Characterization of the Lactation Curve in Shami Cows
Characterization of the Lactation Curve in Shami Cows
Mohamed Attia Ahmed Awad1*, Obaida Abdel Kareem Almasri2, Mohamed Abd El-Aziz Mohamed Ibrahim1, Rabie Ragab Sadek1, Samy Abou-Bakr1
ABSTRACT
Abstract | The objectives of this study were to estimate the lactation curve parameters, describe the shape of the lactation curve of Shami cows using Wood’s incomplete gamma function, and demonstrate the effect of environmental factors on the pattern of the lactation curve. A total number of 1533 weekly test-day records were collected on 584 Shami cows during the period from 1983 to 2012, at Deir Al-Hajar station belonging to the Ministry of Agriculture and Land Reclamation, Syria. Data were analyzed using the General Linear Model applied in XLSTATE software. The least squares means for the lactation curve parameters were 9.7 ± 0.12 kg for the initial milk yield (a), 0.40 ± 0.01 kg/week for the rate of increase to the peak (b), and 0.09 ± 0.001 kg/week for the rate of decline from the peak to dried off (c). The least squares means for the peak milk yield (PMY), peak week (PW), and persistency of lactation (P %) were 12.1 ± 0.11 kg, 4.5 ± 0.07 weeks, and 43.8 ± 1.11 %, respectively. The effect of parity on “a”, PMY, and PW was significant (P < 0.01). Season of calving affected significantly only on PMY and P % (P < 0.05). The effect of the period of calving was significant on all studied traits. It could be concluded that Wood’s incomplete gamma function was adequate to characterize the shape of the lactation curve for Shami cows and the shape of the lactation curve of Syrian Shami cows in the current study followed the ideal shape of other cattle breeds.
Keywords | Incomplete gamma function, Lactation curve parameters, Milk yield, Persistency, Shami cows
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April 2022
Vol. 10, Iss. 4, Pages 712-954
