Making the best use of scanning data

• Published date: 22 June 2022
• Publication title: Central Rural Life

In a Beef + Lamb New Zealand Scene + Herd podcast, Massey University’s Professor Paul Kenyon outlines how pregnancy scanning data can be used to maximise ewe and lamb survival

He says scanning should be carried out a minimum of 45 days after the ram has been removed. After 100 days it is difficult for the scanner to determine how many lambs each ewe is carrying.

Scanners can identify singles, twins, triplets (or just multiples) and early- and late-lambing ewes. This information enables farmers to strategically feed and manage ewes to maximise both ewe and lamb survival and pre-weaning lamb growth rates.

Scanning is also an ideal time to body condition score each ewe as she is moved into the scanning crate.

Prof Kenyon points out that for multiple-bearing ewes, there is only a small window when body condition can be increased. After that, it becomes physically impossible for her to gain condition because of the demands of pregnancy.

‘‘Grazing herbage, most twin- and triplet-bearing ewes cannot physically eat enough to meet their theoretical requirements, so the ewe needs to use her fat and she needs to have some fat to use.’’

In the last 30 to 40 days of pregnancy the foetus grows rapidly, so in a triplet-bearing ewe, the total pregnancy weight (foetus and placenta) at the point of lambing is 20kg–22kg. A ewe cannot eat enough feed to sustain her metabolic needs in late pregnancy, which is why triplet lambs are typically small, thin and lack vigour.

‘‘This is why feeding in early- to mid-pregnancy is so vital.’’

On day 120 after the ram has gone out, some ewes will be 120 days pregnant and some will be 69 days pregnant, and their nutritional needs will be very different.

‘‘So why feed them the same?’’ Prof Kenyon asks.

He says knowing how many lambs a ewe is carrying can also inform the selection of lambing paddocks based on shelter and topography. Shelter is a critical factor in multiple lamb survivability and a gradient of more than 30 degrees will significantly increase the chance of separation in multiples so should be avoided.

Identifying...