Ruminal Degradation and Outflow of Amino Acids in Cows

Abstract

Summary Two rumen‐ and duodenum‐cannulated cows were used to study the disappearance rate, degradation in, and outflow from the rumen of four amino acids administered individually into the rumen at the following dose levels (mmol): lysine 273–547‐820, tyrosine 276–496‐828, isoleucine 381–762‐1143, methionine 335. Calculations were based on the use of PEG (polyethylene glycol, 4000) as liquid marker for determination of the volume and dilution rate of rumen fluid. At the same dry matter intake a comparison was made between the influence of a high‐forage and a low‐forage diet. At the lowest dose level, the initial rates of disappearance (mmol/l per h) were 0.52 for lysine, 0.48 for tyrosine, 0.55 for isoleucine and 0.58 for methionine. The rates increased with increasing dose levels. The fractions of administered amino acids flowing out of the rumen and the fractions degraded in the rumen were studied over an 11 h period. At the lowest dose level, outflow (mmol/11 h) amounted to 42 and 54 for lysine, 36 and 29 for tyrosine, 93 and 48 for isoleucine, 104 and 75 for methionine on the high and low forage diet, respectively. The corresponding figures for degradation were 232 and 209, 239 and 247, 287 and 333, 226 and 259 mmol/11 h. The fractions of an administered amino acid flowing intact out of the rumen increased, and the fractions degraded in the rumen decreased, with increasing doses. Zusammenfassung Ruminaler Abbau und Ausstrom von Aminosäuren bei Kühen Zur Untersuchung der Verschwindensrate und des Abbaus von Aminosäuren sowie des Ausstroms von Aminosäuren aus dem Pansen wurden bei jeweils zwei Kühen mit Pansen‐ und Duodenalkanüle 4 Aminosäuren einzeln in folgenden Dosierungen (mmol) in den Pansen eingebracht: Lysin: 273–547‐820, Tyrosin: 276–496‐828, Isoleucin: 381–762‐1143, Methionin: 335. Für die Bestimmung des Volumens und der Verdünnungsrate der Pansenflüssigkeit wurde PEG (Polyethylenglykol, 4000) als Flüssigkeits‐Marker verwendet. Bei gleicher Trockenfutteraufnahme wurde der Einfluß einer rauhfutterreichen und einer rauhfutterarmen Ration auf die Ergebnisse miterfaßt. Bei der niedrigsten Dosierung betrugen die initialen Verschwindensraten (mmol/l per h) für Lysin 0,52, für Tyrosin 0,48, für Isoleucin 0,55 und für Methionin 0,58. Die betreffenden Werte nahmen mit der Dosierung zu. Die Fraktionen der verabreichten Aminosäuren, die den Pansen verließen bzw. im Pansen abgebaut wurden, wurden während eines 11 stündigen Zeitraums ermittelt. Bei der niedrigsten Dosierung betrugen die Werte für den ruminalen Ausstrom von Aminosäuren (mmol/11 h) bei rauhfutterreicher bzw. bei rauhfutterarmer Fütterung für Lysin 42 bzw. 54, für Tyrosin 36 bzw. 29, für Isoleucin 93 bzw. 48 und für Methionin 104 bzw. 75. Die entsprechenden Werte für den Abbau betrugen 232 und 209, 239 und 247, 287 und 333 sowie 226 und 259 mmol/11 h. Mit zunehmender Dosierung stieg der Anteil der verabreichten Aminosäuren, die den Pansen verließen, an, während der abgebaute Anteil abnahm.

Supply of the dairy cow with amino acids from dietary protein

“…In agreement with this Kowalczyk (1994) concluded, after comparing in vitro and in vivo ruminal deg radation of free amino acids, that amino acids disappeared faster in vivo than in vitro, and that only small proportions of free amino acids appeared at the duode num. Other experiments has though indicated that a dose dependent ruminal es cape of free amino acids takes place (Cottle and Velle, 1989;Sulu et al, 1989;Velle et al, 1997), and is enhanced by the dosage of free amino acids in mixtures and that the apparent degradation rate of free amino acids is not dependent on feed level (Volden et al, 1998). There is thus substantial reason to believe that amino acid composition of undegraded feed protein flowing to the duodenum, is different compared to the original feed.…”

Rumen escape of methionine and lysine administered intraruminally to growing double-muscled Belgian Blue bulls

“…Total ruminal outflow of free Lys did not differ when it was supplied with or without Met (P = 0.08) and reached, respectively, 26.6 ± 5.5 and 27.5 ± 5.5 g. In this study, high ruminal escape of Met and Lys were observed despite dietary conditions favourable to AA degradation. High concentrate diets actually induce an efficient growth of microorganisms [16] and a selection of amylolytic bacteria that utilise high proportions of AA [24]. However, more than 65% of the total amounts of free Met and free Lys that escaped ruminal fermentation did so during the first 4 h. According to Velle et al [23], ruminal escape of free AA is increased when they are administered with larger amounts of other AA.…”

“…The ruminal escape of free AA has been shown to vary with AA [22], dietary conditions [16], amount supplied [24], and whether the AA is administered individually or with other AA [23]. To our knowledge, only Campbell et al [2] has investigated free AA supplementation for growing cattle, and observed no effect on animal performances although the amounts supplied were modest.…”

Harnessing the Value of Rumen Protected Amino Acids to Enhance Animal Performance – A Review

“…Supplementing AA in low-quality forage-based diets promotes protein accretion and N retention (Volden et al 2001). Sulu et al (1989) fed cattle two different diets supplemented with AA and observed that the degradation rates of these AAs in the forage-based diet were less and escaped more from the rumen as compared with the high concentrate diets.…”