Relationships between live weight and herd-test traits in a Saanen goat herd in New Zealand

Genetic relationships among doe live weight and herd-test milk traits were investigated in a large herd of Saanen goats, managed with seasonal (spring) kidding and twice-daily milking. There were 34,183 herd-test records of milk solids yield (FPL) for 20 milking seasons to 2010-2011, with individual fat (F), protein (P) and lactose (L) yields in later seasons, somatic cell count (SCC) from 1999-2000 onwards (26,575 records), and weights recorded on four dates between June 2008 and November 2010 (4358 records). FPL, log(10)SCC and live weight were analysed using restricted maximum likelihood, with a repeated-animal model and full relationship matrix, yielding heritability estimates of 0.35 +/- 0.02, 0.20 +/- 0.02 and 0.64 +/- 0.04 respectively and repeatabilities of 0.48 +/- 0.01, 0.37 +/- 0.01 and 0.80 +/- 0.01 respectively. Genetic correlation estimates were 0.41 +/- 0.06 (FPL, live weight), -0.07 +/- 0.06 (FPL, log(10)SCC) and 0.24 +/- 0.08 (live weight, log(10)SCC). Expected correlated changes in doe live weight will depend on the selection index weights applied to doe weights and the other traits.