Analyses of variance were conducted on first lactation milk, fat and protein production records in England and Wales of daughters of British Friesian sires. Herds were split on milk yield into high and low levels of mean production and, in subsequent analyses, into high and low levels of within herd variance and coefficient of variation using all first lactation records. Data were then extracted on daughters of 798 young sires undergoing progeny test and on 118 widely used proven sires to generate connections. Least squares analyses were conducted within levels and genetic correlations estimated from the covariance of sire effects.W ith data split on mean yield, the heritability of milk yield was 0-24 at the low level and 0-30 at the high level, that of log transformed yield being 0-25 and 0-35 respectively. With data split on variance the corresponding figures were 0-24, 0-30, 0-27 and 0-36 respectively, and when split on coefficient of variation, 0-22,0-26,0-26 and 0-32. There were similar increases for fat and protein yield, proportionately smaller increases for fat and protein content.Genetic correlations were close to 1-0 between high and low levels for all traits on all criteria of data splitting. As a consequence progeny testing of bulls is rather more accurate at high mean or variance of production levels and data can be combined optimally without scaling. Cows of the highest predicted value using an index will be found in high variance herds.

Data from the Butana herd of Atbara Livestock Research Station were analyzed for the period 1949 -1999. The least squares means for age at first calving, calving interval, milk yield per lactation, daily milk yield, lactation length and dry period were 45.05 ± 3.56 months, 382.38 ± 8.30 days, 1662.57 ± 108.96 kg, 6.10 ± 0.40 kg, 268.17 ± 5.56 days and 119.10 ± 8.30 days, respectively. The analysis of variance revealed that the sire and parity number influenced the studied traits, while year-season of calving influenced the milk yield per lactation, daily milk yield and lactation length. Linear and quadratic regressions on lactation length significantly influenced milk yield per lactation and daily milk yield. Heritability estimates for age at first calving, calving interval, milk yield per lactation, daily milk yield, lactation length and dry period were 0.19 ± 0.07, 0.09 ± 0.03, 0.26 ± 0.06, 0.27 ± 0.07, 0.04 ± 0.02, and 0.09 ± 0.03, respectively. This study highlighted the importance of conserving the indigenous dairy cattle breeds for future generations. The presence of significant variation and the corresponding heritability estimates give promise of reasonable genetic improvement under selective breeding with respect to milk yield characters.

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Abstract. The data obtained from the dairy herd of the Arab Company for Agricultural Production and Processing (ACAPP) in a semi arid area 40 km south of Khartoum involved 337 cows with a total of 1049 records from 16 years between 1986 and 2002. The least squares means for age at first calving, calving interval, days open, lactation milk yield, daily milk yield, lactation length and dry period were 29.76±0.40 months, 433.12 ± 6.70 days, 167.79±7.08 days, 3475.53±78.89 kg, 12.29±0.28 kg, 294.10±3.62 days and 164.08 ± 6.70 days, respectively. The analysis of variance showed that the parity number had significant (p<0.05) influences on all studied traits, while year-season of calving influenced (p<0.05) age at first calving, milk yield per lactation and daily milk yield. The sire of cow influenced (p<0.05) lactation yield, daily yield, lactation length and days open. The effects of linear and quadratic regressions of both lactation yield and daily yield on length of lactation were also highly significant (p<0.01). Heritability estimates of age at first calving, calving interval, milk yield per lactation, daily milk yield, lactation length and dry period were generally low (0.098±0.104, 0.047±0.046, 0.130±0.042, 0.123±0.041, 0.172±0.062 and 0.044±0.031, respectively) except the heritability of days open which was 0.51±0.37. The productivity of the herd in this study which averaged 12.3 kg/cow/day was much lower than the expected productivity of Holstein Friesian cows, which reflects the negative impact of the prevalent environment in the Sudan. More records and economic data are required to examine the economic feasibility of raising pure Friesians under Sudan conditions.

Data from Zebu x Friesian crossbred dairy cows of different upgrading kept in the Kenana Sugar Company (KSC) farm, 300 km south of Khartoum on the bank of the White Nile in the low rainfall savannah region were collected over a period from 1984 to 2004 and analyzed using Harvey's (1990) Least Squares programme. The results indicated that there were no significant differences in milk yield per lactation, daily milk yield and lactation between the 25% and 37.5% genetic groups. The 50% Zebu x Friesian group produced significantly more milk per lactation (2721.10 ± 87.36 kg) compared to the 25% and 37.5% groups (2067.20 ± 241.62 and 2192.68 ± 122.66, respectively). The milk yield per lactation and daily milk yield of the 50, 62.5, 75 and 87.5% breed groups was not significantly different. There were no significant differences in length of lactation between the 25%, 37.5% and the 50% group (267.99±18.14, 273.11±9.25 and 278.75±6.52, respectively). Groups with 75% and 87.5% of Friesian blood proportion had significantly longer lactation days (305.09 ±10.63 and 347.07 ±30.14, respectively). The range for dry period was between 78.37±12.27 days for the 75% genetic group to 92.56±16.76 days for the 25% group. The mean calving intervals for the five genetic groups ranged from 367.85±21.38 days for the 75% group to 394.60±16.33 days for the 50% group. The earliest age at calving (41.56±2.16 months) was achieved by the 37.5% group while the latest age at first calving (49.01±1.29 months) was recorded for the 62.5 % group. The results of this study and other similar studies in tropical countries provide proof that the local environment (i.e. high temperature, low feed quality and quantity, disease and parasitic loads) can sustain composite genotypes of up to 50% B. taurus blood and does not lead to significant yield increases in upgraded groups. The economic feasibility of raising crossbred cows (Zebu x Bos taurus) under the Sudan condition has to be further evaluated in comparison with native dairy breeds to determine the overall efficiency and economic benefits. Es konnten keine signifikanten Unterschiede der Laktationsleistung, der täglichen Milchleistung und der Laktationslänge bei Kühen mit einem 25 % und 37,5 % Holstein-Friesian-Anteil gefunden werden. Die F1 50 % Zebu x HF hatten eine signifikant höhere Milchleistung (2721 ± 87 kg) im Vergleich zu den genetischen Gruppen 25 % und 37,5 % mit jeweils 2067 ± 241 und 2192 ± 123 kg. Die Laktationsleistung und die tägliche Milchleistung der genetischen Gruppen 50 %, 62,5 %, 75 % und 87,5 % waren nicht signifikant unterschiedlich. Auch gab es keine signifikanten Unterschiede in der Laktationslänge zwischen den Kreuzungsgruppen mit 25 %, 37,5 % und 50 % HF-Anteil (268 ±18; 273 ± 9 und 279 ± 6) während die Kreuzungsgruppen mit 75 % und 87,5 % HF-Anteil eine signifikant längere Laktation aufwiesen (305 ± 11 und 347 ± 30). Die Trockenperiode schwankte zwischen 78 Tagen für die 75 % HF-Gruppe und 92 Tagen für die 25 % HF-Gruppe.