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Linear hyperbolic laction curves

Evaristo Bianchini-Sobrinho^I; Francisco A. Moura Duarte^II; Raysildo Barbosa Lobo^II

^IDepartamento de Ciências Exatas, Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESP, 14870 Jaboticabal, SP, Brasil. Send correspondence to E.B.-S.
^IIDepartamento de Genética, Faculdade de Medicina de Ribeirão Preto, USP, 14049 Ribeirão Preto, SP, Brasil

ABSTRACT

The linear hyperbolic model Y = Bo + B₁X + B2 1/X and the gamma model Y=Axbe cx were used to describe lactation curves of 553 Gyr dairy cows, considering the first three parturitions. The coefficient of determination for lactation stage means was 0.96 for both models. When the models were used individually for each cow in the herd, the linear hyperbolic model showed a slightly better fit than the gamma model. Due to the simplicity of its equation, the linear hyperbolic model can be used to advantage with respect to the gamma model for estimating total milk production of Gyr cows with incomplete records.

Keywords: hyperbolic; laction; curves.

REFERENCES

Bianchini, E.S. (1984). Estudo da curva de lactação de vacas da raça Gir. Doctoral Thesis. Faculdade de Medicina de Ribeirão Preto, USP.

Harvey, W.R. (1977). User's Guide for LSML-76: Mixed Model Least-Square and Maximum Likelihood Computer Program. Ohio State University, (mimeo), pp. 76.

Wood, P.D.P. (1967). Algebraic models of the lactation curve in cattle. Nature 216: 164-165. Wood, P.D.P. (1968). Factors affecting persistency of lactation in cattle. Nature 218: 894.

Wood, P.D.P. (1969). Factors affecting the shape of the lactation curve in cattle. Anim. Prod. 11:307-316.

Wood, P.D.P. (1970a). The relationship between the month of calving and milk production. Anim. Prod. 12: 253-259.

Wood, P.D.P. (1970b). A note on the repeatability of parameters of the lactation curve in cattle. Anim. Prod. 12: 535-538.

Wood, P.D.P. (1972). A note on seasonal fluctuations in milk production. Anim. Prod. 15:89-92.

Wood, P.D.P. (1976). Algebraic models of the lactation curves for milk, fat and protein production, with estimates of seasonal variation. Anim. Prod. 20: 35-40.