Wild and Free-Roaming Horses and Burros Current Knowledge and Recommended Research. (1980) / Chapter Skim
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Appendix A: Digestive Physiology of the Horse
Appendix A: Digestive Physiology of the Horse
Pages 259-301
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From page 259... ...
This fermentation site provides not only a protected environment of the proper pH for the microbes, but also the ability to slow down the passage of fibrous particles for more complete fermentation.
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From page 260... ...
; but in tropical grasses, where no such relationship exists, crude fiber is a poor index of forage quality (Olubajo et al 1974)
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From page 261... ...
By increasing the proportion of the plant which is slowly digestible or totally resistent to breakdown, the plant decreases its digestibility and palatability. Cellulose and hemicellulose, the principal structural carbohydrates of the cell wall, vary in the extent of their availability for fermentation dependent upon the lignin content of the cell wall (van Soest 1967)
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262 cr.
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From page 263... ...
263 3 G vD 2 cn i-t •H •-t c in~ ^, in c C C C !
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From page 264... ...
is most likely due to the differences in termperature at which they were grown and their greater stem-to-leaf ration. Furthermore tropical grasses show a greater difference between cell-wall and lignin values in the stem and leaves than temperate grasses, while the amount of soluble carbohydrates within the stem is greater in tropical grasses (Deinum and Dirven 1975)
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From page 265... ...
of the forage is directly digestible by gastric enzymes of vertebrates, if this fraction is fermented in the foregut, a sizeable fraction of the energy is lost to heat and methane production. Since little of the soluble nutrients escape fermentation (Bryant 1963, Bryant and Robinson 1963, Nolau et al.
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From page 266... ...
266 co 5U w Q °K 0 0 0 CO < £h-3 '>,, < Z -- ^ w § /-v ^ 2 Z H .P • O 2E r^ o o w •y ~.
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From page 267... ...
Therefore dietary selection for amino acids is not essential, but selection for nitrogen in any digestible form is critical. Also because rumen microorganisms rapidly assimilate most of the glucose in the rumen, foregut fermenters must rely heavily on deamination of protein in the liver for their blood-sugar supply.
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From page 268... ...
Quantitative differences between ruminants and nonruminants would be expected on the basis of the positioning of the fermentation site. The magnitude of the difference should be size specific, decreasing with larger body size as retention times increase.
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From page 269... ...
Within the nonruminant the relative volume of the hindgut increases, indicating the growing importance of fermentation with larger body size. However donkeys have, on an absolute scale, substantially larger lower tracts than expected and show greater capacities for fiber digestion than the horse (Wolter and Velandia 1970)
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From page 270... ...
270 e sis s = s 7.
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From page 271... ...
271 tn •p .
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From page 272... ...
He found that fecal particle size was larger in nonruminants than ruminants. Although this phenomenon is often attributed to the longer retention times of ruminants (see below)
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From page 274... ...
Because Mfi increases with weight, albeit at a decreasing rate, large animals always require more total energy but small animals require more energy relative to their body weight. The capacity of the gut determines, in part, the capacity for digestion in the herbivore.
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From page 275... ...
275 ^r O CO CO O cc CM o h.
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From page 276... ...
. Since total metabolic requirement increases with body size, larger animals require more total food than smaller animals.
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The exponent is very close to l.00, indicating an isometric increase in gut size with body weights. There is no significant difference between ruminants and nonruminants in this relationship.
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From page 278... ...
, evaluating several assays, found Van Soest's methods (1964) of detergent analysis to be the best predictor of digestibility in forages for horses (the inadequacy of crude fiber as a forage measure was discussed under "plant material" above)
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From page 279... ...
. While the importance of caecal retention times are citical to the determination of fiber digestion in the horse, the effect of fistulas and cannulas, necessary for these determinations, must be carefully measured in each experiment.
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From page 280... ...
280 oiNvoao do 0> T3 J3- CU Pi """^ CD +J 'O 2 rH .P CU O O C t*
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From page 283... ...
microbial respiration and methane production) must be subtracted- Therefore, when considering the soluble fraction, the difference between DE and ME (metabolizable energy)
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From page 284... ...
Evidence exists of differences in passage rates, forage quality reaching the fermentation site and efficiency of digestion within the site (albeit often contradictory)
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From page 285... ...
. The point where intake compensation ceases appears to be sensitive, independently, to the energy requirements of the animal and its body size (Peterson and Baumgardt 1971b, Owen and Ridgmen 1968)
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From page 286... ...
Energy Requirements and Intake Calculations In only one study among the recent work on the energy requirements of horses have measures been made independent of energy intake. The one exception is Wooden et al.
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From page 287... ...
Intake for horses is consistently lower than for cattle on diets of low crude fiber. As this fiber fraction increases, horses approach cattle intake levels and then exceed them above -40% crude fiber.
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From page 288... ...
288 T3 C it)
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From page 290... ...
The equations presented here are incorporated with others relating TDN, DE and ME to predict intake of the two species (see Energy requirements and intake calculations) , References Cited Alexander, F
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From page 291... ...
1942. Microbial synthesis and autolysis in the digestive tract of herbivores.
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From page 292... ...
1957. Interrelations between digestible nutrient and energy content, voluntary dry matter intake and overall feeding value of forages.
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From page 293... ...
1969. Partitioning the nutrients of forage for horses hay holo cellulose hemi cellulose cellulose lignin carbohydrate protein ash ether extract crude fiber.
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From page 294... ...
197l. Apparent digestion in various segments of the digestive tract of ponies fed diets with varying roughage grain ratios.
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From page 295... ...
1978. Comparative cell wall and dry matter digestion in the cecum of the pony and the rumen of the cow using "in vitro and nylon bag techniques.
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1970. The digestibility of temperature and tropical grasses.
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1968. Further studies of the effect of dietary energy content on the voluntary intake of pigs.
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196l. Rate of passage of fecals through the digestive tract of Holstein cows.
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From page 299... ...
33:38-4l. Van Soest, P
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From page 300... ...
II. Rumen content, dry matter passage and water intake..
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From page 301... ...
1976. Effect of the physical form of a complete mixed feed on its rate of passage through the digestive tract and digestibility in ponies.
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