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Development of an Appropriate Technology for Enhancing Nutritional Worth of Crop Residues for Dairy Production in Pakistan
Department of Animal Nutrition, University of Agriculture, Faisalabad. The basic
reason for poor productivity of dairy animals in Pakistan is the limited supply of good
quality fodders in sufficient amount. That is why our dairy animals are fed diets high in
cereal straws (wheat straw, rice straw, corncobs etc) The carbohydrates of these
straws are of low digestibility
(less than 40%) and they are usually low in crude protein and often deficient in minerals required by animals. The efficient function of the digesting milieu of microorganisms in the rumen is critical to the feeding value of forages containing carbohydrates largely indigestible by gastro-intestinal enzymes.
The level of production of ruminants on these feeds depends on appropriate nutritional
manipulation to optimize digestive function and to balance availabilities of nutrients as close as possible to nutrient requirements. A number of plant, animal and
environmental factors, however, interact to determine the level of animal production
and the nutritional value of a feed. The ability of these crop residues to support
reasonable levels of ruminant production can be achieved by supplementing these poor quality straws with protein and energy sources, but it is very
costly and can render the livestock keeping an expensive enterprise for a
common farmer in Pakistan. Thus, there is a dire need to undertake some
appropriate nutritional research involving mainly locally available feed
resources and how their nutritional value can be optimized.
One of the feasible alternatives may be to chemically upgrade the feeding value of
straws, as the chemical treatment has the potential to increase the feed intake and nutrient digestibility by the ruminant animals. Various chemicals like sodium hydroxide, ammonia, alkaline hydrogen peroxide and urea have been used for upgrading these poor quality cereal straws. Among the various chemicals employed for the treatment of cereal straws, ammonia (NH3) an alkali has shown good results, but ammoniations of straw using gaseous or aqueous NH3 have their inherent
problems of being costly and tedious to transport. Urea, a cheap source of NH3 after
hydrolysis, has given satisfactory results as far as the improvement in nutritive value
of wheat straw is concerned. Appropriate nutritional research for development
considers mainly locally available feed resources and how their nutritional value can be optimized.
Usage of urea as a source of NH3 is not a perfect method, as the NH3 liberated from urea because of action of ureolytic organism is not fully fixed in the wheat straw. The urea treated wheat straw only retained about 30-35% of NH3 added to the straw during treatment and the remaining 65-70% was lost to the atmosphere. This escaped NH3 is not only a significant nitrogen (N) loss but it also causes atmospheric pollution.
Thus, it is imperative to devise some methods, which can help save or minimize this
major loss of NH3 to the atmosphere. To overcome these problems, the corn
steep liquor (CSL), a byproduct of maize industry, may offer a solution to
the problem of escaping NH3 and poor fermentation of urea treated wheat
straw. Because it does not only contain easily soluble carbohydrates, which
can improve fermentation, but it's acidic pH can also help fix the excess
NH3. Thus, the use of this feed ingredient alone can enhance both the
fermentation process and NH3 fixation in the ensiled urea treated wheat
straw. However, the scientific evidence regarding this effect on the NH3
fixation in the urea treated ensiled wheat straw and its nutritional value is limited.
The objectives of this research project were to examine the influence of
corn steep liquor (CSL) on nitrogen (N) retention in urea treated wheat
straw and its dietary effects on intake, ruminal characteristics, in situ
digestion kinetics, N metabolism, nutrients digestion, milk yield and its
composition in buffaloes. The hypothesis was that ensilation of urea treated
wheat straw with CSL can enhance both the N retention in the straw and its
feeding value without adversely affecting rumen functions, N metabolism and
lactation performance of buffaloes.
The CSL was added to 5 % urea treated wheat straw at 0, 3, 6, and 9% on dry matter (DM) basis. This treated straw was ensiled in laboratory silos for 5,
10 and 15 days and after opening of these silos, it was revealed that
neutral detergent fibre (NDF) contents of urea treated wheat straw ensiled
with 0, 3, 6 and 9% CSL were 74.01, 76.16, 77.34 and 78.93 %, respectively,
but the concentration of acid detergent fibre (ADF), cellulose and lignin
remained unaffected. The increase in NDF was because of increased neutral
detergent insoluble nitrogen (NDIN), when NDF was calculated on a CP-free
basis (NDF-NDIN X 6.25), its concentration remained unaltered between urea
treated wheat straw ensiled with or without CSL. The N contents of urea
treated wheat straw ensiled with 0, 3, 6 and 9% CSL were 1.03, 1.55, 1.83
and 2.17%, respectively.
A significant (P<0.05) increase in N content of urea treated wheat straw ensiled with CSL was noticed when compared to urea
treated wheat straw ensiled without CSL. The urea treated wheat straw
ensiled with 3, 6, and 9% CSL increased 50, 78 and 111% wheat straw N when
compared to urea treated wheat straw without CSL. In the present study,
urea treated wheat straw ensiled with CSL has approximately doubled
the N contents when compared to urea treated straw without CSL.
The urea treated wheat straw was ensiled at a large scale for 5 days. The
varying levels of this ensiled urea treated wheat straw was used to
formulate rations. Two metabolic trials (restricted and ad libitum) were
conducted to examine the influence of urea treated wheat straw ensiled with
or without CSL on feed intake, ruminal characteristics, digestion kinetics,
N metabolism and nutrient digestibility by ruminally cannulated buffalo
bulls.
The 5 kg urea was dissolved in 50-liter water with or without CSL and this solution was uniformly sprayed on 100 kg wheat straw. This treated
wheat straw was put into four different cemented pits and ensiled for a
period of 15 days with air temperatures of 35-45°C. In the control pit, the
wheat straw was treated with 5% urea only. In the second, third and fourth
pit, 3, 6 and 9% CSL on DM basis was added, respectively, to the 5% urea
treated wheat straw. Each pit was covered with 4 inches thick layer of rice
straw, followed by the plastic film covering which was plastered with a
blend of wheat straw and mud to avoid any cracking on drying. Four diets
were formulated to contain 20 % concentrate and 80% urea treated wheat straw
ensiled with or without CSL. The urea was used to make all diets
iso-nitrogenous. Four buffalo bulls, each weighing 350 kg, fitted with
ruminal cannulae, using 4x4 Latin Square Design, were used. All diets were
mixed daily and fed twice daily at .75% of body weight for each feeding in
restricted fed trial that lasted for 68 days. In the ad libitum trial, animals were fed free of choice for 68 days. For each trial, the first 10
days were given for adaptation to the new feed followed by 7 days of sample
collection in each period. Data were analyzed as a 4 x 4 Latin square design
with factorial arrangement of levels of CSL and duration of ensiling
treatments.
Dry matter, digestible DM, OM, CP, ADF and NDF intakes were the highest in
animals fed diets containing urea treated wheat straw ensiled with 9% CSL
and was the lowest in animals fed diets containing urea treated wheat straw
ensiled without CSL in ad libitum trial. A significant increase both in DM
disappearance and rate of disappearance and a reduction in lag time of urea
treated wheat straw ensiled with CSL was noticed. There were significant
differences in ruminal ammonia (NH3) concentrations between diets containing
urea treated wheat straw ensiled with or without CSL at 3, 6 and 12 h
sampling periods.
The concentrations of total ruminal volatile fatty acids (VFA), acetate, total, viable
and cellulolytic bacteria were higher in the
rumens of animals fed diets containing urea treated wheat straw ensiled with
CSL than those fed diets containing urea treated wheat straw ensiled without
CSL. The cellulolytic bacteria were isolated at higher dilutions (p<. 05) in
animals fed diets containing 3, 6 and 9% CSL than those fed diets without
CSL. The animals fed diets containing urea treated wheat straw
ensiled with
9% CSL had the highest concentration of these bacteria whereas the lowest
concentration was noticed in animals fed diets containing urea treated wheat
straw ensiled without CSL.
A significant increases both in NDF degradation and rate of disappearance of urea treated wheat straw ensiled with CSL may
be because of enhanced cellulolytic bacteria in the rumen of animals fed
diets containing CSL. Nitrogen balance was positive for all animals;
however, the animals fed diets containing CSL retained the highest amount of
N than those fed diets without CSL. Urinary N excretion was the lowest in
animals fed diets containing CSL than those fed control diet. The lower
blood urea N in buffalo bulls fed diets containing urea treated wheat straw
with CSL implies slower release of NH3 in the rumen. The diets containing
CSL treated wheat straw promoted the greatest N retention.
Digestibilites of DM, OM, NDF and ADF were higher in animals fed diets containing urea treated
wheat straw ensiled with CSL than those fed diets containing urea
treated
wheat straw ensiled with 0% CSL. Thus, the ensiling of urea treated wheat
straw with all levels of CSL was more effective in improving the nutritional
quality of straw than that ensiled without CSL, however, the 9% CSL gave the
best results. This suggests that CSL can effectively be used to enhance the
nutritional worth of poor quality crop residues.
In conclusion, urea treated wheat straw ensiled with CSL on average
increased two-fold wheat straw nitrogen. It has also increased feed intake,
DM and NDF degradations and their ruminal disappearance rates. The
concentrations of total ruminal VFA and acetate were also higher in animals
fed CSL diets than those fed diets without CSL. Thus, the urea treatment of
wheat straw ensiled with CSL not only improved its nutritional worth but its
non-protein nitrogen was also utilized more effectively by animals than
those fed urea treated wheat straw ensiled in the absence of CSL.
In lactation trial, sixteen early lactating Nili-Ravi buffaloes, four
animals in each group, were used in a Completely Randomized Design to
evaluate the effect of varying levels of 5% urea treated wheat straw ensiled
with or without CSL on feed intake, digestibility and milk production and
its composition. Four experimental diets were formulated and urea treated
wheat straw ensiled with or without CSL was the roughage used in the
experimental diets.
The WS35 diet was balanced to contain 35% urea treated wheat straw ensiled with 0
% CSL and WS45, WS55 and WS65 diets were
formulated to have 45, 55 and 65% urea treated wheat straw ensiled with 9%
CSL, respectively. All diets were formulated to be iso-nitrogenous and
isoenergetic. Diets were mixed daily and fed twice a day at ad libitum
intakes. The buffaloes were fed for 40 days. The first 10 days were allowed
for dietary adaptation and 30 days were for sample collection. Daily feed
intake and milk production were averaged over 30 days. Milk samples (a.m. &
p.m.) were collected twice weekly during the last 30 days of feeding trial
and were analyzed for crude protein, fat, solid not fat, total solids and
ash.
The acid insoluble ash was used as digestibility marker. The data collected were analyzed according to Completely Randomized Design.
Dry matter intakes by buffaloes remained similar across all treatments.
However, DM as a percent of body weight and digestible DM intakes were
higher in WS65 diet when compared to WS35, WS45 and WS65 diets. The
increased intake of digestible DM may be attributed to enhanced
digestibility of NDF. Neutral detergent fibre intakes remained unaltered
across all diets however, NDF intake as percent of body weight was
significantly higher in WS55 diets and was the lowest in WS45
diets.
However, digestible NDF intakes were also significantly higher for WS65 diet as compared to all other diets. The intakes of ADF and digestible ADF were higher for WS55 and WS65 than WS35 and WS45 diets. The significant variation in digestible DM, ADF and NDF intakes may be attributed to the ammoniation of wheat straw along with CSL that caused significant changes in the
degradability and digestibility of the diets. Crude protein intake remained
unaltered among all treatments. Similarly, digestible crude protein intake
was also similar for all treatments. Ether extract and digestible EE intakes
differed significantly (p<. 05) among all treatments. Intakes of EE were the
highest in animals fed WS65 diet, which was because of added fat to make it
is caloric.
The apparent DM digestibility was statistically significant across all
diets. Apparent DM digestibility was the highest in WS35 diet and was the
lowest in WS45 diet. However, the higher DM digestibility in WS35 diets can
be ascribed to its low forage to concentrate ratio. Neutral detergent fibre
and ADF digestibilities were higher in animals fed diets containing urea
treated wheat straw ensiled with 9% CSL when compared to those fed diets
containing urea treated wheat straw ensiled with 0% CSL. Ammoniation
probably has caused reduction in the concentration of aromatic compounds in
treated material, which might have improved the fiber digestibility.
Apparent digestibility of CP was significantly different across all diets.
The highest (71.47%) value was noted in animals fed WS65 diet when compared to those fed WS55 (67.75%), WS45 (67.04%), and WS35 (65.39%) diets. These results indicated that CSL was very effective that enhanced the utilization
of N by minimizing N loss at ruminal level. Milk yield (4% FCM) was the higher in buffaloes fed WS65, WS55 and WS45
diets than those fed WS35 diet. A tendency for a linear increase in milk
production by cows fed diets with decreasing NSC concentration may be
attributed to increasing fat in the diet to maintain NEL in the experimental diets. However, true protein and non-protein nitrogen, as percentage of milk
protein did not show any treatment affect. Percent milk fat; SNF and total
solid remained unchanged across all treatments.
In conclusion, feeding of urea treated wheat straw ensiled with 9% CSL had
no adverse effect on the milk yield and its composition. However,
digestibility and ruminal data from short term trials are considered
reliable, but lactation performance should be tested in continuous lactation
trial (s) for long enough time to determine actual effects of formulating
diets using fairly high (65%) level of urea treated wheat straw ensiled with
CSL on milk yield and its composition, body weight loss and feed efficiency.
Therefore, more information is needed before these diets should be
recommended for use by the dairy farming community.
Courtesy Business Recorder
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