Total Grazing Time Research Articles

Ingestive behaviour in sheep under field conditions

Grazing behaviour of sheep was examined over a period of 2 years (March 1975–March 1977) by means of 8 24 h vibracorders attached to the neck of 2 animals. The relationships between total walking time and the length of grazing periods were initially calculated in the same animals using an 8 3 h modified vibracorder which permitted a continuous record of the jaw movements. Grazing activity was largely confined to the daytime, and the onset of grazing was closely correlated with sunrise. Grazing was concentrated during the whole daylight time available from November to February and total grazing time reached greatest levels in spring and autumn when most herbage was available. The day/night ratio of grazing was modified by unusually hot temperatures but remained unchanged during wet weather. It was concluded that the distribution patterns of grazing were more closely related to patterns of daylight than to herbage availability which affected the duration of ingestive behaviour.

THE AUTOMATIC RECORDING OF THE GRAZING BEHAVIOUR OF DAIRY COWS

ABSTRACTA technique for the automatic recording of the grazing behaviour of dairy cows was investigated, using ‘Vibracorders’ which transmit grazing movement via a pendulum and stylus to a 24 h recording chart. The total labour input was 2 h/day for 6 cows, which gave 144 h of results. In 2 months, 3312 h of recording were obtained. Total grazing time per cow in 24 h was 559 min. on a rigid rotational system of grazing and 638 min. on a system of set stocking. Grazing time was significantly and negatively related to the yield of available herbage DM. It is concluded that if the Vibracorders are sealed and fitted correctly, they are simple, reliable and accurate instruments for automatically measuring the grazing behaviour of dairy cows.

The natural regulation of buffalo populations in East Africa: The food supply as a regulating factor, and competition*

SummaryEvidence is presented to show that both the quality and quantity of food available to a buffalo population falls below the minimum maintenance requirements of that population at certain times of the year. In the Serengeti grasslands there was a shortage of the only good quality component, grass leaf, in the dry season, with the result that the animals consumed an increasing proportion of poor quality food such as grass stem. By the end of the dry season the diet had dropped in quality below the minimum maintenance level. In areas such as Mt. Meru where there was a more continuous growing season, the high density of animals kept the standing crop of leaf at a low level. During the cooler dry season the growth of leaf became insufficient in quantity for the maintenance requirements of the population. These two quite different situations suggested that food shortage was a more general phenomenon in eastern Africa.Various measurements of feeding behaviour were made. Total grazing time per 24 h did not differ between seasons but ruminating time may have increased as the season became drier and could have been a response to the more fibrous food. Analysis for cycles of activity showed that there was more temporal organization during the dry season. These changes in activity cycles appeared to be related to the increase in energy expenditure produced by heat stress and sweating. Old animals with poor teeth did not compensate for the poor food supply by changing their feeding behaviour.There was a positive relationship between annual rainfall and mean crude density in different areas of eastern Africa, indicating that regulation was taking place. Since rainfall determined the amount of available food, it could have operated through the food supply. On a finer scale it was found that the extent of the preferred riverine habitats was also related to density. Thus rainfall, the extent of riverine habitat and perhaps soil moisture were three limiting factors that determined mean density and all could have taken effect through the food supply.As a result of initial selective grazing the amount of available leaf declined as the dry season progressed to the extent that by the end of the season the proportion of this component in the diet fell to a very low level. The impact of the population on its limited food supply indicated that intra‐specific competition was acting as the cause of regulation. Measurements of wildebeest eating the same food in the same habitats as buffalo showed that inter‐specific competition was also taking place. A small proportion (7“) of the wildebeest population could have reduced the buffalo population by approximately 18o,‘, from its potential population size.The buffalo population in the Serengeti was regulated by adult mortality which was caused by undernutrition as a result of food shortage. This food shortage was caused by intra‐ and inter‐specific competition. The effect of predation and disease was to hasten the response of the population to changes in the food supply. The limiting factors determining the mean level of the available food were, amongst others, rainfall, soil moisture and the extent of the preferred riverine habitat. The effect of interspecific competition could result in a complex regulation of populations through their food supply. There appears to be no foundation for hypotheses which invoke over‐utilization or damage as a consequence of regulation through food.

Observations on the grazing behaviour of lactating dairy cattle in a sub-tropical environment

1. Three trials are reported in which the grazing behaviour of separate groups of cows, one receiving supplementary food, either as conserved roughage, concentrate or fodder crop, was observed over 24 hr. periods. A fourth trial, assessing the effect of summer temperatures on unshaded milking cows, is briefly described.2. In trials 1 and 2 the stall feeding of either conserved roughage or concentrate reduced grazing as compared with unsupplemented cows by approximately 10%.3. Allowing access to a fresh ‘strip’ of a fodder crop at a set time each day, whilst not altering total grazing time, very markedly altered periodicity of grazing. Cows delayed grazing up to 3 hr. whilst awaiting a fresh ‘strip’.4. Environmental temperatures up to 87° F. did not alter total grazing time as compared with grazing time when temperature reached a maximum of only 70° F.5. The value of supplementary feeding of dairy cattle at pasture, at least where the intake of pasture is sufficient for maintenance and a low level of production, appears to be open to question.

Studies on the Northern Rhodesia Hyparrhenia veld Part I. The grazing behaviour of indigenous cattle grazed at light and heavy stocking rates

1. The normal pattern of grazing behaviour of free-range indigenous cattle under conditions of lenient stocking and overstocking has been studied throughout the year.2. There was a fairly fixed daily pattern of herd behaviour. The cattle usually started day grazing round sunrise and ceased approximately 1 hr. after sunset. There was a morning and afternoon peak of intense grazing activity separated by a rest period and watering about midday. There was usually one peak of night grazing.3. The average daily grazing times varied from 8 hr. during the rains period of relative feed abundance, to about 13 hr. during the dry season period of malnutrition.4. During the dry season there were no major differences in grazing times between the leniently stooked and overstocked groups. Both herds were losing weight.5. The relatively greater weight gains of the overstocked herd compared with the leniently stooked group during the rains resulted from the increased grazing times of the overstocked herd.6. The night grazing remained fairly constant at approximately 20% of the total daily grazing time.7. There were no seasonal effects on the pattern of grazing behaviour. High daytime temperatures did not cause an increase in the proportion of night grazing of indigenous cattle.