Determination of heat-exposure effects on the concentration of catecholamines in bovine plasma and milk

Stress-Induced Suppression of Milk Protein Is Involved in a Noradrenergic Mechanism in the Mammary Gland

Stress decreases milk components such as milk protein and milk yield. The objective of this study was to investigate whether noradrenaline (NA) in milk constituted a factor associated with stress-induced changes in milk proteins such as β-casein. Breast milk obtained from eight healthy, nursing women contained NA at concentrations ranging from 12.7 to 115.5 nM. The expression of tyrosine hydroxylase (TH), a rate-limiting enzyme of NA synthesis, was observed in primary normal human mammary epithelial cells (HMECs), and in MCF-12A and MCF-10A cell lines. The mean NA concentration in culture medium used by MCF-12A transfected with TH small interfering RNA (siRNA) was significantly lower than that of cells transfected with control siRNA. NA concentration in milk in restraint-stressed nursing mice was significantly higher than that in nonstressed nursing mice, owing to elevated TH expression in the mammary epithelium. The mean β-casein concentration in milk in restraint-stressed mice was significantly lower than that in nonstressed mice. NA treatment resulted in a concentration-dependent decrease in β-casein expression in HMECs. β2 adrenergic receptor (ADRB2) expression was observed in HMECs, MCF-12A, and MCF-10A, and immunohistochemical analysis of ADRB2 using mammary epithelium sections obtained from mice at day 10 of lactation showed that ADRB2 was expressed at the apical membrane of mammary epithelium. Treatment with salbutamol, an ADRB2 stimulant, decreased β-casein expression in a concentration-dependent manner in MCF-12A. Our results showed that endogenous NA derived from mammary epithelial cells likely comprises one of the factors involved in stress-induced changes in milk proteins such as β-casein.

Up-regulation of milk secretion with modified microclimate through manipulating plasminogen-plasmin system in Murrah buffaloes during hot dry season

The present study was aimed at determining changes in milk yield and composition along with the plasminogen-plasmin system of milk, plasma hormones, and metabolites of buffaloes during hot dry season (air temperature range 39.7 to 44.8 °C) under two different management systems. Buffaloes were divided in two groups of six animals each: control and treatment, where treatment group animals accessed benefit of mist and fan cooling from 9:30 a.m. to 5:00 p.m., while control group animals were devoid of it. Duration of experiment was 6 weeks. Under mist and fan cooling system, buffaloes experienced better comfort by alleviating environmental stress as their physiological responses such as rectal temperature, respiration rate, pulse rate, and forehead and middorsal temperatures were significantly (P < 0.05) reduced compared to control, which subsequently resulted higher milk yield by 4.44 % (P < 0.001). Analysis of milk samples revealed higher concentration of plasminogen (7.99 vs 6.27 μg/ml; P < 0.01) and β-casein (1.09 vs 0.92 g/dl; P < 0.001) and lower plasmin level (0.178 vs 0.194 μg/ml; P < 0.05) in buffaloes under the treatment group compared to that under the control. Plasma glucose level was higher (P < 0.001) by 21.08 %, whereas cortisol, norepinephrine, and NEFA levels were lower (P < 0.001) by 19.19, 15.38, and 11.41 %, respectively, in treatment animals. However, exposure of buffaloes to cooling system did not alter composition and calcium content of milk, GH, and epinephrine level in plasma. Hence, it may be concluded that provision of cooling system during summer was effective to minimize environmental stress and improve milk production by manipulation of the PG-PL system in buffaloes.