Adaptive abilities of the females and sustainability of ruminant livestock systems. A review

Abstract

-In a systemic approach, the breeder can be considered as the decisional component of the livestock system, whereas animals are usually depicted to be part of its biotechnical component. The animal itself is a biological system whose ability to survive, grow, reproduce and cope with the environnement and livestock practices play a major role in the ability of the livestock system to sustain. In such a conceptual representation of the system, the reproductive females draw a peculiar attention since they determine in a great part the productivity and the durability of the system through their abilities to maintain their own production level (milk production, numeric productivity) and to save their reproductive efficiency (repeated pregnancies and lactations) over years. Considering the animal level and its lifespan, it is clear that the abilities to adapt rely on behavioural and physiological regulatory processes. The study of the biological mechanisms involved in the adaptation to undernutrition is particularly interesting since regulatory processes implied in energy metabolism may interfere directly or indirectly with the reproductive function, and consequently, with the durability of the livestock system. A biological significance of such relationships between nutrition and reproduction is given that they allow the female to be informed about the associated risk of entering a productive process facing the uncertainty of the nutritional context. Although the general mechanisms implied in the ability to adapt to the underfeeding constraint are conserved among ruminants, the thresholds (or priorities) may largely differ according to the breed within the same species. Hence, in order to evaluate the ability of the ruminant livestock systems to perpetuate in hard environments (maintaining their production levels) or to assess sustainable objectives (opening bushy landscapes by increasing grazing pressure), animals' inherent adaptive potentialities have to be well known. Résumé -Capacités adaptatives des femelles et durabilité des systèmes d'élevage. Synthèse bibliographique. Dans une représentation systémique du système d'élevage, l'éleveur incarne la composante décisionnelle du système, tandis que l'animal constitue, avec la ressource, sa composante biotechnique. L'animal lui-même peut être considéré comme un système biologique soumis à un environnement contraignant, dont les aptitudes à survivre, croître, se reproduire et s'adapter jouent un rôle fondamental dans la pérennité du système d'élevage. Les femelles reproductrices tiennent une place particulière dans cette représentation car non seulement elles déterminent une large part de la productivité du système par leur propre niveau de production (production laitière, productivité numérique), mais elles en assurent également sa reproductibilité au cours du temps (investissement reproductif). A l'échelle de l'individu et de sa durée de vie, les modalités d'adaptation reposent sur des processus de régulations comportementales et physiologiques. De tels pro...

Effects of herbage allowance of native grasslands in purebred and crossbred beef cows: metabolic, endocrine and hepatic gene expression profiles through the gestation–lactation cycle

“…The present study indicates that the superiority of CR over PU cows was associated with a better metabolic status (greater BCS, serum insulin and hepatic GHR mRNA abundance) particularly in late fall (−165 days) and with greater hepatic IGFBP3 mRNA expression in late winter (−75 and −45 days) and in early lactation (+15 days). These results would support the concept of a 'metabolic memory' impacting reproduction, allowing nutritional information to be carried forward beyond the life of the original metabolic stimulus (Blanc et al, 2006) …”

Sustainability of ruminant agriculture in the new context: feeding strategies and features of animal adaptability into the necessary holistic approach

“…In addition, numerous transfers of improved dairy cattle from temperate zones to harsh environments revealed that performance were considerably lower due to the recognized effects of genotype-environment interactions (Hammami et al, 2008). The approach to analysing the exact causes of difficulties encountered with highly selected ruminants, even in ICs, is now questioned (see Blanc et al, 2006;Friggens and Newbold, 2007;Friggens et al, 2010).…”

“…Several functional responses of ruminants to underfeeding constraints have been described and classified according to the shape of the response curves (Blanc et al, 2006;Friggens and Newbold, 2007). In the case of domestic ruminants their adaptive response cannot be assessed only by the individual capacity of survival or even by the species perennity but, importantly, by the ability to sustain a given productive function.…”

“…When a biological sub-system has reached its breaking point some other metabolic pathways may be activated, and the global response is still elastic within a given range of intensity of perturbation or within a range of duration of this perturbation. With regard to reproduction, it has also been underlined (Blanc et al, 2006) that the introduction of a delay in the response is also a way of adapting to inadequate nutrition. This is particularly the case in species such as the bovines, whose reproduction should occur during lactation at a stage when the females are in strong negative energy balance (see Friggens et al, 2010).…”

Rangeland utilization in Mediterranean farming systems

“…When the herd or flock has to face alternative periods of low and high feed availability, the production cycle is secured by two well-known mechanisms: the mobilization and reconstitution of body reserves and the adjustment of animal performance, milk production for the lactating females or growth rate for the young (Blanc et al, 2006). In Lebanese Baladi dairy goats, each time the feed availability increases (i.e.…”