A. Nefzaoui

DEACTIVATION OF CONDENSED TANNINS IN ACACIA CYANOPHYLLA LINDL. FOLIAGE BY POLYETHYLENE GLYCOL IN FEED BLOCKS EFFECT ON FEED INTAKE, DIET DIGESTIBILITY, NITROGEN BALANCE, MICROBIAL SYNTHESIS AND GROWTH BY SHEEP

Abstract Unmolassed feed blocks were used as supplement of Acacia cyanophylla Lindl. (acacia)-based diets. They were made, on the basis of crude weight, with olive cake (42.2%), wheat bran (26.7%), wheat flour (10.7%), quicklime (10.7%), urea (4.4%), salt (4.4%) and a mineral and vitamin supplement (0.9%). Polyethylene glycol (PEG, mol. wt. 4000) was introduced in these feed blocks at five increasing levels (0 (control), 6, 12, 18 and 24% on the basis of ingredient mixture before moulding) to deactivate acacia condensed tannins. The five dietary treatments (levels of PEG) were evaluated simultaneously and each diet was tested on 6 yearling male Barbarine sheep (average initial weight 19±1.5 kg) and five Barbarine rams (average initial weight 47±3.0 kg). Animals were held in individual pens and metabolism cages, respectively. They were adapted to experimental conditions for 10 and 21 days, respectively before the commencement of the measurement periods. Freshly cut foliage of acacia was distributed ad libitum and the feed block was permanently available in the trough. Feed intake and daily gain were measured on yearlings during a 60-day period. Feed intake, in vivo diet digestibilities, nitrogen balance and microbial nitrogen synthesis using urinary excretion of allantoin were measured on rams during 10 consecutive days. Dry matter intake (DMI) of feed blocks ranged from 13.7 and 16.5 g/kg W 0.75 for yearling sheep and from 15.5 and 24.3 g/kg W 0.75 for rams. PEG had no effect on feed block intake. Acacia DMI by sheep given feed blocks without PEG was low (37.7 and 39.9 g/kg W 0.75 , respectively for yearlings and rams). Supplementation with feed blocks containing either 6, 12, 18 or 24% of PEG increased acacia DMI by 25, 50, 56 and 45%, respectively for yearling sheep and 22, 25, 56 and 71%, respectively for rams. Providing PEG in feed blocks at a rate of 6, 12, 18 or 24% increased digestible organic matter intake (DOMi) by 3.4, 4.3, 9.4 and 18.2 g/kg W 0.75 and digestible crude protein intake by 17, 12, 23 and 36 g/day, respectively. The higher the rate of PEG introduced in feed blocks the greater N retention and urinary excretion of allantoin. Estimated microbial N (g/kg DOMi) was increased by 37, 94, 135 and 153% with feed blocks containing 6, 12, 18 and 24% of PEG, respectively. The clear-cut improvement of the nutritive value of acacia-based diets following PEG supply resulted in a linear increase of the growth rate of sheep. The optimum responses of acacia intake, nitrogen retention, microbial N yield and daily gain were obtained in sheep given feed blocks with 18% of PEG which corresponded to a PEG consumption of about 23 g/day. It was concluded that feed blocks may be used as carrier of PEG for improving the nutritive value of tannin-rich diets.

Feed blocks as alternative supplements for sheep and goats

This paper discusses the potential use of feed blocks as alternative supplements for stall-fed and grazing small ruminants raised under harsh environments. A background on manufacturing process of these blocks and the impact of their use in livestock feeding are reported. Trends converge to indicate that hard blocks, a mixture of agro-industrial by-products, urea, binder and preserver, improve digestion of low quality forages thereby increase body weight. Therefore, feed blocks may be considered as an alternative to promote intensive use of numerous agro-industrial by-products and to overcome nutritional constraints. A positive effect of block enriched or not with microelements and vitamins on reproductive performance of ewes was demonstrated. Another potential role of feed blocks is their use as efficient carrier of tannin-neutralising reagents (e.g. polyethylene glycol) to valorise tanniniferous shrubs and trees. Worth noting that these blocks may be used also to vehicle some anthelmintic medicines for small ruminants to control gastrointestinal nematodes. Feed blocks may reduce the use of concentrate feeds, thus reduce feeding cost and increase farmer’s income. In addition to their nutritional and economical benefit, the success of feed block technology depends on its adoption by smallholders. Therefore, the active participation of farmers in the evaluation and transfer of feed block technology targeting their specific conditions is highly recommended.

Palatability of shrubs and fodder trees measured on sheep and dromedaries: 1. Methodological approach

Experiments were performed to study the effect of measurement duration on the palatability of 11 range species and to define a palatability index. The range species were randomly distributed in five combinations (C1–C5) each containing four species. Each combination was tested over a 15 day experimental period on four 1-year-old sheep and five 2-year-old dromedaries (Camelus dromedarius). Animals received the four range species ad libitum daily at 08:00 h and were supplemented at 17:00 h with spineless cactus. Barley hay (standard food) was offered with the range species only during the first 5 days of each experimental period. Food intakes measured on the first day (I1), average food intakes in the first 5-day period (I5), the second 5-day period (I10) and the third 5-day period (I15) were compared. Significant correlations were found between I1 and I5 (r = 0.93, P < 0.01), I5 and I10 (r = 0.75, 0.01) or I15 (r = 0.61, P < 0.05), and I10 and I15 (r = 0.87, P < 0.001) for sheep. These correlations were higher for dromedaries, and intakes may be predicted by the following regression equations: I5 = 1.09I1 + 0.07 (r = 0.96, P < 0.001); I10 = 1.15I1 + 0.25 (r = 0.85, P < 0.01); I15 = 1.42I1 + 0.32 (r = 0.78, P < 0.01). As the range species were not offered in the same amounts, intakes were expressed as a percentage of the relative quantities offered daily (I1D1, I5D5, I10D10 and I15D15). The same trend as reported above was observed between I1D1 and I5D5, I1D1 and I10D10, and I1D1 and I15D15. Such results suggested that for dromedaries 1 day of measurement may be sufficient for palatability assessment while for sheep this period should be extended to 5 days for better accuracy of intake prediction. As all the range species were not offered at one time, I1D1 and I5D5 ratios were expressed in relation to hay intake (HI)hay distributed (HD) ratio. Two indices were then calculated: R1 = (I1/D1)/(/HI1/HD1) and R2 = (I5/D5)/(HI5/HD5). R1 and R2 were found to be highly correlated for sheep (r = 0.94) and dromedaries (r = 0.92). Therefore, R1 was chosen as a palatability index. The range species were ranked using this index and animal preferences were established.

Polyethylene glycol in concentrate or feedblocks to deactivate condensed tannins in Acacia cyanophylla Lindl. foliage 1. Effects on intake, digestion and growth by Barbarine lambs

Thirty young male sheep were given air-dried foliage of Acacia cyanophylla Lindl. ad libitum and 400 g oat hay. Animals were divided into five equal groups each of which was supplemented with either 300 g concentrate with (C PEG ) or without (C) 20 g polyethylene glycol 4000 (PEG) or urea-containing feedblocks with (BU PEG ) or without (BU) PEG. One other treatment was PEG-containing feedblock without urea (B PEG ). PEG was used to preferentially bind A. cyanophylla condensed tannins (CT). Feedblocks (BU, B PEG and BU PEG respectively) were made from olive cake (395, 376 and 353), wheat bran (263, 250 and 235), wheatfeeds (132, 125 and 118), quicklime (88, 83 and 78), salt (44, 42 and 39), mineral and vitamin supplement (12, 10 and 10), urea (66, 0 and 59) and PEG (0, 114 and 107 g/kg). These diets were used in growth (60 days) and metabolism (7 days) studies. Ureacontaining feedblocks, as compared with concentrate, were higher in crude protein (CP; 235 v. 116 g/kg DM) and lower in metabolizable energy (6 v. 10 MJ/kg DM). The type of supplement (i.e. concentrate v. feedblocks) had no effect ( P > 0·05) on A. cyanophylla DM intake, CP and neutral-detergent fibre (NDF) digestibilities and nitrogen (N) retention. However, concentrate-containing diets exhibited higher DM and organic matter (OM) digestibilities ( P < 0·05), urinary excretion of allantoin ( P < 0·05), microbial N supply ( P < 0·001) and average daily gain ( P < 0·001). PEG supply increased DM intake of A. cyanophylla , CP digestibility, N retention, allantoin voided in urine, microbial N supply and lamb growth. PEG-containing feedblocks enriched (BU PEG ) or not (B PEG ) with urea had similar effect on A. cyanophylla intake, DM, OM and NDF digestibilities, allantoin in urine, microbial N supply and average daily gain. These findings suggested that urea inclusion in feedblocks are not necessary and thus the feeding cost may be reduced. The higher amount of microbial N and daily gain in lambs given concentrate as compared with those on feedblock-supplemented diets was ascribed to the level of energy which was low in the latter diets. Enrichment of feedblocks with energy-rich ingredients such as molasses or cactus fruits could be a solution. This work confirmed that tannins depressed the nutritive value of this shrub species and lamb growth. However, the reduction was not drastic in the absence of PEG in the diet. Feedblock diet (BU) matched maintenance requirements of lambs while lambs on concentrate-supplemented diet (C) grew at a rate of 78 g/day. The choice between these two supplements will depend upon farm conditions and objectives.

Polyethylene glycol in concentrate or feedblocks to deactivate condensed tannins in Acacia cyanophylla Lindl. foliage 2. Effects on meat quality of Barbarine lambs

Twenty-five male Barbarine lambs aged approximately 150 days were divided into five groups. All the animals received 400 g/day of oat hay and Acacia cyanophylla Lindl. foliage ad libitum . Two groups also received 300 g/ day of a mixture (70 : 30) of processed barley and wheat bran, with or without 20 g polyethylene glycol 4000 (PEG), groups C PEG and C respectively. The three other groups had free access to feedblocks based on olive cake, and containing urea, urea and PEG, or PEG, groups BU, BU PEG and B PEG respectively. Lambs were slaughtered at age 230 days and meat quality was determined in the longissimus thoracis et lumborum muscle. Lean colour was significantly affected by dietary condensed tannins. Lightness (L*) was higher in those animals that did not receive PEG ( P < 0·001) indicating that condensed tannins can cause lighter meat colour. This difference was not due to the ultimate pH, which was not affected by the inclusion of PEG in the diet. Meat from groups that received supplementation of concentrate had lower values of resistance to the Warner-Bratzler shear device compared with those that received feedblocks. This result was confirmed by a taste panel, that found samples from groups C and C PEG more tender than samples from groups BU, BU PEG and B PEG . Inclusion of PEG in the diet increased intensity of flavour ( P < 0·05) but had no effect on overall acceptability. Meat from animals that had received the concentrate had higher overall acceptability ( P < 0·05) than meat from animals that received the feedblocks. No differences were found in meat chemical composition.

Upgrading of sorghum stover with anhydrous ammonia or urea treatments

Abstract The effects of anhydrous ammonia and urea treatments of sorghum stover on intake, in vivo digestibility, in situ dry matter degradation and nitrogen balance on sheep were compared. Untreated, ammonia-treated (3% dry matter (DM) basis) and urea-treated (5.3% and 25% water, DM basis) stovers were fed ad libitum to four sheep, supplemented with 300 g of barley and 30 g of a mineral/vitamin mix for 25 days. Both treatments resulted in a smaller decrease in the fibre content of stover, but total nitrogen contents were markedly increased with urea (18.9% of DM) and ammonia (17.0% of DM) treatments compared with untreated stover (9.3% of DM). The free ammonia nitrogen and the fibre-bound nitrogen (N-NDF) contents were increased by the ammonia (+2.4 g kg−1 and +0.6 g kg−1 DM, respectively) and the urea (+4.4 g kg−1 and +0.4 g kg−1 DM) treatments. Ammonia treatment resulted in an increase in the DM intake from 31.4 g DM kg−1 W0.75 for untreated stover to 47.2 g DM kg−1 W0.75; urea treatment increased DM intake to 46.8 g DM kg−1 W0.75. Organic matter, fibre and crude protein digestibilities were increased when stover was treated. The highest crude protein digestibility and nitrogen retention values were obtained with the urea treatment (66.6% and 6.2 g day−1 respectively), while the highest fibre digestibility (NDF) value was recorded with the ammonia treatment (65.1%). Rumen cellulolytic activity measured as in situ dry matter degradation showed the same pattern of variation as in in vivo fibre digestibility. Ammonia and urea treatments increased the potentially degradable fraction from 61.4% for untreated stover to 80.1% and 68.4% respectively. The rate of degradation also increased from 2.88% h−1 for untreated stover to 2.92% h−1 and 3.67% h−1, respectively, with ammonia and urea treatments. Both anhydrous ammonia and urea treatments increased the intake and digestion of sorghum stover by sheep. Urea is as effective as anhydrous ammonia in improving the nutritive value of sorghum stover.

Energy or nitrogen supply to sheep fed Acacia cyanophylla Lindl. leaves-based diets : effects on intake and digestion

In this paper, we report preliminary results of a study dealing with the effect of energy (spineless cactus) or nitrogen (urea) supply on intake and digestion by sheep fed acacia-based diets. Four diets were tested according to a 4x4 Latin square design on rumen fistulated sheep (initial liveweight 47 kg). All diets included airdried acacia leaves ad libitum, 176 g DM barley, 30 g mineral and vitamin supplement (control, D1) and supplemented with 15 g urea (D2), or 300 g DM cactus (D3), or 15 g urea and 300 g DM cactus (D4). Each experimental period lasted 25 days (15 days for adaptation and 10 days for measurements). Diet digestibility was measured by total faecal collection technique. Rumen fluid was sampled before morning meal and thereafter at 2, 4 and 8 h and analysed for pH, ammonia nitrogen (N-NH 3), and volatile fatty acids (VFA). Acacia degradability in the rumen was measured by the nylon bag technique (0rskov et al, 1980, Trop Anim Prod, 5, 195213). Two grams samples of acacia (dried at 50°C and ground to pass through 3 mm screen) were introduced in nylon bags (6.5 cm x 9 cm, pore size 50 Nm). DM and nitrogen disappearance rates of incubated acacia were fitted against incubation times (4, 8, 16, 24, 48, 72 and 96 h) by the model of Orskov and McDonald (1979, J Agric Sci, 92, 499-503). Voluntary intake of acacia is low for all diets. It was not affected by urea supply (D2) but tended to decrease with cactus supply (D3). Highest intake of acacia was recorded with D4. Diet

Prediction of the nutritive value of shrubs and fodder trees by laboratory techniques

In Tunisia, livestock feeding in arid and semiarid regions is based on range lands. Management of range species requires knowledge of their palatability and nutritive value. Use of conventional digestion trials with animals to measure intake and digestibility of range species is a complicated, costly and time-consuming operation. Some laboratory techniques (chemical constituents (OM, CF, CP, NDF, ADF, ADL), condensed tannins, Absorbance at 280 nm (A280)), (Nefzaoui, 1985, These Doctorat, Univ Catholique Louvain, 354 p), in vitro organic matter digestibility (IVOMD) (Tilley and Terry, 1963, J Brit Grassl Soc, 18, 104-111 ), in sacco dry matter degradability (0rskov et al, 1980, Trop Anim Prod, 5, 195-213) and gas production (Gas), (Menke et al, 1979, J Agric Sci, 92, 499-503) were assayed in our laboratory to predict dry matter (DM) intake and organic matter digestibility (OMD) of 10 fodder shrubs and trees harvested at different