Genetics of casein content in Brown Swiss and Italian Holstein dairy cattle breeds

Over 2,000,000 records of casein contents were collected from herds of Brown Swiss (BS) and Italian Holstein Friesian (HF) dairy cows in northern Italy during routine milk recording. Variance components for casein and genetic correlations of casein with production and type traits considered in selection were estimated from a sample of 200,484 test day records for 26,279 BS cows and 376,652 for 41,543 HF cows. A multivariate multi-model REML estimation of variance components was made. Models for production included the fixed effects for herd-test day, year of evaluation, days in milk, month of calving and age at calving within parity. Models for type traits were defined accordingly to the model officially used for each breed for breeding value estimation. Breeding values for casein yield and content were calculated from estimated heritabilities (Brown 0.12; Holstein 0.09). Estimates were similar for protein and casein yield and content while genetic correlations with traits in the actual selection indexes differed between breeds. These differences, together with the greater emphasis now given to protein in the selection index of the Brown Swiss than in the Italian Holstein Friesian, suggest that a direct selection for casein could be more advantageous in Brown than in Holstein cows. The Brown breeders association could soon include casein yield and content directly in their selection criteria while that of Holstein cows would wait for a longer term casein data collection

Genetic parameters for casein and urea content in the Italian Brown Swiss dairy cattle

A total of 137,753 test day records of 20,745 Italian Brown Swiss dairy cows from 26 provinces of Italy were used to estimate heritability for casein and urea content in milk and their genetic correlations with other production traits and milk somatic cell score. Milk component values were obtained by Fourier Transformed Infrared (IR) Spectroscopy from milk samples collected during national routine recording and were analysed using test day repeatability animal models. Fixed effects included 1,001 levels of herd-test date, 15 classes of days in milk, and 13 classes of age at calving within parity. The variation among cows was large for most of the traits. The heritability value for casein content was 0.31, as for protein content, and genetic and phenotypic correlations between these two traits were large (0.99 and 0.97 respectively). Milk urea content had a heritability of 0.17 and a positive genetic relationship with fat (0.12), null with protein (0.03) and casein (0.002) content and a negative genetic correlation with milk yield (-0.17) suggesting that the genetic improvement for milk urea content would be possible, but genetic gain would be affected by other traits included as selection criteria in the economic index and by their relative economic emphasis

Genetic evaluations for measures of the milk-flow curve in the Italian Brown Swiss population

The objective of this study was to estimate heritabilities and genetic correlations between milk-release parameters, somatic cell score, milk yield, and udder functional traits in the Italian Brown Swiss population. Data were available from 37,511 cows over a span of 12 yr (1997-2008) from 1,592 herds. Milking flows were recorded for each individual once during lactation. Three different analyses were performed to estimate variance components for all the traits of interest. The first analysis included single control data milk yield, somatic cell score, maximum milk flow, average milk flow, time of plateau, decreasing time, and total milking time, whereas the second analysis included milk-release parameters as well as total udder score, udder depth, and 305-d milk yield and somatic cell score as dependent variables. The third analysis included total milking time, 305-d milk yield and somatic cell score, total udder score, udder depth, and ratios of maximum milk flow over total milking time (R1), time of plateau (R2), and decreasing time (R3) to estimate the relationship between the shape of the milk-release curves and important milking traits. Results from the first and second analysis found similar heritabilities for milkability traits ranging from 0.05 to 0.41 with genetic correlations between production traits and flow traits ranging from low to moderate values. Positive genetic correlations were found among production, somatic cell score, and milkability traits. The third analysis showed that R1 had the greatest heritability of the ratio traits (0.37) with large genetic correlations with R2 and R3, a low correlation with 305-d somatic cell score, and no correlation with 305-d milk yield. Estimated responses to selection over 5 generations were also calculated using different indexes, which included either flow or ratio traits. The results of this study show that it is possible to use information collected through portable flowmeters to improve milkability traits. Using a set of variables or traits to describe the overall release of milk can be an advantageous selection strategy to decrease management costs while maintaining milk production

Interfamiliar specific fertility in Italian Brown Swiss cattle

The aim of this study is to evaluate the effects of interaction between sire of cow and service sire on the success/unsuccess of inseminations. Data from insemination events of Italian Brown Swiss cows collected from January 1993 through August 2007 were restricted to repeat breeder cows. A cluster analysis was carried out to group herds with very few observations in clusters with at least 15 observations. The edited data set included 102,710 services of 10,708 cows, daughters of 1,716 sires and mated to 3,108 service sires. The success or unsuccess at each insemination was evaluated by a linear mixed model including the fixed effects of herd-year interaction, month of insemination, age, and the random effects of sire service-sire of cow interaction and residual. The distribution of bull combination estimates was bimodal. When the tails of distribution (best and worst 5% of estimates) were considered, 271 service sires were included in both tails. Results suggest that major gene can affect the survival of embryos and that positive or negative interactions between paternal and maternal genotype can affect this reproductive trait

Bimodality and the genetics of milk flow traits in the Italian Holstein-Friesian breed

The overall goal of this study was to investigate milk flow traits in Italian Holstein-Friesian cows and, in particular, the bimodality of milk flow, defined as delayed milk ejection at the start of milking. Using a milkometer, 2,886 records were collected from 133 herds in northern Italy from 2001 to 2007. All records included 5 time-period measurements for milk flow, somatic cell score (SCS), milk yield, 8 udder type traits, and the presence or absence of bimodality in milk flow. Genetic parameters were estimated using linear animal models for continuous traits such as milk flow, udder type, SCS, and milk production, whereas bimodality was analyzed as a categorical trait. With the exception of decreasing time (which had a very small heritability value of 0.06), heritability values for milk flow traits were moderate, ranging from 0.10 (ascending time) to 0.41 (maximum milk flow). In addition, moderate to high genetic correlations were estimated between total milking time and other time measures (from 0.78 to 0.87), and among time flow traits (from 0.62 to 0.91). The decreasing time was the trait most genetically correlated with udder type traits, with correlation values of 0.92 with rear udder height, 0.85 with rear udder width, and 0.73 with teat placement. Large udders with strong attachments were also associated with greater milk production. Heritability estimated for bimodality was 0.43, and its genetic correlation with milk flow traits and SCS indicated a sizable genetic component underlying this trait. Bimodality was negatively associated with milk production; shorter milking times and greater peak milk levels were genetically correlated with more frequent bimodal flows, indicating that faster milk release would result in an increase in bimodal patterns. The negative genetic correlation of bimodality with SCS (-0.30) and the genetic correlation between milk flow traits and SCS suggest that the relationship between milkability and SCS is probably nonlinear and that intermediate flow rates are optimal with respect to mastitis susceptibility. Quicker milk flow over a shorter period would increase the frequency of bimodal curves in milking, whereas the correlation between bimodality and both ascending and descending time was less clear

Genome-wide association study for somatic cell score in Valdostana Red Pied cattle breed using pooled DNA

Mastitis is a major disease of dairy cattle occurring in response to environmental exposure to infective agents with a great economic impact on dairy industry. Somatic cell count (SCC) and its log transformation in somatic cell score (SCS) are traits that have been used as indirect measures of resistance to mastitis for decades in selective breeding. A selective DNA pooling (SDP) approach was applied to identify Quantitative Trait Loci (QTL) for SCS in Valdostana Red Pied cattle using the Illumina Bovine HD BeadChip

Variation of milk components in the Italian Brown cattle

The aim of this study was to evaluate the variations of protein, casein, saturated (SFA), unsaturated (UFA), monounsaturated (MUFA), polyunsaturated (PUFA) fatty acids contents and cheese yield in the milk of two groups of Italian Brown cows conventionally reared in indoor period of housing or consuming pasture during the summer months in 2008 and 2013. Milk components were obtained from samples collected during the national routine (conventionally reared) and 'extraordinary' (pasture period) milk recording scheme in herds located near Sondrio (Lombardia, Italy). Milk samples were processed with the MilkoScanTM FT6000 for the identification of milk casein, SFA, UFA, MUFA and PUFA composition. The groups were analysed separately per year and the environmental factors affecting milk protein, casein, and fatty acids contents (pasture/indoor, parity, data of sampling, days in milk, days from collection to analysis) were included in the MIXED procedure of SAS 9.3. A total of 778 milk samples were available, including 234 records from indoor and 544 observations from pasture feeding. Pasture intake affected the content of casein (%) and the proportion of fat in milk (g/100 g), enhancing milk casein levels (from 2.90 to 3) and reducing the concentration of milk SFA in milk from grazing cows (from 2.29 to 1.92). Additionally, the cheese yield was calculated as 'kg of cheese per 100 kg of milk' and resulted to be 10.4 and 12 in 2008 from milk of cows reared indoor and with pasture based diet, respectively. The dairy industry should take advantage of the milk production during grazing periods from which high quality products may be obtained

The QuaLAT Project : Mapping QTL for Milk Fatty Acid Content in the Italian Brown Population and in the Israel Holstein Friesian

Milk contains a number of micro-components ("functional foods") having specific health promoting activities. Important among these compounds are the conjugated linoleic acids (CLAs) consistingof a mixture of isomers of C18:2 fatty acid with conjugated doublebonds. The predominant form in milk fat is the cis-9,trans-11 isomer, accounting for 75 to 90% of the total CLA content. Biomedical studies with animal models have demonstrated a variety of preventive health effects from CLA including anticarcinogenic, antiatherogenic, antiobesity, immune system enhancement and antidiabetic benefits. Linolenic acid does not form CLA as an intermediate in rumen biohydrogenation, but it does form vaccenic acid (C18:1,t11) that enters the bloodstream from the rumen, through the abomasum and intestine, and is transported to the mammary gland. Several investigations using direct and indirect approaches established that endogenous synthesis of CLA via \u394 9-desaturase action on vaccenic acid (VA, C18:1,t11) is the predominant source of the CLA found in milk fat across a range of diets. Thus, rumen VA production and mammary tissue \u394 9-desaturase (D9D) are of key importance in determining the CLA content of milk fat. Mammary tissue D9D activity is measured indirectly as the milk desaturase index (DI), calculated as the ratio of milk CLA to the sum of milk CLA and VA. The study is centered on the Italian Brown Swiss and Israeli Holstein dairy cattle populations. Objectives of the project are: i) to identify environmental and physiological factors (e.g., herd, season, parity and stage of lactation) affecting milk CLA content and DI, and determine appropriate correction factors, if needed; ii) to estimate heritability of milk CLA content and DI in the study populations; iii) to implement a total genome scan for QTL affecting milk CLA VA content and DI in the two study populations. using a selective DNA pooling approach based on milk samples for the initial scan, followed by individual genotyping to confirm suggestive QTL regions. For each of the studied populations,, the research includes determination of CLA,VA and DI for more than 2500 individuals of five large sire half-sib families (for the genome scan) and an additional 400 individuals of 20 small sire half-sib families for the heritability analysis. Milk fat is extracted and transmethylated according to Chouinard et al. (1999). Fatty acid methyl esters are analyzed by GC-FID with a highly polar 100 m SP-2560 column, using GLC-60 supplemented with CLA and VA as a standard. Based on the results obtained to date for the Italian Brown Swiss population, the mean (fatty acid composition over the total fatty acid) \ub1SD(minimum and maximum) are respectively: VA, 1.97\ub10.77 (0.63 - 5.40); CLA, 0.63\ub1.0.47 (0.35 - 5.31); DI, 0.25\ub10.097 (0.063 - 0.64). The means for VA and CLA content found are similar to those reported by other studies (control treatment) and reviewed by Collomb et al (2006). The slightly larger variability here reported, anyhow within the limit of values found in literature, is possibly affected by the wide farming conditions of the individuals sampled