Brown fat measurement could offer key to improving lamb survival

AgResearch's Sue McCroad with lamb.Not all fats are created equal, and work by AgResearch is looking into how this knowledge can help reduce lamb deaths.

In good conditions, mortality of twins and triplets is below 10 percent and 20 percent respectively, but in poor weather conditions it can be much more. Many of these deaths occur in the first three days of life, often because the lamb is unable to generate enough body heat to keep warm during periods of extreme weather.

Immediately after birth and until they get a feed, lambs have only one main way to regulate and maintain their body temperature: burn ‘brown fat’ to generate heat.

This special fat, officially called brown adipose tissue, is vital for newborn lambs to generate enough heat to survive extreme weather conditions.

Previous work at AgResearch looking at the effects of various maternal supplements on lamb birth-weight and growth performance also saw an increase in brown fat stores.

Research physiologist Dr Sue McCoard, from AgResearch’s Grasslands campus in Palmerston North (pictured above), wanted to look more closely at this effect, as well as finding better ways of measuring brown fat stores in animals. She applied for and received a $35,000 Curiosity Fund grant, which is a seed fund enabling AgResearch staff to investigate ideas that could benefit the pastoral sector.

Her project has been looking at using thermo-imaging as the first non-invasive way to measure the amount of brown fat in the body, and what could possibly increase brown fat deposit in multiple newborns.

“For the first few days of life newborn lambs are reliant on the brown fat. This is particularly important if they are born in challenging circumstances such as storms, where chill index is high, or if they don’t have much milk to drink,” she says.

“Thermo-imaging is being looked at as a non-invasive way to gauge the amount and availability of brown fat carried by each animal.

“Previous to this, the only way to measure brown fat in the body required the slaughter of animals.”

Increasing prolificacy in sheep is a cost effective approach to increase the efficiency of meat production in a sustainable manner. An increase in multiple pregnancies is one of the reasons lamb production in New Zealand has been maintained in spite of reductions in the number of breeding ewes in the last 20 years.

However, twins and triplets are usually smaller at birth and suffer increased mortality early in life compared to their singleton counterparts.

“It’s a major issue on farm, particularly where ewes haven’t been allocated enough feed, in times of cold stress,” Dr McCoard says.

“Finding consistent ways to increasing brown fat in new-born lambs is key to improving core temperature, and therefore survivability in early life.

“Increased lamb survival, and increasing the number of live lambs that can be sold or used as replacements, will make a major contribution to the welfare and economic outcomes of lamb production on New Zealand sheep farms.”

 

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