Effect of the dietary supplementation with sunflower oil-enriched bromoform from Asparagopsis taxiformis on lambs' growth, health, and ruminal methane production.

The red seaweed Asparagopsis taxiformis has a potent antimethanogenic effect, which has been proven both in vitro and in vivo. Vegetable oil immersions of this seaweed (hereafter Bromoil) help stabilise the bromoform (CHBr3) responsible for its antimethanogenic effect. We evaluate the effects of increasing the levels of CHBr3 in lamb diets on growth performance, methane (CH4) production, animal health and meat quality. Twenty-four Merino Branco ram lambs were fed a ground complete compound feed, supplemented with 50 mL/kg DM of sunflower oil with different CHBr3 content. The treatments were defined by the CHBr3 doses in the oil: 0 mg (control - B0), 15 mg (B15), 30 mg (B30) and 45 mg (B45) of CHBr3 per kg of feed DM. The feed was prepared daily by mixing Bromoil with the compound feed. At the end of the experiment, the lambs were sacrificed, the ruminal content was collected for in vitro fermentation to evaluate CH4 production and organic matter (OM) degradability, and the rumen mucosa was sampled for histological examination. Meat samples were collected for chemical composition and CHBr3 analysis. The half-life of CHBr3 in the air-exposed feed was 3.98 h making it very difficult to establish the practiced level of CHBr3 supplementation. Lambs-fed treatments B30 and B45 decreased DM intake by up to 28%. Average daily gain was also reduced due to CHBr3 supplementation, with B45 showing results 40% lower than B0. DM feed conversion ratio was similar for all treatments. The degradability of OM, the volume of total gas and of gas without CH4 were unaffected by the experimental treatments, evaluated by the in vitro method. However, the volume of CH4 decreased by up to 75% for treatments above 30 mg/kg DM, while the yield of CH4/g OM degraded was reduced by up to 78% with treatments above 30 mg/kg DM. Meat chemical composition was not affected by Bromoil supplementation and no traces of CHBr3 were found in meat samples. During this experiment, the animals presented normal health and behaviour. However, postslaughter examination of the rumen showed distinct lesions on the ventral region of the rumen mucosa of animals supplemented with Bromoil. These lesions were more severe in the animals receiving treatments B30 and B45. This research determined that although concentrations of CHBr3 in the diet above 30 mg/kg DM helped to reduce CH4 emissions, it negatively affected the performance and rumen wall.

Effects of sunflower oil infusions of Asparagopsis taxiformis on in vitro ruminal methane production and biohydrogenation of polyunsaturated fatty acids.

Asparagopsis taxiformis inhibits ruminal methane (CH4) production due to its bromoform (CHBr3) content. The immersion of A. taxiformis in edible vegetable oils allows the extraction and stabilization of the highly volatile CHBr3 in the oil phase. The objectives of this study were to explore the effects of adding sunflower oils with increasing concentrations of CHBr3 on in vitro ruminal methanogenesis and biohydrogenation. Five batches of 48-h in vitro incubations were performed in 14 fermentation bottles, using rumen inocula collected shortly after the slaughter of young crossbred bulls and 1 g of dry matter (DM) from a total diet of mixed feed without added oil (control) or with 60 µL of sunflower oil per gram of DM as the substrate. The treatments were the CHBr3 content in the oil added: 0 µg (B0), 25 µg (B25), 50 µg (B50), 75 µg (B75), 100 µg (B100), and 150 µg (B150) of CHBr3 per gram of substrate DM. Organic matter (OM) degradability, total gas, CH4, volatile fatty acids (VFA), long-chain fatty acids, and dimethyl acetals (DMA) were analyzed at the end of each incubation. Data were analyzed with a model considering the treatments as the fixed effect and the run as a random block and using orthogonal contrasts. Degradability of OM was higher in the control group and was unaffected by CHBr3 concentration. Total gas production per gram of degraded OM was unaffected by treatments and averaged 205 ± 29.8 mL/g. Methane (mL) production decreased linearly with increasing CHBr3 concentrations, with 33%, 47%, and 87% reductions for B75, B100, and B150, respectively. Total VFA concentration was unaffected by oil inclusion but was reduced by 20% in CHBr3-containing treatments, although without any dose-response pattern. The molar percentage of acetate decreased linearly, whereas propionate and butyrate increased linearly with the increasing CHBr3 dosage. Including oil in the diet decreased the branched-chain fatty acids and DMA content. Increasing CHBr3 concentrations did not affect branched-chain fatty acids, but linearly increased most of the identified DMA. Adding oil to the control diet increased the 18:2n-6, whereas increasing the concentration of CHBr3 had no effect on 18:2n-6 but decreased linearly the 18:0 and increased the trans-18:1 isomers. The results obtained provide evidence that oil immersions of A. taxiformis can successfully inhibit ruminal production of CH4 in vitro at doses of 100 and 150 µg/g DM, and simultaneously modulate biohydrogenation.

The effects of improving low dietary protein utilization on the proteome of lamb tissues.

Cistus ladanifer L. is a common shrub endemic to the Mediterranean region with high levels of condensed tannins (CT). CT form complexes with dietary protein resisting microbial degradation in the rumen, which enhances dietary protein utilization in ruminant diets. The objective of this study was to evaluate the utilization of CT in the diet of lambs on the proteomes of muscle, hepatic and adipose tissues. Twenty-four Merino Branco ram lambs were randomly allocated to three treatments (n = 8): C - control (160 g crude protein (CP)) per kg DM, RP - reduced protein (120 g CP/kg DM); and RPCT - reduced protein (120 g CP/kg DM) treated with CT extract. At the end of the trial, lambs were slaughtered and the longissimus lumborum muscle, hepatic and peri-renal adipose tissues sampled. A two-way approach was used for proteomic analysis: 2D-DIGE and nanoLC-MS. In the muscle, C lambs had lower abundance proteins that partake in the glycolysis pathway than the lambs of other treatments. Control lambs had lower abundance of Fe-carrying proteins in the hepatic tissue than RP and RPCT lambs. The latter lambs had highest abundance of hepatic flavin reductase. In the adipose tissue, C lambs had lowest abundance of fatty-acid synthase. SIGNIFICANCE: soybean meal is an expensive feedstuff in which intensive animal production systems heavily rely on. It is a source of protein extensively degraded in the rumen, leading to efficiency losses on dietary protein utilization during digestion. Protection of dietary protein from extensive ruminal degradation throughout the use of plants or extracts rich in CT allow an increase in the digestive utilization of feed proteins. In addition to enhance the protein digestive utilization, dietary CT may induce other beneficial effects in ruminants such as the improvement of the antioxidant status.