The use of dosed and herbage n-alkanes as markers for the determination of herbage intake

Whether the rumen microbes are able to synthesize and/or degrade long-chain alkanes in anaerobic conditions remains a question to be answered before these hydrocarbons can be confidently used as duodenal flow or rumen transit markers. In this context, an experiment in vitro was carried out to establish whether within a rumen liquor fermentation system, n-alkanes can be derived from de-waxed structures of the plant or from non-alkane wax components (long-chain fatty alcohols, long-chain fatty acids and esters), or may be metabolized by bacteria to other components or to shorter-chain hydrocarbons. Ryegrass was labelled with 14 C in growth chambers under controlled conditions in order to use it as a substrate. The labelled material obtained was separated in three fractions: labelled alkanes, labelled de-waxed plant and labelled wax components without the alkanes. These fractions were used for three different incubations in vitro, which objectives were as follows: 1. To check whether rumen bacteria can synthesize alkanes from carbon structures other than waxes (e.g. sugars). 2. To verify whether rumen bacteria can metabolize the n-alkanes to other compounds. 3. To check whether rumen bacteria can synthesize n-alkanes from other carbon compounds from waxes. The results showed that there was neither bacterial synthesis nor metabolism of the n-alkanes in in vitro conditions.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In vitro studies of the metabolism of [14C]-n-alkanes using ruminal fluid of sheep as substrate

Keli

Mayes²,

Vega

2008

“…The DM intake (DMI) of each individual cow was estimated in year 2 between days 67 and 73 using the n-alkane technique (Mayes et al, 1986), as modified by Dillon and Stakelum (1989). Cows were dosed twice daily at approximately 0900 and 1600 h for 12 consecutive days (starting on day 62) with a paper bung (Carl Roth, GmbH, Karlesruhe, Germany) containing 500 mg of dotriacontane (C 32 ).…”

Section: Feeding Managementmentioning

confidence: 99%

The effect of dry cow winter management system on feed intake, performance and estimated energy demand

O’Driscoll

Hanlon

Buckley

et al. 2010

This research compared three wood-chip out-wintering pad (OWP; an unsheltered OWP; a sheltered OWP (both with a concrete feed apron); and an unsheltered OWP with silage provided directly on top of the wood-chip bedding (self-feed OWP)) designs and cubicle housing with regard to dairy cow performance during the pre-partum period, and for 8 weeks post partum. Data were compared during 2 years. In Year 1, the unsheltered (space allowance 5 12 m 2 per cow) and sheltered (6 m 2 per cow) OWPs were compared with cubicle housing (n 5 49 cows per treatment). In Year 2, all three OWP designs (12 m 2 per cow) were compared with cubicle housing (n 5 24 cows per treatment, split into two replicates). Animals were dried off and assigned to treatment in the autumn, and remained there until calving in spring. Subsequently, they were managed at pasture during lactation. Outcome measures for analysis during the pre-partum period were feed intake, live weight, body condition score (BCS), heat production and heat loss, and post-partum were live weight, BCS, milk yield and milk composition. In Year 1, all cows had a similar live weight, but both pre-partum and at calving cows on the unsheltered OWP had a lower BCS than cows in cubicles ( P , 0.05). However, in Year 2, there were no differences in either live weight or BCS. In Year 1, cows in the unsheltered OWP produced less heat than in cubicles ( P , 0.05), but in Year 2, there was no treatment effect. In both years, cows in unsheltered OWPs lost more heat than cows in the sheltered OWP ( P , 0.001). Treatment had no effect on milk composition either year. However, in Year 2, cows in the self-feed OWP had higher milk yields than the other treatments ( P , 0.05). The lower BCS and heat production values in unsheltered treatments during Year 1 were probably because of higher rainfall and wind-speed values of that year. However, in both years, live weight in all treatments increased pre partum, and BCS did not decrease, indicating that unsheltered cows did not need to mobilise body reserves. Thus, OWPs could be a suitable pre-partum alternative to cubicle housing for dry dairy cows with regard to some aspects of dairy cow productive performance. However, further research should be carried out to investigate longer-term effects.

“…The individual herbage intake was determined by the method of n-alkanes (Mayes et al, 1986) using tritriacontane (C 33 ) as the internal marker and dotriacontane (C 32 ) as the external marker, according to the following equation:…”

Section: Paddock Managementmentioning

confidence: 99%

“…The NDF, ADF and ADL concentrations were measured according to van Soest et al (1991). N-alkanes were determined after freeze-drying according to Mayes et al (1986) after a direct saponification (Vulich et al, 1991).…”

Section: Pé Rez-ramírez Delagarde and Delabymentioning

confidence: 99%

Herbage intake and behavioural adaptation of grazing dairy cows by restricting time at pasture under two feeding regimes

Pérez-Ramírez

Delagarde

Delaby

2008

The time at pasture of dairy cows is often restricted in the context of extending the grazing season in autumn or at the end of winter. The objective of our study was to evaluate the effects of a restriction of time at pasture on milk production, herbage intake and feeding behaviour in dairy cows according to feeding regime. The four treatments consisted of 4 h or 8 h of time at pasture per day tested under two feeding regimes combining rate of supplementation and herbage allowance: either a high rate of supplementation (10 kg dry matter (DM) of a maize silage-soya bean meal mixture in the ratio 87 : 13 on a % DM basis) with a low herbage allowance (6 kg DM/cow per day above 5 cm), or a low rate of supplementation (5 kg DM of the same supplement) with a high herbage allowance (11 kg DM/cow per day). The study was carried out according to a 4 × 4 Latin square design with four 2-week periods, with 48 mid-lactation Holstein cows. The cows in the 4-h treatment had access to pasture from 0900 h to 1300 h and those in the 8-h treatment from 0900 h to 1700 h. The supplement was given at 1830 h. When time at pasture was reduced from 8 h to 4 h per day, herbage intake decreased (9.9 v. 8.1 kg DM, P < 0.001), along with a fall in milk production (22.3 v. 21.2 kg, P < 0.001) and milk protein concentration (30.1 v. 29.6 g/kg, P < 0.001), while milk fat concentration increased (39.4 v. 39.9 g/kg, P < 0.05). The effect of time at pasture on milk production was slightly more marked on the low-supplement feeding regime (interaction P < 0.06). Reducing time at pasture by 4 h led to a sharp decrease in grazing time (327 v. 209 min, P < 0.001), but strongly increased the pasture intake rate (31 v. 39 g DM/min, P < 0.001) and the proportion of time spent grazing (0.68 v. 0.87, P < 0.001). Cows showed a stronger motivation for grazing when receiving the low-supplement feeding regime. In conclusion, we showed that reducing time at pasture from 8 to 4 h for cows receiving 5 to 10 kg DM of a maize silage-based supplement decreased moderately milk production and herbage intake, because of the capacity for behavioural adaptation by the grazing dairy cows.