Voluntary intake and in vivo digestibility of forages from semi-natural grasslands in dairy cows

To study in vivo digestibility of forages from semi-natural grasslands two experiments were carried out. In the first experiment lactating dairy cows were offered three different silage-based diets. Silage originated from intensively managed grassland (IM), extensively managed species-poor grassland (SPP), or extensively managed species-rich grassland (SPR). In the second experiment lactating dairy cows were offered IM or a diet in which part of the IM had been replaced by 20% SPP (20SPP), 60% SPP (60SPP) or 60% SPR (60SPR). Intake was significantly lowest on diets with SPP, but intake on diets with SPR was not significantly lower than intake on IM. In both experiments gross energy and in vivo digestibility of organic matter, crude protein and neutral detergent fibre were highest for IM. In the first experiment SPP had a significantly higher digestibility than SPR, but in the second experiment differences in digestibility between 60SPP and 60SPR were not statistically significant. In both experiments in vivo digestibility was almost similar to in vitro digestibility, but no suitable equation could be found to estimate in vitro or in vivo digestibility from the chemical composition. Although digestibility and crude protein content were significantly lower for SPR than for SPP, intake of digestible organic matter appeared to be higher. It was concluded that there appears to be more scope for silage from extensively managed species-rich than for silage from extensively managed species-poor grasslan

Dairy cow performance on silage from semi-natural grassland

The effects of including forage from semi-natural grassland in the diet of dairy cows were studied in a feeding trial with cows in mid-lactation. Diets were compared in which part of the silage from intensively managed grassland was replaced with 0% (100IM), 20% (20SPP), 40% (40SPP) or 60% (60SPP) silage from species-poor semi-natural grassland or with 60% silage from species-rich semi-natural grassland (60SPR). On a dry matter basis, the total mixed ration (TMR) contained 63% grass silage, 18% maize silage and 19% concentrates. Concentrates were either low or high in protein to prevent protein surpluses or shortages. High producing cows were offered additional concentrates in concentrate boxes. The additional concentrates had the same composition as the concentrates in the TMR. With the 60SPP diet voluntary daily intake decreased by 1.4 kg DM cow−¹ day−¹. Uncorrected milk production was the same for all diets, but milk fat yield was lower with the 60SPP diet and milk protein yield lower with the 60SPR diet than with the other diets. No statistically significant differences in fat and protein corrected milk production were observed between the 100IM and the 20SPP diet. The fat and protein corrected milk production with the other diets was significantly lower than with 100IM. All cows gained body weight, but there were no statistically significant differences between diets. In conclusion, if used in low quantities (< 40%), silage from semi-natural grassland can be included in the diet of lactating dairy cows without reducing production. This conclusion is based on the presented results and cannot be generalized

Effect van graasduur op grasklaver en snijmaïsopname en op de stikstofuitscheiding in de urine = The effect of grazing time on the intake of grass/clover and silage maize and on the production of urine nitrogen

The report describes research into the optimum grazing time from the production and environmental points of view. An experiment has been carried out with limited and very limited grazing. Treatment influenced the intake of grass/clover mixture and maize silage as well as the composition of urin

Fermentation and degradation in the rumen of dairy cows fed on diets consisting of silage from an intensively managed sward and silages from semi-natural grassland

To assess the effect of grassland management on the ruminal digestion of silages, four lactating dairy cows, fitted with a rumen cannula, were fed diets consisting of concentrates and different grass silages. The grass silages consisted of intensively managed grass (IM) in variable proportions replaced by silages harvested from a 'species-poor' grassland managed to stimulate nesting of birds (SPP) or from a grassland managed to increase plant species diversity (SPR). The roughage part of the diets was composed completely of IM (100IM), or 200 g/kg (in dry matter) of IM replaced by SPP (20SPP) or 600 g/kg of IM replaced by SPP (60SPP), or SPR (60SPR). The pH in the rumen was highest on 60SPR and lowest on 100IM and 20SPP (P <0(.)05), whereas volatile fatty acids (VFA) concentrations were lowest on 60SPP and 60SPR and highest on 100IM (P <0(.)05). No differences in the ratio non-glucogenic:glucogenic volatile fatty acids were observed among the diets. The NH3 concentration was highest on 100IM and 20SPP and lowest on 60SPR (P <0(.)05), reflecting differences in CP intake. The concentration of uric acid in the urine (mg per kg metabolic body weight) was highest on 100IM (P <0(.)05). Rumen pool size of OM and DM did not differ among treatments, but pool size of NDF and IADF were highest on 60SPR (P <0(.)05). Passage rate was high on 100IM and 60SPR, but no significant differences with the other treatments were established. Also, no significant differences were observed in rates of degradation. Clearance rate of large particles was highest on 60SPP and differed significantly from 60SPR (P <0(.)05) only. No differences were observed in clearance rate of small particles. In conclusion, for most rumen fermentation characteristics measured in the study, no noticeably aberrant behaviour of the silages from semi-natural grassland was observed

Susceptibility to chronic mucus hypersecretion, a genome wide association study

Background: Chronic mucus hypersecretion (CMH) is associated with an increased frequency of respiratory infections, excess lung function decline, and increased hospitalisation and mortality rates in the general population. It is associated with smoking, but it is unknown why only a minority of smokers develops CMH. A plausible explanation for this phenomenon is a predisposing genetic constitution. Therefore, we performed a genome wide association (GWA) study of CMH in Caucasian populations. Methods: GWA analysis was performed in the NELSON-study using the Illumina 610 array, followed by replication and meta-analysis in 11 additional cohorts. In total 2,704 subjects with, and 7,624 subjects without CMH were included, all current or former heavy smokers (≥20 pack-years). Additional studies were performed to test the functional relevance of the most significant single nucleotide polymorphism (SNP). Results: A strong association with CMH, consistent across all cohorts, was observed with rs6577641 (p = 4.25x10-6, OR = 1.17), located in intron 9 of the special AT-rich sequence-binding protein 1 locus (SATB1) on chromosome 3. The risk allele (G) was associated with higher mRNA expression of SATB1 (4.3x10 -9) in lung tissue. Presence of CMH was associated with increased SATB1 mRNA expression in bronchial biopsies from COPD patients. SATB1 expression was induced during differentiation of primary human bronchial epithelial cells in culture. Conclusions: Our findings, that SNP rs6577641 is associated with CMH in multiple cohorts and is a cis-eQTL for SATB1, together with our additional observation that SATB1 expression increases during epithelial differentiation provide suggestive evidence that SATB1 is a gene that affects CMH

Forages from intensively managed and semi-natural grasslands in the diet of dairy cows

Keywords : Intensively managed grass, semi-natural grasslands, forage species, dairy cows, in vivo digestibility, feed degradation, energy metabolism, milk production, ruminant nutrition, rumen fermentation, rumen kinetics, voluntary intake, feed evaluation This thesis focuses on the nutritional value of grass from intensively managed as well as semi-natural grasslands in diets fed to dairy cows. Aims were to explain why performance of dairy cows, fed intensively managed grass, is lower than expected based on their calculated energy intake, and to obtain knowledge on the nutritional value of forages from semi-natural grasslands if fed to dairy cows. In order to understand the reason for the overestimation of the performance of dairy cows, several feeding and respiration trials were collected. From the feeding trials it was concluded that there was a discrepancy between energy input in grass and concentrates and energy output in milk and maintenance. This was due to the composition of grass and diet, but also due to higher maintenance requirements on grass-based diets than currently assumed. In the respiration trials it was observed that maintenance requirements for dairy cows on grass-based diets should be increased by 10%. This increase was attributed to nitrogen excretion and energy required for digestion. The digestibility of forages from semi-natural grasslands is often low, due to a delayed harvesting date, and thus an advanced stage of maturity. However, though the ( in situ and in vitro ) degradation rate of mature grasses was low, the degradation rate of some dicotyledonous species appeared to be high. Also the intake of silage from semi-natural grasslands, with high proportions of dicotyledonous species was observed to be relatively high, especially when compared to the intake of silages from semi-natural grasslands mainly consisting of grasses in an advanced stage of maturity. The milk production of diets containing large proportions of semi-natural silages was low compared to diets containing mostly intensively managed grass. In vivo digestibility of forages from semi-natural grasslands was approximately similar to the in vitro digestibility. Digestibility could not be estimated based on chemical composition. Rumen fermentation of semi-natural forages did not deviate from expectations based on the chemical composition of the diet. However, a study of the rumen kinetics showed that diets containing large proportions of dicotyledonous species had a higher intake rate and passage rate than expected, and diets containing large proportions of mature grasses had a faster particle size reduction than expected. Also on forages from semi-natural grasslands, maintenance requirements should be increased, due to required energy for nitrogen excretion and for chewing and rumination. For intensively managed grass as well as for forages from semi-natural grasslands, a correction of the energy value of grass, by correcting for the surplus of protein per kg grass, is suggested, together with an increase of maintenance requirements by 10% for digestion and rumination. Including forages from semi-natural grasslands in diets of dairy cows is possible, especially if the forages are fed in small amounts. Replacement of intensively managed grass by forages from semi-natural grasslands until a maximum of 30% seems to offer best possibilities.</p

Werking van stikstof uit runderdrijfmest = Efficiency of nitrogen in cattle slurry

In het officiële bemestingsadvies voor grasland is de werking van stikstof (N) in runderdrijfmest verdeeld over sneden na toediening van deze mest. Er is twijfel gerezen over de juistheid van deze verdeling. Om de werkelijke verdeling van de werkingscoëfficiënt van runderdrijfmest over het seizoen te kunnen bepalen is er een aantal reeds uitgevoerde proeven geanalyseerd waarin runderdrijfmest met de zodebemester is toegediend. De proeven waren een Vel & Vanla proef, een compostproef, een NP werkingsproef en een zodebemestingsproef. De Vel&Vanla proef is uitgevoerd op twee locaties op zandgrond tussen 1999 en 2002 en had als doel het vaststellen van het effect van het gebruik van toevoegmiddelen op stikstofbenutting van drijfmest, bodemvruchtbaarheid en droge stofproductie. De compostproef is uitgevoerd op twee locaties op zandgrond in 2000 en 2001, met als doel de bemestende waarde van N uit compost te kwantificeren. De NP werkingsproef is uitgevoerd op kleigrond en op zandgrond in 1999 en 2000 en had als doel de stikstof- en fosfaatwerking van runderdrijfmest onder verschillende teeltomstandigheden te bepalen. De zodebemestingsproef, tenslotte, is uitgevoerd op zandgrond, op kleigrond en op veengrond tussen 1989 en 1991 en had als doel een inschatting te maken van de bemestende waarde van runderdrijfmest aangewend met de zodebemeste

Werking van stikstof uit runderdrijfmest = Efficiency of nitrogen in cattle slurry

In het officiële bemestingsadvies voor grasland is de werking van stikstof (N) in runderdrijfmest verdeeld over sneden na toediening van deze mest. Er is twijfel gerezen over de juistheid van deze verdeling. Om de werkelijke verdeling van de werkingscoëfficiënt van runderdrijfmest over het seizoen te kunnen bepalen is er een aantal reeds uitgevoerde proeven geanalyseerd waarin runderdrijfmest met de zodebemester is toegediend. De proeven waren een Vel & Vanla proef, een compostproef, een NP werkingsproef en een zodebemestingsproef. De Vel&Vanla proef is uitgevoerd op twee locaties op zandgrond tussen 1999 en 2002 en had als doel het vaststellen van het effect van het gebruik van toevoegmiddelen op stikstofbenutting van drijfmest, bodemvruchtbaarheid en droge stofproductie. De compostproef is uitgevoerd op twee locaties op zandgrond in 2000 en 2001, met als doel de bemestende waarde van N uit compost te kwantificeren. De NP werkingsproef is uitgevoerd op kleigrond en op zandgrond in 1999 en 2000 en had als doel de stikstof- en fosfaatwerking van runderdrijfmest onder verschillende teeltomstandigheden te bepalen. De zodebemestingsproef, tenslotte, is uitgevoerd op zandgrond, op kleigrond en op veengrond tussen 1989 en 1991 en had als doel een inschatting te maken van de bemestende waarde van runderdrijfmest aangewend met de zodebemeste

Energy evaluation of fresh grass in the diets of lactating dairy cows

The discrepancy between the estimated feeding value of fresh grass and the output per kg grass in terms of milk and maintenance was studied by evaluating 12 experiments with grass-fed dairy cows. The percentage grass in the diets varied between 40 and 90. Intake and milk production were recorded daily. Per treatment a number of parameters relating to the composition of the grass, characteristics of the animals, and composition of the total diet were determined. The correlation between each of these parameters and the measured discrepancy was calculated. The digestible organic matter in the grass (DOM), intake of grass, intestinal digestible protein in the total diet, percentage milk protein and body weight gain correlated well with the discrepancy. It was concluded that energy input from grass and energy output in milk production were significantly different (P < 0.05). For the diets with 80–90␐rass a high DOM increased discrepancy. It was furthermore concluded that the maintenance requirements of lactating dairy cows fed grass-based diets are probably higher than the currently used values This was ascribed to energy requirements in the gastro-intestinal tract and to nitrogen excretio

Enery evaluation of fresh grass in the diets of lactation dairy cows

The discrepancy between the estimated feeding value of fresh grass and the output per kg grass in terms of milk and maintenance was studies with grass-fed dairy cows. It was concluded that energy input from grass and energy output in milk production were significantly different. It was futhermore concluded that the maintenance requirements of lactating dairy cows fed grass-based diets are probably higher than the currently used values