External evaluation of the predictions of body condition score change across lactation of the Herd Dynamic Milk (HDM) model

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External evaluation of the predictions of body condition score change across lactation of the Herd Dynamic Milk

(HDM) model

E. Ruelle, Luc Delaby, M. Wallace, Laurence Shalloo

To cite this version:

E. Ruelle, Luc Delaby, M. Wallace, Laurence Shalloo. External evaluation of the predictions of

body condition score change across lactation of the Herd Dynamic Milk (HDM) model. Agricultural

Research Forum 2014, Mar 2014, Tullamore, Ireland. Agricultural Research Forum, 2014, Proceedings

of the Agricultural Research Forum. �hal-01210852�

137

Table 1. Comparison between the average actual (A) and simulated (S) daily BCS of the dairy cattle for the stocking rate 3.28 ( SR1), 2.92 (SR2) and 2.51 (SR3) for the Irish multiparous and primiparous cow, and the low and high feeding of the Normande and Holstein French cow.

External evaluation of the predictions of body condition score change across lactation of the Herd Dynamic Milk (HDM) model.

Ruelle E.

, Delaby L.,

Wallace M.,

and Shalloo L.

1

Animal & Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland.

School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.

INRA, UMR 1348, PEGASE, Domaine de la Prise, 35590 Saint Gilles, France

Introduction

Predicting milk production and body condition score (BCS) change throughout lactation either in grazing or indoor feeding conditions presents a major challenge for models and modelers. Many studies have shown that BCS at calving and during lactation can have a major impact on the fertility of the cow. Therefore a model that can predict with reasonable accuracy using a daily time step BCS change of a dairy cow over a multi-year time horizon could have a significant impact on decision support at farm level.

Materials and methods

The Herd Dynamic Milk (HDM) model evaluated in this study is an agent-based dynamic model. The model simulates each animal from birth to death with a daily time step. The intake of the animal is calculated using the INRA French system (Faverdin et al., 2011) for nutrition. In this paper, the model has been tested against actual data from both France and Ireland. The model has been initialised using the actual data from both the Irish and the French experiments. Then, the outputs from the model were compared to the recorded experimental data to compare model accuracy at the herd level for both experiments. A number of statistical procedures were used to determine model accuracy which included root mean square error (RMSE) and the relative predicted error (RPE) for milk production.

The objective of the Irish study carried out in one of the Teagasc farms was to determine the impact of different stocking rates (SR) on key physical, biological and economic performances (McCarthy et al., 2013). The objective of the French experiment carried out at INRA was to evaluate over a long term time horizon, the ability of different breeds of dairy cows to produce and to reproduce under two feeding strategies (Cutullic et al., 2011). Since 2006, two breeds of dairy cows (Holstein Friesian and Normande) were evaluated under contrasting feeding strategies (high and low feeding group).

Results and Discussion

A general guide for model usefulness centres on an RPE of less than 10% (Delagarde et al., 2011). The weekly comparison of the BCS of the actual against the predicted data resulted in every RPE lower than 10%

except for the Holstein breed in the low feed scenario (10.73%) (Table 1). On farm, the recording scale for BCS is 0.25 units of BCS. With every RMSE lower than 0.25 units the model shows a good accuracy in the simulation of BCS. The RPE were higher for the French experiment in the case of the low feeding system than the high feeding system. The largest proportion of the error was observed in late lactation resulting in the model underestimating BCS and overestimating milk production of the cow. This result is probably due to a inaccurate partitioning of the energy intake in late lactation. The BCS loss was slightly overestimated by the model from 0.02 units for the low Holstein to 0.16 units for the low Normande cow on the French data. For the Irish data the model slightly underestimated the BCS loss (average of 0.1 units) except for the SR3 multiparous cows, but the prediction is accurate with all the RPE lower than 5%

at the lactation or season level.

Conclusion

The HDM model is capable of accurately simulating the BCS of dairy cows through lactation. The model has been able to simulate different breeds, parity and feeding system but further work is required in late lactation in case of underfeeding.

Acknowledgement

The authors acknowledge the financial support of the FP7 GreenHouseMilk Marie Curie project, SRUC for co-hosting and funding from the Research Stimulus Fund 2011 administered by the Department of Agriculture, Fisheries and Food (Project 11/S/132).

References

Cutullic, E., Delaby, L., Gallard, Y. & Disenhaus, C.

(2011) Animal 5:731-740

Delagarde, R., Faverdin, P., Baratte, C. & Peyraud, J.L.

(2011) Grass For. Sci. 66:45-60

Faverdin, P., Baratte, C., Delagarde, R.& Peyraud, J.L.

(2011) Grass For. Sci. 66:29-44

McCarthy, B., Delaby, L., Pierce, K.M., Brennan, A. &

Horan, B. (2013) Livest. Sci. 153:123-134

French Irish

Holstein Normande Multiparous Primiparous

High Low High Low SR1 SR2 SR3 SR1 SR2 SR3

mean A 2.45 1.83 3.31 2.69 2.82 2.88 2.97 2.95 2.98 3.05

mean S 2.28 1.66 3.14 2.48 2.79 2.84 2.94 3 3.01 3.05

RMSE 0.18 0.2 0.18 0.22 0.07 0.1 0.12 0.07 0.07 0.06

RPE 7.53 10.73 5.35 8.05 2.36 3.52 4.12 2.54 2.2 2.03