The INZAC Flock - Update May 2020

The Ireland New Zealand across breed animal comparison study (INZAC flock) aims to o validate the Irish maternal (Replacement) genetic sheep index and to compare Irish versus New Zealand genetically elite animals. Fiona McGovern and Henry Walsh give an update on the flock.

The Ireland New Zealand Animal Comparison (INZAC) flock is based at Teagasc Athenry. There are 180 ewes involved in the study. These are split into three groups of 60 comprising of Irish and New Zealand animals of high genetic merit and low genetic merit Irish animals.All Irish animals are ranked on the Sheep Ireland replacement genetic sheep index and are classified as five star (high genetic merit), representing the top 20% of animals within each specific breed, or one star (low genetic merit) representing the bottom 20% of animals within that breed. Each group contains two breed types namely Suffolk and Texel. All animals are pedigree and bred within breed type. Ewes began lambing on February 24^th this year and had a mean lambing date of March 6^th. Birth weights across the three groups were on average 5.2kg. This differed depending on litter size with single lambs weighing on average 1.6kg heavier at birth than those born as triplets and quadruplets.  All lambs are weighed at 40d of age with ewe weights and BCS collected at this time too. Our lambs are now 11weeks old on average and there 10 week / 70d weights were collected on May 14^th.  In line with results from previous years High Irish and New Zealand lambs are heaviest on average with weights of 27.9 and 27 kg, respectively. Low genetic merit Irish lambs have average weights of 25.6 kg with growth rates of 293g/day compared to 326 and 317g per day for the High Irish and New Zealand lambs. Lambs are weaned at approximately 100 days of age.

Each group is managed separately in a grass based system, stocked at 12 ewes /ha. Animals are currently in their third grazing rotation with 60% of each farmlet having being removed as silage and/or surplus grass. Our aim is to graze covers of 1,100kg DM/ha with paddocks split using temporary fencing to ensure optimum grass utilisation by reducing residency time per grazing paddock. After weaning a leader follower grazing system is operated with lambs grazing ahead of the ewes, ensuring that they are offered the best quality grass. Carrying out weekly grass measuring and using Pasturebase Ireland allows us to assess grass growth on the farm, make timely grazing management decisions and ensure that lambs are offered the best quality grass available. Lambs will be weighed once every fortnight post-weaning and drafted when they reach their target pre-slaughter drafting weight. To date this year all lambs have received a white drench for Nematodirus at eight weeks of age. From six weeks of age lambs are weighed fortnight and faecal samples are also collected to monitor the worm burden. Samples are analysed using the FECPAK technique and animals will be dosed depending on these results. In order to prevent lameness issues from arising and to treat any incidences of scald which may be present ewes and lambs are put through the footbath each time they are in the handling unit.