摘要:

AbstractThe relationship between net canopy photosynthesis (Pnc) measured at 400 J m−2s‐1and leaf area index (LAI) was determined on ryegrass‐dominant swards over a range of her bage masses in five grazing experiments. In three experiments the swards were continuously stocked either by sheep or by cattle to maintain a number of herbage heights and hence LAI values. In two experiments the swards were intermittently grazed with 21 ‐d regrowth intervals. On the continuously stocked swards measurements were made over nine periods each of 7 to 21 d in length. On the intermittently grazed swards measurements were made over six periods while the herbage was being grazed down from a high to a low LAI and over three periods during the regrowth phase.On all the swards where measurements were made while grazing was in progress, the relation of Pnc to LAI was linear. The photosynthetic rate was greater on the continuously grazed than on the intermittently grazed swards up to LAI 35 and in two experiments to LAI 5. The relationship of Pnc to LAI of swards in the regrowth phase was predominantly curvilinear and such that over much of the LAI range they had a greater photosynthetic potential than the same swards being grazed down from high to low mass. Daily rates of CO2uptake and growth in the field were calculated for one continuously stocked experiment. Both were linearly related to LAI in the range LAI 2–4·5. The agronomic implications of the results are

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01668.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractGrass silage made in late May from S24 perennial ryegrass was offeredad libitumto eight Ayshire cows in a 16‐week feeding experiment. The silage had a DM concentration of 244 g kg−1, contained 163 g crude protein (kg DM)−1with a ruminal degradability of 0.77 and had anin vitroDOMD concentration of 678 g kg−1. In addition, four concentrates each containing 167 g soya‐bean meal kg−1were consumed at a mean daily rate of 6.43 kg DM per cow. The soya‐bean meal was either untreated, or ‘protected’ by formalin and mixed in the following proportions, 100:0; 66:34; 34:66; and 0:100 respectively, in the four concentrates. The daily intakes of silage DM were not significantly different on the four treatments and averaged 90 kg DM per cow, giving a mean total daily DM intake of 32.4 g kg−1live weight. The milk yields were not significantly different on the four treatments and averaged 23.9 kg−1The treatments had small and non‐significant effects on milk composition and live weight. It is concluded that with a high‐digestibility, well‐preserved grass silage of satisfactory protein content the inclusion of ‘protected’ protein in the supplementary concentrate had no benefi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01669.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY