Adediran, S.A., Roche, J.R., Donaghy, D.J., Rawnsley, R., Freeman, M., Nish, P., and Malau-Aduli, A.E.O. (2007) Predictive characteristics of lactation models for pasture-based Holstein Friesian dairy cows. In: Proceedings of the Dairy Science Symposium. pp. 423-430. From: 3rd Dairy Science Symposium: meeting the challenges for pasture-based dairying, 18-20 September 2007, Melbourne, VIC, Australia.

PDF (Published Version) - Published Version Restricted to Repository staff only

Abstract

Mathematical functions to describe a series of milk test day records have the advantage of minimizing random variation, while simultaneously summarizing the lactation profile. Five empirical functions and two mechanistic models were used to model herd and individual milk yield profiles of multiparous Holstein-Friesian cows on 113, 290 milk yield records (8438 lactations) collected from 1994-2005. The models tested were the incomplete gamma (IG), a modified gamma (MG), an exponential (EXP), a polynomial regression (PR), a mixed log (ML), the bi-compartmental (BC), and Dijkstra (DJ) functions. Each model was fitted using the non-linear (NLIN) function of SAS. Model accuracy was evaluated based on mean square error (RMSE), the magnitude and distribution of residuals, and the correlation between the observed and predicted values. All the models did equally well in portraying the lactation profile. The residuals were generally random, except with MG. Parameter estimates were significant (P<0.05), with large serial correlations indicating biased predictions, during mid-lactation. Correlations of residuals and observed herd average lactations ranged between -0.13 (MG) to 0.19 (IG), while that between observed and predicted was between 0.76 and 0.99 for the same models. Lactation curves of individual cow milk yields were more varied, exhibited the tendency for a second peak which were not accurately modeled. The PR model fitted best, while the MG model fitted the profile least accurately in this study.

Item ID:	48672
Item Type:	Conference Item (Research - E1)
Keywords:	model, lactation profile
Date Deposited:	11 Dec 2018 02:00
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0702 Animal Production > 070201 Animal Breeding @ 100%
SEO Codes:	83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8303 Livestock Raising > 830302 Dairy Cattle @ 100%
Downloads:	Total: 1
	More Statistics