The effect of bleaching agents on the degradation of vitamins and carotenoids in spray-dried whey protein concentrate.

Previous research has shown that bleaching affects flavor and functionality of whey proteins. The role of different bleaching agents on vitamin and carotenoid degradation is unknown. The objective of this study was to determine the effects of bleaching whey with traditional annatto (norbixin) by hydrogen peroxide (HP), benzoyl peroxide (BP), or native lactoperoxidase (LP) on vitamin and carotenoid degradation in spray-dried whey protein concentrate 80% protein (WPC80). An alternative colorant was also evaluated. Cheddar whey colored with annatto (15 mL/454 L of milk) was manufactured, pasteurized, and fat separated and then assigned to bleaching treatments of 250 mg/kg HP, 50 mg/kg BP, or 20 mg/kg HP (LP system) at 50°C for 1 h. In addition to a control (whey with norbixin, whey from cheese milk with an alternative colorant (AltC) was evaluated. The control and AltC wheys were also heated to 50°C for 1 h. Wheys were concentrated to 80% protein by ultrafiltration and spray dried. The experiment was replicated in triplicate. Samples were taken after initial milk pasteurization, initial whey formation, after fat separation, after whey pasteurization, after bleaching, and after spray drying for vitamin and carotenoid analyses. Concentrations of retinol, a-tocopherol, water-soluble vitamins, norbixin, and other carotenoids were determined by HPLC, and volatile compounds were measured by gas chromatography-mass spectrometry. Sensory attributes of the rehydrated WPC80 were documented by a trained panel. After chemical or enzymatic bleaching, WPC80 displayed 7.0 to 33.3% reductions in retinol, ß-carotene, ascorbic acid, thiamin, α-carotene, and α-tocopherol. The WPC80 bleached with BP contained significantly less of these compounds than the HP- or LP-bleached WPC80. Riboflavin, pantothenic acid, pyridoxine, nicotinic acid, and cobalamin concentrations in fluid whey were not affected by bleaching. Fat-soluble vitamins were reduced in all wheys by more than 90% following curd formation and fat separation. With the exception of cobalamin and ascorbic acid, water-soluble vitamins were reduced by less than 20% throughout processing. Norbixin destruction, volatile compound, and sensory results were consistent with previous studies on bleached WPC80. The WPC80 colored with AltC had a similar sensory profile, volatile compound profile, and vitamin concentration as the control WPC80.

Arginine Supplementation Recovered the IFN-γ-Mediated Decrease in Milk Protein and Fat Synthesis by Inhibiting the GCN2/eIF2α Pathway, Which Induces Autophagy in Primary Bovine Mammary Epithelial Cells.

During the lactation cycle of the bovine mammary gland, autophagy is induced in bovine mammary epithelial cells (BMECs) as a cellular homeostasis and survival mechanism. Interferon gamma (IFN-γ) is an important antiproliferative and apoptogenic factor that has been shown to induce autophagy in multiple cell lines in vitro. However, it remains unclear whether IFN-γ can induce autophagy and whether autophagy affects milk synthesis in BMECs. To understand whether IFN-γ affects milk synthesis, we isolated and purified primary BMECs and investigated the effect of IFN-γ on milk synthesis in primary BMECs in vitro. The results showed that IFN-γ significantly inhibits milk synthesis and that autophagy was clearly induced in primary BMECs in vitro within 24 h. Interestingly, autophagy was observed following IFN-γ treatment, and the inhibition of autophagy can improve milk protein and milk fat synthesis. Conversely, upregulation of autophagy decreased milk synthesis. Furthermore, mechanistic analysis confirmed that IFN-γ mediated autophagy by depleting arginine and inhibiting the general control nonderepressible-2 kinase (GCN2)/eukaryotic initiation factor 2α (eIF2α) signaling pathway in BMECs. Then, it was found that arginine supplementation could attenuate IFN-γ-induced autophagy and recover milk synthesis to some extent. These findings may not only provide a novel measure for preventing the IFN-γ-induced decrease in milk quality but also a useful therapeutic approach for IFN-γ-associated breast diseases in other animals and humans.

Effects of rumen-protected choline supplementation on metabolic and performance responses of transition dairy cows.

The objective of this experiment was to compare metabolic and milk production parameters in dairy cows supplemented and nonsupplemented with rumen-protected choline (RPC) during the transition period. Twenty-three nonlactating, multiparous, pregnant Holstein cows were ranked by BW and BCS 21 d before expected date of calving and immediately were assigned to receive (n = 12) or not receive (control; n = 11) RPC until 45 d in milk (DIM). Cows supplemented with RPC received (as-fed basis) 50 and 100 g/d of RPC (18.8% choline) before and after calving, respectively. Before calving, cows were maintained in 2 drylot pens according to treatment with ad libitum access to corn silage, and individually they received (as-fed basis) 3 kg/cow daily of a concentrate. Upon calving, cows were moved to 2 adjacent drylot pens according to treatment, milked twice daily, offered (as-fed basis) 35 kg/cow daily of corn silage, and individually received a concentrate formulated to meet their nutritional requirements after milking. The RPC was individually offered to cows as a topdressing into the morning concentrate feeding. Before calving, cow BW and BCS were recorded weekly, and blood samples were collected every 5 d beginning on d -21 relative to expected calving date. Upon calving and until 45 DIM, BW and BCS were recorded weekly, individual milk production was recorded daily, and milk samples were collected once a week and analyzed for fat, protein, and total solids. Blood samples were collected every other day from 0 to 20 DIM and every 5 d from 20 to 45 DIM. Based on actual calving dates, cows receiving RPC or control began receiving treatments 16.8 ± 1.7 and 17.3 ± 2.0 d before calving, respectively. No treatment effects were detected (P ≥ 0.18) on postpartum concentrate intake, BW and BCS, or serum concentrations of cortisol, ß-hydroxybutyrate, NEFA, glucose, and IGF-I. Cows supplemented with RPC had greater (P ≤ 0.01) mean serum haptoglobin and insulin concentrations compared with control. Cows supplemented with RPC had greater (P < 0.01) milk protein, total solids (P < 0.01), and milk fat concentrations (P = 0.09) compared with control. No treatment effects were detected (P ≥ 0.43) for milk yield parameters, such as fat-corrected or solids-corrected milk yield. In conclusion, supplementing RPC to transition dairy cows increased haptoglobin and insulin concentrations and benefited milk composition.

The effect of starter culture and annatto on the flavor and functionality of whey protein concentrate.

The flavor of whey protein can carry over into ingredient applications and negatively influence consumer acceptance. Understanding sources of flavors in whey protein is crucial to minimize flavor. The objective of this study was to evaluate the effect of annatto color and starter culture on the flavor and functionality of whey protein concentrate (WPC). Cheddar cheese whey with and without annatto (15 mL of annatto/454 kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a mesophilic lactic starter culture or by addition of lactic acid and rennet (rennet set). Pasteurized fat-separated whey was then ultrafiltered and spray dried into WPC. The experiment was replicated 4 times. Flavor of liquid wheys and WPC were evaluated by sensory and instrumental volatile analyses. In addition to flavor evaluations on WPC, color analysis (Hunter Lab and norbixin extraction) and functionality tests (solubility and heat stability) also were performed. Both main effects (annatto, starter) and interactions were investigated. No differences in sensory properties or functionality were observed among WPC. Lipid oxidation compounds were higher in WPC manufactured from whey with starter culture compared with WPC from rennet-set whey. The WPC with annatto had higher concentrations of p-xylene, diacetyl, pentanal, and decanal compared with WPC without annatto. Interactions were observed between starter and annatto for hexanal, suggesting that annatto may have an antioxidant effect when present in whey made with starter culture. Results suggest that annatto has a no effect on whey protein flavor, but that the starter culture has a large influence on the oxidative stability of whey.

Long-term effects of feeding monensin on methane production in lactating dairy cows.

The objective of this study was to determine the long-term effects of feeding monensin on methane (CH4) production in lactating dairy cows. Twenty-four lactating Holstein dairy cows (1.46 +/- 0.17 parity; 620 +/- 5.9 kg of live weight; 92.5 +/- 2.62 d in milk) housed in a tie-stall facility were used in the study. The study was conducted as paired comparisons in a completely randomized design with repeated measurements in a color-coded, double-blind experiment. The cows were paired by parity and days in milk and allocated to 1 of 2 treatments: 1) the regular milking cow total mixed ration (TMR) with a forage-to-concentrate ratio of 60:40 (control TMR; placebo premix) vs. a medicated TMR (monensin TMR; regular TMR + 24 mg of Rumensin Premix/kg of dry matter) fed ad libitum. The animals were fed and milked twice daily (feeding at 0830 and 1300 h; milking at 0500 and 1500 h) and CH4 production was measured prior to introducing the treatments and monthly thereafter for 6 mo using an open-circuit indirect calorimetry system. Monensin reduced CH4 production by 7% (expressed as grams per day) and by 9% (expressed as grams per kilogram of body weight), which were sustained for 6 mo (mean, 458.7 vs. 428.7 +/- 7.75 g/d and 0.738 vs. 0.675 +/- 0.0141, control vs. monensin, respectively). Monensin reduced milk fat percentage by 9% (3.90 vs. 3.53 +/- 0.098%, control vs. monensin, respectively) and reduced milk protein by 4% (3.37 vs. 3.23 +/- 0.031%, control vs. monensin, respectively). Monensin did not affect the dry matter intake or milk yield of the cows. These results suggest that medicating a 60:40 forage-to-concentrate TMR with 24 mg of Rumensin Premix/kg of dry matter is a viable strategy for reducing CH4 production in lactating Holstein dairy cows.

Hyperinsulinaemia, supplemental protein and branched-chain amino acids when combined can increase milk protein yield in lactating sows.

The aim of this study was to determine whether dietary supplementation with branched-chain amino acids, and the infusion of insulin and dextrose, would increase milk protein secretion in the sow. The experiment involved sixteen lactating sows fed either a normal lactation diet (162 g/kg crude protein, n 8) or a high-protein diet (230 g/kg crude protein, n 8) supplemented with branched-chain amino acids (valine, isoleucine and leucine). Sows were either infused with insulin and dextrose or not infused at all during mid (day 5-10) and late (day 17-22) lactation in a single reversal design. Blood samples were analysed for glucose, and the dextrose infusion rate was adjusted to maintain the blood glucose level within 15 % of pre-infusion levels. Milk (10.1 v. 11.1 kg/d; P=0.014) and lactose (628 v. 727 g/d; P=0.002) yield increased with insulin infusion, whereas milk protein content (5.0 % v. 5.5 %; P=0.007) was increased in diets supplemented with protein and branched-chain amino acids. Piglet growth was increased by feeding the higher-protein diet (237 v. 273 g/d; P=0.05) but not significantly increased by insulin infusion (245 v. 265 g/d; P=0.11). These effects were additive such that the combined treatment resulted in a 24 % (56 g/d; P<0.05) increase in piglet growth rate. These data demonstrate that increasing the dietary protein/branched-chain amino acid content can increase milk protein secretion but not milk yield. The infusion of insulin and dextrose increased milk and milk lactose yields, and tended to increase milk protein yield but not milk protein content. These effects are additive and translate to increased protein yield and piglet growth.

Effects of supplemental dietary biotin on performance of Holstein cows during early lactation.

This study determined the effects of supplemental dietary biotin (0, 10, or 20 mg/d) on performance of Holstein cows (n = 45; 18 primiparous and 27 multiparous). Treatments started at 14 d prepartum and continued until 100 d in milk (DIM). Blood samples were taken at 14 d prepartum, and blood and milk samples were taken at calving, and 30, 60, and 100 DIM. Dry matter intake during lactation was not different across treatments (19.7 kg/d). Milk production linearly increased with biotin supplementation (36.9, 37.8, and 39.7 kg/d for 0, 10, and 20 mg/d of supplemental biotin, respectively). Biotin supplementation did not affect milk fat and true protein percentages or fat yield but linearly increased true protein yield. Supplemental biotin increased concentrations of biotin in plasma and milk at all time points. Concentrations of biotin in plasma and milk (colostrum) at calving were higher than at other time points for cows fed supplemental biotin. In an ancillary experiment, plasma biotin concentrations were not as high when cows were fed 20 mg/d of supplemental biotin for 14 d during the middle of their dry period as when cows were fed 20 mg/d of biotin for the last 14 d of gestation. This suggests that events associated with parturition altered plasma biotin concentrations. Plasma concentrations of glucose, insulin, nonesterified fatty acids, and molar proportions of ruminal volatile fatty acids were not affected by biotin supplementation. Biotin supplementation had no effect on change in body weight or condition score. Supplemental biotin linearly increased milk and protein yields, however, the mode of action that caused these increases was not determined.

Intramammary infusion of insulin or long R3 insulin-like growth factor-I did not increase milk protein yield in dairy cows.

Two experiments investigated the regulation of milk protein synthesis in well-fed cows (n = 4) using 1) a hyperinsulinemic-euglycemic clamp and 2) intramammary infusion of insulin or long R3 insulin-like growth factor-I plus supplementary amino acids. In experiment 1, insulin was infused at 1.0 microg x kg BW(-1) x h(-1) to increase circulating levels fourfold, and euglycemia was maintained by infusion of glucose. An insulin clamp increased the yields of casein and whey protein both with and without supplementary amino acids. Plasma concentrations of insulin-like growth factor-I were increased and insulin-like growth factor binding protein-2 decreased during insulin clamp, while both insulin and insulin-like growth factor-I in milk were elevated by this treatment. Milk concentrations of insulin peaked on day 4, but insulin-like growth factor-I concentrations in milk peaked on day 1 of the insulin clamp. In experiment 2, intramammary infusion of insulin had no effects on any measured variables, while yields of milk, protein, and fat were slightly lower following long R3 insulin-like growth factor-I treatment. This could be associated with an increase in somatic cell count, which occurred following long R3 insulin-like growth factor-I treatment. Results from experiment 1 suggest insulin and insulin-like growth factor-I are likely candidates responsible for the increased milk protein yields during the insulin clamp. However, in experiment 2 neither hormone enhanced milk protein yield when administered using an intramammary technique.