Top Dressing of Fertilizers: A Way Forward for Boosting Productivity and Economic Viability of Grasslands

Grasslands in the Ethiopian highlands have been degrading with grazing loads. Fertilizers like nitrogen, phosphorus and sulfur improves the soil fertility and species composition of the grazing lands. This study justifies, evaluation of top dressing nitrogen and phosphorus fertilizers on biomass yield of grass lands for market-oriented livestock production studied at Chosha kebele, Southern Ethiopia in 2017. Three fertilizer levels ((T1), 150 kg ha−1 urea (T2) and combination of 110 kg ha−1 urea and 100 kg ha−1 NPS (T3)) were laid out in randomized complete block design with 6 replications in summer and winter cropping seasons. Dry matter yield was significantly (P<0.001) different among treatments and higher results were obtained for combination of urea and NPS, followed by urea and the control one. Higher grasses species composition between application of combination of urea and NPS than urea alone. Net revenue is higher in nitrogen alone application than nitrogen and phosphorus. Therefore, better marginal rate of return (MRR=828%) recorded in Urea application for grazing land improvement in Gamo highland areas. It is recommendable to apply 150 kg/ha urea fertilizer to bring optimum yield of grazing land in Southern Ethiopian Highlands

Evaluation of legumes for fermentability and protein fractions using in vitro rumen fermentation

Diversifying feed with non-traditional options could minimize the dependency on traditional sources, maintain the feed supply throughout the year, and potentially reduce the cost of raising animals. A total of eight forage legumes including Peltophorum pterocarpum, Neptunia monosperma, Vachellia sutherlandii (Corkwood), Gliricidia sepium, Bauhinia hookeri and three Desmanthus species (JCU4, JCU5 and JCU9) were collected to assess their in vitro fermentability, degradable and undegradable protein fractions using in vitro gas production method. Soybean meal and lucerne hay were used as control. The total gas production ranged from 12.8 mL/g in P. pterocarpum to 127.3 mL/g in soybean meal. The total volatile fatty acid (VFA) concentration from G. sepium (117.7 mM/L) and V. sutherlandii (111.3 mM/L) were larger than other legumes except for soybean meal (157.1 mM/L) and lucerne hay (130.4 mM/L), P < 0.001. The methane gas produced from B. hookeri and P. pterocarpum (0.39 and 0.32 mL/g) was lower than other feeds, P < 0.001. The V. sutherlandii (720 g/kg crude protein (CP)) and G. sepium (745 g/kg CP) had the greatest effective CP degradation (EPD) than other legume species examined, P < 0.001, which was approaching that measured in the control samples. The amount of protein fraction ‘a’ (rapidly degradable) was larger in JCU9 (551 g/kg CP), and G. sepium (472 g/kg CP), and lower in B. hookeri (10.9 g/kg CP) and P. pterocarpum (14.8 g/kg CP), P < 0.001. The V. sutherlandii (386 g/kg CP) and G. sepium (272 g/kg CP) exceeded other legumes in the proportion of fraction ‘b’ (slowly degradable), P < 0.001, but not the controls. The undegradable fraction increased with increasing phenolic content and reached more than 940 g/kg CP for both B. hookeri and P. pterocarpum. The Desmanthus cultivars showed intermediate values among the tested legumes in fermentation characteristics and shows potential to provide slowly degradable protein while reducing methane. The findings indicate the possibility of using V. sutherlandii and G. sepium to substitute other forages for their greater slowly degradable protein content. Moreover, B. hookeri and P. pterocarpum plants emerged as candidates to assist protein protection in the rumen and reduce methane emissions. However, these legumes need to be evaluated in vivo before promoting for further use to confirm the variability reported here

Optimizing ruminant nutrition through in vitro protein fractionation and protection

© 2024 Bereket Zeleke TunkalaThe quantification of feed digestibility plays a pivotal role in optimising feed resource utilisation and mitigating excessive nutrient excretion into the environment. However, in vivo feed digestibility experiments are encumbered by time, expense, labour intensiveness, and substantial feed quantity requirements. Such methodologies are impractical for the expeditious and routine evaluations demanded by laboratories catering to the needs of livestock producers and feed manufacturers. Therefore, in vitro degradation techniques have emerged as a preferred alternative due to their rapidity, cost efficiency, and precision in predicting digestibility in ruminants, presenting a favourable contrast to the protracted and resource-demanding nature of in vivo approaches. However, in vitro feed fermentation techniques require rumen fluid (RF) to simulate the process of rumen fermentation. Therefore, storing RF while maintaining its microbial activity is a potential approach that would enable the standardisation of in vitro studies by decreasing variation and reducing the need for frequent access to cannulated animals on research farms. The first and second experiments of this project compared RF preservation techniques. In the first experiment, four preservation techniques namely RF stored at -20 degrees Celsius, mixed with 5% DMSO and stored at -20 degrees Celsius (D-20), RF snap-frozen using liquid nitrogen and stored at -80 degrees Celsius (-80), and mixed with 5% DMSO, snap frozen in liquid nitrogen and stored at -80 degrees Celsius (D-80), were compared with fresh RF over five incubation periods (1, 4, 8, 14 and 30 days) using wheat grain and lucerne hay as substrates. The mean cumulative gas production of wheat grain and lucerne hay incubated with fresh RF did not differ from the gas production using RF preserved with D-20. The maximum gas production from fresh RF was also not different from RF preserved with D-20. The concentration of acetic acid, propionic acid, and isobutyric acid did not differ (P < 0.001) between fresh RF and the D-20. The second experiment evaluated the effect of two RF storage methods (-80 and D-20) on dry matter disappearance (DMD) and gas composition of lucerne hay and wheat grain under in vitro fermentation on days 1, 14, 30 and 180 post-collection. There was no difference (P < 0.05) between DMD values between days 14 and 30. The methane composition was greater (P < 0.001) in fresh RF compared to both preserved RFs. The DMD and average cumulative gas production from RF stored at D-20 was higher than -80. Moreover, there was no difference between days 30 and 180 in the lag time and total gas production when fermented using RF preserved at D-20. Overall, RF can be preserved using D-20 for in vitro feed ranking purposes when access to the fresh RF is limited. However, freezing RF negatively affected the in vitro fermentation parameters, yet in different proportions. Therefore, additional RF preservation studies are required to minimise the differences between fresh and preserved RF in terms of in vitro feed degradation, gas production and composition. The information on feed degradation and availability needs to be precise to mix ingredients during feed formulation effectively. Thus, this project evaluated the feed quality, degradation of alternative feeds, effect of feed additives, and protein digestibility using in vitro feed assays. A protein fractionation experiment was conducted to evaluate the possibility of using the ANKOM gas production system and preserved RF to estimate the protein fractions and in vitro degradability of protein-rich feeds. The gas production method, Cornell Net Carbohydrate and Protein System (CNCPS), and the unavailable nitrogen assay of Ross (uNRoss) were used to quantify protein fractions of four feeds (lupin meal, vetch grain, Desmanthus hay, and soybean meal). Based on the results of experiment 1 and 2, the RF preserved at D-20 was also compared against fresh RF in the gas production and uNRoss methods for protein fractions. The protein fractions and fermentation characteristics differed between the in vitro protein quantification methods. However, a strong positive correlation was observed between the protein fractions of the feeds across different methods utilized in this project. Moreover, the ranking of feeds based on their protein fractions were identical across all methods, and the gas production method requires less time, chemicals, and labour than the CNCPS and uNRoss methods. The gas production and uNRoss assay methods behaved similarly in terms of protein fractionation. Therefore, the adaptation of ANKOM gas production apparatus to the gas production technique has the potential to be an alternative protein quantification tool to CNCPS and uNRoss assay, along with the procedural modifications to the ammonia-N sampling. However, RF preservation using D-20 negatively affected the values of ammonia-N and protein fractions. Therefore, testing more options of RF preservation methods is still required to find appropriate RF preservation for in vitro protein quantification. The in vitro fermentability, degradable and undegradable protein fractions of eight forage legumes including Peltophorum pterocarpum, Neptunia monosperma, Vachellia sutherlandii (Corkwood), Gliricidia sepium, Bauhinia hookeri and three Desmanthus species (JCU4, JCU5 and JCU9) were examined using the in vitro gas production method. Soybean meal and lucerne hay were used as control for comparison of the results. After conducting three prior experiments on the effect of preserved rumen fluid (chapters 3, 4 and 5), fresh RF was utilized for all remaining experiments. The total gas production was lowest in P. pterocarpum and largest in soybean meal. The total VFA concentration from G. sepium and V. sutherlandii were larger than other legumes except for soybean meal and lucerne hay. The methane gas percentage of B. hookeri and P. pterocarpum was lower than that of other feeds. The V. sutherlandii and G. sepium had the greatest degradable protein fractions than other legume species examined, which approached that measured in the control samples. The Desmanthus cultivars were intermediate among the tested legumes in total gas production, effective protein degradation (EPD), methane production, total volatile fatty acids (VFA) values, and ammonia-N concentration. The variation between legumes is likely driven by the high variability in the presence of secondary metabolites such as tannins, other polyphenols and overall feed chemical composition. Moreover, the V. sutherlandii and G. sepium showed great potential to be used as a protein source for ruminants, meanwhile B. hookeri and P. pterocarpum could be exploited as natural resources for methane mitigation. Desmanthus can be a viable alternative to improve protein digestibility and reduce methane production. However, these legumes need to be tested in vivo before further use. The fifth experiment evaluated the effect of different tannin extract (TE) inclusion levels (0, 20, 40 and 60 g/kg dry matter (DM)) extracted from Bauhinia hookeri hay on in vitro fermentation characteristics of soybean and canola meals. In the third and fourth experiments (chapters 5 and 6), soybean meal exhibited a higher level of the water-soluble protein fraction, highlighting the necessity for protein protection mechanisms. Consequently, the condensed tannin in Bauhinia hookeri hay (quantified in the fourth experiment) was extracted and tested in vitro to explore its potential to reduce protein degradation in the rumen. The volume of gas production, methane emission, ammonia-N concentration, and immediately degradable protein (fraction ‘a’) decreased with increasing doses of TE from Bauhinia hookeri. At 40 g/kg DM inclusion, TE decreased methane by 40.4%. While 20 g/kg DM TE had no effect on methane, 60 g/kg DM TE negatively affected volatile fatty acid. TE treatment altered protein fractions, reducing protein fraction ‘a’, and increasing slowly degradable protein (fraction ‘b’). The findings highlight the potential of TE from Bauhinia hookeri for methane reduction and protein protection in rumen fermentation, with 40 g/kg DM TE showing consistent benefits. The inclusion rates of different dose of Bioprotect, the starch and protein binding agent, (15 and 30 mL/kg DM) and TE (20 and 40 g/kg DM) from red grape marc were also investigated for their impact on the protein protection and in vitro fermentation characteristics of canola and soybean meals incubated for 24 h using an ANKOM in vitro gas production system. Similar to experiment 5, the addition of Bioprotect and TE from red grape marc to soybean and canola meals inhibited in vitro fermentation characteristics and protein solubility as measured by the gas production, total VFA, ammonia-N, in vitro degradable crude protein (IVDP), fraction ‘a’ and degradation rate of fraction ‘b’. The treated canola and soybean meals produced lower protein fraction ‘a’ and fraction ‘b’ than its untreated counterparts, confirming successful protein protection. However, the effect of 20 g/kg DM TE inclusion from red grape marc in protein fractions ‘a’ and ‘b’ was lowest compared to other additives. Moreover, the increase of Bioprotect from 15 to 30 mL/kg DM and TE of grape marc from 20 to 40 g/kg DM did not affect the gas production in soybean meal. Therefore, 15 mL/kg DM Bioprotect and 40 g/kg DM TE could be promising protein protection doses for in vitro experiments. The most significant factors impacting the efficiency of protein utilisation in ruminants are the amount of rumen undegradable protein (RUP) and the profile of essential amino acids (EAA) entering the small intestine. The last experiment evaluated the effect of two TE (20 and 40 g/kg DM) doses extracted from brown sorghum bran and two Bioprotect (15 and 30 mL/kg DM) inclusion rates compared with tannic acid (30 g/kg DM) on in vitro rumen protein degradation, in vitro intestinal digestibility of RUP (IVIDP) and the amino acid profile of soybean and canola meals. The gas production and ammonia-N concentration from untreated meals were larger than that of treated counterparts. The rumen degradable protein of the untreated canola meal was greater than that of treated meals, and it was not different between meals treated with 30 mL/kg Bioprotect and 40 g/kg TE DM. All additives increased the RUP of both meals, and no difference between the proportion of RUP measured from canola and soybean meals treated with 30 mL/kg Bioprotect, 40 g/kg TE DM and tannic acid. The IVIDP was greater for canola meal treated with 40 g/kg TE DM and 30 mL/kg DM Bioprotect, followed by tannic acid. Treating canola and soybean meals with these additives increased the total EAA concentration quantified after in vitro rumen fermentation and IVIDP procedures, with greater total EAA resulted from the use of 40 g/kg TE and 30 mL/kg Bioprotect DM than other treatments. The additives protected protein and maintained the structural integrity of amino acids from extensive degradation in the rumen. Consequently, increased proportion of RUP and EAA that can reach the intestine for further digestion and absorption. However, in vivo studies are required to validate these findings on ruminants. In conclusion, the D-20 RF preservation is more reliable technique to adopt, but not recommended for methane and protein studies. The ANKOM gas production technology can fit in to the modified gas production method for protein fractionation. Desmanthus plants have a dual benefit as a degradable protein source while reducing methane emissions. The A. Sutherlandii and G. sepium have greater protein potential to be used as a substitute for lucerne hay. The inclusion of 40 g/kg TE from B. Hookeri hay, red grape marc and brown sorghum bran are promising protein protection doses. However, these TE sources need to be tested in vivo before further use

Impact of Rumen Fluid Storage on In Vitro Feed Fermentation Characteristics

Storing rumen fluid (RF) has the potential to standardize subsequent in vitro feed fermentation studies. The first phase of this experiment aimed to evaluate the effect of two RF storage methods on gas composition and dry matter disappearance (DMD) in wheat grain and lucerne hay under in vitro fermentation. The storage methods were as follows: (1) snap-freezing RF using liquid nitrogen and then storing it at −80 °C (−80 °C); and (2) mixing RF with 5% dimethyl sulfoxide (DMSO), subsequently freezing it at −20 °C (D−20 °C), and comparing it to fresh RF on days 1, 14, and 30 post collection. The objective of the second phase was to quantify the impact of preserving the RF for 180 days at D−20 °C on the in vitro fermentation parameters. The methane composition was lower (p p < 0.05) in DMD values between days 14 and 30. The average cumulative gas production and DMD from the RF stored at D−20 °C was higher than that from the RF stored at −80 °C. Moreover, there was no difference between day 30 and day 180 in the total gas production and lag time when fermenting with RF preserved at D−20 °C. Therefore, storing RF at D−20 °C is preferable to storing it at −80 °C when access to fresh RF is limited