Estimativas de herdabilidade e tendências genéticas para característicasde crescimento e reprodutivas em bovinos da raça Nelore 0.171 (0.01); 0.219 (0.02); 0.186 (0.03); and 0.224 (0.02) kg per year, for WW, PW, GBW, and GWP, respectively, corresponding to increases of 0.10, 0.08,

The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank..

Records of birth weight (BW) and weights standardized to 210 (W210); 365 (W365) and 550 (W550) of age in the Nellore breed were used to estimate variance components of genetic effects and predict genetic values of sires. The model included the fixed effects of contemporary group and cow age at calving as co-variable, and the additive and maternal genetic, permanent maternal environmental, and temporary environmental random effects. Estimates of means and standard deviations for BW, W210; W365 and W550 were 32.76 ± 3.74; 184.30 ± 29.02; 240.31 ± 41.85 and 322.12 ± 60.77, respectively. A significant additive genetic variability was detected for all weights. The permanent maternal environmental variance showed greater relevance on weaning weight, and it was practically inexistent after weaning. For the maternal genetic variance, the estimate for birth weight was more significant as compared with weaning weight. The estimated heritability values for BW, W210; W365 and W550 were 0.37 ± 0.02; 0.36 ± 0.03; 031 ± 0.01 and 0.38 ± 0.02, respectively. Genetic correlations between birth weight and other weights were of low magnitude, with high values of weights at other ages. The use of sires of higher genetic value for total maternal effect makes it possible to use sires that are more positive for weaning weight and also for year and yearling weight.

Genetic parameters for test-day milk flow (TDMF) of 2175 first lactations of Holstein cows were estimated using multiple-trait and repeatability models. The models included the direct additive genetic effect as a random effect and contemporary group (defined as the year and month of test) and age of cow at calving (linear and quadratic effect) as fixed effects. For the repeatability model, in addition to the effects cited, the permanent environmental effect of the animal was also included as a random effect. Variance components were estimated using the restricted maximum likelihood method in single-and multiple-trait and repeatability analyses. The heritability estimates for TDMF ranged from 0.23 (TDMF 6) to 0.32 (TDMF 2 and TDMF 4) in single-trait analysis and from 0.28 (TDMF 7 and TDMF 10) to 0.37 (TDMF 4) in multiple-trait analysis. In general, higher heritabilities were observed at the beginning of lactation until the fourth month. Heritability estimated with the repeatability model was 0.27 and the coefficient of repeatability for first lactation TDMF was 0.66. The genetic correlations were positive and ranged from 0.72 (TDMF 1 and 10) to 0.97 (TDMF 4 and 5). The results indicate that milk flow should respond satisfactorily to selection, promoting rapid genetic gains because the estimated heritabilities were moderate to high. Higher genetic gains might be obtained if selection was performed in the TDMF 4. Both the repeatability model and the multiple-trait model are adequate for the genetic evaluation of animals in terms of milk flow, but the latter provides more accurate estimates of breeding values.Keywords: functional trait, genetic correlation, heritability, milkability ImplicationsThe milk flow trait can be considered as functional, of great importance in dairy cattle, both related to udder health on the efficiency of labor. A increased milk flow is associated with a decrease in occupancy time of labor and thus a decrease in spending on it. In addition, a faster milking implies a reduction in electricity costs and maintenance of machines. Studies investigating milk flow are still limited and the best approach for analyzing this trait has not been well defined.

Mozzarella cheese is traditionally prepared from bubaline (Bubalus bubalis) milk, but product adulteration occurs mainly by addition of or full substitution by bovine milk. The aim of this study was to show the usefulnes of molecular markers to identify the admixture of bovine milk to bubaline milk during the manufacturing process of mozzarella cheese. Samples of mozzarella cheese were produced by adding seven different concentrations of bovine milk: 0%, 1%, 2%, 5%, 8%, 12% and 100%. DNA extracted from somatic cells found in cheese were submitted to PCR-RFLP analysis of casein genes: α-s1-CN -CSN1S1 that encompasses 954 bp from exon VII to intron IX (Alu I and Hinf I), β-CN -CSN2 including 495 bp of exon VII (Hae III and Hinf I), and κ-CN -CSN3, encompassing 373 bp of exon IV (Alu I and Hind III). Our results indicate that Hae III-RFLP of CSN2 exon VII can be used as a molecular marker to detect the presence of bovine milk in "mozzarella" cheese. Mozzarella cheese has its origin in Italy where it is traditionally manufactured from bubaline (Bubalus bubalis) milk. The most commonly employed production process of mozzarella cheese is a traditional technique where bacterial fermentation of milk induces pH reduction and curd precipitation (Chapman et al., 1981). Nowadays, many countries that have a considerable number of buffalo cows widely use the milk of these animals for mozzarella cheese production.Some dairy products can be adulterated by milk admixture from different species in order to maximize profit. Certification is, thus, a way to guarantee cheese quality and to protect consumers against fraudulent producers. Bubaline breeders demand high precision technology to validate milk origin to assure that only bubaline milk is present in the composition of the manufactured product. The most common type of adulteration in the manufacture of mozzarella cheese is the addition or full replacement of bubaline milk by bovine milk. Consequently, several methods have been developed to detect milk mixture in these products.Methods based on electrophoresis and chromatography include isoelectric focusing (Moio et al., 1989), high-performance liquid chromatography (Visser et al., 1991;Veloso et al., 2002;Enne et al., 2005), nuclear magnetic resonance spectroscopy (Andriotti et al., 2000), and also hydrophobic interaction chromatography (Bramanti et al., 2003). However, these methods present limitations due to time intensive protocols and/or high costs.An alternative way to detect milk mixtures is the use of molecular markers to identify the DNA of different species (Bardin et al. 1994;Branciari et al., 2000;Rea et al., 2001;Bottero et al., 2002; Leoparelli et al., 2007). Here we describe a relatively rapid and simple method to identify admixtures of bovine milk to bubaline milk, by extracting DNA directly from Mozzarella cheese and analyzing a β-casein gene polymorphism.Samples of "pasta filata" mozzarella cheese were produced using 7 L of milk according to the methodology developed by Kuo et al. (2001). The samples ...