Effects of cortisol secreted via a 12-h infusion of adrenocorticotropic hormone on mineral homeostasis and bone metabolism in ovariectomized cows

Eucalcemia during lipopolysaccharide challenge in postpartum dairy cows: II. Calcium dynamics

Hypocalcemia induced by immune activation is a conserved response among mammals. Early postpartum cows will experience decreased circulating Ca concentrations following acute immune activation; however, the cause for decreased Ca concentration is unknown. Our objectives were to (1) describe Ca dynamics following an intravenous (IV) LPS challenge in early postpartum cows, and (2) compare inflammatory-induced changes in Ca dynamics between IV Ca-treated cows and control cows. Cows (n = 14, 8 ± 1 d in milk) were enrolled in a matched-pair randomized controlled design to receive IV Ca (IVCa) in a eucalcemic clamp for 12 h, or 0.9% NaCl (CTRL) following an IV LPS infusion (0.040 or 0.045 µg of LPS/kg of body weight over 1 h). During the 24 h following LPS infusion, circulating concentrations of parathyroid hormone and serotonin were measured, serum and urine samples were collected to calculate urinary fractional excretion of Ca (FECa), and fecal samples were collected to calculate Ca apparent digestibility (ADCa) using amylase-treated and ash-corrected undigested neutral detergent fiber after 240 h (uNDFom₂₄₀) as an internal marker. Changes in Ca intake and milk Ca secretion were also quantified and compared with baseline values. Cows were fasted during challenge and dry matter intake was 20 ± 5% less than baseline values on the day of challenge and did not differ between groups. On the day of challenge, milk Ca concentration increased, but milk yield decreased such that total Ca secreted in milk did not change from baseline. Urine FECa was low overall, but an interaction of treatment and time was identified such that FECa increased in IVCa but decreased in CTRL. Concentrations of parathyroid hormone increased and serotonin decreased following challenge. Fecal dry matter decreased from baseline, but did not differ between 6, 12, and 24 h, and did not differ between groups. An interaction of treatment and time was identified for ADCa and apparent digestibility of dry matter such that digestibility was decreased in CTRL but not IVCa at 6 h. Acute immune activation induced hypocalcemia in CTRL, and although urinary Ca excretion was not a primary cause, it is unclear to what degree hypocalcemia was due to altered ADCa. Eucalcemia appeared to alter adaptations in Ca homeostasis during immune activation as FECa was increased in IVCa animals.

Physiological, Immunological and Genetic Factors in the Resistance and Susceptibility to Gastrointestinal Nematodes of Sheep in the Peripartum Period: A Review

Parasitic diseases of sheep involving gastrointestinal nematodes (GIN) are one of the main problems that affect fl ock productivity, especially during the peripartum period. Around lambing, the ewes are immunosuppressed and the nematode faecal egg count (FEC) increases at four weeks before lambing, reaching a peak between the fourth and sixth week postpartum and subsequently decreasing towards weaning. Prolactin has been credited with a suppressive effect on immune system, along with other hormones that intervene in metabolism, such as leptin, which has an important role in the activation of other hormones. Cortisol has also been included; this is stimulated by any stressful event and inhibits the proliferation of T-cells and alters the function of immunoglobulins. Another related hormone is pepsinogen, which is considered a marker of the integrity of the abomasum mucosa, as well as the albumin concentration that increases in the presence of a GIN infection. The humoral and cellular immune response, as well as inflammatory reactions, are the main mechanisms of action against GIN. Lymphocytes direct the effector mechanisms in a Th2 cell response, including interleukins (IL-4, IL-5, IL-9, IL-10) and transforming growth factor beta (TGF-β) together with immunoglobulins (IgA, IgG, IgM and IgE), which prevent the invasion of pathogens. Eosinophils with a cytotoxic effect are indicators of a parasitic infection, with importance in the immune protection of infected individuals. The genetic selection of resistant individuals measured by FEC is dependent on the heritability (h²), which is moderately inheritable and highly repeatable. Effects that influence the resistance or susceptibility of sheep to GIN infections in the peripartum period are determined by the interaction of various factors, such as genotype or breed, nutrition, age, type of birth, season and production system, etc., which are studied in this review.

Stress-Induced Phosphaturia in Weaned Piglets

Simple Summary

The weaning period is a critical period in piglets’ lives. Multiple elements, including diet change, social stress, handling, and change of physical environment, contribute to enormous stress that has health implications. This period has been studied extensively in the past, but some gaps in our knowledge remain. We attempted to fill them by biochemical characterizations of the changes in blood and urine before and after the weaning. The major finding is the observation of the release of phosphate in the urine in the apparent absence of a factor other than weaning. This release is followed by the drop of the phosphate in the blood. Additionally, we observed a population-level Bohr effect, suggesting a decrease in oxygen levels in the tissues. These results point to the development of systemic hypophosphatemia, even though modern diets used in pig breeding have an excess of phosphorus typically. This study sheds new light on the weaning period and will help researchers and veterinary practices in improving design studies and treatments around that time.

Abstract

The weaning period in piglets draws significant attention from researchers, veterinarians, and breeders. A substantial change in diet accompanied by enormous stress has health and welfare implications (abnormal feeding intake, infections, umbilical lesions, etc.). While the parameters like optimal age or weight for the weaning have been studied extensively, relatively less attention has been devoted to the study of stress effects in the piglets’ biochemistry. As one of the effects of stress is hyperventilation, a gasometric analysis supported by measurements of hypoxia biomarkers was conducted. Piglets blood and urine, one day and seven days before and one day and seven days after the weaning, were tested. There was no evidence of hyperventilation, but phosphaturia and hypophosphatemia were observed one and seven days postweaning, respectively. A statistical analysis across the population also pointed to minor tissue hypoxia. Our work contributes to an understanding of biochemical dynamics and helps in the interpretation of physiological changes observed in piglets in this critical period.

Plasma calcium concentrations are decreased at least 9 hours before parturition in multiparous Holstein-Friesian cattle in a herd fed an acidogenic diet during late gestation

Calcium homeostatic mechanisms are challenged in periparturient multiparous dairy cattle due to the rapid transport of large amounts of calcium into the mammary gland associated with colostrogenesis, resulting in decreased plasma total calcium concentration ([Ca]). An unresolved issue is the timing of the decrease in plasma [Ca] relative to the time of parturition, with the consensus view being that plasma [Ca] does not decrease until after parturition. The objective of this study, therefore, was to characterize the change in plasma [Ca] over time in periparturient dairy cattle. Plasma and mid-stream urine samples were collected daily starting 3 d before calving from 104 periparturient Holstein-Friesian dairy cows in a herd fed an acidogenic total mixed ration during the late dry period. Mixed-models ANOVA and linear and multivariable regression analyses were conducted. Plasma [Ca] decreased in periparturient multiparous cattle (n = 70) but not in primiparous cattle (n = 34). Compared with mean values approximately 72 h before parturition ([Ca] = 2.32 mmol/L), mean plasma [Ca] in multiparous cattle first decreased at 9 h before parturition (2.13 mmol/L) and remained decreased for up to 48 h after parturition, with the lowest mean value (1.87 mmol/L) occurring at 28 h after parturition. Mean 24-h urine Ca excretion was calculated to decrease by 3.5 to 3.8 g in periparturient multiparous cattle. Regression analysis indicated that plasma [Ca] in the 12-h period before and 24-h period after parturition was strongly and negatively associated with age but was also negatively associated with milk production indices. We conclude that plasma [Ca] was decreased at least 9 h before parturition in multiparous dairy cattle fed an acidogenic diet in late gestation, and that calcium homeostasis was disrupted for 2 to 3 d around parturition.

Treatment of phosphorus balance disorders

Phosphorus (P) homeostasis in ruminants has received increased attention over the past decades. Although environmental concerns associated with excessive P excretion in cattle manure have led to incentives to lower dietary P intake, hypophosphatemia-particularly in the periparturient dairy cow-has been associated with conditions, such as the downer cow syndrome or postparturient hemoglobinuria. The objective of this article is to revisit current understanding of P homeostasis in ruminants, to discuss the pathophysiology and clinical presentation of P balance disorders, and to review different treatment approaches to correct imbalances of the body's P equilibrium.