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Due to anatomical characteristics of ungulate placenta types, immunoglobulins (IG) cannot be transferred via the placenta from the maternal to the fetal circulation during pregnancy. Therefore, passive immunization of the newborn ungulate immediately after birth is crucial for its survival. Colostrum, the first milk produced contains immunoglobulins (IG) as well as greater concentrations of several nutrients and bioactive components to provide specific immunity for the first weeks of life as well as an activation of the digestive tract and metabolism through colostral hormones, growth factors, vitamins, and special nutrients such as oligosaccharides. The uptake of colostrum by newborn calves, piglets, or foals within the first few hours after birth requires the availability of colostrum in a sufficiently liquid form. The formation of precolostrum starts days or even weeks before parturition, which allows concentrations of IG and other factors far beyond the concentrations in maternal blood circulation. Pre-colostrum components are partially secreted into the alveolar lumen and partially stored in the lactocytes of the mammary gland. These secretions are characterized by increased viscosity and density, which are difficult to harvest by the newborn. Through lactogenesis the secretion of milk components such as lactose is initiated, which causes a considerable water influx into the mammary secretion through an osmotic gradient between maternal blood and mammary secretion. The typical high concentrations of gestagens, mostly progesterone, inhibit the initiation of lactogenesis during pregnancy. A declining gestagen activity is the key signal to initiate a lactogenic prolactin increase and hence milk secretion. Mechanisms and timing of gestagen withdrawal differ considerably among mammalian species. Most species initiate both parturition and lactation through luteolysis (cattle, goat, pig, cat, dog, rabbit, mouse rat). In some species the placenta takes over the main portion of gestagen production (human, sheep, horse). In human, IG are transferred to the fetus during pregnancy, and the start of colostrum secretion only several days after parturition is no problem. In sheep and horses, gestagen secretion during late pregnancy is provided by the placenta. Both of these species are ungulates, and a delayed start of lactogenesis would be critical for the survival of the newborn. Therefore, the placental steroid secretion is subject to characteristic changes in both species towards the end of pregnancy to allow a timely availability of colostrum immediately after birth. At the end of pregnancy, the placenta of sheep produces estrogens at the expense of progesterone, and in horses the less potent dihydroprogesterone is produced instead of progesterone. A considerable variation in the resulting colostrum composition is likely due to the existing wide range of the interval between the commencement of lactogenesis and parturition or due to local regulatory effects at the level of individual glands. [ABSTRACT FROM AUTHOR]

The agricultural sector contributes to nitrogen (N) emissions since farm animals excrete considerable N amounts via feces and urine. To reduce N emissions by dairy cattle, methods predicting accurately individual N emissions are of great interest. Recent data showed that Brown Swiss (BS) cows have greater urea concentrations in milk and blood than Holstein (HO) cows. However, it is still unknown if greater BUN concentrations in a particular breed are congruently reflected by concomitantly increased contents of nitrogenous compounds in other media (e.g., urine and saliva). Thus, the present study simultaneously assessed biomarkers for kidney function like urea, and creatinine and symmetric dimethylarginine (SDMA) concentrations in several body fluids (i.e., blood, urine, milk, and saliva) as well as nitrogen excretion in feces in BS and HO cows under identical feeding conditions. Blood, saliva, urine, and feces were sampled in 31 multiparous BS and 46 HO cows kept under identical feeding and management conditions. Samples were collected at different lactational stages after the monthly DHIA control test-day. Concentrations of urea and creatinine were measured in serum, urine, and saliva. Symmetric dimethylarginine was determined in serum, which is an established indicator for glomerular filtration rate (GFR). Feces were analyzed for dry matter content and nitrogen concentrations. Data on milk urea and protein concentrations, and daily milk yield were obtained from the monthly DHIA test-day records. The effects of breed, time, and parity number on blood, saliva, urine, feces, and milk parameters were evaluated with the GLM procedure with breed, time, and parity number as fixed effects. Differences between BS and HO were assessed by the Tukey-corrected t-test at P < 0.05. Dry matter intake and body weight were similar in BS and HO cows (P > 0.05). No differences between BS and HO were observed for milk yield, fecal DM and nitrogen content. BS cows showed greater urea concentration (25.8 ± 0.7 vs 21.8 ± 0.7 mg/ dL), and protein content in milk (3.70 ± 0.08 vs 3.45 ± 0.07%) than HO cows (P < 0.01). Concentrations of urea, creatinine, and SDMA in serum, were greater in BS than in HO cows (P < 0.01) with 5.46 ± 0.19 vs 4.72 ± 0.13 mmol/L for urea, 105.96 ± 2.23 vs 93.07 ± 1.50 mmol/l creatinine, and 16.78 ± 0.69 vs 13.39 ± 0.44 μg/dL SDMA, respectively. Urea and creatinine concentrations in urine and saliva did not differ among breeds. Despite greater urea and creatinine concentrations in blood, and milk urea content in BS compared with HO, excretion of these parameters did not differ between breeds in urine. Our results suggest a reduced renal glomerular filtration rate in BS compared with HO. The underlying mechanisms require further investigations. [ABSTRACT FROM AUTHOR]

The disaccharide lactose represents the major carbohydrate source in milk-fed calves. Considering the complex and energy demanding processes of lactose synthesis in the mammary gland, the question arises why lactose is highly conserved as milk carbohydrate in evolution. In newborn and growing calves, lactose is enzymatically cleaved in the small intestine by lactase into its absorbable monosaccharides glucose and galactose. We investigated which effects different carbohydrate sources in milk exerted on metabolism of pre-weaned calves. Male and female calves [n = 44, age: 19.0 ± 0.3 d, body weight (BW): 53.7 ± 1.0 kg] were assigned to 6 different experimental diets (4 kg per meal, 2 meals/d) fed for 3 consecutive days. Experimental diets were formulated to achieve a composition similar to whole milk (WM; 4% fat, 3.4% protein, 4.7% lactose) by adding different carbohydrate sources to a milk replacer (based on a reconstituted protein extract with added milk fat): lactose (LAC), glucose (GLU), galactose (GAL), glucose + galactose (G/G), and xylose (XYL). Blood samples were taken from a jugular vein on the last day of treatments, right before feeding in the morning (T1), 2 (T2) and 7 (T3) hours later. Concentrations of glucose, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), triglycerides (TG), insulin, and glucagon were determined in plasma. Data were evaluated using a mixed model (SAS, version 9.4) with treatment, timepoint of sampling, and treatment x time interaction as fixed effects and the individual calf as repeated subject. Plasma glucose concentration increased after feeding from T1 to T2 in WM and GLU (P < 0.05), but not in calves fed LAC, GAL, G/G, and XYL. In WM, glucose concentrations reached basal values at T3, whereas no changes were observed in the other groups. NEFA concentrations were increased by trend in GAL at T2 (P = 0.06). Plasma BHB concentrations increased (P < 0.05) in all groups except WM from T1 to T2. Blood TG concentrations were increased in all groups except WM at T2 compared with T1 (GLU, GAL, XYL: P < 0.05; LAC: P = 0.08; G/G: P = 0.09). Whereas insulin concentrations increased after feeding from T1 to T2 (WM, G/G: P < 0.05; GLU: P = 0.09), glucagon concentrations were greater at T2 (XYL: P < 0.05; GLU: P = 0.08) and T3 (GLU, G/G, XYL, GAL: P < 0.05; LAC: P = 0.06) compared with T1. In conclusion, we observed different metabolic and endocrine responses to feeding of milk replacers differing in their carbohydrate composition. Although gross nutrient composition of the experimental diets was similar, digestion, absorption, and post-absorptive metabolization seem to differ between the carbohydrate supplements. In calves receiving XYL, a more catabolic status could be shown as XYL is absorbed, but cannot be used in intermediary metabolism. [ABSTRACT FROM AUTHOR]

Keywords: colostrum; FcRn; lactoferrin; mammary; regulation EN colostrum FcRn lactoferrin mammary regulation 37 43 7 06/20/23 20230601 NES 230601 Implications Colostrum formation is directed by placental structure and hormone signals Quality colostrum is defined by the concentration of immunoglobulin Quality colostrum formation in ungulates (hoofed mammals) is dependent on the Fc receptor of the neonate (FcRn) While the FcRn binds IgG1, IgG2, and albumin, only IgG1 is transported to colostrum FcRn IgG release into colostrum is pH dependent and lactoferrin likely facilitates it release Introduction Members of the class mammalia are so named for their mammary glands. Another example of this variation is that ungulate species form colostrum with IgG in a period of 3-4 weeks before birth ending shortly after partum, while the rodent species continue colostrum production over the entire suckling period (21 d) with an IgA emphasis that gradually transitions to mature milk. Immunoglobulins present in cow colostrum include G, M, and A, but it is IgG subclass 1 (IgG1) that constitutes 65-80% of immunoglobulin in cow colostrum (Table 1). Thus, milk secretion and hence dilution of the pre-colostrum secretion starts at this time and provides liquid colostrum at first milking ([14]). [Extracted from the article]

Milk production in dairy cows increases worldwide since many decades. With rising milk yields, however, potential limiting factors are increasingly discussed. Particularly, the availability of glucose and amino acids is crucial to maintain milk production as well as animal health. Limitations arise from feed sources, the rumen and digestive tract, tissue mobilization, intermediary metabolism and transport, and the uptake of circulating nutrients by the lactating mammary gland. The limiting character can change depending on the stage of lactation. Although physiological boundaries are prevalent throughout the gestation–lactation cycle, limitations are aggravated during the early lactation period when high milk production is accompanied by low feed intake and high mobilization of body reserves. The knowledge about physiological constraints may help to improve animal health and make milk production more sustainably. The scope of this review is to address contemporary factors related to production limits in dairy cows from a physiological perspective. Besides acknowledged physiological constraints, selected environmental and management-related factors affecting animal performance and physiology will be discussed. Potential solutions and strategies to overcome or to alleviate these constraints can only be presented briefly. Instead, they are thought to address existing shortcomings and to identify possibilities for optimization. Despite a scientific-based view on physiological limits, we should keep in mind that only healthy animals could use their genetic capacity and produce high amounts of milk. [ABSTRACT FROM AUTHOR]

Subclinical ketosis (SCK) and periparturient diseases considerably account for economic and welfare losses in dairy cows. The majority of scientific reports investigating the prevalence of SCK and production diseases are based on empirical studies conducted in Western Europe and North America. The present study surveyed the prevalence of SCK and production-related clinical diseases in early lactating cows in various countries across the world other than those in North America and Western Europe. Twelve countries of South and Central America (Argentina, Brazil, Chile, Colombia, Mexico), Africa (South Africa), Asia (Thailand, China), Eastern Europe (Russia, Ukraine), Australia, and New Zealand were assessed, and data from a total of 8,902 cows kept at 541 commercial dairy farms were obtained. A minimum of five cows per farm were blood sampled and examined once after parturition up to day 21 of lactation. Blood concentration of β-hydroxybutyrate was measured (threshold for SCK: 1.2 mmol/L), and the presence of production-related diseases such as milk fever, retained placenta, mastitis, metritis, displaced abomasum, lameness, and clinical ketosis was recorded. More than 95% of all cows were examined in their second week of lactation. Across all investigated countries, the SCK prevalence was 24.1%, ranging from 8.3% up to 40.1%. The prevalence of production-related diseases detected during the first 21 d of lactation was relatively low (<5%). Calculated odds ratios did not indicate an elevated risk for production diseases in cows with SCK. Despite differences in production systems across countries and variation between individual farms within a region, the present study data on SCK prevalence align with observations in Western European and North American dairy herds. At the very early stage of sampling and clinical examination for detection of SCK, it cannot be excluded that certain production diseases such as displaced abomasum, lameness, and mastitis have developed later. [ABSTRACT FROM AUTHOR]

Oxytocin (OT) can affect the blood-milkbarrier integrity by modulating the closure of tight junctions. Earlier research demonstrated a transfer of circulating immunoglobulins (Ig) into milk upon OT application during an LPS-induced mastitis. The role of OT in colostrogenesis, i.e., IgG transfer into colostrum, is not fully understood. Our study aimed at retarding the postpartum closure of the blood-milk-barrier and concomitantly prolonging the transfer of IgG into colostrum of dairy cows by a supraphysiological OT injection. Multiparous Holstein cows (n = 28) were enrolled. Blood and milk samples were collected at the first 2 milkings after parturition and milk yields were recorded. Ten cows received 50 IU OT i.v. at 30 min after the first milking (OT+30), 9 cows were injected 50 IU OT i.v. at 120 min before the second milking (OT-120), and 9 cows remained untreated (CTRL). Cows were milked at 6.7 ± 0.7 h after parturition (first milking) and 11.5 ± 0.3 h later (second milking). Milk was analyzed for fat, protein, lactose and IgG, serum albumin (SA), and electrolytes (Na, K, Cl) concentrations and for lactate dehydrogenase (LDH) activity. Concentration of α-lactalbumin (α-LA) was measured in blood plasma. Data were evaluated using a mixed model (SAS) with group, milking number, and group x milking number as fixed effects, and cow as random subject. In all groups, concentrations of protein, IgG, SA, LDH in milk decreased from first to second milking, while lactose content in milk increased (P < 0.05). Milk yield and milk fat content did not differ between first and second milking (P > 0.05). Concentration of α-LA in plasma tended to decrease from first to second milking. Treatments did not affect changes in blood and milk from first to second milking. In conclusion, a single injection of supraphysiological OT either at 30 min after the first milking postpartum or 2 h before the second milking postpartum did not retard the closure of the blood-milk-barrier in dairy cows. Furthermore, OT application did not prolong the active transport of IgG into milk after the first milking. [ABSTRACT FROM AUTHOR]

The present study investigated over 9 months the changes of fermentative quality of total mixed rations (TMR) containing grass silage (GS) as a major component, associated with changes in the volatile basic nitrogen (VBN) levels in an experimental dairy farm. Effects of VBN levels in TMR on metabolic parameters, reactive oxygen species (ROS) production by blood polymorphonuclear leukocytes (PMNs) and conception rates for dairy cows were analyzed. According to VBN levels in TMR during survey periods, three distinct phases were identified; phase A with low VBN; phase B with high VBN; and phase C with mid-VBN. Metabolic parameters in blood were all within normal range. However, during phases B and C, nitrogen metabolic indices such as blood urea nitrogen and milk urea nitrogen showed higher levels compared to those in phase A, and a simultaneous increase in ROS production by blood PMNs and the load on hepatic function in metabolic parameters was observed in the cows with a lower conception rate. This suggests that feeding TMR with elevated VBN levels due to poor fermented GS results in stimulation of ROS production by PMNs by ammonia, and negatively affects metabolism and reproductive performance in lactating dairy cow. [ABSTRACT FROM AUTHOR]