G. Niero

Phenotypic characterisation of milk technological traits,protein fractions,and major mineral and fatty acid composition of Burlina cattle breed

Abstract The aim of the present study was to characterise milk of Burlina local cattle breed for traits of technological and nutritional relevance, such as milk coagulation properties (MCP), and protein, major mineral and fatty acid (FA) composition. Burlina is mainly reared in mountain areas of Veneto Region (Italy) and it has been inserted in conservation plans aiming to avoid biodiversity loss and marginal pasture areas abandonment. Eighty-one individual milk samples were collected in four farms. Milk coagulation properties were determined using Formagraph, and protein, mineral and FA composition were analysed in high performance liquid chromatography, inductively coupled plasma optical emission spectrometry and gas chromatography, respectively. Results evidenced good protein percentage (3.38%) and considerable casein content (28.89 mg/mL), as well as a desirable FA profile, with ω-6 to ω-3 ratio of 4.04. Somatic cell score, averaging 3.13, is a trait that should be enhanced through the improvement of farm management. This would have positive effects on MCP. Among milk minerals, the most and less abundant were K (1493.53 mg/kg) and Mg (110.07 mg/kg), respectively. Overall, herd, parity and lactation stage explained moderate to low variation of the studied traits. Results of the present study could be useful to valorise Burlina local breed and preserve biodiversity in marginal areas.

Short communication: characterization of soluble thiols in bovine milk.

Antioxidants are molecules essential for the maintenance of cell homeostasis and their intake through the diet has positive effects on human health. Among antioxidants, low-molecular-weight (LMW) thiols represent an important class of compounds. The aim of this study was to identify LMW thiols in bovine milk. A total of 96 individual milk samples from Brown Swiss, Holstein-Friesian, Alpine Grey, and Simmental cattle breeds were collected in 8 herds. The LMW thiols were extracted from the soluble fraction of milk and, following a derivatization protocol, they were separated by reverse phase HPLC and detected fluorimetrically. Six thiol species were detected and 2, glutathione (GSH) and cysteine-glycine (Cys-Gly), were identified and quantified. Regardless of the breed, the average concentration of Cys-Gly in milk was greater than that of GSH. Overall, milk from dual-purpose breeds (Simmental and Alpine Grey) was richer in LMW thiols than milk from dairy cows (Holstein-Friesian and Brown Swiss). Glutathione and Cys-Gly, closely linked metabolically, were strongly correlated. Pearson correlations of Cys-Gly with protein and casein contents were moderately low, and no relationship was found between GSH and milk chemical composition. Future research should focus on the identification of all detected LMW thiol species.

Development and validation of a near infrared spectrophotometric method to determine total antioxidant activity of milk

In the present study a spectrophotometric method for the determination of total antioxidant activity (TAA) based on ABTS assay was developed and validated on raw milk (RM), whole UHT milk (WUM), partially skimmed UHT milk (SUM), whole pasteurised milk (WM) and partially skimmed pasteurised milk (SM). The most suitable solvent for antioxidant extraction was 80% acetone. Regardless of the type of milk, the coefficient of determination from the linearity test was greater than 0.95. The limit of detection ranged from 0.74 to 6.07μmoll-1 Trolox equivalents. Repeatability, calculated as relative standard deviation of twenty measurements within a day, and reproducibility, calculated as relative standard deviation of sixty measurements across three days, ranged from 1.24 to 4.04% and from 2.18 to 3.52%, respectively. Preservative added to RM had negligible effects on the TAA of milk. The greatest TAA was measured for SM followed by SUM, RM, WM and WUM.

Short communication: Selecting the most informative mid-infrared spectra wavenumbers to improve the accuracy of prediction models for detailed milk protein content

The objective of this study was to investigate the ability of mid-infrared spectroscopy (MIRS) to predict protein fraction contents of bovine milk samples by applying uninformative variable elimination (UVE) procedure to select the most informative wavenumber variables before partial least squares (PLS) analysis. Reference values (n=114) of protein fractions were measured using reversed-phase HPLC and spectra were acquired through MilkoScan FT6000 (Foss Electric A/S, Hillerød, Denmark). Prediction models were built using the full data set and tested with a leave-one-out cross-validation. Compared with MIRS models developed using standard PLS, the UVE procedure reduced the number of wavenumber variables to be analyzed through PLS regression and improved the accuracy of prediction by 6.0 to 66.7%. Good predictions were obtained for total protein, total casein (CN), and α-CN, which included αS1- and αS2-CN; moderately accurate predictions were observed for κ-CN and total whey protein; and unsatisfactory results were obtained for β-CN, α-lactalbumin, and β-lactoglobulin. Results indicated that UVE combined with PLS is a valid approach to enhance the accuracy of MIRS prediction models for milk protein fractions.

Technical note: Development and validation of a new method for the quantification of soluble and micellar calcium, magnesium, and potassium in milk

Milk mineral content is a key trait for its role in dairy processes such as cheese-making, its use as source of minerals for newborns, and for all traits involving salt-protein interactions. This study investigated a new method for measuring mineral partition between soluble and micellar fractions in bovine milk after rennet coagulation. A new whey dilution step was added to correct the quantification bias due to whey trapped in curd and excluded volume. Moreover, the proposed method allowed the quantification of the diffusible volume after milk coagulation. Milk mineral content and concentration in whey, and diluted whey were quantified by acid digestion and inductively coupled plasma optical emission spectrometry. The repeatability of the method for micellar Ca, Mg, and K was between 2.07 and 8.96%, whereas reproducibility ranged from 4.01 to 9.44%. Recovery of total milk minerals over 3 spiking levels ranged from 92 to 97%. The proposed method provided an accurate estimation of micellar and soluble minerals in milk, and curd diffusible volume.

Phenotypic characterisation of major mineral composition predicted by mid-infrared spectroscopy in cow milk

Abstract Population-level phenotyping is, for some traits, hardly achievable due to limitation of reference analyses. Mid-infrared spectroscopy (MIRS) is a quick and cost-effective laboratory technique allowing the prediction of innovative milk quality features on a large scale. The present study aimed at investigating factors associated with milk Ca, K, Mg, Na and P contents predicted by MIRS models on a large multi-breed spectral data set of 123,240 test-day records. Two dairy (Holstein–Friesian and Brown Swiss) and two dual-purpose (Simmental and Alpine Grey) cattle breeds were considered. Sources of variation of predicted milk mineral contents were studied using linear mixed models, including the fixed effects of breed, month of sampling, stage of lactation, parity and interactions between the main effects. Random factors were herd nested within breed, cow nested within breed and the residual. Calcium content was greater in milk of dual-purpose than dairy cattle breeds. Simmental cows produced milk with the greatest content of Ca and Na, and milk of Holstein-Friesian had the lowest P content. Variation of content of Ca, Mg, Na and P throughout lactations exhibited an opposite trend to that of milk yield, with the lowest values around the peak of lactation. On the other hand, K content mirrored the trend of milk yield. Multiparous cows had lower content of milk minerals, with the exception of Na, compared with first parity animals. Environmental factors identified in the present study can be considered for within-breed genetic evaluation to adjust records of milk mineral contents for these effects.

Technical note: Development and validation of an HPLC method for the quantification of tocopherols in different types of commercial cow milk

In the present study, a methanol-fluorescence-based HPLC method was validated for its use to quantify α-tocopherol and γ-tocopherol in raw milk, whole UHT milk, partially skimmed UHT milk, whole pasteurized milk, and partially skimmed pasteurized milk. Repeatability and reproducibility, calculated as relative standard deviation of 10 measurements within the same day and 30 measurements across 3 d, respectively, were always below 5% for both tocopherols concentrations and retention times. Recovery was assessed through 3 spiking levels and it ranged from 89 to 107%. The method was able to detect the expected declines in tocopherols in milk exposed to UHT or skimming treatments. Vitamin E, calculated as the sum of α-tocopherol and γ-tocopherol, was similar in whole pasteurized and raw milk, averaging 1.57 and 1.56 mg/L, respectively, followed by whole UHT (1.33 mg/L), partially skimmed pasteurized (0.77 mg/L), and partially skimmed UHT milk (0.61 mg/L).

Short communication: Phenotypic characterization of total antioxidant activity of buffalo, goat, and sheep milk

Free radicals are reactive and unstable waste molecules produced by cells, responsible of damages and alteration on DNA, proteins, and fat. The daily intake of antioxidant compounds, acting against free radicals and their detrimental effects, is essential for human health. Milk contains several compounds with antioxidant activity, and the sum of their reducing potential blocking free radicals development is defined as total antioxidant activity (TAA). This novel trait has been described in literature both in individual and bulk cow milk, but there are no reports from other dairy species. Therefore, the present study aimed to investigate phenotypic variation of TAA in individual samples of buffalo (n = 105), goat (n = 112), and sheep (n = 198) milk. Total antioxidant activity was measured through a reference spectrophotometric method, and expressed as millimoles per liter of Trolox equivalents (TE). The greatest TAA was observed in sheep milk, averaging 7.78 mmol/L of TE and showing also the broadest phenotypic variation expressed as coefficient of variation (13.98%). Significantly lower TAA values were observed for buffalo (7.35 mmol/L of TE) and goat (6.80 mmol/L of TE) milk, with coefficients of variation of 8.18 and 8.47%, respectively. Total antioxidant activity exhibited weak correlations with milk yield and chemical composition. Phenotypic values of TAA presented in this study will be used to assess the ability of mid-infrared spectroscopy to predict this new trait and thus to collect data at the population level.

Effectiveness of mid-infrared spectroscopy to predict bovine milk minerals

Carbohydrates are not the only macronutrients triggering insulin release following food intake. Besides other components, leucine (Leu) has been demonstrated to induce insulin secretion in humans and in laboratory rodents. We hypothesized that Leu stimulates the release of insulin in dairy cows, and thus our objective was to test the effects of a single-dose of Leu infused intraduodenally on the concentrations of insulin, glucose and free amino acids (AA) in blood plasma as compared to infusions with either glucose or saline. Six duodenum-fistulated Holstein cows were studied in a replicated 3 × 3 Latin square design with 3 periods of 7 d, in which the treatments were applied at the end of each period. The treatments were duodenal bolus infusions of Leu (DIL; 0.15 g/kg BW), glucose (DIG; at Leu equimolar dosage) or saline (SAL). Blood samples were taken at -15, 0, 10, 20, 30, 40, 50, 60, 75, 90, 120, 180, 210, 240 and 300 min relative to the infusion and the concentrations of insulin, glucose and AA were determined in plasma. In DIG, insulin and glucose concentrations peaked at 30-40 and 40-50 min after the infusion, respectively. Insulin concentrations were greater (P<0.05) from 30-50 min in DIG than DIL and SAL. In DIG, glucose concentrations were greater (P≤0.01) from 30-75 and 40-50 min than in DIL and SAL, respectively. In DIL, Leu concentrations peaked 50-60 min after infusion, reaching 20 and 15-fold greater values than that in DIG and SAL, respectively. The plasma concentrations of total AA minus Leu were affected by treatment (P<0.0001), resulting in lowest mean concentrations of total AA minus Leu in DIL, followed by DIG and SAL. The data suggest that Leu infusion did not elicit an apparent insulin response, but may stimulate the tissue uptake of AA by mechanisms yet to be elucidated.Breeding goals of Holstein dairy cattle in New Zealand (NZL) focus on traits reflecting adaptation to pasture-based systems. Due to high prices for concentrates, and advantages for cattle health and welfare, low input grazing systems become important in regions of North-West Germany. The present study addresses the hypothesis that progeny of NZL-Holstein sires are superior in 30 German grassland farms compared to offspring of Holstein sires being progeny tested in German indoor systems. A research design was implemented to create three different genetic groups (F1 generation) within herds on the basis of a German Holstein cow (GHC) population: Group 1=GHC x NZL sires, group 2=GHC x GH sires, group 3=GHC x GH_pasture sires. GH_pasture sires represent bulls of German origin with high breeding values for the traits being important in NZL. Group comparison focused on the full set of production and functional traits from official recording systems, and in addition on further novel traits reflecting cow health and welfare: Scores for body condition (BCS), locomotion (LOCS), hock lesions (HLS), and total hygiene (THS). Linear and generalized linear mixed models were applied to estimate group differences for a longitudinal data structure (2998 observations). In parity 1, daughters of NZL sires had the highest LSMean for BCS (2.56), and lowest LSMean for LOCS (0.10), HLS (0.25) and THS (3.67), reflecting an enhanced robustness of HF strains from NZL. Within breed genetic analyses simultaneously considering all genetic groups revealed a moderate genetic background with the following heritabilities: BCS (0.25), LOCS (0.12), HLS (0.04), and THS (0.17). Genotype by environment interactions between pasture-based and indoor systems were studied by applying multiple trait models. For all traits, rg were smaller than 0.80, especially indicating GxE interactions for low heritability functional traits.