Friday, March 29, 2024

Flocking to new stock policies

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The harsh drought in north Canterbury’s Hurunui district has tested the resilience of the farming community over the past 12 months.  A string of above-average seasons over the previous three to four years had farmers wondering when the good run would end. However, no one could have predicted the severity of this year’s mega drought and all but the most flexible operations have struggled to cope with the huge challenges that have been presented. 
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Farmers likely face another dry summer and everyone is sweating on spring and what’s in store. It is crucial we continue to make early decisions to assist with farming in an El Nino weather pattern. Already we have seen initiatives adopted by farmers to aid with destocking and add feed to their systems. This includes the grazing-off of more than 100,000 pregnant ewes from the Hurunui area. In a season of many firsts it is necessary to challenge how we do things in terms of stock policies and look for every improvement in feeding efficiency.

The following observations draw on a wealth of information on sheep nutrition and production and acknowledge the excellent research work of others. Understanding the principles behind feeding ewes over lactation and the timing of weaning will likely be key areas this coming spring-summer for these predominantly dryland sheep and beef farmers.  

Many operators have done exceptionally well by achieving a pre-lambing ewe body condition score of close to 3 which is the magic figure to encourage lamb survival and early lamb growth. Because of the adverse climate, pre-lambing pasture covers for set stocking are down at 700-800kg drymatter (DM)/ha rather than the 1200-1500kg DM/ha that is recommended to provide sufficient energy to maintain ewe condition through early lactation. 

Ewes are obligated to make milk for their lambs so in a negative energy balance situation they will milk condition off their backs. This has serious implications for getting ewes up to target liveweights for mating in 2016. If feed is tight in early lactation then the peak of lactation at two to four weeks is lowered and less total milk is produced. 

About half of the ewe’s milk is produced in the first four weeks of lactation. Ewes that were in ideal body condition at lambing will obviously tolerate a feed pinch over lactation much better. The supplementation of these “under pressure ewes” in early lactation with high-energy feeds such as palm kennel, soybean hulls, or barley can be a cost-effective strategy if finances allow and providing it is logistically practical.

There is a window of opportunity to sell ewes with lambs at foot after tailing if feed conditions remain poor. Once the stocking policy is decided it is worthwhile considering creep feeding systems for the preferential feeding of lambs (especially multiples) between two and eight weeks of age, and to assist with early weaning. This can ensure that valuable, quality feed goes to the lamb alone. 

The contribution to lamb growth through milk from the mother declines after peak lactation, dropping from 2.5-3kg/day at the peak to about 0.5-1 kg/day by week 12. Creep feeding systems rely on vertically barred gates with 200-300mm spacing giving access to fenced feeding areas containing meal or superior pasture for young lambs. 

Meal helps the lamb transition on to pasture more quickly because it accelerates rumen development and it facilitates early weaning as an option by providing the high levels of protein and energy required by young lambs. An eight-metre square pen with creep feeding panels can service a mob of up to 400 ewes and lambs.

It is important to emphasise when lactating ewes can be fed well through to 12 weeks of age then lambs will grow the best on mum, however, when feed is limiting early weaning might be an option. Another advantage of early weaning is that ewe intakes fall by 20% post-weaning. This allows these recently weaned ewes to put on about 50g per day, which will start them tracking towards next season’s mating target liveweight. 

Lamb-selling strategies should be worked out in advance with advisers because these will influence weaning decisions. Early weaning should only be attempted after six weeks of age and only in conjunction with lucerne or lambs conditioned to protein meal supplements. Average spring pasture will not supply the level of protein and the energy that is required for six-week-old lambs. 

The crude protein requirement of a lamb less than 20kg is relatively high at 14g of megajoules of metabiolisable energy. If no meal or lucerne is available then weaning should be delayed to at least eight weeks of age and the lambs then weaned on to legume-dominant pasture. It is important that lambs selected for early weaning are above 15kg so weaning at six weeks and 15kg is the earliest and lightest weight that weaning should be attempted and regardless of nutritional efforts small lambs can result. It is generally accepted that weaning earlier than eight weeks is a risky strategy.

In a tight feed season weaning between eight and 12 weeks can be an option worth investigating. 

There are specific animal health problems to watch for during a tough spring and some diseases are more commonly associated with early-weaning scenarios. 

Magnesium grass staggers can occur in ewes around peak lactation, especially when pastures are short and during cold, windy weather. 

Shorter pasture covers and a drier spring can make fluorine toxicity from pastures recently top-dressed with superphosphate a risk.

To further discuss animal health issues particular to your farming system contact your local veterinarian.

Lamb health

Young lambs under nutritional stress, especially at a high stocking density and-or associated with creep feeding can be more susceptible to disease. These include scabby mouth, internal parasites, clostridial disease, skin infections, trace element deficiencies, lice and flystrike. 

Scabby mouth is exacerbated by chewing grass under thistles when pasture is short. Monitor for internal parasites and be vigilant against diarrhoea and ill-thrift in these young lambs. 

Lambs begin eating grass at three weeks of age but roundworm burdens are unlikely to be significant before six to eight weeks. Usually lambs do not require drenching until weaning so any pre-weaning treatment should be based on objective information and farm-specific advice.

Other internal parasites that can occasionally cause problems in young lambs include coccidia and cryptosporidium. Many ewes are lousy this year with the dry conditions suiting this ecto-parasite so treatment of lambs and ewes, preferably post ewe shearing might be necessary. 

Any disease causing diarrhoea or skin infections will predispose animals to flystrike so preventative treatment of lambs at tailing might be appropriate. Much of Hurunui is sporadically low in vitamin B12 and is always low in selenium so regular supplementation with these two trace elements is important. Cover for lambs against clostridial disease is strongly recommended and any creep feeding of lambs with meal will increase the risk of pulpy kidney in younger lambs.

  • Gerard Poff is a sheep and beef cattle veterinarian for North Canterbury Veterinary Clinics and a part-time farmer.
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