Ruminant Rumen Physiology and Acidosis (cattle／sheep／goats; alpacas are pseudoruminants)

FAQ

How many compartments does a ruminant stomach have? Is it the same in alpacas?

No, and the two must not be conflated. Cattle, sheep and goats are true ruminants, with a stomach divided into 4 compartments — the rumen (the largest, a microbial fermentation vat), the reticulum (a honeycomb structure in which swallowed metal foreign bodies readily lodge, giving rise to "hardware disease／traumatic reticuloperitonitis"), the omasum (a many-layered structure, mainly absorbing water), and the abomasum (the true glandular stomach). Alpacas and other camelids have only 3 compartments (C1/C2/C3) and are pseudoruminants; the mechanism is similar but the structure is not the same.

反芻動物の胃はいくつの腔室がありますか。アルパカも同じですか。 — 同じではなく、両者を混同することは禁じられています。ウシ、ヒツジ、ヤギは真の反芻動物で、胃は 4 つの腔室に分かれます——ルーメン rumen（最大で、微生物の発酵槽）、第二胃 reticulum（蜂の巣状の構造で、誤飲した金属異物がここに引っかかりやすく、「ハードウェア病 hardware disease／創傷性第二胃腹膜炎」と呼ばれます）、第三胃 omasum（多層構造で、主に水分を吸収します）、第四胃 abomasum（本当の腺胃）。アルパカとラクダ科の動物は胃室が 3 つ（C1/C2/C3）しかなく、擬反芻動物 pseudoruminant に属し、機序は似ていても同一の構造ではありません。

How many compartments does a ruminant stomach have? Is it the same in alpacas? — No, and the two must not be conflated. Cattle, sheep and goats are true ruminants, with a stomach divided into 4 compartments — the rumen (the largest, a microbial fermentation vat), the reticulum (a honeycomb structure in which swallowed metal foreign bodies readily lodge, giving rise to "hardware disease／traumatic reticuloperitonitis"), the omasum (a many-layered structure, mainly absorbing water), and the abomasum (the true glandular stomach). Alpacas and other camelids have only 3 compartments (C1/C2/C3) and are pseudoruminants; the mechanism is similar but the structure is not the same.

Why does suddenly feeding a large amount of grain harm cattle and sheep?

The symbiotic microbial population in the rumen needs time to adapt to a change of feed. If a large amount of high-starch or high-sugar concentrate is given suddenly (excess grain, an abrupt change of feed formulation, escaping the fence and raiding the grain store), the microbes ferment rapidly and produce large quantities of volatile fatty acids and lactic acid at a rate exceeding the buffering and absorptive capacity of the rumen wall; pH falls rapidly, the rumen wall is damaged and endotoxin is released, which can go on to cause systemic toxaemia, laminitis (see 3.3), liver abscesses and even death.

なぜ急に大量の穀物を与えるとウシやヒツジに問題が起きるのですか。 — ルーメン内の共生菌群は飼料の変化に順応するのに時間を必要とします。もし急に大量の高デンプンまたは高糖の濃厚飼料を与えれば（穀物の過給、飼料配合の急な変更、柵から逃げ出して穀物庫を食い荒らす）、微生物が急速に発酵して大量の揮発性脂肪酸と乳酸を産生し、その速度がルーメン壁の緩衝と吸収の能力を超えて pH が急激に低下し、ルーメン壁を破壊して内毒素を放出し、さらに全身性の中毒、蹄葉炎（3.3 参照）、肝膿瘍、さらには死を引き起こすことがあります。

Why does suddenly feeding a large amount of grain harm cattle and sheep? — The symbiotic microbial population in the rumen needs time to adapt to a change of feed. If a large amount of high-starch or high-sugar concentrate is given suddenly (excess grain, an abrupt change of feed formulation, escaping the fence and raiding the grain store), the microbes ferment rapidly and produce large quantities of volatile fatty acids and lactic acid at a rate exceeding the buffering and absorptive capacity of the rumen wall; pH falls rapidly, the rumen wall is damaged and endotoxin is released, which can go on to cause systemic toxaemia, laminitis (see 3.3), liver abscesses and even death.

What can a keeper do to prevent ruminal acidosis?

The original text sets out four principles that can be acted on: any change of feed must always be "gradual" rather than "all at once"; grain and concentrate must be limited in amount and given in divided portions; pasture and hay must always remain the basis of the staple diet; and animals must be prevented from accidentally getting into the grain store or feed room.

飼い主はルーメンアシドーシスを予防するために何ができますか。 — 原文は 4 つの実行できる原則を挙げています：飼料の切り替えは一律に「一度に全部」ではなく「段階的」に行うこと。穀物と濃厚飼料は量を制限して数回に分けて与えること。牧草と乾草を常に主食の基礎とすること。動物が誤って穀物庫や飼料庫に入り込まないようにすること。

What can a keeper do to prevent ruminal acidosis? — The original text sets out four principles that can be acted on: any change of feed must always be "gradual" rather than "all at once"; grain and concentrate must be limited in amount and given in divided portions; pasture and hay must always remain the basis of the staple diet; and animals must be prevented from accidentally getting into the grain store or feed room.