The research-theme on adaptation and stress aims to unravel the mechanisms behind the transition from a physiologically adapted, high producing farm animal to situations of (pathophysiological) non-adaptation under the influence of stress conditions. Read-out parameters of non-adaptation are e.g. subfertility and reproductive disorders (impaired oocyte quality; lowered pregnancy rates; the occurrence of early embryonic and fetal death; cystic ovarian disease; impaired cervix function), health disorders (ketosis; mastitis; digital disorders, abomasal displacement; disturbed liver and immune function; disorders during the perinatal period and after weaning; mortality), and/or behavioural disturbances.
Nutritional and metabolic stress around parturition in the high yielding dairy cow is an increasingly important phenomenon because during this period the physiological balance of the animal is challenged. In the same period the feed intake is usually reduced, and energy intake does no longer meet the energy requirements for maintenance and reproduction. Consequently, the energy balance becomes (often severely) negative, and the metabolic situation of the animal further deteriorates because of other stressors that exert their effect on the animal (e.g. mineral status; reactive oxygen metabolite formation versus lack of anti-oxidants; subfertility and reproduction disorders; infections; excessive body condition leading to fat cow and fatty liver syndrome). In extreme situations this fatty liver syndrome occurs due to the deposition of surplus TAG. Then, an anabolic process accompanies the catabolic process of lipolysis. The research line 'Adaptation and stress' focuses on these multifactorial phenomena and underlying mechanisms, which can be reflected in several endocrinological, immunological and biochemical parameters, and 'once determined' can be used to define the level of adaptation in the animal more accurately.
In modern pig husbandry, piglets weaned at an age of four weeks are confronted with an abrupt diet change. This transition implies abstinence of (epithelial) growth factors from sow milk, the inability of piglets to digest complex plant (lectin) proteins and a drop in feed intake. Consequently the nutrient supply to the small intestine drops dramatically after weaning. Moreover, the oxygen demand for digestion of complex nutrients in the newly weaned piglet increases, whereas the oxygen supply of the small intestine decreases as a result of the physical stress of weaning (hypo-perfusion). The resulting degeneration (villus shortening; crypt deepening) and functional changes (reduced absorption) of the small intestine contributes to a high incidence of post-weaning diarrhoea (also caused by shortage of absorption in the colon at this age) and allows macromolecules and bacteria (e.g. Streptococcus suis) to pass the gut mucosa. The research line 'Adaptation and stress' aims at a better understanding of the underlying pathophysiological mechanisms in order to enable the development of strategies to alleviate the forenamed constraints, and to improve health and welfare of piglets without compromising reproductive performance of the sows. Intermittent suckling might be an example of such a strategy. |
