Relations entre le nombre de fœtus par corne utérine, la taille de portée à la naissance et la croissance pondérale des lapereaux

Abstract

Résumé—Au total, 246 lapines de la souche INRA0029 ont été mises en place pour réaliser deux portées en insémination artificielle. La moitié avait préalablement subi une ovariectomie unilatérale pour doubler le nombre de foetus dans une corne utérine. Le nombre de foetus implantés était compté par endoscopie. Il existe une relation du nombre d'implants positive avec la taille de portée et négative avec le taux de survie foetale. Il y a une relation de la taille de portée positive avec le poids total des nés vivants et négative avec le poids moyen des lapereaux nés vivants. L'effet défavorable du doublement de la population dans une corne sur le taux de survie foetale (-5,2 points) et le poids moyen des lapereaux à la naissance (-2,6 g) est significatif, mais beaucoup plus faible. En deuxième parité, les portées étaient standardisées à six lapereaux à la naissance, qui étaient pesés chaque semaine jusqu'au sevrage, puis à 7 et 11 semaines pour les femelles conservées. La relation négative entre poids individuel et taille de portée à la naissance est significative quel que soit l'âge, malgré un effet favorable de la taille de portée à la naissance sur la production de lait pendant les deux premières semaines. L'effet défavorable du groupement de tous les fcetus dans une seule corne est beaucoup plus faible et de moins en moins marqué quand l'âge des lapereaux augmente ; l'effet défavorable sur la croissance est une conséquence de l'effet sur le poids à la naissance. Il n'y a aucun effet du surpeuplement utérin ou de la taille de portée sur la croissance après sevrage. La diminution du poids des lapereaux issus de grandes portées semble donc essentiellement due à une compétition nutritionnelle pendant la gestation entre tous les fcetus et non à un surpeuplement physique des cornes utérines. L'augmentation de la prolificité doit donc s'accompagner d'une meilleure couverture des besoins de la lapine gestante.lapin / reproduction / croissance / effets maternels Summary — Relations between the crowding of the uterine horns, litter size at birth and growth of young rabbits from birth to 11 weeks, after cross-fostering of litters. The effect of the number of foetuses during pregnancy and of litter size at birth on young rabbits' weight at birth and up to 11 weeks was investigated. Two hundred forty-six does from the INRA0029 strain were bred in artificial insemination. Half of them were unilaterally ovariectomized before puberty in order to achieve a double crowding of the uterine horn corresponding to the remaining ovary and so to challenge the uterine capacity. The number of implanted foetuses was counted by endoscopy. There was a positive relationship of the total number of implanted embryos with litter size at birth, in spite of a negative relationship with the foetal survival rate. There was a positive relationship of litter size at birth with the litter weight, in spite of a negative relationship with the average weight of young rabbits alive at birth. The unfavourable effect of double crowding of one h...

Characterization of Local Algerian Population of Rabbit: Factors Influencing Fetal and Placental Development

“…In primiparous, the horns with 5 or 6 fetuses present a higher number of blood vessels than those with the same number in nulliparous (+25%). As regards the relationships between parity order and reproductive traits, our results agreed with existing literature describing best development of genital tract at primiparous stage (Parigi Bini et al, 1989;Bolet et al, 1996;Boumahdi et al, 2009) and in turn a better vascularization (Argente et al, 2008). The fetal weight and fetal crown-rump decreased when the number of fetus per horn increased (p < 0.05) and when the horn contains 5 fetuses, the fetal crown-rump and weight were reduced in nulliparous compared to primiparous does (-9% and -24% respectively).…”

“…According to Szendrö et al (1996), the mortality rate is lower (-12.6%) in the class of rabbits with a birth weight between 60 and 69 g compared to rabbits kits weighing between 40 to 49 g. The weight of rabbit kits at birth is influenced by several factors during the pregnancy period (litter size, kindling number, physiological status, nutrition, intra uterine position and vascularization of the fetuses). Indeed, the average individual birth weight increase when the litter size decrease, as the degree of nutrient supply per foetus is more favorable in does carrying fewer young (Duncan, 1969;Lebas, 1982;Garcia-Ximenez & Vicente, 1993;Bolet, 1994;Bolet et al, 1996). The growth of the fetuses is influenced also by the parity order of the doe.…”

Rabbit milk: A review of quantity, quality and non-dietary affecting factors

“…On the contrary, does with medium and high litter weight at birth (>450 g) had a significant higher yield by assigning additional kits. Due to the limited number of kits born or suckling kits in some non selected lines or populations, maximum milk production can therefore not be reached as demonstrated by Bolet et al (1996). However, Zerroucki et al (2005) demonstrate in a local population that maximum does milk production capacity can be reached for a number of kits lower than the maximum litter size naturally observed in this population: in theses author's observations milk production increases regularly with the suckling kits number until a maximum (7 in the present case) above which a plateau production is observed whatever the kits number (7, 8 or 9).…”

Genetic homogenisation of birth weight in rabbits: Indirect selection response for uterine horn characteristics

“…It has already been shown that there is a great heterogeneity of foetus weight (Bolet et al, 1996), which may be influenced by its location in the uterine horn (Lebas, 1982). In this experiment, the litter weight at birth is considered as a trait of the rabbit doe.…”

“…Rabbit birth weight presents a great variability within each litter (Bolet et al, 1996). Reducing this heterogeneity may be useful for the rabbit industry, since it induces a high mortality, as a result of the loss of the weakest rabbits.…”