title: Influence of litter size and breed on variation in length of gestation in the dog.
abstract: The variation in the length of gestation, the period from mating until parturition, was studied in 77 dogs of different breeds; the time for mating was determined by measuring peripheral blood progesterone levels. The mean length of gestation was 62.1 +/- 0.2 (S.E.M.) days, with a variation of 11 days. The number of pups appeared to influence the length of gestation. Length of gestation was negatively correlated (r = -0.96, P < 0.001, n = 44) with litter size in litters with 7 or fewer pups. The intra-breed variation in length of gestation in the five breeds represented by five or more bitches was 3-6 days. The mean gestation of Alsatians (60.1 +/- 0.5, n = 9) was shorter (P < 0.005) than that of the other breeds combined (62.3 +/- 0.3, n = 68). The primiparous/multiparous status of the bitch did not influence the length of gestation.
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Okkens
authors.forename: T W
authors.initials: TW
authors.lastname: Hekerman
authors.forename: J W
authors.initials: JW
authors.lastname: de Vogel
authors.forename: B
authors.initials: B
authors.lastname: van Haaften
mesh_terms: D000818:Animals; D004285:Dogs / Q000097:blood / Q000235:genetics* / Q000502:physiology*; D005260:Female; D005865:Gestational Age; D008098:Litter Size / Q000502:physiology*; D011374:Progesterone / Q000097:blood
chemical_list: D011374:Progesterone