Effects of animal type (wild vs. domestic) and diet alfalfa level on intake and digestibility of European adult rabbits (Oryctolagus cuniculus)
The diet of domestic rabbits is usually composed of pellets, which composition is based on forages, grains and various by‐products of the agro‐food industry and formulated to meet their nutritional needs and to achieve and/or maintain a healthy status (De Blas & Mateos, 2010; Irlbeck, 2001).
Alfalfa is an ingredient of excellence as fibre but also as protein source for rabbits and is the most widely recommended forage for these animals (Linga & Lukefahr, 2000). Its hay is frequently included in commercial formulas because it is highly palatable and it provides both long and digestible fibre's, which promote an adequate transit time of the digesta and a balanced growth of the caecal flora (De Blas & Mateos, 2010). However, alfalfa is low in energy and should be supplemented when fed to rabbits (Jouglar & Lebas, 1986; Oyawoye, Oyikin, & Shehu, 1990).
In rabbits, as in other animals, many factors can affect feed intake and digestibility. The diet composition, notably the level and type of fibre, starch and protein (De Blas & Mateos, 2010; Gidenne, Pinheiro, & Falcão e Cunha, 2000; Monk, 1989; Nicodemus, García, Carabaño, & De Blas, 2007), the age (Gallois, Fortun‐Lamothe, Michelan, & Gidenne, 2008; Perez, Fortun‐Lamothe, & Lebas, 1996), and the physiological status of the rabbits (Iyeghe‐Erakpotobor, Oyedipe, Eduvie, & Ogwu, 2007; Prasad & Karim, 1998) are some of the variables most frequently studied and reported in literature. The effect of the genotype has been also reported, namely in experiments that compared the feed intake and the digestibility by different rabbit breeds (Oke, Ibe, & Ogbonnaya, 2004; Ozimba & Lukefahr, 1991) and rabbit lines (Feki, Baselga, Blas, Cervera, & Gómez, 1996; Ondruška, Chrastinová, Chrenek, Rafay, & Parkányi, 2010; Orengo, Piles, Rafel, Ramon, & Gómez, 2009). There are also studies comparing the intake and digestion capacity of rabbits with other species (Franz, Kreuzer, Hummel, Hatt, & Clauss, 2011; Hagen, Tschudin, Liesegang, Hatt, & Clauss, 2015; Slade & Hintz, 1969), but no experiment was performed, to the author's knowledge, comparing intake and digestibility by wild versus domestic rabbits.
The rabbit, like any other animal, ingests food to fulfil its metabolic requirements, and it is accepted that these requirements do not correlate linearly with BW. The mathematical expression that better describes the correlation between the BW and the metabolic requirements in homoeothermic animals, in general, and within specific species in particular, is more controversial. Since Kleiber (1947), the two most widely used expressions appointed in literature as being the unifying base for metabolic requirements expression, known as metabolic weight, are the BW0.75 and the BW0.67. As it is not clear which is the more accurate way to express the metabolic requirements, it is interesting to compare the intake of homoeothermic animals (including rabbits) based on the two metabolic weight expressions.
The domestication imposes adaptation challenges to the animals, and the response to the artificial habitat conditions is expected to induce changes in the animal's physiology. Current anthropogenic pressure on wild populations imposes the need to raise wild animals under artificial conditions.