A project that seeks to understand the long-term impact of retaining lambs from a hogget as replacements is underway.
The Massey University and Beef + Lamb New Zealand-led research project will follow the lifetime performance of single and twin ewe lambs born in 2017 from a hogget mating. These lambs were then mated as hoggets.
Professor Hugh Blair is spearheading the project, which is taking place at Massey University’s Keeble Farm near the Manawatu campus.
This project, which will finish in early 2023, has two objectives:
- To demonstrate that you can breed both single and twin lambs born to hoggets as ewe lambs and that their lifetime performance will be similar to ewe lambs born to mixed-age ewes. According to the bodies, farmers could also benefit from improved genetic gain generated from a younger ewe flock;
- Determine whether ewe lambs grown to heavy pre-mating weights achieve heavier mature weights and what this means for ewe efficiency.
These groups are:
- Twin lambs born to mixed-age dams and grown to 48kg by their first mating (the fast group);
- Twin lambs born to mixed-age dams and grown to 44kg by mating (the control group);
- Single lambs born to hogget dams;
- Twin-born lambs born to hogget dams.
How they are conducting the trial
They identified all lambs in the trial and weighed them at birth. They gave supplementary feeding to a ‘fast’ group of ewe lambs to meet the 48kg target mating weight.
They combined all lambs into one mob at eight months old for mating simultaneously and to the same ram team.
They repeated the cycle over four years, with all lambs weaned in either December or early January, with all groups being farmed as one mob except at lambing.
The variables they measure annually include:
- The number of lambs born and weaned to each group;
- Ewe liveweight and Body Condition Score (BCS) at weaning;
- Percentages of lambs born and weaned;
- Lamb survival to birth;
- Lamb birth weight;
- Lamb weaning weight.
In his most recent project report, Professor Blair stresses that because this is a lifetime study, data will not be fully analysed until the end of the project in February next year.
However, Blair says findings look “encouraging”, particularly around potential efficiency gains.
As four and a half-year-olds, the ewe’s retained from the hoggets (and themselves mated as hoggets) remained lighter than the control groups, particularly the twins who were about 7kg lighter.
However, the bodies say that this lack of size does not appear to have hindered reproductive performance.
Furthermore, they found no differences in BCS between the four groups at weaning in December. Besides, ll groups recorded similar weaning rates (135-147%) and weaning weights (30.48 to 32.2kg).
The report notes that it was encouraging that the ewes born as twins from hoggets weaned a similar proportion of lambs to the control group even with their liveweight handicap.
Twin lambs from hoggets
The project builds on previous research Massey University carried out. It demonstrated that while twin lambs from hoggets were smaller at birth, they produced the same weight of lamb weaned as ewes from mixed-age dams.
This hinted at potential efficiency gains, but unlike this project, those trials did not mate ewe lamb off-spring until they were eighteen-months-old.
According to those involved, the important part of this trial is to determine whether there is potentially an optimal pre-mating growth strategy for ewe lambs, so they do not grow out to be excessively heavy mature ewes while still achieving good hogget breeding performance.
This part of the project, they said, will show whether very heavy ewe lambs at breeding have heavier mature weights.
If they do, they will utilise this data determine what impact this heavier mature weight has on ewe production efficiency.
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