Evaluation of strategies for improvement of grass silage quality for smallholder dairy farmers in Tanzania
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Date
2017
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
Abstract
Silage production strategy has never been widely adopted by majority of dairy farmers in
Tanzania. On the other hand, most silage making technologies are expensive and not
technically viable under smallholder production. Studies which have been done in
developing cheap, practical and technically feasible silage making technologies
concentrated on a single dimensional approach of intervention, i.e. pre-ensiling
treatments, additives, others on ensiling amount and storage positions. Others dealt with
single grass leaving other potential locally available grasses uninvestigated. Studies
which specify the most appropriate combination of different techniques to achieve high
quality fodder grass silage under smallholder farmers have rarely been conducted. To
address these issues, six experiments were conducted in Magadu farm of Sokoine
University of Agriculture, Morogoro, Tanzania to evaluate the effectiveness of various
technologies used in fodder grass silage production under smallholder dairy farmers.
The first study dealt with determination of the effect of grass species, wilting and ensiled
amount in shopping plastic bags on silage quality. Elephant grass (Pennisetum
purpureum) and guatemala grass (Tripsacum laxum) were established and harvested
when they were 1.5 and 1 m tall respectively. One portion of grass was wilted for 24
hours and the other portion was unwilted before ensiling. Each portion was chopped into
4 cm particle length before ensiling. The chopped materials were ensiled either in
portions of 5 or 10 kg in plastic bag silos. Treatments were assigned to a completely
randomized design in factorial arrangement (2 x 2 x 2) as two grasses (elephant and
guatemala grasses), two pre-ensiling treatments (unwilted and wilted) and two ensiled
amounts (5 and 10 kgs) with two replications. The silage was opened and sampled after
60 days, analyzed for dry matter (DM) losses, chemical composition, fermentation and sensoric qualities and in vitro DM digestibility (IVDMD). The results showed that
elephant grass silage had higher (p< 0.05) sensoric scores, crude protein (CP), ash, lactic
acid (LA), acetic acid (AA) and bulk density (BD) but lower (p< 0.05) DM, water
soluble carbohydrate (WSC), IVDMD, pH, Ammonia Nitrogen (NH3N) and DM loss
than guatemala grass silage. Wilted fodder grass showed higher (p< 0.05) sensoric
scores, DM, CP, ash, WSC, pH, LA, AA and bulk density but lower Neutral Detergent
Fiber (NDF), NH3N, butyric acid (BA) and DM loss than unwilted fodder grass. The 5 kg
silage showed higher (p< 0.05) bulk density than 10 kg silage in plastic bag silo. There
was no difference between the two ensiled amounts (5 and 10 kg) in terms of appearance,
smell and texture scores, DM, CP, WSC, ash, NDF, IVDMD, pH, NH3N, LA, AA, BA
and DM losses.
The second experiment was conducted to investigate the effect of grass species and
different levels of maize bran on silage quality. Elephant grass, guatemala grass and
rhodes grass were established and harvested when they were at the age of 120, 63 and 56
days, respectively. Nutritive value declines quickly as plant matures thus were harvested
at respective recommended stages of growth for each grass. The harvested grasses were
chopped into 4 cm length and subdivided into four portions each of which was treated
with different level of maize bran (0, 5, 10 and 15%). The chopped materials were
ensiled in portions of 5 kg in plastic bag silo. Treatments were assigned to a completely
randomized design in factorial arrangement (3 x 4) as three grasses (elephant, guatemala
and rhodes grasses) and four maize bran levels (0, 5, 10 and 15%) with two replications.
The silage was opened after 60 days, sampled and analyzed for chemical composition,
fermentation, sensoric qualities, IVDMD and keeping quality stability. Elephant grass
produced higher (p< 0.05) quality silages than those produced by guatemala and rhodes
grasses as indicated by higher (p< 0.05) sensoric qualities, CP, LA and stability but lower (p< 0.05) pH and NH3N. Maize bran at 10% level produced higher (p< 0.05) quality
silages than maize bran at 0, 5 and 15% levels as indicated by higher (p< 0.05) sensoric
scores, CP, WSC, LA, AA and stability but lower (p< 0.05) NDF, pH and NH3N. The
interaction between grass species and different maize bran levels showed that, elephant
grass silage with maize bran at 10% level produced best silage as indicated by highest
sensoric scores, CP, LA and stability but lowest pH.
The third experiment focused on assessing the effect of grass species and different levels
of molasses on silage quality. The grasses were harvested when the re-growth was 1.5
and 1 m tall for elephant and guatemala grasses respectively and at flowering stage of
growth for rhodes grasses. The harvested grasses were chopped into 4 cm length and
subdivided into three portions each of which was treated with different levels of molasses
(0, 3 and 5%), packed in 5 kgs plastic bag silo and stored in thatched barn. Treatments
were assigned to a completely randomized design in factorial arrangement (3x3) as three
grasses (elephant, guatemala and rhodes grasses) and three levels of molasses (0, 3 and
5%) with two replications. The silage was opened and sampled after 60 days, analyzed
for sensoric qualities, chemical composition, IVDMD and fermentation. Elephant grass
produced higher quality silage and preserved better than guatemala and rhodes grasses as indicated by higher (p< 0.05) sensoric qualities, CP, ash, LA, AA and stability but lower
DM, pH, NH3N and BA. Silages produced from molasses at 5% level had higher
(p< 0.05) quality and preserved better than silages mixed with molasses at 0 and 3%
levels as indicated by higher (p< 0.05) DM, CP, WSC, ash, IVDMD, LA, AA and
stability but lower (p< 0.05) NDF, pH and NH3N. Elephant grass at 5% level of molasses
showed highest CP and WSC but lowest pH and NH3N. The fourth experiment aimed at
determination of the effect of wilting, chopping length and maize bran additive levels on
fodder grass silage quality. Elephant grass was harvested when the re-growth was 1.5 m
tall. The harvested grass was divided into two portions. One portion of grass was wilted
for 24 hours prior to ensiling while the other portion was ensiled unwilted. Before
ensiling each portion was chopped into either 2 or 4 cm length pieces using a machete.
Within each chop length (2 or 4 cm) the material was subdivided into four portions each
of which was treated with one of the four levels (0, 5, 10 and 15%) of maize bran.
Treatments were assigned to a randomized factorial design (4 x 2 x 2) as four maize bran
level (0, 5, 10 and 15%), two pre-ensiling treatments (wilted and unwilted) and two
chopped treatments (2 or 4 cm) with two replications. The silage was opened and
sampled after 60 days analyzed for; sensoric qualities, chemical composition, in vitro
DM digestibility, fermentation characteristics and stability. Wilted grass produced silages
with higher (p< 0.05) appearance, smell and texture scores, DM, CP, WSC, LA AA, pH
and stability but lower (p< 0.05) IVDMD, NDF, NH3N and butyric acid than unwilted
grass silages. Silages produced from 2 cm chop showed higher (p< 0.05) sensoric scores,
DM, CP, WSC and IVDMD, LA, AA and stability but lower (p< 0.05) NDF, pH, NH3N
and butyric acid than those from 4 cm chop. Silages treated with maize bran at 10 and
15% levels had higher (p< 0.05) DM, WSC and ash but lower (p< 0.05) NDF than the
other levels (0 and 5%). Silages treated with maize bran at 10% level had higher
(p< 0.05) sensoric scores, CP, IVDMD, lactic acid, acetic acid and stability but lower
(p< 0.05) NDF, pH, NH3N and butyric acids than the other levels (0, 5 and 15%). Wilting
with 2 cm chop and maize bran at 10% produced silage with highest IVDMD, CP and
acetic acid.
Experiment 5 dealt with the investigation of the effect of wilting, chopping lengths and
different levels of molasses on grass silage. Elephant grass (Pennisetum purpureum) was
harvested when the re-growth was 1.5 m tall. The harvested grass was divided into two
portions. One portion of grass was wilted for 24 hours prior to ensiling while the other portion was ensiled unwilted. Before ensiling each portion was chopped into either 2 or 4
cm length pieces using a machete. Within each chop size (i.e. 2 or 4 cm) the material was
subdivided into three portions each of which was treated with one of the three levels (0, 3
and 5%) of molasses as additive. Treatments were assigned to a randomized factorial
design (3 x 2 x 2) as molasses additive levels (0, 3 and 5%), two pre-ensiling treatments
(wilted and unwilted) and two chopping treatments (2 or 4 cm) with two replications. The
silage was opened and sampled after 60 days, analyzed for sensoric qualities; chemical
composition IVDMD, fermentation characteristics and stability. Wilted grass produced
silages with higher (p< 0.05) appearance, smell and texture scores, higher DM, CP,
WSC, ash, LA, AA, pH and stability but lower NDF, IVDMD, NH3N and BA than
unwilted grass silages. Silages produced from 2 cm chop showed higher (p< 0.05)
sensoric scores, DM, CP, WSC, IVDMD, LA, AA and stability but lower NDF, pH,
NH3N and BA than those from 4 cm chop. Silages treated with molasses at 5% level had
higher (p< 0.05) sensoric scores, DM, CP, WSC, ash, IVDMD, LA, AA and stability but
lower (p< 0.05) NDF, pH, NH3N and BA than silages treated with molasses at 0 and 3%
levels. Wilting with 2 cm chop and molasses at 5% produced silage with highest sensoric
scores, DM, WSC, LA but lowest NDF, pH and NH3N.
Experiment 6 dealt with determination of the effect of grass species, ensiled amount in
shopping plastic bags and storage positions on grass silage quality. The grasses were
harvested when the re-growth was 1.5 m and 1 m tall for elephant and guatemala grasses
and at flowering stage of growth for rhodes grasses. The harvested grasses were chopped
in 2 cm particle length before ensiling. The chopped materials were ensiled in portions of
5, 10 or 12 kg in plastic bag silos. Then the plastic bags were stored either in thatched
barn or in trench. Treatments were assigned to a completely randomized design in
factorial arrangement (3 x 3 x 2) as three grasses (elephant, guatemala and rhodes grasses), three ensiled amount of grasses in shopping plastic bag silos (5, 10 and 12 kgs)
and two storage positions (thatched barn and trench) with two replications. The silage
was opened and sampled after 60 days, analyzed for chemical composition, fermentation,
sensoric qualities, IVDMD and stability. Elephant grass produced higher (p< 0.05)
quality silage and preserved better than those of guatemala and rhodes grasses as
indicated by higher (p< 0.05) sensoric scores, CP, ash, LA, AA and stability but lower
(p< 0.05) pH, NH3N and butyric acid. The 5 and 10 kg ensiled amounts showed higher
(p< 0.05) appearance, smell and texture scores, DM, CP, WSC, ash, IVDMD, LA, AA
and stability but lower (p< 0.05) NDF, pH, NH3N and BA than 12 kg ensiled amounts.
There was no difference (p< 0.05) between the two ensiled amounts (5 and 10 kg) in
terms of appearance, smell and texture scores, DM, CP, WSC, ash, NDF, IVDMD, pH,
NH3N, LA, AA and BA. There were no differences (p< 0.05) between silages stored in
thatched barn and trench in terms of sensoric scores, DM, CP, WSC, ash, NDF and
IVDMD, pH, NH3N, LA, AA, BA and stability. It was therefore concluded that, wilted elephant grass chopped 2 cm, treated with either
maize bran at 10% or molasses at 5% levels, ensiled either at 5 or 10 kg in shopping
plastic bag silo, stored in either thatched barn or in trench was the most optimal
combination of technologies to achieve high quality grass silage.
Description
PhD THESIS
Keywords
Smallholder dairy farmers, Tanzania, Silage production, Pennisetum purpureum, Tripsacum laxum, Silage quality evaluation