A comparison of in vitro rumen fluid and enzymatic methods to predict digestibility and energy value of grass and alfalfa hay

Nutritional potential, in vitro ruminal fermentation kinetics and methanogenesis of stover from newer cultivars of sorghum (Sorghum bicolor) in buffalo

Context In developing countries of south Asia and Africa, cereal crop residues provide important fodder resources for ruminants. Genetic improvement through plant breeding for high-quality crop residues as well as for grain yield is gaining in demand among mixed crop–livestock farmers. Aims The present study investigated the potential nutritional quality, in vitro ruminal fermentation kinetics, gas production, enzyme activities and methane production of stover of newly developed brown midrib cultivars of sorghum (Sorghum bicolor (L.) Moench) compared with other cultivars in buffalo (Bubalus bubalis). Methods Stover from seven sorghum cultivars – brown midrib sorghum (SPV-2017, SPV-2018), normal grain sorghum (CSV-27), forage sorghum (SSG-59-3, CSV-32F) and sweet sorghum (CSH 22SS, CSV 24SS) – was analysed for chemical composition. Stover samples (200 ± 5 mg dry matter) from each cultivar were incubated with buffered rumen fluid (30 mL) in 100-mL calibrated glass syringes at 39°C for 72 h following a standard in vitro gas-production protocol for gas production and fermentation kinetics. Key results Stover chemical composition varied significantly (P < 0.05) among cultivars, with highest organic matter in forage sorghum SSG-59-3 and lowest in sweet sorghum CSV-24SS. Acid detergent lignin was lowest in stover of the brown midrib cultivars (1.27% in SPV-2018 and 1.67% in SPV-2017) and highest in forage sorghum SSG-59-3 (9.42%). The brown midrib cultivars showed highest (P < 0.001) total gas production, truly degradable dry matter, organic matter digestibility and metabolisable energy content. The brown midrib cultivars and forage sorghum CSV-32F had highest (P < 0.05) production of volatile fatty acids (acetate, propionate and butyrate) and activity of ruminal enzymes (carboxymethyl cellulase and xylanase) during fermentation. Conclusions This study demonstrates that stover from brown midrib sorghum cultivars (SPV-2017 and SPV-2018) and forage sorghum CSV-32F could be preferred over stover of other cultivars for animal feed owing to their potential for enhanced utilisation. Implications This study provides information on nutritional quality of stover from newly developed sorghum cultivars for large-scale utilisation as animal feed in smallholder production systems of developing countries.

The influence of food availability, quality and body size on patch selection of coexisting grazer ungulates in western Serengeti National Park

Context Differences in body size and mouth morphologies influence dietary resource separation among savanna ungulates, and this influences their distribution across landscape. Aim The aim was to understand the influence of body size and mouth morphology differences on both diet and patch selection by ungulate species in western Serengeti. Two hypotheses were tested: (1) for ungulate species, the relative body sizes and muzzle widths (mean muzzle width range: 3.1- 9.85) relate directly to food biomass, and to quality of diets selected in the wet season when food is abundant; (2) in the wet season, if food is not limiting, similar-sized species should exhibit greater dietary niche overlap than ungulate species that differ greatly in body size and muzzle width; moreover, similar-sized species exhibit less dietary niche overlap than ungulate species that differ greatly in body size. Methods In the western Serengeti ecosystem, road transects and direct observation were used to obtain data on the distribution and diet of five ungulate species namely buffalo, zebra, wildebeest, topi and impala; which have of varying sizes (range: 70–630kg) feeding in three different vegetation types. Grassland biomass, structure, nutrient content and ungulate use were measured at sites along transects. Key Results Results indicated that large-bodied ungulates utilised patches of greater food abundance compared with those of smaller ungulates. Body mass was also negatively correlated with diet quality, so that smaller animals ate higher protein and lower-fibre foods, as predicted. Diet niche overlap (niche similarity) showed a strong positive relationship with body mass differences among ungulate species, in support of the second of the two predictions from this hypothesis, namely that dissimilarly sized species could eat the same food. Conclusion Overall, the results suggest that in this savanna system, variation in ungulate body size influences resource separation even in the food-abundant wet season, and that this helps multiple species to co-exist. Implications Implementing more focused conservation strategies will improve wildlife habitat quality by integrating fire as a forage management tool with grazing preferences to promote forage heterogeneity in protected areas.

The effect of increased atmospheric temperature and CO2 concentration during crop growth on the chemical composition and in vitro rumen fermentation characteristics of wheat straw

This experiment was conducted to investigate the effects of increased atmospheric temperature and CO2 concentration during crop growth on the chemical composition and in vitro rumen fermentation characteristics of wheat straw. The field experiment was carried out from November 2012 to June 2013 at Changshu (31°32'93″N, 120°41'88″E) agro-ecological experimental station. A total of three treatments were set. The concentration of CO2 was increased to 500 μmol/mol in the first treatment (CO2 group). The temperature was increased by 2 °C in the second treatment (TEM group) and the concentration of CO2 and temperature were both increased in the third treatment (CO2 + TEM group). The mean temperature and concentration of CO2 in control group were 10.5 °C and 413 μmol/mol. At harvesting, the wheat straws were collected and analyzed for chemical composition and in vitro digestibility. Results showed that dry matter was significantly increased in all three treatments. Ether extracts and neutral detergent fiber were significantly increased in TEM and CO2 + TEM groups. Crude protein was significantly decreased in CO2 + TEM group. In vitro digestibility analysis of wheat straw revealed that gas production was significantly decreased in CO2 and CO2 + TEM groups. Methane production was significantly decreased in TEM and CO2 + TEM groups. Ammonia nitrogen and microbial crude protein were significantly decreased in all three treatments. Total volatile fatty acids were significantly decreased in CO2 and CO2 + TEM groups. In conclusion, the chemical composition of the wheat straw was affected by temperature and CO2 and the in vitro digestibility of wheat straw was reduced, especially in the combined treatment of temperature and CO2.

Nutritional and ecological evaluation of dairy farming systems based on concentrate feeding regimes in semi-arid environments of Jordan

The objective of this study was to evaluate the nutritional and ecological aspects of feeding systems practiced under semi-arid environments in Jordan. Nine dairy farms representing the different dairy farming systems were selected for this study. Feed samples (n = 58), fecal samples (n = 108), and milk samples (n = 78) were collected from the farms and analysed for chemical composition. Feed samples were also analysed for metabolisable energy (ME) contents and in vitro organic matter digestibility according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility. ME and nutrient intakes were calculated based on the farmer's estimate of dry matter intake and the analysed composition of the feed ingredients. ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein, rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). Technology Impact Policy Impact Calculation model complemented with a partial life cycle assessment model was used to estimate greenhouse gas emissions of milk production at farm gate. The model predicts CH4, N2O and CO2 gases emitted either directly or indirectly. Average daily energy corrected milk yield (ECM) was 19 kg and ranged between 11 and 27 kg. The mean of ME intake of all farms was 184 MJ/d with a range between 115 and 225 MJ/d. Intake of RUCP was lower than the standard requirements in six farms ranging between 19 and 137 g/d, was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply = 19 g/d) and ranged between 3 and 30 g/d. Ca intake was significantly below the requirements in small scale farms. Milk nitrogen efficiency N-eff (milk N/intake N) varied between 19% and 28% and was mainly driven by the level of milk yield. Total CO2 equivalent (CO2 equ) emission ranged between 0.90 and 1.88 kg CO2/kg ECM milk, where the enteric and manure CH4 contributed to 52% of the total CO2 equ emissions, followed by the indirect emissions of N2O and the direct emissions of CO2 gases which comprises 17% and 15%, respectively, from total CO2 equ emissions. Emissions per kg of milk were significantly driven by the level of milk production (r (2) = 0.93) and of eDMI (r (2) = 0.88), while the total emissions were not influenced by diet composition. A difference of 16 kg ECM/d in milk yield, 9% in N-eff and of 0.9 kg CO2 equ/kg in ECM milk observed between low and high yielding animals. To improve the nutritional status of the animals, protein requirements have to be met. Furthermore, low price by-products with a low carbon credit should be included in the diets to replace the high proportion of imported concentrate feeds and consequently improve the economic situation of dairy farms and mitigate CO2 equ emissions.

Short Communication: Prediction of in vitro dry matter digestibility with the ANKOM Daisy II system of ruminant feeds using the gas production technique

Plaizier, J. C. and Li, S. 2013. Short Communication: Prediction of in vitro dry matter digestibility with the ANKOM Daisy II system of ruminant feeds using the gas production technique. Can. J. Anim. Sci. 93: 399–402. The potential of the gas production technique to predict in vitro dry matter digestibility was determined using 50 ruminant feeds, including grass/alfalfa forages, grain crop silages, grains, high protein feeds, and feed straws. Without including the chemical composition in the prediction equation, the prediction of IVDMD based on the cumulative gas production during 48 h alone was poor (R 2=0.48). Including the crude protein and neutral detergent fibre concentrations of the feed in the prediction equation improved the accuracy of the prediction (R 2=0.87), which was higher than that of predicting IVDMD based on the chemical composition alone (R 2=0.82).