Breed and sex differences in growth curves for two breeds of dog guides
I. Introduction
A. Choosing a dog breed(s) that meets the acceptable size limits, minimum and
maximum to safely guide, but not to over power the owner.
1. The optimum weight of good mature dog breed should be between
18kg to 32kg. This selection process was determined by using a
mathematical formula known is the Gompertz function to determine
the average minimum and maximum size of adult dogs of two
different breeds, the German Shepard and the Labrador retriever.
2. Mathematical functions (Gompertz function) were used to show the
growth models of the two breeds of dogs. The objectives of this
research were to construct average growth curves for male and
female German Shepard dogs and Labrador retrievers, find
similarities and differences in growth within and between the breeds
and sexes, and approximate the average weight of mature dogs as
well as when the mature weight is reached. (Helmink, Shanks &
Leighton, 2000)
B. The study was done to help facilitate in choosing a breed(s) of dog(s) that are the
appropriate weight as an adult dog.
1. Prior studies did not account for the entire growth period, so results
were limited.
2. Proper dog selection saves money. This is due to fewer dogs needing
to be trained and breed as the average dog selected would be more
within the range of acceptability.
C. The goal of this study was to create average growth curves for male and female
dogs of the Labrador and German Shepard families.
II. Materials and Methods
A. Information was collected over a 6 year period in which over 18,000 weight
observations were recorded on over 1550 Labrador retrievers and German
Shepard dogs by the Seeing Eye, Inc., in Morristown NJ.
1. “Weights were recorded daily for the first week of life, then weekly until the
dogs were 5 to 8 wk of age. (Helmink, Shanks & Leighton, 2000)
2. Weights of dogs were recorded up to 12 to 14 months of age if the
caretakers brought the dogs the Seeing Eye during this time.
B. The Gompertz Function.
1. Selected over the logistic function, Diphasix logistic function, and von
Bertalanffy function. This selection was due to the fit of data and the
suitable point of inflection for modeling dog growth, and previous use of the
Gompertz function in the literature. (Helmink, Shanks & Leighton, 2000)
2. The Gompertz function was chosen for its adequate fit of data.
III. Results
A. The average weight of adult male and female Labrador retrievers and German
Shepard dogs were recorded. Labrador retrievers were heavier on average than
German Shepard’s, and males were heavier than females.
1. The average weight of Labrador retriever dogs was almost 5 lbs more than
German Shepard dogs.
2. Weight average of male dogs was approximately 10 lbs heavier than female
dogs. The correlation of breed and sex interaction did not make for any
significance in mature weight.
B. Estimate for growth duration was longer in male dogs.
1.
Male dogs took between 3 – 13 days longer on average to reach an average
mature age. The breed of dogs didn’t have any noticeable difference in
duration.
2.
Male dogs took an average of 2.4 – 4.8 days longer to reach point of
inflection. Once again, the Breed and sex interaction made no difference in this
study.
IV. Discussion
A. It is important to separate male populations from female populations when
doing a study on growth.
1. Male Labrador retriever dogs’ weight is the closest to the maximum ideal
weight, averaging 31kg. The maximum ideal weight for guide dogs is 32kg.
2. Over ½ of the dogs above the ideal maximum were male Labradors. Once
returned to the facility the dogs were put on a regulated feeding and
exercise program. 16% of the reported 880 dogs lost a minimum of 2.27kg
in the time they returned to the facility and 550 days of age.
B. The fewest recorded weight observations were between 2 to 11 months. More
data during this time pe3riod may change the results and has the potential to
increase the accuracy of the parameter estimates. (Helmink, Shanks & Leighton,
2000)
References
S.K. Helmink, R.D. Shanks, and E.A. Leighton (2000). Breed and sex differences in growth curves
for two breeds of dog guides. Journal of Animal Science, 78, 27-32.