The objective of this study was to
compare the standard methodology with an alternative method to
determine feed sorting in dairy cows during the transition period.
Twenty-six Holstein multiparous cows were paired by expected calving
date and fed diets containing either glycerol or high moisture corn
from -28 through +56 days relative to calving (DRTC). Feed sorting was
determined on -16, -9, +9, +15 and +51 DRTC in two different ways.
Firstly, it was determined as the actual intake of each screen of the
Penn State Particle Separator (PSPS) consumed between 0-4, 4-8, 8-12
and 12-24 hours post feeding, and expressed as a percentage of the
predicted intake of that correspondent screen. Secondly, by measuring
the particle size distribution of feed consumed between 0-4, 4-8, 8-12
and 12-24 hours post feeding. The total mixed ration (TMR) at feeding
and at each time post feeding was separated by size using the 3-screen
(19, 8, and 1.18 mm) Penn State Particle Separator (PSPS) to yield long
(>19 mm), medium (<19, >8 mm), short (<8, >1.18 mm), and
fine particles (<1.18 mm), respectively. Adding glycerol to the
prepartum diet increased (P<0.05) the proportion of DM% retained as
long particles (>19 mm) and reduced (P<0.05) the proportion of
DM% retained as short (<8, >1.18 mm) and fine particles (<1.18
mm), but it did not alter (P>0.05) the proportion of DM% retained as
medium particles (<19, >8 mm). Cows fed prepartum glycerol
increased (P<0.05) the preference for long particles (>19 mm)
according to the standard methodology (77.2 vs. 101.5%, control vs.
glycerol) and also in the alternative methodology (9.2 vs. 17.8%,
control vs. glycerol). Cows fed prepartum glycerol discriminated
against (P<0.05) short particles (<8, >1.18 mm) in the
standard methodology (102.6 vs. 94.2%, control vs. glycerol) as well as
in the alternative methodology (42 vs. 37.3%, control vs. glycerol).
There was no response (P>0.05) of diet on feed sorting of fine
particles (<1.18 mm) according to standard methodology during the
prepartum interval, but cows fed prepartum glycerol decreased
(P<0.05) the preference for fine particles (<1.18 mm) in the
alternative methodology (17.9 vs. 13.6%, control vs. glycerol). Cows
fed postpartum glycerol increased (P<0.05) the preference for medium
particles (<19, >8 mm) according to the standard methodology
(108.6 vs. 116.5%, control vs. glycerol), but did not (P>0.05)
according to the alternative methodology. Cows fed postpartum glycerol
discriminated against (P<0.05) short particles (<8, >1.18 mm)
according to the standard methodology (100.6 vs. 96.6%, control vs.
glycerol), but did not (P>0.05) according to the alternative
methodology. Feeding prepartum glycerol to transition dairy cows
increases the preference for the long-stem forage particles of the
diet. The alternative methodology proposed in this study is more
reliable than the standard methodology to determine feed sorting.
KEYWORDS: Biodiesel, byproduct, particle size, preference.
RESUMO
METODOLOGIA ALTERNATIVA NA DETERMINAÇÃO DO CONSUMO SELETIVO EM VACAS LEITEIRAS NO PERÍODO DE TRANSIÇÃO ALIMENTADAS COM GLICEROL
Objetivou-se, nesta pesquisa, comparar a metodologia-padrão com um novo
método alternativo na determinação do consumo seletivo em vacas
leiteiras durante o período de transição. Vinte e seis vacas multíparas
da raça Holandesa foram pareadas de acordo com a data prevista de
parição e alimentadas com dietas contendo glicerol ou milho grão de
alta umidade desde os -28 até +56 dias relativos à data de parição
(DRDP). Determinou-se o consumo seletivo aos -16, -9, +9, +15 e +51
DRDP por duas maneiras. Na primeira, com o consumo real de cada peneira
do Penn State Particle Separator (PSPS) entre 0-4, 4-8, 8-12 e 12-24
horas pós-alimentação, e expresso como a porcentagem do consumo predito
da peneira correspondente. Na segunda maneira, por meio da mensuração
da distribuição do tamanho de partículas do alimento consumido entre
0-4, 4-8, 8-12 e 12-24 horas pós-alimentação. Tanto no momento da
alimentação quanto em cada tempo pós-alimentação, a ração foi separada
por tamanho utilizando-se um conjunto com três peneiras (19, 8 e 1,18
mm) denominado Penn State Particle Separator (PSPS), gerando partículas
longas (>19 mm), médias (<19, >8 mm), curtas (<8, >1,18
mm) e muito curtas (<1,18 mm), respectivamente. A adição de glicerol
na dieta pré-parto aumentou (P<0,05) a proporção da %MS retida das
partículas longas (> 19 mm) e reduziu (P<0,05) a proporção da %MS
retida das partículas curtas (<8, >1,18 mm) e muito curtas
(<1,18 mm), mas não alterou (P>0,05) a proporção da %MS retida
das partículas médias (<19, >8 mm). Nas vacas alimentadas com
glicerol no pré-parto, houve aumento (P<0,05) da preferência pelas
partículas longas (>19 mm) na metodologia-padrão (77,2 vs 101,5%,
controle vs. glicerol) e também na metodologia alternativa (9,2 vs
17,8%, controle vs. glicerol). As vacas alimentadas com glicerol no
pré-parto discriminaram (P<0,05) as partículas curtas (<8,
>1,18 mm) na metodologia-padrão (102,6 vs 94,2%, controle vs.
glicerol) assim como na metodologia alternativa (42 vs. 37,3%, controle
vs. glicerol). Não houve efeito (P>0,05) de tratamento sobre o
consumo seletivo de partículas muito curtas (<1,18 mm) de acordo com
a metodologia-padrão na fase pré-parto, mas nas vacas alimentadas com
glicerol nessa fase houve diminuição (P<0,05) da preferência pelas
partículas muito curtas (<1,18 mm) na metodologia alternativa (17,9
vs. 13,6%, controle vs. glicerol). Nas vacas alimentadas com glicerol
na fase pós-parto, houve aumento (P<0,05) da preferência por
partículas médias (<19, >8 mm) de acordo com a metodologia-padrão
(108,6 vs. 116,5%, controle vs. glicerol), porém não houve efeito
(P>0,05) de tratamento sobre o consumo seletivo de partículas médias
(<19, >8 mm) na metodologia alternativa. As vacas alimentadas com
glicerol no pós-parto discriminaram (P<0,05) as partículas curtas
(<8, >1,18 mm) de acordo com a metodologia-padrão (100,6 vs.
96,6%, controle vs. glicerol), mas não houve resposta da dieta
(P>0,05) sobre o consumo seletivo de partículas curtas (<8,
>1,18 mm) na metodologia alternativa. A alimentação com glicerol
para vacas leiteiras no período de transição aumenta a preferência por
partículas longas (> 19 mm) da dieta durante o pré-parto. A
metodologia alternativa proposta neste estudo é mais confiável do que a
metodologia-padrão na determinação do consumo
seletivo.
PALAVRAS-CHAVES: Biodiesel, preferência, subproduto, tamanho de partícula.
INTRODUCTION
Cattle have the intrinsic ability to select specific and needed
nutrients when feeds are offered separately (STRICKLIN &
KAUTZ-SCANAVY, 1983). However, feeding dairy cows with rations in the
form of a total mixed ration (TMR) is a preferred practice compared
with component feeding systems on most dairy farms, but, despite the
aim of providing feed as a homogenous mixture in TMR, dairy cattle have
selectively consumed or sorted the grain component of a TMR and
discriminated against the longer forage components (LEONARDI &
ARMENTANO, 2003).
The periparturient or transition dairy cow has been defined when the
cow is between three weeks prepartum and three weeks postpartum
(GRUMMER, 1995). During this period of transition from gestation to
lactation the cow is at greater risk for developing metabolic and
infectious diseases than at any other time during its life (DRACKLEY,
1999). Therefore, special attention must be paid when formulating
diets, as well as feeding and nutritional strategies to minimize the
feed sorting behavior of dairy cows, which can result in the
consumption of a ration with inconsistent nutritive value (STONE, 2004)
and increasing risks of developing subacute ruminal acidosis (COOK
et al.,
2004; STONE, 2004), particularly when early lactating cows are fed low
forage diets. Likewise, the feed sorting behavior leads to variations
in nutritive values of the TMR in the feed bunk with a greater interval
of time post feed delivery (DEVRIES
et al.,
2005), especially when dominant and subordinate cows are grouped
together, where feed sorting by some groups of cows is also likely to
impact the nutritional value of feeds available for other cows in the
group, and may reduce the feeding value of the ration (KRAUSE &
OETZEL, 2006).
Several additions to rations fed as a TMR have been investigated in an
attempt to reduce feed sorting. The addition of water to a TMR has been
investigated to reduce feed sorting by decreasing discrimination
against long particles and reducing the preferential consumption of
short particles (LEONARDI
et al.,
2005a). However, a more recent study (MILLER-CUSHON & DEVRIES,
2009) demonstrated that the addition of water decreased DM intake and
increased sorting against long particles and increased preference for
short and fine particles. Molasses has been recognized for its property
to conglomerate small feed particles to larger particles. The addition
of molasses to corn silage based diets decreased feed sorting,
suggesting that molasses might be beneficial to enhance uniformity of
TMR consumption for group-fed cows (OELKER
et al.,
2009), and addition of molasses reduces the percentage of fine
particles found in calf starter (LESMEISTER & HEINRICHS, 2005).
Glycerol is a byproduct of the biodiesel industry that has been
currently produced by a reaction that utilizes a base-catalyzed
transesterification of oil in the formation of methyl and ethyl fatty
acid esters in the production of biodiesel (THOMPSON & HE, 2006),
and is a main byproduct of ethanol fermentation processing (MICHNICK
et al.,
1997). For each 100 g of soybean oil input, there is a yield of 12.25 g
of glycerol (THOMPSON & HE, 2006). Furthermore, glycerol has been
recently demonstrated to be a suitable primary feed ingredient to
replace corn grain in rations fed to mid-lactating dairy cows (DONKIN
et al., 2009).
Feed sorting has been previously measured according to LEONARDI &
ARMENTANO (2003) and several authors have also used later the same
methodology (LEONARDI
et al., 2005a; LEONARDI
et al., 2005b; DEVRIES
et al., 2007; BHANDARI
et al., 2008; DEVRIES
et al., 2008; HOSSEINKHANI
et al.,
2008). The objective of this study was to compare the methodology
according to LEONARDI & ARMENTANO (2003) with an alternative method
to determine feed sorting in periparturient dairy cows.
MATERIAL AND METHODS
Twenty-six Holstein multiparous were paired by expected calving date
and housed in individual tie stalls at the Purdue Dairy Research and
Education Center. Cows were randomly assigned to diets containing
either high moisture corn (control) or glycerol, and fed diets
formulated to meet or exceed the NRC (2001) guidelines for 600 kg dairy
cattle from -28 through +56 days relative to calving (DRTC). The
experiment was conducted between May/28/09 and October/23/09 and was
approved by the Purdue Animal Care and Use Committee.
The ingredients and nutrient composition of the pre- and post-partum diets are presented in
Table 1.
The diets were adjusted weekly to account for forage DM fluctuation.
The addition of soybean meal in the prepartum diet and the higher
participation of this ingredient in the postpartum diet were intended
to adjust for the protein that was removed with high moisture corn.
Diets were offered once daily from 06:30 to 07:30 for ad libitum intake
(10 to 15% weight backs). Feed refusals were measured daily and feed
intake was determined by difference.
Samples of corn silage, alfalfa haylage and TMR were collected weekly,
dried in a forced-air oven for 72 h at 55ºC and ground using a Willey
mill to pass a 1-mm screen. Composite samples were formed monthly and
analyzed by a commercial laboratory (Dairy One, Ithaca, NY) for DM,
crude protein (CP), acid detergent fiber (ADF), starch and minerals by
wet chemistry following AOAC (2000) procedures, and for NDF following
the method of GOERING & VAN SOEST (1970).
Feed sorting was determined at -16, -9, +9, +16 and +51 DRTC (targeted
days) by two methodologies. In both, samples of diets were taken at 0,
4, 8, 12 and 24 hours after feed delivery and frozen at -20ºC. Upon
thawing, samples were separated using the 3-screen (19, 8, and 1.18 mm)
Penn State Particle Separator (PSPS) to yield long (>19 mm), medium
(<19, >8 mm), short (<8, >1.18 mm) and fine (<1.18 mm)
particles (LAMMERS
et al.,
1996). Post separated materials were then dried in a forced-air oven
for 72 h at 55ºC. Feed sorting was determined according to LEONARDI
& ARMENTANO (2003) as the actual intake of each screen of the PSPS
consumed between 0-4, 4-8, 8-12 and 12-24 hours post feeding, and
expressed as a percentage of the predicted intake of that correspondent
screen. The actual intake for each individual particle size equals the
product of the DMI between 0-4, 4-8, 8-12 and 12-24 hours post feeding
multiplied by the particle size distribution within the same intervals,
whereas the predicted intake for each individual particle size equals
the product of the DMI between 0-4, 4-8, 8-12 and 12-24 hours post
feeding multiplied by the particle size distribution of the offered
TMR. The final outcome is that values equal to 100% indicate no
sorting, <100% indicate selective refusals (sorting against), and
>100% indicate preferential consumption (sorting for). In the
alternative methodology proposed in this study, feed intake of the
individual particle sizes during each interval was determined by
subtracting the particle size distribution available at the beginning
of each interval from the particle size distribution remaining at the
end of the interval, and feed sorting was determined by measuring the
particle size distribution of feed consumed between 0-4, 4-8, 8-12 and
12-24 hours relative to feed delivery.
The data were analyzed using the MIXED procedure (SAS, 1999). The model
accounted for the effects of treatments, DRTC and times post feeding
(4, 8, 12 and 24 h), as well as the interaction effect of treatment by
DRTC, treatment by time, DRTC by time and treatment by DRTC by time.
Means were different if P<0.05 and values are reported as least
square means and associated standard errors.
RESULTS
Twenty-three cows completed the study (12 in the glycerol group and 11
in the control group). Two cows were removed due to displaced abomasum
just after parturition (3935, control group and 4090, glycerol group)
and one cow (3846, control group) experienced uterine torsion 7 days
prior to parturition. Data from these cows were used in the prepartum
parameters. Actual means and associated standard deviations of feed
sorting sampling days were -16 (±3.6), -9 (±3.7), +11 (±1.6), +18
(±2.4) and +53 (±1.8) DRTC. Feed intake did not differ (P>0.05)
between treatments and was 14.7 ± 0.4 and 20.2 ± 0.5 kg/d for the pre-
and post-partum intervals, respectively.
There was effect of treatments on the particle size distribution of the
prepartum experimental diets. Adding glycerol increased (P<0.05) the
proportion of DM% retained as long particles (>19 mm). Contrarily,
the proportion of DM% retained as short (<8, >1.18 mm) and fine
(<1.18 mm) particles was reduced (P<0.05) with glycerol
inclusion. There was no response (P>0.05) to prepartum glycerol on
the proportion of DM% retained as medium particles (<19, >8 mm)
and no response (P>0.05) of treatments on the particle size
distribution of the postpartum diets (
Table 2).
Results of feed sorting according to the methodology from LEONARDI & ARMENTANO (2003) are presented in
Figures 1 and
2, whereas according to the alternative methodology proposed in this study are shown in
Figures 3 and
4.
Cows fed prepartum glycerol increased (P<0.05) the preference or
sorting for long particles (>19 mm) according to the methodology by
LEONARDI & ARMENTANO (2003) (77.2 vs. 101.5%, control vs. glycerol,
Figure 1) and also in the alternative methodology (9.2 vs. 17.8%, control vs. glycerol,
Figure 3).
There was no response (P>0.05) of treatments on feed sorting of
medium particles (<19, >8 mm) during the prepartum period in both
methodologies (116 vs. 117.4%, control vs. glycerol, LEONARDI &
ARMENTANO, 2003,
Figure 1; 30.9 vs. 31.3%, control vs. glycerol, alternative methodology,
Figure 3).
Cows fed prepartum glycerol discriminated or sorted against (P<0.05)
short particles (<8, >1.18 mm) in both methodologies (102.6 vs.
94.2%, control vs. glycerol, LEONARDI & ARMENTANO, 2003,
Figure 1; 42 vs. 37.3%, control vs. glycerol, alternative methodology,
Figure 3).
Conversely, there was no response (P>0.05) of diet on feed sorting
of fine particles (<1.18 mm) according to the methodology by
LEONARDI & ARMENTANO (2003) (78.3 vs. 76.1%, control vs. glycerol,
Figure 1),
but cows fed prepartum glycerol decreased (P<0.05) the preference
for fine particles (<1.18 mm) in the alternative methodology (17.9
vs. 13.6%, control vs. glycerol,
Figure 3).
Feed sorting during the postpartum interval did not differ (P>0.05)
between treatments in both methodologies for long particles (>19 mm)
(98.6 vs. 108.9%, control vs. glycerol, LEONARDI & ARMENTANO, 2003,
Figure 2; 5.8 vs. 7%, control vs. glycerol, alternative methodology,
Figure 4).
However, cows fed postpartum glycerol increased (P<0.05) the
preference for medium particles (<19, >8 mm) according to the
methodology by LEONARDI & ARMENTANO (2003) (108.6 vs. 116.5%,
control vs. glycerol,
Figure 2), but did not (P>0.05) according to the alternative methodology (36.1 vs. 37%, control vs. glycerol,
Figure 4).
Conversely, cows fed postpartum glycerol discriminated against
(P<0.05) short particles (<8, >1.18 mm) according to the
methodology by LEONARDI & ARMENTANO (2003) (100.6 vs. 96.6%,
control vs. glycerol,
Figure 2), and again did not (P>0.05) according to the alternative methodology (42.2 vs. 41.6%, control vs. glycerol,
Figure 4).
There was no effect (P>0.05) of diet on feed sorting of fine
particles (<1.18 mm) in both methodologies (85.4 vs. 72.4%, control
vs. glycerol, LEONARDI & ARMENTANO, 2003,
Figure 2; 15.8 vs. 14.4%, control vs. glycerol, alternative methodology,
Figure 4).
DISCUSSION
The response to prepartum glycerol on the preference for long particles
(>19 mm) in both methodologies can be explained by the fact that the
proportion of DM retained as long particles (>19 mm) in the
prepartum glycerol diet was increased compared with the prepartum
control diet (
Table 2).
This happened because the glycerol adhesive property increased the
weight only of the long particles (>19 mm) of the prepartum diet,
but not of the medium (<19, >8 mm), short (<8, >1.18 mm)
and fine particles (<1.18 mm), and yet, no effect of glycerol
coating was observed on the particle size distribution of the
postpartum diet. Thus, it can be inferred that the greater response to
glycerol coating on the long particles (>19 mm) was related to a
higher proportion of long-stem forage in the glycerol prepartum diet
(13% of hay of the total DM ration) compared with the glycerol
postpartum diet (3.5% plus 1.5% of hay and straw of the total DM
ration, respectively), which may have resulted in a greater density of
the long particles (>19 mm) due to more surface exposure for
glycerol coating on the long-stemmed forage.
As mentioned previously, several authors (LEONARDI & ARMENTANO, 2003; LEONARDI
et al., 2005a; LEONARDI
et al., 2005b; DEVRIES
et al., 2007; BHANDARI
et al., 2008; HOSSEINKHANI
et al.,
2008) reported that dairy cows have an intrinsic behavior to
discriminate against long (>19 mm) and sort for fine particles
(<1.18 mm) of the diet. Taking into account only the results
obtained according to the methodology by LEONARDI & ARMENTANO
(2003), cows in this study discriminated against fine particles
(<1.18 mm) regardless of diets consumed, during both the pre- and
post-partum intervals. This finding is rather difficult to explain, but
DEVRIES
et al. (2007)
speculated that the reason why dairy cows were more eager to increase
the preference for short particles (<8 mm) was the
forage:concentrate ratio of the diets. In that study, one group of cows
was fed a lower forage diet (50.7% forage:49.3% concentrate; DM basis),
while the other group was fed a higher forage diet (62.3% forage:37.7%
concentrate; DM basis). The authors reported that cows from both groups
demonstrated preference for short particles (<8 mm), but the degree
of sorting was more pronounced in cows fed the lower forage diet,
simply because the concentrate content was more accessible and easier
to sort. However, in the present study the forage:concentrate ratios of
the pre- and post-partum diets in both treatments (56.4:43.6 and
59.5:40.5 of the total DM, respectively) were closer to the
forage:concentrate ratio of the higher forage diet used by DEVRIES
et al.
(2007), but cows in this study had a high degree of discrimination
against fine particles (<1.18 mm), indicating that this result was
not related to the forage:concentrate ratio of diets.
Overall, discrepancies of determinations of feed sorting between
methodologies occurred three times. During the prepartum stage, there
was no effect of treatments on feed sorting of fine particles (<1.18
mm) according to the methodology by LEONARDI & ARMENTANO (2003),
but cows fed glycerol decreased the preference of those particles
according to the alternative methodology. During the postpartum
interval, cows fed glycerol increased the preference for medium
particles (<19, >8 mm) according to the methodology by LEONARDI
& ARMENTANO (2003), but did not according to the alternative
methodology, as well as cows fed glycerol discriminated against short
particles (<8, >1.18 mm) according to the methodology by LEONARDI
& ARMENTANO (2003), and again did not according to the alternative
methodology.
Finally, it can be stated that the alternative methodology proposed in
this study is more reliable than the standard methodology based on the
fact that feed sorting was determined as the particle size distribution
relative to feed intake of the individual particle sizes during each
interval, and considering the amount of feed that was available to the
cow exclusively in the beginning of each interval as a baseline to
determine feed sorting in the end of each interval. However, LEONARDI
& ARMENTANO (2003) considered the predicted intake as a baseline to
determine feed sorting, and the problem is that cows will always sort
for or against the different components of the diet over the course of
the day, and consequently alter the particle size profile of the TMR,
thereby impacting the results of feed sorting in the end of the first
interval and also in the following intervals. Another strong reason to
corroborate that the alternative methodology may be more accurate is
that cows fed prepartum glycerol had significant differences on feed
sorting only when there were significant variations on the particle
size distribution of the experimental diets (
Table 2).
As reported previously, the addition of prepartum glycerol increased
the DM proportion of long particles (>19 mm) and decreased the DM
proportion of short (<8, >1.18 mm) and fine (<1.18 mm)
particles. Likewise, cows fed prepartum glycerol increased the
preference for long particles (>19 mm) and decreased the preference
for short (<8, >1.18 mm) and fine (<1.18 mm) particles. The
same pattern was observed during the postpartum interval, when there
was neither effect of diet on the particle size distribution of the
experimental diets, nor on feed sorting according to the alternative
methodology. Nonetheless, additional research is needed to investigate
whether or not the alternative methodology proposed in this study will
bring the same kind of results through experiments using cows fed
ingredients other than glycerol that do not have adhesive properties on
long-stemmed forage particles.
CONCLUSIONS
The glycerol adhesive property enhanced the preference for the long
particles (>19 mm) of the diet during the prepartum interval, which
may prove to be beneficial to rumen health.
The alternative methodology proposed in this study is more reliable
than the standard methodology in the determinations of feed sorting.
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Protocolado
em: 27 abr. 2010. Aceito em: 15 out.
2010.