Digestive and metabolic adaptations of ruminants to undernutrition, and consequences on reproduction

Abstract

-In response to undernutrition, short-(days) and medium-term (weeks) adaptations are more pronounced for splanchnic organs than for other tissues. For the latter, the long-term response involves a sequential mobilization (fat > muscle > bone) with

Indices of heart rate variability as potential early markers of metabolic stress and compromised regulatory capacity in dried-off high-yielding dairy cows

“…A reduced blood supply to the portal-drained viscera, mainly the rumen and liver, and thus, a decreased metabolic rate of these organs presumably contribute markedly to energy conservation (Chilliard et al, 1998). All cows also lowered physical activity (reduction of movements, shorter standing times) during P2 which is contrary to experimental results showing that steers (Derno et al, 2005) and calves (Schrama et al, 1995) spend more time standing during energy restriction.…”

“…Stress-induced hyperthermia is known to be mediated by the dorsomedial hypothalamus and sympathetic premotor neurons in the rostral medullar raphe region that induce thermogenesis and peripheral vasoconstriction (Kataoka et al, 2014) which is in accord with activation of the sympathetic branch of the ANS in pregnant, fasting <L MAX cows. The plasma level of cortisol is influenced by feeding and by the nutritional status (Samuelsson et al, 1996, Chilliard et al, 1998, and has been shown to increase as an anticipatory response to forthcoming food (Willett and Erb, 1972) and in feed-deprived cows (Mills and Jenny, 1979;Samuelsson et al, 1996). Elevated levels of cortisol are important for glucose supply in animals being in NEB (Samuelsson et al, 1996), but a noticeable increase was only seen in lactating >L MAX cows at day 2 (P2 + P3) of the experiment.…”

“…Because of the well-known interactions between metabolic stress, nutrition and reproduction, various metabolites (i.e. non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, lactate) and reproductive hormones are commonly used (Chilliard et al, 1998;Mudron et al, 2005). In addition, the plasma level of cortisol and the heart rate (HR) are applied to assess a stress response and/or the welfare status, and both are known to be influenced by feeding and by the nutritional status (Beerda et al, 2004;Davidson and Beede, 2009;Turbill et al, 2011).…”

“…The autonomic nervous system (ANS) plays a predominant role in regulating the adaptive response to inadequate energy and/or fuel availability and the resulting metabolic stress (Fröhli and Blum, 1988;Chilliard et al, 1998). Particularly, the ANS influences the metabolic rate in organs such as heart, liver and gastrointestinal tract.…”

“…The sympathetic nervous system (SNS) activity in a variety of tissues/organs is increased in conjunction with high feeding levels and is decreased during starvation (Fröhli and Blum, 1988). Also, the SNS and epinephrine are mainly involved in control of protein kinase A-mediated lipolysis during periods of NEB (Chilliard et al, 1998). Together with the adrenocortical axis and behavioural adaptations, the SNS belongs to the main mediators of the stress response (Mudron et al, 2005).…”