Experiments on the nutrition of the dairy heifer. II. Experimental methods in short-term experiments

Abstract

1. Data from twenty-four short-term trials on the nutrition of dairy heifers have been used in a study of the effects of management, method of estimation of live-weight gain, length of experimental period, covariance analysis and the use of monozygous twins upon experimental error.2. The value of rigid adherence to a routine and allowing ample time for the animals to settle down before the trial have been demonstrated.3. Error standard deviations were associated with length of experimental period, those for 42-day periods being about half those per 21-day periods, but were not appreciably correlated with initial live weight.4. No advantage could be demonstrated for the use of monozygous twins, or covariance analysis with initial weight or rate of gain, indicating that genetic effects contributed little to the error in experiments lasting 3–6 weeks.5. There was no significant difference between errors in live-weight gains calculated from the regression of live weight on time, from single initial and final weights, or from two initial and final live weights, indicating that deviations from linear regression are not solely in the nature of random day to day fluctuations in live weight.

The water intake of milking cows grazing Pangola grass (Digitaria decumbens Stent.) under wet- and dry-season conditions in Trinidad

“…Within this large weight range there was no correlation between liveweight of the cow and daily total water intake. This finding agrees with the finding of Rollinson, Harker & Taylor (1955), working with Zebu cattle in Uganda, but does not support the work of Bailey & Broster (1958) who established that water consumption of European type stock increased by 0-0075 gal. for every one pound increase in live weight.…”

Some effects of wintering yearling beef cattle on different planes of nutrition: I. Live-weight gain, food consumption and body measurement changes during the winter period and the subsequent grazing period

“…Dodsworth (1958) suggests that it may be economical to feed only a little above maintenance level when cattle are first housed. From the experimental point of view, however, the suggestion of Bailey, Broster & Burt (1958) of allowing animals ample time to settle down before commencing a trial is particularly sound, and it appears that a period of approximately 1 month would be necessary to do this.…”

Short-term fluctuations in the live weight of identical twin cattle

“…This range of estimates can be compared with the estimates of King (1953) of 11 -3 kg 2 for the variance of weights taken at the same time of day on consecutive days, Patterson (1947) of about 8-2 to 10-3 kg 2 and Bailey et al (1958) of 4-1 kg 2 for animals unadapted to a fixed routine decreasing to 1*6 kg 2 when animals become adapted. The greater part of this 3-day variation is due to hour-to-hour variation (11-6 kg 2 ) and to the interaction of hours and days with periods (1-1 and 2-3 kg 2 respectively).…”

“…Previous studies of the repeatability of a single weighing and the mean of three consecutive daily weighings have been made by Lush, Christensen, Wilson and Black (1928) and Patterson (1947), and by Bailey, Broster and Burt (1958) with special reference to feeding trials. Previous studies of the repeatability of a single weighing and the mean of three consecutive daily weighings have been made by Lush, Christensen, Wilson and Black (1928) and Patterson (1947), and by Bailey, Broster and Burt (1958) with special reference to feeding trials.…”