Modelling of digesta passage rates in grazing and browsing domestic and wild ruminant herbivores

Ruminant utilization of poor-quality feeds is governed by rates of digestion and of passage through the rumen. The passage rate of feed material determines the quantity of bypass nutrients and the efficiency of synthesis of microbial protein in the rumen, making modelling of passage rate important. Artificial neural networks were used to develop models of liquid and solid passage rates. Studies that reported fractional passage rates, along with class and body mass of ruminants, were included in the dataset. Factors that affect rates of passage in all the studies were identified, which included animal and feed factors. The dataset was composed of observations of domestic and wild ruminants of variable body mass (1.5 to 1238 kg) from 74 studies and 17 ruminant species from various climatic regions. Observations were randomly divided into two data subsets: 75% for training and 25% for validation. Developed models accounted for 66 and 82% of the variation in prediction of passage rates for solid and liquid, respectively. On validation with an independent dataset, these models attained 42 and 64% of precision in predicting passage rates for solid and liquid, respectively. Liquid and solid prediction passage rate models had no linear and mean bias in prediction. This study developed better prediction models for solid and liquid passage rates for ruminants fed on a variety of diets and/or feeds from different climatic regions.Keywords: Artificial neural networks, intake, mean retention time, prediction equation, rume

Supplement 1) Peer-reviewed paper

Abstract The effect of different inoculum sources, obtained from the faeces of ungulates, i.e. horses (H), wildebeest (WB) and zebra (ZB) and combinations of inoculum sources on the fermentation of maize stover (MS) was investigated. Combined sources (CS) were: (1) H+WB, (2) H+ZB, (3) WB+ZB and (4) H+WB+ZB. Fresh faecal inocula were cultured in the laboratory on MS and lucerne (mixed in 1 : 1 ratio) with salivary buffer for 72 h at 38 °C prior to application as an inoculum or extraction of crude protein (CPZ) for enzyme assays. Crude protein was precipitated using 60% ammonium sulphate and analyzed for exocellulase, endocellulase and hemicellulase specific activities (µg reducing sugar/mg CPZ). An in vitro fermentation study was done by transferring 33 mL of laboratory cultured faecal inoculum into 67 mL of salivary buffer containing 1 g MS and incubating for 72 h at 38 °C. Exocellulase specific activities differed among the seven inoculum sources. Exocellulase activity ranked the different microbial sources according to their fibrolytic potential as follows: 1 > 2 > 4 > H > ZB > WB >3. Total gas, true degradability (TD), microbial yield and total short chain fatty acids (SCFA) were higher in the CS than in the individual systems. Systems 1 and 3 had the highest TD (714mg/g CPZ) and total SCFA (680 mg/g CPZ), respectively. True degradability, total gas, total SCFA, partitioning factor and degradability efficiency ranked the microbial ecosystems according to their fibrolytic potential as follows: 3 > 1 > 4 > WB > 2 > ZB >H. Inoculum sources differed in fibrolytic digestion, with microbes from CS (1) and (4) proving to be the best. Further investigation is essential towards using inoculums sources as possible feed additives in ruminants

On the suitability of Illius and Gordon\'s model for simulating the intake and digestibility of roughage diets by ruminants

predicting the digestibility and intake of tropical roughages by ruminants. Data from seven suitable empirical studies (i.e. studies that reported all requisite data needed to run the model) in which tropical roughages were fed to ruminants were used. These seven studies had 235 intake and 70 digestibility measurements on goats, sheep and cattle. The coefficient of variation (cv) of the observed digestibility was 13.8%. A linear least square regression relationship between the observed (Y) and predicted (X) digestibility accounted for barely 37% of the variation for the entire data set [Y = 0.24(s.e. = 0.056) + 0.61(SE = 0.100) X] and for 53% of the variation when 5% of the observations were treated as outliers: [Y = 0.17 (SE = 0.047) + 0.72 (SE = 0.084) X]. For both equations the intercept and the slope were different from zero and unity, respectively. Although, a plot of residual digestibility showed no distinct pattern, this model should be used with extreme caution because of its inherent noise. The observed intake had a higher cv of 18.3%. Regression relationships between the observed and predicted intakes accounted for barely 15% of the variation for the entire data set: [Y = 30.1(SE = 7.39) + 0.71(SE = 0.111) X] and for 20% of the variation when 5% of the extreme values were treated as outliers: [Y = 28.7(SE = 6.73) + 0.75(SE = 0.101) X]. A residual plot showed that the model systematically underestimated the intake of roughages which elicited high intakes. The discussion was structured to identify, justify and propose pathways for enhancing the model. Keywords: Ruminant, roughage intake, digestibility, modelSouth African Journal of Animal Science Vol. 37 (4) 2007: pp. 275-28

Nutritive value of Adenodolichos rhomboideus leaves compared with Leucaena leucocephala and Stylosanthes guianensis forages in indigenous goats in Lubumbashi (DR Congo)

Three forages (Adenodolichos rhomboideus,Leucaena leucocephala, and Stylosanthes guianensis) were evaluated for their chemical composition, and for both voluntary intake and apparent in vivo digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), and acid detergent fibre (ADF) as estimated by six goats (17.1 kg ± 0.7) used in a 3 × 3 double Latin square design. Forage from S. guianensis had a lower (p < 0.001) CP content than L. leucocephala forage and A. rhomboideus leaves. Fibre content (ADF and NDF) was lower (p < 0.001) in L. leucocephala (35%) forage than in A. rhomboideus (59.5%) and S. guianensis forages (56.5%). Leucaena leucocephala forage presented higher CP, ash, and ether extract levels, and higher digestibility and voluntary intake of CP. Adenodolichos rhomboideus leaves had lower (p < 0.05) apparent digestibility and intake of DM. Digestible CP content was similar for A. rhomboideus leaves and S. guianensis forage. Leucaena leucocephala appears to be the most adequate forage for goat production. Low digestibility and voluntary intake of A. rhomboideus leaves may be due to negative effect of an anti-nutritional factor such as tannin

The effects of storage condition and preservatives on maize-based diets for broiler chickens

A study was conducted to assess the effects of varying storage temperature and relative humidity (RH) conditions, and feed preservatives (a mixture of Mold-Zap (a fungal inhibitor) and Banox E (an antioxidant)) on performance, visceral organ weight, serum biochemistry and haematology of broiler chickens. Birds fed diets stored at low RH (50%) were heavier and had a better feed conversion efficiency (FCE) than those on diets stored at high RH (80%). Diet storage temperature had no significant effort on body weight of birds but FCE was improved when birds were maintained on diets stored at a low temperature (15°C). Feed intake was unaffected by the main factors but the interactive effect of temperature x preservative influenced intake. Liver weight was lowest in birds that consumed feeds stored at a low temperature and low RH. The presence of a detoxifier (MTB 100) in the diet reduced the heart weight of birds by 11%. Diets stored at the low temperature or RH significantly decreased the weight of the gizzard in birds. Inclusion of the preservative in the diets also reduced gizzard weight by 4%. Similarly, gizzard weight was reduced by about 6% due to the presence of the detoxifier in the diets stored at low temperature. Inclusion of the detoxifier in the diet reduced spleen weight and the inorganic phosphorus concentration in serum. Further studies are required to test a wider range of storage conditions as well as the potential of some of the additives used in the present trial

The nutritive value of forage sorghum genotypes developed for the dry tropical highlands of Kenya as feed source for ruminants

in vitro studies were conducted on five sorghum genotypes developed for the dry tropical highland climate of Kenya and which can be fed to ruminants fresh or as silage. The five sorghum genotypes consisted of two normal white mid-rib (WMR) genotypes, coded E1291 and E65181, and three brown-midrib (BMR) genotypes, coded Lan-5, Lan-6 and Lan-12. Whole mature plants (herbage plus grain) and silage made from E 1291 were used in the study. An in vitro manual gas production technique was used to compare the nutritive characteristics of these genotypes for ruminants. These sorghums differed significantly in true organic matter degraded (OMDeg), which ranged from 520 to 678 g/kg after 24 h incubation and 706 to 805 g/kg after 72 h incubation. All the BMR sorghums had a higher degradability than the WMR genotype, E6518, and the silage, with Lan-5 having the highest degradability. Methane produced per g OMDeg ranged from 40.6 to 46.4 mL/g after 24 h incubation and from 53.1 to 62.6 mL/g after 72 h incubation. It was similar for all genotypes after 24 h incubation but Lan-12 had the highest methane production after 72 h incubation. After 24 h and 72 h incubation all the genotypes produced a similar total amount of gas per OMDeg (293 to 309 and 357 to 385 mL/g, respectively) with similar total short chain fatty acid concentrations in the liquid digesta (7.8 to 10.4 and 9.5 to 10.3 mmol, respectively) and acetate to propionate ratios of 2.16 to 2.49 and 2.35 to 2.87, respectively. The sorghums showed great potential as ruminant feed sources in the region