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Responses in lactose yield, lactose percentage and protein-to-protein-plus-lactose ratio from index selection in New Zealand dairy cattle
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2016-03-16
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NW Sneddon, N Lopez-Villalobos, SR Davis, RE Hickson, L Shalloo, DJ Garrick & U Geary (2016) Responses in lactose yield, lactose percentage and protein-to-protein-plus-lactose ratio from index selection in New Zealand dairy cattle, New Zealand Journal of Agricultural Research, 59:1, 90-105, DOI: 10.1080/00288233.2015.1131724
Abstract
The breeding goal of the New Zealand dairy industry is to improve
the genetic capability of cows to convert pasture-based feed into
farmer profit. The New Zealand dairy industry exports over 95% of
milk produced and the most significant product by export volume
is whole milk powder (WMP). The current selection objective,
breeding worth (BW), will increase yields of protein and fat,
potentially shifting milk composition further from the ideal
composition for making WMP. This study aimed to investigate the
correlated responses in lactose yield (LY), lactose percentage (LP)
and protein-to-protein-plus-lactose ratio (P:P + L) from selection
for BW, BW plus LY, BW plus LP and BW plus P:P + L. Selection for
BW is predicted to have per-cow responses of 54.92 kg milk/year,
2.22 kg fat/year, 1.78 kg protein/year and 2.84 kg lactose/year.
When lactose was included in the selection objective in the form
of LY, LP or P:P + L, genetic responses ranged from −59.98 kg to
61.08 kg milk/year and from −2.67 kg to 3.70 kg lactose/year. The
industry could reduce imported lactose requirements per tonne of
WMP by 6%–11% by including lactose into the selection objective,
compared with selection on BW alone.