A Study of the Effect of Season of Calving, Stage of lactation on Grade Cows on the University Farm.

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Kamal EL Hassan, El abid
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The influence of upgrading, stage of lactation, season of calving and age of the animal on milk yield and composition (Protein, fat, solid-not-fat, total solids and ash) was studied in the crossbred dairy herd of the University of Khartoum farm. The average daily milk yield shows an upward trend with the increase of Friesian inheritance up to 62.5% Twenty five percent Friesian inheritance cows daily yield was significantly lower than 50% and 62.5% daily yield while 50% and 62.5% daily yield showed no significant difference. Friesian inheritance did not significantly affect milk constituents. Milk yield decreased with the advancement of lactation while milk constituents increased. Winter calvers were better yielders with poor milk constituents, while summer calvers were low yielders with rich milk constituents. The age of the animal in terms of lactations was found to have a significant effect on milk yield and solid-not-fat content of the milk and it had no significant effect on protein, fat and total solids content of the milk. Maximum milk yield was reached in the fifth lactation, while the richest milk was produced in the second lactation.
Season,Calving, Stage of lactation,Grade Cows,University Farm.