Resumen de Some factors affecting production and milk composition characters in a crossbreeding experiment involving Gabali and V- line rabbits in Egypt.
M.M. Iraqi, M.E. Shenana, Manuel Baselga Izquierdo
Data from 662 litters and 221 samples (two replicates per each sample) of rabbit milk were collectedfrom three different genetic groups [Gabali (G), V-line (V) and G×V (F1)] to study the effect of line and of somenon-genetic factors affecting production and milk composition traits. The studied traits were: number bornalive (LSBA); litter size at weaning (LSW); litter weight born alive (LWBA); litter weight at weaning (LWW); totalmilk yield (TMY) and protein, fat, total solids (TS), ash, phosphorus (P), potassium (K), sodium (Na), calcium(Ca) and magnesium (Mg) milk content. The genetic group effect was significant for LSBA [V (7.3) and F1(7.3)were superior to G (6.6)); LWBA (higher values for V (416 g) and F1 (405 g) than for G (382 g)]; TMY [G (3497g) and F1(3486 g) higher than V (3042 g)]; milk fat [F1 (26%) and G (25%) superior to V (23%)] and milkTS[F1(42%) superior to G (40%) and V (39%)]. The estimates of the heterosis effect ranged between 1.6% and12.8% for production and milk gross chemical traits, being significant only for milk fat content (9.1%). Thepositive values of the heterosis estimates for those traits and the complementarity between the G breed andthe V line, the G superior in milk related traits but the V superior in prolificacy, show the interest of their crossand of the synthetic lines derived from them. The heterosis was non-significant for milk mineral content traits.The parity effects were significant for LSBA, fat, TS, ash and K (the maxima were reached at 6th or 5th parity).The effect of week of lactation was significant for fat, ash and TS, corresponding the maximum values of fatand TS to the 3rd and 4th week. The year-season or the year-month effects were significant for all traitsshowing the importance of including these time-period factors into the statistical models proposed for the traits.
