Serum Non-Esterified Fatty Acids and Plasma Glycerol as Indicators of Fat Mobilization in Pregnant Sheep Subjected to Cold Stress

The effects of cold exposure of pregnant sheep on foetal plasma nutrients, hormones and birth weight

1. Five pregnant sheep, with indwelling catheters positioned for withdrawal of maternal right-atrial and foetal arterial blood, were exposed for 2 h to neutral and to cold (-10 and wool-clipped) environmental temperatures. Acute maternal cold exposure increased the concentrations of glucose, glycerol and non-esterified fatty acids in maternal plasma and increased the concentration of glucose in foetal plasma, but not glycerol or non-esterified fatty acids. The concentration of corticosteroids in maternal plasma increased. The concentration of corticosteroids in foetal plasma did not change but the concentration of insulin increased. 2. Thirteen pregnant sheep were housed at thermoneutrality and thirteen similar sheep, fed the same amount of food, were clipped and exposed to cold during the last 5-6 weeks of pregnancy. Chronic maternal cold exposure increased the birth weight of both single and twin lambs. 3. It is concluded that exposure of pregnant sheep to cold can alter the partition of some nutrients between mother and foetus in favour of the foetus, and it is suggested how this may be brought about.

Free glycerol in the plasma of cows

A survey is given on glycerol and its metabolism in the organism. Free glycerol in plasma was determined in 173 samples from 21 cows at 2 different farms. The highest concentration 110±42 µmol/1 was observed in the interval 0–2 days post partum. During the 3–45 days post partum interval, a significant difference was observed between the 2 farms (P < 0.001), with the highest values corresponding to the highest milk yields. The values found in cows correspond with levels previously reported for other species.