Synlait Milk dropped 2.2 per cent to $9.81.
New Zealand shares dropped in light trading, with A2 Milk Co and Synlait Milk leading the index lower, while Pushpay Holdings and Fletcher Building gained.
The S&P/NZX50 Index fell 19.6 points, or 0.2 per cent, to 8,303.62. Within the index, 25 stocks rose, 15 fell and 10 were unchanged. Turnover was $84 million.
"We've certainly got that school holiday feel, it's very sluggish," said Peter McIntyre, investment adviser at Craigs Investment Partners.
"We got mixed messages from Friday's close in the US - the pointer to the market is where US 10-year Treasury notes got to and it's sitting at 2.9738 as I speak. The watermark is 3 per cent, that's what a number of analysts and market commentators have consistently looked at as a signal for the market to become weaker or have some more volatility.
"Even though futures are lining up okay, I think that's going to weigh on the minds of investors in the US, and that will impact on us potentially later in the week."
A2 Milk led the index lower, dropping 3.1 per cent to $12.37.
"It's following its trading pattern in Australia too, on light volume for A2," McIntyre said.
"It's been bouncing around ever since Nestle said they'd be competitors in that Chinese market, there's a bit of nervousness about competition despite A2 wanting to expand into other Asian markets."
Synlait Milk, which supplies A2, dropped 2.2 per cent to $9.81.
Vector fell 1.2 per cent to $3.20, Air New Zealand dropped 1.2 per cent to $3.25, and Mainfreight declined 1.2 per cent to $24.01.
Pushpay Holdings was the best performer, up 2.5 per cent to $4.10, while Westpac Banking Corp rose 1.6 per cent to $30.86.
New Zealand Refining gained 1.3 per cent to $2.36.
At the company's annual meeting in Auckland this afternoon, chief executive Sjoerd Post said the failure of the pipeline between the plant at Marsden Point and Auckland in September 2017 had a net impact on profit of $8.2m.
At the end of February, the company declared a 66 per cent increase in net profit for the year to December 31 to $78.5m, driven by historically high average refining margins of US$8.02 per barrel of oil processed.
"They acknowledged the difficulties they've had, but also pointed out that going forward the margins should be quite wide," McIntyre said.
"What's going to keep the market interesting over the next while is annual meetings where CEOs can flesh out results or put them in plain language for shareholders. Typically we've seen some good positive movements post these meetings in the past."
Fletcher Building rose 0.8 per cent to $6.20. Last week, it completed the institutional entitlement offer and shortfall bookbuild component of its capital raising plan, reaping $515m of $750m target. Institutions paid $6.15 in the bookbuild - above the deeply discounted offer itself at $4.80. The retail entitlement offer opened today.
"The market will be pretty pleased they're trading above $6, to be honest," McIntyre said.
"There's still some uncertainty about the US private placement holders, they're tending to raise enough capital to make sure that's not going to be an issue though. Some of the infrastructure segment is still facing risks and they're still reporting a nil margin, and some of their outstanding work, there's still uncertainty, so in all likelihood there's potential for further write downs from here, but we've seen enough interest from institutional investors on a value basis."
Precinct Properties gained 0.4 per cent to $1.26. It has sold Deloitte House in Wellington for $10.2m and says it's entered into a period of exclusivity with one potential buyer for its stake in the ANZ Centre in Auckland.