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. 2025 Mar 14;57(2):116.
doi: 10.1007/s11250-025-04365-z.

Evaluation of empirical and mechanistic models and sampling intervals to model the lactation curves of F1 dairy sheep

Lilian Guevara  1 , Nicolas Lopez-Villalobos  2 , Geoffrey Ernest Pollott  3 , Benito Albarrán-Portillo  4 , Alberto Magno Fernandes  1 , Jesús Armando Salinas-Martínez  5 , Juan Carlos Angeles-Hernandez  6
Affiliations

Evaluation of empirical and mechanistic models and sampling intervals to model the lactation curves of F1 dairy sheep

Lilian Guevara et al. Trop Anim Health Prod. .

Abstract

Recently Latin American countries have developed a dairy sheep industry with an increasing number of specialized dairy-sheep flocks. The objective of this study was to evaluate the goodness of fit of empirical and mechanistic models and sampling interval to model the lactation curve of F1 dairy sheep with different shape of lactation curves in an intensively managed flock of the central highlands of Mexico. A total of 4,494 weekly (7D) test day records (TDR) from 156 lactations were analyzed. Three datasets were generated from the original 7D data set, setting TDR at different sampling intervals: 14 (14D), 21 (21D) and 28 (28D) days. Lactation curves were fitted using two empirical (Wood and Wilmink) and two mechanistic models (Dijkstra and Pollott). The parameters of the empirical and mechanistic models were estimated using the iterative non-linear curve fitting procedure in R. The results showed that the estimation of TMY was not affected by the sampling interval. However, the estimation of peak yield (PY) and day at peak yield (TPY) was affected by sampling interval (P < 0.05), with better estimates for 7D and 14D. Estimates of PY and TPY differed between the empirical and mechanistic models with both methods failing to estimate PY and TPY in atypical curves. The Dijkstra model showed the best fit for typical curves and the Pollott model for atypical curves in all the sampling intervals evaluated.

Keywords: Dairy ewe; Lactation curve; Mathematical modeling; Milk recording.

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Conflict of interest statement

Declarations. Statement of animal rights: The authors declare that production records were used, so the Statement of Animal Rights is not required. Conflicts of interest: The authors declare no conflict of interest.

Figures

Fig. 1
Fig. 1
Typical and atypical dairy sheep lactation curves fitted using empirical (Wood and Wilmink) and mechanistic (Dijkstra and Pollott) models
Fig. 2
Fig. 2
Pirate plots of actual and estimated total milk yield (L) by sampling interval, shape of lactation curve and mathematical model applied to F1 dairy sheep lactations
Fig. 3
Fig. 3
Correlogram between actual and estimated total milk yield (TMY), peak yield (PY) and time to peak yield by the Pollott model according to sampling interval (7, 14, 21, 28 days) of F1 dairy sheep. Actual values of total milk yield actual (TMYa), peak yield (PYa) and time to peak yield (TPY) and estimated from different sampling intervals (7, 14, 21 and 28 days)
See this image and copyright information in PMC

References

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