Short communication: Comparative estimation of colostrum quality by Brix refractometry in bovine, caprine, and ovine colostrum.

Newborn ungulates depend on the timely supply of colostrum containing sufficient immunoglobulins to obtain passive immunity against disease. Brix refractometry enables a rapid on-farm estimation of colostrum quality and has been intensively studied in bovines. However, the suitability of Brix refractometers for assessing colostrum quality in goats and ewes has been scarcely evaluated. The present study compared bovine, caprine, and ovine colostrum quality estimation using an optical Brix refractometer. In addition, between-species variations in the relationships between Brix values and colostrum constituents (IgG, fat, protein, and lactose) and the accuracy of Brix refractometry at different cutoff values were evaluated by a receiver operating characteristic curve analysis. We measured the Brix value and contents of IgG, fat, protein, and lactose in 324 colostrum samples (108 cows, 116 does, and 100 ewes). Thresholds for classification of good colostrum quality (as determined by ELISA) were set at 50 mg IgG/mL in cows and 20 mg/mL in does and ewes. Bovine colostrum showed the greatest IgG concentrations compared with caprine and ovine colostrum. Fat and protein content was higher in sheep colostrum compared with the other species, whereas the highest lactose concentrations were detected in goat colostrum. Brix values ranged from 11.4 to 34.6% (22.1 ± 4.2%; mean ± standard deviation), 15.4 to 40.0% (28.5 ± 6.8%), and 8.8 to 39.8% (21.6 ± 5.3%) in bovine, ovine, and caprine colostrum, respectively. In all 3 species, Brix was highly correlated with IgG and protein concentrations (cows, r = 0.83 and 0.98; goats, r = 0.83 and 0.89; sheep, r = 0.75 and 0.87). Optimal cutoff points for greatest accuracy of Brix measurements were 19.3% Brix in cows [with 87.1% sensitivity (Se) and 100% specificity (Sp)], 20.7% Brix in does (with 53.5% Se and 100% Sp), and 26.5% Brix in ewes (with 75% Se and 91.3% Sp). In conclusion, Brix refractometry is an acceptable tool for on-farm estimations of colostrum quality in does and ewes despite distinct between-species variations in colostrum composition.

Pattern of milk yield and immunoglobulin concentration and factors associated with colostrum quality at the quarter level in dairy cows after parturition.

First colostrum yield and constituents as well as milk yield during established lactation vary considerably among mammary quarters in dairy cows. However, data on the development of milk yield, IgG concentration, and their distribution per quarter within cows during the first milkings after calving are scarce. We analyzed milk production and IgG concentration at the individual quarter level in 29 multiparous Holstein cows during the first 5 milkings after calving. Cow- and calf-related factors (time interval between calving and first milking, parity number, previous lactation yield, gestation length, dry period length, sex, and birth weight of the calf) potentially affecting first colostrum quality and quantity were assessed. Milking of first colostrum was carried out between 30 and 180 min after parturition. Further milkings were performed twice daily. Quarter milk yield varied between 0.1 and 5.5 kg at the first milking and between 1.4 and 5.1 kg at the fifth milking relative to parturition. Quarter IgG concentration ranged between 18.8 and 106.0 mg/mL at the first milking and between 0.8 and 46.1 mg/mL at the fifth milking. Distribution of milk yield and IgG concentration among quarters was not entirely repeatable during the first 5 successive milkings after parturition; that is, the ranking of quarters changed (intraclass correlation coefficients for quarter milk yield and IgG concentration: 0.64 and 0.79, respectively). The average hourly milk production increased in all quarters, ranging from 0.02 to 0.26 kg/h between the first 2 milkings up to 0.11 to 0.45 kg/h between the fourth and fifth milkings. First colostrum yield was not affected by any of the evaluated cow- and calf-related factors. Quarter colostrum IgG concentration was higher in cows with a higher previous lactation yield, whereas a lower colostrum IgG content was observed in cows with a longer gestation period and consequently heavier calves. In conclusion, milk yield and IgG concentration of individual quarters varied considerably, and their distribution among quarters within cows was moderately repeatable in consecutive milkings and changed partially over time. The decline of IgG concentration was independent of the concomitant increase in milk secretion, with changes occurring at different rates in individual quarters. Our results confirm the independence of the single mammary quarters at the onset of lactation despite an identical exposure to endocrine stimuli.

Immunoglobulin G content and colostrum composition of different goat and sheep breeds in Switzerland and Germany.

Colostrum represents the sole source to acquire humoral immunity and is an important energy source for newborn lambs and goat kids. However, colostrum composition (i.e., the contents of IgG, fat, protein, and lactose) is affected by various factors such as parity and litter size and, potentially, by breed. In the present study, we examined the colostrum composition of different goat and sheep breeds raised for milk and meat production in Switzerland and Germany. Ten goat breeds (Anglo-Nubian, Appenzell, Boer, Bunte Deutsche Edelziege, Chamois-colored, Grisons Striped, Peacock, Saanen, Toggenburg, and Valais Blackneck) and 10 sheep breeds (Brown-Headed Meat, East Friesian Milk, German Blackheaded Mutton, Gray Horned Heath, Lacaune Dairy, Merino Land, Swiss Black-Brown Mountain, Swiss Charollais, Swiss White Alpine, and Valais Blacknose) were involved in this study. First colostrum samples were obtained from ewes (n = 100) and goats (n = 116) between 10 and 390 min after parturition and analyzed for total IgG, fat, protein, and lactose contents. Colostral IgG concentrations varied between 4.8 and 75.0 mg/mL in goats, and between 6.2 and 65.4 mg/mL in ewes, and the time interval between milking and parturition did not affect colostral IgG concentrations. In goats, the highest IgG concentrations were found in Boer (meat-type; 61.0 ± 10.3 mg/mL; mean ± SD) and the lowest concentrations were observed in Bunte Deutsche Edelziege (milk-type; 26.5 ± 12.5 mg/mL). In sheep, East Friesian Milk and Lacaune Dairy showed the lowest colostral IgG concentrations (17.9 ± 7.3 and 20.2 ± 8.0 mg/mL, respectively), and the highest values were observed in the Merino Land breed (44.2 ± 15.7 mg/mL). The lowest fat and protein concentrations and concomitantly highest lactose concentrations were observed in colostrum of East Friesian Milk and Lacaune Dairy sheep. Parity number did not affect colostrum composition in sheep or goats. In contrast, colostral fat content was higher in ewes bearing twins and triplets than in those carrying singletons. Increasing litter size tended to be associated with higher protein and lower lactose concentrations in ovine (i.e., singletons vs. twins vs. triplets) and caprine colostrum (i.e., singletons vs. twins), whereas colostral IgG concentrations were not affected by litter size. In conclusion, IgG and concentrations of other colostrum constituents showed a wide range in goats and ewes and were mainly affected by the type of breed.

Short communication: Mammary gland tight junction permeability after parturition is greater in dairy cows with elevated circulating serotonin concentrations.

After parturition, the start of copious milk production in dairy cows requires the closure of tight junctions (TJ) to form the blood-milk barrier and prevent paracellular transfer of blood constituents into milk [e.g., lactate dehydrogenase (LDH) and serum albumin (SA)] and vice versa [e.g., appearance of α-lactalbumin (α-LA) in blood]. Serotonin (5-HT) has been demonstrated to alter tight junction permeability in the mammary gland. The present study investigated individual differences of TJ permeability of mammary epithelium at the beginning of lactation in relation to circulating 5-HT in dairy cows. Blood and milk samples were obtained from 11 multiparous Holstein dairy cows for the first time at 4 h after parturition, at the following 5 milkings, and at the evening milkings on d 5, 8, 10, and 14 of lactation. Retrospectively, cows were split into 2 groups according to their calculated areas under the curve of serum 5-HT during the entire experimental period: a high-serum 5-HT (HSS) group (5 cows) and a low-serum 5-HT (LSS) group (6 cows). The areas under the curve of serum 5-HT concentrations over the 324-h experimental period were 62 ± 2 × 103 ng/mL in HSS and 25 ± 5 × 103 ng/mL in LSS. Plasma α-LA concentration was greater in LSS than in HSS cows at the first milking, but no difference between groups was found from the second to sixth milking. Yield of α-LA in milk was lower in HSS than in LSS during the first 6 milkings postpartum, especially in colostrum. Concentrations of α-LA, IgG1, and IgG2 in milk did not differ between groups during the entire experiment except for higher IgG observed in LSS than in HSS at the second milking and for higher IgG2 found in HSS compared with LSS on d 5. In contrast, SA concentrations and LDH activity in milk were lower in LSS compared with HSS cows during the first 6 milkings postpartum, particularly in colostrum. Milk somatic cell count was higher in HSS than in LSS throughout the study. Higher circulating 5-HT concentrations were associated with an increased transfer of the paracellularly transported SA, LDH, and somatic cell count, especially at the first milking, suggesting that 5-HT affects TJ permeability during closure of the blood-milk barrier at the onset of lactation. Furthermore, higher serum 5-HT concentrations were associated with a lower α-LA yield in milk. A consistent relationship with serum 5-HT concentrations was neither observed for the transfer of IgG2 nor the primarily transcellular transport of IgG1 during the first milkings after parturition.

Short communication: Circulating serotonin is related to the metabolic status and lactational performance at the onset of lactation in dairy cows.

Serotonin (5-hydroxytryptamine, 5-HT) affects many physiological functions because it is involved in glucose and lipid metabolism, calcium homeostasis, and regulation of lactation in dairy cows. This study aimed to examine physiological differences in serum 5-HT concentrations (high vs. low) and their association with metabolic status and milk production at the onset of lactation. Twelve multiparous Holstein dairy cows were milked within 4 h of calving, and blood and milk samples were collected at the first 6 subsequent milkings after parturition and at the evening milkings on d 5, 8, 10, and 14. Cows were retrospectively divided into 2 groups (6 cows/group): low serum 5-HT (LSS) and high serum 5-HT (HSS) according to their calculated areas under the curve (AUC) for serum 5-HT for the entire experimental period (cut-off: 46,000 ng/mL × 324 h). Concentrations of 5-HT, free fatty acids (FFA), ß-hydroxybutyrate (BHB), glucose, calcium, and IGF-1 were measured in blood. Milk was analyzed for fat, protein, lactose, and 5-HT concentrations. Milk yield was recorded at each milking and energy-corrected milk yield was calculated. Serum 5-HT concentrations were higher in HSS than in LSS [AUC (ng/mL × 324 h): 57,830 ± 4,810 vs. 25,005 ± 5,930]. The amount of energy-corrected milk was lower in HSS than in LSS. The HSS group produced less colostrum and had decreased milk yield, specifically during the first 6 milkings. Concentrations of FFA, BHB, and glucose in plasma did not differ between groups. Concentrations of IGF-1 in serum were elevated in HSS compared with LSS throughout the experiment. Total circulating calcium concentrations in serum tended to be higher in HSS than in LSS. Milk fat and protein yields were decreased in HSS compared with LSS. Milk 5-HT decreased overall during the experimental period, with LSS maintaining higher 5-HT concentrations than HSS until d 14 of lactation. In conclusion, cows with high serum 5-HT concentrations showed a reduced metabolic load at the onset of lactation, concomitantly lower milk yield, and a reduced energy output via milk.

Hyperglycaemia in transition dairy cows: Effects of lactational stage and conjugated linoleic acid supplementation on glucose metabolism and turnover.

Supplementing conjugated linoleic acid (CLA) is supposed to spare glucose due to the milk fat-depressing effect of the trans-10, cis-12 CLA isomer, and allows repartitioning nutrients despite an energy deficiency in early lactation. However, there is still a lack of knowledge in terms of the dynamic pattern of the glucose turnover in transition dairy cows. We hypothesized that dairy cows supplemented with CLA have an altered rate of glucose turnover and insulin sensitivity during early lactation. We conducted three consecutive hyperglycaemic clamps (HGC) in weeks -2, +2 and +4 relative to parturition in Holstein cows supplemented daily either with 70 g of lipid-encapsulated CLA (6.8 g trans-10, cis-12 and 6.6 g of the cis-9, trans-11 CLA isomer; CLA; n = 11) or with 56 g of control fat (CON; n = 11). From week -3 up to week +4 relative to parturition, milk yield and dry matter intake (DMI) were recorded daily, while body weight (BW) and milk composition were obtained once weekly. Blood samples were taken once weekly and every 30 min during the HGC. Plasma was analysed for concentrations of glucose, fatty acids (FFA), beta-hydroxybutyrate (BHB), insulin, triglycerides and cholesterol. The CLA supplementation did not affect performance and metabolic parameters except for BHB and cholesterol. Furthermore, insulin concentrations and insulin sensitivity were affected by treatment. During the HGC in early lactation, insulin response was lower and decrease in FFA and BHB greater compared with the HGC in week -2 although glucose target concentration achieved during the steady-state period was similar for all three HGC. Our findings in terms of insulin and cholesterol suggest that body reserves are preserved through CLA feeding without restraining animal's performance. Furthermore, CLA effects on cholesterol and triglyceride concentrations indicated beneficial effects on hepatic lipid export contributing to an improved efficiency of prevailing metabolites in circulation.

Quarter vs. composite colostrum composition assessed by Brix refractometry, specific gravity and visual color appearance in primiparous and multiparous dairy cows.

The control of colostrum quality is essential for successful calf rearing. Instruments for on-farm colostrum quality determination are mostly utilized for testing composite colostrum samples, but do not take potential variation between quarters into account. In cases of low composite colostrum quality, feeding of better quality colostrum from individual quarters might be beneficial. The objective of the present study was to identify relationships between colostrum color, colostrum quality and composition. Besides laboratory methods, a colostrometer and a Brix refractometer were used to assess colostrum quality at quarter levels. Quarter and composite colostrum samples from 17 primiparous and 11 multiparous Holstein cows were analyzed for total IgG, fat, protein and lactose content; color was measured by a spectrophotometer. In the present study, an IgG concentration below 50 g/L as determined by ELISA was found in 14.3% of the analyzed quarter samples. Concentration and mass of IgG in composite colostrum samples were greater in multiparous compared with primiparous cows. Specific gravity (SG) of colostrum of individual and composite samples was lower in primiparous compared with multiparous cows. Milk fat content was greater in quarter and composite colostrum samples of primiparous compared with multiparous dairy cows. No clear relationships between IgG content and SG, Brix, and the color space coordinates L*, a*, and b* were detected. Interestingly, results indicate that despite a similar range of the variables investigated, correlations between those parameters can differ at quarter compared to composite level. Not only for SG and Brix determination, but also for the color space coordinates measured, correlation coefficients with IgG concentration of the respective samples were greater at a composite compared with the individual quarter level. In conclusion, accuracy and limitations of on-farm instruments estimating colostrum quality apply to both quarter colostrum samples and composite evaluations. Identification of quarters with superior colostrum quality would possibly be a way to improve the immunization of newborn calves. However, the potential on-farm methods validated in the present study to estimate quarter colostrum quality are not sufficiently sensitive to distinguish between quarters. This is due to the variation of gross colostrum composition between individual quarters of a cow.

Cholesterol metabolism, transport, and hepatic regulation in dairy cows during transition and early lactation.

The transition from the nonlactating to the lactating state represents a critical period for dairy cow lipid metabolism because body reserves have to be mobilized to meet the increasing energy requirements for the initiation of milk production. The purpose of this study was to provide a comprehensive overview on cholesterol homeostasis in transition dairy cows by assessing in parallel plasma, milk, and hepatic tissue for key factors of cholesterol metabolism, transport, and regulation. Blood samples and liver biopsies were taken from 50 multiparous Holstein dairy cows in wk 3 antepartum (a.p.), wk 1 postpartum (p.p.), wk 4 p.p., and wk 14 p.p. Milk sampling was performed in wk 1, 4, and 14 p.p. Blood and milk lipid concentrations [triglycerides (TG), cholesterol, and lipoproteins], enzyme activities (phospholipid transfer protein and lecithin:cholesterol acyltransferase) were analyzed using enzymatic assays. Hepatic gene expression patterns of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGC) synthase 1 (HMGCS1) and HMGC reductase (HMGCR), sterol regulatory element-binding factor (SREBF)-1 and -2, microsomal triglyceride transfer protein (MTTP), ATP-binding cassette transporter (ABC) A1 and ABCG1, liver X receptor (LXR) α and peroxisome proliferator activated receptor (PPAR) α and γ were measured using quantitative RT-PCR. Plasma TG, cholesterol, and lipoprotein concentrations decreased from wk 3 a.p. to a minimum in wk 1 p.p., and then gradually increased until wk 14 p.p. Compared with wk 4 p.p., phospholipid transfer protein activity was increased in wk 1 p.p., whereas lecithin:cholesterol acyltransferase activity was lowest at this period. Total cholesterol concentration and mass, and cholesterol concentration in the milk fat fraction decreased from wk 1 p.p. to wk 4 p.p. Both total and milk fat cholesterol concentration were decreased in wk 4 p.p. compared with wk 1 and 14 p.p. The mRNA abundance of genes involved in cholesterol synthesis (SREBF-2, HMGCS1, and HMGCR) markedly increased from wk 3 a.p. to wk 1 p.p., whereas SREBF-1 was downregulated. The expression of ABCA1 increased from wk 3 a.p. to wk 1 p.p., whereas ABCG1 was increased in wk 14 p.p. compared with other time points. In conclusion, hepatic expression of genes involved in the biosynthesis of cholesterol as well as the ABCA1 transporter were upregulated at the onset of lactation, whereas plasma concentrations of total cholesterol, phospholipids, lipoprotein-cholesterol, and TG were at a minimum. Thus, at the gene expression level, the liver seems to react to the increased demand for cholesterol after parturition. Whether the low plasma cholesterol and TG levels are due to impaired hepatic export mechanisms or reflect an enhanced transfer of these compounds into the milk to provide essential nutrients for the newborn remains to be elucidated.

Peripartal progesterone and prolactin have little effect on the rapid transport of immunoglobulin G into colostrum of dairy cows.

Colostrum formation and lactogenesis in the mammary gland and the timing of parturition are regulated by endocrine signals. Changes in progesterone (P4) and prolactin (PRL) are considered key events that inhibit colostrum formation, trigger parturition, and signal the onset of lactation. The goal of our study was to determine if colostrum yield and composition and immunoglobulin transfer are affected by prepartum milking relative to the decrease in P4, peak of PRL, or occurrence of parturition. Twenty-three multiparous cows were randomly assigned to 1 of 2 groups: (1) control with first milking at 4h postcalving (CON, n=11), and (2) treatment group with first milking approximately 1d before calving and second milking at 4h after parturition (APM, n=12). Colostrum yields were recorded and proportional samples were analyzed for immunoglobulin G (IgG) concentration. Blood plasma samples for the analyses of P4 and PRL were collected 3 times daily at 8-h intervals for 4d prepartum and again taken at 4h after parturition. Total colostrum mass of APM cows was higher than that of CON cows. Immunoglobulin G concentration and protein content did not differ between antepartum milking in APM cows and postpartum milking in CON cows. Colostrum IgG concentration and protein content in APM cows at the postpartum milking were lower compared with the IgG concentration established at the prepartum (APM) and postpartum milkings of CON cows. Immunoglobulin G mass did not differ in first and second colostrum collection in APM cows but was lower compared with that of CON cows. The sum of IgG mass in APM cows (prepartum + postpartum collections) did not differ from that of CON cows. Lactose and fat in milk (concentration and mass) increased from first to second milking in APM cows. Total mass of lactose and fat in APM cows (prepartum + postpartum collections) was greater compared with that of CON cows. The finding that the time of milking relative to parturition, P4 decrease, and PRL peak slightly affected yield and quality of colostrum emphasizes the complex interactions of numerous endocrine and morphological changes occurring during colostrogenesis and lactogenesis in dairy cows. The considerably rapid transfer of immunoglobulins into colostrum of prepartum-milked cows within a few hours leads to the hypothesis that the transfer of IgG can be very fast and-contrary to earlier findings-persist at least until parturition.

Milk production during the colostral period is not related to the later lactational performance in dairy cows.

In dairy cows, milk yield increases rapidly after parturition until a peak at around wk 6 of lactation. However, the description of the shape of the lactation curve is commonly based on weekly average milk yields. For a more detailed analysis of the milk production curve from the very beginning of lactation including the colostral period and the effect of colostrum yield on further lactational performance, the first 10 milkings after parturition, daily milk yields from d 1 to 28 of lactation, and the cumulative milk production on d 100 to 305 of lactation were investigated in 17 primiparous and 39 multiparous cows milked twice daily. Milk yield at the first milking after parturition (colostrum) ranged from 1.3 to 20.7kg (Δ=19.4kg) in multiparous and from 1.8 to 10.9kg in primiparous animals (Δ=9.1kg). At the tenth milking, milk production ranged from 9.2 to 21.5kg (Δ=12.3kg) in multiparous and from 7.0 to 15.2kg (Δ=8.2kg) in primiparous animals. Immediately after parturition, daily milk production increased rapidly, but after approximately 1wk in lactation, the slope of the daily milk production curve flattened and continued more linear. A nonlinear regression equation was used to determine this timely change, which occurred earlier in primiparous (d 6.9±0.3) than in multiparous cows (d 8.2±0.2). The correlation between the amount of first colostrum and milk production during further lactation decreased already from 0.47 on d 5 to 0.32 on d 14. In multiparous cows, the correlation between total milk production of the previous 305d standard lactation and the amount of first colostrum was not significant (correlation=0.29), whereas the correlation with the daily production increased from 0.45 on d 5 to 0.69 on d 14. However, in primiparous animals, correlations between first-colostrum yield and daily milk yields up to d 28 of lactation were not significant, possibly due to the smaller sample size compared with multiparous animals. First-colostrum yield and cumulative milk production of 100, 200, and 305 lactation days were not significantly correlated in multiparous and primiparous cows. In conclusion, the milk production during the first few milkings is widely independent from the overall production level of a cow. Potentially, genetic selection toward lower milk yield during the very first days after parturition at a simultaneously high lactational performance may be a tool to ensure sufficient colostrum quality and to reduce the metabolic load around parturition.