Immediate, cumulative and residual effects of short- and long-term low plane of nutrition on milk protein and casein composition

Immediate and residual effects of two lengths of low plane of nutrition (PON) on the synthesis of milk protein and protein fractions were studied at the Mutdapilly Research Station, in south-east Queensland. Thirty-six multiparous Holstein-Friesian cows, between 46 and 102 days in milk (DIM) initially, were used in a completely randomised design experiment with three treatments. All cows were fed on a basal diet of ryegrass pasture (7.0 kg DM/cow.day), barley-sorghum concentrate mix (2.7 kg DM/cow.day) and a canola meal-mineral mix (1.3 kg DM/cow.day). To increase PON, 5.0 kg DM/cow.day supplemental maize and forage sorghum silage was added to the basal diet. The three treatments were (C) high PON (basal diet + supplemental silage); (L9) low PON (basal diet only) for a period of 9 weeks; and (L3) low PON (basal diet only) for a period of 3 weeks. The experiment comprised three periods (1) covariate – high PON, all groups (5 weeks), (2) period of low PON for either 3 weeks (L3) or 9 weeks (L9), and (3) period of high PON (all groups) to assess ability of cows to recover any production lost as a result of treatments (5 weeks). The low PON treatment periods for L3 and L9 were end-aligned so that all treatment groups began Period 3 together. Although there was a significant effect of L9 on yields of milk, protein, fat and lactose, and concentrations of true protein, whey protein and urea, these were not significantly different from L3. There were no residual effects of L3 or L9 on protein concentration or nitrogen distribution after 5 weeks of realimentation. There was no significant effect of low PON for 3 or 9 weeks on casein concentration or composition.

Immediate and residual effects of heat stress and restricted intake on milk protein and casein composition and energy metabolism

The effects of heat stress on dairy production can be separated into 2 distinct causes: those effects that are mediated by the reduced voluntary feed intake associated with heat stress, and the direct physiological and metabolic effects of heat stress. To distinguish between these, and identify their effect on milk protein and casein concentration, mid-lactation Holstein-Friesian cows (n = 24) were housed in temperature-controlled chambers and either subjected to heat stress HS; temperature-humidity index (THI) ~78 or kept in a THI < 70 environment and pair-fed with heat-stressed cows (TN-R) for 7 d. A control group of cows was kept in a THI < 70 environment with ad libitum feeding (TN-AL). A subsequent recovery period (7 d), with THI < 70 and ad libitum feeding followed. Intake accounted for only part of the effects of heat stress. Heat stress reduced the milk protein concentration, casein number, and casein concentration and increased the urea concentration in milk beyond the effects of restriction of intake. Under HS, the proportion in total casein of αS1-casein increased and the proportion of αS2-casein decreased. Because no effect of HS on milk fat or lactose concentration was found, these effects appeared to be the result of specific downregulation of mammary protein synthesis, and not a general reduction in mammary activity. No residual effects were found of HS or TN-R on milk production or composition after THI < 70 and ad libitum intake were restored. Heat-stressed cows had elevated blood concentrations of urea and Ca, compared with TN-R and TN-AL. Cows in TN-R had higher serum nonesterified fatty acid concentrations than cows in HS. It was proposed that HS and TN-R cows may mobilize different tissues as endogenous sources of energy.

The use of early lactation milk protein content to predict subsequent fertility performance and likelihood of culling, in commercial dairy cows

A dataset of 1,846,990 completed lactation record,; was created Using milk recording data from 8,967 commercial dairy farms in the United Kingdom over a five year period. Herd-specific lactation curves describing levels of milk, Cat and protein by lactation number and month of calving were generated for each farm. The actual yield of milk and protein proportion at the first milk recording of individual cow lactations were compared with the levels taken from the lactation curves. Logistic regression analysis showed that cows production milk with a lower percentage of protein than average had a significantly lower probability of being in-calf at 100 days post calving and it significantly higher probability of being culled at the end of lactation. The culling rates derived from the studied database demonstrate the current high wastage rate of commercial dairy cows. Well of this wastage is due to involuntary culling as a result of reproductive failure.

Effects of dietary urea levels on milk protein fractions of Holstein cows

The aim of this study was to evaluate the effects of substituting soybean meal for urea on milk protein fractions (casein, whey protein and non-protein nitrogen) of dairy cows in three dietary levels. Nine mid-lactation Holstein cows were used in a 3 x 3 Latin square arrangement, composed of 3 treatments, 3 periods of 21 days each, and 3 squares. The treatments consisted of three different diets fed to lactating cows, which were randomly assigned to three groups of three animals: (A) no urea inclusion, providing 100% of crude protein (CP), rumen undegradable protein (RUP) and rumen degradable protein (RDP) requirements, using soybean meal and sugarcane as roughage; (B) urea inclusion at 7.5 g/kg DM in partial substitution of soybean meal CP equivalent; (C) urea inclusion at 15 g/kg DM in partial substitution of soybean meal CP equivalent. Rations were isoenergetic and isonitrogenous-1 60 g/kg DM of crude protein and 6.40 MJ/kg DM of net energy for lactation. When the data were analyzed by simple polynomial regression, no differences were observed among treatments in relation to milk CP content, true protein, casein, whey protein, non-casein and non-protein nitrogen, or urea. The milk true protein:crude protein and casein:true protein ratios were not influenced by substituting soybean meal for urea in the diet. Based on the results it can be concluded that the addition of urea up to 15 g/kg of diet dry matter in substitution of soybean meal did not alter milk protein concentration casein, whey protein and its non-protein fractions, when fed to lactating dairy cows. (c) 2007 Elsevier B.V. All rights reserved.

Effects of diets high in whey, soy, red meat and milk protein on body weight maintenance in diet-induced obesity in mice

This study examined the effects of different food sources of protein on energy intake, body weight maintenance, and on the responses of plasma leptin, insulin and adiponectin in chronic high-fat diet-induced obese mice. Obesity was induced in 47 mice with a high-fat diet for 20 weeks. They were divided into five diet groups to test the effects of a higher protein proportion (30% energy), achieved at the expense of carbohydrate. For the next eight weeks, four of the groups were fed diets of chow formulated with whey, soy, red meat or milk while the control group continued on their high-fat diet. The results showed that: (i) increasing the protein : carbohydrate ratio (both at 30% energy) in a high-fat diet did not reduce the level of obesity; (ii) the type of protein added, however, did have a significant effect on the level of obesity attained; (iii) whey protein stabilised weight gain the most, had the strongest satiety effects and also stimulated the highest production of adiponectin; and (iv) whey protein also was associated with the lowest insulin values among all proteins tested. Plasma leptin levels were not affected by any of the diets. Dietary fat remains a potent factor in weight management, but the type and amount of protein may also be important through its effects on food intake. In particular, the apparent decreased appetite associated with increased adiponectin in the whey-based high-protein diet may contribute to stabilised body mass in chronic high-fat diet-induced obesity.

Aspects of milk protein catabolism by lactobacilli

Lactobacillus plantarum and subspecies of Lactobacillus casei were isolated from good quality mature Cheddar cheese and characterized with respect to metabolic functions that would allow their use in cheesemaking. In this way microbiological control of the maturation process with particular emphasis on protein catabolism was achieved. The lactobacilli isolated were selected for low growth rates (and acid production) in milk, and low proteinase activity to allow for their addition in high numbers to cheesemilk together with the normal starter flora (group N streptococci). The growth and acid production of the starter bacteria were unaffected by the presence of the lactobacilli during cheese manufacture and it was found that the added lactobacilli were able to grow and function under the conditions prevalent in Cheddar cheese during maturation. It was also demonstrated that the lactobacilli could be grown in an artificial medium to high numbers under controlled conditions and could be harvested for the preparation of cell concentrates, a necessary characteristic for commercialization. The lactobacilli also metabolized citrate, a potential problem in cheese maturation associated with C02 production but this did not adversely affect the maturation process under the conditions used. Compared to the group N streptococci the non-starter lactobacilli possessed a proteinase system that had a higher temperature optimum and was less affected by heat and sodium chloride. They also possessed a more active peptidase system although both the lactobacilli and the starter organisms possessed a similar range of peptidases. Non-starter lactobacilli were added to normal cheese and cheese made with proteinase negative starter. The added organisms did not adversely affect manufacturing parameters and did not metabolize citrate or lead to the formation of biogenic amines. However protein catabolism rates, particularly with respect to peptide degradation, were increased, as was flavour development and intensity. It was observed that the body and texture of the cheeses was unaffected by the treatment. By controlling both the starter and non-starter microflora in the cheeses a practical system for favourably influencing cheese maturation was possible. The investigation has demonstrated that carefully selected and characterized non-starter lactobacilli can be incorporated into Cheddar cheese manufacture in order to influence flavour development during maturation. Moreover the organisms can be added to the vat stage of manufacture without causing problems to the manufacturing process. This approach is a simple cost effective means of improving the cost of Cheddar cheese production and provides an unique opportunity to improve and control quality of all Cheddar cheese produced.

A novel approach identified the FOLR1 gene, a putative regulator of milk protein synthesis

This study has utilised comparative functional genomics to exploit animal models with extreme adaptation to lactation to identify candidate genes that specifically regulate protein synthesis in the cow mammary gland. Increasing milk protein production is valuable to the dairy industry. The lactation strategies of both the Cape fur seal (Artocephalus pusillus pusillus) and the tammar wallaby (Macropus eugenii) include periods of high rates of milk protein synthesis during an established lactation and therefore offer unique models to target genes that specifically regulate milk protein synthesis. Global changes in mammary gene expression in the Cape fur seal, tammar wallaby, and the cow (Bos taurus) were assessed using microarray analysis. The folate receptor α (FOLR1) showed the greatest change in gene expression in all three species [cow 12.7-fold (n = 3), fur seal 15.4-fold (n = 1), tammar 2.4-fold (n = 4)] at periods of increased milk protein production. This compliments previous reports that folate is important for milk protein synthesis and suggests FOLR1 may be a key regulatory point of folate metabolism for milk protein synthesis within mammary epithelial cells (lactocytes). These data may have important implications for the dairy industry to develop strategies to increase milk protein production in cows. This study illustrates the potential of comparative genomics to target genes of interest to the scientific community.

Insulin, a key regulator of hormone responsive milk protein synthesis during lactogenesis in murine mammary explants

Murine milk protein gene expression requires insulin, hydrocortisone, and prolactin; however, the role of insulin is not well understood. This study, therefore, examined the requirement of insulin for milk protein synthesis. Mammary explants were cultured in various combinations of the lactogenic hormones and global changes in gene expression analysed using Affymetrix microarray. The expression of 164 genes was responsive to insulin, and 18 were involved in protein synthesis at the level of transcription and posttranscription, as well as amino acid uptake and metabolism. The folate receptor gene was increased by fivefold, highlighting a potentially important role for the hormone in folate metabolism, a process that is emerging to be central for protein synthesis. Interestingly, gene expression of two milk protein transcription factors, Stat5a and Elf5, previously identified as key components of prolactin signalling, both showed an essential requirement for insulin. Subsequent experiments in HCll cells confirmed that Stat5a and Elf5 gene expression could be induced in the absence of prolactin but in the presence of insulin. Whereas prolactin plays an essential role in phosphorylating and activating Stat5a, gene expression is only induced when insulin is present. This indicates insulin plays a crucial role in the transcription of the milk protein genes.

Targeting viral hepatitis using natural milk protein and traditional medicinal herbs

Hepatitis is a major health related disease spread worldwide with frequent occurrence of epidemics. It is a zoonotic disease which leads to jaundice, anorexia, malaise and death. Although, vaccines have been developed against hepatitis A and hepatitis B, it is a challenge to generate vaccines against other prevalent forms of hepatitis which are equally harmful and spread worldwide. Natural products that are obtained from living organisms and found freely in nature have proven to be effective against several types of hepatitis due to presence of pharmacologically important bioactive compounds. Since they are natural products they do not cause much harm to body and can be easily applied or consumed. Our main focus is on hepatitis E virus (HEV) which is an opportunistic pathogen and leads to acute jaundice. This virus is mainly present in developing countries with poor sanitation facilities and effects individuals having weak immune response, mainly children, old people, organ transplant patients and pregnant women. HEV infection makes the patient more susceptible to infections from other viruses as well as HIV. In this review, we discussed about the natural protein known as lactoferrin which is isolated from milk colostrum and extracts of some medicinal plants that have proven to be effective against various forms of hepatitis. Such form of natural therapies forms the basis of modern medicine and major pharmaceutical discoveries.

Paracrine control of milk protein gene expression in tammar wallaby

Stephen utilised the unique lactation strategy of the tammar wallaby to identify factors within the mammary gland that determine the composition of milk and how the milk composition changes throughout lactation in order to provide immunity both to the nursing mammary gland and the suckling.

SurR9-C84A mutant nanocarrier and milk protein therapeutics for neurological disorders

 The current project revealed that the novel nanoformulation of SurR9-C84A was able to rescue the neurons following the Alzheimer’s related ß-amyloid toxicity and inflammation. In addition, bovine lactoferrin was found to have potential differentiating effect in the tumor cells and hence is a valuable therapeutic for strengthening the degenerating neurons.