Ultrasound to test pregnancy in sheep

Waimarino Bulletin, Volume 2, Issue 5, 3 July 1984, Page 11

Ultrasound to test pregnancy in sheep

A new ultrasound machine will have a number of important applications on Limestone Downs, a 3219 hectare sheep and beef cattle property in the Waikato. It has been purchased by the C. Alma Baker Trust which administers the property for the furtherarice of agricultural science, education and other charitable purposes. The portable machine is the same as those used in hospitals for soft tissue diagnosis. On Limestone Downs, it will be used to diagnose pregnancy in sheep. It is expected to have considerable impact on breeding and feed management programmes. The possibilities for sheep breeding are of particular interest to staff of the Animal Science Department at Massey University. The Limestone Downs Administration, which comprises representatives from the University, has sought their involvement to help determine the potential of the ultra-sound. Both farm and animal science staff are about to use the machine on Limestone Downs to screen better performing animals to go into a nucleus flock which breeds flock sires for the property.

In the past two years, the procedure has been to draft off the best looking 1,000 two tooths from a flock of about 7,000. At lambing, farm staff identify twinning ewes in this group. Last season, 300 were marked, many of which went to the nucleus flock. However, this month, all the two-tooths will be screened, enabling immediate identification of possibly 1,000 twinning ewes. The 1,000 ewes will then be further screened at lambing so that best twinning ewes can be supplied to the nucleus flock. A much greater selection differential can be achieved by including a second screening which might be on the basis of fleeceweight or four-tooth lambing performance. The machine is also.being used off the property to improve the ram breeding scheme which provides the farm with flock sires. The scheme is located on Massey University's hill country property in the Manawatu — Tuapaka Farm. A nucleus flock has been built up from a number of sources, including the University's Riverside Farm in the Wairarapa, the Lands and Survey Department, and Limestone Downs.

So far 1,200 ewes from Tuapaka 's nucleus flock have been screened so that dry and single-bearing ewes can be removed before lambing. The resulting decrease in flock size will reduce much of the recording work needed during spring when demands on labour are high. Removing ewes from a commercial flock before lambing is one of the improvements to feed management resulting from the ultrasound^ Pregnancy diagnosis will enable dry or barren sheep to be identified much earlier and not taken through the winter. An added advantage is they can be ciilled at a time when the freezing works are looking for stock. Also, if single-bearing and twin-bearing ewes are identified, it may be possible to improve feeding management by putting the groups on different pre-and post-lambing feeding regimes. A commonly held theory, which has been under investigation at Massey University's Keeble and Riverside Farms (using the DSIR x-ray machine), is that twin-bearing ewes should be run at lower stocking rates. This could reduce the incidence of starvation and exposure at lambing, improve lactation performance and obtain better lamb weights at weaning. On the other hand, higher stocking rates for singlebearing ewes could lower the incidence of dystocia. Should this theory prove correct, pregnancy diagnosis is likely to become an important commercial proposition for improving productive performance on Limestone Downs — and other sheep farms. With improving technology, the ultrasound which currently retails at $10,000 (compared to $30-40,000 three years ago), is fallirig within the means of sheep farmers and it may not be long before it becomes an important piece of farm machinery.