Abstract
Summary A study was made of the production records of 353 Butana cows with 1,311 calvings during the years 1943–57 in a governmental dairy farm herd on the north of Atbara, Northern Province, Sudan. Prom the performance records of this herd, it was found that (a) heifers averaged 44 months old at first calving, (b) the average interval between consecutive calvings was 416 days, and (c) the average milk yield in 253 days was 3,129 lb, with a standard deviation of 1,709 lb. The records also showed highly significant differences between all production traits at different years. No real differences were evident in milk yield records due to month of calving or age of cows in lactation. Based on reported data, repeatability estimates of single-record milk yield, calving intervals, lactation periods, and dry periods were: 0.415±0.037, 0.111±0.039, 0.415±0.043, and 0.221±0.037, respectively. Heritability of a single-record milk yield was estimated as 0.278±0.232 and of two records as 0.302±0.286. Further statistical analysis showed that the total generation length was 25.87 yr, and it is estimated that the annual genetic improvement in milk yield has amounted to about 0.7% of the herd average. Most of this improvement has been brought about by the selection of the sires used.
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