University of Khartoum

Statistical Analysis of Dairy Records of Holstein Friesians Under Khartoum, Sudan Conditions

Statistical Analysis of Dairy Records of Holstein Friesians Under Khartoum, Sudan Conditions

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Title: Statistical Analysis of Dairy Records of Holstein Friesians Under Khartoum, Sudan Conditions
Author: Alkhider, Sara Omer Ibrahim
Abstract: This study was conducted to investigate the reproductive and productive performance and to estimate some genetic parameters of these traits in Holstein-Friesian cattle at Dairy Land Farm in Sudan. The data used covered the period of eighteen years (1984-2002); it comprised 47 sires and 720 cows with 2400 records extended from first to fifth lactation. The data were classified into three groups and each of which was classified into 3 periods, group I based on the year of calving (Period 1: 1984-1989, period 2 :1990-1995 and period 3: 1996-2002); group II according to the year of birth of the cow (Period 1: 1982-1985, period 2: 1986-1989 and period 3: 1990-1993), group III was classified according to the month of birth of the cow and the time it calved into three seasons (Winter, Dry summer and Wet summer). Regarding to parity number, the data were classified into five groups, which extended from the first to fifth lactation. The data were statistically analyzed using Harvey’s least- squares computer programme (1990). Least squares means, standard errors and coefficients of variation of the reproductive and productive traits were computed. The heritabilities and correlations (phenotypic, genetic and environmental) were estimated. The results showed that the least squares means for age at first calving was late (29 months). Calving interval (413 days), open period (148 days) and dry period (130 days) were long. Number of services per conception was high (2). Gestation length was normal (273 days). But lactation milk yield (3055 kg), daily milk yield (11 kg) and the lifetime production (8069 kg) were low while the lactation length was close to optimal length (290 days). The sires had a highly significant (P< 0.001) effect on number of services per conception, lactation milk yield, lifetime production, age at first calving (P< 0.01) and lactation length (P< 0.05) due to genes passed from sires to daughters. Year-season of birth of cows had a highly significant (P< 0.001) effect on age at first calving, while year of birth had significant (P< 0.05) influence on lifetime production. The calving year-season had a highly significant (P< 0.001) effect on lactation milk yield, daily milk yield ,lactation length , dry period(P< 0.01) and calving interval (P< 0.05). Parity had a highly significant (P< 0.001) effect on calving interval, open period, lactation milk yield, daily milk yield ,lactation length , number of services per conception (P< 0.01) and on dry period(P< 0.05). The heritability estimates of reproductive traits were found to be very low, which indicates that most of the variation in these traits was due to environmental causes. Also the heritability of productive traits were low, this is probably a result of the artificial selection of the herds under study. The genetic correlations was 0.185 between age at first calving and lifetime production, -0.265 between calving interval and lactation milk yield and -0.004 between age at first calving and open period while phenotypic correlations between the same traits were -0.001, 0.035 and 0.019, respectively and the environmental correlations between the same traits were 0.009, 0.067 and 0.02, respectively. The study concluded that the performance of Holstein-Friesians was below their performance in temperate regions which probably reflects differences in the environment and levels of management. Apparently, 50% crossbreds can perform similarly or better in tropical regions.
URI: http://khartoumspace.uofk.edu/123456789/25543


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