Study of the effect of some non-genetic factors on the parameters of the milk yield curve of Shami cows

Abstract

The research was carried out at the Deir Al-Hajar Research Station for the Improvement of Shami Cows affiliated to the Department of Livestock Research - General Authority for Scientific Agricultural Research, where 1420 records were collected for (71) Shami cows during the period between 2018-2020 to study the effect of some non-genetic factors on the curve parameters. Milk production of Shami cows by using an incomplete linear gamma function to estimate the parameters of the milk production curve (c, b, a). The data were subjected to a general linear model, and analysis of variance was used to determine the effect of different factors. The Duncan test was applied to compare averages using SAS (1996). The mean parameters of the curve were (2.04 kg) for function a, (0.49 kg) for function b, and (-0.06 kg) for function c, milk production peak, production peak time, and productivity stability (8.33 kg and 61.4 days, 4.8 weeks). Respectively, the total milk production is 1498 kg, and the lactation season length is 239.9 days. The mother's age at birth had a significant effect on parameter (c), the peak of production, the time of reaching the peak of production, the year of birth had a significant effect in the two parameters b and c, and the productivity stability, and the correlation analysis showed a negative significant value for parameter (a) with parameter (b), and the peak Production, productivity stability, and significant positive with the total milk production, while the parameter (b) has a positive significant value with the parameter (c), the production peak, the time of reaching the production peak, and the parameter (c) has a positive significant value with the time of reaching the peak of production, and the value of Moral negativity with the stability of productivity, and a positive positive correlation was found between the peak of production, the time of reaching the peak of production, and with the stability of productivity.