Body weights (BW) of 2,611 Muzaffarnagari lambs at birth and 3, 6, 9, and 12 months of age were used to compare five alternative growth curves. Four three-parameter functions (Brody, von Bertalanffy, Gompertz, and logistic) and the four-parameter Richards function were fit for each lamb. Estimates of the asymptotic final BW (A), a maturing-rate parameter (k), and the degree of maturity at birth (u₀) = BW/A were estimated for each function. A shape parameter (m) was included in the Richards function and used to identify the degree of maturity (u) at the point of inflection of the growth curve (u_I). Among three-parameter functions, the Brody function had the smallest pooled residual sum of squares (RSS) across all lambs and the smallest RSS for 56% of individual lambs. For the Brody function, the growth rate is maximum at birth and declines continuously as animals age. In comparison with the Brody function, fitting the Richards function with a variable inflection point did not significantly reduce RSS. Comparisons of Brody and Richards functions indicated that the Richards function converged to a Brody function for 17% of the lambs. The predicted growth rate was maximum at an average u_I of 0.26 for the Richards function and at an average of u₀ = 0.10 for the Brody function. Parameters k and m interacted to define the maturing rate in the Richards function, and the predicted age at u= 0.50 (t₅₀) was proposed to measure growth efficiency. Correlations between estimates of A, u₀, and t₅₀ for the Brody and Richards functions were all 0.89, confirming limited benefit from fitting the Richards function. For the Brody function, correlations among estimates of A, k, and u₀ were modest (-0.59 to 0.39). Use of these parameter estimates in selection to modify the growth curve would be relatively straightforward. Correlations among A, k, and u₀ from the Richards function were also modest (-0.60 to 0.27), but the correlation between k and u_I was 0.82. Selection to modify the Richards parameters would therefore be more challenging, and the Richards function likely over-parameterized the growth curve. We therefore concluded that the Brody function was the most appropriate growth function to describe BW changes from birth to 1 year of age in Muzaffarnagari lambs.

2,611 只 Muzaffarnagari 羔羊在出生时和 3、6、9 和 12 个月大时的体重 (BW) 用于比较五种替代生长曲线。四个三参数函数（Brody、von Bertalanffy、Gompertz 和 Logistic）和四参数理查兹函数适用于每只羔羊。估计每个函数的渐近最终 BW (A)、成熟率参数 (k) 和出生成熟度 (u ₀ ) = BW/A。形状参数 (m) 包含在理查兹函数中，用于确定生长曲线 (u _I)拐点处的成熟度 (u)）。在三参数函数中，Brody 函数在所有羔羊中具有最小的合并残差平方和 (RSS)，对于 56% 的单个羔羊具有最小的 RSS。对于 Brody 函数，生长速度在出生时最大，随着动物年龄的增长而不断下降。与 Brody 函数相比，使用可变拐点拟合 Richards 函数并没有显着降低 RSS。Brody 和 Richards 函数的比较表明，对于 17% 的羔羊，Richards 函数收敛为 Brody 函数。对于 Richards 函数，预测增长率在平均 u _I为 0.26 和平均 u _{0 时最大} = 0.10 对于 Brody 函数。参数 k 和 m 相互作用以定义 Richards 函数中的成熟率，并建议使用 u= 0.50 (t ₅₀ )的预测年龄来衡量生长效率。Brody 和 Richards 函数的 A、u ₀和 t ₅₀估计值之间的相关性均为 0.89，证实拟合 Richards 函数的益处有限。对于 Brody 函数，A、k 和 u _{0 的}估计值之间的相关性不大（-0.59 到 0.39）。在选择中使用这些参数估计来修改增长曲线将相对简单。来自理查兹函数的A、k 和 u ₀之间的相关性也很小（-0.60 到 0.27），但 k 和 u _I之间的相关性是 0.82。因此，选择修改理查兹参数将更具挑战性，并且理查兹函数可能会过度参数化增长曲线。因此，我们得出结论，Brody 函数是描述 Muzaffarnagari 羔羊从出生到 1 岁体重变化的最合适的生长函数。