Mahassin A. Mohamed1, S.A. Mohamed2 and K.A. Gubartalla3
1 Shukaba Animal Production s Research Station, Wad Medani South, Sudan.
2 Department of Animal Science, Faculty of Agricultural Sciences, University of Gezira, Sudan.
3 Animal Production Research Centre, P.O. Box 1355, Kuku, Khartoum North, Sudan.
Summary
The study investigated the effect of age at first calving and calving season on the first lactation performance of 203 Butana heifers maintained at Atbara Station during (1970/2000). Heifers were grouped into early, medium and late ages at first calving- (<42; 42-48 and >48 months). Seasons were classified into hot (March /August) and moderate (September/February). Data were analysed using the computer program of SPSS.
Age group significantly affected total lactation yield, lactation length, dry period and calving interval (P<0.001). Older heifers at first calving were superior compared to the other two age groups producing 259.54kg (23.18%) more milk. However, their lactations were longer by 31.5 days (12.59%) than the youngest age group.
The dry period and calving interval of the youngest age group were 60.35 (29.92%) and 28.11 (6.67%) days longer than those of the late maturing group.
There was a significant season effect on total yield, days in milk and days dry (P<0.05).The hot season calves realized 129.92kg greater yield (12.49%) in a 14.02 days longer (5.82%) lactation, but with a correspondingly shorter dry period(17.8 days less, 9.68%) compared with the moderate season.
Age and season of calving affected the productive traits in question with the greatest yield and longest duration achieved by late maturing cows and in the hot season.
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