A review of allodiversity in Lake Naivasha, Kenya: Developing conservation actions to protect East African lakes from the negative impacts of alien species

The biodiversity of developing countries is increasingly threatened by introductions of invasive alien species. This study on the allodiversity in Lake Naivasha, Kenya reviews the pathways, establishment rates and outcomes of introduced species, and provides the basis for determining conservation actions that, if implemented, could prevent potentially harmful effects of similar events in other East African lakes. Introductions into Naivasha commenced in the 1920s with the release of a sport fish and have since produced an allodiversity of 23 species. This includes species that are no longer present (e.g., some tilapia species), presumed no longer present (e.g., the Nile perch Lates niloticus) or whose distribution is highly localised and ecologically neutral (e.g., the coypu Myocastor coypus). It also includes species that established successfully and invoked major changes in lake ecology (e.g., the red swamp crayfish Procambarus clarkii) and a species that is producing apparent economic benefits to the local population (i.e., the common carp Cyprinus carpio). The most frequent donor continents were the Americas and most species were the result of secondary introductions. The main introduction vector was active release that aimed to enhance fishery production. Alien species now dominate each main level of the lake’s food web and produce impacts that are rarely restricted to a single ecosystem service. With a few exceptions, the majority of introductions translate into socioeconomic costs that contribute to rising social conflicts and exacerbating poverty. Development of appropriate conservation management tools within a regulatory framework could help protect Naivasha from further damage and could be used elsewhere in East African lakes to ensure that subsequent introductions enhance ecosystem services without affecting biodiversity.     

Effect of grain sorghum hybrid on in vitro rate of starch disappearance and finishing performance of ruminants.

Forty-eight commercial grain sorghum hybrids were ranked on the basis of in vitro starch disappearance (IVSD) and starch content. Starch content ranged from 64.3 to 70.3% (P less than .01) and IVSD ranged from 5.2 to 6.3%/h (P less than .01). In the next year, 20 experimental grain sorghum hybrids consisting of 17 hybrids being developed for livestock diets and three for human diets were ranked according to IVSD, starch content, and CP content. In these samples, IVSD varied from 6.0 to 9.1%/h (P less than .05). Starch content and CP were not related to IVSD. Starch content was not correlated to CP content. Four of the original 48 grain sorghum hybrids, selected on the basis of IVSD (two fast and two slow), that differed in IVSD by 7.0% (6.5 to 7.0%/h), were fed for 133 d to steers (mean initial BW of 326 kg). The ADG of steers fed Hybrid A (fastest IVSD) was 9.0% faster than that of steers fed Hybrid D (slowest IVSD; 1.33 vs 1.22 kg, P = .06). Gain:feed ratio was positively correlated with IVSD across all treatments (R2 = .94). Hybrids A and D, another Hybrid, A1, and a bird-resistant hybrid (BR) were fed for 85 d to finishing lambs (mean initial BW of 28 kg). Lambs fed Hybrid A gained more efficiently (gain:feed) than those fed BR or A1 (.210 vs .188 and .184, P less than .05), and those fed D were intermediate (.200). Performance of sheep fed A1, with the fastest IVSD, and those fed BR, with the lowest IVSD, were similar, suggesting that factors other than IVSD affected lamb performance. Our data indicate that rate of grain sorghum starch digestion may influence feeding value of grain sorghum fed to cattle.     

Induced non-enzymatic browning of soybean meal. II. Ruminal escape and net portal absorption of soybean protein treated with xylose

Non-enzymatic browning was tested as a means of increasing ruminal escape of soybean meal N. Soybean meal was treated with xylose (3 mol/mol SBM-lysine), sodium hydroxide (pH 8.5) and enough water to achieve an 83% dry matter mixture and then heated at 150 C for 30 min (XTS-30). Trial 1 evaluated ruminal escape of N from XTS-30 compared with commercial soybean meal (CS) or urea (U) in a replicated 3 X 3 Latin square design using six duodenally cannulated Angus X Hereford steers (24.7 kg). Duodenal flow of dietary N was higher (P less than for steers fed XTS-30 (47.9 g/d) than for steers fed CS (39.5 g/d). The ruminal escape estimate for XTS-30 (33.7%) was higher (P less than .10) than CS (13.1%), whereas total tract apparent N digestibility was not different among treatments. In trial 2, net portal absorption of alpha-amino N was measured in Finnsheep X Suffolk ram lambs (24.7 kg) fed U, CS or XTS-30 in a 3 X 3 Latin square design. Portal blood flow was measured by primed, continuous infusion of para-aminohippuric acid. Portal blood flow was lower (P less than .05) for U.fed lambs than for lambs fed CS or XTS-30, and tended to be lower for lambs fed CS than those fed XTS-30. Net portal absorption of alpha-amino N tended to be lowest for lambs fed U (281 mmol/d) and highest for lambs fed XTS-30 (578 mmol/d). The results are interpreted to show that non-enzymatic browning increased flow of soybean meal N to the intestine.     

Induced non-enzymatic browning of soybean meal. III. Digestibility and efficiency of protein utilization by ruminants of soybean meal treated with xylose or glucose

Trials were conducted to evaluate effects of non-enzymatic browning of soybean meal (SBM) on efficiency of protein utilization and N digestibility. In trial 1, 48 Suffolk-Finnsheep lambs (22 kg) were fed 80 d to evaluate efficiency of protein utilization for growth when supplemental protein was fed as urea (U), commercial SBM (CS), or commercial SBM (pH 8.5, 83% dry matter) containing xylose (3 mol/mol SBM-lysine) and heated 30 min (XTS-30) or 55 min (XTS-55). Diets containing graded levels of N from CS, XTS-30 and XTS-55 were fed. Response criterion was efficiency of protein utilization, plotted as gains of lambs fed test proteins minus gain of lambs fed U vs supplemental test protein fed. Efficiencies of protein utilization were .62, 1.27 and .91 for CS, XTS-30 and XTS-55, respectively. Protein from XTS-30 was used more efficiently (P less than .05) than that from CS. In trial 2, apparent digestibility of N from CS (97%) was higher (P less than .01) than XTS-30 (77%) and XTS-55 (82%) by Suffolk-Finnsheep lambs (27 kg). In trial 3, 60 mixed-breed steers (218 kg) were fed individually for 105 d to evaluate glucose as a reducing sugar. Glucose-treated SBM (GTS) was prepared by mixing glucose (3 mol/mol SBM lysine) with SBM, adjusting pH and dry matter content to 8.5 and 80%, respectively, and heating at 150 C for 60 min. Supplemental N sources were U, CS, GTS and a 50:50 mixture (protein basis) of corn gluten meal and blood meal (CGM/BM).(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrolyzed feather meal as a protein source for growing calves

Growth, digestion and in situ studies were conducted to determine the protein value of hydrolyzed feather meal (Fth) for growing ruminants. Dacron bags containing blood meal (BM), Fth, corn gluten meal (CGM) and soybean meal (SBM) were suspended in the rumen of two steers for 12 h to estimate escape protein. The escape protein value for Fth, 69.1%, was less than that for BM (82.8%) and CGM (80.4%; P less than .05) but greater than that for SBM (26.6%; P less than .05). Apparent protein digestion by lambs was similar (P greater than .10) for isonitrogenous diets containing urea (U), BM, Fth, CGM and SBM. Amino acid contents of the protein sources before vs after a 12-h ruminal in situ digestion were similar (P greater than .10). In a growth study, a basal diet of 80% ensiled corncobs and 20% alfalfa was fed to 60 individually fed crossbred steers (215 kg BW). Steers were supplemented with U, BM, Fth, 1/2 BM:1/2 Fth, 1/2 BM:1/2 CGM and 1/3 BM:1/3 Fth:1/3 CGM (protein basis). Protein sources were fed at 30, 45 and 60% of the supplemental N with urea supplying the remainder. Protein efficiency was calculated using the slope ratio technique. Protein efficiency was similar (P greater than .10) for BM- and Fth-supplemented calves. Protein efficiencies were similar (P greater than .10) for BM:CGM, BM:Fth and BM:Fth:CGM combinations. These data indicate the Fth is a digestible high escape protein source that is useful in diets for growing ruminants.     

Influence of dietary forage and energy intake on metabolism and acyl-CoA synthetase activity in bovine ruminal epithelial tissue.

Twenty calves (7 mo old) were blocked by breed, sex, and weight into five groups of four calves and randomly assigned to either a 90% forage (alfalfa) or a 90% grain (50% sorghum and 50% wheat) diet fed at one (1M) or two (2M) times NEm for 140 d. Samples of ruminal epithelial tissue were collected from the anterior ventral sac, and papillae were cut free by hand and used for in vitro incubations and acyl-CoA synthetase assays. Substrates were acetate (90 mM), propionate (60 mM), butyrate (30 mM), and glucose (20 mM). Net productions of beta-hydroxybutyrate and acetoacetate from acetate were greater (P less than .01) with the 2M feeding; however, 14CO2 production from acetate was greater (P less than .05) with the grain diet. Net production of lactate (P = .09) and pyruvate (P less than .01) from propionate increased with the 2M feeding, whereas net lactate production from glucose decreased (P less than .01). Uptakes of VFA were similar with 1M and 2M feeding and were about 10-fold greater than uptakes of glucose. Production of 14CO2 from propionate was two- to fivefold greater than from acetate, butyrate, or glucose. Oxygen consumption was greater (P less than .01) with 2M feeding and unaffected by substrate. Activities of butyryl-CoA synthetase (nmol.mg of tissue-1.h-1) were greater (P less than .05) for animals consuming the forage diets. Addition of butyrate inhibited acetyl- and propionyl-CoA synthetase activity by 63 and 92%, respectively for all dietary treatments. Overall, metabolism of ruminal epithelial tissue tended to increase with the 2M feeding. Influence of dietary forage content on metabolism and activity of acyl-CoA synthetases was minimal, but the high-forage diet caused slight increases.     

Balance and urinary excretion of calcium, magnesium and phosphorus in response to high concentrate feeding and lactate infusion in lambs

Two experiments were conducted to investigate the influence of dietary concentrate level and iv lactate infusion on the urinary excretion and balance of Ca, Mg and P in lambs. In Exp. 1, six ruminal fistulated, crossbred wethers (25 kg) were fed diets of 0, 50 and 70% concentrate for 5-d periods (periods 1, 2 and 3, respectively) followed by 25 d on a 90% concentrate diet (periods 4, 5 and 6, respectively). Collections were made for all days except 6 to 10 and 16 to 20 on the 90% concentrate diet. Dry matter intakes increased with each increase in dietary concentrate until the initial period of 90% concentrate (period 4) when intakes were lowest. Intakes increased (P less than .05) during the latter two periods of 90% concentrate feeding compared with period 4. Rumen fluid pH decreased and rumen L (+) lactate increased with increasing concentrate intake. Blood pH and bicarbonate both decreased with increasing concentrate intake indicating a mild disturbance in acid-base balance. Plasma concentrations of Ca, Mg and P decreased with increased concentrate intake and were elevated (P less than .05) for periods 5 and 6 compared with period 4. Plasma alkaline phosphatase activity and urinary hydroxyproline excretion both increased (P less than .05) for periods 5 and 6. Four of the six animals were in negative Ca balance for the initial period of 90% concentrate feeding, but showed highest Ca retentions for periods 5 and 6. Magnesium and P balance appeared unaffected by increased concentrate intake. Disturbances in Ca metabolism appeared to be short-term and nondetrimental; the animals responded with increased growth and Ca retentions once adjusted to the high concentrate diet. In Exp. 2, four Hampshire ewes (32 kg) were used in a 4 X 4 Latin square design with treatments being saline (.9% NaCl, w/v), L (+) lactate, D (-) lactate and D, L-lactate infused iv in a saline solution to supply .6 mM/kg body weight of each isomer in 15 min. Plasma and urine samples were taken 0, .5, 1, 1.5, 3, 6 and 12 h from the start of infusion. Total urinary excretion of Ca (P less than .04) and Mg (P less than .02) were elevated for all lactate infusions as compared with saline. Total P excretion was greater (P = .06) for all lactate infusions compared with saline and was increased (P less than .05) for the D, L-lactate treatment as compared with the D- and L-lactate treatments.(ABSTRACT TRUNCATED AT 400 WORDS)     

Novel expression of Haemonchus contortus vaccine candidate aminopeptidase H11 using the free-living nematode Caenorhabditis elegans

With the problem of parasitic nematode drug resistance increasing, vaccine development offers an alternative sustainable control approach. For some parasitic nematodes, native extracts enriched for specific proteins are highly protective. However, recombinant forms of these proteins have failed to replicate this protection. This is thought to be due to differences in glycosylation and/or conformation between native and recombinant proteins. We have exploited the free-living nematode Caenorhabditis elegans to examine its suitability as an alternative system for recombinant expression of parasitic nematode vaccine candidates. We focussed on Haemonchus contortus aminopeptidase H11 glycoprotein, which is enriched in a gut membrane fraction capable of inducing significant protection against this important ovine gastrointestinal nematode. We show that H. contortus H11 expressed in C. elegans is enzymatically active and MALDI mass spectrometry identifies similar di- and tri-fucosylated structures to those on native H11, with fucose at the 3- and/or 6-positions of the proximal GlcNAc. Some glycan structural differences were observed, such as lack of LDNF. Serum antibody to native H11 binds to C. elegans recombinant H11 and most of the antibody to rH11 or native H11 is directed to glycan moieties. Despite these similarities, no reduction in worm burden or faecal egg count was observed following immunisation of sheep with C. elegans-expressed recombinant H11 protein. The findings suggest that the di- and tri-fucosylated N-glycans expressed on rH11 do not contribute to the protective effect of H11 and that additional components present in native H11-enriched extract are likely required for enhancing the antibody response necessary for protection.