Spatio-temporal extension of the INRA 2018 goat model. 2. Dynamic changes of body reserves, body weight and body condition score throughout a whole productive cycle

Abstract

The objective of this study was to use the dynamic relationships of the INRA 2018 nutritional model to simulate changes in body weight (BW), its components (e.g. body reserves) and body condition score (BCS) of goats throughout a whole productive cycle. In a first step, the approach considered separately the changes induced by lactation, gestation and growth since the available information and computing steps were not the same for the three physiological stages. A model of gut contents was used to achieve the prediction of BW and empty body weight (EBW). For lactation, equations for energy changes in body reserves were used to determine cumulated energy balance and then BW dynamics, accounting for the effect of milk production potential. For gestation, BW and EBW dynamics were used to differentiate gravid uterus, depending on prolificacy, from maternal mass. For this latter, an original approach allowed the estimation of maternal anabolism in early gestation and catabolism in late gestation, both depending on the effect of prolificacy. For growth, the approach based on BW at birth and at maturity did not raise specific problems. Dynamics of BW and EBW for the 3 physiological stage were combined to predict the overall dynamics throughout a productive cycle, and the BW “format” was integrated as an input parameter. Finally, predicting BCS was based on relationships between sternal BCS and lipid content in BW. Equations for converting sternal BCS into lumbar BCS were also proposed. BCS dynamics were computed for each physiological stages, in particular during gestation to account for maternal mass changes. All these equations were included in the Ruminal’caprin software.