The objective of the present study was to estimate genetic trends for lactation milk yield, persistency of milk yield, somatic cell count and interval between first and second calving in Holstein dairy cows of Iran. The dataset consisted of 210,625 test day and 25,883 first parity cows with milk yield recorded from July 2002 to September 2007 comprising 97 herds in Iran. Breeding values of anim...

Milk and serum samples from 35 dairy herds in 17 states were evaluated for cow- and herd-level Mycobacterium avium subspecies paratuberculosis (MAP) antibody test agreement. Evaluation of 6,349 samples suggested moderate agreement between milk and serum enzyme-linked immunosorbent assay (ELISA) results, with a kappa value of 0.50. Cow-level sensitivity (Se) for 18 dairy operations with 1,921 an...

The study aimed to determine factors affecting the dry period length and effect of dry days on milk yield, milk composition and lactation length in the next lactation of dairy cows. Data used for analysis included 7264 lactation records collected from 2012 to 2016 on 4737 Holstein cows raised in 152 herds. The statistical model used to determine the factors influencing the dry period length sho...

The linear model method of VanRaden and Klaaskate for analyzing herd life was expanded. Information on conception and protein yield was included in the estimation of predicted herd life of Israeli Holsteins. Variance components were estimated by a multitrait animal model. Heritability was slightly higher for herd life than for number of parities, but genetic correlations were close to unity. An...

Whether to select for longer life in the herd or shorter calving interval depends on the genetic and phenotypic relationships among herd life, amount of milk in first lactation, and calving interval. Herd life and average calving intmwal are essentially phenotypically uncorrelated. The phenotypic and genetic correlations of herd life and milk in first lactation ranged from .19 to .25 and from ....

test day milk records of a holstein dairy farm collected during years 2004 to 2006 on 142 cows in the 1st lactation vs. 140 cows in the 2nd lactation were used in this research. there were real milk yields of cows available in each part of lactation in this farm making it possible to compare functions based on the new criteria (squared error of estimation). five functions were compared to estim...

To study the genetic relationship between the lifetime milk production (LMP), first lactation milk yield (MY305), and length of productive life (PL) in the Slovenian Brown cattle population, first lactation records from 14,389 cows and lifetime performance records (LMP and PL) from 12,416 cows were used. Records of LMP and PL were normalised using the square root transformation of the raw value...

in this research in order to estimate genetic parameters for milk yield at different milking times for holstein cows of razavi khorasan, a total of 180,462 monthly test day records belonging to first lactation cows calved from 2000 to 2009 were utilized. the records were analysed by a random regression test day model. in the model, the fixed effects of contemporary group of geographical locatio...

Test-day genetic evaluation models have many advantages compared with those based on 305-d lactations; however, the possible use of test-day model (TDM) results for herd management purposes has not been emphasized. The aim of this paper was to study the ability of a TDM to predict production for the next test day and for the entire lactation. Predictions of future production and detection of ou...

to estimate the prevalence of subacute ruminal acidosis (sara) in dairy cows, a total of 196 ruminalfluid samples were drawn by rumenocentesis from 10 dairy herds of khorasan razavi province, northeast ofiran. two groups of 12 cows, early lactation and mid-lactation cows were sampled in each dairy herd andruminal ph was determined immediately using a portable ph-meter. a total of 54 cows (27.6%...