Analysis of weaning-induced stress in Saanen goat kids.

In young ruminants' life, weaning often coincides with a period of growth stasis and poor welfare. The present study aimed at evaluating the effect of coping with the new diet on behavioural and haematological stress indicators in goat kids subjected to a commonly adopted weaning practice. Immediately after birth, male Saanen goat kids were divided into two groups: MILK and WMIX. All were fed colostrum for the first 3 days and then goat milk to the age of 29 days. After that, MILK kids continued to receive milk, while the WMIX kids underwent weaning and were completely weaned by day 48. Animal behaviour was recorded daily. From day 23-50, blood samples were taken weekly and analysed for indicators of stress and immune function. No abnormal behaviour, such as injurious behaviours or stereotypies, was observed in either of the experimental groups throughout the experimental period. During the last week, fasting plasma cortisol level was significantly lower, whereas plasma activity of both alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was significantly higher in WMIX kids, in relation to the MILK ones. Anyway, data were within the normal physiological range and no difference was observed neither in plasma haptoglobin, ceruloplasmin, albumin and antithrombin III, nor in plasma immunoglobulin A and G, at any time, signalling no stressful condition. Therefore, differences observed in cortisol, ALT and AST could be the consequence of the metabolic changes that occur during the transition from pre-ruminant to ruminant state. The gradual weaning at 48 days of age did not result in any stressful condition and had no negative effect on weight gain. Results suggest that parameters commonly adopted to provide information on animal stress, such as cortisol and aminotransferase activity, can vary in relation to the physiological status of the animals and may bias stress assessment.

Diet influences the content of bioactive peptides in goat milk.

Leptin, insulin, ghrelin, and IGF-I are circulating peptide hormones concerned with energy homeostasis and the regulation of GH axis. They are present in human milk, and are thought to promote neonatal development. The aim of the present study was to detect these substances in goat milk and determine whether their levels can be modified by changing the macronutrient content of the lactating animals' diet. Sixteen Saanen goats in mid-lactation were divided into two balanced groups, one given a diet containing 17% starch (LS) and the other a diet of 33% starch (HS). Eighty days later, leptin, insulin, ghrelin, and IGF-I were determined by human radioimmunoassay kits in plasma before and after feeding, and in sonicated milk centrifuged to remove fat from morning and evening milking. The HS diet was associated with higher plasma and milk insulin and IGF-I, and plasma ghrelin. Leptin, insulin, and ghrelin in milk were two-three times higher than in plasma; milk IGF-I was only 5-20% of plasma level. Plasma insulin correlated positively with plasma IGF-I; morning milk IGFI and insulin correlated positively with morning plasma levels. These findings demonstrate that human immuno-activities of bioactive peptides are present in goat milk, and also that levels of insulin and IGF-I in milk can be altered by changing the macronutrient content of the diet. Further research is required to determine whether these substances can be transferred from the milk to suckling animals and humans, and whether they have biological activity in such animals.