绵羊增重

Small Ruminant Research ELSEVIER Small Ruminant Research 18 (1995) 113-120 Effect of supplementing oat hay with lablab, sesbania, tagasaste or wheat middlings on voluntary intake, N utilization and weight gain of Ethiopian Menz sheep N.N. Umunna”,“, P.O. Osuji”, I.V. Nsahlai”, H. Khalilib, M.A. Mohamed-Saleem” alnternational Livestock Centre for Africa (ILCA), PO Box 5689, A&is Ababa, Ethiopia “Agricultural Research Centre (FARC), Institute of Animal Production, Animal Nutrition, 31600 Jokioinen, Finland Accepted 10 October 1994 Abstract This study investigated the effect of feeding oats hay alone or with 250 g of dolichos lablab (Lablabpurpureus, 50% flowering at harvest) hay, wheat middlings, leaves of sesbania (Sesbunia sesbun) or tagasaste (Chamaecyfisuspalmensis) on the growth of 66 Ethiopian Menz sheep and the nutrient metabolism of five sheep from each treatment. One other dietary treatment was oats straw supplemented with lablab. Sheep on the hay-lablab diet, compared with the straw-lablab diet, had higher intake (774 vs. 7 11 g day- I; P < O.Ol), growth rate (28 vs. 18 g day-‘; PO.l); +, (f’0.1;*,P<0.05;**,P<0.01;***,P<0.001;SEDbasedonn=5. “In calculating roughage digestibility the 36 h degradability (g kg-‘) of lablab (645), wheat middlings (827). sesbania (884) and tagasaste (605) were assumed (N.N. Umunna et al., 1995) to equal their digestibilities. bX, xanthine. growth rate, which differed from lablab (P < 0.05) and tagasaste (P < 0.05). 3.3. Intake during metabolism trial Voluntary intake and digestibility values are given in Table 3. There was no effect of source of roughage (P > 0.05) on response to lablab supplementation. Intake of oat hay was higher when given alone than when supplemented with either lablab (PCO.05) or wheat middlings (P < 0.01). Intake of oat hay was similar for lablab and wheat middlings, and also for sesbania and tagasaste, with the former pair having lower (P < 0.05) oat hay intake than the latter. Supplementation and type of supplement (P < 0.001) increased total DM and OM intake. Ses- bania supplementation promoted greater total DM and OM intake than did lablab (P < 0.05) or wheat mid- dlings (P < 0.01) supplementation. Tagasaste supple- mentation promoted higher (PCO.05) intake than wheat middlings supplementation. N.N. Umunna et al. /Small Ruminant Research 18 (1995) 113-120 117 N intake (Table 3) was lowest for unsupplemented oat hay and was different (P < 0.00 1) from the lablab- supplemented oat straw diet. Intake of N was higher (P < 0.001) with the sesbania-supplemented diet than with lablab-, wheat middlings- or tagasaste-supple- mented diets. The last three were not different from each other. 3.4. Digestibility and N utilization Digestibilities (Table 3) of DM (P cO.05) and OM (P < 0.05 ) were higher for lablab-supplemented oat hay than for lablab-supplemented oat straw. Digestibilities of DM and OM were lower for oat hay when given alone than when supplemented with wheat middlings (P < 0.05) or tagasaste (P < 0.05). Effect of supplement type on digestibility was significant (P sesbania = lablab. Digestibility of N (Table 3) was lower for the unsup- plemented oat hay than for any other treatment (P < 0.001) Type of roughage had no effect (P > 0.05) on digestibility of N. Excretion and reten- tion of N are given in Table 3. Faecal N was higher (P < 0.05) for lablab-supplemented oat hay than for lablab-supplemented oat straw. Supplementation of oat hay increased (P < 0.001) faecal N output: ses- bania > tagasaste (P < 0.001) = wheat mid- dlings > lablab (P > 0.05). Urinary N did not differ (P > 0.05) between lablab- supplemented oat hay and lablab-supplemented oat straw. Animals given oat hay alone excreted similar quantities of urine N (P> 0.05) to those given hay supplemented with either lablab or wheat middlings. However, supplementation increased (P < 0.01) uri- nary N output with the following ranking order: lablab < wheat middlings (P > 0.05) < tagasaste (P>O.O5) 0.05) for excretion of uric acid and xanthine plus hypoxanthine. Although the excretion of allantoin and total PD and microbial N supply tended to be highest with the sesbania diet, the differences between supplements were small and non-significant (P>O.O5). 4. Discussion 4.1. Roughage factor The two trials showed inconsistency in the intake of the roughages. Apparent lack of difference between the intake of roughages during the metabolism study can partly be attributed to the lower precision of the trial because numerical differences in intake of oat hay and oat straw were close in the two trials (64 vs. 51 g day- ‘); yet the difference of 64 was significant (P < 0.001) and the difference of 5 1 was not. The lower precision may be a function of low replication (n = 5) during the metabolism trial. Several factors could account for differences in intake of roughages. Oat hay was higher in quality (higher N and lower NDF) than oat straw. This agrees with a report by Mosi and Butterworth ( 1985) and the principle that NDF is the primary factor limiting rough- age intake (van Soest, 1965; Colburn et al., 1968). It has been demonstrated (Umunna et al., 1995) that oat hay has higher solubility, degradability and outflow from the rumen than oat straw. These factors would promote increased microbial protein synthesis in the rumen, but in addition a rapid outflow rate would 118 N.N. Umunna et al. /Small Ruminant Research 18 (199.5) 113-120 enhance the transit of potentially digestible nutrients. Higher faecal N when hay was fed may indicate greater synthesis of microbial protein in the rumen and/or in the caecum. The higher microbial N supply for the hay diet may be due to increased intake of digestible OM (DOM) as well as to increased efficiency of microbial N supply, since the ratios of microbial N sup- ply:digestible OM were 14.29 and 11.55 g per kg DOM for the hay and straw diets, respectively. 4.2. Effect of supplementation In the growth trial, the lower intake of tagasaste relative to sesbania may be due to the reactivity of its tannins, since sesbania had more tannins than tagasaste (Umunna et al., 1995). Low acceptability of tagasaste has been reported in cattle (Varvikko et al., 1992; Var- vikko and Khalili, 1993)) but contradicts other reports indicating that tagasaste is readily accepted by sheep (McGowan et al., 1988; Lambert et al., 1989). Closer examination of daily intake of tagasaste during the growth trial indicated that intake increased progres- sively to a maximum towards the end of the trial. This is consistent with the report by Akin et al. (1988) indicating microbial adaptation to tannins. Inconsis- tency of intake of tagasaste between the growth and metabolism trials can be explained by the fact that the animals used in the latter trial had prior adaptation to tagasaste. Supplementation of oat hay, while increasing total intakes of DM and OM, tended to depress the intake of oat hay, particularly with lablab and tagasaste. This tendency agrees with the findings of Mosi and Butter- worth (1985) and Tolera (1990). Substitution rates were low for wheat middlings (0.11) and sesbania (0.09)) but high for lablab (0.31) and tagasaste (0.28) diets (growth study). Wheat middlings is less bulky than legumes, and this may explain why it had a low substitution rate. However, lower substitutions for ses- bania than for lablab and tagasastediets may be because sesbania degrades relatively fast and promotes faster particulate passage rate through the rumen (Umunna et al., 1995). It was concluded, in accordance with other reports (McMeniman et al., 1988; Reed et al., 199