- Lick intake by Sheep
|Last update: April 2, 2012 08:49:54 AM|
Lick intake by Sheep
G A Jacobs
Agricultural Researcher: Small Stock
Grootfontein College of Agriculture
The use of supplements or licks for grazing sheep is a general practice in South Africa. The theory of successful lick feeding assumes that each animal gets its proper share. There has however been little study on the extent to which lick intakes of individual animals within a group vary. Australian research workers used chromic oxide as a marker and studied individual intakes of lick blocks containing molasses and urea (Lobato, Pearce & Tribe, 1980). They found an average daily lick intake of 17 ± 24g with a minimum of zero intake and a maximum of 105g per sheep per day. This means that the highest intake was six times the group average.
From these facts it is clear that more information on individual lick intakes is essential.
The aim of this experiment was to determine the pattern of lick intake of individual sheep on Karoo veld.
From two months before commencement of this experiment, all sheep received a lick consisting of salt and mealiemeal to accustom them to this type of supplement. The supplement was supplied to the sheep in two 200Q drums cut open in length. The grazing capacity was one sheep to four hectare. The veld was in a moderate to a little under moderate condition, according to visual estimation.
The lick consisted of 40% common salt and 60%mealiemeal. The mielies were hammermilled through a 6mm sieve and were then mixed with fine salt. The salt was just fine enough to prevent the sheep from selecting against salt lumps or larger grains.
The experiment was conducted with 30 adult Merino wethers at the Carnarvon Experimental Farm. All sheep had free access to the lick right around the clock. Then, for two periods of 24 hours (1980-08-11 and 1980-10-07) the lick was replaced by the selfsame lick but this time containing 8,8% moisture to which tritiated water was added to serve as a marker. The level of this radioactive moisture in the mealiemeal was so low that it could not have any effect on the sheep. By measuring the amount of radioactivity in the blood of each sheep, is very precise estimate of its lick intake could be calculated.
The 30 sheep were arranged in order of lick intake and these intakes, with standard deviations, are shown in Fig. 1. Four sheep consumed nothing and are not indicated in Fig. 1. When the standard deviation of individual lick intake is considered (Fig. 1), it is clear that there is a tendency for individual sheep to stick to their level of lick intake. From the results of Lobato et al (1980) it is clear that this conclusion is not true when different supplements are compared. They found no significant correlation between the intake of three supplements by individual sheep. Thus, a sheep that was a large consumer of hay, for example, was not necessarily a large consumer of concentrates in the form of whole grain or in the form of lick.
Further analysis of the results in Fig. 1 show that 13% of the sheep did not consume any lick. On the first of the two experimental days, eight sheep consumed nothing. On the second day, again, eight sheep consumed nothing, but only four non-consumers corresponded to those of the previous day. Thus when the experimental time was doubled, the non-consumers changed from 27 to 13%, and one can therefore expect this percentage to be less than 13 over longer periods. These results accord well with those of Lobato et al. (1980), who reported that 9% of the sheep consumed nothing over a period of one week.
The average lick intake of sheep no. 1 (Fig. 1) was 84g per day. This was four times the average group intake of 21g per day. This considerable variation between sheep is however a bit less than that reported by Lobato et al. (1980). They reported individual intakes of six times the group average. For this study the average and standard deviation of lick intake of the group was 21 ± 22g/day compared with 17 ± 24g/day reported by Lobato et al. (1980). The greater variation of Lobato et al. (1980) could perhaps partly be ascribed to the fact that they used licks in block form.
Further research is necessary to determine the influence of different methods of feeding management on the variation in individual lick intake. From available research findings a method of management which will alleviate the problem has already emerged. In Table 1 different quantities of supplement intake are compared for individual grazing sheep. The coefficients of variation show that the variation in supplement intake was the smallest in the two cases where the larger quantities were supplemented daily. When the results of the present study are considered in combination with the work of Lobato et al (1980), it is clear that less variation in supplement intake occurred at higher intakes.
Lick consumption varies considerably between sheep on Karoo veld. The greatest variation occurs at relatively low levels of supplement intake, for example, less than 150g per sheep per day. To lower the variation in individual intake it would probably be a sound procedure to supplement relatively large quantities, for example, 350 to 400g per sheep per day. To minimise costs, this supplementation should then only be given during the most critical dry periods to the most vulnerable stock.
I wish to express my sincere gratitude to Messrs A Koen, J A N Cloete and W F Immelman for their technical assistance during this study.
LOBATO, J F P., PEARCE, G.R. &TRIBE, D E., 1980. Measurement of the variability in intake by sheep of oat grain, hay and molasses-urea blocks using chromic oxide as a marker. Aust. J. Exp. Agric. Anim. Husb. 20, 413-416.
Karoo Agric 2 (2), 21-22