Rumen Escape and Apparent Degradation of Amino Acids After Individual Intraruminal Administration to Cows

Abstract

Apparent rumen degradation and escape of 18 amino acids (AA) after individual administration intraruminally were studied using two nonpregnant, nonlactating, rumen-cannulated cows fed a ration containing hay and concentrate twice daily. The pulse-dosages of AA were 75, 150, 300, and 600 mmol. Polyethylene glycol was used as the liquid marker. Rates of apparent degradation during the first 60 min (initial degradation) varied markedly among the AA; rates were highest for Ser, Asn, Glu, and Gln and lowest for Tyr, Val, Arg, and His. At the 75-mmol dosage, which corresponded to an initial substrate concentration of about 1 mM of rumen fluid, initial degradation varied between 95 and 40% of the dosage, depending on the AA. Rates, expressed as percentages of the dosage, decreased as dosages increased. During the first 8 h after administration, escape of the AA increased from a mean of 9% at the lowest dosage to a mean of 21% at the highest dosage. At the highest dosage, Met caused a net increase in the concentration of 11 of the other AA in rumen fluid. Twelve of the AA administered caused a net increase in the concentration of Ala in rumen fluid. Methionine and Lys are among the AA considered to be limiting to milk yield. These AA showed relatively high rumen escape values and may be useful as feed supplements even in an unprotected form.

Effect of diets with hydrolysed feather keratin meal on milk yield and composition in dairy cow and calf performance

“…Thomas and Martin (1988) and Rulquin (1992) also demonstrated that a postruminal casein infusion increased milk production and the protein content of milk (from 1.1 to 1.5 g/kg) due to increased protein available for absorption and amino acid delivery. Similar results were obtained by Patton (1996) and Velle et al (1997) who supplemented diets with protected methionine which improved amino acid composition in duodenal digesta.…”

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

“…Feeding crystalline AA could be economically attractive when their ruminal escape rates exceed 20 to 25% [11]. Such rates, observed with dairy cows with high AA administration [22][23][24], have not previously been reported for fast-growing bulls. However, the main factor influencing the proportional ruminal escape of free AA is their concentration in the ruminal fluid, which depends on its volume and the dose of AA.…”

“…However, the main factor influencing the proportional ruminal escape of free AA is their concentration in the ruminal fluid, which depends on its volume and the dose of AA. High ruminal fluid AA concentrations could inhibit the activity of microbial deaminases in the rumen and, therefore, AA degradation [22]. Since it is during the growth phase that AA requirements in BBb are the most important [6,7], when rumen volume is the lowest, the ruminal AA concentration is more influenced by AA administration and causes the highest proportional AA escape from the rumen.…”

“…Nevertheless, the results suggest that no effect of free AA supplementation remained on the composition of intestinal content 12 h after AA administration. Velle et al [22] showed that most free AA, except histidine, were gone from the rumen 8 h after ruminal administration, whatever the amounts supplied.…”

“…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.…”