Milk production declines as dairy cows enter late lactation, resulting in reduced milk quality and negatively impacting milk processability, such as rennet coagulation time (RCT), milk pH and ethanol stability (ES), leading to seasonality issues for milk processors. Multispecies forages, containing grass, legume and herb species, require lower N inputs and are of interest to dairy farmers. However, little is known about the effect of grazing multispecies forages on milk processability characteristics in late lactation dairy cows. Forty-five autumn-calving dairy cows in late lactation were allocated to 1 of 3 grazing forages; perennial ryegrass (PRG; Lolium perenne), perennial ryegrass and white clover (Trifolium pratense) (PRGWC), and a 6 – species multispecies forage (MULTI) containing perennial ryegrass, timothy (Phleum pratense), white clover, red clover (Trifolium repens), chicory (Cichorium intybus) and plantain (Plantago lanceolata). Cows were allocated 12 kg DM grazed forage and supplemented with a grass – silage TMR and concentrate. Forage DMI was significantly lower for cows grazing PRG. Milk yield increased when cows grazed PRGWC (18.07 kg/d) and MULTI (17.84 kg/d) compared to PRG (16.08 kg/d). Milk RCT (mins) and ES (%) were unaffected by treatment. However, offering cows PRGWC and MULTI increased the concentration of C18:2 cis – 9, 12 and C18:3 cis – 9, 12, 15 in milk compared to PRG. Compared to PRG, grazing forages containing clover and herb species improved milk yield and beneficially altered milk fatty acid profile in late lactation dairy cows without negatively impacting milk processability.

This research paper analyzes the stability of raw cow milk in the alcohol test and seeks to understand to know the factors that influence milk stability and the occurrence of unstable non-acid milk. Milk samples were collected from the cooling tanks of rural farmers in the state of Paraná twice in summer and twice in winter. The farms were classified according to the production system: pasture with supplementation and feedlot. The following variables were analyzed: stability in the alcohol test, titratable acidity, ionized calcium concentration (iCa), chemical composition of milk, somatic cell count and standard plate count. The results showed that milk stability was greater in winter vs. summer, when the milk contained higher iCa, and in the feedlot vs. pasture system. The Pearson Correlation between variables (ethanol stability, milk composition, iCa, cooling tank temperature, milk volume, number of milking, number of cows milked, fat/protein ratio, distance and travel time) were analyzed. Stability was negatively correlated with iCa concentration and positively with lactose content. Logistic regression of the risk of unstable non-acid milk at 72% alcohol (UNAM72) showed that only iCa and lactose were determinants, while evaluation of the same risk at 78% alcohol revealed iCa, titratable acidity, lactose and milk urea nitrogen as risk factors. Under the dairy farming conditions of Paraná state, the frequency of UNAM72 was low (12.16%) and was higher in summer and in pasture systems with supplementation. In conclusion, in dairy herds bred with high technological level, with adequate nutritional and health management, the frequency of UNAM is low and is related to nutritional management abnd, perhaps, heat stress, factors that alter iCa and lactose levels.

This research communication was designed to evaluate the effects of different levels of diet restriction on the composition and ethanol stability (MES) of raw bovine milk. This research was carried out using three electronic databases: Scopus, Pubmed and Web of Science. The main inclusion criteria were: (i) original research, (ii) use of alcohol (ethanol) test as a method to assess milk stability, (iii) measure different levels of feed restriction and (iv) allow access to the raw data of articles. Of the nine publications that addressed the subject filtered by the systematic review, seven fitted the selection criteria and were selected to perform the meta-analysis. Feed restriction (reduction of 20, 30, 40 and 50% of the dietary dry matter offered) decreased (P < 0.01) milk yield (−18%), ethanol stability (−5%), acidity (−4%), protein (−3%) and lactose (−2%) concentrations, but did not affect the values of pH, density, fat and total solids concentrations, nor somatic cell count. The correlation between milk yield and MES was low but positive and numerically higher in the control group compared with the restriction group. The milk of cows fed the control diet presented greater ethanol stability (76.5%) compared with milk of cows fed the restrictive diet (72.8%). This decrease by up to 4 percentage units due to restriction levels ranging from 20 to 50% of diet intake may cause limitations in milk processing at the dairy industry, increasing milk rejection.

The study investigated the seasonal changes in the compositional, physicochemical and processing characteristics of milk from a mixed-herd of spring- and autumn-calving cows during the year 2014–2015. The volume proportion of autumn-calving milk (% of total milk) varied with season, from ~10–20 in Spring (March–May), 5–13 in Summer (June–August), 20–40 in Autumn (September–November) and 50–100 in Winter (December–February). While all characteristics varied somewhat from month to month, variation was inconsistent, showing no significant trend with progression of time (year). Consequently, season did not significantly affect many parameters including concentrations of total protein, casein, whey protein, NPN, total calcium, pH, rennet gelation properties or heat stability characteristics. However, season had a significant effect on the concentrations of total P and serum P, levels of αs1- and β-caseins as proportions of total casein, casein micelle size, zeta potential and ethanol stability. The absence of a significant effect of season for most compositional parameters, rennet gelation and heat-stability characteristics suggest that milk from a mixed-herd of spring- and autumn-calving cows is suitable for the manufacture of cheese and milk powder on a year-round basis, when the volume proportion of autumn milk, as a % of total, is similar to that of the current study.

Sediment formation was investigated during UHT treatment of goats' milk, subjected to indirect treatment at 140°C for 2 s, with upstream homogenisation. Stabilisers evaluated were sodium hexametaphosphate (SHMP), trisodium citrate (TSC), disodium hydrogen orthophosphate (DSHP), and sodium dihydrogen orthophosphate (SDHP). With no added stabiliser, goats' milk produced a heavy sediment on UHT treatment. Addition of SDHP reduced pH, had little effect on ionic calcium and did not substantially reduce sediment. However, addition of SHMP, DSHP and TSC each reduced ionic calcium, increased ethanol stability and reduced sediment. Following stabiliser additions, there was a good correlation between ethanol stability and ionic calcium (R2=0·85) but not between ethanol stability and pH (R2=0·08). Overall, reducing ionic calcium reduced the amount of sediment formed for all these three stabilisers, although there was no single trend line between sediment formation and ionic calcium concentration. Sediment formation was not well correlated with pH for TSC or for SHMP, but it was for DSHP, making it the only stabiliser where sediment formation correlated well both with ionic calcium and pH, which might account for its effectiveness at higher ionic calcium levels. Sediment was much reduced when the temperature was reduced from 140°C to 125°C and 114°C. There were no further changes in sediment on storage for two weeks. Analysis of the sediment showed that it was predominantly fat and protein, with a mass ratio ranging between 1·43:1 and 1·67:1. Its mineral content was usually less than 5% of dry weight. The maximum amounts of P and Ca were found to be 2·32% and 1·63%, respectively.

The effects of minerals on casein micelle stability of individual cows' milk, throughout a complete lactation, were investigated. Calcium and calcium ions, magnesium, phosphorus, sodium, potassium and citrate contents were analysed, together with the following physical properties of milk; pH, ethanol stability, rennet clotting time and coagulum firmness. There was an inverse non-linear relationship between free calcium ion concentration and ethanol stability (ES; r=0·84). Rennet coagulation time showed a weaker relationship with free calcium ion concentration (r=0·44) but a stronger relationship with pH (r=0·66). In addition, samples containing higher amounts of free calcium ions produced a firmer gel. Citrate in natural samples acts as a stabilizing factor, as it slightly improves milk stability. Potassium, on the other hand, exhibited a negative correlation, but only with rennet clotting time (r=−0·52). Throughout lactation the average values were; free Ca2+ concentration 1·88 mM, pH 6·63, ES 83·2% and clotting time 13·6 min. The equilibrium relationship between pH and free Ca2+ concentration was investigated by adjusting milk pH from 5·9 to 7·1, using acid and alkali. There was a good inverse linear relationship between pH and log (free Ca2+) for individual milk samples, with a gradient of −0·62 and a standard deviation of 0·042.

The objective of the present work was to identify the compositional parameters of raw milk that affected ethanol stability at natural pH when natural milk conditions were not modified. Heat stability, measured as coagulation time (CT), was included in the analysis to verify relation to alcohol test. Statistical models were proposed for alcohol and heat (CT) stabilities. Milk samples of good hygienic quality from dairy farms were classified in two groups according to their alcohol stability. Unstable samples to ethanol (72%, v/v) presented lower values of pH, somatic cells count, casein and non-fat-solids relative to ethanol stable samples (ethanol at 78%, v/v or more); whereas freezing point, chloride, sodium and potassium concentrations were higher in the unstable group. Logistic regression and multiple regression were applied to modelling alcohol and heat stability behaviour respectively. Chloride, potassium, ionic calcium and somatic cell count were included in the alcohol regression model, whereas calcium, phosphorous, urea, pH and ionic calcium were part of CT model. Ionic calcium was the only measured variable that contributed to both models; however coagulation time was noted to be more sensitive to ionic calcium than alcohol. The relation between ionic strength and casein was found to contribute to the alcohol model but not to the CT model. However, the interaction calcium plus magnesium plus phosphorous and casein contributed only to CT model.

Two main genetic variants of κ-casein, A and B, are found in Holstein cows. A positive association between the κ-casein B genetic variant and milk characteristics of economic importance have been reported (reviews: Creamer & Harris, 1997; Ng-Kwai-Hang, 1998). This can be explained, at least in part, by a higher κ-casein content of the casein in milk of cows having the κ-casein B genetic variant (Donnelly et al. 1984; Law, 1993). We have recently reported the presence of a differential allele-specific expression of the κ-casein gene in Holstein cows by comparing the content of allele-A and allele-B specific mRNA in the mammocytes of lactating cows genotyped κ-casein AB (Robitaille & Petitclerc, 2000). For some cows, the A- and B-specific κ-casein gene alleles were expressed in a similar manner. These cows are named HH here to indicate that they were homozygous for κ-casein gene expression. The other group of cows, cows HL, presented a differential allele specific expression of the κ-casein gene allele B which was overexpressed compared to allele A. The genetic polymorphism governing this differential allele-specific expression of the κ-casein gene is likely to affect the physico-chemical properties of casein micelles and, hence, the technological properties of milk, as κ-casein is considered to be the stabilizing component of the milk micelles. The objective of the study was to evaluate the effect of this expression polymorphism of the κ-casein gene on milk ethanol stability.