The heat of combustion of the urine of sheep and cattle in relation to its chemical composition and to diet

Abstract

I . The results of over 500 determinations of the heat of combustion of the urine produced by cattle and sheep have been analysed statistically. 2. The analytical errors for nitrogen, carbon and heat of combustion were k 0.54, f 1'4 and ? 2.2 %. The error attached to an estimate of the heat of combustion of the urine produced by an individual sheep in 4 days was & 10 %. 3. At the maintenance level of feeding, the heat of combustion of the urine ( U kcal/ 100 kcal food) was related to the crude protein content of the diet (P%) by the equation U = 0.25P+ 1.6, with a residual standard deviation of To.88 kcal/Ioo kcal. 4. Regression analysis of the relation between the heat of combustion of urine and its N content showed significant differences with diet. The heat of combustion of the urine of sheep was 9.7 kcal/g C and of cattle 10.3 kcal/g C, and did not vary with diet. 5. It is shown that the variation in the heat of combustion of urine/g N and its relative constancy/g C arises largely from variation, from diet to diet, in the proportion of the N excreted as hippurate. The metabolizable energy of a feed is its heat of combustion less the heat of combustion of the faeces, urine and combustible gas produced when it is eaten. In many trials with ruminants designed to provide an estimate of the nutritive value of feeds, the measurements made are limited to determinations of the heat of combustion of the feed and the faeces and neither methane nor urine energy are determined. In some trials, however, the nitrogen content of the urine is determined. Methods are available which enable the methane produced when different diets are given to ruminants in different amounts to be predicted with reasonable precision from knowledge of the faecal loss of energy (Blaxter & Clapperton, 1965) and, if methods were available for estimating the loss of urine energy from commonly measured attributes of the feed, then metabolizable energy could be estimated from the results of trials more simple than complete calorimetric ones.Understandably many attempts have been made to estimate the heat of combustion of ruminant urine from its more easily measured N content. The earliest of these consisted of assigning a constant calorific value to the urine/g N although most of the workers concerned realized that this ratio varied with diet (see Armsby, 1908). More recently the heat of combustion of urine has been related to its N content by linear regression methods, which, since they rarely have intercepts of zero, implies that the heat of combustion of urine changes with its N content. Thus Paladines, Reid, Van Niekerk & Bensadoun (1964) Other less satisfactory approaches have been made. Thus both Elliot & Loosli (1959) with cattle and Street, Butcher & Harris (1964) with sheep and cattle have related the heat of combustion of urine/unit weight to its N content/unit weight. Both found positive intercepts for their regressions. This approach implies that the heat of combustion of the urine produced by an animal in a day is greater when it is s...

Dairy cow excreta patches change the boreal grass swards from sink to source of methane

“…This is supported by the bucket experiment where high amounts of CH 4 were emitted from the dung. The C content of dung from dairy cows using similar dietary, 430 g C kg -1 (P. Virkajärvi, unpublished results) is also much higher than C content in urine reported in the literature, 2−6 g C kg -1 (Blaxter et al 1966, Petersen et al 2004). The high soil concentration after dung application was probably result of CH 4 diffused into the soil from dung.…”

Silagem de grãos úmidos de milho de textura dura ou macia em dietas com polpa cítrica para vacas em lactação

“…3). Apesar de a substituição de milho por polpa de citros ser capaz de atuar negativamente sobre a produção de leite (Broderick et al, 2002;Salvador et al, 2008b), os resultados aqui obtidos evidenciram que, nesse tipo de formulação dietética (Tab. 1), a polpa cítrica resultou em produção diária similar à do milho ensilado.…”

“…Broderick et al (2002) também não observaram resposta em teor de Nureico no leite quando 19% da matéria seca dietética de milho úmido ensilado foram substituídos por polpa cítrica. Teoricamente, a menor eficiência de síntese de proteína microbiana, quando pectina e sacarose substituem amido (Hall e Herejk, 2001;Sannes et al, 2002), poderia aumentar a excreção de Nureico no leite nos tratamentos com maior teor de polpa cítrica.…”

“…3). Assumindo que o incremento calórico, oriundo do metabolismo ruminal ou do metabolismo intermediário de ruminantes, varia pouco dentro da amplitude fisiológica na relação entre os ácidos graxos voláteis produzidos no rúmen (Orskov et al, 1979), e que a perda urinária de energia não estaria variando nesses tratamentos isonutricionais (Blaxter et al, 1966), a relação entre a secreção diária de energia no leite e o CMOD seria uma medida indireta de metano excretado por dia. Esses dados sugerem que a substituição de milho por polpa cítrica, teoricamente capaz de aumentar a proporção de acetato dentre os produtos da fermentação ruminal (Leiva et al, 2000;Broderick et al, 2002;Salvador et al, 2008a), não teve magnitude suficiente para alterar a eficiência de utilização energética nestes animais.…”

The voluntary intake and utilization of roughage–concentrate diets by sheep. 2. Barley and soya bean meal supplementation of hay diets

“…The estimated mean daily intake of metabolizable energy by each lamb during the experiment was calculated from the intakes of digestible energy and the dietary crude protein content by using the conversion figures of Blaxter, Clapperton and Martin (1966). The correction of methane energy losses for level of feeding (Blaxter and Clapperton, 1965) was not applied.…”