Properties of sodium caseinate as affected by the ß-casein phenotypes.

The aim of the study was to investigate the properties of sodium caseinate dispersions and oil-in-water emulsions obtained from cows' milk of either A1/A1, A1/A2, or A2/A2 ß-casein phenotype. Protein structural characterisation was examined using Fourier Transform Infrared and Nuclear Magnetic Resonance spectroscopies, with physicochemical and interfacial properties assessed by analysing adsorbed protein content, hydrophobicity, solubility, and emulsion stability of the samples. Results showed variations in the secondary structure of all samples dependent of the presence of A1 or A2 ß-caseins. The main differences included greater amounts of α-helix and ß-sheet in A1/A1 and A1/A2 sodium caseinate dispersions that influenced their lower solubility, while random coils/polyproline II helixes were found only in A2/A2 sodium caseinate dispersion. In contrast, upon adsorption on the interface of A2/A2 sodium caseinate emulsion, the protein adopted ordered conformational motifs. This conformational shift supposedly arose from structural differences between the two ß-casein proteoforms, which most likely enhanced the emulsion properties of A2/A2 sodium caseinate compared to either A1/A1 or A1/A2 sodium caseinates. The A2 ß-casein in both, A1/A2 and A2/A2 sodium caseinates, appears to be able to more rapidly reach the oil droplet surface and was more efficient as emulsifying agent. The current results demonstrated that the conformational rearrangement of proteins upon adsorption to emulsion interfaces was dependent not only on hydrophobicity and on solubility, but also on the conformational flexibility of A1/A1, A1/A2, and A2/A2 ß-casein phenotypes. These findings can assist in predicting the behaviour of sodium caseinates during relevant industrial processing.

Prior Forage Type Influences Ruminal Responses to a Wheat Grain Challenge in Lactating Dairy Cows.

To increase the dry matter and metabolisable energy intake of cows, dairy farmers often supplement pasture with concentrates and conserved fodder. Feeding large amounts of highly fermentable concentrates to cows can result in metabolic issues, such as ruminal acidosis, and thus safer but more efficient introduction strategies are desirable. We assessed the role that forages play in ruminal, behavioural and production responses to a wheat grain challenge in dairy cows with no previous wheat adaptation. Multiparous lactating Holstein dairy cows (n = 16) were fed a forage-only diet of either lucerne (Medicago sativa) hay, perennial ryegrass (Lolium perenne L.) hay or one of two cultivars of zero-grazing fresh perennial ryegrass herbage (Bealey or Base), for 3 weeks. The forage diet was then supplemented with crushed wheat grain at 8 kg dry matter/cow day-1, with no adaptation period. Wheat comprised between 32 and 43% of total dry matter intake. Cows fed hay maintained a higher mean ruminal fluid pH than those fed herbage, on both the forage-only diet (6.43 vs. 6.17) and the forage plus wheat diet (6.03 vs. 5.58). Following supplementation of wheat, cows fed herbage exhibited minimum ruminal fluid pH levels indicative of acute ruminal acidosis, at 5.15 and 5.06 for cultivars Bealey and Base, respectively. Furthermore, for both herbage cultivars, adding wheat resulted in a ruminal fluid pH under 6 for >20 h/day. The ruminal environment of cows fed lucerne hay remained most stable throughout the grain challenge, spending the least amount of time below pH 6.0 (9.0 h/day). Hay created a ruminal environment that was better able to cope with the accumulation of acid as wheat was digested. A combination of increased ruminating time and a slower rate of fermentation, due to higher neutral detergent fiber and lower metabolisable energy concentrations in the hays, is likely responsible for the higher ruminal fluid pH values. Forage plays a critical role in wheat introduction strategies; aggressive adaptation strategies could be implemented when a hay such as lucerne is used as the base forage.

Economic Analysis of Offering Different Herbage Allowances to Dairy Cows Fed a Partial Mixed Ration.

The economics of grazing dairy cows offered a range of herbage allowances and fed supplements as a partial mixed ration (PMR) were examined where profit was defined as the margin between total milk income and the cost of pasture plus PMR supplement. The analysis made use of milk production and feed intake data from two dairy cow nutrition experiments, one in early lactation and the other in late lactation. In early lactation and at a PMR intake of 6 kg DM/cow per day, the profit from the cows with access to a medium herbage allowance (25 kg DM/cow per day) was AUD 1.40/cow per day higher than that for cows on a low allowance (15 kg DM/cow per day). At a higher PMR intake of 14 kg DM/cow per day, the profit from the cows on a medium herbage allowance was AUD 0.45/cow per day higher than the cows on a low allowance; there was no additional profit from increasing the herbage allowance from medium to high (40 kg DM/cow per day). In late lactation, the profit from the cows fed a PMR with a medium herbage allowance (20 kg DM/cow per day) was only higher than the cows on a low allowance (12 kg DM/cow per day) when the PMR intake was between 6 and 12 kg DM/cow per day. There was also a difference of AUD +0.50/cow per day between the PMR with medium and high herbage allowance (32 kg DM/cow per day). It was concluded that farmers who feed a PMR to dairy cows should offer at least a medium herbage allowance to optimize profit. While feeding additional PMR increases milk production and profit, further gains would be available by offering a higher herbage allowance. These findings provide an estimate of the net benefits of different herbage allowances when feeding a PMR and will enable farmers to manage their feeding systems more profitably.

Faecalibacterium diversity in dairy cow milk.

The bacterial species, Faecalibacterium prausnitzii, beneficial to humans and animals and found in mammalian and avian gut, is also occasionally found in dairy cow milk. It is one of the butyrate-producing bacteria of the colon, has anti-inflammatory properties and its abundance in the gut is negatively correlated with obesity in humans. Several strains differing in their functional capability, have been identified. It is important therefore, milk being a potential source of F. prausnitzii as a novel probiotic, to investigate the diversity of this species in bovine milk. Using 16s rRNA gene amplicons we find 292 different dereplicated Faecalibacterium-related amplicons in a herd of 21 dairy cows. The distribution of the 20 most abundant amplicons with >97% identity to a Greengenes OTU varies from cow to cow. Clustering of the 292 pooled sequences from all cows at 99.6% identity finds 4 likely Faecalibacterium phylotypes with >98.5% identity to an F. prausnitzii reference sequence. Sequence alignment and phylogenetic analysis shows these phylotypes are distinct from 34 other species from the Ruminococcaceae family and displaying the sequence clusters as a network illustrates how each cluster is composed of sequences from multiple cows. We conclude there are several phylotypes of Faecalibacterium prausnitzii (the only species so far defined for the genus) in this dairy herd with cows being inoculated with a mixture of several strains from a common source. We conclude that not only can Faecalibacterium be detected in dairy cow milk (as noted by others) but that there exist multiple different strains in the milk of a dairy herd. Therefore milk, as an alternative to faeces, offers the opportunity of discovering new strains with potential probiotic application.

Influence of acid hydrolysis, saponification and sample clean-up on the measurement of phytosterols in dairy cattle feed using GC-MS and GC with flame ionization detection.

The fortification of processed foods including dairy products is increasingly commonplace with phytosterols among many compounds used to improve the nutritional value of food products. It is also increasingly common practice for some dairy cattle feeds to be fortified for their potential to increase phytosterol levels in milk. In this study, a combined, streamlined protocol using acid hydrolysis, saponification and sample clean-up was developed to enable the rapid and reliable measurement of phytosterols. The method was developed with focus on streamlining the overall technique to make it suitable for commercial laboratories, to reduce labor and consumable costs, while maintaining accuracy. A total of 12 different feed types commonly used in the dairy industry were analyzed with the highest and lowest sterol contents found in cotton seed oil and tannin with average phytosterol contents of 256 and <30 mg per 100 g, respectively. With a limit of reporting of 30 mg/kg for individual sterols and a correlation coefficient > 0.99, the method was validated for milk to enable feed comparison studies with respect to the total phytosterol content in raw milk.

Milk protein concentration, estimated breeding value for fertility, and reproductive performance in lactating dairy cows.

Milk protein concentration in dairy cows has been positively associated with a range of measures of reproductive performance, and genetic factors affecting both milk protein concentration and reproductive performance may contribute to the observed phenotypic associations. It was of interest to assess whether these beneficial phenotypic associations are accounted for or interact with the effects of estimated breeding values for fertility. The effects of a multitrait estimated breeding value for fertility [the Australian breeding value for daughter fertility (ABV fertility)] on reproductive performance were also of interest. Interactions of milk protein concentration and ABV fertility with the interval from calving date to the start of the herd's seasonally concentrated breeding period were also assessed. A retrospective single cohort study was conducted using data collected from 74 Australian seasonally and split calving dairy herds. Associations between milk protein concentration, ABV fertility, and reproductive performance in Holstein cows were assessed using random effects logistic regression. Between 52,438 and 61,939 lactations were used for analyses of 4 reproductive performance measures. Milk protein concentration was strongly and positively associated with reproductive performance in dairy cows, and this effect was not accounted for by the effects of ABV fertility. Increases in ABV fertility had important additional beneficial effects on the probability of pregnancy by wk 6 and 21 of the herd's breeding period. For cows calved before the start of the breeding period, the effects of increases in both milk protein concentration and ABV fertility were beneficial regardless of their interval from calving to the start of the breeding period. These findings demonstrate the potential for increasing reproductive performance through identifying the causes of the association between milk protein concentration and reproductive performance and then devising management strategies to capitalize on them. Research should be conducted to understand the component of the relationship not captured by ABV fertility.

Influence of pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt.

The influence of different pasture-based feeding systems on fatty acids, organic acids and volatile organic flavour compounds in yoghurt was studied. Pasture is the main source of nutrients for dairy cows in many parts of the world, including southeast Australia. Milk and milk products produced in these systems are known to contain a number of compounds with positive effects on human health. In the current study, 260 cows were fed supplementary grain and forage according to one of 3 different systems; Control (a traditional pasture based diet offered to the cows during milking and in paddock), PMR1 (a partial mixed ration which contained the same supplement as Control but was offered to the cows as a partial mixed ration on a feedpad), PMR 2 (a differently formulated partial mixed ration compared to Control and PMR1 which was offered to the cows on a feedpad). Most of the yoghurt fatty acids were influenced by feeding systems; however, those effects were minor on organic acids. The differences in feeding systems did not lead to the formation of different volatile organic flavour compounds in yoghurt. Yet, it did influence the relative abundance of these components.

Effects of dietary cottonseed oil and tannin supplements on protein and fatty acid composition of bovine milk.

This experiment was conducted to determine the effects of diets supplemented with cottonseed oil, Acacia mearnsii-condensed tannin extract, and a combination of both on composition of bovine milk. Treatment diets included addition of cottonseed oil (800 g/d; CSO), condensed tannin from Acacia mearnsii (400 g/d; TAN) or a combination of cottonseed oil (800 g/d) and condensed tannin (400 g/d; CPT) with a diet consisting of 6·0 kg dry matter (DM) of concentrates and alfalfa hay ad libitum, which also served as the control diet (CON). Relative to the CON diet, feeding CSO and CPT diets had a minor impact on feed intake and yield of lactose in milk. These diets increased yields of milk and protein in milk. In contrast to the TAN diet, the CSO and CPT diets significantly decreased milk fat concentration and altered milk fatty acid composition by decreasing the proportion of saturated fatty acids but increasing proportions of monounsaturated and polyunsaturated fatty acids. The CPT diet had a similar effect to the CSO diet in modifying fatty acid profile. Overall, reduction in milk fat concentration and changes in milk fatty acid profile were probably due to supplementation of linoleic acid-rich cottonseed oil. The TAN diet had no effect on feed intake, milk yield and milk protein concentration. However, a reduction in the yields of protein and lactose occurred when cows were fed this diet. Supplemented tannin had no significant effect on fat concentration and changes in fatty acid profile in milk. All supplemented diets did not affect protein concentration or composition, nitrogen concentration, or casein to total protein ratio of the resulting milk.

Influence of different systems for feeding supplements to grazing dairy cows on milk fatty acid composition.

This study investigated the effects of different strategies for feeding supplements to grazing dairy cows on the proportions of fatty acids in milk. Two hundred and sixteen cows were fed supplementary grain and forage according to one of 3 different strategies; (1) CONTROL: cows grazed perennial ryegrass pasture (14 kg dry matter/d) supplemented with milled barley grain fed in the milking parlour and pasture silage offered in the paddock; (2) Partial mixed ration 1 (PMR1): same pasture allotment and supplement as CONTROL strategy, but the supplements presented as a mixed ration after each milking in feedpad, and; (3) Partial mixed ration 2 (PMR2): same pasture allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage and crushed corn grain fed in a feedpad. Within each strategy, cows were assigned to receive either 6, 8, 10 or 12 kg dry matter supplement/cow per d. Milk fatty acid proportions from cows fed CONTROL and PMR1 strategies were similar and different from those fed PMR2, particularly at 10 to 12 kg dry matter supplement/cow per d. The reduction in milk fat yield and concentration in cows fed high amounts of supplement as CONTROL and PMR1 was coincident with 4 × increase in 10t-18:1 proportion. The composition of the partial mixed ration (PMR) and the amount offered affected milk fatty acid proportions and milk fat content, however, the method of supplementation did not.

The effects on claw health of supplement feeding grazing dairy cows on feed pads.

The effects of feeding and management systems on the health and welfare of grazing dairy cows were investigated by comparing the claw health of cows fed grain during milking and pasture silage in the paddock (Control), with cows fed a grain-based partial mixed ration (PMR) on a concrete feed pad. Cows were assessed on three occasions during lactation: (1) early lactation (20-81 days in milk [DIM]) before allocation to feeding treatments; (2) mid-lactation (97-158 DIM) immediately following an intensive feeding experiment, and (3) late lactation (173-243 DIM) several months after return to initial management groups. At the final examination, claw puncture resistance was measured. The results showed that for the most prevalent lesions (white line disease, paintbrush haemorrhage and traumatic bruising), there was no effect of feeding system or amount of supplement on the presence of the moderate to severe forms in early lactation, but cows were more likely to have a particular lesion at the second assessment if it was present in early lactation. Puncture resistance of the claw was not related to presence of a lesion for any of the most prevalent lesion types. It was concluded for this herd that for most indicators of claw health, there was no overall effect of different feeding systems (supplement fed during milking or on a feed pad) or amount of supplement.

Effects of melatonin on the yield and composition of milk from grazing dairy cows in New Zealand.

The aim was to determine whether administration of melatonin would alter the yield and composition of milk from grazing dairy cows in summer. Twelve sets of spring-calving identical twin Friesian cows were used in the experiment. In late-November (late spring), one twin from each set was given slow-release melatonin implants behind the ears (108 mg melatonin/cow). Two further implantations occurred at 4-weekly intervals to maintain increased circulating concentrations of melatonin for 12 weeks. The other twin served as a control. Milk yield and composition were measured twice prior to treatment and then four times over the following 12 weeks. Concentrations of melatonin, prolactin and insulin-like growth factor 1 (IGF-1) were measured in blood plasma twice before treatment and then either seven (melatonin and prolactin) or three (IGF-1) further times during the experiment. Management procedures for all cows were similar and cows grazed a daily pasture allowance of approximately 30 kg DM/cow as their sole feed source. In melatonin-treated cows there was a decrease in mean concentrations of prolactin in plasma, but concentrations of IGF-1 did not change. Melatonin reduced milk yield by 6 weeks after treatment and by the end of the 12-week experimental period milk yield in melatonin-treated cows had fallen by 23%. Melatonin also reduced concentrations of lactose in milk, but increased concentrations of fat, protein and casein, changes that were broadly similar to those that occur in late lactation in seasonally calving dairy cows. Thus, the results suggest that some of the variation in the volume and quality of milk throughout the season in New Zealand dairy systems may be due to changes in photoperiod mediated by increased concentrations of plasma melatonin in association with decreased concentrations of plasma prolactin.

A comparison of the composition, coagulation characteristics and cheesemaking capacity of milk from Friesian and Jersey dairy cows.

Twenty-nine multiparous cows of each of the Jersey and Friesian breeds, all kappa-casein AB phenotype, were grazed together and managed identically. On three occasions during 10 d in spring (early lactation), milk was collected from all cows at four consecutive milkings and bulked according to breed. On a separate occasion, milk samples were also collected from each cow at consecutive a.m. and p.m. milkings to form one daily sample per cow. The bulked milks (800-1000 l per breed on each occasion) were standardized to a protein:fat (P:F) ratio of 0.80, and 350 l from each breed was made into Cheddar cheese. The solids content of the remaining Friesian milk was then increased by ultrafiltration to a solids concentration equal to that of the Jersey milk. This solids-standardized Friesian milk and a replicate batch of P:F standardized Jersey milk were made into two further batches of Cheddar cheese in 350-l vats. Compared with Friesian milk, Jersey milk had higher concentrations of most milk components measured, including protein, casein and fat. There were few difference in milk protein composition between breeds, but there were differences in fat composition. Friesian milk fat had more conjugated linoleic acid (CLA) than Jersey milk fat. Jersey milk coagulated faster and formed firmer curd than Friesian milk. Concentrations of some milk components were correlated with coagulation parameters, but relationships did not allow prediction of cheesemaking potential. Jersey milk yielded 10% more cheese per kg than Friesian milk using P:F standardized milk, but for milks with the same solids concentration there were no differences in cheese yield. No differences in cheese composition between breeds were detected. Differences in cheesemaking properties of milk from Jerseys and Friesians were entirely related to the concentrations of solids in the original milk.

Effects of atropine on plasma amino acid profiles and on the synthesis of individual milk proteins in dairy cows fed with pasture.

Effects of atropine on blood plasma amino acid profile and on the yields and concentration of milk components were investigated in 12 Friesian cows in early lactation. Cows were housed indoors and fed with cut pasture ad libitum. Each cow received four treatments over 12 d during a replicated 4 x 4 Latin square experiment. Treatments were: control (saline); low dose (L; 30 microg atropine/kg body weight (BW)); medium dose (M; 40 microg atropine/kg BW); and 2 x L dose, 2 h apart (2 x L). On each of four treatment days, cows were milked at about 7.00, after which treatments were administered by subcutaneous injection. Cows were milked again at 2 h, 6 h and 10 h after injection. Milk samples were collected at each milking. Immediately after the 2 h milking, blood samples were drawn from each cow and the second injection was given for the 2 x L treatment. Atropine reduced hourly milk yield, and concentrations and hourly yields of total protein, casein, whey protein, alpha-casein, beta-casein, kappa-casein, beta-lactoglobulin and alpha-lactalbumin, but by differing amounts. Milk concentrations of bovine serum albumin and immunoglobulin G were increased by atropine, and overall yields of these proteins were mostly unchanged. Atropine lowered concentrations of most, but not all, amino acids in blood plasma, with essential amino acids reduced more than non-essential amino acids. Concentrations of alpha-amino N in whole blood, and glucose and insulin in blood plasma, fell after atropine injection. There was no difference between the L and M doses of atropine, but the 2 x L dose had greater effects on milk composition than the single doses. For yields of milk and milk components, the effect of the 2 x L dose was also more persistent. The results highlight the differential synthesis of individual milk proteins, and suggest that atropine might be useful for evaluating the mechanisms regulating milk protein composition.

Effects of stage of lactation and time of year on plasmin-derived proteolytic activity in bovine milk in New Zealand.

The objective of this study was to determine the effects of stage of lactation (SOL) and time of year on plasmin-derived proteolytic activity in the milk of pasture-fed dairy cows in New Zealand. Four herds of 20 Friesian cows were used, one herd calving in each of January, April, July and October. Cows grazed ryegrass/white clover pasture only, except during June (winter) when all cows received supplementary pasture silage. Milk samples were collected on four occasions during the year (spring, summer, autumn and winter) from each cow in milk, to give a total of three samples per cow (early, mid and late lactation; c. 30, 120 and 220 days after calving, respectively). Milk samples were analysed for plasmin-derived proteolytic activity. There was no effect of either SOL or time of year on plasmin activity and therefore yields of plasmin followed patterns in milk yield (highest in early lactation and in summer). There were effects of both SOL and time of year on plasminogen-derived and total plasmin plus plasminogen-derived activity, both of which were highest in late lactation and in spring. Changes in plasminogen-derived activity and total plasmin plus plasminogen-derived activity due to SOL were not only due to the decrease in milk yield associated with advancing lactation, because enzyme yields were also increased with advancing lactation. Similarly, effects of time of year on plasminogen-derived activity and total plasmin plus plasminogen-derived activity could not be attributed solely to concomitant changes in milk yield, and may be influenced by the variation in the quality and quantity of feed during the year inherent in a pasture-based dairy system. Effects of SOL on proteolytic activity were greater than, and independent of, effects of time of year.