The evaluation of locally produced full-fat canola seed (Brassica napus) as an alternative protein source in the diets of slaughter ostriches (Struthio camelus var. domesticus)

[摘要] ENGLISH ABSTRACT: Ostriches are multi-purpose animals, producing feathers, leather and meat that contribute to the income generated from slaughter ostrich production. Compared to other domesticated farm animals, knowledge of the nutritional requirements of ostriches has been very limited, until recently. Together with simulation models this knowledge gained is being used to formulate least cost, nutrient specific rations for ostriches in different production phases. In an effort to reduce feeding costs, which make up the largest expense (ca. 75%) in an intensive ostrich production unit, the use of alternative protein sources are being explored to replace the more expensive protein sources that make up a large portion of the diet. Full-fat canola seed (FFCS) is one such locally produced protein source that has the potential to replace current protein sources such as soybean oilcake meal. However, it is unclear whether ostriches will readily consume canola, due to its anti-nutritional factors, and what effect its consumption may have on animal performance.The feeding preference (Chapter 3) of ostriches towards canola was established by placing 60 South African Black ostriches (82.2 ± 1.06 kg in live weight, 233 days of age) in ten camps of six birds per camp. Each camp had five identical feed troughs, each containing diets, where FFCS incrementally (0, 25, 50%, 75 and 100% of protein source) replaced the soybean oilcake meal (9.8% of the total diet composition in control diet) as protein source. Feed and water were made available ad libitum. Dry matter intake (DMI) was measured on a daily basis and feed colour characteristics were measured based on CIE L*, a* and b* colour attributes. Only the 25%FFCS (25% soybean oilcake meal replacement diet) showed a higher DMI (817.4 ± 81.98 g/bird/day) than the other diets (average of 488.8 ± 81.98 g/bird/day). While there were slight differences between some of the colour attributes, it is believed to have had no effect on DMI. Based on the results of this study, FFCS can be used to replace 25% soybean oilcake meal without any negative effect on DMI; resulting in an inclusion level of 6.8% FFCS in ostrich diets.To evaluate to what extent FFCS can be utilised in the diets of slaughter ostriches, 187 day old South African Black ostrich chicks were randomly divided into 15 groups (9 - 12 animals per group). The growth trial (Chapter 4)commenced at the onset of the starter phase when the chicks were 84 days of age weighing 24.7 ± 0.36kg. Five iso-nutritional treatment diets with varying levels of FFCS were randomly allocated to the groups with three replications per treatment diet. Birds were reared according to standard practises and slaughtered at 309 days of age (93.2 ± 1.82 kg). Within each feeding phase, FFCS incrementally (0%, 25%, 50%, 75% and 100% of protein source) replaced the soybean oilcake meal as protein source. Feed and water were supplied ad libitum. Dry matter intake, average daily gain (ADG), feed conversion ratio (FCR) and end weights were recorded with in each phase and over the entire trial period, as well as slaughter traits. No differences were observed regarding production traits during the starter and finisher phases. Dry matter intake during the grower phase was lowest (P =0.01) for the 100% replacement of soybean oilcake meal (100%FFCS) (1.52 kg/bird/day). The rest of the diets with an average DMI of 1.80 kg /bird/day did not differ. The 100%FFCS also showed the slowest growth (P =0.01) (152.0 g/bird/day) during the grower phase, and did not differ from 25%FFCS (208.9 g/bird/day) and 75%FFCS (209.5 g/bird/day) diets. With the 0%FFCS (236.2 g/bird/day) and 50%FFCS (267.8 g/bird/day) diets resulting in higher ADG. End weights during the grower phase for the 0%FFCS, 25%FFCS, 50%FFCS and 75%FFCS (74.8, 72.2, 76.8 and 72.5 kg respectively) did not differ from each other. The 100%FFCS resulted in lower end weights (67.4 kg), although not differing from the 25%FFCS and 75%FFCS. For the overall trial period the only differences observed, were within ADG, with the 0%FFCS, 50%FFCS and 75%FFCS replacement diets showing the fastest growth and the 100%FFCS, although not differing from the 25%FFCS and 75%FFCS diets, resulted in the slowest growth. Fat pad weight was the only slaughter trait that revealed differences between diets, with the 50%FFCS resulting in the heaviest fat pad weights. Based on these results, it is recommended that a maximum of 20.6% inclusion (75%FFCS) of FFCS be used in diets during the grower phase as it may lead to reduced performance when exceeded. Although in the other phases, FFCS can be included up to the maximum levels evaluated (100% replacement of soybean oilcake meal) without any detrimental effects.The aim of the study in Chapter 5 was to evaluate the effect of different dietary FFCS inclusion levels on the feathers, leather and meat composition of slaughter ostriches. The end products of the South African Black ostriches slaughtered in Chapter 4 were used during this trial. The only differences between diets regarding feather yields were within chick body short (P =0.021) and unmarketable feathers (P =0.011). The 50%FFCS resulted in the heavier yields of chick body short feathers (283.2 ± 14.84 g), however, it did not differ from the 0%FFCS, 25%FFCS and 75%FFCS. The 100%FFCS resulted in lighter yields (202.3 ± 14.84 g) of chick body short feathers, although not differing from the 75%FFCS. The 50%FFCS had the lightest yield (97.1 ± 13.18 g)of unmarketable feathers, differing from all the other diets. The rest of the diets did not differ and yielded anaverage of 161.2 ± 13.18 g unmarketable feathers. Skin thickness was the only leather trait showing differences (P =0.038) between diets. With the 0%FFCS resulting in thicker skins (0.65 ± 0.027 mm), not differing from the 25%FFCS and 50%FFCS diets. The 100%FFCS resulted in thinner skins (0.53 ± 0.027 mm), not differing from the 50%FFCS or 75%FFCS diets. Moisture and protein concentration of the meat were the only chemical components showing differences (P =0.008 and P =0.004, respectively) between diets. Meat from the 100%FFCS was found to have higher moisture concentrations (77.0 ± 0.29%). The 25%FFCS meat resulted in the lowest mean moisture concentration (75.2 ± 0.24%), not differing from the 0% and 50%FFCS meat. The inverse of moisture concentration could be seen with regards to protein concentration where the 25%FFCS diet resulted in the highest meat protein concentration (22.6 ± 0.19%), not differing from the 0%FFCS and 50%FFCS diets' meat. The 100%FFCS diet resulted in the lowest (20.9 ± 0.23%) meat protein concentration.Dietary FFCS inclusion had beneficial effects on the fatty acid profile of the abdominal fat tissue. Total saturated fatty acids concentrations decreased from 37.8% (0%FFCS) to 20.3% (100%FFCS) of total identified fatty acids. Total MUFA concentrations increased from 39.7% for the 0%FFCS fed birds to 51.0% for the 100%FFCS fed birds. The total PUFA concentrations also increased from 22.1% for the 0%FFCS fed birds to 28.7% for the 100%FFCS fed birds. These changes resulted in the PUFA:SFA ratios to increase from 0.60 (0%FFCS) to 1.43 (100%FFCS). Both n-6 and n-3 fatty acids increased with an increase in FFCS inclusion, however the n-6:n-3 ratio showed a beneficial decrease from 3.20 for the 0%FFCS fed birds to 2.28 for the 100%FFCS birds.Overall it is recommended that full-fat canola seed can be used to replace up to 75% (not exceeding inclusion levels used within each growth phase in this trial) of the soybean oilcake meal in slaughter ostrich diets. Prescribed replacement of soybean oilcake meal with FFCS can be done without affecting growth of ostriches or the quality of end products, and achieve similar results as current standard commercial diets.

[发布机构] Stellenbosch University