A dried up water hole in the Owyhee area.
Bureau checks by air this week found the horses gathered in two herds, neither of which were close to water.
The bureau moved in emergency water troughs and have provided 20,000 gallons of water in the hope the horses would drink, but hoofprint evidence suggests few have taken the opportunity.
US District Court judge Larry Hicks, sitting in Nevada, lifted his restraining order on Friday afternoon for the Owyhee area, after the bureau explained the dangers faced by the horses.
That afternoon, the contractor running the muster managed to bring in 54 animals, comprising 18 males, 26 mares and 10 foals.
One foal was suffering from extreme dehydration, and was humanely euthanised this morning (NZ time). The remaining 53 animals appeared to be stabilising, the bureau said.
The muster resumed at 6.30am on Saturday (early today, NZ time) and by 8.30am a further 107 wild horses had been captured.
Bureau staff, specialists and on-site US Department of Agriculture veterinarians are treating the animals, which were suffering from dehydration.
No further updates on gather numbers were available.
Bureau field staff and specialists reported on Friday that the condition of the wild horses within the Owyhee area was critical and declining rapidly.
The bureau said it continued to haul water to both herds by tankers, filling temporary troughs and a reservoir, yet only a small group had taken water, based on tracks in the mud.
The bureau said that early today it shipped 112 horses gathered when the first muster was undertaken, on Saturday last week, to more permanent facilities. Seventy-five males were transported to the Gunnison Prison Wild Horse Training Facility at the Central Utah Correctional Facility and 37 mares and foals went to the Palomino Valley Center regional adoption facility.
They were among 228 wild horses initially gathered, many of which were found to be severely dehydrated. In the days following, 13 horses died of dehydration-related complications.
The bureau has stressed that the deaths were the result of a lack of water in the immediate area occupied by the horses before they were gathered, not from the muster itself.
A 14th horse also died due to a fractured leg suffered in the temporary holding corrals.