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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.

It was recently shown that a teat that is not used in the first lactation will have a reduced development and milk yield in the second lactation. In the current study, the impact of imposing a suckling period of 2, 7, or 21 d during the first lactation on piglet performance, milk composition, endocrine status, and mammary gene expression of sows in their second lactation was studied. Pregnant Yorkshire gilts were divided into 3 groups according to lactation length: 1) 2-d lactation (2D; = 20), 2) 7-d lactation (7D; = 20), and 3) 21-d lactation (21D; = 21). After weaning, sows were bred and kept for a second parity. In both lactations, litters were standardized to 12 piglets with 12 functional teats and surplus teats were sealed. In the second lactation, piglets were weighed on d 2, 7, 14, 21 (weaning), 31, and 56 postpartum, and sow feed intake was recorded. On d 110 of gestation and on d 21 of lactation, mammary biopsies were performed on 10 sows per treatment to obtain parenchymal tissue samples for determination of mRNA abundance for , , , , , and genes. Milk samples and jugular blood samples were also obtained from sows on d 21 of lactation. Standard composition analyses (DM, fat, protein, and lactose) were done in milk. Concentrations of prolactin, IGF-1, glucose, and urea were measured in blood. There was a tendency for 21D sows to consume more feed than 2D or 7D sows during the first week of lactation (0.10). There was no treatment effect on BW of piglets at any time until d 56 (0.10). Concentrations of prolactin, IGF-1, urea, and glucose in sows on d 21 of lactation were not affected by treatment (0.10). Dry matter, fat, protein, and lactose contents in milk were not altered by treatment (0.10). On d 110 of gestation, gene expression was greater ( = 0.05) in 21D sows than in 7D sows. On d 21 of lactation, gene expression of was greater ( = 0.05) and that of tended to be lower (0.10) in 7D sows than in 2D sows. The mRNA abundance of also tended to be lower (0.10) in 2D sows than in 7D sows. Results indicate that increasing the duration of lactation from 2 d to 7 d or to 21 d in first-parity sows did not improve growth rate of their piglets in the subsequent lactation. This suggests that suckling of a teat for 2 d during the first lactation is sufficient to ensure optimal mammary development.

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 ( = 0.75,0.0001) between saliva and blood cortisol concentrations was observed with increased (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 ( = 0.03, = 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.

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 (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 (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 (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 (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.

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]; P0.05), 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 (P0.05). 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 (P0.05). This finding emphasizes the regulatory role of the current metabolic status on the cortisol release during inflammation.

To ultrasonographically investigate the effect of administration of exogenous progesterone using a progesterone-releasing intravaginal device (PRID), with or without the addition of equine chorionic gonadotropin (eCG), to cows with cystic ovarian disease (COD) in the first month postpartum.Thirty-three dairy cows (n = 11/group) diagnosed with COD between day 20 and 30 postpartum were randomly assigned to treatment groups (TG) PRID/PGF and PRID/PGF+eCG or a control group (CG). The CG remained untreated during the 20-day study period, which started on the day the diagnosis was made (day 0). Cows of group PRID/PGF received a PRID, which was removed on day 10, at which time PGF2α was given intravenously. Cows of the PRID/PGF+eCG group additionally received eCG on day 7 intravenously. Ovarian ultrasonography and blood sampling for measurement of plasma progesterone (P4) and estradiol-17β (E2) were done on days 0, 7, 10, 13, and 20 in the TG and on days 0, 10, and 20 in the CG.On day 0, all cows had follicular cysts, six of which developed into luteal cysts in the CG. The mean cyst diameter remained unchanged in the CG and decreased in the TG by day 20 (p 0.01). All treated cows ovulated and formed at least one corpus luteum (CL) after PRID removal, but only two control cows ovulated (p 0.05). Of 12 ovulatory follicles in the TG dominant on day 7, eight formed a CL with a cavity, whereas of 10 ovulatory follicles in the same groups, dominant on day 10, only one formed a CL with a cavity (p 0.05). The diameters of follicles, that formed a CL with a cavity, were larger on day 10 (p 0.01). Mean P4 concentrations on day 0 were ≤ 1 ng/ml in all groups. P4 concentration increased during treatment and decreased below 1 ng/ml after PRID removal (p 0.05).Treatment with PRID alone led to resolution of COD in all cows and therefore the additional benefit of eCG could not be critically assessed. CL with a cavity more often originate from larger and older dominant ovulatory follicles.