Effect of sex on feed intake , growth and nutrients digestibility in Blackhead sheep fed complete mash rations of crop residues

Three complete mash rations formulated with crop residues: groundnut shell (GNS), sunflower heads (SFH) and citrus pulp waste (CPW) were tested using 18, 10-month-old Blackhead sheep (9 ram lambs and 9 ewe lambs) of initial body weight 16.9 + 0.59 kg in a 2 x 3 factorial randomized complete design. The three rations contained about 13% CP and the parameters tested were feed intake, growth and nutrients digestibility. Sex had no effect (P>0.05) on feed intake of the sheep in any of the rations offered. Final average body weight among sheep in the three rations were not significantly (P>0.05) different from each other, however, within treatments sex had an effect (P < 0.05) on final average body weight. Ram lambs had higher (P < 0.05) final average body weight than ewes. This was also the case in average daily live weight gains. Among the three rations, rams and ewes on the CPW ration had better (P<0.05) growth rates than those on GNS and SFH. Feed efficiency (kg DMI/kg live weight gain) followed the pattern of growth rate. Nutrients were better (P<0.05) digested by ram lambs than by ewe lambs of the three rations offered. Nutrients digestion was, however, better (P<0.05) in ram and ewe lambs fed the CPW ration.


INTRODUCTION
The integration of small ruminant production with crop residues remains underappreciated and unexplored among small holder farmers in Zambia (Aregheore, 1994a).Crop residues are a key element in tropical ruminant nutrition (deHaan, 1991), and can meet the nutritional requirements of animals if properly processed.The major draw back in the use of crop residues lies in their low feeding value due to their high fibre and low protein content (Sharma and Rajora, 1971;deHaan, 1991;Aregheore and Chimwano, 1992;Aregheore, 1994b).
However, their importance in ruminant nutrition has been stressed in temperate and tropical countries (Rakes, 1969;Cappock et. al.,1974;Reddy andReddy, 1981, 1983; Krishnamohan and Charyule, 1983;deHaan, 1991;Ikhatua et. al. 1991;Aregheore, 1994aAregheore, ,b, 1996)).The use of crop residues in complete rations has been reported (Rakes 1969;Reddy and Reddy, 1981;Kawalker and Patel, 1978;Aregheore, 1992).Using crop residues in compounding complete rations facilitates total feed intake of all portions of the ration offered, rapid growth of animals so they reach market weight earlier than conventional grazing animals, without supplementary feeding.Rakes (1969) reported that the incorporation of crop residues in balanced complete rations provides uniform consumption to meet daily nutrient requirements of ruminant livestock.This minimizes labour, reduces wastage and optimizes the utilization of waste materials (Reddy and Reddy, 1983;Aregheore, 1992;Aregheore et. al., 1996).
The aim of this experiment was to investigate the effect of the sex of Blackhead sheep in the utilization of complete rations based on crop residues in Zambia.

MATERIAL AND METHODS
Groundnut shells (GNS), sunflower head (SFH) and citrus pulp waste (CPM) were obtained from different areas within Lusaka, Zambia.They were sun-dried to a constant weight and then ground through a 6 mm sieve hammer mill (Turner and Metals, Lusaka).They were later moistened to contain 60% DM, maintained at 21°C for at least 10 days and aerated for 24 h before being used in the preparation of rations.Other ingredients used were maize grain, maize bran, urea (46% N), common salt and mineral + vitamin premix.The feedstuffs were compounded into three rations (mash) to represent each of the crop residues (Tables 1 and 2).The rations were isonitrogenous.Eighteen Blackhead sheep (9 rams and 9 ewes) were used.The sheep were about ten months old with an average initial body weight of 16.9 + 0.59 kg, and were divided into three groups according to sex so that there were 3 rams and 3 ewes in each treatment.The experiment was a 2 x 3 factorial randomized complete design.The sheep were housed and fed in groups of three, and for each ration there were two group pens.Thus there was a total of six group-pens.The sheep were fed twice daily at 8.00 and 18.00 h, and were allowed free access to fresh clean water.The rations offered were either increased or decreased depending on intake.Average weight at the beginning and at the end of the trial was used to express growth rate and voluntary dry matter intake.
At the end of the growth phase, the sheep were housed individually for digestibility studies.Faeces voided by each sheep during the day were collected and sampled for 7 days using the total faecal collection method.At the end faeces were dried in a forced draught oven at 70°C for 24 h.The faeces for each sheep were bulked and 25% of the total sample was taken, milled and kept in air tight bottles until chemical analysis.The rations fed were also sampled for approximate chemical analysis.

Analytical methods
Approximate chemical analyses of crop residues, rations (Table 3) and faeces were according to the outlined procedures of AO AC (1980).Gross energy values were determined by the ballistic bomb calorimeter using benzoic acid as the standard.Fibre fractions, NDF, ADF and ADL, hemicellulose and cellulose were analyzed using the procedures of Goering and Van Soest (1970).
Analysis of variance for factorial randomized complete design Steel and Torrie (1980) was used to analyze data.Significant differences between means were compared using Bonferroni t-statistics (Gill, 1978).All data between the sexes within treatments were subjected to the Student t-test.

RESULTS AND DISCUSSION
Data on body weight, dry matter intake and feed efficiency are presented in Table 4.There was no significant difference (P>0.05)among sheep in final average body weight, but within treatments there were significant differences (P<0.05) between rams and ewes.The ewes had lower (P<0.05)growth rates than the rams.Also, the growth rate of rams and ewes was better (P < 0.05) in the CPW than in SFH and GNC, however, within the CPW ration rams also had better growth rates than ewes (P<0.05).Shelton and Carpenter (1972) reported that male animals usually have higher gains than females.With sheep, Abouheif et al. (1992) reported higher growth rate for Najdi ram lambs than ewe lambs of the same age.Also, Aregheore (1994b) reported higher growth rate for rams than ewes of the West African Dwarf goats in Southern Nigeria where course forage was fed in the dry season.Feed intake did not differ between rams and ewes, or treatments (P>0.05).Results of growth rate and dry matter intake indicated that even when DMI is at the same level between ewes and rams, rams still gained better.This, therefore, confirmed earlier reports that male animals grow better than females of the same age even when they are fed the same ration and/or are subjected to the same environmental conditions (Aregheore, 1994b).
Voluntary DMI were within the same level, even though the fibre fractions of the rations differed.The processing (grinding) of the residues before their incorporation with other ingredients to give the final complete feed mash helped the sheep consume every portion of the rations offered.Due to the even distributions of nutrients in the rations, the sheep could not give preference to a particular portion.Sheep generally are selective in nature, preferring nonfibrous feedstuffs (Leng, 1981;Aregheore, 1996), however, the total mixture made it impossible for them to differentiate the fibrous and non-fibrous portions of the rations offered.The preparation improved the utilization of agricultural wastes and also improved DMI of the rations.The results obtained in improved feed intake are in agreement with Leng et al. (1955), Kawalker and Patle (1978), Reddy and Reddy, (1983), Aregheore et al.(l995).These results are a step forward in matching ruminant livestock production with locally available feed resources in Zambia, a land-locked country.Feed efficiency (kg DMI/kg live weight gain) was influenced by growth rate, thus the rams had better (P<0.05)feed efficiency than the ewes.Among the rations, the sheep on the CPW ration had better (P<0.05)feed efficiency than the others, however, there was no difference between GNS and SFH fed sheep.Aregheore (1994b) with goats observed a similar trend in feed efficiency, where the bucks were better than the female goats.
Nutrients digestibility (Table 5) was on average better in the rams than in the ewes in all the rations offered.With the exception of ADF, which was low in GNS, the digestibility of nutrients was high in both rams and ewes.Among the three rations, nutrients digestibility was higher (P<0.05) in the CPW group (rams and ewes), over the other two rations.However, SFH had almost the same level of the digestibility.The similarities between GNS and SFH rations could be due to the fact that they had almost the same level of fibre.The complete feed mash system used helped to improve the digestibility of the rations.The use of urea-N in the rations may also have contributed to the improvement in nutrients digestibility by the sheep (Loosli and McDonald, 1968).
The results of this trial demonstrated that sex has no influence on DMI, however, sex did influence nutrients digestibility and, subsequently, on the growth rate of sheep.Conclusively, the results demonstrated that complete feed mash can be prepared from locally available crop residues to produce cheap livestock feed, and it was also a means of improving the quality of residues for livestock nutrition in Zambia where they do not have enough feed resources to sustain high level of livestock production.

TABLE 4
Weight gain, dry matter intake and feed efficiency of Blackhead sheep fed the three complete mash ration (40 days)

TABLE 5
Effect of sex on apparent nutrients digestibility of complete mash rations by sheep , b, c -means within each treatment for each variable of different superscript differ at P<0.05 1, 2, 3 -means within row with different superscript differ at P<0.05 a