Digestibility, nitrogen balance and weight gain in sheep fed with diets supplemented with different seaweeds
Three completely randomised design experiments examined the effects of the inclusion of three seaweed species (Ruppia sp., Ulva sp. or Chaetomorpha sp.) into the diet on digestibility and nitrogen balance in Barbarine sheep. Diets were composed of oat hay ad libitum supplemented with 600 g of concentrate. Seaweeds were incorporated into the concentrate at increasing levels (0, 200, 300 or 400 g seaweed kg−1 concentrate, dry matter (DM) basis) in replacement of other ingredients. Feed intake and water consumption were increased (P < 0.01) linearly with Ruppia supplementation. As the proportion of Ruppia was increased in the diet, the digestibility of organic matter decreased linearly (P < 0.01) from 0.698 (no seaweed) to 0.642 (400 g seaweed kg−1 concentrate). Increasing the level of inclusion of Chaetomorpha up to 300 g kg−1 did not affect the intake of concentrate. Organic matter digestibility decreased linearly (P < 0.001) from 0.685 with the control diet to 0.622 with the diet containing 400 g Chaetomorpha kg−1 concentrate. The level of inclusion of Ulva did not affect feed intake or water consumption, but decreased linearly (P > 0.001) organic matter digestibility from 0.637 with the control diet to 0.599 with the diet containing 400 g Ulva kg−1 concentrate. In all the experiments, nitrogen balance was positive and there were no differences among levels of seaweed supplementation in N retention or daily weight gain. These results suggest that seaweeds such as Ruppia, Ulva or Chaetomorpha can be incorporated into sheep concentrates up to 30% (DM basis) without adverse effects on feed digestibility or growth performance.
KeywordsSeaweed Sheep Feeding Digestibility Feed
The authors are grateful to the contribution of the director and the workers in the livestock industry of Tabarka (North of Tunisia). Special thanks to Mr. Boussbiaa and Mr. Mabrouk for their involvement.
Compliance with ethical standards
The experiments were carried out at the Small Ruminants Research Unit of the Institut National de la Recherche Agronomique de Tunisie (INRAT) in strict accordance with good animal practices as defined by national authorities and European Union Directive 2010/63/EU. The experimental animal procedures complied with the institutional guidelines of INRAT and were conducted by trained specialised personnel to ensure animal welfare.
Conflict of interest
The authors declare that there are no conflicts of interest.
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