In tropical regions growth rates of animals maintained under extensive grazing systems fluctuate because of seasonal patterns of forage growth. During the dry season both quality and quantity of forages available to livestock declines and this is accompanied by a decrease or even loss of live weight, however animals are able to grow rapidly and recover body weights by having higher than normal rates of gain when given liberal amounts of feed, after periods of restriction has been eliminated. This phenomenon is termed compensatory growth (Wilson and Obsourn, 1960).
Compensatory growth is a controversial subject; the reported observations vary from one study to another. Conflicting conclusions undoubtedly have resulted from differences in: (a) the species of the animals studied and their physiological peculiarities; (b) the degree of maturity of the animal at the time deprivation and rehabilitation were imposed; (c) the nature and severity of under nutrition and the duration of the period of under nutrition; (d) the physiological requirements of the various tissue groups during the time under nutrition and refeeding were imposed and (e) the breed or sex of animals.
This study was undertaken to examine the effect of the compensatory growth on the performance of Sudanese female goats.
MATERIALS AND METHODS
Experimental animals: Thirty female Nubian goats were used in this experiment.
Animals were selected according to their age (9-12 month) and weight which was
approximately 16.5 Kg. Goats were ear-tagged and given an adaptation period
of four weeks. During this period goats were fed groundnut haulm and a mixture
containing equal percentages of assigned experimental rations ad libitum.
Spraying with an acaricide solution against ectoparasites and deworming with
thiobenzol as a drench solution was performed, the thiobenzol treatment was
repeated after 15 days. Immediately after the adaptation period the animals
were individually weighed and then randomly divided into tow groups (A and B)
of similar number and weight and each group was separately penned.
Feeds and feeding: Tow iso-nitrogenous diets, contains tow levels of dietary energy (11.5 and 8.5 Mj/KgDM) were used. The ingredient proportions and calculated chemical analysis of experimental diets are given in Table 1. During the feeding period animals were fed the assigned diets ad libitum.
Conduct of the experiment: The experiment was divided into two terms, first term which was lasted in 105 days, and second term in which seven goats from the second group (B) were refed with the highest dietary energy diet (11.5 Mj/KgDM).These goats were kept until they reach the final weight obtained by the first group (A), they spent 175 days to reach that weight.
Data collection: Performance data which include, feed intake, live weight gain and feed conversion efficiency was calculated.
proportion and chemical composition of Experimental diets
according to Ministry of Agriculture, Fisheries and Food, London, U.K.
Statistical analysis: The data was analyzed by student t-test according to (Snedecor and Cochran, 1980).
Performance data: As shown in Table 2, there was no significant
difference in initial weight and final live weight which was the determined
the target weight. Total live weight was slightly lower in the compensated group,
while the weekly rate of gain and daily weight gain were significantly (p<0.001)
decreased in the compensated group than in the first group. Fig.
1 and 2 clearly show live weight growth and daily gain
of the first and the compensated goat groups. Total dry matter intake and daily
feed intakes were significantly (p<0.001) lower in the compensated group
than in the first group. In fact the compensated group consumed 50% lower dry
matter than the first group. When the dry matter intake was plotted in a graph
Fig. 3, the compensated group in the first term of the experiment
consumed more dry matter than the first group, subsequently their dry matter
intake dropped to about 50% of the first group. Feed conversion ratio was significantly
(p<0.001) superior in the compensated group compared with the first group.
In fact the compensated group was 172% superior in feed conversion efficiency
than the normally growing group.
Feedlot performance: compensated female goats had lower weekly and daily
rate of weight gain than the normally growing ones. These could be due to the
reduced feed intake of the compensated group. These results disagreed with those
of Toukourou and Peters (1999) who studied the impact of feed restriction on
the growth performance of goat kids and found no difference in body weight gain
among the restricted and control goat groups. Also Ehoche et al. (1992)
worked with zebu bulls and found that during first and mid period of restriction,
restricted bulls had lower weight gain than the control ones.
||Effect of compensatory growth on feedlot performance
|p = probability, N.S = Not significant.
of compensatory growth on live weight growth
But during the final period of their experiment live weight was significantly
(p<0.05) higher in restricted bulls than in the control ones. Thornton et
al. (1979) studied compensatory growth in sheep and found rapid gains during
compensatory growth which were associated with an increased feed intake.
This discrepancy might be related to type of animals, length of recovery period, severity and duration of restriction period and type of realimination diet.
Feed intake: compensated female goats had significantly (p<0.01) lower feed intake than the basal group. In fact the compensated kids ate 50% lower than the normally fed kids. This result was in line with those of Drew and Reid (1975) who found that there was no increase in daily feed intake after refeeding immature lambs. The results obtained in this study also agreed
with those of Coleman and Evans (1986) who worked on the effect of nutrition,
age and size on compensatory growth in steers.
of compensatory growth on daily weight gain
of compensatory growth on daily dry matter intake
They found that feed intake was reduced in restricted group than in the controls.
Kabbali et al. (1992) also found that daily consumption was not higher
in reefed lambs than in the controls. However, Owen et al. (1971) studied
the effect of food restriction on subsequent voluntary feed intake of pigs and
found that feed intake was increased in restricted group than in the control
group. On the other hand Ehoche et al. (1992) studied the growth performance
and carcass characteristics following feed restriction and realimination in
zebu bulls and found that daily dry matter intake was higher in restricted bulls
than in normally grown ones. Also Rayan et al. (1993a) found that during
realimination, steers that were previously restricted had greater feed intake
than non restricted control animals. These results were at variance with the
present result. Type of animals, diet composition, severity and duration of
restriction might be the reasons.
Feed conversion efficiency: compensated female goats had highly superior feed conversion efficiency than continuously fed kids. The improved feed conversion efficiency in this study might be due to the reduced feed intake. The findings in this study agreed with the results
of Ehoche et al. (1992) who studied the growth performance and carcass
characteristic following feed restriction and realimination in zebu bulls and
found that efficiency of feed utilization was significantly greater in restricted
bulls than in continuously fed bulls. Enhanced growth efficiency during compensatory
growth has been reported in several studies as Turgeon et al. (1986)
who worked in lambs and Abdalla et al. (1988) who worked in calves.