|Abstract or Summary
- This study involved three separate experiments employing a total
of 29 horses and 4 rabbits. The purpose of these studies was to investigate
the use of various quantities and forms of ryegrass straw in horse
rations, and to determine the use of whole corn plant pellets as an alternative
roughage for horses and rabbits.
In the first experiment, twenty head of mature (500 kg) mares and
geldings were divided into two groups of ten fed Diet I (51% ryegrass
straw and 49% concentrates), or Diet II (51% fescue hay and 49% concentrates).
The rations were completely pelleted, isonitrogenous, and isocaloric
containing 10.8% crude protein and 2.40 Mcal/kg digestible
energy (DE). Apparent digestibilities (Mean ± SE) were calculated by
utilizing an indicator ratio technique, chromic oxide. Results indicated
that dry matter (DM) digestibility was less (P < . 05) for Diet I than for
Diet II (DM 56.00 ± 1.8 and 66.0 ± 1.3). There were no differences
(P >. 05) between the two diets for acid detergent fiber (ADF 18.5 ± 1. 5 and 21.0 ± 1. 5), or cell wall constituents (CWC 30.8 ± 5 and 36.0 ±
1.7), Apparent crude protein (CP) digestibility in Diet I (76.2 ± .8)
was greater (P < .01) than Diet II (70,3 ± 1.0). During a 60-day maintenance
trial, body appearance improved considerably. However, considerable
wood chewing was noted with most horses during the initial
three weeks of the feeding period. Both groups maintained body weight
during the trial with average weight gains of 10kg and 1 kg, respectively,
for Diet I and Diet H. However, horses fed Diet I consumed 7.9 kg
of feed whereas horses on Diet II consumed 7.5 kg. The maintenance
and gain in weight, improved appearance and apparent excellent health
of the animals in this trial indicated that complete light horse diets can
be based upon poor quality roughages such as ryegrass straw. Although
the ration based on ryegrass straw was the cheaper per ton, the increased
intake made daily feed costs equal.
In the second experiment, four mature (500 kg) horses were used
in a 4 x 4 Latin square experiment to determine diet preference for a
variety of physical forms of ryegrass straw on the basis of nutrient digestibility,
consumption and side effects. All forms of straw were
similar in composition, varying only in form (longstem, pelleted, cubed
or briquetted). Addition of 5% molasses was used both as a binder and
to aid palatability.
All horses adapted to the compressed straws, but individual horses were hindered initially by the compactness and density of the cubed and
briquetted forms. Greater chewing and consumption time of these forms
was necessary for splitting and ingesting the straw. Mean voluntary
consumption of the densified forms of straw was greater (P <. 01) than
for longstem straw (5. 5, 6.4, 6. 0 and 5.9 kg for longstem, pelleted,
cubed and briquetted, respectively). Considerable wood chewing was
noted among all animals regardless of diet; however, horses consuming
the pelleted diet tended to chew even after ingesting the diet. No digestive
disturbances, health impairments or choking was noted.
Digestibility coefficients indicated that all horses digested equally
the CP and ash fractions regardless of diet form. Digestibility of ADF,
CWC and DM was lower for pelleted straw than longstem straw (P <. 01)
and, furthermore, was lower for the pellets than for the four other diet
forms. A possible explanation for this decreased digestibility of pellets
may be a faster rate of passage. Data indicate that the mature horse
will accept different physical forms of straw. Straw fed as the only
source of nutrients will not meet the horses' needs for maintenance over
time. Additional research is necessary to determine if concentrates
can be incorporated into one of the densified forms to form a complete
package feedstuff that might help solve the bulkiness, storage, and
transportation problems of conventional hay and grain rations.
In the third experiment, whole corn plant pellets (WCPP) contain ing 6. 2% CP, 30.8% ADF and 64. 8% CWC were fed to five mature
horses (500 kg) as a completely pelleted total ration (no supplementation).
Apparent digestibilities were calculated by utilizing conventional
total fecal collection techniques or the acid insoluble ash (ALA) method.
Results of the total collection vs. AIA techniques, respectively, were
not different (P >. 05) for CP, ADF and CWC, but were different for
EE. Similar trials with rabbits indicated higher CP digestibility, but
lower ADF and CWC digestibility as compared to horses. Results
from total collection and AIA techniques were not different in rabbits
(P >. 05).
A three month maintenance trial indicated that mature horses
could be maintained by feeding 6. 2 kg per day (1. 8% of body weight),
but considerable appetite depravity and excessive coprophagy were observed.
Supplementation of the WCPP with soybean meal to increase
dietary protein content to 10% CP eliminated all coprophagy within five
to seven days. Subsequent removal of the supplemental protein source
initiated coprophagy again within seven to ten days. Horses fed WCPP
alone, practising coprophagy, had higher (P < 05) CP digestibility than
when coprophagy was inhibited. Similarly, when WCPP are fed and
coprophagy is allowed but not practised during protein supplementation,
CP digestibility is significantly higher (P < .05) than when coprophagy
is allowed and practised with no protein supplementation. Furthermore, when protein is supplemented to the WCPP, there is a significantly
higher (P < . 01) CP digestibility than when WCPP are fed alone with
coprophagy inhibited and no protein supplemented. Irrespective of
whether or not coprophagy was practiced or protein supplemented, DM,
ADF and CWC digestibilities were not different (P > . 05). Data indicate
that the mature horse may be maintained on WCPP if supplemented
with an adequate protein source.
Utilizing the ALA technique for determining apparent digestibilities
in horses offers another indicator technique that may be more convenient
and easier to use than conventional total fecal collection techniques.