Effects of High-Forage Diets Containing Raw Flaxseeds or Soybean on In Vitro Ruminal Fermentation, Gas Emission, and Microbial Profile

Lipid metabolism plays an important role in the energy economy of ruminants. However, its interactions of fat, rumen fermentation, gas emission, and microorganisms are not yet clear. This study evaluated the effect of adding raw oilseeds to high-forage diets on in vitro ruminal fermentation, gas composition, and microbial profile. Three isoenergetic and isoproteic experimental diets were designed and used as fermentation substrate: control treatment (CON group) was the basal diet lacking oilseeds, the other two treatments were the basal diet supplemented by 100 g/kg dry matter (DM) raw whole soybean (S group) and 50 g/kg DM raw flaxseed (F group), respectively. Data showed that the acetate, butyrate, and total VFA concentration of culture fluids in the S group were lower (p < 0.05) than in the F group. There was a tendency to a higher level (p = 0.094) of propionate concentration in the F group compared with the other two groups. The gas production in the F group was higher (p < 0.05) than in the control group. There was a lower abundance of Sutterella (p < 0.05) and a greater abundance of Butyrivibrio (p < 0.05) in both of the two oilseed treatments. Methanobrevibacter (p = 0.078) in the F group was the lowest. Our results suggested that CH4 emission could be inhibited with flaxseed supplementation by propionate production metabolism, biohydrogenation of unsaturated fatty acid (FA), and toxicity to Methanobrevibacter, while regarding soybean seed supplementation, the emission of CH4 was more likely to be reduced through biohydrogenation of unsaturated FA modulated by Butyrivibrio.

PSXIV-4 Meta-analysis of the effects of monensin on growth and bloat of growing beef calves on pasture

This meta-analysis investigated the impacts of monensin on performance of stocker cattle on high-forage diets. The stocker performance analysis resulted from 38 experiments with 73 mean comparisons; bloat analysis was conducted with 12 experiments with 23 mean comparisons. The metaphor package (version 2.4-0) for R (version 4.0.3; www.r-project.org) was used to determine the overall effect size of monensin compared to a negative control. Each study’s n, means, and SEM or P-value was used to calculate the mean difference and estimate of within study variance for responses of interest. Moderators of monensin response considered in the analysis were delivery method, dose, study duration, initial calf BW, diet ME and CP, and forage category. Initial BW and basal ADG averaged 236 ± 45.9 kg and 0.72 ± 0.28 kg/day, respectively. In the ADG analysis the only significant moderator of those considered was length of the study (P &lt; 0.01), as duration of the study increased the ADG response to monensin decreased by 0.0007 kg/day. For the average 112-day length of study, the average monensin response is estimated to be 0.0784 kg/day increase in average daily gain. Sufficient information was presented in only 18 citations representing 40 mean comparisons for determining the effect of monensin on BW at the end of the experiment, estimated by (P &lt; 0.01) monensin response (increased ending BW, kg) = 22.3 – 0.05 (initial calf BW, kg). Thus, for the average initial BW of 235 kg the average monensin response is estimated to be 10.6 kg increase in average ending BW. The incidence (-20%) and severity (-0.7 bloat scores) of bloat was found to be reduced in bloat prone pastures. There is ample evidence that monensin increases performance of growing calves on high forage diets along with reducing the incidence and severity of bloat.

Use of cashew and castor essential oils to improve fibre digestibility in high forage diets: digestibility, ruminal fermentation and microbial protein synthesis

High forage diets in the tropics are less efficient and more contaminating due to high energy losses as methane and the low digestibility of tropical forages. The objective of the study was to determine the effects of essential oils (EO) of Anacardium occidentale and Ricinus communis as additives in high forage diets on intake, digestibility, ruminal fermentation and synthesis of microbial protein. Four ‘Holstein’ steers fitted with ruminal cannula were used in a 4 × 4 Latin square design (21-day period). The treatments were 1, 2, 4 and 8 g day-1 EO per animal (essential oils, Oligobasics®). The diet was total mixed ration (TMR) of Brachiaria hay (Brachiaria humidicola cv. Lanero) and concentrate (ground corn, soybean meal, ammonium sulphate, urea and minerals) in an 80:20 ratio. Differences were observed in the digestibility of neutral detergent fibre (NDF) and total digestible nutrients (TDN) in levels above 2 g day -1 EO (P < 0.05). The VFA (volatile fatty acids) acetate and propionate were higher in diets with 2 g day -1 EO (P < 0.05), without affecting the acetate:propionate ratio. Levels above 2 g day -1 EO negatively affected the faecal N excretion (P < 0.05). The inclusions of A. occidentale and R. communis EOs at 2 g day-1 per day animal improved fibre digestion and decreased N excretion. These results indicate that this mixture of EOs may have strong antimicrobial activity at lower doses. The N losses, fibre digestion and digestibility could be improved with the use of cashew and castor essential oils in high forage diets.

Methionine-balanced diets improve cattle performance in fattening young bulls fed high-forage diets through changes in nitrogen metabolism

Ruminants fed high-forage diets usually have a low feed efficiency, and their performances might be limited by methionine (Met) supply. However, the INRA feeding system for growing cattle does not give recommendation for this amino acid (AA). This study aimed to assess the effects of Met-balanced diets on animal performance and N metabolism in young bulls fed high-forage diets formulated at or above protein requirements. Four diets resulting from a factorial arrangement of two protein levels (Normal (13·5 % crude protein) v. High (16·2 % crude protein)) crossed with two Met concentrations (unbalanced (2·0 % of metabolisable protein) v. balanced (2·6 % of metabolisable protein)) were tested on thirty-four fattening Charolais bulls for 7 months before slaughter. Animal growth rate was greater in Met-balanced diets (+8 %; P = 0·02) with a trend for a greater impact in High v. Normal protein diets (P = 0·10). This trend was observed in lower plasma concentrations of branched-chain AA only when Met supplementation was applied to the Normal protein diet (P ≤ 0·06) suggesting another co-limiting AA at Normal protein level. Feed conversion efficiency and N use efficiency were unaffected by Met supplementation (P > 0·05). However, some plasma indicators suggested a better use of AA when High protein diets were balanced v. unbalanced in Met. The proportion of total adipose tissue in carcass increased (+5 percent units; P = 0·03), whereas that of muscle decreased on average 0·8 percent units (P = 0·05) in Met-balanced diets. Our results justify the integration of AA into dietary recommendations for growing cattle.

Linseed and glycerol in forage diets effect methane production and rumen fermentation parameters in a Rusitec semi-continuos system

Context The use of oilseeds as a feed ingredient has been proposed to improve fatty acid profiles and reduce methane (CH4) emissions. Glycerol has been used as a common additive in ruminant feeding systems with variable effects on CH4 production. The effects of the combination of these ingredients remain unknown. Aims The aim of this study was to assess the effects of feeding linseed and increasing concentrations of glycerol in forage diets supplemented with corn grain on nutrient disappearance, CH4 production and rumen fermentation parameters. Methods Experimental diets were: control (70:30% hay:corn); linseed (70:15 :15% hay:corn:linseed); 5% glycerol (70:10:15:5% hay:corn:linseed:glycerol); 10% glycerol (70:5:15:10% hay:corn:linseed:glycerol). Diets were incubated in a completely randomised design with four replicates per treatment in a Rusitec apparatus for 15 days (10 days adaptation, 5 days sampling). Key results Total VFA production (VFA, mmol/day) was quadratically increased due to glycerol concentration in the diets (P = 0.009). Acetate:propionate (A:P) decreased by the inclusion of linseed (P &lt; 0.001) and glycerol into the diets (P &lt; 0.001). Linseed inclusion in the diet reduced CH4 production, mg/DM disappeared (P = 0.004) by up to 36%. These effects were not altered by the addition of glycerol into the diets. Ammonia nitrogen (NH3-N) production increased 2-fold in the linseed-added diets, but this effect was partially reverted by increasing glycerol concentrations in the diets (P &lt; 0.001). Crude protein (CP) disappearance increased (P &lt; 0.001) in the linseed added diets, with no effect of glycerol addition. Neutral detergent fibre (aNDFom; P = 0.005) disappearance was increased by the addition of linseed to the diet. Conclusions The use of linseed in ruminant diets reduces CH4 emissions but increases NH3-N production in a Rusitec system. This latter effect is partially reverted by glycerol inclusion in the diet. Propionate production increases with the inclusion of glycerol, but does not alter CH4 production. Including linseed increases the in vitro CP disappearance without affecting DM total disappearance. Implications Care should be taken with the use of oilseeds in ruminant diets as it can reduce CH4 emissions but may cause important increases in NH3 emissions. Inclusion of glycerol may partially overcome this latter issue.