Modeling the pattern of udder growth During Pregnancy and lactation in three Nigerian Goat Breeds

Abstract

Linear, quadratic and exponential regression equations were used to model the pattern of udder growth during pregnancy while Wood’s, modified Wood’s, inverse polynomial regression and polynomial regression equations were adopted during lactation using descriptors such as udder length (UL), udder width (UW) and udder circumference (UC) in West African Dwarf (WAD), Red Sokoto (RS) and Sahel breeds of goats in Nigeria. UC and UW were found to be the best descriptors of udder growth during pregnancy and lactation respectively in the three breeds. The quadratic and polynomial regression equations best fitted data from the three breeds of goats during pregnancy and lactation respectively. The equations during pregnancy were: UC = 22.0 – 0.0384X +  0.0005X², R² = 0.97 (for WAD); UC =  26.5 – 0.0402X + 0.0006X², R² = 0.96 (for RS); UC =  33.1– 0.0286X + 0.0004X², R² = 0.98 (for Sahel), while the equations during lactation were: UW = 1.2 + 9.5X – 0.2X² – 3.5logX – 11.6 (logX)², R² = 0.90 (for WAD); UW = 4.2 + 7.6X – 0.2X² – 4.4logX – 8.6(logX)², R² = 0.97 (for RS) and UW = 4.6 + 8.5X – 0.2X² – 5.0logX – 9.2(logX)², R² = 0.95 (for Sahel). During pregnancy, data from Red Sokoto does were best fitted by the linear, quadratic and exponential equations (R² = 0.82), the R² value being 1% higher than that of WAD and Sahel does. During lactation, data from Sahel does were best fitted by the Wood’s, modified Wood’s, inverse polynomial regression and polynomial regression equations (R² = 0.92) with 13% and 1% higher R² values than WAD and RS respectively. In essence, UC and UW could preferably describe the pattern of udder growth during pregnancy and lactation respectively, while quadratic and polynomial regression equations could be used preferably to model the pattern of udder growth during pregnancy and lactation respectively.