R. Dal Zotto

Prediction of coagulation properties, titratable acidity, and pH of bovine milk using mid-infrared spectroscopy

This study investigated the potential application of mid-infrared spectroscopy (MIR 4,000-900 cm(-1)) for the determination of milk coagulation properties (MCP), titratable acidity (TA), and pH in Brown Swiss milk samples (n = 1,064). Because MCP directly influence the efficiency of the cheese-making process, there is strong industrial interest in developing a rapid method for their assessment. Currently, the determination of MCP involves time-consuming laboratory-based measurements, and it is not feasible to carry out these measurements on the large numbers of milk samples associated with milk recording programs. Mid-infrared spectroscopy is an objective and nondestructive technique providing rapid real-time analysis of food compositional and quality parameters. Analysis of milk rennet coagulation time (RCT, min), curd firmness (a(30), mm), TA (SH degrees/50 mL; SH degrees = Soxhlet-Henkel degree), and pH was carried out, and MIR data were recorded over the spectral range of 4,000 to 900 cm(-1). Models were developed by partial least squares regression using untreated and pretreated spectra. The MCP, TA, and pH prediction models were improved by using the combined spectral ranges of 1,600 to 900 cm(-1), 3,040 to 1,700 cm(-1), and 4,000 to 3,470 cm(-1). The root mean square errors of cross-validation for the developed models were 2.36 min (RCT, range 24.9 min), 6.86 mm (a(30), range 58 mm), 0.25 SH degrees/50 mL (TA, range 3.58 SH degrees/50 mL), and 0.07 (pH, range 1.15). The most successfully predicted attributes were TA, RCT, and pH. The model for the prediction of TA provided approximate prediction (R(2) = 0.66), whereas the predictive models developed for RCT and pH could discriminate between high and low values (R(2) = 0.59 to 0.62). It was concluded that, although the models require further development to improve their accuracy before their application in industry, MIR spectroscopy has potential application for the assessment of RCT, TA, and pH during routine milk analysis in the dairy industry. The implementation of such models could be a means of improving MCP through phenotypic-based selection programs and to amend milk payment systems to incorporate MCP into their payment criteria.

Reproducibility and Repeatability of Measures of Milk Coagulation Properties and Predictive Ability of Mid-Infrared Reflectance Spectroscopy

The objectives of the study were to estimate the reproducibility and repeatability of milk coagulation properties (MCP) measured by a computerized renneting meter (CRM) and to evaluate the predictive ability of mid-infrared spectroscopy (MIRS) as an innovative technology for the assessment of rennet coagulation time (RCT, min) and curd firmness (a(30), mm). Four samples without addition of preservative (NP) and 4 samples with Bronopol addition (PS) were collected from each of 83 Holstein-Friesian cows. Six hours after collection, 2 replicated measures of MCP were obtained with CRM using 1 NP and 1 PS sample from each cow. Mid-infrared spectra of the remaining NP and PS samples from each animal were recorded after 6 h, 4 d, and 8 d after sampling. Two groups of calibration equations were developed using MIRS spectra and CRM measures of MCP as reference data obtained from analysis of NP and PS, respectively. Reproducibility and repeatability of CRM measures were obtained from REML estimation of variance components on the basis of a linear model including the fixed effects of herd and days in milk class and the random effects of cows, sample treatment (addition or no addition of preservative), and the interaction between cow and sample treatment. Coefficient of reproducibility is an indicator of the agreement between 2 measurements of MCP for the same milk sample preserved with or without addition of Bronopol. Coefficient of repeatability is an indicator of the agreement between repeated measures of MCP. Pearson correlations between MCP measures for NP and PS were 0.97 and 0.83 for RCT and a(30), respectively. Reproducibility of CRM measures under different preserving conditions of milk was 93.5% for RCT and 64.6% for a(30). Repeatabilities of RCT and a(30) measures were 95.7 and 77.3%, respectively. Based on the estimated cross-validation standard errors and coefficients of determination and ratios of standard errors of cross-validation to standard deviation of reference data, the predictive ability of MIRS calibration equations was moderate for RCT and unsatisfactory for a(30.) Predictive ability of equations based on spectra and MCP measures of PS was greater than that of equations based on data of NP. The study did not provide conclusive evidence on the effectiveness of MIRS as a predictive tool for MCP and it requires an enlargement of the variability of milk sampling circumstances. Because the relevance of MIRS predictions in relation to breeding programs for MCP based on indicator traits relies on the genetic variation of MIRS predictions and on phenotypic and genetic correlations between MIRS predictions and MCP measures, additional specific investigations on these topics are needed.

Effect of Holstein Friesian and Brown Swiss Breeds on Quality of Milk and Cheese

In Italy, more than 75% of milk is used for cheese making. For this reason, milk composition and coagulation traits and cheese quality represent the most important tools for the economic development of the dairy sector. In particular, cheese quality varies in relation to cheese-making technology and breed of cow. The aim of this study was to investigate the effect of 3 types of milk, originating from Holstein-Friesian (HF), Brown Swiss (BS), and mixed of both breeds, on vat milk characteristics, cheese yield, and quality in 3 different typical Italian cheese-making conditions (Casolet, Vezzena, and Grana Trentino). One hundred forty-four cows (66 HF and 78 BS) were involved, and a total of 24 vats of milk were evaluated. At maturity, 30, 21, and 16 wheels of Casolet, Vezzena, and Grana Trentino cheese were analyzed. Brown Swiss cows yielded 9% less milk per day than HF cows, but milk showed greater contents of protein, casein, titratable acidity, and better rennet coagulation time and curd firmness than HF milk. The chemical composition and cholesterol content of the 3 types of cheese were similar between breeds, whereas the cheese made with BS milk showed greater contents of monounsaturated and polyunsaturated fatty acids. Cheese made with BS milk had greater b* (yellow component) than HF. Cheese yield, recorded at different ripening times, demonstrated that BS milk yielded more cheese than HF. Mixed milk showed values, on average, intermediate to HF and BS milk characteristics, and this trend was confirmed in cheese yield at different ripening times.

Genetic parameters for conjugated linoleic acid, selected milk fatty acids, and milk fatty acid unsaturation of Italian Holstein-Friesian cows.

The objective of this study was to estimate genetic parameters for conjugated linoleic acid (CLA) and other selected milk fatty acid (FA) content and for unsaturation ratios in the Italian Holstein Friesian population. Furthermore, the relationship of milk FA with milk fat and protein content was considered. One morning milk sample was collected from 990 Italian Holstein Friesian cows randomly sampled from 54 half-sib families, located in 34 commercial herds in the North-eastern part of Italy. Each sample was analyzed for milk percentages of fat and protein, and for single FA percentages (computed as FA weight as a proportion of total fat weight). Heritabilities were moderate for unsaturated FA, ranging from 0.14 for C16:1 to 0.19 for C14:1. Less than 10% of heritability was estimated for each saturated FA content. Heritability for index of desaturation, monounsaturated FA and CLA/trans-11 18:1 ratio were 0.15, 0.14, and 0.15, respectively. Standard errors of the heritability values ranged from 0.02 to 0.06. Genetic correlations were high and negative between C16:0 and C18:0, as well as between C14:0 and C18:0. Genetic correlations of index of desaturation were high and negative with C14:0 and C16:0 (-0.70 and -0.72, respectively), and close to zero (0.03) with C18:0. The genetic correlation of C16:0 with fat percentage was positive (0.74), implying that selection for fat percentage should result in a correlated increase of C16:0, whereas trans-11 C18:1 and cis-9, trans-11 C18:2 contents decreased with increasing fat percentage (-0.69 and -0.55, respectively). Genetic correlations of fat percentage with 14:1/14 and 16:1/16 ratios were positive, whereas genetic correlations of fat percentage with 18:1/18 and CLA/trans-11 18:1 ratios were negative. These results suggest that it is possible to change the milk FA composition by genetic selection, which offers opportunities to meet consumer demands regarding health aspects of milk and dairy products.

Effects of Composite β- and κ-Casein Genotypes on Milk Coagulation, Quality, and Yield Traits in Italian Holstein Cows

The aim of the study was to estimate the effect of the composite CSN2 and CSN3 genotypes on milk coagulation, quality, and yield traits in Italian Holstein cows. A total of 1,042 multiparous Holstein cows reared on 34 commercial dairy herds were sampled once, concurrently with monthly herd milk recording. The data included the following traits: milk coagulation time; curd firmness; pH and titratable acidity; fat, protein, and casein contents; somatic cell score; and daily milk, fat, and protein yields. A single-trait animal model was assumed with fixed effects of herd, days in milk, parity, composite casein genotype of CSN2 and CSN3 (CSN2-CSN3), and random additive genetic effect of an animal. The composite genotype of CSN2-CSN3 showed a strong effect on both milk coagulation traits and milk and protein yields, but not on fat and protein contents and other milk quality traits. For coagulation time, the best CSN2-CSN3 genotypes were those with at least one B allele in both the CSN2 and CSN3 loci. The CSN3 locus was associated more strongly with milk coagulation traits, whereas the CSN2 locus was associated more with milk and protein yields. However, because of the tight linkage between the 2 loci, the composite genotypes, or haplotypes, are more appropriate than the single-locus genotypes if they were considered for use in selection.

Association Between a Polymorphism at the Stearoyl-CoA Desaturase Locus and Milk Production Traits in Italian Holsteins

Associations between stearoyl-CoA desaturase (SCD) gene polymorphisms and milk production traits (milk, fat, and protein yields, fat and protein contents, somatic cell score) were investigated on a sample of 701 lactations of 313 Italian Holsteins. Test-day records (5,097) were analyzed with a mixed linear model that included the fixed effects of herd, date of test, parity, genotype at the SCD locus, and lactation interval nested within SCD genotype, and the random effect of cow. An effect of the SCD genotype on milk and protein yields was detected, with VV cows producing more milk (about 2 kg/d) and protein (about 0.07 kg/d) compared with AA cows. The contribution of the SCD locus to the phenotypic variance of the 2 traits was about 0.015. These results suggest a possible use of the SCD locus in gene-assisted selection programs for the improvement of milk production traits in dairy cattle, although large-scale studies in different breeds are required.

Short communication: Influence of composite casein genotypes on additive genetic variation of milk production traits and coagulation properties in Holstein-Friesian cows

The aim of the study was to quantify the effects of composite beta- and kappa-casein (CN) genotypes on genetic variation of milk coagulation properties (MCP); milk yield; fat, protein, and CN contents; somatic cell score; pH; and titratable acidity (TA) in 1,042 Italian Holstein-Friesian cows. Milk coagulation properties were defined as rennet coagulation time (RCT) and curd firmness (a(30)). Variance components were estimated using 2 animal models: model 1 included herd, days in milk, and parity as fixed effects and animal and residual as random effects, and model 2 was model 1 with the addition of composite beta- and kappa-CN genotype as a fixed effect. Genetic correlations between RCT and a(30) and between these traits and milk production traits were obtained with bivariate analyses, based on the same models. The inclusion of casein genotypes led to a decrease of 47, 68, 18, and 23% in the genetic variance for RCT, a(30), pH, and TA, respectively, and less than 6% for other traits. Heritability of RCT and a(30) decreased from 0.248 to 0.143 and from 0.123 to 0.043, respectively. A moderate reduction was found for pH and TA, whereas negligible changes were detected for other milk traits. Estimates of genetic correlations were comparable between the 2 models. Results show that composite beta- and kappa-CN genotypes are important for RCT and a(30) but cannot replace the recording of MCP themselves.

Use of crossbreeding with beef bulls in dairy herds: effect on age, body weight, price, and market value of calves sold at livestock auctions.

The aim of this study was to investigate the effect of different breeds and breed crosses on age (AC, d), BW (kg), price (PR,

Genetic characterization of the Burlina cattle breed using microsatellites markers.

/kg), and market value (MV,

Breed assignment test in four Italian beef cattle breeds

/calf) of purebred and crossbred calves sold for veal and beef production. The Kovieh wholesale cattle organization (Bolzano, Italy) grouped calves from several dairy herds located in the Trentino-Südtirol region in Italy and sold them by public auctions. Data on AC, BW, PR, and MV from 96,458 calves were recorded from January 2003 to December 2007 and consisted of 4 pure breeds [2 dairy, Brown Swiss (BS) and Holstein-Friesian (HF); and 2 dual-purpose, Simmental (SI) and Alpine Grey (AG)], and 8 crossbreds by crosses of Limousin (LI) and Belgian Blue (BB) with the 4 dam breeds. Least squares means for AC, BW, PR, and MV were calculated for breeds and breed crosses with a model that included fixed effects of herd of birth, age (except for AC), sex, and breed of the calf, year and season of auction, and interactions between the main effects. The coefficients of determination of the models were 0.41, 0.51, 0.84, and 0.82 for AC, BW, PR, and MV, respectively. Sex, age, and breed were the most relevant sources of variation for BW (P < 0.001), whereas breed and sex were the most important sources of variation for AC, PR, and MV (P < 0.001). Also, PR and MV were significantly influenced (P < 0.01) by all the effects included in the model, except for season x age interaction in the case of MV. Market value of male was greater (P < 0.001) than that of female calves, with the exception of BS (-