Frequency distribution of sward height of kikuyu (Pennisetum clandestinum) grass pastures intensively grazed by dairy cows

2009 ◽  
Vol 49 (7) ◽  
pp. 574 ◽  
Author(s):  
R. C. Dobos ◽  
K. Sinclair ◽  
G. N. Hinch ◽  
W. J. Fulkerson
Keyword(s):  
Dairy Cows ◽  
Normal Distribution ◽  
Frequency Distribution ◽  
Information Criteria ◽  
Skewed Distribution ◽  
Height Measurement ◽  
Pennisetum Clandestinum ◽  
Sward Height ◽  
Log Normal ◽  
Log Normal Distribution

Swards that are grazed continuously by cattle can become heterogeneous in structure, such that frequencies of height measurements have a skewed distribution. This structure has been best described by the double-normal, gamma and Weibull distributions rather than by the more common single-normal distribution. Limited analysis of the frequency distribution of sward height under dairy cattle grazing management is available. The current paper reports the frequency distribution of sward height under intensive dairy cow grazing of kikuyu (Pennisetum clandestinum) in a subtropical environment. Frequencies of sward height were collected during an experiment designed to investigate the effects of compressed sward height and grazing duration on grazing behaviour of dairy cows. There were two compressed sward heights (10 and 13 cm; Earle and McGowan 1979) and five grazing durations (1, 2, 4, 8 and 15 h). The frequency of height measurements taken were then fitted to four distributions – single-normal, log-normal, gamma and Weibull – to determine if treatments influenced the structure of the sward as grazing duration progressed. The frequency of sward height measurement was best described by the log-normal distribution. However, no one distribution described the frequency of height measurements consistently as grazing duration progressed, as determined by Akaike information criteria. The present analysis did not provide unequivocal evidence for either bimodal or unimodal distributions describing the height measurements for 10- and 13-cm compressed sward height treatments as grazing duration progressed.

scholarly journals A Comparison of Efficiency for Homogeneity of Variance Tests under Log-normal Distribution

2021 ◽  
Vol 9 (4) ◽  
Author(s):  
Kunlanan Sritan ◽  
Bumrungsak Phuenaree
Keyword(s):  
Normal Distribution ◽  
Skewed Distribution ◽  
Type I ◽  
Jackknife Test ◽  
Power Of The Test ◽  
Bartlett’S Test ◽  
Homogeneity Of Variance ◽  
Log Normal ◽  
Skew Distribution ◽  
Log Normal Distribution

In this paper, we compare five homogeneity of variance tests which are Bartlett’s test, Levene’s test, Cochran’s test, O’Brien’s test and Jackknife test. Considering their ability to control probability of type I error and the power of the test, when groups of population are distributed in log-normal distribution. The equal sample sizes are defined as 10, 15, 30 and 50 at the significance is 0.05. The results show that the Levene’s test become the best test for the high skewed distribution. For the lowed skew distribution, the Cochran’s test is the best test when a variance of group is different to the others. Moreover, Bartlett’s test provides the highest power when variances of all populations are different.

A study of marriage and mobility in Reading, England

1979 ◽  
Vol 11 (4) ◽  
pp. 369-389 ◽  
Author(s):  
D. A. Coleman
Keyword(s):  
Normal Distribution ◽  
Geographical Distribution ◽  
Frequency Distribution ◽  
Response Rate ◽  
Married Couples ◽  
Basic Data ◽  
Geometric Means ◽  
Electoral Register ◽  
Log Normal ◽  
Log Normal Distribution

SummarySurvey of recently married couples was carried out in Reading, Berkshire, UK in 1974. Its purpose was to provide information about the geographical and social origins of marriage partners, and to show how the town's social and geopraphical features might influence marital choice.A list marriage certificate was preferred to the electoral register as a sample frame. Despite a lower than usual response rate the method was judged successful. Basic data on the geographical distribution of the husband and wife are given here, together with the fitting of the aggregate frequency distribution of distances to the log-normal distribution and their summary description in terms of the geometric means.

scholarly journals A Universal Model for the Log-Normal Distribution of Elasticity in Polymeric Gels and Its Relevance to Mechanical Signature of Biological Tissues

Biology ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 64
Author(s):  
Arnaud Millet
Keyword(s):  
Elastic Modulus ◽  
Normal Distribution ◽  
Biological Tissues ◽  
Force Microscopy ◽  
Polymeric Gels ◽  
Atomic Force ◽  
Clear Explanation ◽  
Log Normal ◽  
Log Normal Distribution

The mechanosensitivity of cells has recently been identified as a process that could greatly influence a cell’s fate. To understand the interaction between cells and their surrounding extracellular matrix, the characterization of the mechanical properties of natural polymeric gels is needed. Atomic force microscopy (AFM) is one of the leading tools used to characterize mechanically biological tissues. It appears that the elasticity (elastic modulus) values obtained by AFM presents a log-normal distribution. Despite its ubiquity, the log-normal distribution concerning the elastic modulus of biological tissues does not have a clear explanation. In this paper, we propose a physical mechanism based on the weak universality of critical exponents in the percolation process leading to gelation. Following this, we discuss the relevance of this model for mechanical signatures of biological tissues.

Grazing behaviour and pattern of intake of dairy cows grazing kikuyu (Pennisetum clandestinum) grass pastures in relation to sward height and length of grazing session

2009 ◽  
Vol 49 (3) ◽  
pp. 233 ◽  
Author(s):  
R. C. Dobos ◽  
W. J. Fulkerson ◽  
K. Sinclair ◽  
G. N. Hinch
Keyword(s):  
Dairy Cows ◽  
Grazing Management ◽  
Feeding Strategies ◽  
Intake Rate ◽  
Pennisetum Clandestinum ◽  
Sward Height ◽  
Rate Of Increase ◽  
Grazing Period ◽  
The Difference ◽  
Strip Grazing

To investigate how grazing time, herbage dry matter intake (DMI) and intake rate (IR) are influenced by intensive grazing management, dairy cows strip-grazing subtropical grass pastures (Pennisetum clandestinum) at two compressed sward heights (10 and 13 cm) and at five grazing durations (1, 2, 4, 8 and 15 h) and replicated over 3 days were studied. The study was conducted in summer and the cows were observed every 20 min from 1600 to 0700 hours to calculate the time spent (min/h) grazing, ruminating and resting. Total time spent grazing was 45 min longer for cows grazing the 13-cm sward than for those grazing the 10-cm sward over the 15-h grazing period. The rate of increase in grazing time was 0.64 h/h grazing duration up to 4 h after introduction to fresh pasture. IR of cows grazing the 13-cm sward was significantly higher than those grazing the 10-cm sward (0.17 v. 0.12 kg DM/min spent grazing). The difference in IRs between sward height treatments resulted from the higher DMI in the 13-cm sward within the first 4 h of grazing compared with the 10-cm sward, although following the first 4-h grazing period IR was similar for both sward heights. Grazing time increased with sward height up to a maximum of 4 h after introduction to fresh pasture and had also maximised herbage DMI by this time. These results have important practical implications for dairy cow grazing management systems because they show that dairy managers could remove cows after 4 h with little compromise in production and will help in developing optimum supplementary feeding strategies when pasture availability limits DMI.

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