Some errors in the determination of nitrogen retention of sheep by nitrogen balance studies

Abstract

I . Loss of NH, N from faeces and urine between voiding and collection and also losses in expired air, eructed gas and from the skin of wether sheep 2-3 years old given a ration of 400, 700, 1000 or 1300 g dried grass/day have been measured. 2. Losses of NH3 from faeces were negligible, and the loss from urine depended on the temperature and pH at which it was collected. Collection at neutral pH resulted in losses of up to 9.7 % of the urinary N as NH, gas if an acid trap were not incorporated in the collection apparatus. The average loss of N on collection of urine at pH values below 2.0 was 1.33 % when the ambient temperature was between 25 and 28O, and 0.97 % when it was between 15 and 18". 3. Very little NH, was lost in expired air or eructed gas, but when total NH, loss other than that from urine was determined, an average loss of 3'14+0.55 mg N/kg body-weight per day was found. This loss was independent of food intake and larger than the loss of N in suint which was estimated to range from 0 5 9 to 2-55 mg N/kg body-weight per day with the rations given. It was concluded that the larger losses found in some experiments were due to splashing o f urine on to the fleece during collection and subsequent loss of this urine N as NH,. It was shown that the losses of NH, N due to errors in urine collection and failure to consider dermal losses ranged between In this laboratory N balances are determined routinely during energy exchange studies with sheep. Sheep are harnessed for separate collection of faeces and urine, and urine is collected by the method described by Wainman & Paterson (1963). Incorporation of an acid trap between the urine reservoir and the continuously running pump used to aspirate urine into the reservoir in this apparatus was found to result in the trapping of between 0'02 and 0.77g ammonia N daily which would otherwise have been lost (Martin, 1965, unpublished). This loss represented from 0 ' 1 to 9-7 % of the N collected in the urine reservoir.In view of this loss of N, a study was made of the factors affecting it and an exhttps://www.cambridge.org/core/terms. https://doi

Errors in Measuring Nitrogen and Dry–matter Content of Plant and Faeces Material

“…Loss of N did not occur in faeces left for 24 hours at room temprature (22), which confirms the results of earlier workers (14,16). However, Waite, Johnston and Armstrong (25) observed a 2% loss of total N when samples were dried under vacuum at 27°C.…”

“…Loss of N from urine may be accentuated in situations where urine splashes on the wool of sheep and where sections of the collection apparatus are not maintained atlowpH. In these situations as much as 9-7 % of the total N may be lost as ammonia (16).…”

“…The accuracy of the chemical methods was discussed (18,21). N lost from faeces and urine samples, due to faults in methods of collection and storage, was judged the major reason for the estimated retention by balance experiments being higher than that estimated from slaughter data (6,16). The losses of energy and N associated with particular methods of drying samples are discussed below.…”

Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques

“…Spanghero and Kowalski (1997) found only a small, nonsignificant decrease in fecal N concentration over a 24-h simulated collection period but observed a 15% decrease in measured fecal N concentration following either air or freeze drying compared with the same sample analyzed without drying, which is why fecal N analysis is recommended to be performed on a nondried sample. Martin (1966) also found that volatile loss of N from feces of mature wether sheep fed dried grass hay was negligible over 24 h at varying ambient temperatures.…”

The effect of different dietary energy concentrations on the voluntary intake and growth of intensively-fed lambs

“…DISCUSSION Nitrogen retention. Large differences between nitrogen retention measured by the comparative slaughter technique and that measured by the balance technique have been encountered by other workers and reasons for the differences have recently been discussed by Duncan (1966) and Martin (1966 It is probable that the difficulty of carrying out an accurate balance trial with large animals, and the relatively small samples of excreta taken, contributed to the major share of the error in this trial. The utilization of dietary energy.…”