Milk production and methane emissions from dairy cows fed silages from different grassland species and harvesting frequencies
Notice bibliographique
Résumé
The aim of this study was to examine how silages from different grassland species and harvesting frequencies affect feed intake, milk production, and methane (CH 4 ) emission in dairy cows. We hypothesized that cows consuming silages of more frequent harvest, grass species with greater OM digestibility and legumes with lower NDFom concentration would have greater silage DMI and milk yield and thereby lower CH 4 yield and intensity. Forty Norwegian Red cows were allocated to 5 treatments in a cyclic changeover design with four 21-d periods (14 d of adaptation, 7 d of data collection). The 5 treatments evaluated were silages produced from timothy ( Phleum pratense L.) in a 3-cut system (T3), timothy in a 2-cut system (T2), perennial ryegrass ( Lolium perenne L.) in a 3-cut system (PR3), red clover ( Trifolium pratense L.) in a 3-cut system (RC3) and a mix of T3 and RC3 (50:50 on DM basis; T3/RC3). The treatments were prepared by mixing silages from each crop over the growing season, proportional to the harvested DM yield of each cut. Cows were offered the mixed silages ad libitum supplemented with a fixed level of concentrate. Gas emissions were measured using 2 Greenfeed units. Milk yield was recorded in the milking robot at each visit, and milk samples were collected at 3 consecutive milkings during the last 7 d of each period. Cows were weighed after each milking, and total-tract digestibility of each diet was estimated using acid insoluble ash as internal marker in fecal grab samples. The data were analyzed using the MIXED procedure of SAS with block, period, and treatment as fixed effects and animal within block as random effect. Silage and total DMI did not differ between T3 and T2, but total DMI was lower for PR3 than for T3. There was a quadratic effect of increased proportion of red clover, with highest intakes of T3/RC3 and lower intakes of RC3 than of T3. Energy-corrected milk yield was lower for T2 than T3, and for PR3 than T3. There was a quadratic effect of increased proportion of red clover, with highest ECM yield in T3/RC3 and lower in RC3 than in T3. Organic matter digestibility was lower for T2 than T3, but it did not differ between T3 and PR3. Including red clover in the diet linearly decreased OM digestibility. Methane production (g/d) did not differ between T3 and T2, but CH 4 intensity (g/kg ECM) was greater for T2 than for T3. There was no difference between T3 and PR3 for CH 4 production but yield and intensity were greater for PR3 than T3. Including red clover in the diet linearly increased CH 4 production, yield and intensity with greatest intensity in the 100% red clover diet. In conclusion, changing harvesting frequency for timothy from 2 to 3 harvests per year did not affect CH 4 production or yield, but CH 4 intensity was reduced. Replacing timothy with perennial ryegrass and increased inclusion rate of red clover both increased CH 4 yield and intensity.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».