The impact of underutilised crops as feed and food ingredients

Bone, Gabrielle M (2023) The impact of underutilised crops as feed and food ingredients. PhD thesis, University of Nottingham.

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In the face of population growth and climate change, alternative feed sources are urgently needed to replace traditional sources such as soybean and wheat. The bambara groundnut and mezquite trees are two underutilised crops of current interest but are underutilised due to lack of widespread knowledge on cultivation or potential uses.

The aim of this work was to investigate the impact of bambara groundnut and mezquite pod flour as potential feed and food ingredients by studying their nutritional and antinutritional concentrations and testing mezquite pod flour as a potential feed ingredient for broiler chickens, both raw and following the application of post-harvest processing and exogenous enzymes.

For both bambara groundnut and mezquite pod flour there were significant (p<0.05) differences in crude protein between landraces or species. Protein content was the main focus of this analysis, due to this being the most expensive consideration in animal feed. The crude protein quantity was found to be lower than reported for soybean seeds. For bambara groundnut seeds, the crude protein content ranged from 15.82- 25.85 g/100g, while the mezquite pod flour ranged from 10.78-13.72 g/100g. However, the essential amino acid concentrations within the protein are comparable for bambara groundnut and within the mezquite dry weight, shows a similar profile to soybean. This is important as it indicates a high protein quality.

Both alternative crops had significant variation between the landraces or species in their antinutrient content. For the bambara groundnut seeds the total phenolic content ranged from 5.64-59.62 mg TAE/g and the phytic acid content from 0.210-1.162 g/100g. In the mezquite pod flour the total phenolic content ranged from 5.75-8.96 mg TAE/g and the phytic acid from 0.0260-0.3034 g/100g. The total phenolic content was used as an estimate of the tannin content, which reduced protein digestibility. This was therefore the antinutrient that could be expected to have the greatest impact within the following broiler chicken trials.

A 15% (w/w) inclusion of Prosopis(P.) juliflora pod flour within broiler chicken’s feed, significantly reduced the final body weight (p<0.001) whilst not affecting feed intake, resulting in a significant negative increase in the feed conversion ratio (p<0.001). P. juliflora was chosen as the mezquite species due to previous literature research on this species, alongside availability. However, it also had a total phenolic content that fit in the middle of the range previously studied. Proportional breast muscle weights of birds fed the P. juliflora feed was significantly lower (p<0.001) whist liver weights were not affected. The apparent ileal digestibility coefficients for both crude protein and multiple essential amino acids were also reduced by the P. juliflora inclusion (p<0.05). When two alternative mezquite pod species (P. velutina and P. articulata) were tested, either raw or heat processed along with a phytase inclusion; there was a significant interaction between feed variety and processing for final body weight (p=0.006) and feed conversion ratio (p=0.049). Processing the P. velutina resulted in this feed giving the same characteristics as the control feed, whilst P. articulata containing feeds, either processed or not, was significantly different from the control. In addition, there was a significant effect of feed variant on feed intake (p<0.001) as birds eating any diet containing mezquite had a significantly higher feed intake than control birds. Mezquite pod inclusion significantly reduced the apparent ileal crude protein digestibility coefficients (p<0.001), whilst there was a significant interaction between feed variant and processing (p<0.05) for all essential amino acids exceot phenylalanine. This indicated that processing P. velutina pod flour resulted in this feed giving similar characteristics as the control feed, whilst P. artiulata containing feeds were significantly different from the control, irrespective of whether or not they had been processed.

In conclusion, bambara groundnut seeds show potential as future feed and food ingredients due to their nutritional profiles. Though their use is limited by antinutritional factors, these can be reduced by seed dehulling or potentially by heat treatment. Mezquite pod flour has a variable nutritional and antinutritional profile. Its negative impact on broiler chickens feed digestibility is potentially due to its antinutritional profile. While this may be improved by heat treatment and the application of exogenous phytase; this is dependent on the species of mezquite pod flour used. It should therefore be recommended that the trees local to a community be profiled before use.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Parr, Tim
Brameld, John
Elmes, Matthew
Gonzalez-Carranza, Zinnia
Keywords: crops, animal feed, bambara groundnut flour, mezquite pod flour
Subjects: S Agriculture > SB Plant culture
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 76315
Depositing User: Bone, Gabrielle
Date Deposited: 21 Dec 2023 10:24
Last Modified: 21 Dec 2023 10:24

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