No abstract

The objectives of the present study were to estimate mean, heritability, genetic and phenotypic correlations and genetic trend. Data of 1776 records of Egyptian buffaloes, kept at Mehallet Mousa farm, Ministry of Agriculture, during the period from 1972 to 2002 were used to estimate the genetic parameters for productive traits, total milk yield (TMY), 305-day milk yield (305-DMY), lactation period (LP) and dry period (DP) and the reproductive traits were calving interval (CI) and days open (DO). Data were analysed using the software package VCE-6 Groeneveld et al (2010).

This study had two aims. Firstly, to determine the associations of month of recording (MOR) and days in milk (DIM) with somatic cell count (SCC), milk urea concentration (MU) and milk production traits (i.e. test-day milk yield, TDM; milk protein percentage, PP and milk protein yield, PY). Secondly, to evaluate the associations among SCC, MU and milk production traits by analyzing individual monthly test-day records for dairy cows raised in the Czech part of the Czech Republic. A total number of 33,881 individual test-day milk records involving 15,565 dairy cows for a 12-month period between January and December 2001 enrolled in Database Computer Center belonging to Czech Moravian Breeders´ Corporation, Inc., Hiradistko, The Czech Republic were used. Data were analyzed using General Linear Model procedure (GLM) using Statistical Analysis System (SAS, 2004). The MOR and DIM had highly significant (P<0.001) effects on the studied traits. The SCC reached the maximum level in September (504,000) associated to the lowest TDM (19.9 kg) and the lowest SCC in December (320,000) and February (335,000 cell/ml). Least squares means of TDM, categorized by 30-d increments of DIM, paralleled reversible changes in PP and followed a curvilinear shape. SCC reached to the peak in the 2 nd and 3 rd months of lactation then decreased gradually to the end of lactation. MU was lower (30.5 mg/dl) during the first 30 DIM compared with all other DIM categories. The statistical analysis of TDM, PY and SCC by MU showed that as MU increased, TDM, PY increased and SCC decreased. MU, SCC, PP and PY were significantly different among TDM categorized. Each of PP and SCC measures inversely associated with TDM, meanwhile MU paralleled change with TDM. Somatic cell count measures showed a paralleled change with PP. The effects of environmental variables and associations among traits must be taken into consideration when cows are evaluated. Keywords: dairy cattle, days in milk, environmental effects, milk urea nitrogen * MOR=month of recording, DIM=days in milk (day), MUC=milk urea content categories (mg/dl), PPC=protein percentage categories (%), MYC= test-day milk yield categories (kg), SSC=somatic cell score categories, SCC= Somatic cell count (x1000) , SCS= Somatic cell score, TDM= Test-day milk yield (kg), MU= Milk urea content (mg/dl), PP=Protein percentage (%), PY= Protein yield (kg)

A total of 4,752 monthly lactation records of Friesian cows during the period from 2000 to 2005 were used to estimate genetic parameters and to determine the effect of udder health on milk production traits. Three milk production traits were studied: 305day milk yield (305-dMY), 305-day fat yield (305-dFY) and 305-day protein yield (305-dPY). Four udder health traits were studied: somatic cell count (SCC), mastitis (MAST), udder health status (UDHS) with 10 categories and udder quarter infection (UDQI) with 7 categories. Mixed model least square analysis was used to estimate the fixed effects of month and year of calving and parity (P) on different studied traits. Sire and dam within sire were included in the model as random effects. Data were analyzed using Multi-trait Derivative Free Restricted Maximum Likelihood methodology (MTDFREML) to estimate genetic parameters. Unadjusted means of 305-dMY, 305-dFY, 305-dPY and SCC were 3,936, 121, 90 kg and 453,000 cells/ml, respectively. Increasing SCC from 300,000 to 2,000,000 cells/ml increased UDQI from 5.51 to 23.2%. Losses in monthly and lactationally milk yields per cow ranged from 17 to 93 and from 135 to 991 kg, respectively. The corresponding losses in monthly and lactationally milk yields return per cow at the same level of SCC ranged from 29.8 to 163 and from 236 to 1,734 Egyptian pounds, respectively. Heritability estimates of 305-dMY, 305-dFY, 305-dPY, SCC, MAST, UDHS, UDQI were 0.31±0.4, 0.33±0.03, 0.35±0.05, 0.23±0.02, 0.14±0.02, 0.13±0.03, and 0.09±0.01, respectively. All milk production traits showed slightly unfavorable negative phenotypic and genetic correlations with SCC, MAST, UDHS and UDQI. There were positive and high genetic correlations between SCC and each of MAST (0.85±0.7), UDHS (0.87±0.10) and UDQI (0.77±0.06) and between MAST and each of UDHS (0.91±0.11) and UDQI (0.83±0.07). It could be concluded that the economic losses from mastitis and high SCC are considerable. The high genetic correlation between SCC and clinical mastitis (CM) suggest that the selection for lower SCC would help to reduce or eliminate the undesirable correlated responses of clinical mastitis associated with selection for increasing milk yield. Additionally, it is recommended also that if direct information on under health traits is not available, measures of SCC can be inclusion in a selection criteria to improve the income from dairy cows.

Data used in this investigation were collected from 4370 records relevant to 874 purebred Friesian cows which belong to Shobratana Animal Production Society, located in the north part of Delta region near Tanta city in Egypt. These cows were daughters of 43 sires. The records used covered the period from 1985 to 2003. The following six productive and reproductive traits of the first lactation were analyzed: Total Milk Yield (TMY, kg), dry period (DP, day), lactation length (LL, day), days open (DO, day), calving interval, (CI, month) and age at first calving (AFC, month).sire random effect and month and year fixed effect. Data were analyzed using Linear Mixed Model Least Squares and Maximum Likelihood (LSMLMW) computer program of Harvey (1990). The overall means of TMY, DP and LL were 5387 kg, 72.9 days and 327 days, respectively. The overall means of CI, DO and AFC were 13.4 month, 121 days and 27.8 month, respectively. Heritability estimates for TMY, DP, LL, CI, DO and AFC were 0.141±0.074, 0.109±0.069, 0.040±0.057, 0.104±0.068, 0.202±0.084 and 0.217±0.087 respectively. The ranges of breeding values of all sires in the pedigree for TMY, DP, LL, DO and CI were 685 kg, 18 day, 8.15 day, 48.2 day and 1.05 month, respectively. Spearman rank correlations and Pearson correlations among estimated breeding values of all sires in pedigree provided by the genetic analysis ranged between -0.712 to 0.907. The objectives of the present study were: 1) to estimate some genetic and non-genetic factors affecting productive and reproductive traits, 2) to estimate genetic and phenotypic parameters for these traits and 3) to estimate breeding values for sire Friesian cows in this farm. Rank correlations of animals between traits were the lowest for reproduction traits. It could be concluded that improving the environmental conditions will improve these traits.