Tom Ward

Writing an article telling farmers how to fatten their lambs is akin to telling your grandmother how to suck eggs; everyone has done it and there are many ways to skin this particular cat, and the weather always dictates what a farmer can do anyway.

So, from my perspective; I am always keen to look at lamb finishing from the return per kilogram of drymatter consumed, and this approach means a focus on higher growth rates being desirable. This may not suit everyone as the lamb finishing business is always only a part of the total farm system, which itself reflects each farmer’s goals and the farm’s strengths and limitations.

Organising tupping, so that a high proportion of ewes are mated quickly, improves feed efficiency, brings forward average sale date, and improves the marketability of a line of lambs.

For example, with winter lamb finishing, growth rates are often held back to avoid over-fats and over-size lambs, and part of the lamb profit comes from the grooming effect on seed crops.

What is most important is that the farmer needs to be very clear about why he does what he does; why he breeds, finishes in summer or sells store, trades in summer or trades in winter.

Most of the time, lamb growth rate is a big driver of profitability, right up there with lambing percentage. It’s a combination of the two, with the bottom line expressed as total carcaseweight times dollars per kg CW, minus the costs.

Many factors combine to drive lamb growth rate: ewe body condition score (BCS), genetics, pasture quality and quantity, ewe milking potential, animal health, water supply, climate, weather and geography.

Higher growth rates result in lambs sold earlier, (releasing more feed for other stock classes) and better feed conversion efficiency (less feed required to achieve targets).

If the farmer is breeding, a minimum ewe body condition score (BCS) of 3.0 is so important because, with good feeding and genetics, it drives everything that the ewe can achieve. At mating, the potential lamb drop and timing of that drop is determined.

Organising tupping, so that a high proportion of ewes are mated quickly, improves feed efficiency, brings forward average sale date, and improves the marketability of a line of lambs. Maintain the ewe BCS through winter and set stock only one week out from lambing, on to pasture covers which average 2000kg DM/ha. Feed the lambed ewes 3kg DM/day and if feed gets short consider weaning at six-nine weeks provided lambs are at least 16kg LW.

This will save at least 20% of feed and avoid a reduction in lamb weight. Lamb on the feed growth curve, not before it. Remember it is potentially easier to grow lambs pre-weaning.

I have spent the last paragraphs talking about matters from conception to lambing, because that is where, if the farmer is breeding, the groundwork is laid for successful lamb finishing.

For lamb finishing, feed quality and quantity are equally important.

Feed quantity can be increased by winter or summer cropping, nitrogen application, grazing off some stock in winter if necessary, using supplement like balage, use of specialist crops in spring like lucerne, annual ryegrass, and cocksfoot, and feeding less-profitable stock classes at less than maintenance levels (eg: breeding cows).

Feed quality is fundamentally at its best in spring/early summer on most New Zealand farms; by early December a combination of heat and seed head emergence is reducing ME in ryegrass pastures significantly, however legumes will be emerging to compensate in part for this.

So, highest lamb growth rates are achievable prior to weaning and the lamb markets are generally at their most positive before the Christmas break as moisture levels are usually good. Declining feed quality not only reduces lamb growth rates through less energy per kg DM, it also reduces lamb intake because lower-quality feed takes longer, sometimes 24 hours longer, to digest. If the pasture contains a mixture of green, stalk and dead material, the lamb must only be required to eat the green, and the rest be tidied up by other means.

To show the benefit of growing lambs faster in a trading situation, two gross margin studies on Farmax software, Low growth rate (Low GR) and High Growth Rate (High GR) are summarised left. The study is of 3000 wether lambs purchased November 12 for $4.26/kg LWT. The schedule declines from $8 in December to about $7/kg CW in March.

Matters to focus on when buying lambs

Lamb quality – buy healthy, strong, well-grown lambs and research the breeding – buying off drought-stressed farms is what we often do but a cheap price is no substitute for a quality animal. Some farmers are very, very picky about the lambs they buy.

Animal health – remedying low blood serum levels for Vitamin B12 can improve growth rates by 50-100g/day. Do liver biopsies off freshly weaned lambs if you suspect cobalt deficiency.

Worms – doing faecal egg count in pastures, faecal egg reduction test to test the efficacy of the drench, and managing pastures to minimise worms are all important in managing what is potentially a very damaging problem.

Change the drench family in the autumn and avoid drenching at less than 28-day intervals. After lambs arrive on the farm use a quarantine drench and hold the lambs off pasture for 24 hours, then on a contaminated paddock for 24 hours. Watch with holding periods.

Viral pneumonia – can halve the growth rate of lambs. To manage this, minimise yarding, avoid dusty yards and tracks, avoid middle of the day yarding and long walks, yard in small mobs, avoid shearing lambs at weaning, and avoid buying lambs from proven sources of pneumonia.

Flystrike – constant vigilance, keep lambs free of dags, and jetting.

Feeding specialist crops through summer – This needs careful thought as variation in yield, the costs of establishing crops and regrassing, damage to the crops over time, and low lamb growth rates, can kill the profit. Nevertheless, there are plenty of success stories from farmers using lucerne, red clover, chicory and plantain, annual ryegrasses, tall fescue and cocksfoot, pasja and raphnobrassica to create specialist lamb finishing feed.

Higher lamb returns have increased specialist lamb finishing feed crops this year. Farmers need to give themselves time to learn how to manage new crops and not be disillusioned by a less-than-happy experience in the first one or two years. Do not underestimate the time needed for lambs to adjust to the forage crop. Animal health matters may be even more important, for example salt on lucerne, clostridial vaccination on fodder beet.

  • Tom Ward is an Ashburton-based farm consultant.