Comparitive Digestibility Of Cattle versus Sheep: Effect of Forage Quality
Abstract
Chapter III Comparative Digestibility of Different Types of Forage by Cattle and Sheep Abstract Five yearling English crossbred steers and 5 yearling whiteface wethers each fitted with a ruminal cannula were randomly assigned to one of the three forage sources in an incompletely replicated 6 x 6 Latin square design experiment. The treatment structure was arranged in a 2 x 3 factorial with ruminant species (2) and forage source (3) as the factors. Forage sources were: 1) alfalfa hay; 2) warm-season grass hay mix; and 3) Lovegrass hay. Steers and wethers consumed similar amounts of forage and its components, and intake (P<0.05) was more influenced by forage quality than ruminant specie. When expressed per unit of metabolic BW (P<0.05), cattle consumed more DM, fiber and CP than sheep. Steers and wethers digested similar amounts of nutrients for two of the forages. Total tract digestibility was influence by specie x diet interactions (P<0.05). Sheep and Cattle were similar in the digestion of nutrients from alfalfa and grass hay. Cattle digested lovegrass significantly better than sheep. Site and extent of digestion by steers and wethers was similar (P<0.05). Digestion was influenced more by forage than by specie. The higher quality alfalfa was digested faster than the other two forages. Ruminal DM fill was influenced by forage more than specie. Steers and wethers showed more DM fill from grass hay and lovegrass hay than alfalfa at all stages. Ruminal liquid fill influenced more by forages showed grass hay to have more fill than the other two forages. VFA's were influenced by forage more than species. Rumen VFA counts showed alfalfa to be the highest, grass hay intermediate, and lovegrass was the lowest. The acetate:propionate ratio was highest for lovegrass, intermediate grasshay, and lowest for alfalfa. In our experiment our results suggest that while cattle and sheep do have similar results on some areas, one must make the decision on weather or not the sacrifice of addition information is worth the cost reduction of sheep. Introduction Research in ruminant nutrition all most always utilizes sheep or cattle. With the increased budgeted concerns for research institutions cattle become an expensive option for research. The idea to use sheep instead of cattle has become a popular option. Research done to utilize sheep as small animal models for cattle usually comes back with mixed results. Nutrient digestibility differences between cattle and sheep are generally small and of little importance; however; highly digestible feeds, such as cereal grains, tend to be more efficiently digested by sheep. Poorly digested feedstuffs, such as low quality roughages, tend to be better digested by cattle (McDonald, 2002). Many believe that this occurs because cattle have a greater proportional ruminal fill and lower particle passage rate. It is thought that sheep masticate feed more extensively than cattle, and that reduction in particle size may allow sheep to have a more rapid passage rate. Replacing cattle with sheep will decrease cost, decrease the amount of space needed to do research, and allow the number of research animals to increase greatly. Therefore our objective was to evaluate comparative digestibility of different types of forage by cattle and sheep
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