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Decision on BCAA requirement for Thoroughbreds using the IAAO
method (2007-2008)
Branched
chain amino acids (BCAA: valine, leucine and isoleucine) are
essential amino acids that play an important role in the metabolism
of muscle protein. However, the respective requirements of these
are not specified in Japanese light breed horse feeding
standards or in the 2007 NRC Feeding Standards published in the
USA. Conversely, a method of measuring the BCAA requirement in
humans has already been established using the indicator amino
acid oxidation (IAAO) method. Therefore, this IAAO method was
used to investigate the BCAA requirement in horses. As a result,
it became clear that the BCAA requirement for horses when at
rest is 179mg/kg/day.
Evaluation and improvement
of vitamin K nutrition status associated with growth in light
breed horses: Preparation of guidelines on vitamin K requirement
needed for bone formation (2006-2008)
(Commissioned research conducted by Kyoto University)
Vitamin
K (particularly menaquinone-4) is an essential vitamin for healthy
bones, but the concentration of VK homologues in equine plasma
needed to evaluate the vitamin K nutrition status has not previously
been measured. In this study, the concentration of VK homologies
in plasma was measured and a method of vitamin K supplementation
was studied. Phylloquinone, menaquinone-4, menaquinone-7 and
menadione supplementation tests were carried out on adult horses,
whereupon it became clear that only menadione at 0.12 μmol/kg body weight/day, far less than
the toxic dose, can efficiently raise the menaquinone-4 concentration
in plasma. Also, supplementing mothersﾕ
feed with menadione raised the menaquinone-4 concentration in
plasma of nursing foals. It was also suggested that the nutritional
significance of menaquinones synthesized in the digestive tract
is small.
Search for pregnancy marker
substances in mares (2006-2008)
(Commissioned research conducted by University of Tokyo)
Pregnancy
marker substances have yet to be identified in mares. In this
study, the following four phenomena were posited as implantation
phenomena: (1) embryo mobility and suppression of regression
of the corpus luteum, (2) attachment of the embryo to the uterus
wall, (3) regulation of calcium concentration in the uterus after
capsule loss, and (4) preparation of an immune environment for
the uterus. Next, using subtraction and the DNA microarray method,
factors related to the four implantation phenomena were identified,
and their localization, expression control and functions were
analyzed. Finally, to develop a method of controlling these factors,
a system for in vitro tissue and cell culture analysis
was also developed.
Research on the content of
water-soluble carbohydrates in pasture grasses used for light
breed horses (2007-2008)
(Commissioned research conducted by Obihiro University of Agriculture
and Veterinary Medicine)
Causes
of fluctuation in the content of water-soluble carbohydrates
in pasture grasses used for light breed horses were studied,
together with the influence of this content on the properties
of horse feces in open pastures. The content of water-soluble
carbohydrates in pasture grasses fluctuated not only in accordance
with the type and growth stage of the grass, but also between
different times of day (it was higher in the evening than in
the morning). The pH of horse feces in open pastures was lower
in spring than in summer and autumn, and in open pastures where
supplementary feed was not given, the pH of feces was 6.0 or
less. The pH of feces was lower in spring than in summer and
autumn, falling below 6.0 at one point, and it was surmised that
in spring, acidosis in the hind gut is more prone to occur than
in summer and autumn. Nevertheless, the content of water-soluble
carbohydrates in open pasture grasses was in some cases not so
high in spring as in summer and autumn. It was therefore suggested
that, besides the content of water-soluble carbohydrates in pasture
grasses, there may be other factors that change the fermentation
properties inside the hind gut.
Studies on training and management
of yearling horses (2002-2006)
Purpose
To
study new guidelines for training techniques based on scientific
indicators of aerobic exercise ability and bone metabolism.
Results
1.
Evaluation of V200 values among JRA yearlings in Hidaka and Miyazaki
Traing Fram:
We
measured the V200 of JRA yearlings in Hidaka and Miyazaki that
were sold between 2002 and 2006 (192 colts, 155 fillies) in February
and April of the 2nd year. As a result, V200 rose significantly
between February and April in both yearling farms, although the
values for Miyazaki tended to be higher than those for Hidaka.
To study the relationship between aerobic exercise ability and
exercise intensity of yearlings in more detail, moreover, we
investigated the V200 of horses sold between 1999 and 2006 in
February and April of the 2nd year. As a result, we were able
to conveniently classify the period from 1999 to 2002 as one
in which gentle exercise load was imposed in the first half of
the training and the exercise load was intensified in the finishing
stages (ﾒThe type of higher
exercise intensity in the latter half during the yearlingﾕs trainingﾓ),
and the period from 2003 to 2006 as one in which heavy exercise
load was imposed from the first half to improve physical fitness
(ﾒThe type of higher exercise
intensity in the first half during the yearlingﾕs trainingﾓ).
In fact, yearlings subjected to the latter of these two training
patterns tended to enter races at an earlier age. From this it
was thought that this pattern makes it possible to mitigate the
increase in exercise intensity in the second half of the training,
making yearlings more easily adaptable to training after entering
the Training Centers.
2.
Changes in bone mineral content associated with training progress:
On
investigating changes in bone mineral content associated with
training progress in private yearling farms, no difference was
found in bone mineral content in June of the 2nd year between
farms that imposed heavy exercise and moderate exercise load.
However, in December of the 1st year, when the study was started,
there were some farms in which bone mineral content was larger
than in other yearling farms.
In a separate study, night and day grazing before training by
riding in the field was effective in improving aerobic exercise
ability. Therefore, taking this into account at the same time,
exercise in the appropriate period was thought important for
bone growth and building up fitness in the yearling phase.
3.
The impact of treadmill exercise on yearlings:
Since
high intensity exercise in winter can easily cause injuries to
the locomotive organs of mares, we used research horses for training
by riding in the field, in conjunction with high intensity exercise
using a treadmill (TM) to avoid the load associated with field
riding (once a week from February of the 2nd year, intensity
close to all-out), and investigated the impact. As a result,
the V200 of research horses in April of the 2nd year was significantly
higher than that of JRA yearlings trained only by riding in the
field. From this, we understood that TM exercise in the training
phase is effective in improving aerobic exercise ability, and
that the aerobic exercise ability obtained from conventional
training by riding in the field alone does not necessarily reach
its maximum potential in the training phase. On the other hand,
TM exercise given to yearlings was thought to entail a number
of problems, such as the possibility that it could have an adverse
effect on building up running form.
4.
Relationship between the V200 and fat-free mass of horses in
the training phase:
A
significantly positive correlation was seen between V200 and
fat-free mass in April of the 2nd year, and we found that fat-free
mass is valid as a new method for estimating aerobic exercise
ability.
Conclusions
1.
Increasing physical fitness from the first half of the training
phase makes it easier to adapt to high intensity exercise in
the second half (is effective in building up physical fitness).
2.
For bone growth and improved fitness in the training phase, it
is important to apply rearing management before training by riding
in the field.
3.
By using TM and designing methods of rearing management, it is
possible to impose exercise load that better improves aerobic
exercise ability.
4.
We found that fat-free mass is valid as a new method for estimating
aerobic exercise ability.
Studies on correct feeding
for yearlings ; Supplementing nutrients with a view to enhancing
muscle volume and strength and preventing bone disease (2002-2006)
Purpose
Increasing
muscle volume is important in order to improve running ability,
while strong bones are necessary to prevent injuries during exercise.
In research until now, we have clarified the impact on body condition
score due to changes in blood amino acid concentration following
protein ingestion after exercise, as well as the impact of exercise
on mineral and bone metabolism, among others. In this research,
with a view to creating strong muscle and bones, we measured
1) the rate of synthesis and degradation of muscle protein, and
investigated the impact of exercise and post-exercise nutrient
ingestion on these. 2) Using a simple method of evaluating the
bone mineral content of horses, we investigated changes in standard
bone mineral content accompanying the growth of horses in the
training phase in Japan, while also studying the impact of various
types of exercise and nutrient conditions on bone mineral content.
Results
1.
Impact of branched chain amino acids (BCAA) on inhibition of
muscle protein degradation:
Using
twelve research yearlings, we administered branched chain amino
acids (BCAA) immediately after exercise. This is thought to be
effective in inhibiting muscle protein degradation. As a result,
the blood BCAA concentration rose significantly in the BCAA administered
group after exercise compared to that of the non-administered
group. However, the administration of BCAA after exercise produced
no marked effect on the inhibition of muscle protein degradation.
2.
Method of measuring the synthesis rate and degradation rate of
muscle protein, and the effect of accelerating the synthesis
rate of muscle protein:
We
established a method of measuring the rate of muscle protein
synthesis and degradation in hindlimb muscles (gluteal and crus
muscle groups), with stable isotope phenylalanine ( 2H5 Phe)
as a marker. Using this, we studied the impact of exercise on
muscle protein synthesis and degradation. As a result, when imposing
approximately 90% HRmax exercise load using a treadmill, the
rate of muscle protein synthesis after exercise was unchanged
compared to during rest. Therefore, we studied the impact of
various nutrient preparations after exercise on the rate of amino
acid absorption by hindlimb muscles. The result was that 10%
amino acids + glucose most significantly accelerated the rate
of muscle protein synthesis, while the difference between synthesis
and degradation increased. It also became clear that administrating
both solutions of amino acids and glucose promotes synthesis
of myogenic protein inside muscle tissue.
3.
Method of measuring bone mineral content (micro densitometry)
using X-rays and preparation of a BMC growth curve:
It
became clear that the method of measuring bone mineral content
using X-rays (micro densitometry) had a repeatability (CV%) of
1.0-1.6 and reproducibility of (CV%) 1.3-1.7, making it sufficiently
precise for practical application. We created a BMC growth curve
using this method. As a result, it became clear that bone mineral
content rises while bone metabolism markers fall with increasing
age.
4.
The effect of administering milk basic protein (MBP) and organic
minerals as nutrients to accelerate bone metabolism in horses:
On
feeding organic minerals with high bioavailability to weaned
yearlings, bone formation was accelerated and bone mineral content
increased compared to feeding with inorganic minerals. Meanwhile,
an increase in bone mineral content was seen when yearlings subjected
to exercise load were fed with milk basic protein (MBP). This
made it clear that organic minerals and MBP work to accelerate
bone formation, and we are now able to recommend them as nutrients
to accelerate bone metabolism in horses.
Research on an efficient method
of reproduction management for broodmares: Development of a method
of detecting ovarian activity in mares by measuring hormones
(2004-2006)
Purpose
In
racehorse breeding in recent years, there has been a tendency
to produce foals earlier in the year to take maximum advantage
of market prices. However, since horses are seasonally reproductive,
the reality is that maiden and barren broodmares only return
to estrus towards the end of April. Consequently, we are required
to develop a simple method of reliably inducing estrus at an
earlier stage. Moreover, in the early part of the breeding season,
silent heat and prolonged estrus caused by unovulatory follicles
commonly occur. As such, there is an urgent need to develop an
objective method of evaluating ovarian activity that can be applied
in breeding areas. The purpose of this research was to endocrinologically
develop diagnostic methods for the reproductive physiology of
horses, and particularly for ovarian activity, and to objectively
evaluate the ovarian activity of broodmares under various rearing
environments in breeding farms. At the same time, we studied
the effects of light control as a method of inducing estrus in
the early part of the breeding season.
Results
1.
Development of a method to measure hormones by time-resolved
fluorescent immunoassay:
Measurements
of the concentration of progesterone (P), estradiol and testosterone
in the blood of horses using the time-resolved fluorescent immunoassay
were good in both accuracy and sensitivity, and it became clear
that these can be measured in about 3 hours without using any
special facilities.
2.
Significance of the blood P concentration a weekly measurement
method:
A
weekly measurement of blood P concentration is extremely useful
as a method of evaluating ovarian activity in maiden (barren)
mares in the early part of the breeding season, when silent heat
and failure of ovulation are common. It is therefore seen as
a useful means of mating these horses in a planned fashion.
3.
Changes in blood P concentration in normally pregnant mares and
standard values for the gestation period:
We
traced changes in the blood P concentration of 20 normally pregnant
mares, and computed standard values for the gestation period.
On comparing these to abnormal cases, we proved that, in cases
of early embryonic loss or miscarriage, blood P concentration
shows low values throughout the gestation period, indicating
the importance of endocrinological diagnosis in the gestation
period.
4.
Usefulness of the Light Control method:
1)
As one method of stimulating ovarian activity, we studied the
usefulness of the Light Control method (LC method, creating an
illuminated environment of around 100 lux for 14.5 hours in the
daytime and 9.5 hours at night) from the winter solstice, using
94 maiden and barren broodmares from neighboring farms. As a
result, cases of confirmed first ovulation in the LC group were
51.9 % by the final week of the February and 80.5 % by the final
week of March. We also succeeded in advancing the timing of ovulation
by maiden and barren broodmares by about 1.5 months using the
LC method.
2)
Between one month before and one month after foaling, we studied
the usefulness of the LC method for broodmares due to give birth
in January and February. As a result, normal first ovulation
was confirmed in 45 out of 46 mares (97.8%). On the other hand,
in pregnant mares due to give birth in the same period without
any special measures as a control, clear ovarian inactivity and
failure of ovulation were observed in 3 out of 9 mares. This
proved that the method is also useful for broodmares due to give
birth in midwinter.
Conclusion
We
endocrinologically studied efficient management methods for broodmares,
and indicated guidelines for this. Namely, 1) we established
a quick and simple method of measuring blood progesterone (P)
in horses. 2) A weekly blood P concentration measurement was
useful for estimating the estrus cycles of broodmare and evaluating
the luteal functions of pregnant mares. 3) We established and
evaluated a Light Control method in Hokkaido, with the finding
that it is useful for barren mares and pregnant mares due to
give birth in January and February. From these results, it was
suggested that, by introducing objective diagnostic methods and
the Light Control method, we will be able to make further progress
in improving the reproductive efficiency of light horses.
Establishment of objective
standards for the recovery of uterine functions in the puerperal
period of light horses (2004-2006)
Purpose
Our
aim was to establish objective diagnostic standards whereby veterinarians
in sites of breeding could apply a shared understanding when
evaluating postpartum uterine functions and deciding the propriety
of mating. Besides this, we set out to ascertain rearing management
methods and blood properties in broodmares before and after parturition,
and to study the correlation between pregnancy rates and early
pregnancy loss.
Results
1.
Diagnostic standards for uterine function recovery:
We
periodically measured the resistance index (RI), pulsatility
index (PI) and time-averaged velocity (evaluation markers for
blood flow) of uterine arteries from before pregnancy to one
month postpartum, using Color Doppler Ultrasonography. As a result,
both RI and PI rose significantly at 3 days and 8 days postpartum,
compared to the values before parturition. Uterine arteries were
easily visualized in all mares during the late stage of pregnancy
using Color Doppler Ultrasonography. Mean PI and RI values were
0.77-0.84 and 0.52-0.53 during late gestation. They then showed
an abrupt increase to 1.73 and 0.74, respectively, after parturition.
In addition, the mean time-averaged velocity was over 70 cm/s
during the last three months of gestation, followed by an abrupt
decrease to approximately 20 cm/s at both 3 and 8 days after
parturition. A significant rise in PI and a decrease in time-averaged
velocity were shown 30 days after parturition, compared with
the 8th day postpartum.
From
these results, it was strongly suggested that the blood flow
in uterine arteries, which transport oxygen and nutrients to
the fetus, increases gradually during the gestation period, then
falls sharply with parturition. Judging from changes in blood
flow, meanwhile, the possibility was suggested that physiological
uterine recovery is still incomplete at the first estrus after
parturition.
2.
Breeders questionnaire survey on parturition as well as mating
and conception at first estrus after parturition:
We
carried out multivariate studies on the results of a questionnaire
survey aimed at breeders, concerning more than 1,300 cases of
parturition as well as mating and conception at first estrus
after parturition. As a result, we proved that there is a major
correlation between conception in postpartum estrus, on the one
hand, and the age of the mare and date of the previous parturition,
on the other.
3.
Impact of energy requirement and feed intake level on postpartum
broodmares:
In
farms where feed intake levels did not meet the energy requirement
of postpartum broodmares, problems such as a decrease in pregnancy
rates at first estrus after parturition were observed. Also,
from biochemical tests, the possibility was suggested that decreases
in lipids, protein concentrations and other properties of blood
could act as markers for the nutritional management of horses.
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