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Dairy
farmers continually
seek out feeds and diet mixes that allow
economical production for healthy cows. AAES studies suggest that both
an unconventional silage system and the use of cottonseed hulls in the
diet may provide new options for dairy producers. The proper balance
of forages and grains is not an easy task under favorable conditions but
often becomes more difficult in the Southeast because climatic conditions
and crops in the Southeast create difficulty in growing and harvesting
good quality hay. Harvesting and storing hay crops as silage are not affected
as much by climatic conditions as are haying procedures. However, many
farms are not properly equipped to store silage with conventional systems.
Various approaches to ensiling crops have been developed during recent
years, including a vacuum process to extract air from the plastic-sealed
silage crops that has been used for two to three seasons under practical
farm conditions at Alexandria, Alabama. However, crops ensiled with this
procedure have not been adequately evaluated under controlled conditions. Inclusion of
cottonseed hulls in diets has been beneficial under some conditions. However,
milk yield responses to rations containing cottonseed hulls are variable.
The objective of this investigation was to compare the effects of various
silages and cottonseed hulls on milk yield and composition. For the VAL
treatment, five vacuum system silage bags were filled. The silage was
piled (about seven by 20 feet) on top of plastic. Another sheet of plastic
was placed over the top of the silage and connected to all four sides
of the bottom sheet by rolling around a two-inch PVC pipe. The plastic
was secured to the PVC pipe with clamps and duct tape. A perforated PVC
pipe was placed on the bottom sheet of plastic prior to filling and extended
through the wrapped silo via a non-perforated PVC pipe. This pipe was
coupled to a vacuum pump. This silage was evacuated immediately after
ensiling and at daily intervals thereafter until opened for feeding. Treatment diets
were mixed and fed daily as a total mixed ration (TMR) for 75 days beginning
in mid June, 1998. Feed consumed was recorded for each cow, and treatment
diets were sampled periodically. Silages were analyzed for dry matter
(DM) at ensiling and sampled periodically throughout the experiment for
nutrient analyses. Diets were based on initial analyses. Cows were housed
in tie-stalls and milked twice daily at 1 a.m. and 1 p.m. Milk weights
were recorded daily, and milk was sampled the first week of each month.
Milk fat and protein were determined on individual milk samples by the
Southeast Dairy Laboratory in McDonough, Georgia. Cow body weights were
taken on two to three consecutive days prior to the study, at 45 days,
and at the end of the study. Nutrient
composition of the silages (Table
1) are typical of good quality silage for the different crops. The
Ag-Bag alfalfa silage was much drier than the other silages but the nutrient
content (DM basis) of the two alfalfa silages were very similar. Due to
the wide variation of nutrient content of the silages and in an attempt
to maximize the amount of silage used in the diets (Table
2), some variation existed in energy and protein content of the diets.
Protein content of all diets was increased to that supplied by the RG
treatment in order to minimize any possible protein differences. Energy
content was greater in the CS diets but the energy supplied in other diets
was considered adequate for the milk production at the start of the study.
Differences in CP, fibers, and minerals between the alfalfa, corn, and
ryegrass silages are consistent with known nutrient differences, relevant
to stage of maturity at harvest between legume and grass silage. Table
3 contains production results. Cows receiving VAL produced milk as
well as those receiving AgAL. These results indicated that the vacuum
method of ensiling is a satisfactory approach to ensiling crops. In this
study, the first VAL silo was opened within 40 days of ensiling and the
last at about 90 days after ensiling. The silage bags were vacuumed daily
until the bag was opened. The silage within each bag was fed out within
two to three weeks after opening with care to re-cover the bags after
each day’s feeding. All silage removed had a good visual appearance
with a "normal silage" odor. The effect of longer storage and
less frequent vacuuming on silage quality is not known. Additional laboratory
tests on the silage are in progress to help evaluate the silage system. Intake was lowest
on ryegrass diets and greatest on the AgAL diet. In contrast to earlier
studies, CSH did not improve intake in CS or RG diets. However, intake
was increased with the inclusion of CSH in alfalfa diets. Also, in contrast
to previous studies, CSH depressed milk production in the CS diets. Milk
production was improved by CSH in the alfalfa diets but did not affect
production for cows on ryegrass. No differences in milk fat percentage
were observed among cows fed the various silages, although supplementing
with CSH increased milk fat by 0.3-0.4 percentage units. Milk protein
percentage was lower for cows fed alfalfa silage or ryegrass silage with
CSH compared with that of cows fed corn silage. This may have been due
to the solubility of protein in the diets. The protein in grass and legume
silage is very soluble. It is logical to conclude that such protein was
absorbed from the rumen rapidly and not used to make as much milk protein.
Cows gained weight on all diets with cows fed corn silage without the
CSH supplement diet gaining the most. These results suggest that ensiling crops with a vacuum bag process may well provide as much milk production as when the crops are ensiled under more conventional methods. Additional information is needed on storing for extended times in these bags. Although alfalfa and ryegrass are high in protein, milk production may not be as good as with corn silage diets, probably due to usable energy. Use of cottonseed hulls may enhance production but results may not be consistent with different crops or seasons.
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