Effects of species-diverse high-alpine forage on in vitro ruminal fermentation when used as donor cow's feed or directly incubated

Alpine forages are assumed to have specific effects on ruminal digestion when fed to cattle. These effects were investigated in an experiment from two perspectives, either by using such forages as a substrate for incubation or as feed for a rumen fluid donor cow. In total, six 24-h in vitro batch culture runs were performed. Rumen fluid was collected from a non-lactating donor cow after having grazed pastures at ∼2000 m above sea level for 2, 6 and 10 weeks. These ‘alpine runs' were compared with three lowland samplings from before and 2 and 6 weeks after the alpine grazing where a silage-concentrate mix was fed. In each run, nine replicates of four forages each were incubated. These forages differed in type and origin (alpine hay, lowland ryegrass hay, grass-maize silage mix, pure hemicellulose) as well as in the content of nutrients. Concentrations of phenolic compounds in the incubated forages were (g/kg dry matter (DM)): 20 (tannin proportion: 0.47), 8 (0.27), 15 (0.52) and 0 (0), respectively. Crude protein was highest in the silage mix and lowest with hemicellulose, whereas the opposite was the case for fiber. The total phenol contents (g/kg DM) for the high altitude and the lowland diet of the donor cow were 27 (tannins: 0.50 of phenols) and 12 (0.27), respectively. Independent of the origin of the rumen fluid, the incubation with alpine hay decreased (P < 0.05) bacterial counts, fermentation gas amount, volatile fatty acid (VFA) production as well as ammonia and methane concentrations in fermentation gas (the latter two being not lower when compared with hemicellulose). Alpine grazing of the cow in turn increased (P < 0.001) bacterial counts and, to a lesser extent, acetate proportion compared with lowland feeding. Further, alpine grazing decreased protozoal count (P < 0.05) and VFA production (P < 0.001) to a small extent, whereas methane remained widely unchanged. There were interactions (P < 0.05) between forage type incubated and feeding period of the donor cow in protozoal counts, acetate:propionate ratio, fermentation gas production and its content of methane, in vitro organic matter digestibility and metabolizable energy. Although increased phenolic compounds were the most consistent common property of the applied alpine forages, a clear attribution to certain effects was not possible in this study. As a further result, adaptation (long-term for donor cow, short term for 24 h incubations) appears to influence the expression of alpine forage effects in ruminal fermentatio

Transfer of linoleic and linolenic acid from feed to milk in cows fed isoenergetic diets differing in proportion and origin of concentrates and roughages

The transfer of ingested α-linolenic acid (ALA) and linoleic acid (LA) determines the nutritional quality of milk, but the factors determining this transfer are unclear. The present experiment investigated the influence of roughage to concentrate proportions and the effect of concentrate types on milk fat composition. Respectively, six lactating dairy cows were fed one of three isoenergetic (5·4±0·05 MJ net energy for lactation/kg dry matter; DM) and isonitrogenous (215±3·5 g crude protein/kg DM) diets, consisting of ryegrass hay only (33 g fatty acids/kg DM; ALA-rich, no concentrate), maize (straw, whole maize pellets and gluten; 36 g fatty acids/kg DM; LA-rich; 560 g concentrate/kg DM), or barley (straw and grain plus soybean meal; 19 g fatty acids/kg DM; LA-rich; 540 g concentrate/kg DM). The fatty acid composition of feeds and resulting milk fat were determined by gas chromatography. The ALA concentration in milk fat was highest (P<0·001) with the hay-diet, but the proportionate transfer of ALA from diet to milk was lower (P<0·001) than with the maize- or barley-diets. The LA concentration in milk fat was highest with the maize-diet (P<0·05, compared with hay) but relative transfer rate was lower (P=0·01). The transfer rates of ALA and LA were reciprocal to the intake of individual fatty acids which thus contributed more to milk fat composition than did roughage to concentrate proportions. The amount of trans-11 18:1 in milk fat was lowest with the barley-diet (P<0·001) and depended on the sum of ALA and LA consumed. The milk fat concentration of cis-9, trans-11 18:2 (rumenic acid) was more effectively promoted by increasing dietary LA (maize) than ALA (hay). Amounts of 18:0 secreted in milk were four (maize) to seven (hay) times higher than the amounts ingested. This was suggestive of a partial inhibition of biohydrogenation in the maize-diet, possibly caused by the high dietary LA leve

Supplementary Table S1 - database

Data used for a meta-analysis of Mg absorption in dairy cattleTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Magnesium in dairy cattle nutrition

Supplementary Materials - data used for a meta-analysis of Mg absorption in dairy cattle and supplemental figuresTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Methods of Emulsifying Linoleic Acid in Biohydrogenation Studies In Vitro May Bias the Resulting Fatty Acid Profiles

ISSN:0024-4201ISSN:1558-930

Transfer of linoleic and linolenic acid from feed to milk in cows fed isoenergetic diets differing in proportion and origin of concentrates and roughages

ISSN:0022-0299ISSN:1469-762

A meta-analysis of effects of chemical composition of incubated diet and bioactive compounds on in vitro ruminal fermentation

This study examined the role of supplementation of several bioactive compounds (BC) and the chemical composition of the diet used as substrate for in vitro incubations, on in vitro ruminal fermentation profile and nutrient degradation. A meta-analytical approach was used to weigh the sample size used in each experiment, and account for the random effect of each as well as unequal variance among studies. A total of 20 recently conducted experiments with 354 treatments, each including one control (i.e., no BC supplementation), fulfilled the criteria for inclusion. Doses of BC supplementation varied from 0.03 to 500 mg/g dry matter (DM) of incubated diet. Contents of crude protein (CP) and neutral detergent fibre (NDF) of the incubated diets (DM basis) ranged from 139 to 189 g/kg and 160 to 420 g/kg, respectively. Results indicate that supplementation of BC linearly decreased (137.4 versus 116.5 mmol/L; P<0.05) concentration of total volatile fatty acids (VFA) and proportion of acetate (P<0.05). Also, the concentration of ammonia in the in vitro rumen fluid was lower with BC supplementation (22.9 versus 15.6 mg/dL; P<0.05). Analysis by backward elimination correlation analysis revealed that inclusion of the chemical composition of the incubated diet into the model with BC supplementation improved the accuracy of estimation of responses of fermentation variables. Thus, higher NDF and CP contents of the substrate and higher BC dosage were associated with lower concentrations of total VFA (r2 = 0.54), whereas both lower CP contents of the substrate and BC supplementation lowered the concentration of ammonia (r2 = 0.32). This analysis showed negative associations between BC supplementation and in vitro disappearance of DM and NDF, and positive correlations with dietary NDF content. In contrast, higher BC inclusion and lowering NDF content in the diet was accompanied with decreased in vitro CH4 formation (r2 = 0.21). Results indicate that BC supplementation and chemical composition of the incubated diet are determining factors which impact responses of in vitro ruminal fermentation and degradation.This study examined the role of supplementation of several bioactive compounds (BC) and the chemical composition of the diet used as substrate for in vitro incubations, on in vitro ruminal fermentation profile and nutrient degradation. A meta-analytical approach was used to weigh the sample size used in each experiment, and account for the random effect of each as well as unequal variance among studies. A total of 20 recently conducted experiments with 354 treatments, each including one control (i.e., no BC supplementation), fulfilled the criteria for inclusion. Doses of BC supplementation varied from 0.03 to 500 mg/g dry matter (DM) of incubated diet. Contents of crude protein (CP) and neutral detergent fibre (NDF) of the incubated diets (DM basis) ranged from 139 to 189 g/kg and 160 to 420 g/kg, respectively. Results indicate that supplementation of BC linearly decreased (137.4 versus 116.5 mmol/L; P<0.05) concentration of total volatile fatty acids (VFA) and proportion of acetate (P<0.05). Also, the concentration of ammonia in the in vitro rumen fluid was lower with BC supplementation (22.9 versus 15.6 mg/dL; P<0.05). Analysis by backward elimination correlation analysis revealed that inclusion of the chemical composition of the incubated diet into the model with BC supplementation improved the accuracy of estimation of responses of fermentation variables. Thus, higher NDF and CP contents of the substrate and higher BC dosage were associated with lower concentrations of total VFA (r2 = 0.54), whereas both lower CP contents of the substrate and BC supplementation lowered the concentration of ammonia (r2 = 0.32). This analysis showed negative associations between BC supplementation and in vitro disappearance of DM and NDF, and positive correlations with dietary NDF content. In contrast, higher BC inclusion and lowering NDF content in the diet was accompanied with decreased in vitro CH4 formation (r2 = 0.21). Results indicate that BC supplementation and chemical composition of the incubated diet are determining factors which impact responses of in vitro ruminal fermentation and degradation