Running Head: GROWTH CURVE DIFFERENCES FOR TWO BREEDS OF GUIDE-DOGS
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Growth Curve Differences for Two Breeds of Guide-Dogs
Kalliopi Karaiskos
Salt Lake Community College
October 25, 2014
Growth Curve Differences for Two Breeds of Guide-Dogs
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Growth Curve Differences for Two Breeds of Guide-Dogs
A guide-dog may be the only aid for some blind people to reach destinations with greater
speed and confidence by locating obstacles and avoiding them. When determining the
appropriateness of a dog breed for the task of being a guide dog their physical dimensions need
to be carefully considered. While heavy dogs prove too difficult for the owner to handle, a
smaller dog may not be sufficient for performing this job safely. A more efficient protocol for
selecting dog types could cut costs by enabling the facilities to raise and train fewer dogs. In
order to devise a formula for this purpose, it is necessary to gain a better understanding of dog
growth. The application of previous studies is limited due to the fact that while previous studies
measured growth of specific breeds, they did not follow the study through the entire growth
period. “A better understanding for growth curves for guide dogs may aid in estimating mature
weight at a young age, thus allowing earlier breeding and training decisions to be made and
increasing genetic change per year” (Helmink, et al., 2000, p. 27).
Objectives
The purpose of tracking the dogs’ growth was to establish baseline for the growth of specific
breeds of dogs and the genders within those breeds, in order to find the similarities and
differences amongst them. Another objective was to “approximate the average weight of mature
dogs as well as when that weight is reached” (Helmink, et al., 2000, p.27).
Methods and Materials
1558 German Shepherds and Labrador Retrievers, raised by the Seeing Eye Inc., in
Morristown, NJ, were weighed every day for the first week of their lives, and again once each
week until the dogs were anywhere from six to eight weeks old. The dogs were then placed in
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homes until twelve to fourteen months, at which point weights were recorded periodically if the
dogs were brought into the facility throughout their training to become a guide dog. Weights
were not accounted for if the age was more than 550 days, if the dog did not have an observation
between 290 and 550 days, or if the dog was older than 550 days. After this alteration of data
there were a remaining 10,484 observations for 880 dogs. The method for measurement chosen
for this research was The Gompertz Function. The formula used was Wt=Wmaxexp(-e{-(t-c)/bl);
where Wt is weight at time, Wmax is mature body weight, b is proportional to duration of growth,
c is age at point of inflection, and t is age in days.
Results
Estimates for mature body weight, duration of growth, as well as the estimate for age at
point of inflection were all greater for males than females. Duration for growth and the
measurement for age at point –of-inflection was the same between breeds, while, measurements
of mature body weight were greater for Labrador retrievers than for German shepherds, with
male Labrador retrievers being the closest to the heaviest limit for desirable weight. Female
Labrador retrievers had the shortest estimate for growth. The male Labrador retriever was closest
to the maximum weight allowed, with the highest estimated mature weight being thirty-one kg
and the highest desirable weight being thirty-two kg.
Discussion
Establishing growth curves for the two types of breeds and the genders within those
breeds can help provide curial information when breeding and selecting dogs for the purpose of
becoming a guide dog, including the average mature weight and the average growth term for
these specific types of dogs. Of the dogs weighed, only six females and one male were below the
ideal eighteen kg. This proves the breeds chosen were the ideal breeds for the study, even
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regardless of the fact that one-hundred-nineteen of the dogs were above the ideal thirty-two kg,
because, a large percentage of those were male Labrador retrievers. According to the study, “the
temperament and trainability of the [Labrador retriever] for guide work provides incentives to
keep [them] in the breeding program” (Helmink, et al., 2000, p. 31).
Limitations
Upon returning to the facility many of the dogs either lost weight because they were
returned to a regulated feeding and exercising schedule, or, gained weight because they were
going through an adjustment period when taken from a home life, to kennel living. Meaning, The
Gompertz Function may have overestimated the mature weight of some of the dogs because it
was influenced by a weight change when the dogs were originally returned to the facility.
According to the study, using either multiphasic function or linear regression to include this
influx or decrease in weight may return more accurate results (Helmink et al., 2000, p. 31).
Another limitation may have been the lack of measurements taken between sixty-one and
332 days while the animals were not at the facility, more data gathered may have changed the
results.
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References
Helmink, S. K., Shanks, R. D., & Leighton, E. A. (2000). Breed and sex differences in
growth curves for two breeds of dog guides. American Society of Animal Science, 78,
27-32.