Monday, January 6, 2014

Drought Planning

I took my friend Pat Shanley to lunch just before Christmas.  Pat was born in Auburn in 1920, so he has first-hand experience with all kinds of weather years here in the Sierra foothills.  He told me that December 2013 was the driest December in his memory.

I received a forwarded email today from the superintendent of the Sierra Foothill Research and Extension Center (SFREC) in Browns Valley that confirms Pat's observations.  Since 1991, SFREC has collected forage production data for November and December.  These measurements basically account for the amount of forage that grows after the first germinating rain in the fall until the soil is too cold to support further growth.  Since 1991, the average forage production from germination through the end of December is 482 pounds of forage (basically grass) per acre.  This year, forage production from the germinating rain we received on November 21 through December 31 was just under 48 lbs per acre!  Furthermore, soil temperatures at SFREC dropped below 50F on December 5 - which means grass growth is at a standstill until soil temperatures rise sometime in mid-February.  Normal precipitation from September 1 through December 31 at SFREC is around 11 inches - this year, they measured 3.27 inches.  In other words, it's shaping up to be one of the driest years on record - and it suggests that Pat has a pretty good memory!

After I read this email, I checked the long range forecast on Weather Underground, AccuWeather and the National Weather Service website.  Each forecast has indicated a chance of rain in the next 10 days, but as of today that chance seems to have evaporated.  Based on the current forecast, I wouldn't be surprised if we receive less than an inch of precipitation this month.

What's a grass-farmer to do? We time our lambing season to take advantage of the "spring flush" of grass growth - usually mid-February through late-April.  By matching our peak demand for forage with peak supply, we try to ensure that we have enough animals to use our forage resources efficiently. Usually, we have more grass than mouths to feed, but this year looks to be very different. Due to our move to Rio Vista, we're lambing a bit later than usual, but we would likely be facing a pretty lean year in terms of forage production regardless of where our sheep have their lambs.

We have two options in the short term - destocking and early weaning.  While most producers have culling criteria that they use every year, drought conditions may require us to go beyond our normal considerations to further reduce our flock size.  Early weaning can also reduce forage demand – the sooner an animal’s offspring is weaned, the sooner that female can dedicate energy to restoring body condition in anticipation of the next breeding season (instead of to producing milk).

Typically, we cull our ewes based on productivity – an open (un-bred) ewe is sold so that we make sure our pregnant ewes have enough feed.  This year's drought conditions, however, may require a more aggressive culling strategy.  We have identified an “A” flock (animals we will keep) and a “B” flock (animals that can be sold during drought).  The "B" flock will probably be sold by the end of January.

Here are a few additional factors we consider when deciding whether to keep or cull a specific animal:
  • Productivity (as measured in pounds of lambs, calves or kids weaned): keeping ewes that under-produce can compromise the health and productivity of our higher producing ewes by utilizing scarce forage and water resources.  Obviously, this requires careful record-keeping - the records we've maintained over the last 5 or 6 years will pay off now.
  • Age: research at the UC Sierra Foothill Research and Extension Center has demonstrated that weaning weights of calves and pregnancy rates decline dramatically in cows that are 10 years of age or older.  Drought can be good time to cull older animals.  We've already culled most of our older ewes, but we'll take another look at the flock this month.
  • Behavior: most flocks contain individual animals whose behavior presents management problems.  For example, a ewe that has learned not to respect electric fence may teach other sheep to escape.  A ewe that is aggressive when being worked in the corrals can be dangerous.  Drought can present an opportunity to remove these problems.
  • Physical Health: low performance may be related to physical health issues – foot rot in sheep, for example.  Aggressively culling animals for physical problems can improve overall herd productivity in the long run.
  • Genetics: Drought can present an opportunity to analyze and adjust the genetic composition of your herd.  Again, detailed record-keeping is crucial.  Animals whose genetic potential fits our production system and resources of the ranch will be retained; those who do not will be culled.

Destocking also requires requires us to examine our female replacement strategies and capacity for running stockers or feeder animals.  Reduced forage supplies may mean keeping fewer replacement ewe lambs and reducing the number of feeder lambs kept as stockers.  We'll evaluate these options later in the spring.

Early Weaning
Weaning  lambs earlier than normal is another effective strategy for surviving drought.  Ewes experience their highest nutritional demand when lactating.  In addition, ewe lambs and yearling ewes have even greater nutritional demand because their bodies are still growing, which requires energy and protein levels above that of mature females.  Early weaning can allow females to regain body condition prior to breeding and may help boost conception rates during times of drought.

With lambs, early weaning can occur as soon as 14 days of age, although most early weaning of lambs  takes place at 45 to 60 days of age.  We make sure our lambs are drinking water and consuming adequate amounts of dry feed prior to being weaned.  While we have focused on grass-fed production, we may creep feed our lambs this year (creep feeding involves providing feed to lambs while keep it away from their mothers - this replaces some of the protein and energy the lambs would normally get from mother's milk).   Heavily lactating ewes may develop mastitis, so we'll watch them carefully during the weaning process.  We'll probably try to wean all of our lambs by the middle of May this year.

Part of the bargain that we strike with Mother Nature when we decide to make our living from farming or ranching is that we'll make due with whatever she gives us in any given year.  This year looks as if it will test the boundaries of that bargain!

Renquist, B.J., J.W. Oltjen, R.D. Sainz and C.C. Calvert.  2006. Effects of age on body condition and production parameters of multiparous beef cows. Journal of Animal Science. 84(7):1890-1895.

Doran, M. 2014. Managing Cattle During Drought: Destocking and Early Weaning

Pratt, D. Ranch Management Consultants, Inc.

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