A COMPARISON OF ALGEBRAIC MODELS TO DESCRIBE THE LACTATION CURVES IN JAFARABADI BUFFALO 3384
Loading...
Files
Date
2021-09
Authors
CHUDASAMA HARSHAL MOHANLAL
Journal Title
Journal ISSN
Volume Title
Publisher
JAU JUNAGADH
Abstract
The present investigation aims to compare the efficiency of seven Algebraic
models with respect to weekly milk yield records of Jafarabadi buffalo. The weekly
milk yield (litre) data were collected for 357 record of six lactations covering the period
from 2009 to 2018 of the Cattle Breeding Farm, Junagadh Agriculture University,
Junagadh.
The weekly milk yield records of 43 weeks for each of the six lactations and
average of all the six lactations (overall) were subjected to statistical analysis based on
seven different models viz., Inverse polynomial, Gamma type, Parabolic exponential,
Exponential, Quadratic, Quadratic cum log and model proposed by Morant and
Gnanasakthy using non-linear fitting approach.
The two criteria employed to judge the efficiency of different models were
coefficient of determination (R2) and deviation from regression sum of squares (DSS).
Apart from this, different characteristics viz., initial milk yield (litre/week), peak
milk yield (litre), time to attain peak milk yield (week), 43rd week milk yield (litre), rate
of increase (litre), rate of decrease (litre) and total milk yield (litre/lactation) were
estimated and compared with the observed data in each lactation and overall, i.e.
average of six lactations.
The Quadratic cum log model was found most efficient based on both the
criteria i.e. R2 and DSS. Next in order was Gamma model followed by Parabolic
exponential for all the six lactations and overall basis (average of six lactations).
Since both the criteria i.e. R2 and DSS were highly negatively correlated either
of them can be considered for comparing efficiency of different algebraic models.
It was also observed that the variation in coefficient of determination (R2) was
less for all the models tried in each of the lactation whereas it was comprehensive in
the case of deviation from regression sum of squares (DSS).
Various useful characteristics of lactation curve viz., initial milk yield, peak
milk yield, time to attain peak milk yield, milk yield in 43re week (last week), rising
and declining phases and total milk yield were estimated for four out of seven models,
i.e. Gamma type model, Quadratic cum log model, Quadratic model and Inverse
polynomial model. These models were compared for various characteristics based on
observed records. Inverse polynomial model, model proposed by Morant and
Gnanasakthy and Exponential models were excluded from comparison as they did not
provide logical estimates for these characteristics.
Performance of the models varied with the characteristics of milk yield of
different lactations. Gamma type model was found most efficient for time to attain peak
milk yield and rate of increase. However, Gamma model showed superiority to predict
rate of decrease. To predict initial milk yield as well as peak milk yield, Quadratic cum
log model was found superior as compared to rest of the models. Quadratic model less
efficiency to estimate various characteristics of milk yield records of Jafarabad buffalo