Farm Ireland

Saturday 24 March 2018

Sheep: Lamb growth hit by a triple whammy of negatives

Host farmer Michael Gowen and Tom O'Dwyer, Teagasc, check grass cover at the Teagasc dairy farm walk at Downing, Kilworth, Co Cork on 'Managing Through 2016'. Photo: O'Gorman Photography.
Host farmer Michael Gowen and Tom O'Dwyer, Teagasc, check grass cover at the Teagasc dairy farm walk at Downing, Kilworth, Co Cork on 'Managing Through 2016'. Photo: O'Gorman Photography.
Tommy Boland

Tommy Boland

Lambs were weaned at Lyons Research Farm three weeks ago and weaning weights were back 2.5kgs for the twin lambs from last year. There seems to be a number of reasons for this.

Initially the weather after turnout was very harsh and this impacted on lamb growth rate in the first four weeks of life, which is linked to reduced milk yield by the ewe. Secondly there appeared to be a secondary hatch of nematodirus when lambs were 10-11 weeks of age which again impacted on growth rate and required a second anthelmintic treatment.

Finally grass quality has proved to be a challenge in the run up to weaning when even low covers were heading out.

However, since weaning, growth rate has certainly stabilised and for the first two weeks post weaning growth averaged 240 grams per day which is running 50 grams per day ahead on the same period last year.

Grass growth is currently 40kg/DM/ha per day on the sheep grazing block, but this comes after a period of very high growth rate which saw around 40pc of the SmartGrass research platform cut for silage.

As weaning has taken place, we are now running eight separate flocks in this study, four groups of ewes and four groups of lambs. This is essentially operating as four separate farms with each farmer operating a leader follower system. The lambs graze paddocks down to between 5 and 5.5cm and then the ewes come in and take this down to 4cm.

This system will continue until eight weeks prior to mating at which time ewe body condition score will be assessed again and ewes will then be managed accordingly. Incidentally ewes had an average BCS of 2.8 at weaning.

Grass quality and supply will now be a key focus of our management for the foreseeable future.

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Post weaning grass supply and quality can have detrimental effects on lamb performance, with the latter quite often presenting the major challenge.

As the pre grazing herbage mass increases so too does the quantity of stem in the sward. The stem contains the most indigestible components of the grass plant so as the amount of stem increases, the digestibility of the grass decreases. This means that the lambs will consume less grass, and the grass they do consume will be of lower quality, especially in terms of its energy and protein content, ultimately leading to reduced lamb performance.

Where silage after-grass is available, the quality of the grass is increased as this is new growth.

This is ideal material for finishing lambs as it has high levels of protein and energy.

This week will see the selection of our replacement ewe lambs for the coming year. This process is a combination on the visual assessment of the animals and the interrogation of their genetic information.

As we are involved in the Sheep Ireland Central Progeny Test programme the parentage of all lambs on the farm is known, with the exception of the repeat lambs.

This data combined with the performance data of all other animals recorded by Sheep Ireland is used to generate breeding values for the various animals in our flocks and they receive a star rating of 1 to 5. One star indicates they are in the lowest 20pc of animals and 5-stars indicating they are in the top 20pc of animals.

As we are selecting replacement females we are focussed on the replacement index, with the other index being the terminal index.

The replacement index incorporates traits such as mothering ability, litter size, lamb growth rate and mature live-weight.

The overall aim of our farm is to have a prolific ewe, which is a good mother with good milk yield that will support lamb growth to weaning.

Dr Tommy Boland, lecturer in sheep production, Lyons Research Farm, UCD. @Pallastb

Indo Farming