Singh

4. Polynomial regression function (Ali and Schaeffer,

MLF, respectively. Comparison of predicted with actual

1987)

monthly test day milk yields using different functions

have been presented in Table 3 and the overall observed

and predicted MTDMY using all the four lactation curve

functions were plotted graphically (Figure 1 to 4). The

Inthismodel,Y _t =Averagemilk yieldint th weboflactation,

figures indicated that PRF was almost of similar order

a = Associated with peak yield, b & c =Associated with the

of magnitude as the actual curve. This may be due to the

decreasing slope, d & e = Associated with the increasing

fact that this function accounted for rising and declining

slope, × = t / 305. The best fit model was identified on the

segments of the lactation curve.

basis of higher coefficient of determination (R 2 ) and lower

root mean square error (RMSE). Residuals obtained by

In the present investigation it was found that on an

these functions were plotted graphically.

average, the peak yield from all lactation curves func tions

was found to be highest in 3 rd test day (TD ₃ ) of lac tation in

RESULTS AND DISCUSSION

Murrah buffaloes. Among four models studied PRF fitted

best to the test day data followed by EF and therefore

The mean monthly test day milk yields (MTDMY)

these two functions are recommended for prediction of

increased from 5.91±0.13 kg on TD ₁ (15 th day of lactation)

MTDMYs in Murrah buffaloes.

toapeakyieldof7.41±0.12kgonTD ₃ (75 th dayoflactation)

and subsequently declined to 3.11±0.15 kg on TD ₁₀ (285 th

ACKNOWLEDGEMENTS

day of lactation). Geetha et al. (2006), Chakraborty et

al. (2010) and Patil et al . (2012) who reported the peak

The authors are immensely grateful to the Director, ICAR-

MTDMY as 7.15±0.15 kg, 8.11±0.25 kg and 8.02±0.09

National Dairy Research Institute, Karnal and Head, Dairy

kg, respectively on TD ₃ . The estimated lactation curve

Cattle Breeding Division for providing necessary facilities

parameters (a, b, c, d and e) of four lactation curve models

for conducting this study. Financial support in form of

(Table 1) were using 9071 monthly test-day milk yield

ICAR-JRF (ICAR) is duly acknowledged.

records of first lactation in Murrah buffaloes to fit into the

mathematical models and obtain the predicting equation

REFERENCES

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Journal of Animal Research: v.5 n.1. April 2015