Castillo-Gallegos Epigmenio, Marín-Mejía Bernardo de Jesús
Facultad de Medicina Veterinaria y Zootecnia. Universidad Nacional Autónoma de México, Mexico city, Mexico.
Centro de Enseñanza, Investigación y Extensión en Ganadería Tropical,Carretera Federal Martínez de la Torre a Tlapacoyan, km 5.5. Municipio de Tlapacoyan, Veracruz, CP, 93600, Mexico.
Trop Anim Health Prod. 2019 May;51(4):809-818. doi: 10.1007/s11250-018-1760-y. Epub 2019 Feb 11.
The objective of this study was to compare the fit of seven functions to cumulative daily milk yield records of grazing F1 (Holstein × Zebu) cows in a dual-purpose cattle production unit of the Mexican tropics. Fifty-seven lactations from cows that calved from 1998 to 2001 were used. The functions were quadratic without intercept, three with two segments (both segments linear, the first segment quadratic and the second linear, and both segments quadratic), and three classical growth functions (Gompertz, logistic, and Richards). The Akaike information criterion corrected (AIC) was used as criterion of fit, being the function with the best fit the one with the lowest AIC value. The best fit was for the segmented function with both segments quadratic, followed closely by the Richards function. The derivatives of these functions give the daily milk yield curve (kg/cow/day), so the former results in a straight line per segment and the latter in the usual shape of the typical lactation. However, as cumulative records produce a monotonic increasing line, neither function can distinguish a priori the presence of a lactation peak. For this reason, it is advisable to examine the common dispersion plot of daily milk yield of each cow, and if a peak is not evident, then proceed to fit the segmented function; otherwise, the function of Richards should be used. The need to study the causes for the absence of a lactation peak in tropical dual-purpose cows is highlighted.
本研究的目的是比较七种函数对墨西哥热带地区一个两用养牛场中放牧的F1（荷斯坦×泽布）奶牛累计日产奶量记录的拟合情况。使用了1998年至2001年产犊母牛的57次泌乳记录。这些函数包括无截距的二次函数、三个两段式函数（两段均为线性、第一段为二次函数第二段为线性、两段均为二次函数）以及三个经典生长函数（冈珀茨函数、逻辑斯蒂函数和理查兹函数）。采用校正后的赤池信息准则（AIC）作为拟合标准，AIC值最低的函数即为拟合最佳的函数。拟合最佳的是两段均为二次函数的分段函数，其次是理查兹函数。这些函数的导数给出日产奶量曲线（千克/头/天），因此前者每段形成一条直线，后者形成典型泌乳的常见形状。然而，由于累计记录产生一条单调递增的线，这两种函数都无法先验地区分泌乳高峰的存在。因此，建议检查每头奶牛日产奶量的常见散点图，如果高峰不明显，则采用分段函数进行拟合；否则，应使用理查兹函数。强调了研究热带两用奶牛泌乳高峰缺失原因的必要性。
