Energy and Matter Flows in Bahiagrass Pasture : VI. Nitrogen excretion in dung and urine by Holstein heifers

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  • バヒアグラス放牧草地におけるエネルギーと物質の流れ : VI. 乳用育成牛のふんおよび尿による窒素排泄量について
  • バヒアグラス放牧草地におけるエネルギーと物質の流れ-6-乳用育成牛のふんおよび尿による窒素排泄量について
  • バヒアグラス ホウボク ソウチ ニ オケル エネルギー ト ブッシツ ノ ナガ

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Abstract

Bahiagrass, (Pasplum notatum Flugge.), pasture (0.18 ha) was grazed eight times during the grazing season (May-Oct.) in 1983 by 21-24 Holstein heifers under rotational system with 2-4 week intervals. Amount of excreted N was estimated by following equations ; dung-N (g N/head/day)=weight of dung pat (g/pat)×No. of dung pat (pat/head/day)×N concentration of dung (%) and urine-N (g N/head/day)=volume of urine (l/urination)×No. of urination (No./head/day)×N content of urine (g N/l) 1. Amount of excreted dung-N and urine-N was much varied with grazing Nos. Differences in dung-N were largely dependent on the variations in weight of dung pat and No. of dung pat, and those in urine-N were resulted from changes in all of the determinants in the above equation. 2. Significant positive correlation was found between the amount of excreted dung-N and dry matter intake (r=0.946^*), and nitrogen intake (r=0.945^*), whereas the amount of urine-N was significantly related to mean liveweight (r=0.981^<**>), and metabolic body size (r=0.982^<**>) of heifers. 3. Amounts of excreted dung-N and urine-N during the grazing season were 101.0 kg/ha and 95.9 kg/ha, respectively. The pasture being grazed recieved 86% of dung-N and 78% of urine-N, and the remainder of 14% and 22% was deposited on the pasture served to resting for the herd (resting place). 4. The investigation suggested that a certain amount of excreted N was not recycled in the pasture through the deposition of excreta on the resting place. Especially in summer, percentage deposition of excreta on the resting place was higher and it was accounted that presumably less than 40% of excreted N were recycled in this season.

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