Long-term implications of feed energy source in different genetic types of reproductive rabbit females: I. Resource acquisition and allocation

Abstract

To achieve functional but also productive females, we hypothesised that it is possible to modulate acquisition and allocation of animals from different genetic types by varying the main energy source of the diet. To test this hypothesis, we used 203 rabbit females belonging to three genetic types: H (n=66), a maternal line characterised by hyper-prolificacy; LP (n=67), a maternal line characterised by functional hyper-longevity; R (n=79), a paternal line characterised by growth rate. Females were fed with two isoenergetic and isoprotein diets differing in energy source: animal fat (AF) enhancing milk yield; cereal starch (CS) promoting body reserves recovery. Feed intake, weight, perirenal fat thickness (PFT), milk yield and blood traits were controlled during five consecutive reproductive cycles (RCs). Females fed with CS presented higher PFT (+0.2 mm, P0.05), particularly for those fed with AF. Moreover, LP females fed with AF progressively increased PFT across the RC, whereas those fed with CS increased PFT during early lactation (+7.3%; P<0.05), but partially mobilised it during late lactation (-2.8%; P<0.05). Independently of the diet offered, LP females reached weaning with similar PFT. H females fed with either of the two diets followed a similar trajectory throughout the RC. For milk yield, the effect of energy source was almost constant during the whole experiment, except for the first RC of females from the maternal lines (H and LP). These females yielded +34.1% (P<0.05) when fed with CS during this period. Results from this work indicate that the resource acquisition capacity and allocation pattern of rabbit females is different for each genetic type. Moreover, it seems that by varying the main energy source of the diet it is possible to modulate acquisition and allocation of resources of the different genetic types. However, the response of each one depends on its priorities over time.

Long-term implications of feed energy source in different genetic types of reproductive rabbit females: III. Fitness and productivity

“…x 320 mm). Although not all the females began the experiment at the same time (231 days between the first and the last female), most of them did so during the first three months, when the lowest temperatures of the experiment were recorded (for details, see Arnau-Bonachera et al, 2017). The entry of animals from each of the three genetic types was distributed over time similarly.…”

“…Line H (n=66), founded by hyper-prolific criteria at birth and selected by litter size at weaning; line LP (n=67), founded by functional hyper-longevity characterised by a high robustness; line R (n=70), selected for average daily gain during the growing period. For a further description of the lines, see (Arnau-Bonachera et al, 2017).…”

“…11.3 MJ of digestible energy (DE) and 126 g of digestible protein per kg DM]. For a further description of the diets, see (Arnau-Bonachera et al, 2017).…”

“…We equalize litters to compare genetic types under similar lactational effort. However, when litters were standardised to 9.7 offspring, we forced R females to nurse many offspring of large size with non-adapted energy intake and milk output (Arnau-Bonachera et al, 2017). In other words, we set the reproductive effort to be much greater than that initially set by R females' genetic potential.…”

“…The main hypothesis of the series is that varying the main energy source of the diet we could alter the way each genetic type acquires and allocates resources over time, impacting in the immunological status of females or their fitness and productivity. In the first paper, we investigated the way three genetic types differing greatly in their genetic background acquire and allocate resources when fed with diets specially designed to influence either the milk production or body reserves (Arnau-Bonachera et al, 2017). In the second paper, we investigated parameters related to the immune system of these genetic types across time and how previous diets affected them (Penadés et al, 2017).…”