The determination of vitamin D3 and 25-hydroxyvitamin D3 in early lactation and seasonal bovine milk

There is a need to account for the content of 25-hydroxyvitamin D₃ (25OH-D₃) in foods to more accurately estimate dietary vitamin D intake, given its higher biological activity. A high-performance liquid chromatography–tandem mass spectrometry method was applied to the determination of vitamin D₃ and 25OH-D₃ in bovine milk obtained during early lactation and over the course of a full milking season. In this seasonal study of bovine milk, vitamin D₃ levels ranged from 167 ng L⁻¹ in winter to 615 ng L⁻¹ in summer, whereas the content of 25OH-D₃ in bovine milk was <50 ng L⁻¹ and showed little variation. This study will provide manufacturers with data concerning endogenous vitamin D content that will enhance formulation capability related to the production of bovine-milk-based paediatric products.     

Fluorometric determination of free and total isocitrate in bovine milk

Isocitrate is an intermediate metabolite in the citric acid cycle found both inside the mitochondria as well as outside in the cytosolic shunt. Oxidation of isocitrate is believed to deliver large fractions of energy [i.e., reducing equivalents (NADPH) in the bovine udder] used for fatty acid and cholesterol synthesis. This study describes a new analytical method for determination of free and total isocitrate in bovine milk where time-consuming pretreatment of the sample is not necessary. Methods for estimation of both total isocitrate and free isocitrate are described, the difference being the esterified or even lactonized isocitrate. On average, 20% (6–27%) of cow milk isocitrate was esterified and free isocitrate correlated significantly with total isocitrate (r = 0.98). The present fluorometric determination correlated well with the traditional spectrophotometric determination of isocitrate. Milk samples from Danish Holstein cows (984) contained significantly less isocitrate than milk from Danish Jersey cows (760; i.e., 0.134 vs. 0.211 mmol/L). Isocitrate in milk is correlated to milk protein, fat, and citrate, and it is speculated, based on biochemistry, former studies, and the present, that isocitrate may reflect the energy situation in the mammary gland. The use of isocitrate as a biomarker of the energy status in the dairy cow is warranted.     

Concentrations of sialyloligosaccharides in bovine colostrum and milk during the prepartum and early lactation

Sialyloligosaccharides and sialylglycoconjugates in colostrum and milk are regarded to be important biological components with respect to be source of brain gangliosides in infant and to be antiinfectional components for the attack by the pathogenic bacteria and virus. Several acidic oligosaccharides have been characterised in both bovine and human milk or colostrum. The sialyloligosaccharide content of human colostrum and milk has been extensively studied, whereas that of cows milk and colostrum has received less attention. In this study, the concentrations of three sialyloligosaccharides of bovine colostrum and milk were determined at various stages during the prepartum and the first 7 d postpartum. The concentration of 3'SL (Neu5Ac(alpha2-3)Gal(beta1-4)Glc) reached a maximum value of 0.85 mg/ml immediately following parturition while the concentrations of 6'SL (Neu5Ac(alpha2-6)Gal(beta1-4)Glc) and 6'SLN (Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc) of 0.14 and 0.12 mg/ml, respectively, were much lower at this initial stage, although these concentration were maximum immediately following parturition. Bovine colostrum, especially that collected immediately after parturition, may be suitable as a source of 3'SL and other sialyloligosaccharides for use as additives by the food or pharmaceutical industries.     

Distribution of bovine milk sialoglycoconjugates during lactation

The sialoglycoconjugate content of human milk has been extensively studied. However, little attention has been paid to the changes occurring in these compounds in bovine milk during lactation. Since sialoglycoconjugates are very abundant in milk from the early stages of lactation, they have been suggested to be important for the nutrition of the newborn during the first months of life. The distribution of sialoglycoconjugates (expressed as glycoconjugate-bound sialic acid) from four different stages of lactation (colostrum, transitional, mature, and late-lactation milks) was investigated in four Spanish-Brown cows. All the fractions studied (total sialic acids, glycoproteins, oligosaccharides, casein, and gangliosides) showed a similar trend. We found the highest values in the colostrum, these decreasing in transitional and mature milks and increasing again in late-lactation milk. We also found a selective change in the relative contents of glycoprotein- and oligosaccharide-bound sialic acids. In mature milk, the latter increased up to 80% (59% in colostrum) and the former decreased to 3.9% (35.3% in colostrum). It would appear that the decrease in oligosaccharide-bound sialic acid is compensated by the increase in glycoprotein-bound sialic acid. From these results, it is deduced that newborn infants or calves fed with infant formulas or milk replacers, respectively, should be supplemented with sialoglycoconjugates to approximate the composition of human and cow milk as far as is practicable.     

Comparison of total and free cortisol in bovine serum and milk or colostrum

Total (free plus protein-bound) and free cortisol concentrations in paired samples of serum and skim milk or colostrum were determined by specific radioimmunoassay after extraction or ultrafiltration. For 11 cows in established lactation mean total cortisol concentrations +/- SE in serum and milk were 4.5 +/- .7 ng/ml and .35 +/- .06 ng/ml, respectively. Concentrations of free cortisol in serum and milk were about .3 ng/ml, which is at the lower limit of the present assay. Following 200 IU Synacthen injection to 5 cows, total cortisol in serum and milk rose to 67 +/- 6.0 ng/ml and 11.4 +/- 1.5 ng/ml by 8 h postinjection, while free concentrations increased to 4.3 +/- .7 ng/ml and 6.5 +/- .8 ng/ml in serum and milk, respectively. Eight additional cows were sampled at 1 to 2 d after parturition, and total cortisol in serum and colostrum was 16.6 +/- 1.6 ng/ml and 4.4 +/- 1.3 ng/ml, and free cortisol was 2.4 +/- .4 ng/ml and 1.8 +/- .5 ng/ml, respectively. Free cortisol concentrations in colostrum or in milk from cows in established lactation, before or after adrenal stimulation, are directly related to free cortisol concentrations in the blood, while the bound cortisol in milk is more related to these two stages of lactation rather than the bound hormone in the blood. Measurement of free cortisol in milk should allow the monitoring of changes in plasma free cortisol in studies of stress in dairy cows.     

Glycosidase activities in bovine milk over lactation

The presence and activity of glycosidases in Irish bovine milk over three months of lactation was investigated. A low level of variation between animals was observed and the highest level of glycosidase activity was present in colostrum, decreasing through transitional milk production to minimal but constant levels in mature milk. N-acetyl-β-d-glucosaminidase, α-l-fucosidase, α-galactosidase and N-acetyl-neuraminidase appear to be the most biologically relevant glycosidases in bovine milk. The elevated levels of enzymatic activity in colostrum suggests the milk glycosidases may play a role in the digestion of bovine milk glycans in the infant mammal, possibly acting as substitutes for bacterial glycosidases prior to colonisation by the gut microflora, which are involved in in vivo oligosaccharide metabolism in the lower gastrointestinal tract.     

Changes in physical properties of bovine milk from the colostrum period to early lactation

The aim of this study was to analyze individual cows’ samples from the colostrum, postcolostrum, and early lactation periods to investigate how milk composition, physical properties, stability, and suitability for processing change throughout this period. Attention was paid to the first week postpartum in which the composition of bovine mammary secretion can change markedly. Properties including pH, titratable acidity, ethanol stability (ES), rennet clotting time, and casein micelle size were analyzed, together with some compositional factors such as fat, total protein, lactose, total and ionic calcium, magnesium, citrate, phosphorus, sodium, and potassium. Total Ca (36.2 mM) and free ionic Ca (2.58 mM), Mg (5.9 mM), P (32.2 mM), and Na (24.1 mM) appeared to be high on d 5 postpartum, having decreased substantially over the first 5 d; they gradually decreased thereafter. The average pH on d 5 was only 6.49, compared with 6.64 at 1 mo postpartum. Stability measurements showed that the average ES on d 5 was 70% and the rennet clotting time was 12.2 min, which were significantly lower than values at later stages. A number of milk properties including ES, pH, protein content, and Ca²⁺ concentration could be useful for identifying the point of transition from colostrum to the early lactation period. Knowing the composition and physical properties of colostrum and postcolostrum secretions will help establish when such milk is suitable for processing and determine the best use for that milk.     

Effect of stage of lactation, stage of pregnancy, milk yield and herd management on seasonal variation in spontaneous lipolysis in bovine milk

The free fatty acid (FFA) levels after milking (initial FFA) and after 22 h storage at 4 degrees C (FFA-22) were determined in milk from 57 cows every 2 weeks for one year. FFA levels which were higher in summer than in winter were explained by later stages of lactation occurring in summer. Initial FFA content increased regularly during lactation. FFA-22 content increased after 12 weeks, and further after 32 weeks of lactation. The first increase was due to stage of lactation. The second increase, which appeared in late lactation, was essentially due to the stage of pregnancy combined with the effect of milk yield. FFA-22 content increased in the second part of pregnancy, chiefly after 24 weeks. A low milk yield (less than or equal to 5 kg) further increased lipolysis, but only after 16 weeks of pregnancy. The effect of stage of pregnancy may have been enhanced by management factors such as feeding conditions. In this investigation, the seasonal FFA variation in bulk tank milk could be explained entirely by physiological factors.     

Associations of bovine blood and milk polymorphisms with lactation traits: Guernseys

First lactation milk yield and percentages of fat, solids-not-fat, and protein were analyzed in Guernsey cows to determine relationships of production traits to genetic markers at 16 polymorphic loci. The polymorphic systems examined were blood groups A, B, C, F, J, L, M, S, and Z; blood proteins transferrin, hemoglobin, and alkaline phosphatase; and milk proteins beta-lactoglobulin, alpha s1-casein, beta-casein, and kappa-casein. Different statistical models were utilized to evaluate direct genetic marker effects, linkage group effects, and heterozygosity effects. There were many indications of relationship with milk composition traits but for milk yield only for A system direct effects and for F system linkage effects. Pronounced associations between markers and component percentages were noted for the J, Z, and beta-lactoglobulin systems with fat percentage, for the M system with fat and solids-not-fat percentages, for the alkaline phosphatase system with solids-not-fat percentage and protein percentages, and for L and alpha s1-casein systems with protein percentage. Additionally, the interaction of beta-lactoglobulin and alpha s1-casein markers was significant for deviations of percent fat and percent solids-not-fat.     

Associations of bovine blood and milk polymorphisms with lactation traits: Holsteins

First lactation milk yield and percentages of fat, solids-not-fat, and protein were analyzed to determine the possible relationships between 14 polymorphic loci and production in Holstein cows. The polymorphic systems examined were blood groups (A, B, C, F, J, L, M, S, and Z), serum transferrin, and milk proteins (beta-lactoglobulin, alpha s1-casein, beta-casein, and kappa-casein). Several statistical models were utilized. Although results differed according to the analysis conducted, in general, no system had a significant association with first lactation milk yield expressed as a herdmate deviation. Most striking were the relationships between milk protein polymorphisms and percent solids-not-fat and protein deviations; beta-casein and kappa-casein alleles had statistically significant associations with these traits. The F system was significant for percent fat deviations, whereas J x L system interactions were significant for all traits. Degree of heterozygosity over the 14 systems was positively associated with percent protein deviations.     

Variations in bovine milk oligosaccharides during early and middle lactation stages analyzed by high-performance liquid chromatography-chip/mass spectrometry

Milk oligosaccharides (OS) are not only a source of nutrition for newborns, but also provide numerous important biological functions including the prevention of pathogen binding to the intestinal epithelium and serving as nutritive sources for beneficial bacteria. High-performance mass spectrometry and separation methods were used to evaluate changes of bovine milk oligosaccharides (bMO) in different lactation stages. Previously, 40 bMO were identified in bovine milk with many consisting of short oligomeric chains that were less complex than human milk oligosaccharides (hMO). The bMO are also significantly more anionic than hMO, with nearly 70% in measured abundances containing either N-acetylneuraminic acid or N-glycolylneuraminic acid, and no fucosylated OS. In this study, we examined factors that could affect the abundances of bMO including stage of lactation and breed. The total concentrations dropped rapidly in the first several days of lactation. Moreover, the anionic oligosaccharides (including N-glycolylneuraminic acid) decreased more rapidly compared with the neutral oligosaccharides.     

The effects of increased milking frequency during early lactation on milk yield and milk composition on commercial dairy farms

Increased milking frequency (IMF) during early lactation has the potential for carryover responses following the return to normal herd milking frequency. The objective was to determine the consistency of response of cows in commercial dairy farms to IMF during early lactation. Cows (n = 398) were assigned randomly at calving within each of the 4 participating farms to 1 of 2 treatments. The control group was milked twice-daily (2×) during the entire lactation. The IMF group was milked 4-times daily (4×) starting on d 1 to 7, depending on farm, until d 21 postcalving and 2× thereafter. Cows in the IMF group were milked at the beginning and again at the end of the normal milking routine. Milking intervals differed across the farms for the 4× cows with a minimum interval of 3.5, 4.0, 5.0, and 6 h for each of the 4 farms, respectively. The milk yield of cows subjected to IMF increased by 2.2 ± 0.4 kg/d during the first 7 mo of lactation. Interactions of treatment with lactation group (primiparous vs. multiparous) were not significant. Although percentages of fat and protein in milk were decreased by early lactation IMF (3.69% ± 0.03 fat and 3.05% ± 0.02 true protein for control vs. 3.57% ± 0.03 fat and 2.99% ± 0.02 true protein for IMF), overall yields of protein were increased by IMF (1.02 ± 0.01 vs. 0.98 ± 0.01 kg/d). Early lactation IMF did not affect udder health as assessed by somatic cell count linear score. Cows subjected to IMF were 1.4 times more likely classified as subclinically ketotic than the control cows. Early lactation IMF has the potential to increase milk yield on commercial dairy farms. Although the direction of response was the same on all farms, the magnitude of the response was different among farms and appears influenced by management practices specific to each farm, which included, but were not limited to, housing system, stocking density, nutrition, genetics, and other covariates differing among farms.     

Angiogenin content in human milk in the early period of lactation

The content of angiogenin in human milk and dairy produce for feeding of children of the first year of life is investigated. It is revealed, that the highest concentration of angiogenin in human milk takes place in colostric period (18.00 +/- 0.72 mg/l). During the subsequent time of lactation the concentration of angiogenin keeps at a level 2.00 +/- 0.06 mg/l. In products of infant's feeding the angiogenin either was absent, or its concentration was much lower, than in breast milk.     

Impact of early lactation somatic cell count in heifers on milk yield over the first lactation

The objective of this study was to estimate the impact of somatic cell count (SCC) in early lactation (SCCel) [measured between 5 to 14 d in milk (DIM)] of dairy heifers on test-day milk yield (MY) during the first lactation.In total, 117,496 four-weekly test-day records of 14,243 heifers were used. A multilevel regression analysis, which included test-day SCC among the explanatory variables, revealed that an increase by one unit of the natural log-transformed SCCel (LnSCCel) was on average associated with a decrease in MY of 0.13 kg/d later in lactation. As an example, a heifer with an SCCel of 50,000 cells/mL measured at 10 DIM was estimated to produce 119 and 155 kg more milk during its first lactation than heifers with a SCCel of 500,000 and 1,000,000 cells/mL, respectively. When not accounting for test-day SCC, the effect of LnSCCel on MY was larger, indicating that part of the negative impact of elevated SCCel was associated with elevated test-day SCC later in lactation.Furthermore, an elevated SCCel at 14 DIM had a larger impact than an equally elevated SCCel measured at an earlier DIM. In addition, the negative effect of an elevated SCCel remained present during almost the entire first lactation in a subgroup of heifers with a second test-day SCC 相似文献   

Genetic relationships between weight loss in early lactation and daily milk production throughout lactation in Holstein cows

After calving, high-yielding dairy cows mobilize body reserves for energy, sometimes to the detriment of health and fertility. This study aimed to estimate the genetic correlation between body weight loss until nadir and daily milk production (MY24) in first- (L1) and second-lactation (L2) Holstein cows. The data set included 859,020 MY24 records and 570,651 daily raw body weight (BWr) phenotypes from 3,989 L1 cows, and 665,361 MY24 records and 449,449 BWr phenotypes from 3,060 L2 cows, recorded on 36 French commercial farms equipped with milking robots that included an automatic weighing platform. To avoid any bias due to change in digestive content, BWr was adjusted for variations in feed intake, estimated from milk production and BWr. Adjusted body weight was denoted BW. The genetic parameters of BW and MY24 in L1 and L2 cows were estimated using a 4-trait random regression model. In this model, the random effects were fitted by second-order Legendre polynomials on a weekly basis from wk 1 to 44. Nadir of BW was found to be earlier than reported in the literature, at 29 d in milk, and BW loss from calving to nadir was also lower than generally assumed, close to 29 kg. To estimate genetic correlations between body weight loss and production, we defined BWL5 as the loss of weight between wk 1 and 5 after calving. Genetic correlations between BWL5 and MY24 ranged from −0.26 to 0.05 in L1 and from −0.11 to 0.10 in L2, according to days in milk. These moderate to low values suggest that it may be possible to select for milk production without increasing early body mobilization.     

Fatty acid composition of milk from multiparous Holstein cows treated with bovine somatotropin and fed n-3 fatty acids in early lactation

Multiparous cows (n = 59) were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine effects of bovine somatotropin (bST; Posilac, Monsanto Animal Agricultural Group, St. Louis, MO) and source of dietary fat on milk fatty acid composition during the first 140 d in milk. Diets were provided from calving and included whole, high-oil sunflower seeds (SS; 10% of dietary dry matter; n-6/n-3 ratio of 4.6) as a source of linoleic acid or a mixture of Alifet-High Energy and Alifet-Repro (AF; Alifet USA, Cincinnati, OH; 3.5 and 1.5% of dietary dry matter, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids (15.7% 18:3, 1.3% 20:5, and 1.3% 22:6). Treatments were derived from a 2 × 2 combination of supplemental fat source (SS, AF) and with 0 (SSN, AFN) or 500 (SSY, AFY) mg of bST administered every 10 d from 12 to 70 d in milk and at 14-d intervals thereafter. Milk fatty acid composition was determined in samples collected from 32 cows (8 complete blocks) during wk 2, 8, and 20 of lactation. Data were analyzed as repeated measures using mixed model procedures to determine the effects of diet, bST, week of lactation, and their interactions. Proportions of 18:3 (4.02 vs. 3.59 ± 0.16%), 20:5 (0.52 vs. 0.41 ± 0.02%), and 22:6 (0.11 vs. 0.02 ± 0.02%) were greater and the n-6/n-3 fatty acid ratio (7.40 vs. 8.80 ± 0.30) was reduced in milk from cows fed AF compared with SS. Proportions of de novo-synthesized fatty acids increased and preformed fatty acids decreased as lactation progressed, but bST administration delayed this shift in origin of milk fatty acids. Transfer efficiency of 18:3, 20:5, and 22:6 from AF to milk fat averaged 36.2, 4.9, and 5.2%, respectively. These efficiencies increased as lactation progressed, but were delayed by bST. Apparent mammary Δ⁹-desaturase activity and milk conjugated linoleic acid (cis-9, trans-11 conjugated linoleic acid) content increased through the first 8 wk of lactation. Based on the product-to-substrate ratio of 14:1/14:0 fatty acids in milk, there was an interaction of diet and bST because bST decreased apparent Δ⁹-desaturase activity in SSY cows but increased it in AFY cows (0.10, 0.09, 0.08, and 0.09 ± 0.01 for SSN, SSY, AFN, and AFY, respectively). Feeding Alifet-Repro increased n-3 fatty acids in milk and bST prolonged the partitioning of dietary fatty acids into milk fat.     

Genetic improvement of total milk yield and total lactation persistency of the first three lactations in dairy cattle

The objective of this study was to compare 6 selection criteria in terms of 3-parity total milk yield and 9 selection criteria in terms of total net merit (H) comprising 3-parity total milk yield and total lactation persistency. The 6 selection criteria compared were as follows: first-parity milk estimated breeding value (EBV; M1), first 2-parity milk EBV (M2), first 3-parity milk EBV (M3), first-parity eigen index (EI₁), first 2-parity eigen index (EI₂), and first 3-parity eigen index (EI₃). The 9 selection criteria compared in terms of H were M1, M2, M3, EI₁, EI₂, EI₃, and first-parity, first 2-parity, and first 3-parity selection indices (I₁, I₂, and I₃, respectively). In terms of total milk yield, selection on M3 or EI₃ achieved the greatest genetic response, whereas selection on EI₁ produced the largest genetic progress per day. In terms of total net merit, selection on I₃ brought the largest response, whereas selection EI₁ yielded the greatest genetic progress per day. A multiple-lactation random regression test-day model simultaneously yields the EBV of the 3 lactations for all animals included in the analysis even though the younger animals do not have the opportunity to complete the first 3 lactations. It is important to use the first 3 lactation EBV for selection decision rather than only the first lactation EBV in spite of the fact that the first-parity selection criteria achieved a faster genetic progress per day than the 3-parity selection criteria. Under a multiple-lactation random regression animal model analysis, the use of the first 3 lactation EBV for selection decision does not prolong the generation interval as compared with the use of only the first lactation EBV. Thus, it is justified to compare genetic response on a lifetime basis rather than on a per-day basis. The results suggest the use of M3 or EI₃ for genetic improvement of total milk yield and the use of I₃ for genetic improvement of total net merit H. Although this study deals with selection for 3-parity milk production, the same principle applies to selection for lifetime milk production.     

Relationships of first lactation milk and type traits to cow survival and a sire index for discounted total milk

The probability of cow survival during each of six consecutive 13-mo periods after first calving was regressed on lactation milk yield and 15 type traits, each recorded during the first lactation. Adjusted coefficients of determination were small (.028 to .081). The ratio of variance in predicted cow survival probabilities due to milk only with that due to the 15 type traits was 12.6:1, 4.7:1, 2.5:1, .5:1, 0:1, and .02:1 for respective herdlife periods. Maximum effect of type traits on herdlife ranged from 11 to 109 d. Prediction equations for cow survival were incorporated into a sire index for discounted total milk yield of progeny. Type traits affected the sire index by their influence on the six predicted survival rates. Milk yield affected the discounted total milk index directly as well as through the survival rates. Simulated variation from milk estimated transmitting abilities for sires accounted for 99.9% of the total variation in the discounted total milk index. Since the effect of the type traits on cow survival rates was greatest during the later herdlife periods, too few animals would have survived to these later periods to reveal any significant effect from type on the discounted total milk index.