Digestibility Coefficients of Cattle Hoof Meal Diet by African Catfish Clarias gariepinus Juvenile

Digestibility trial of Cattle hoof waste subjected to five processing methods was conducted on Clarias gariepinus juveniles. A reference diet 70 % and test diet 30 % was formulated with chromic oxide biomarker. Feed and feacal samples collected at 8h interval after feeding were analysed for proximate parameters and digestibility coefficient calculated. There was significant difference (P < 0.05) among treatments crude protein digestibility was highest in Reference diet (88.26 ± 0.04) < soda ash diet (87.49 ± 0.04) < fermented diet (82.15 ± 0.10) < wood ash diet (81.26 ± 0.03) < raw hoof diet (79.57 ± 0.05) and lowest in Autoclaved diet (77.69 ± 0.02). Nutrient digestibility also showed significant difference (P < 0.05) among treatments with highest values for soda ash diets parameters and least protein nutrient in autoclaved diet (58.99±0.08 ); fat, dry matter and energy nutrient in raw hoof diet (56.41 ± 3.49; 23.39 ± 0.16; 25.71 ± 0.75). This study concludes that Clarias gariepinus juveniles can be fed soda ash treated cattle hoof waste.


Introduction
Studying the digestibility of new feed ingredient in animal nutrition is in order to make recommendation for optimal inclusion in animal diet. Falaye A. E. (1992) stated that utilization of crop and animal by-product which are inexpensive will reduce cost of nutritive high value feed, increase fish production and farmers profit. Utilization of animal by-product has expanded the aquaculture industry worldwide (Erturk & Sevgili, 2003;Nwanna, 2003). Scarcity and high cost of fish meal had stimulated scientific interest in finding utilization for waste to replace either partially or wholly fish meal in diet of cultured fish (Nwanna, 2003).
Much information exists on the utilization of feather meal in fish diet (Falaye, 1982;Omitoyin, 1995;Falaye et al., 1999;Olaniran & Falaye, 2007). However, Cattle and pig hoof has been used in the nutrition of poultry (Wagner & Elvehjem, 1942;1943;Slinger et al., 1944;Qureishi et al., 1962) while there is dearth of information on the digestibility of this rich protein keratin source in aquaculture nutrition to justify for its inclusion as a dietary protein source. The objective of this study is to assess the digestibility of Cattle hoof meal on Clarias gariepinus juvenile.

Materials and methods
Experimental procedure: The experiment was set up in Aquaculture and Fisheries Management laboratory, University of Ibadan, Ibadan, Oyo State. 720 Clarias gariepinus juveniles were stocked in rectangular plastic tank of 65litre (0.6m X 0.3m X 0.3m) in replicate according to Mubarak et al., (2011) and experimental fish was acclimatized for 7 days.
Feed formulation: Samples of raw cattle hoof waste were processed according to Falaye and Sule (2020). All five processing methods were used to formulate diets for digestibility study. A control basal/reference diet of 40% crude protein was formulated and adjusted according to Hussain et al., (2011) to 70 % reference diet and test diet 30% with chromic oxide biomarker (Table 1). Hoof meal mixed with other feedstuff were ground to fine powder, mixed into dough and pelletized to 2 mm size using motorized pelletizer. The fish in each tank was batch-weighed forth-nightly. Feeding was done twice daily at 3 % fish body weight (Akinwole & Akinnuoye, 2012). The duration of the digestibility trial was 56 days according to Taufek et al., (2016). Fish faeces were collected from each tank daily (8 hours after feeding) from the 7 th day of the experiment. The faeces were strained using 2mm hose on to filter papers, oven-dried at 50 °C for 6 hours and kept for analysis. Proximate analysis: The digestibility feeds samples (n = 6), faecal samples (n = 6) ( Table 3), were subjected to proximate analysis for their nutritional compositions (AOAC, 2000) while chromic oxide analysis of feed and faeces according to Furukawa and Tsukahara (1966).

Apparent and nutrient digestibility co-efficient
Apparent digestibility coefficients (ADC) was calculated according to Fagbenro and Bello-Olusoji (1997

Results
The chemical analysis of components in feed, faeces and chromic oxide is presented in Table 2. There was significant difference (P < 0.05) in faecal sample components analysed. Hoof meal apparent digestibility result showed that the Reference diet was significantly different (P < 0.05) from the Test diets while soda ash hoof sample diet showed significant difference (P < 0.05) from other Test diets (Table 3). The nutrient digestibility of processed Cattle hoof diets (Table 4) showed that soda ash hoof samples was significantly different (P < 0.05) in protein, fat, dry matter and energy when compared to other processed diets.

Discussion
Proximate analysis of Cattle hoof meal digestibility diet revealed significant variations (P < 0.05) among treatments. This is in line with Bureau et al., (1999), Olaniran and Falaye (2007), Hussain et al., (2011) who all reported similar variations in composition of feed due to the crude protein of the test ingredient used in formulation which affected the final crude protein analysis of diet.
The findings of this study on protein digestibility were similar to the report of Richie and Williams (2010) when plant protein sources were fed to Florida pompano. The protein digestibility for the tests diet was in line with Bureau et al., (1999) on feather meal (81 %) usage in (Onchorynchus mykiss) except for the autoclaved hoof diet which showed slight variation. Using feather meal, protein and dry matter digestibility for Diet 4 of Falaye (1982) was similar to the Fermented hoof diet in this study. Falaye et al., (1999) fed composite diet of Cocoa husk and feather meal to O. niloticus and observed digestible protein and dry matter decreased with increased inclusion level of samples in diet. The reason for the variation might have been as a result of processing and diet assimilation by the fish. It was noted that lack of processing impacted on both apparent and nutrient digestibility of raw hoof diets. Omitoyin (1995) and Bureau et al., (1999) reported highest apparent digestibility in control diet for dry matter, protein, lipid and energy which corroborates this research. Similar protein digestibility had been reported by Erturk and Sevigili (2003) for poultry by-product meal (89.3-78.0 %) for Rainbow trout (Onchorynchus mykiss). The values in this study was higher than values reported for Blunt nose black bream (Megalobrama ambylcephala) fed feather meal (-5.7 %); extruded feather meal (76.0 %) and cooked dried feather meal (65.5 %) (Zhou et al., 2008). Significant reduction in lipid digestibility for rainbow trout fed poultry by product and feather meal was reported by Bureau et al., (1999); Erturk and Sevgili (2003), which was in line with this study. Allan et al., (1998) reported that Silver perch showed low protein and energy digestibility when fed poultry and feather meal (15.3 %, 35.1 % vs. 15.5 %, 38.6 %) which contradicts this study. The variability report of digestibility showed the effect of different methods of processing that was used in preparing test ingredient for diet as stated by Morris (1972) and Bureau et al., (1999). Also, NRA (2008) had stated that the equipment used in hydrolysing under high pressure will help achieve up to 80 % digestibility for rendered animal by-products. Utilisation of finely ground cattle horn/hoof soda ash treated sample can aid its digestibility by livestock AFRIS/Feedipedia (2017).

Conclusions
Soda ash treated samples diet of cattle hoof was well digested by C. gariepinus juveniles over other processed sam-ple diets. Hence utilization of soda ash treated hoof meal in juvenile catfish diet hereby suggested.