title: Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development.
abstract: In a 15-month study, the effects of prepubertal gonadectomy on skeletal growth, weight gain, food intake, body fat, secondary sex characteristics, and behavioral development were investigated in 32 mixed-breed dogs. Male and female pups from 5 litters were randomly allotted to 3 groups: group I, neuter at 7 weeks (n = 14); group II, neuter at 7 months (n = 8); and group III, sexually intact dogs (n = 10). Growth plate closure was delayed (group I vs group III; P less than 0.000001; group II vs group III, P less than 0.000001) in all neutered dogs, as compared with sexually intact dogs. Growth plate closure was delayed longer (group I vs group II, P less than 0.000045) in dogs neutered at 7 weeks old, compared with dogs neutered at 7 months old. The rate of growth was unaffected by gonadectomy, but the extended growth period resulted in greater final radial/ulnar length in all male dogs and bitches neutered at 7 weeks. Gonadectomy did not influence food intake, weight gain, or back-fat depth. Penile development was immature in the adult group-I males (mean +/- SEM diameter of pars glandis = 11.1 +/- 1.0 mm), compared with adult group-II (16.3 +/- 0.5 mm) and group-III (21.0 +/- 2.2 mm) males. Subjectively, the prepuce and os penis of the group-I males were immature, compared with those of group-II and group-III males. Vulvar development in group-I and group-II bitches was less mature than vulvar development in the sexually intact bitches. Of 7 behavioral characteristics assessed, only general activity and excitability rated differently among treatment groups. All neutered dogs were judged to be more active (group I, P less than 0.004) than sexually intact dogs. Group-I males were judged to be more excitable (P less than 0.02) than group-III males. It was concluded that with respect to skeletal, physical, and behavioral development, the effect of neutering pups at 7 weeks old was similar to that of neutering pups at 7 months old.
authors.affiliation: Department of Small Animal Clinical Sciences, University of Florida, Gainesville 32610-0126.
authors.forename: K R
authors.initials: KR
authors.lastname: Salmeri
authors.forename: M S
authors.initials: MS
authors.lastname: Bloomberg
authors.forename: S L
authors.initials: SL
authors.lastname: Scruggs
authors.forename: V
authors.initials: V
authors.lastname: Shille
mesh_terms: D000273:Adipose Tissue / Q000254:growth & development; D000367:Age Factors; D000818:Animals; D001522:Behavior, Animal; D001846:Bone Development; D004283:Dog Diseases / Q000209:etiology; D004285:Dogs / Q000254:growth & development / Q000601:surgery*; D004435:Eating; D004958:Estradiol / Q000097:blood; D005260:Female; D006132:Growth Plate / Q000502:physiology; D008297:Male; D009765:Obesity / Q000209:etiology / Q000662:veterinary; D009919:Orchiectomy / Q000009:adverse effects / Q000662:veterinary*; D010052:Ovariectomy / Q000009:adverse effects / Q000662:veterinary*; D010413:Penis / Q000254:growth & development; D011897:Random Allocation; D012727:Sex Characteristics; D012741:Sexual Maturation; D013739:Testosterone / Q000097:blood; D014844:Vulva / Q000254:growth & development; D015430:Weight Gain
chemical_list: D013739:Testosterone; D004958:Estradiol