Response in nitrogen balance, fibre digestibility and physicochemical characteristics of digesta in Windsnyer pigs fed on incremental levels of amarula nut cake.
Loading...
Date
2021
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The broad objective of the study was to determine the response in nitrogen balance, fibre
digestibility and physicochemical characteristics of digesta in slow-growing Windsnyer pigs fed
on incremental levels of amarula nut cake (ANC) based diets. Thirty clinically healthy growing
Windsnyer pigs (21.5 kg ± 4.97) (mean ± standard deviation) were individually assigned to
separate pens in a completely randomized design. Five iso-energetic dietary treatments were
formulated to contain 0, 50, 100, 150, and 200 g/kg dry matter (DM) of ANC. Six pigs were fed
on each experimental diet ad libitum. Pigs were given ten days of the dietary adaptation period.
In Experiment 1, nitrogen (N) balance trial was conducted after thirty-one days of feeding pigs
with an average body weight of 30.7 kg ± 6.57. The collection of faeces and urine took place every
morning at 08h00 for five consecutive days. The hand-picking method was used to collect all
faecal material from each pen and those captured by a 1 mm sieve suspended underneath the pen.
Urine was collected using plastic trays and treated with 2 ml of sulphuric acid to reduce N
volatilisation. The collected samples were frozen at -20 ºC pending analyses. Nitrogen intake (NI),
total N excretion (TNE), urinary pH levels, N retention (NR), N absorption (NA), N digestibility
(ND), N utilization (NU), net protein utilization (NPU), and biological value of feed protein
(BVFP) were estimated. The average daily feed intake (ADFI), average daily gain (ADG), and
gain: feed (G: F) ratio were also estimated weekly.
There was a quadratic increase in ADFI (P < 0.05), while ADG (P < 0.05) and G: F ratio (P < 0.05)
increased linearly with incremental levels of ANC. Nitrogen (N) intake increased linearly with
ANC inclusion levels (P < 0.01). There was an increasing quadratic response in NA, apparent ND,
and NR in pigs fed on increasing levels of ANC (P < 0.05). A positive linear response in NPU and
BVFP to ANC inclusion was observed (P < 0.01). Nitrogen utilization increased at the rate of 0.63
g for each 1 g increase in ANC. There was a negative linear response in TNE through urine and
faeces as ANC inclusion increased (P < 0.01). The relationship between urinary pH levels and
ANC inclusion was described by the quadratic equation Y = 0.0115x2 - 0.3491x + 4.872 (P < 0.01).
In Experiment 2, apparent total tract digestibility (ATTD) of fibre and physicochemical
characteristics of colon digesta in growing Windsnyer pigs fed on ANC was determined. The
experimental diets were blended with 3 g chromium oxide (Cr2O3) and pigs were acclimatized to
this diet three days before the collection period. Representative feed samples for each diet were
stored at room temperature pending Cr2O3 analysis. Faecal material was collected using the grab
sampling method for five consecutive days between 08h00 and 13h00 and immediately chilled at
-20 °C for further analysis. Digestibility of dry matter (DMD), acid detergent fibre (ADFD), acid
detergent lignin (ADLD), hemicellulose (HemiD), and neutral detergent fibre (NDFD) were
determined. After the digestibility trial, pigs weighing 34 kg ± 6.25 kg were fasted for 24 hours
prior to slaughter, and routine abattoir procedures were followed. About 15 to 20 g digesta samples
were obtained from the proximal colon and frozen immediately at -20 ºC within 1 hour of
collection pending analysis. The DM content, pH level, water retention capacity (WRC), and
swelling capacity (SWC) in the colonal digesta were estimated. The digesta pH was determined
by inserting Crison 52 02 glass pH electrode immediately after collection. The WRC and SWC
were measured using the centrifugation method and modified bed volume technique, respectively.
There was a quadratic increase in DMD as ANC inclusion increased (P < 0.01). A positive linear
relationship between HemiD and increasing levels of ANC was observed (P < 0.01). There was
also an increasing linear response in NDFD as ANC inclusion increased (P < 0.01). Apparent
digestibility of ADF and ADL increased quadratically in response to ANC inclusion (P < 0.01).
There was an increasing quadratic relationship between digesta DM content and ANC inclusion
(P < 0.01). The digesta pH level decreased quadratically with ANC inclusion levels (P < 0.01).
The quadratic equation Y = -0.0017x2 + 0.0867x + 3.0929 and Y = 0.017x2 + 0.0389x + 2.9637
described the response in swelling capacity (SWC) (P < 0.01) and water retention capacity (WRC)
(P < 0.05) to ANC inclusion levels, respectively. It can be concluded that dietary ANC improves
N utilisation and fibre digestibility while reducing N excretion into the environment. Further,
fibrous ANC increases the physicochemical properties of colonal digesta, predicting increased
fibre fermentation. Hence, ANC can be a potential dietary protein source.
Keywords: ammonia volatilization, by-products, digesta properties, dietary fibre, digestion, dry
matter content, nitrogen absorption, nitrogen intake, nitrogen utilisation, swine, urinary pH level
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.