Effects of dietary protein and fibre of nitrogen excretion patterns in swine
Date
2001
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
Successful management of nitrogen (N) excretion is important for sustainable pork
production. Two experiments were conducted and their objectives were to study the
effect of dietary protein and fibre on N excretion patterns and to relate plasma urea (PU)
to urinary N excretion.
In the first experiment, three dietary protein contents (high, 197; medium, 169; low, 138 g kg⁻¹) and two levels of fibre (low and high) were tested. Diets (wheat, barley,
soybean meal; oat-hulls as the fibre source) were formulated to an equal digestible
energy (DE) content (3.25 Meal DE kg⁻¹) and at least 2.18 g digestible lysine per Meal DE, and were supplemented with Lys, Met, Trp, Thr, Ile, or Val. Pigs (32 ± 3.4 kg; n =
42) were housed in confinement-type metabolism crates for 19 d. On d 10 or 11,
catheters were installed by cranial vena cava venipuncture. Daily feeding rates were
adjusted to three times maintenance and daily rations were halved to two equal meals.
Faeces and urine were collected from d 15 to 19. Five blood samples were collected in
two-h intervals on d 16 and 19. Faecal N, urinary N, and total N excretion were reduced
linearly with a reduction of dietary protein content (P < 0.001). Reduction was greater
for urinary (48%) and total N excretion (40%) than for faecal N (23%) excretion. The
ratio of urinary N to faecal N was reduced linearly with a reduction of dietary protein
content (P < 0.001). Retention of N (g d⁻¹) was reduced linearly but N retention as
percentage of intake was increased linearly with a reduction of dietary protein content (P < 0.001). Addition of oat hulls did not affect N excretion patterns (P > 0.10). Dietary treatments did not affect average daily gain (ADG) or feed efficiency (P > 0.10). Plasma
urea increased after feeding, peaked at 4 h and then decreased toward pre-feeding
concentrations. A linear relationship of urinary N to PU concentration (R² = 0.66) was
observed.
In the second experiment, effects of dietary protein content (high, 185; and low, 157 g kg⁻¹) and fibre sources on N excretion patterns were studied in a 2x3 factorial
arrangement. The three fibre sources were control, soybean hulls (SH; 15% ), and sugar
beet pulp (SBP; 20%). Diets were formulated to 3.3 Meal DE kg⁻¹ and 2.4 g digestible
Lys per Meal DE, and were supplemented with Lys, Met, Trp, Thr, lie, or Val. Pigs
(30.5 ± 3 kg; n = 36) were housed in confinement-type metabolism crates, with restricted access to feed (3 x maintenance DE) from d 1 to 18, and free access to feed
from d 19 to 26. Faeces and urine were collected from d 15 to 18 and d 23 to 26, and
blood samples on d 17 and 25. With restricted access to feed, faecal N (as % of N intake) was increased 3 percentage units for low compared to high protein content, and
increased 4 percentage units for SH and 6.5 percentage units for SBP compared to
control (P < 0.05). Urinary N was reduced 5 percentage units for low compared to high
protein content, and reduced 9 percentage units for SBP compared to control (P < 0.05).
Retention of N (g d⁻¹) was reduced 12% for low compared to high protein content (17.9 compared to 20.4 g d⁻¹; P < 0.05), and was similar among fibre treatments (P > 0.10).
With free access to feed, faecal N (as % of N intake) was increased 2.5 percentage units
for low compared to high protein content, and increased 5 percentage units for SH and 9
percentage units for SBP compared to control (P < 0.05). Urinary N was reduced 5
percentage units for low compared to high protein content, and reduced 9 percentage
units for SH and 10 percentage units for SBP compared to control (P < 0.05). Retention
of N (g d⁻¹) was similar for dietary protein content (30.5 g d⁻¹; P > 0.10), and reduced for
SH (27 g d⁻¹; P < 0.05) compared to control (31 g d⁻¹), while was intermediate for SBP
(29 g d⁻¹). A linear relationship of urinary N to PU concentration was observed with
both restricted (R² = 0.66) and free access to feed (R²= 0.71).
Reduction of dietary protein content is an efficient way to reduce total and
urinary N excretion, which may reduce ammonia emission. Inclusion of fibre sources
high in fermentable fibre shifted N excretion from urine N to faeces N while fibre
sources resistant to fermentation did not have any effects on N excretion patterns.
Combined effects of dietary protein content and fibre reduced urinary N excretion
further than single effects. Level of feed intake is an important consideration when
effectiveness of a nutrient management strategy is studied. Diets with a low protein
content and containing synthetic AA should be studied using pigs with free access to
feed to verify that N retention is maintained. A linear relationship of urinary N to PU
concentration was observed under both restricted and free access to feed indicating that
urinary N excretion could be predicted from PU concentration.
Description
Keywords
Protein, Fibre, Grower pigs, Nitrogen excretion, Plasma urea
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal and Poultry Science