Nutritional and Animal Welfare Implications to Lameness

摘要

Rumen acidosis is associated with fermentive disorders occurring secondary to the consumption of feedstuffs that contain relatively large amounts of highly fermentable carbohydrates. It may be complicated by diets that offer less than adequate levelsof effective fiber. Lactic acid accumulates within the rumen, leading to rumenitis and a change in the rumen flora that favors lactate production. The change in rumen flora is also associated with the release of endotoxins within the rumen. These endotoxins, along with various other vaso-active substances (including lactate), are absorbed into the blood stream where they disrupt the normal flow of blood within the tissues of the corium. Inflammation of the corium initiates the release of potent metalloproteinase enzymes that cause destruction of the suspensory apparatus of the 3rd phalanx. Sinking and rotation of the 3rd phalanx follows with compression and damage to the supporting tissues and structures of the corium that precipitates the developmentof sole ulcers and yhite line disease. In recent years, research from the United Kingdom suggests that damage to the suspensory apparatus is likely to occur by other mechanisms. Their work demonstrates that as animals' progress toward calving, rigidity and strength of the collagenous connective tissue of the suspensory apparatus is significantly reduced (Tarleton et al., 2002; Tarleton and Webster, 2002). They propose that these changes are potentially a consequence of both the activation ofmetalloproteinase enzymes and peripartum hormones, such as estrogen and relaxin. The implications of this are that in addition to feeding and nutrition, dairy farmers must pay particular attention to cow comfort during the transition period. The digitalcushion consisting of fat and loose connective tissue is an important support structure in the claw. Recent work suggests that body condition score mirrors size (i.e. fat content) of the digital cushion and may be very important to the integrity and health of claws. Whereas, most have thought that lame cows become thin, their research suggests mat thin cows become lame. Maintenance of good body condition throughout the first 120 days of lactation may prove to be a very important feeding objective. The welfare implications of lameness are huge. Lameness affects performance, causes pain, and disrupts the cow's ability to express normal behavior. The underlying causes of lameness are multi-factorial, but based upon the preponderance of information on thepathogenesis of lameness in recent years, there is little question that housing is a major contributor to the development of lameness disorders. Overcrowding, stall design and stall surfaces, flooring, and specific management practices restrict resting and force cows to stand for longer periods. Smooth and manure slurry covered or wet floors are slippery and may precipitate injuries due to falling. Abrasive flooring conditions cause excessive wear and lameness due to thin soles. Anything that increasesthe incidence of lameness contributes to poor animal welfare. Treatment of lameness needs to be timely and carefully administered.