The effects of dietary nitrogen to water-soluble carbohydrate ratio on isotopic fractionation and partitioning of nitrogen in non-lactating sheep
Abstract
The main objective of this study was to investigate the relationship between partitioning and isotopic fractionation of nitrogen (N) in sheep consuming diets with varying ratios of N to water-soluble carbohydrate (WSC). Six non-lactating sheep were offered a constant dry matter (DM) allowance with one of three ratios of dietary N/WSC, achieved by adding sucrose and urea to lucerne pellets. A replicated 3 dietary treatments (Low, Medium and High N/WSC) × 3 (collection periods) and a Latin square design was used, with two sheep assigned to each treatment in each period. Feed, faeces, urine, plasma, wool, muscle and liver samples were collected and analysed for ¹⁵N concentration. Nitrogen intake and outputs in faeces and urine were measured for each sheep using 6-day total collections. Blood urea N (BUN) and urinary excretion of purine derivative were also measured. Treatment effects were tested using general ANOVA; the relationships between measured variables were analysed by linear regression. BUN and N intake increased by 46% and 35%, respectively, when N/WSC increased 2.5-fold. However, no indication of change in microbial protein synthesis was detected. Results indicated effects of dietary treatments on urinary N/faecal N, faecal N/N intake and retained N/N intake. In addition, the linear relationships between plasma δ¹⁵N and urinary N/N intake and muscle δ¹⁵N and retained N/N intake based on individual measurements showed the potential of using N isotopic fractionation as an easy-to-use indicator of N partitioning when N supply exceeds that required to match energy supply in the diet.... [Show full abstract]
Keywords
stable isotope; water-soluble carbohydrates; urinary nitrogen; purine derivatives; Dairy & Animal Science; Feces; Animals; Sheep, Domestic; Nitrogen; Nitrogen Isotopes; Urea; Dietary Carbohydrates; Sucrose; Blood Urea Nitrogen; Chemical Fractionation; Analysis of Variance; Animal Feed; Male; Mass SpectrometryFields of Research
0702 Animal Production; 070204 Animal Nutrition; 06 Biological Sciences; 07 Agricultural and Veterinary SciencesDate
2013-08Type
Journal ArticleCollections
© The Animal Consortium 2013