Comparison of nonlinear growth models and factors affecting body weight at different ages in Toy Poodles

Figures & data

Table 1. Nonlinear functions applied to describe the growth curves in Toy Poodle puppies.

Model	Function
Hawthorne^a	y = A/{1 + exp[−(x − x0)/d]}
Gompertz^b	y = A exp[−B exp(−kx)]
Brody^c	y = A [1 − B exp(−kx)]

y = body weight reached to age x: A = adult body weight (g); x₀ = time needed for reaching 50% of adult weight (weeks); B = proportion of the asymptotic mature weight to be gained after birth; k = mature growth rate (calculated as (1/d) by the Hawthorne model).

^aLogistic equation used by Hawthorne et al. (2004).

^bGompertz (1825) as modified by Rogers et al. (1987).

^cBrody (1945).

Table 2. Demographic data and management of the Toy Poodle dogs (n = 65) according to sex. Descriptive statistics: means ± SD or numbers and percentages.

Parameter		Sex		Total
		Male (n = 30)	Female (n = 35)
Birth body weight (g)		146 ± 25	161 ± 41	154 ± 35
Neutering	No	23 (76.7%)	31 (88.6%)	54 (83.1%)
	Yes	7 (23.3%)	4 (11.4%)	11 (16.9%)
Adult body weight (g)^a		3304 ± 864	3110 ± 927	3193 ± 898
Litter size (n)		—	—	3 ± 1
Daily activity	1–2 walking/day	7 (24.1%)	3 (9.1%)	10 (16.1%)
	>2 walking/day	6 (20.7%)	7 (21.2%)	13 (21.0%)
	Garden/box	16 (55.2%)	23 (69.7%)	39 (62.9%)

^aThe adult weight of 9 dogs (6 males and 3 females) was not included because they were lost to follow-up.

Figure 1. Changes in body weights (g) as a function of age (weeks) obtained with the observed curve and the three different growth models for Toy Poodle dogs.

Table 3. Growth characteristics and goodness of fit of growth curves calculated on 65 Toy Poodle dogs (30 males and 35 females).

Model	Category	A^a (g)	k (%)	CV for k (%)	T30 (weeks)	T50 (weeks)	T99 (weeks)	Goodness-of-fit
								R^2	AICc	RMSE
Hawthorne^b	Global	3150 ± 25	17.5	3.3	6.9	11.6	38.0	0.673	36692	672.67
	Male	3166 ± 33	19.1	4.7	6.8	11.2	35.2	0.696	16398	651.1
	Female	3102 ± 34	16.3	4.5	6.9	12.2	40.1	0.700	19994	658.1
Gompertz	Global	3242 ± 30	11.8	3.5	6.9	11.5	47.4	0.676	36667	669.7
	Male	3243 ± 40	13.0	4.9	6.7	10.9	43.6	0.697	16392	649.7
	Female	3222 ± 44	10.9	4.8	7.0	12.0	50.8	0.672	20042	659.9
Brody	Global	3560 ± 54	5.9	4.3	6.5	12.2	78.7	0.671	36707	674.5
	Male	3515 ± 68	6.5	5.7	6.1	11.2	71.4	0.689	16427	658.5
	Female	3625 ± 87	5.3	6.3	7.0	13.3	87.0	0.664	20212	677.1

^aBest fit value ± SE; ^bk calculated as 1/b.

A = estimated adult body weight (grams); AIC = Akaike’s Information Criteria; k = mature growth rate (%); CV = coefficient of variation; T_30, T₅₀, _and T₉₉ = time taken to reach 30, 50 and 99% of adult body weight, respectively; R² = coefficient of determination; RMSE = root mean square error).

Figure 2. Differences between mean observed and predicted values for the body weight (BW) of Toy Poodle dogs at different ages obtained by three different models.

Figure 3. Growth chart percentiles for males Toy Poodle puppies.

Figure 4. Growth chart percentiles for females Toy Poodle puppies.

Table 4. Factors affecting the weight of puppies at different ages, from 1 week to 3 months of age (12 weeks).

	Weeks of age
Parameter	1			2			3			4			9			12
	b	SE b	Sig.	b	SE b	Sig.	b	SE b	Sig.	b	SE b	Sig.	b	SE b	Sig.	B	SE b	Sig.
Intercept	105.66	31.01	0.001	184.73	57.55	0.002	375.43	76.46	<0.001	436.61	100.88	<0.001	420.39	164.77	0.013	824.22	287.52	0.006
Sex
Female	−20.95	10.37	0.047	−26.62	19.20	0.170	−68.41	25.51	0.009	−43.98	33.65	0.196	−228.96	54.97	<0.001	−224.11	95.92	0.023
Male	Ref.			Ref.			Ref.			Ref.			Ref.			Ref.
Birth body weight	1.07	0.16	<0.001	1.41	0.29	<0.001	1.95	0.39	<0.001	2.08	0.52	<0.001	4.00	0.84	<0.001	4.51	1.47	0.003
Mother’s BW	0.01	0.01	0.489	0.02	0.01	0.117	0.05	0.02	0.016	0.06	0.03	0.026	0.18	0.04	<0.001	0.24	0.07	0.001
Father’s BW	−0.00	0.01	0.904	−0.02	0.02	0.278	−0.06	0.02	0.009	−0.09	0.03	0.005	−0.06	0.05	0.258	−0.14	0.09	0.106
Litter size	−13.56	5.06	0.009	−14.94	9.37	0.116	−27.62	12.45	0.030	−7.34	16.42	0.657	−21.21	26.82	0.432	−12.23	46.81	0.795

Results of multivariable models (b coefficient, standard error of b, and significance of b). BW: body weight; Ref.: Reference; SE: standard error.

p values in bold denote statistical significance at the 0.05 level.

Table 5. Fixed-effect estimates and significance for model of the predictors of adult body weight (b coefficient, standard error of b and significance of b).

Parameter	b	Standard error b	Sig.
Intercept	475.535	668.087	0.481
Gender
Spayed female	−752.504	558.552	0.185
Intact female	−529.915	223.241	0.022
Castrated male	−302.426	385.717	0.437
Intact male	Reference
Daily activity
1–2 walking/day	41.409	277.146	0.882
>2 walking/day	−98.256	285.177	0.732
Garden available	Reference
Birth body weight	10.405	3.108	0.002
Mother’s body weight	0.548	0.150	0.001
Father’s body weight	−0.101	0.206	0.628
Litter size	−71.809	98.445	0.470
Management
Professional	−25.421	236.702	0.915
Owner	Reference

p values in bold denote statistical significance at the 0.05 level.

Hawthorne AJ, Booles D, Nugent PA, Gettinby G, Wilkinson J. 2004. Body-weight changes during growth in puppies of different breeds. J Nutr. 134(8 Suppl):2027S–2030S.

 PubMed Web of Science ®Google Scholar

Gompertz B. 1825. On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of life contingencies. Philos Trans R Soc Lond. 115:513–583.

 Google Scholar

Rogers SR, Pesti GM, Marks HL. 1987. Comparison of three nonlinear regression models for describing broiler growth curves. Growth, Dev Aging. 51(2):229–239.

 PubMedGoogle Scholar

Brody S. 1945. Bioenergetics and growth. New York, NY: Reinhold Publishing.

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