Minimizing the Adverse Effects of Ammonia in the Lambing Shed
Published on Feb. 22, 20202
Whit Stewart, Ph.D. Assistant Professor, Extension Sheep Specialist
With lambing shortly upon us, we are in the midst of organizing supplies, labor and setting up jugs. Perhaps we’re thinking about what we’d like to do differently this year than previous years.
And yet, while scarcity of time and labor resources at lambing seems to be something, we all have in common, there is also the ever-present gaseous ammonia issues that all confined lambing operations fight. Efforts to mitigate gaseous ammonia in the lambing shed can lead to healthier lambs and healthier lambing help.
Adverse effects of ammonia on sheep
Some effects of ammonia on sheep include an infected upper respiratory tract and the epithelium lining the nasal passages, trachea and pulmonary airways is damaged.
Sheep affected may show observable flow of tears, nasal secretion and coughing. When ammonia comes in contact with moisture in the upper respiratory tract it produces ammonium hydroxide which elicits coughing.
The ammonia molecule is composed of nitrogen and hydrogen, yet the real culprit of ammonia production comes from the result of excess nitrogen protein being excreted as urea in the urine and, to a lesser extent, feces.
Once this urea is converted to ammonia by specialized urease bacteria, the ammonia in the liquid phase converts to the eye-watering, cough-inducing volatilized ammonia. So how can we minimize the production of ammonia?
Unfortunately, sheep are not perfect when it comes to metabolism, and over feeding of protein immediately prior to lambing and in the lambing jug results in increased protein excretion and greater ammonia being produced wherever the ewe urinates.
While it’s important to meet the ewe’s requirements, the first 24 to 48 hours post-partum in the jug doesn’t require the third cutting alfalfa, but rather the more moderate crude protein in a grass-alfalfa mix, which can reduce the protein being excreted in the urine.
Although not feasible for everyone, feeding protein sources that are less rumen degradable sources such as soybean meal, distillers and cottonseed meal will result in less urea excreted in the urine compared to degradable protein sources e.g., alfalfa.
Feeding high moisture feeds, such as silage and haylage, also increases urine output which can also lead to excessive urination and creates a moist environment for ammonia production to thrive.
Bedding and cleaning of the jug
Adding lime to the cleaned jug increases the pH at the soil surface. If pH is raised enough it can kill certain bacteria in the jug environment. For these reasons, liming the jug can help reduce bacterial loads. Anecdotally producers have commented aggressive liming of jugs can also help in controlling pathogenic organisms involved in mastitis.
Unfortunately, lime accelerates how quickly the ammonia is volatilized. So, cleaning jugs when removing ewes and immediately liming, then waiting a minimum of a few hours will help volatilize the ammonia. This is challenging when jug space is limited, but justifies having extra jug space on hand.
An ideal time frame to allow addition of lime to stand is 24 hours, however the guiding principle should be to immediately remove old bedding and add lime.
Creating dry environments in jugs and group pens minimizes pathogenic bacterial loads and the environment they thrive in. Thus, selecting an absorbent bedding option and regularly cleaning when ewe-lamb pairs move out is the best management practice.
When transitioned to group pens, creation of a creep bedded area where only lambs can bed down can minimize the ammonia concentrations where those lambs bed down.
Even if we cannot smell the ammonia at our standing level, if we put our nose six to 12 inches from the ground surface, we can simulate what the lamb is exposed to.
Good drainage in both the lambing shed and group pens will extend the bedding and help maintain the dry environment necessary to reduce pathogen loads and ammonia production.
In a confined setting with little ventilation, we can have excessive ammonia accumulation. Imagine the ammonia levels of walking into the shearing shed after trying to dry off sheep for 12 to 24 hrs.
Although that represents the extreme scenario, it highlights the excessive levels our noses can detect.
A good rule of thumb is if we can smell ammonia then it probably presents at unhealthy levels. Unfortunately, our ability to smell ammonia diminishes over time with exposure, so relying upon our ability alone isn’t fool proof. The most fool proof solution is a good ventilation system.
The objective of any good ventilation system is built on the principle of replacing moist air inside the barn with the cool dry air from the outside.
Not only are we removing the stale air but respired moisture, CO2, dust and airborne pathogens. Simplistically, any good ventilation system contains an inlet system for fresh air entry, exhaust system for removal of air and air regulation to balance the correct amount of air entering and leaving the shed.
An acceptable range of relative humidity is 50 percent to 80 percent humidity. However, under the spring blizzard scenarios the act of maintaining adequate temperatures within the lambing shed while removing moisture is a balancing act that may require greater engineering expertise.
One strategy for bringing in fresh air is a negative pressure system, which relies upon an exhaust system to create a negative pressure and an inlet system to distribute the incoming air. In theory, the system needs to be sized for at least three ventilation rates: Winter, mild weather and summer, but for lambing sheds, cold weather ventilation is adequate.
Understanding the detrimental effects of ammonia production on lambing success and implementing measures to reduce its negative impact can increase returns on any sheep enterprise.
Implementation of feeding, bedding and housing management strategies will depend on available resources, yet understanding some the principles discussed will allow operational adaptations to be made. Cheers to a heavier weaning weight and a higher weaning percentage this year.
Whit Stewart is the University of Wyoming Extension sheep specialist. He can be reached at firstname.lastname@example.org.