yield (305˗DMY) lactation period (LP), calving interval (CI) and days open (DO) of Friesian cows. Data consisted of 5728 lactation records for 2040 Friesian cows sired by 139 bulls during the years from 1979 to 2016 at Sakha and El-Karada Farms inherent in the Animal Production Research Institute (APRI), Kafr-Elsheikh Governorate, Egypt. Data were analyzed using Harvey program statistic (Harvey, 1990) to determine the fixed effects to be included in the analytical model. Covariance components were estimated for univariate and bivariate analysis for all traits with derivative-free restricted maximum likelihood (REML) procedures using the MTDFREML program of Boldman et al., (1995). Means for 305-DMY, LP, CI and DO were 2632.09 kg, 300.02 d, 449.92 d and 173.95 d, respectively. Heritability estimates were 0.24, 0.22, 0.16 and 0.17 for the similar previous traits, subsequently. The genetic correlation between all traits studied were moderate and positive, ranging from 0.26 to 0.75. Corresponding phenotypic correlations between different traits under investigation were small and positive and ranged between 0.05 to 0.29. The annual genetic changes in the breeding values (BV's) were positive for 305-DMY (6.10 kg/yr.) while being negative for LP, CI and DO (-0.16,-0.05 and-.06 d/yr, respectively), indicating that there is an achievement superior sires however more attention should be given to reproductive traits to avoid losses related to these traits in the future. The results indicated that the use of top ranking bulls on the basis of their (BV's) for milk yield traits in breeding program will lead to noticeable genetic improvement in productivity of Friesian cows in Egypt.

Genetic parameters for Friesian cows were estimated from 9155 lactation records for 3625 cows sired by 182 bulls covered 34 years in two herds (Sakha and El-Karada), belongs to the Animal Production Research Institute, Ministry of Agriculture, Egypt. Multi-trait repeated animal model was employed using the REML procedure to estimate (co)variance components of productive (305-day milk yield-M305 and lactation period-LP) and reproductive traits (number of services per conception-NSC, calving to first service interval-CFS and days open-DO), There is sufficient genetic variation in productive (from 9.5 to 17.1%) and reproductive traits (from 3.9 to 10.3 %). Heritability estimates for M305 and LP traits were 0.204 and 0.110, however, reproduction traits were ranged from 0.010 to 0.044. Genetic correlation between M305 and LP was high (>0.94). Among reproductive traits, absolute genetic correlations were also high (>0.85). Genetic correlations between reproductive and productive traits were high (>0.99). The annual genetic changes were positive for M305, LP, CFS and DO (9.07 kg/yr., 0.30, 0.07 and 0.24 d/yr., respectively), however it was -0.003 number/yr for NSC. The annual phenotypic changes were positive for M305, CFS and DO (12.4 kg/yr., 0.029 and 0.829d/yr., respectively), however it were negative for LP and NSC (-0.265 d/yr. and -0.002 number /yr.).

Data from 3081 reproductive records of Friesian heifers covering the period from 1979 to 2013 belongs to Sakha and El-Karada experimental farms -Kafr-El-Sheikh Governorate, Animal Production Research Institute, Ministry of Agriculture, Egypt were analyzed. A multitrait animal model was used to estimate genetic parameters, genetic and phenotypic changes for age at first breeding (AFB), age at successful breeding (ASB), age at first calving (AFC), number of services per conception (NSC) and service period (SP). Heritabilities of AFB, ASB, AFC, NSC and SP were 0.15, 0.12, 0.11, 0.02 and 0.01, respectively. Genetic correlations between AFB, ASB and AFC were high and ranged from 0.97 to 0.99, however the phenotypic correlations were ranged from 0.78 to 0.99. Genetic correlations between NSC and both AFB, ASB and AFC were -0.12 to 0.16, however the corresponding phenotypic correlations were ranged from -0.04 to 0.46. The genetic correlations between SP and both AFB, ASB and AFC were ranged from 0.58 to 0.79, however that corresponding estimates of phenotypic correlations were ranged from 0.01 to 0.56. The genetic and phenotypic correlations between NSC and SP were 0.72 and 0.94, respectively. A linear regression analysis of estimated breeding values on year of birth of heifers showed favorable genetic improvement of all fertility traits, however the reverse phenotypic trend was observed for AFB, ASB and AFC.

Lactation traits and reproductive performance of three trials of crossing Holstein cattle (H) and German Friesians (F) raised in a hot climatic were evaluated. The first 90-day (M90), 305-day (M305) and total milk yield (TMY), 305-day milk yield per day of calving interval (MCI1), total milk yield per day of calving interval (MCI2) along with length of lactation period (LP), age at first calving (AC1) and calving interval (CI) were used. For these traits, a genetic model was applied for each trial separately to obtain estimates of individual (G I ) and maternal (G M ) additive effects, individual (H I ) and maternal (H M ) heterosis and individual recombination effect (R I ). Data of 8045 normal lactations from the three trials were analysed. Among the crossbreds obtained in the three trials, cows of 3 / 4 H 1 / 4 F ranked first in their lactational performance. Estimates of G I and G M were generally large and in favour of H cows (daughters) and dams for most milk-yield traits, CI and AC1 in the three trials. Estimates of H I in crossbred cows for milk traits, CI and AC1 were mostly negative and reveal that crossing F with H was associated with a reduction in milk-yield traits, shorter CI and earlier AC1 along with longer LP in the three trials. Estimates of H M for milk yields, LP, AC1 and CI in daughters of crossbred dams were mostly negative. Recombination losses in crossbred cows were negative for milk-yield traits, AC1 and CI in most cases. Zusammenfassung Schä tzung von Heterosiswirkungen in Merkmalen der Laktation und Fruchtbarkeit in 3 Kreuzungsversuchen zwischen Holstein Friesian und Dt. Schwarzbunten unter heißen klimatischen BedingungenEs wurden drei Versuche mit Kreuzungen zwischen Holstein (H) und deutschen Schwarzbunten (F) in heißem klima ausgewertet, wo 90 Tage (M90), 305 Tage (M305) und Gesamtmilchleistung (TMY), Tagesmilchleistung während des 303 Tage Intervalls (MCI1) und während der Zwischenkalbezeit, Länge der Laktationsperiode (LP), Erstkalbealter (AC1) und Zwischenkalbezeit (CI) untersucht worden sind. Es wurden geschätzt, fü r jeden Versuch separat, individuelle (G I ) und matennale (G M ) additive Wirkungen, individuelle (H I ) und maternale Heterosiswirkungen sowie individuelle Rekombinationswirkung (R I ). Daten von 8045 normalen Laktationen konnten analysiert werden. Rü ckkreuzungen zu H ( 3 / 4 H 1 / 4 F) zeigten unterKreuzungen die hö chsten Leistungen. Additive Wirkungen, individuelle und maternale, ware groß und zugunsten H fü r die meisten Leistungseigenschaften, individuelle Heterosis fü r diese und CI sowie AC1 meistens negativ, sodaß Kreuzungen von H und F nicht empfohlen werden. Dies resultierte in weniger Milch, kü rzeres CI und frü here AC1 mit längerem LP. Rekombinationsverlust war negativ fü r Milchleistung, AC1 und CI in den meisten Fällen. U.S.