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Because of the decreasing use of antimicrobial drugs in animal food production, new treatments of infectious diseases such as mastitis are needed. This includes strategies to optimize the function of the animal's immune system. The present review discusses the components of the mammary immune response and the involvement of the blood-milk barrier during infections with different bacteria, strategies to manipulate the blood-milk barrier, and the potential to increase the efficiency of the animal's immune response. The mammary immune response is widely based on the cellular components of the innate immune system, which can be detected as an increase of the somatic cell count (SCC). During infection with Gram-negative bacteria such as Escherichia coli, characterized by severe clinical symptoms, there is a considerable transfer of soluble blood components including immunoglobulins from blood into milk. This is not typically observed during intramammary infection with Gram-positive bacteria such as Staphylococcus aureus, which is typically observed as a chronic subclinical infection. We have simulated these different types of mastitis by administering cell wall components of these bacteria (i.e., lipopolysaccharide [LPS] from E. coli and lipoteichoic acid [LTA] from S. aureus). Dosages of these 2 components intramammarily administered were adjusted to induce a comparable increase in SCC. Treatment with LPS caused a comprehensive transfer of blood components including immunoglobulins into milk, whereas in the LTA-induced mastitis, only a small increase of blood components in milk occurred. The blood-milk barrier can be manipulated. Glucocorticoids such as prednisolone reduced the transfer of blood components from blood into milk while reducing the general inflammatory reaction. It is possible that this treatment also inhibits the transfer of immunoglobulins into milk, likely reducing the efficiency of the immune response. In contrast, an opening of the blood-milk barrier could be achieved by an extremely high dosage of oxytocin (e.g., 100 IU). We assume that the myoepithelial hypercontraction increases the epithelial permeability that allows an increased flux of blood components including immunoglobulins into milk. The potential for manipulating the blood-milk barrier permeability as a treatment for mastitis is possible if specific antibodies against pathogens can be efficiently transported to the infected mammary gland. [ABSTRACT FROM AUTHOR]

In dairy cows, hypocalcemia is caused by the sudden calcium demand by the mammary gland at the onset of lactation. Calcitriol (1,25-dihydroxy vitamin D; 1,25-VitD) increases the intestinal calcium absorption and the renal calcium reabsorption. Daylight contributes to the formation of 1,25-VitD, as it transforms 7-dehydrocholesterol into cholecalciferol, a 1,25-VitD precursor. Calving pens are usually set in quiet places where cows can stay calm and relaxed before parturition. However, those pens often have poor lighting conditions and therefore cows may become vitamin D deficient because of inadequate daylight exposure. Therefore, we have tested the hypothesis that direct daylight exposure supports the synthesis of 1,25-VitD and consequently attenuates the decline of calcium concentrations at parturition. Twenty Holstein dairy cows were randomly assigned to 2 experimental groups (daylight group, DL; and control group). Beginning on d -10 before expected parturition, both groups were placed in a standard indoor calving pen from 1700 h to 800 h. From 800 h to 1700 h cows from the DL group were moved into a contiguous open pen with direct access to daylight whereas controls remained at the standard indoor calving pen. After parturition both groups were permanently placed in an indoor calving pen until the end of the experimental period (d 30 postpartum). Blood samples were collected daily from d -10 prior to expected parturition through d 7 postpartum with an additional sample on d 30 postpartum. Milk yield was recorded at each milking during the whole experimental period. In the DL group, 25-hydroxyvitamin D (25-VitD), 1,25-VitD and total calcium concentrations around parturition were higher than in the controls. Higher parathyroid hormone concentrations were observed in the control group compared to the DL group at parturition. Pyridinoline concentrations did not differ between groups on d 1, and therefore it is assumed that the intensity of calcium transfer from the bones to the bloodstream was not affected by the increased daylight exposure. The measured plasma metabolites (β-hydroxybutyrate, fatty acids and glucose) as well as milk yield were not affected by the increased daylight exposure. In conclusion, the increased daylight exposure before parturition increased 25-VitD and 1,25-VitD concentrations, preventing a considerable decline of total calcium concentrations around parturition. [ABSTRACT FROM AUTHOR]

One of the most prominent physiological responses to stressors is the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis, currently assessed by measuring cortisol concentration in blood plasma. To reduce animal discomfort during sampling, which negatively affects stress biomarkers, current research focuses on noninvasive sampling of media other than blood, for example, saliva. The aim of this study was to assess the suitability of saliva cortisol as a biomarker under different physiological and immunological states in dairy cows. Our objectives were to 1) evaluate the relationship between HPA axis activation and saliva cortisol concentration, 2) investigate effects of some feeding action (as influenced by feed and water consumption) on saliva cortisol concentration, and 3) evaluate the time lag between plasma and saliva cortisol during induced inflammatory conditions by intramammary lipopolysaccharide (LPS) and lipoteichoic acid (LTA) injection. During a specific activation of the HPA axis, a positive correlation (r = 0.75, P < 0.0001) between saliva and blood cortisol concentrations was observed with increased (P < 0.01) plasma cortisol concentrations following ACTH administration. Saliva and blood samples were taken before, during, and after drinking, feeding, and ruminating. Only a low correlation between saliva and plasma cortisol concentrations (r = 0.03, P = 0.83) but no significant effects of the different feeding actions on saliva cortisol were observed. When compared with basal concentrations, cortisol concentrations in plasma significantly increased during inflammatory responses following LPS and LTA injection. Compared with plasma cortisol, changes in saliva cortisol concentrations occurred at a much lower level within a narrow range and did not necessarily follow changes in plasma. In conclusion, the positive correlation between saliva and plasma cortisol concentration in response to ACTH and inflammation suggests the suitability of saliva cortisol measurement for the HPA axis activation assessment. However, changes in saliva cortisol concentration occur within a very narrow range. Furthermore, not only must variation among individual animals be considered but also variation within the same animal. Only with additional knowledge of the concomitant physiological status of the cow it is possible to correctly evaluate saliva and blood cortisol samples. [ABSTRACT FROM AUTHOR]

Colostrum IgG concentration and yield vary tremendously among farms and cows and among quarters within cows. The present study quantified changes in quarter colostrum characteristics up to 3 successive lactations. First colostrum was quarter collected within 4 h after parturition in the first 2 consecutive lactations from 12 cows, and colostrum was obtained from 14 multiparous dairy cows in 2 consecutive lactations and 8 cows thereof in 3 consecutive lactations. Colostrum yield per quarter showed a high variation in both primiparous and multiparous dairy cows during consecutive lactations. Percentage distribution of colostrum yield among quarters within cows was similar from parity to parity. The differences in colostrum yield within the same quarter were higher in cows from the first to the second lactation compared with the differences within quarters of multiparous cows in consecutive lactations (P < 0.05). The intraclass correlation coefficient (ICC) for quarter colostrum yield was found to be similar in cows from the first to the second parity (ICC = 0.42) and within consecutive lactations of multiparous cows (ICC = 0.44). Whereas the position of the quarter did not influence colostrum yield in cows from the first to the second lactation, quarter colostrum yield in multiparous cows was higher in rear quarters than in front quarters (P < 0.05) with fewer changes in successive lactations. Concentration and mass of IgG in quarter-milked colostrum distinctly varied among quarters and cows in both primiparous and multiparous cows. In multiparous cows, higher values for quarter concentration and mass of IgG were observed when compared with primiparous cows, in particular in the rear quarters (P < 0.05). Relative differences of IgG concentration and mass within quarters were higher in consecutive lactations of multiparous cows compared with differences within quarters of cows in the first 2 lactations (P < 0.05). The ICC of colostral IgG concentration and mass within quarters of cows from the first to the second lactation was 0.52 and 0.67, respectively, and lower compared with the ICC of IgG concentration and mass within quarters during consecutive lactations of multiparous cows. In conclusion, IgG concentration and mass were shown to be more repeatable within quarters of multiparous dairy cows compared with the first 2 lactations of dairy cows. Contrarily, colostrum yield within quarters in consecutive lactations had only a moderate repeatability and seemed to be affected by factors other than genetics. [ABSTRACT FROM AUTHOR]

During the last months, the number of reports on Holstein calves suffering from incurable idiopathic diarrhea dramatically increased. Affected calves showed severe hypocholesterolemia and mostly died within days up to a few months after birth. This new autosomal monogenic recessive inherited fat metabolism disorder, termed cholesterol deficiency (CD), is caused by a loss of function mutation of the bovine APOB gene. The objective of the present study was to investigate specific components of lipid metabolism in 6 homozygous for the APOB mutation (CDS) and 6 normal Holstein calves with different APOB genotypes. Independent of sex, CDS had significantly lower plasma concentrations of total cholesterol (TC), free cholesterol (FC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very-lowdensity lipoprotein cholesterol (VLDL-C), triacylglycerides (TAG), and phospholipids (PL) compared with homozygous wild-type calves (P < 0.05). Furthermore, we studied the effect of the APOB genotype on cholesterol metabolism in adult Holstein breeding bulls of Swissgenetics. Among a total of 254 adult males, the homozygous mutant genotype was absent, 36 bulls were heterozygous carriers (CDC), and 218 bulls were homozygous wild-type (CDF). In CDC bulls, plasma concentrations of TC, FC, HDL-C, LDL-C, VLDL-C, TAG, and PL were lower compared with CDF bulls (P < 0.05). The ratios of FC:cholesteryl esters (CE) and FC:TC were higher in CDC bulls compared with CDF bulls, whereas the ratio of CE:TC was lower in CDC bulls compared with CDF bulls (P < 0.01). In conclusion, the CD-associated APOB mutation was shown to affect lipid metabolism in affected Holstein calves and adult breeding bulls. Besides cholesterol, the concentrations of PL, TAG, and lipoproteins also were distinctly reduced in homozygous and heterozygous carriers of the APOB mutation. Beyond malabsorption of dietary lipids, deleterious effects of apolipoprotein B deficiency on hepatic lipid metabolism, steroid biosynthesis, and cell membrane function can be expected, which may result in unspecific symptoms of reduced fertility, growth, and health. [ABSTRACT FROM AUTHOR]

Cortisol in dairy cows is released in an episodic manner underlying a circadian rhythm. The involvement of cortisol in numerous adaptive processes to cope with adverse conditions such as pain and inflammation is well characterized. Recent studies described contradictory effects of nutrition and metabolism on the secretory pattern of cortisol. However, up to now, the direct effects of single metabolites during various metabolic conditions without the profound endocrine changes around parturition on the glucocorticoid secretion in dairy cows have not been described. The objective of this study was to investigate the effects of long-term (56-h) manipulated metabolic states, that is, manipulated plasma concentrations of glucose and β-hydroxybutyrate (BHBA), on the release of cortisol in midlactation dairy cows. Besides the concentration of cortisol at defined time points, its pulsatile secretory pattern was studied in combination with an acute immune challenge through an intramammary lipopolysaccharide (LPS) challenge. Twenty-five midlactation dairy cows were randomly assigned to 1 of 4 treatments (hyperinsulinemic hypoglycemic clamp [HypoG], hyperinsulinemic-euglycemic clamp [EuG], continuous infusion of BHBA [HyperB], or infusion of saline solution for the control group [Control). Different metabolic states induced by infusion treatments affected the characteristics of cortisol secretion (elevation of baseline [the HypoG and HyperB treatments] and decreased peak length [the HypoG treatment]; P < 0.05), whereas amplitude, peak interval, height, peak area, area under the curve (AUC) above the baseline cortisol concentration (AUCb), and the total AUC (AUCt) were not different between infusion treatments. The induced inflammatory response due to the intramammary LPS challenge at simultaneously maintained infusion treatments diminished the pulsatile nature of cortisol release, whereas AUCb (and AUCt, respectively) was lowest for the HypoG treatment compared with the HyperB and Control treatments (P < 0.05). This study indicates that single metabolites (glucose and BHBA) and their availability or turnover (in case of glucose) have a different impact on the regulation of cortisol secretion resulting in changes of its pulsatile release. Furthermore, cortisol release during intramammary inflammation was found to be greater in the HyperB, EuG, and Control treatments compared with the HypoG treatment (P < 0.05). This finding emphasizes the regulatory role of the current metabolic status on the cortisol release during inflammation. [ABSTRACT FROM AUTHOR]

Provision of additional floor heating (33 to 34°C) at birth and during the early postnatal hours is favorable for newborn piglets of domestic sows (Sus scrofa). We investigated whether this relatively high temperature influenced sow behavior and physiology around farrowing. One-half of 28 second-parity pregnant sows were randomly chosen to be exposed to floor heating 12 h after onset of nest building and until 48 h after birth of the first piglet (heat treatment), whereas the rest of the sows entered the control group (control treatment) with no floor heating. Hourly blood sampling from 8 h before and until 24 h after the birth of the first piglet was used for investigation of temporal changes in plasma concentrations of oxytocin, cortisol, and ACTH. In addition, occurrence and duration of sow postures were recorded -8 to +48 h relative to the birth of the first piglet. There was a clear temporal development in sow behavior and hormone concentrations (ACTH, cortisol, and oxytocin) across parturition (P < 0.001), independent of treatment. In general, hormone concentrations increased from the start to the end of farrowing. The observed oxytocin increase and peak late in farrowing coincided with the passive phase where sows lie laterally with an overall reduced activity. Floor heating increased the mean concentration of cortisol (P = 0.02; estimated as 29% greater than in controls) and tended to increase the mean concentration of ACTH (P = 0.08; estimated as 17% greater than in controls), but we did not find any treatment effect on mean oxytocin concentrations, the course of parturition, or the behavior of sows. Behavioral thermoregulation may, however, have lost some function for the sows because the floor was fully heated in our study. In addition, exposure to heat decreased the between-sow variation of plasma oxytocin (approximately 31% less relative to control) and ACTH (approximately 46% less relative to control). Whether this decreased variation may be indicative of acute stress or linked to other biological events is unclear. In conclusion, inescapable floor heating (around 33.5°C) may be considered a stressor for sows around farrowing, giving rise to elevated plasma concentrations of cortisol, but without concurrent changes in oxytocin or behavioral activity. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate individual metabolic and endocrine adaptation to lactation under conditions of identical housing and feeding conditions in high-yielding dairy cows. Forty-five cows were studied on a research farm under standardized but practical conditions. From wk 2 before calving until wk 14 postpartum, blood samples were collected at weekly intervals and assayed for blood chemistry and various metabolites and hormones. Body weight, BCS, and backfat thickness were also recorded weekly. Milk yield, milk composition, and feed intake and energy balance were accordingly measured during the postpartum phase. The animals were retrospectively classified according to their plasma concentration of 5-hydroxybutyrate (BHB): cows in which a BHB threshold of 1 mM was exceeded at least once during the experiment were classified as BHB positive (BHB+); cows with BHB values consistently below this threshold were classified as BHB negative (BHB-). Using this classification, differences for NEFA and glucose concentrations were observed, but the mean calculated energy balance did not differ between the groups during the experimental period (-22.2 MJ of NE1/d ± 4.7 for BHB+ and -18.9 MJ of NE1/d + 4.9 for BHB-). In BHB+ cows, the peripartum decrease (P < 0.05) of BW, BCS, and backfat thickness was more pronounced than in BHB- cows. Mean milk yields did not differ between groups. However, BHB+ cows had greater milk fat and lesser milk protein contents (P < 0.05), resulting in a greater (P < 0.05) fat:protein ratio than in BHB-cows. Thus, to some extent, cows were able to compensate for the negative energy balance by adjustments in performance. Milk acetone concentrations followed BHB concentrations in blood. Insulin-like growth factor-I and leptin concentrations were greater (P < 0.05) in BHB-cows during the time of observation than in the BHB+ cows. Comparing the reproductive variables recorded (first increase of progesterone, first service conception rate, number of services per conception, interval from calving to first Al, interval from first Al to conception, and days open) between the 2 groups yielded no significant differences. Our findings imply that despite comparable energy balance, there is considerable individual variation of the adaptive ability of cows during early lactation based on a variety of metabolic and endocrine variables. [ABSTRACT FROM AUTHOR]