Effect of solid feed level and types of roughage on passage kinetics of milk replacer, concentrates, and roughage in veal calves
The aims of this study were (1) to determine the effect of solid feed (SF) level and type of roughage on passage kinetics of milk replacer (MR), concentrates, roughage in veal calves, and (2) to compare passage kinetics of concentrates measured by the fecal excretion curves of indigestible markers with the non-invasive 13C tracer breath test. In total, 48 Holstein-Friesian calves (6 weeks of age; 68 ± 7.7 kg of BW) were assigned to 1 of the 4 dietary treatments. Three treatments contained chopped straw as roughage in the SF mixture in a concentrate to roughage ratio of 90:10 (as fed). The SF level varied, being 20 g/kg BW0.75/d (LowSF), 30 g/kg BW0.75/d (MiddleSF), or 40 g/kg BW0.75/d (HighSF). The fourth treatment (Hay) contained long hay as roughage in the SF mixture in a concentrate to roughage ratio of 70:30 (as fed). The SF level of the Hay treatment was similar to the HighSF treatment, viz. 40 g/kg BW0.75/d. The quantity of MR was fixed for the HighSF treatment (i.e., 39 g/kg BW0.75/d) and during the adaptation period, the amount of MR for the other treatments was calculated based on a pair gain strategy, to achieve comparable body weight gain (BWG) across treatments. Passage kinetics were estimated using the recovery of 13C from a pulsed-dose [1-13C]octanoate with the concentrate or a pulsed-dose low-enriched bacterial protein in the concentrate, in breath measured in respiration chambers. The estimated time to peak enrichment was corrected for the time to peak enrichment following an intravenous injection of [13C]sodium bicarbonate. Passage kinetics were estimated from fecal excretion curves obtained after ingestion of the chromium-mordanted straw (i.e., for LowSF, MiddleSF, and HighSF treatments) or hay (i.e., for Hay treatment) as a marker for the roughage, 2 g of Ytterbium(II)Oxide as a marker for concentrate, and 9 g of cobalt(II)EDTA as a marker for the MR. The results of the fecal excretion curves show that the total-tract retention of MR was, on average, 12.4 h, and that the passage kinetic of MR was not affected by the level of SF. Additionally, the total-tract retention of concentrates was shorter (on average 21.4 h) than that of both straw (59.1 h) and hay (36.8 h), and was not affected by the level of SF. Furthermore, the passage of roughage, both through the rumen and through the total digestive tract, was affected by level of SF as well as type of roughage. Long hay increased time to peak by (on average) 22.3h (P = 0.004) relative to the chopped straw containing treatments. Hence, the passage rate of long hay is higher and subsequently the mean retention time in the gastro-intestinal tract shorter than that of chopped straw. Additionally, the fractional passage rate of the slowest compartment was related with SF level (r = -0.32, P = 0.049), suggesting that the fractional passage rate of the rumen decreases with increasing SF level likely due to the effect of SF level on rumen volume. The results of the 13C breath test show that [1-13C]octanoate cannot serve as an alternative to measure passage kinetics of concentrates through the digestive tract of veal calves. Overall, this study provides estimates of digesta passage kinetics of MR, concentrates and roughage that can be used in digestion modelling. It is concluded that the potential interactions between MR and SF occurring in the gastro-intestinal tract, do not complicate the prediction of the nutritional value of these ration components, and that the non-invasive 13C tracer breath test approach cannot serve as an alternative to the fecal excretion curves of indigestible markers to determine passage kinetics of concentrates in veal calves.
| Main Authors: | , , , |
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| Format: | External research report biblioteca |
| Language: | English |
| Published: |
Wageningen Livestock Research
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| Subjects: | Life Science, |
| Online Access: | https://research.wur.nl/en/publications/effect-of-solid-feed-level-and-types-of-roughage-on-passage-kinet-2 |
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| Summary: | The aims of this study were (1) to determine the effect of solid feed (SF) level and type of roughage on passage kinetics of milk replacer (MR), concentrates, roughage in veal calves, and (2) to compare passage kinetics of concentrates measured by the fecal excretion curves of indigestible markers with the non-invasive 13C tracer breath test. In total, 48 Holstein-Friesian calves (6 weeks of age; 68 ± 7.7 kg of BW) were assigned to 1 of the 4 dietary treatments. Three treatments contained chopped straw as roughage in the SF mixture in a concentrate to roughage ratio of 90:10 (as fed). The SF level varied, being 20 g/kg BW0.75/d (LowSF), 30 g/kg BW0.75/d (MiddleSF), or 40 g/kg BW0.75/d (HighSF). The fourth treatment (Hay) contained long hay as roughage in the SF mixture in a concentrate to roughage ratio of 70:30 (as fed). The SF level of the Hay treatment was similar to the HighSF treatment, viz. 40 g/kg BW0.75/d. The quantity of MR was fixed for the HighSF treatment (i.e., 39 g/kg BW0.75/d) and during the adaptation period, the amount of MR for the other treatments was calculated based on a pair gain strategy, to achieve comparable body weight gain (BWG) across treatments. Passage kinetics were estimated using the recovery of 13C from a pulsed-dose [1-13C]octanoate with the concentrate or a pulsed-dose low-enriched bacterial protein in the concentrate, in breath measured in respiration chambers. The estimated time to peak enrichment was corrected for the time to peak enrichment following an intravenous injection of [13C]sodium bicarbonate. Passage kinetics were estimated from fecal excretion curves obtained after ingestion of the chromium-mordanted straw (i.e., for LowSF, MiddleSF, and HighSF treatments) or hay (i.e., for Hay treatment) as a marker for the roughage, 2 g of Ytterbium(II)Oxide as a marker for concentrate, and 9 g of cobalt(II)EDTA as a marker for the MR. The results of the fecal excretion curves show that the total-tract retention of MR was, on average, 12.4 h, and that the passage kinetic of MR was not affected by the level of SF. Additionally, the total-tract retention of concentrates was shorter (on average 21.4 h) than that of both straw (59.1 h) and hay (36.8 h), and was not affected by the level of SF. Furthermore, the passage of roughage, both through the rumen and through the total digestive tract, was affected by level of SF as well as type of roughage. Long hay increased time to peak by (on average) 22.3h (P = 0.004) relative to the chopped straw containing treatments. Hence, the passage rate of long hay is higher and subsequently the mean retention time in the gastro-intestinal tract shorter than that of chopped straw. Additionally, the fractional passage rate of the slowest compartment was related with SF level (r = -0.32, P = 0.049), suggesting that the fractional passage rate of the rumen decreases with increasing SF level likely due to the effect of SF level on rumen volume. The results of the 13C breath test show that [1-13C]octanoate cannot serve as an alternative to measure passage kinetics of concentrates through the digestive tract of veal calves. Overall, this study provides estimates of digesta passage kinetics of MR, concentrates and roughage that can be used in digestion modelling. It is concluded that the potential interactions between MR and SF occurring in the gastro-intestinal tract, do not complicate the prediction of the nutritional value of these ration components, and that the non-invasive 13C tracer breath test approach cannot serve as an alternative to the fecal excretion curves of indigestible markers to determine passage kinetics of concentrates in veal calves. |
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