The nutritionally imbalanced poor-quality diet feeding is the major constraint of dairy production in tropical regions. Hence, alternative high-quality roughage-based diets are required to improve milk yield and reduce methane emission (CH4). Thus, we tested the effects of feeding natural pasture hay, improved forage grass hays (Napier and Brachiaria Hybrid), and treated crop residues (Eragrostis tef straw) on nutrient digestibility, milk yield, nitrogen balance, and methane emission. The eight lactating Fogera cows selected for the experiment were assigned randomly to a 4 × 4 Latin square design. Cows were housed in well-ventilated individual pens and fed a total mixed ration (TMR) comprising 70% roughage and 30% concentrate. The four roughage-based basal dietary treatments supplemented with formulated concentrate were: Control (natural pasture hay (NPH)); treated teff straw silage (TTS); Napier grass hay (NGH); and Brachiaria hybrid grass hay (BhH). Compared with the control diet, the daily milk yield increased (p < 0.01) by 31.9%, 52.9%, and 71.6% with TTS, NGH, and BhH diets, respectively. Cows fed BhH had the highest dry matter intake (8.84 kg/d), followed by NGH (8.10 kg/d) and TTS (7.71 kg/d); all of these intakes were greater (p = 0.01) than that of NPH (6.21 kg/d). Nitrogen digestibility increased (p < 0.01) from the NPH diet to TTS (by 27.7%), NGH (21.7%), and BhH (39.5%). The concentration of ruminal ammonia nitrogen was higher for cows fed NGH than other diets (p = 0.01) and positively correlated with plasma urea nitrogen concentration (R² = 0.45). Feeding TTS, NGH, and BhH hay as a basal diet changed the nitrogen excretion pathway from urine to feces, which can help protect against environmental pollution. Estimated methane yields per dry matter intake and milk yield were decreased in dairy cows fed BhH, NGH, and TTS diets when compared to cows fed an NPH diet (p < 0.05). In conclusion, feeding of TTS, NGH, and BhH roughages as a basal diet to lactating dairy cows in tropical regions improved nutrient intake and digestibility, milk yield, nitrogen utilization efficiency, and reduced enteric methane emission.

A low nitrogen utilization efficiency (NUE, the ratio of retained N to N intake) and high methane (CH₄) emissions of ruminants can lead to potentially high diet protein wastage and directly contribute to global warming. Diet manipulation is the most effective way to improve NUE or reduce CH₄ emissions. This study investigated how replacing oat hay with alfalfa hay (AH) or common vetch hay (CVH) with different proportions (20% (20) and 40% (40) of the total dry matter (DM) allowance) affects the body weight gain (BWG), NUE, and CH₄ emissions of crossbred Simmental cattle. The forage dry matter intake (DMI) and the total DMI of cattle fed on a CVH40 diet were significantly higher than the values for those fed on AH20 or AH40 diets (p < 0.05). There were no differences in the BWG for the four treatments observed, however, nutrient digestibility significantly decreased in the AH40 diet as compared with the AH20 diet (p < 0.05). The NUE was significantly lower in AH40 than in CVH20. The CH₄ emissions were significantly lower for the CVH40 diet than with the AH20 diet (p < 0.05). Our findings suggest that a 20% AH and 40% CVH substitution for oat hay are the optimal proportions to maintain the BWG, NUE, nutrient digestibility, and reduce the CH₄ emissions of crossbred Simmental cattle. Overall, CVH has a greater potential to reduce CH₄ emissions than AH.

めん羊の飼育期間における体脂肪組織発達に及ぼす2 種類の粗飼料給与効果を評価するため，生後3-4ヵ月齢の去勢サフォーク種7頭を供試した。 1 頭は培養前駆脂肪細胞の単離用い，6 頭のめん羊はチモシー乾草給与区（TH 区，3 頭）およびイタリアンライグラスストロー給与区（IR 区，3 頭）に分け，11 ヵ月間飼育を行った。TH 区，IR 区とも，日増体量を100 g に設定した。各粗飼料は体重の2％相当量を給与し，濃厚飼料給与量は前日の粗飼料摂取量の40％とした。飼育開始後の3 ヵ月および11 ヵ月に各区から採集した血清を脂肪細胞分化誘導培地に添加し，培養前駆脂肪細胞に7 日間処理した。飼育開始3 ヵ月後のTH 区の血清を処理した培養細胞は，IR 区の血清で処理した細胞に比べ脂質蓄積量が多く，脂肪細胞発達関連遺伝子であるPPARγ, C/EBPα, aP2 およびLPL の発現量が増加した。以上の結果は，チモシー乾草を飼育前期段階の若いめん羊に給与することがイタリアンライグラスストローを給与することに比べ脂肪組織発達に効果的であることを示す。

めん羊のエネルギー要求量を算出するために必要となる維持に要するエネルギー代謝率（qm）についてin vivo 試験により，3 試験区を設けて検討した。TH1 区ではチモシー乾草および圧ペントウモロコシを給与し（乾物ベース配合比率＝76 : 24）；TH2区ではチモシー乾草を単体給与，RS 区では稲わらおよび市販配合飼料を給与（60 : 40）した。各試験区においてqm を0.4 に設定し，維持に要する代謝エネルギーを充足する様，試験飼料を各めん羊に給与した。各試験区においてサフォーク系雑種成めん羊を3 頭供試し，全糞採取法による消化試験を実施した。また，in vitro ガス生産テストにより，供試飼料の代謝エネルギー含量を測定した。供試めん羊の供試飼料の化学成分組成および消化試験によるTDN 摂取量測定値よりGE 摂取量およびME 摂取量を算出し，エネルギー代謝率（q）を算出した。In vivo 試験によるq の推定値は0.47-0.49 であり，処理区間に差はみられなかった。In vitro ガス生産テストによるME 摂取量を用いて算出したq は0.39-0.45 であり，in vivo 試験から算出された値より低かった。維持のためのエネルギー代謝率は，低品質粗飼料給与時では0.4，高品質の粗飼料給与時では 0.5 に設定するのが適切であると示唆された。