horses were fed either an all forage diet (4.54 kg alfalfa cubes + 5.45 kg alfalfa/grass hay)(FORAGE) or a mixture of forage and grain (3.63 kg sweet feed + 2.72 ...
THE EFFECT OF EXERCISE ON THE DIGESTIBILITY OF AN ALL FORAGE OR MIXED DIET IN THOROUGHBRED HORSES J.D. Pagan1, P. Harris2, T.Brewster-Barnes1, S.E. Duren1 and S.G. Jackson1 1
Kentucky Equine Research, Inc., Versailles, KY 40383 Waltham Centre for Pet Nutrition, Waltham-on-the-Wolds, Leic., UK
2
Introduction Most digestibility studies in horses have been conducted with idle horses confined to metabolism stalls. The values obtained from these studies are used for all classes of horses including the performance horse. It has not been clearly established whether exercise affects digestibility. Therefore, this study was conducted to measure the effect of 5 miles of daily trotting and galloping exercise on the digestibility of either an all forage or a mixed forage/grain ration. In addition, voluntary salt intake and urinary mineral excretion were measured. Materials and Methods Four conditioned Thoroughbred geldings were used in a 2X2 factorial design to investigate the effect of exercise and diet on apparent nutrient digestibility. The experiment consisted of 4 periods that were 4 weeks in length. During each period, the horses were fed either an all forage diet (4.54 kg alfalfa cubes + 5.45 kg alfalfa/grass hay)(FORAGE) or a mixture of forage and grain (3.63 kg sweet feed + 2.72 kg alfalfa/grass hay + 2.27 kg alfalfa cubes)(MIXED)(table 1). During each period, one horse from each diet was exercised daily on a high speed treadmill (EX) (table 2). The non-exercised horses (NON-EX) were turned out daily in paddocks with muzzles to prevent grazing. During the fourth week of each period, a complete collection digestion trial was conducted. Each morning during the collection period, the EX horses performed an exercise bout on the treadmill (inclined to 3 0) which consisted of a 5 min warm-up walk, 1600 m at 4 m/s, 1600 m at 7 m/s, 1600 m at 9 m/s, 1600 m at 7 m/s, 1600 m at 4 m/s and a 5 min warm-down walk. Each afternoon, the EX horses were hand walked 1600 m. The NON-EX horses were hand walked 1600 m twice daily. During the 5 day collection period, the horses were housed in metabolism stalls that allowed the complete and separate collection of urine and feces. During the collection period, daily feed intake (table 3) and total fecal and urine output were measured. Salt was offered free choice to the horses in 1 kg salt blocks during both the 3 week adjustment period and during the collection period. Both feed and feces were analyzed for dry matter, crude protein, ADF, NDF, fat, calcium, phosphorus, magnesium, sodium, potassium, zinc, copper, manganese, and ash. Calcium, phosphorus, magnesium, potassium, sodium, zinc, copper and manganese were
measured in the urine. Apparent digestibilities and daily urinary mineral excretion were calculated for each nutrient measured. Table 1. Nutrient Composition of Experimental Feed
Nutrient
Grain 1
Hay
Hay Cubes
dry matter (%)
84.4
92.47
89.63
crude protein (%)2
11.48
12.13
19.63
acid detergent fiber (%)2
7.38
45.47
34.47
neutral detergent fiber (%)2
16.83
60.77
42.8
lignin (%)2
1.98
8.40
8.8
ether extract (%)2
5.13
2.47
2.87
NSC (%)2,3
62.9
18.11
23.43
calcium (%)2
0.17
1.02
1.76
phosphorus (%)2
0.35
0.36
0.26
magnesium (%)2
0.16
0.23
0.32
sodium (%)2
0.04
0.19
0.08
potassium (%)2
0.93
1.39
1.90
copper (ppm) 2
6.00
6.33
8.33
29.75
15.67
21.67
zinc (%)2 42% corn, 47% oats, 11% molasses 2 dry matter basis 3 NSC = 100-CP-EE-NDF-Ash 1
Table 2. Exercise program for each period week 1
week 2
week 3
week 4
2 horses on exercise treatment exercised 6 days per week
2 horses on exercise treatment exercised 6 days per week
2 horses on exercise treatment exercised 6 days per week
5 min walk
5 min walk
5 min walk
5 min walk
800 m @ 4 m/s
800 m @ 4 m/s
1600 m @ 4 m/s
1600 m @ 4 m/s
1600 m @ 7 m/s
800 m @ 7 m/s
1600 m @ 7 m/s
1600 m @ 7 m/s
800 m @ 4 m/s
1600 m @ 9 m/s
1600 m @ 9 m/s
1600 m @ 9 m/s
5 min walk
800 m @ 4 m/s
1600 m @ 4 m/s
1600 m @ 7 m/s
5 min walk
5 min walk
1600 m @ 4 m/s
all horses exercised 3 times per week
5 min walk
Table 3. Feeding schedule during collection week.
Time
Diet 1 - FORAGE
Diet 2 - MIXED
6 am
1.14 kg hay cubes 2.73 kg hay
1.82 kg grain 1.36 kg hay
12 pm
1.14 kg hay cubes
1.14 kg hay cubes
4 pm
1.14 kg hay cubes 2.73 kg hay
1.82 kg grain 1.36 kg hay
10 pm
1.14 kg hay cubes
1.14 kg hay cubes
Table 4. Apparent Nutrient Digestibilities (%)
Diet
Exercise
Diet,E xer.
Forage
Mixed
Prob>F
Exercise
Non-exercised
Prob>F
Prob> F
DM
54.6
62.1
.01
57.8
58.9
.05
NS
CP
69.7
70.5
NS
70.2
70.1
NS
NS
ADF
39.1
34.6
.02
35.7
38.0
.15
NS
NDF
40.9
34.6
.01
37.2
38.2
NS
NS
Hemi
46.4
34.0
.05
41.3
39.1
NS
NS
Fat
29.9
52.6
.01
40.6
42.0
NS
NS
Ca
59.3
48.3
.01
53.4
54.2
NS
NS
P
3.0
0
NS
0
3.0
NS
NS
Mg
33.8
29.7
NS
28.5
35.0
NS
NS
K
68.3
72.4
.15
66.3
74.3
.02
NS
Na
62.3
70.2
NS
83.6
48.9
.01
NS
Zn
-29.3
-42.6
NS
-35.0
-36.9
NS
NS
Cu
32.2
22.5
.13
32.1
22.5
.15
NS
Mn
4.5
-4.0
.03
-0.7
1.2
NS
NS
Ash
45.5
41.1
.001
41.8
44.8
.01
NS
Results and Discussion The apparent digestibilities of the diets with and without exercise are shown in table 4. The dry matter digestibility of the MIXED diet was significantly higher than the FORAGE diet (54.6% vs 62.1%) (p
