High ambient temperatures have severe adverse effects on biological functions of high-yielding dairy cows. The metabolic adaption to heat stress was examined in 14 German Holsteins transition cows assigned to two groups, one heat-stressed (HS) and one pair-fed (PF) at the level of HS. After 6 days of thermoneutrality and ad libitum feeding (P1), cows were challenged for 6 days (P2) by heat stress (temperature humidity index (THI) = 76) or thermoneutral pair-feeding in climatic chambers 3 weeks ante partum and again 3 weeks post-partum. On the sixth day of each period P1 or P2, oxidative metabolism was analyzed for 24 hours in open circuit respiration chambers. Water and feed intake, vital parameters and milk yield were recorded. Daily blood samples were analyzed for glucose, β-hydroxybutyric acid, non-esterified fatty acids, urea, creatinine, methyl histidine, adrenaline and noradrenaline. In general, heat stress caused marked effects on water homeorhesis with impairments of renal function and a strong adrenergic response accompanied with a prevalence of carbohydrate oxidation over fat catabolism. Heat-stressed cows extensively degraded tissue protein as reflected by the increase of plasma urea, creatinine and methyl histidine concentrations. However, the acute metabolic heat stress response in dry cows differed from early-lactating cows as the prepartal adipose tissue was not refractory to lipolytic, adrenergic stimuli, and the rate of amino acid oxidation was lower than in the postpartal stage. Together with the lower endogenous metabolic heat load, metabolic adaption in dry cows is indicative for a higher heat tolerance and the prioritization of the nutritional requirements of the fast-growing near-term fetus. These findings indicate that the development of future nutritional strategies for attenuating impairments of health and performance due to ambient heat requires the consideration of the physiological stage of dairy cows.

Climate changes lead to rising temperatures during summer periods and dramatic economic losses in dairy production. Modern high-yielding dairy cows experience severe metabolic stress during the transition period between late gestation and early lactation to meet the high energy and nutrient requirements of the fetus or the mammary gland, and additional thermal stress during this time has adverse implications on metabolism and welfare. The mechanisms enabling metabolic adaptation to heat apart from the decline in feed intake and milk yield are not fully elucidated yet. To distinguish between feed intake and heat stress related effects, German Holstein dairy cows were first kept at thermoneutral conditions at 15°C followed by exposure to heat-stressed (HS) at 28°C or pair-feeding (PF) at 15°C for 6 days; in late-pregnancy and again in early lactation. Liver and muscle biopsies and plasma samples were taken to assess major metabolic pathway regulation using real-time PCR and Western Blot. The results indicate that during heat stress, late pregnant cows activate Cahill but reduce Cori cycling, prevent increase in skeletal muscle fatty acid oxidation, and utilize increased amounts of pyruvate for gluconeogenesis, without altering ureagenesis despite reduced plane of nutrition. These homeorhetic adaptations are employed to reduce endogenous heat production while diverting amino acids to the growing fetus. Metabolic adaptation to heat stress in early lactation involves increased long-chain fatty acid degradation in muscle peroxisomes, allowance for muscle glucose utilization but diminished hepatic use of amino acid-derived pyruvate for gluconeogenesis and reduced peroxisomal fatty acid oxidation and ATP production in liver of HS compared to PF cows in early lactation. Consequently, metabolic adaptation to heat stress and reduced feed intake differ between late pregnancy and early lactation of dairy cows to maintain energy supply for fetus development or milk production simultaneously reducing endogenous heat production.

The videotaping and the WGTA are suitable methods to detect disease-related impairments in common marmosets, which is essential for the refinement of experiments.

While mammary tumours are the main reasons of death in bitches, early detection of tumours and metastases is crucial for survival of affected dogs. Invasiveness and angiogenesis, which are important processes of tumour growth and spreading, require connective tissue remodelling. This process is dominantly mediated by matrix metalloproteinases (MMP), which are well known to be positively regulated by relaxin (RLX) in various tissues, including human breast cancer. So far, the presence of RLX and its receptor RXFP-1 as well as their linkage with MMP in canine mammary tumours (CMT) is completely unknown. In the first part of the present study, concentrations of RLX, oestradiol and progesterone from plasma samples of bitches with CMT were compared with clinical and survival data to investigate the predictive value of these hormones. In the second part, the expressions of RLX, RXFP-1 and MMP-2, -9 and -13 were examined by real-time reverse transcriptase polymerase chain reaction (RT-PCR) in 31 CMT samples. Finally, relationships of systemic plasma RLX or locally expressed RLX with expression of MMP in CMT were analyzed for the first time. Comparison of hormone concentrations in 93 bitches in terms of benign or malignant nature of the CMT, lung metastases, recidivation and 12-month survival discovered no significances. The expressions of RLX, RXFP-1 and MMP were independent from plasma RLX, but expressions of local RLX and RXFP-1 showed a strong correlation (p = 0.00004, r = 0.671) as well as RXFP-1 and MMP-2 (p = 0.009, r = 0.463), indicating a possible significant role of the locally produced RLX in CMT pathogenesis as an inducer of connective tissue remodelling.