[15N-flow after in sacco incubation and feeding of sheep and goats with untreated wheat straw or straw treated with 15N horse urine].

The research examines the nitrogen-flow in sheep and goats when fed with standard wheat straw or wheat straw treated with horse urine, which was labeled with Nitrogen-15 (15N), a naturally occurring stable isotope of nitrogen used as a tracer. The study aimed to understand how the urine-N (Nitrogen in the urine) interacted with the straw, and how it was metabolised within the animals’ rumen.

Preparation of Feed

• The straw was prepared by thoroughly mixing chopped wheat straw with horse urine that contained a specific concentration of 15N. This was then stored airtightly for six months.
• Three rumen fistulated sheep and three goats (animals with a surgically installed passage into their rumen) were selected and fed with either untreated straw or straw that had been treated with the urine.
• Along with the straw, concentrates were also added to their diet to maintain a balanced feed.

In Rumen Incubation Process

• The treated and untreated straw was then put into nylon bags and placed in the rumen of the sheep and goats for various time intervals – 1, 3, 6, 12, 24, 48, and 72 hours.
• After each interval, the bag content was analysed for its 15N-excess and total 15N quantity. The data were used to construct a three-compartment exponential function to understand the inflow and outflow of 15N.

Results and Conclusions

• The curves derived from the exponential function showed how much urine-N was bound by the straw during storage and how much of this bound nitrogen was later attached to the straw in the animals’ rumen.
• The research found that most of the urine-N was not compactly bound by the straw during storage. Instead, the majority of the nitrogen attached to the straw in the rumen came from microbes, with only about 6% coming from the urine.
• Further, similar curves were calculated for the 15N amounts on nylon bags and these helped determine the tracer flows even without specific quantitative information.
• When comparing species, the researchers found no significant differences between sheep and goats regarding their nitrogen metabolism or the handling of the treated straw.