Lactation and Function of Curve Parameters in Yankasa Sheep

  • Afolayan, R.A. (National Animal Production Research Institute, Ahmadu Bello University) ;
  • Abubakar, B.Y. (National Animal Production Research Institute, Ahmadu Bello University) ;
  • Osinowo, O.A. (Federal University of Agriculture, College of Animal Production) ;
  • Dim, N.I. (Department of Animal Science, Ahmadu Bello University)
  • Received : 2001.06.28
  • Accepted : 2002.01.14
  • Published : 2002.06.01


The accuracy of the gamma function to describe lactation curve of Yankasa ewes was investigated using milk production data obtained from 168 ewes with either complete or incomplete 84 day lactation records. Ewes were daily hand milked after over-night separation from lamb and thorough disinfection of the udder. The daily milk yield on the average was estimated from the weekly total yield. The effect of type of birth, parity, season of birth and lactation length on the components of lactation curve (a, b, c and s) were analysed by least-square procedures. All factors except parity significantly (p<0.01) influenced the curve parameters. The goodness of fit of the function did not differ between the two classes of varying duration of lactation; incomplete lactation however, showed a lower persistency and as expected lower level of production. Correlations ($r_p$) between lamb weight gain and milk yield using the weight records from lamb weighed at weekly intervals indicated a high and positive relationship in the early lactation that decreased in intensity as the lactation advanced.


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