Hamada M.,Leibniz Institute for Farm Animal Biology |
Hamada M.,Sadat City University |
Albrecht E.,Leibniz Institute for Farm Animal Biology |
El Bagory A.-R.,Sadat City University |
And 4 more authors.
The presented study investigated changes of fat cell and muscle fibre size, and muscle fibre type composition around first parturition in cows with a combined beef and dairy genetic background. In contrast to high-merit dairy cows, these cows can serve as a model for beef cows because of the very low milk production level. Fifty heifers used in this experiment were F2 offspring originating from mating Charolais bulls to German Holstein cows and a following intercross of F1 individuals. They were assigned to 3 groups according to their lactation performance, namely high lactating (HL), low lactating long (LLL; duration of first lactation at least 100 days), and low lactation short (LLS; duration of first lactation shorter than 100 days). Biopsy samples were taken from semitendinosus muscle (MST) and subcutaneous fat (SCF) at three time points, 10 days before first parturition, 30 and 100 days after calving. These samples were investigated by histology and computer image analysis for muscle fibre profile, as well as intramuscular and subcutaneous fat cell size to estimate the impact of lactation on body reserves. Most cows continued growth and gained weight during lactation. Continuous tissue accretion was indicated on the cellular level by an increase in intramuscular fat cell size. Subcutaneous fat cells were larger in low lactating cows with a short lactation period. There were no morphological signs of fat mobilization from fat cells. There was also no protein mobilization indicated by changes in muscle fibre size. However, the increase in percentage of fast, glycolytic muscle fibres indicated alterations in muscle metabolism during transition from late pregnancy to early lactation. Cows remained obviously in a positive energy balance in this study and continued tissue accretion during lactation. This was reflected on the cellular level in skeletal muscle and subcutaneous fat. © 2015 Elsevier B.V. Source
Schaff C.T.,Institute of Nutritional Physiology Oskar Kellner |
Rohrbeck D.,Institute of Nutritional Physiology Oskar Kellner |
Steinhoff-Wagner J.,Institute of Nutritional Physiology Oskar Kellner |
Kanitz E.,Leibniz Institute for Farm Animal Biology |
And 3 more authors.
Journal of Dairy Science
Catecholamines and glucocorticoids are involved in fetal maturation of organ systems to prepare the fetus for extrauterine life. Calves, especially when born preterm, depend on function of the adrenergic system and the glucocorticoid axis to adapt energy metabolism for the neonatal period. We tested the hypothesis that hepatic glucocorticoid and α1- and β2-adrenergic receptors in neonatal calves are involved in adaptation of energy metabolism around birth and that respective binding capacities depend on stage of maturation during the neonatal period. Calves (n=7 per group) were delivered by section preterm (PT, 9d before term) or were born at term (full-term, FT; spontaneous vaginal delivery), or spontaneously born and fed colostrum for 4d (FTC). Blood samples were taken immediately after birth and before and 2h after feeding at 24h after birth (PT, FT) or on d 4 of life (FTC) to determine metabolic and endocrine changes. After slaughter at 26h after birth (PT, FT) or on d 4 of life (FTC), liver tissue was obtained to measure hepatic binding capacity of glucocorticoid and α1- and β2-adrenergic receptors. Maximal binding capacity and binding affinity were calculated by saturation binding assays using [3H]-prazosin and [3H]-CGP-12177 for determination of α1- and β2-adrenergic receptors, respectively, and [3H]-dexamethasone for determination of glucocorticoid receptor in liver. Additional liver samples were taken to measure mRNA abundance of glucocorticoid and α1- and β2-adrenergic receptors, of key enzymes and factors related to hepatic lipid metabolism, and of insulin-like growth factor 1 (IGF1). Plasma concentrations of β-hydroxybutyrate and leptin changed with time, and leptin concentrations were affected by stage of maturation. The binding capacities for hepatic glucocorticoid and β2-adrenergic receptors as well as gene expression of IGF1 were greater in FTC than in FT and PT, and binding affinity for β2-adrenergic receptor was lowest in PT. The binding capacity of hepatic α1-adrenergic receptor was greatest in FTC and greater in FT than in PT. The binding capacities of glucocorticoid and α1-adrenergic receptors were mainly related to variables of glucose and lipid metabolism. In conclusion, our results indicate dependence of hepatic glucocorticoid and adrenergic receptors on stage of maturation in neonatal calves and emphasize the association of α1-adrenergic receptor and glucocorticoid receptor with neonatal glucose and lipid metabolism. © 2015 American Dairy Science Association. Source