Calcium Content Of Milk Research Articles

Analysis of Calcium, Iron, Ash, Fat, and Water Content in Fresh and Processed Cow's Milk Using Atomic Absorption Spectrophotometry Methods

Milk is a source of nutrition for the body's growth, containing calcium and iron minerals. This study analyzes the optimal calcium, iron, ash, water, and fat levels in fresh and processed cow's milk. This study used five samples: pure milk (S1), pasteurized pure milk (S2), pasteurized milk with sugar (S3), pasteurized milk with paste coloring and citric acid (S4), and pasteurized milk with powder coloring(S5). The results showed that the calcium content of milk 4 (S4) treated with pasteurized milk added with sugar and paste coloring and citric acid had a higher calcium content than the other four samples by 98.61 mg/kg, at levels of milk iron 5 (S5) treated with pasteurized milk added with sugar and powdered dyes had a higher iron content than the other four samples by 73.81 mg/kg. The ash content of pure milk was higher at 0.96%. The fat content of pasteurized milk, the taste of coloring paste and powder, was higher than the other three samples at 2.80%. The water content of pasteurized added sugar milk was higher than the other four samples at 88.58%. Pure milk had the most optimal calcium (Ca) and iron (Fe) levels from the other four samples.

Macroelement Seasonal Variations in Latvian Organic Milk

Abstract Consumer perception of organic milk is associated with the assumption that organic milk differs from conventionally produced milk. The aim of the present study was to analyse calcium, magnesium, and phosphorus concentration in organic milk in the context of the season. The study was conducted from November 2019 to the end of October 2020. Over a year, raw bulk milk samples were collected and analysed. The milk for the study was supplied by two organic farms located in Latvia. Cows received a total mixed ration consisting of high moisture maize silage, grass silage, etc. The chemical composition of the total mixed rations was analysed, as well as fat, protein, lactose, milk solids non-fat, and total solids, calcium, phosphorus, and magnesium content in organic milk were determined. Seasonal variation in milk composition was observed. The average calcium concentration in our study was 107.96 ± 9.61 mg·100 g−1 with a lower average concentration 97 mg·100 g−1 in organic milk in March. The concentration of calcium, phosphorus, and magnesium was higher in organic milk during the spring–summer season. The sale of organic milk is growing in Latvia, and the presence of a favourable level of calcium in organic milk during the whole year should be reached, providing calcium concentration in cow’s milk around 120 mg·100 g−1 throughout the lactation period. Milk and milk products are an important part of daily nutrition, recommended to every consumer due to their wholesomeness and calcium concentration. Evaluating the bone health data of the Latvian population, 100 ml of milk consumption should provide at least 15% of the recommended daily intake of calcium.

Maternal diet during breastfeeding in correlation to calcium and phosphorus concentrations in human milk.

The impact of maternal diet on mineral concentration in human milk (HM) remains unclear. The main aim of this study was to investigate the relationship between maternal dietary intake and calcium and phosphorus concentrations in HM. Furthermore, we aimed to evaluate the intake of both minerals by exclusively breastfed infants. HM samples were obtained from 30 mothers at 6-8 weeks postpartum. Each mother was asked to express pre- and postfeeding milk four times during a 24-h period (6.00-12.00, 12.00-18.00, 18.00-24.00, 24.00-6.00). Maternal dietary assessment was based on a food frequency questionnaire and 3-day dietary records. Analysed minerals were determined using an inductively coupled plasma mass spectrometer (NexION 300D ICP mass spectrometer, Perkin Elmer SCIEX). The mean concentrations of calcium and phosphorus in HM samples were 278.7 ± 61.0 and 137.1 ± 21.9 mg/L, respectively, maintaining 2:1 ratio by weight. The concentration of both minerals was correlated with each other (r = 0.632, p = <0.001). The infants' mean calcium intake was 149.53 ± 36.41 mg/L, and their mean phosphorus intake was 74.62 ± 19.41 mg/L. The risk of insufficient intake of calcium was reported in 60% of infants (n = 18). Spearman's/Pearson's correlation coefficients did not reveal any correlations between HM calcium concentration and maternal diet, contrary to HM phosphorus concentration, which was positively correlated with energy (r = 0.369, p = 0.045), total protein (r = 0.464, p = 0.01), calcium (r = 385, p = 0.036), phosphorus (r = 501, p = 0.005), niacin (p < 0.001) and pyridoxine (r = 382, 0.037) intake. However, in multivariable analysis we observed that maternal dietary intake of both minerals had a positive influence on their concentration in HM. Maternal calcium and phosphorus intake influenced the concentration of both minerals in HM; however, the relationship was rather weak. In addition, we observed that calcium intake by most of the exclusively breastfed infants was insufficient to meet the recommended daily intake.

Genome-wide association study for selected cheese-making properties in Dual-Purpose Belgian Blue cows.

This study aimed to estimate genetic parameters and identify genomic region(s) associated with selected cheese-making properties (CMP) in Dual-Purpose Belgian Blue (DPBB) cows. Edited data were 46,301 test-day records of milk yield, fat percentage, protein percentage, casein percentage, milk calcium content (CC), coagulation time (CT), curd firmness after 30 min from rennet addition (a30), and milk titratable acidity (MTA) collected from 2014 to 2020 on 4,077 first-parity (26,027 test-day records), and 3,258 second-parity DPBB cows (20,274 test-day records) distributed in 124 herds in the Walloon Region of Belgium. Data of 28,266 SNP, located on 29 Bos taurus autosomes (BTA) of 1,699 animals were used. Random regression test-day models were used to estimate genetic parameters through the Bayesian Gibbs sampling method. The SNP solutions were estimated using a single-step genomic BLUP approach. The proportion of the total additive genetic variance explained by windows of 25 consecutive SNPs (with an average size of ∼2 Mb) was calculated, and regions accounting for at least 1.0% of the total additive genetic variance were used to search for candidate genes. Heritability estimates for the included CMP ranged from 0.19 (CC) to 0.50 (MTA), and 0.24 (CC) to 0.41 (MTA) in the first and second parity, respectively. The genetic correlation estimated between CT and a30 varied from -0.61 to -0.41 and from -0.55 to -0.38 in the first and second lactations, respectively. Negative genetic correlations were found between CT and milk yield and composition, while those estimated between curd firmness and milk composition were positive. Genome-wide association analyses results identified 4 genomic regions (BTA1, BTA3, BTA7, and BTA11) associated with the considered CMP. The identified genomic regions showed contrasting results between parities and among the different stages of each parity. It suggests that different sets of candidate genes underlie the phenotypic expression of the considered CMP between parities and lactation stages of each parity. The findings of this study can be used for future implementation and use of genomic evaluation to improve the cheese-making traits in DPBB cows.

Protein Preparations as Ingredients for the Enrichment of Non-Fermented Milks.

Milk enriched with functional ingredients of milk proteins delivers health and nutritional benefits, and it can be particularly recommended to consumers with increased protein requirements. The aim of this study was to evaluate the applicability of casein and serum protein preparations obtained by membrane filtration in the laboratory as additives to non-fermented milks, as compared with commercial protein, preparations (whey protein isolate or concentrate and casein concentrate). The addition of protein preparations increased the pH, viscosity and heat stability of non-fermented milks. Milks enriched with whey proteins were characterized by a higher content of valine and isoleucine and a lower content of leucine, lysine and arginine. Addition of casein or whey protein concentrate decreased the phosphorus content and increased the calcium content of milk, but only in the products enriched with casein or whey protein concentrate. Color saturation was higher in products fortified with protein preparations obtained in the laboratory and commercial whey protein concentrate. Milk enriched with whey protein isolate, followed by milk serum protein concentrate, received the highest scores in the sensory evaluation. The presented results make a valuable contribution to the production of milks enriched with various protein fractions. The study proposes the possibility of production of protein preparations and milks enhanced with protein preparations, which can be implemented in industrial dairy plants.

Influence of calcium on the uptake of ingested strontium

Abstract Radioactive isotopes of strontium, mainly 90Sr, released into the environment due to nuclear accidents may contribute significantly to the internal radiation exposure of members of the public after ingestion of strontium with contaminated foodstuffs. The committed radiation dose is significantly dependent on the fraction of the ingested activity that crossed the gut wall (f1 value). The directive 96/29/EURATOM has adopted f1 values of 0.3 for adults. This study was aimed to investigate how far the calcium content of foodstuffs influences the uptake of ingested strontium. For aqueous solutions without calcium containing 1 mg strontium, f1 values of 0.62 ± 0.13 (mean ± SD) were obtained. However, the uptake of 1 mg Sr from milk, and respectively from solutions with calcium was lower than from aqueous solution (f1: = 0.32 ± 0.06, respectively f1: = 0.31 ± 0.06). The data obtained show a significant reduction of the uptake of ingested strontium from milk in comparison to aqueous solution. The calcium content of milk could explain this reduction.

Elevated serotonin coordinates mammary metabolism in dairy cows.

Serotonin plays a diverse role in maternal and mammary metabolism. Recent research in the dairy cow has shown a relationship between serotonin and calcium, with increased serotonin concentrations improving calcium homeostasis in the peri‐partum dairy cow. Therefore, the objective was to elucidate how administration of 5‐hydroxy‐l‐tryptophan (5‐HTP), the immediate precursor to serotonin, altered serotonin and calcium metabolism in lactating dairy cows. Twelve mid‐late lactation multiparous cows were blocked by parity, production and days in milk and allocated to a daily intravenous infusion of (i) 1.5 mg/kg of 5‐HTP (n = 6) or (ii) saline (n = 6) for 3 consecutive days. Milk samples were collected daily. Blood samples were collected before and after each infusion with mammary biopsies and blood samples collected at 48, 56, and 72 h relative to termination of first infusion. Infusion of 5‐HTP increased (p = 0.001) circulating serotonin concentrations and decreased blood calcium via a transient hypocalcemia immediately after each infusion (p = 0.02). Treatment with 5‐HTP increased milk calcium concentrations (p = 0.02) and calcium release‐activated channel protein 1 (ORAI1) mRNA at 56 h and protein at 48 h relative to termination of first infusion (p = 0.008 and p = 0.09, respectively). Fifty‐six hours from termination of the first infusion mRNA of parathyroid hormone‐related protein and mammary serotonin content were increased relative to control (p = 0.03 and p = 0.05, respectively). These findings demonstrate the ability of 5‐HTP infusion to increase circulating serotonin concentrations and alter endocrine and mammary autocrine/paracrine calcium and serotonin metabolism in the lactating dairy cow.

Relationship between Selected Trace Elements in Human Milk and Psychosocial Characteristics in Korean Early Postpartum Women.

This study aimed to identify the relationship between selected trace elements in human milk and depression, breastfeeding self-efficacy, sleep satisfaction, and the demographic and obstetric characteristics of lactating mothers. Forty lactating mothers recovering after birth in two postpartum care centers located in Changwon, South Korea, were studied. Calcium, sodium, iron, and selenium concentrations in human milk were analyzed using inductively coupled plasma mass spectrometry at the analysis center of Kyungnam University. Data were analyzed using descriptive statistics, the Kruskal-Wallis test, the Mann-Whiney U test, and Spearman’s correlation coefficients using an SPSS 23.0 program. There were no significant differences in concentration of selected trace elements (calcium, sodium, iron, and selenium) in human milk according to demographic and obstetric characteristics. Sodium concentration was negatively correlated with breastfeeding self-efficacy (r = −0.51, CI = −0.71 to −0.24). Selenium concentration was negatively correlated with calcium concentration (r = −0.34, CI = −0.58 to 0.38). Postpartum depression was negatively correlated with sleep satisfaction (r = −0.46, CI = −0.67 to −0.17) and with breastfeeding self-efficacy (r = −0.41, CI = −0.64 to −0.11). Breastfeeding self-efficacy was positively correlated with sleep satisfaction (r = 0.48, CI = 0.20 to 0.69). This study suggests that sodium concentration in human milk is associated with breastfeeding self-efficacy.

Composition, coagulation characteristics, and cheese making capacity of yak milk

Yak is one of the few species of which the rennet-coagulated cheese making characteristics of its milk are still not well understood. This study investigated composition and rennet-induced coagulation properties of milk from 17 individual yak cows in comparison with milk from 32 individual Holstein cows. Yak cows produced milk with generally higher concentrations of milk components. The concentrations of fat, protein, solids-not-fat (SNF), and calcium in yak milk were 1.89-, 1.68-, 1.46-, and 2-fold those in Holstein milk, respectively. The hydrodynamic radii of casein micelles (187.25 nm) and chymosin-induced paracasein (1,620 nm) were about twice the sizes of those found in Holstein milk. Higher concentrations of calcium in yak milk, together with larger sizes of casein micelles, explains the reason for its fast rate of curd formation and firmer curd texture. Optical microrheology analysis also showed that Ca2+ concentration had greater influence on the coagulation of yak milk than on Holstein milk. Cheese making trials with yak and Holstein milk proved the higher cheese yield of yak milk: 1.67-fold that of Holstein milk. Therefore, yak milk could be a suitable source of milk for enzyme-coagulated cheese making.

The factors influencing rennet-induced coagulation properties of yak milk: The importance of micellar calcium during gelation

The objective of this study was to evaluate the importance and effects of age, hair color, lactation stage and number of yak, as well as physicochemical properties and composition of yak milk on rennet-induced coagulation characteristics. Results showed that casein micelle size distribution and total calcium content of milk from 68 yaks were the most important factors affecting the gelation characteristics, including gelling time and gel strength. The yak milk containing smaller casein micelles and higher calcium content formed stronger gels and had shorter incubation time. Moreover, casein micelle samples containing 20.6, 16.8, and 13.9 mmol/L micellar calcium were obtained through pH-induced dialysis method. The results clearly showed that although the removal of micellar calcium did not affect casein macropeptide (CMP) release, the gelation of samples containing lower micellar calcium value corresponded to lower aggregation rate of para-casein micelles and more CMP release. In addition, removal of micellar calcium may lead to longer incubation time and sparser gel structure. This study highlights that higher micellar calcium is indispensable to the aggregation of yak casein micelles and the formation of firm gel, because enough micellar calcium may promote the aggregation of para-casein and firmly links casein micelles.

Lowering dietary cation-anion difference increases sow blood and milk calcium concentrations.

A study was conducted to evaluate the effects of feeding an acidogenic diet with a low dietary cation-anion difference (DCAD) on acid-base balance, blood, milk, and urine Ca concentrations of sows during lactation. A total of 30 multiparous sows (parity: 4.5 ± 2.9, Smithfield Premium Genetic, Rose Hill, NC) were allotted to 1 of 2 dietary treatments: CON (control diets were corn-soybean meal based with a calculated DCAD of 170 and 226 mEq/kg during late gestation and lactation, respectively) or ACI (acidogenic diets had a DCAD 100 mEq/kg lower than the control diets). The lower DCAD was achieved by the addition of an acidogenic mineral. The DCAD was calculated as mEq (Na + K - Cl)/kg diet. Sows had a daily access to 2-kg feed from day 94 of gestation to parturition and ad libitum access to feed during lactation. Blood and urine pH and Ca, serum macrominerals, serum biochemistry, Ca-regulating hormones, and milk composition were measured. Sows in ACI had a lower (P < 0.05) blood pH than sows in CON at day 1 of lactation. Sows in ACI had a lower (P < 0.05) urine pH at day 108 of gestation, days 1, 9, and 18 of lactation compared with sows in CON. Sows in ACI had greater (P < 0.05) concentrations of serum total Ca at days 1 and 18 of lactation than sows in CON. There was a greater (P < 0.05) concentration of colostrum Ca in ACI than in CON. There was no difference in urine Ca concentration between treatments during lactation. Concentrations of parathyroid hormone and 1,25-dihydroxycholecalciferol were not different between treatments at either day 1 or 18 of lactation. Sows in ACI tended to have a smaller (P = 0.086) concentration of total alkaline phosphatase in serum at day 18 of lactation compared with sows in CON. At day 1 of lactation, the concentration of serum Cl in ACI was greater (P < 0.05) than that in CON. Feed intake, BW loss, and litter performance were not different between treatments. Collectively, feeding an acidogenic diet with a low DCAD to sows can induce a mild metabolic acidosis at farrowing, reduce the urine pH consistently, and increase serum total Ca and colostrum Ca concentrations during lactation but without altering the parathyroid hormone and 1,25-dihydroxycholecalciferol levels during lactation.

Tryptophan Supplementation Increases Reproduction Performance, Milk Yield, and Milk Composition in Lactating Sows and Growth Performance of Their Piglets.

Tryptophan (Trp) can produce bioactive compounds for appetite regulation, calcium mobilization, and mammary gland homeostasis via a serotonin pathway. This study evaluated the effects of Trp supplementation on the reproduction performance, milk yield, and composition of lactating sows, growth performance of their piglets, and the secretion function of porcine mammary epithelial cells (PMECs). The infrared emulsion analyzer and ELISA analyses revealed that feeding sows with a 0.12% Trp addition increased ( P < 0.05) sow average daily feed intake, milk yield, milk calcium concentration, average daily gain of piglets, fatty acid synthase (FAS) and lactose synthase (LS), β-casein secretion, intracellular Ca2+ level, the expression of calcium binding protein CaM, and the activity of CaMKII. In a cellular experiment of PMECs treated with Trp, ELISA and flow cytometry analyses revealed that the pretreatment of a Trp hydroxylase inhibitor reduced ( P < 0.05) FAS and LS synthesis, the intracellular Ca2+ level, and the activity of CaMKII. In conclusion, Trp supplementation at 0.12% increased sows' reproductive performance, milk yield, and calcium concentration and piglets' growth performance. Milk yield increased by Trp was linked to 5-hydroxytryptamine-mediated synthesis of FAS, LS, and β-casein in PMECs, while the increase in calcium concentration was attributed to increasing CaM expression and CAMKII activity.

MONITORING OF CALCIUM CONTENT OF RAW COW MILK

Milk is a natural food product that is unique in its nutritive value and signifcance for human organism. Its composition is balanced in major biochemical components as well as mineral components including calcium. Calcium is essential for many metabolic processes and is contained in milk in easily digestible and phosphorus-balanced form. Therefore, decrease in its content in milk creates prerequisites for insufcient meeting the body need in the said microelement and has an effect on human metabolism especially in children. Results of laboratory testing of 400 milk samples collected from clinically healthy Holstein and Black and White Spotted cows kept on 40 farms located in the Moscow Oblast in 2001–2017 are presented. The raw milk was examined for the following quality indicators: sensory, physical and chemical as well as microbiological parameters. It was found that calcium concentration in milk depended on the season. It was shown that the majority of tested milk samples did not comply with the veterinary and sanitary quality parameters despite of the tendency to increase in analyzed parameter content in autumn. The monitoring showed recent decrease in calcium content of cow milk and dairy products intended for infant food. Average calcium content of raw milk was found to be 900–950 mg; it varied from 700 up to 1,100 mg of calcium/litre of milk. Further testing scheme based on analysis of such factors as pure protein, diet, biologically active dietary supplements is proposed. Such testing will allow comprehensive assessment of exogenous factors influencing calcium content of milk as well as harmonization of Russian requirements for food quality and safety assessment with the European ones.

Study of quality indicators of fermented-milk cheese obtained from skimmed milk at a controlled content of calcium

The results obtained in the study of influence of calcium content in skimmed milk on organoleptic, physical, physical-chemical and technological properties were summarized. A method for regulating calcium content in milk using a natural ion exchanger, sodium alginate, was proposed. It has been shown that the use of natural sequestrants allows producers to reduce calcium content in milk to 50 %. In the framework of the conducted studies, a correlation between the degree of milk decalcification and the physical and chemical properties of the fermented clot and whey has been established. It was shown that removal of calcium from milk results in the destruction of caseinate-calcium-phosphate complex with a simultaneous decomposition of the casein micelles to submicelles. The found effect manifests itself by formation of a characteristic fermented clot and an increase in the weight fraction of soluble protein in whey. The influence of calcium content in milk on qualitative parameters of fermented-milk cheese, its microstructure and dispersion of protein particles was established. The boundary conditions of decalcification of milk were substantiated which allows producers to obtain fermented-milk cheese with high qualitative indicators. It was proved that decalcification of milk in a rational interval and at specified parameters enables production of fermented-milk cheese which is characterized by a spreadable consistency, absence of crumbs and whey separation. The organoleptic properties of fermented-milk cheese completely correlate with the indicator of moisture retaining ability which regularly grows with an increase in decalcification within a rational interval. Dispersion of fermented-milk cheese and the size of protein particles were established. A direct relationship between the size of protein particles and sedimentation stability of systems was revealed. An increase in colloidal stability was observed at a reduced calcium content resulting in a growth of the fraction of particles with a smaller diameter. The results obtained in the study completely reflect the theory of decomposition of casein micelles at a reduced calcium content in milk

STUDY OF INFLUENCE OF CALCIUM CONTENT IN MILK ON QUALITY INDICATORS OF COTTAGE CHEESE

The analysis was realized, and the dependence between the calcium content and organoleptic and functional-technological properties of milk as a raw material for producing sour milk cheese was determined. It was demonstrated, that alongside with other factors, the important role in milk clotting belongs to calcium, which role is in binding of free OH-groups of phosphoric acid of casein micelles. As a result of the aforesaid, their negative charge and colloid stability decrease with further hydrophilicity decrease with further aggregation of casein molecules. It was established, that the excessive content of calcium in milk is negative that is manifested in formation of the dry and brittle consistence of sour milk cheese. There was offered the way of calcium content regulation in milk by its decalcification using the natural sorbent of sodium alginate. Regulation of the milk salt system, especially, the calcium content as an initial raw material for producing sour milk cheese by the change of the content and condition of calcium allowed to correct parameters of the process of sour milk cheese making and its functional-technological properties, especially, moisture-keeping ability, form stability and other. It was established, that the decrease of the calcium content in milk provides getting sour milk cheese with the soft, easily smearing consistence, without whey separation. The obtained data on the characteristic of organoleptic indicators fully correlate with studies of the microstructure and dispersity of sour milk cheese. It was determined, that milk decalcification results in raising dispersity of sour milk cheese at the synchronous increase of the percent content of protein particles with minimal size characteristics in the system. It was elucidated, that the microstructure of studied samples consists of protein grains of the same form, evenly distributed by the whole volume. Based on the obtained experimental data, there were corrected parameters of the technological process of sour milk cheese production. There were elaborated ways of formation of the culinary products assortment on the base of sour milk cheese, produced of decalcified milk.

Fortified tuna bone powder supplementation increases bone mineral density of lactating rats and their offspring.

Breastfeeding leads to bone calcium loss for milk production, resulting in progressive maternal osteopenia. Calcium supplement from natural sources has been postulated to be more beneficial to bone health than purified CaCO3 because natural sources also contain other nutrients such as certain amino acids that might enhance calcium metabolism. Herein, we examined the effect of calcium supplementation from tuna bone powder and CaCO3 on bones of dams and the offspring. Both forms of calcium supplement, i.e. tuna bone powder and CaCO3 , increased maternal bone mineral density (BMD). However, bone histomorphometry revealed that only tuna bone had beneficial effect on maternal bone microstructure, i.e. increased bone formation, decreased bone resorption and increased in bone volume. Regarding the mechanical properties, the decreased ultimate load in non-supplement lactating mothers was restored to the load seen in nulliparous animals by calcium supplementation. Moreover, both tuna bone and CaCO3 supplementation in mothers led to increased milk calcium concentration and consequently increased BMD in the growing offspring. Calcium supplement from tuna bone powder was effective in preventing maternal osteopenia. Tuna bone, which is a readily available fishing industrial waste, is a good alternative source of calcium supplement that increases BMD in both lactating mothers and the neonates. © 2017 Society of Chemical Industry.

Spine bone mineral density increases after 6months of exclusive lactation, even in women who keep breastfeeding.

The skeleton is resorbed during lactation to provide much of the calcium content of milk. After lactation ceases, these deficits in skeletal mineral content are largely restored, such that lactation has a neutral or protective effect against the long-term risk of low bone mineral density (BMD), osteoporosis, and fragility fractures. We hypothesized that a large observational study may identify the factors that predict a greater increase in BMD after lactation ceases. A pilot study was first needed to test feasibility and the magnitude of expected BMD change. We undertook Factors Affecting Bone formation after Breastfeeding Pilot (FABB Pilot), which enrolled women who had breastfed exclusively for 6months and planned to wean soon. The main outcome was change in BMD between enrolment and 6months later. Thirty-one women were recruited and completed both time points. Lumbar and thoracic spine BMD increased 4 and 5%, respectively; there was no significant change in femoral neck and total body BMD. Most women did not wean their babies as planned but continued to breastfeed multiple times per day. Despite this, a significant increase in BMD was seen in the subsequent 6months. Return of spontaneous menses and use of a progestin-only pill at recruitment were two potential signals that predicted a greater increase in BMD during the 6months after exclusive lactation. Spine BMD increased significantly during 6months following exclusive lactation and despite continued lactation. The factors that stimulate skeletal recovery remain to be identified.

Absence of Calcitriol Causes Increased Lactational Bone Loss and Lower Milk Calcium but Does Not Impair Post-lactation Bone Recovery in Cyp27b1 Null Mice.

We hypothesized that adaptation to calcium supply demands of pregnancy and lactation do not require calcitriol. Adult Cyp27b1 null mice lack calcitriol and have hypocalcemia, hypophosphatemia, and rickets. We studied wild-type (WT) and null sister pairs raised on a calcium-, phosphorus-, and lactose-enriched "rescue" diet that prevents hypocalcemia and rickets. Bone mineral content (BMC) increased >30% in pregnant nulls, declined 30% during lactation, and increased 30% by 4 weeks post-weaning. WT showed less marked changes. Micro-CT revealed loss of trabecular bone and recovery in both genotypes. In lactating nulls, femoral cortical thickness declined >30%, whereas endocortical perimeter increased; both recovered to baseline after weaning; there were no such changes in WT. Histomorphometry revealed a profound increase in osteoid surface and thickness in lactating nulls, which recovered after weaning. By three-point bend test, nulls had a >50% decline in ultimate load to failure that recovered after weaning. Although nulls showed bone loss during lactation, their milk calcium content was 30% lower compared with WT. Serum parathyroid hormone (PTH) was markedly elevated in nulls at baseline, reduced substantially in pregnancy, but increased again during lactation and remained high post-weaning. In summary, pregnant Cyp27b1 nulls gained BMC with reduced secondary hyperparathyroidism, implying increased intestinal calcium delivery. Lactating nulls lost more bone mass and strength than WT, accompanied by increased osteoid, reduced milk calcium, and worsened secondary hyperparathyroidism. This implies suboptimal intestinal calcium absorption. Post-weaning, bone mass and strength recovered to baseline, whereas BMC exceeded baseline by 40%. In conclusion, calcitriol-independent mechanisms regulate intestinal calcium absorption and trabecular bone metabolism during pregnancy and post-weaning but not during lactation; calcitriol may protect cortical bone during lactation. © 2017 American Society for Bone and Mineral Research.

Quality parameters of curd

The aim of this work was measurement of the curd firmness prepared by different volume of rennet solution and comparison of differences of curd firmness between these volumes. Further, it was observed the influence of different volumes of rennet up to thevolume of whey release, curd firmness, dry matter of curd and dry matter of whey. The composition of milk was determined according ISO and Czech state standard. Dry matter content (%) was determined by gravimetry, in drying oven at 102 °C to constant weight (ISO 6731:2010), the protein content (%) by Kjeldahl´s method (EN ISO 8968-1:2002), content of fat (%) by Gerber´s acidobutyrometric method (ISO 2446:2008), content of lactose by polarimetry, titratable acidity by titration Soxhlet-Henkel method, pH and calcium content in milk (g.L-1) was determined by complexometric titration with flueroxone as an indicator according to Czech state standart No 57 0530. For coagulation was used microbial rennet CHY-MAXRM 200. There were measured: curd firmness, rennet coagulation time, curd quality, volume of released whey, weight of curd, dry matter of curd and dry matter of whey. Different volumes of rennet solution had influence on curd firmness. Curd firmness (volume of rennet solution) had no significant influence on curd quality (five grade scale). Curd firmness had influence on volume of whey release (mL) out of the curd. With the increasing curd firmness s increased the volume of whey released from the curd. The volume of rennet solution had an influence on weight of curd. Curd dry matter raised with higher volume of rennet solution. Volume of added rennet solution had no statistically significant effect on the change of whey dry matter.

Up-regulation of milk secretion with modified microclimate through manipulating plasminogen-plasmin system in Murrah buffaloes during hot dry season.

The present study was aimed at determining changes in milk yield and composition along with the plasminogen-plasmin system of milk, plasma hormones, and metabolites of buffaloes during hot dry season (air temperature range 39.7 to 44.8°C) under two different management systems. Buffaloes were divided in two groups of six animals each: control and treatment, where treatment group animals accessed benefit of mist and fan cooling from 9:30 a.m. to 5:00 p.m., while control group animals were devoid of it. Duration of experiment was 6weeks. Under mist and fan cooling system, buffaloes experienced better comfort by alleviating environmental stress as their physiological responses such as rectal temperature, respiration rate, pulse rate, and forehead and middorsal temperatures were significantly (P<0.05) reduced compared to control, which subsequently resulted higher milk yield by 4.44% (P<0.001). Analysis of milk samples revealed higher concentration of plasminogen (7.99 vs 6.27μg/ml; P<0.01) and β-casein (1.09 vs 0.92g/dl; P<0.001) and lower plasmin level (0.178 vs 0.194μg/ml; P<0.05) in buffaloes under the treatment group compared to that under the control. Plasma glucose level was higher (P<0.001) by 21.08%, whereas cortisol, norepinephrine, and NEFA levels were lower (P<0.001) by 19.19, 15.38, and 11.41%, respectively, in treatment animals. However, exposure of buffaloes to cooling system did not alter composition and calcium content of milk, GH, and epinephrine level in plasma. Hence, it may be concluded that provision of cooling system during summer was effective to minimize environmental stress and improve milk production by manipulation of the PG-PL system in buffaloes.