Could the breed composition improve performance and change the enteric methane emissions from beef cattle in a tropical intensive production system?

The Effects of Supplemental Feeding on Methane Emissions from Yak Grazing in the Warm Season

The yak industry constitutes a pivotal segment of livestock development across the Qinghai-Tibetan Plateau and adjacent pastoral regions. Existing studies have shown that supplemental feeding for grazing yaks significantly improves meat quality and growth performance, but its effect on enteric methane (CH4) emission from yaks has never been reported, so the present experiment aimed to investigate the effect of supplemental feeding of grazing yaks on CH4 emissions in three different periods of the warm season. Thirty male yaks were randomly assigned to two groups, with 15 yaks per group, The groups were designated as the grazing group (GR), with traditional grazing methods and with an initial body weight of 94.56 ± 3.9 kg, and the supplemental feeding group (GRS) with an initial body weight of 95.01 ± 4.1 kg, which received 1500 g/d of supplemental feed for 120 days. The methane emissions of the two groups were measured at the late regreening period (LRP), the greening-grass period (GGP), and the browning period (BRP) using the SF6 tracer method. The results showed that GRS increased (p < 0.01) the total DMI during warm season but decreased (p < 0.01) the forage intake at the LRP and GGP, resulting in a significantly reduced methane yield per kg of BW gain and per kg of DMD in warm-season grazing yaks (p < 0.01), a significantly reduced methane production per kg of DMI and methane energy to gross energy ratio in grazing yaks during the GGP (p < 0.05), and a similarly significantly decrease in methane production per kg of DMI and methane energy to gross energy ratio in grazing yaks during the BRP (p < 0.01). In conclusion, supplemental nutrition for grazing yaks during the warm season in alpine grasslands significantly enhances growth performance, reduces methane emissions, and improves dietary energy utilization efficiency.

A meta-analysis of probiotic interventions to mitigate ruminal methane emissions in cattle: implications for sustainable livestock farming

In recent years, the significant impact of ruminants on methane emissions has garnered international attention. While dietary strategies have been implemented to solve this issue, probiotics gained the attention of researchers due to their sustainability. However, it is challenging to ascertain their effectiveness as an extensive range of strains and doses have been reported in the literature. Hence, the objective of this experiment was to perform a meta-analysis of probiotic interventions aiming to reduce ruminal methane emissions from cattle. From 362 articles retrieved from scientific databases, 85 articles were assessed independently by two reviewers, and 20 articles representing 49 comparisons were found eligible for meta-analysis. In each study, data such as mean, SD, and sample sizes of both the control and probiotic intervention groups were extracted. The outcomes of interest were methane emission, methane yield, and methane intensity. For the meta-analysis, effect sizes were pooled using a fixed effect or a random effect model depending on the heterogeneity. Afterward, sensitivity analyses were conducted to confirm the robustness of the findings. Overall pooled standardized mean differences (SMDs) with their confidence intervals (CIs) did not detect significant differences in methane emission (SMD = -0.04; 95% CI = -0.18-0.11; P = 0.632), methane yield (SMD = -0.08; 95% CI = -0.24-0.07; P = 0.291), and methane intensity (SMD = -0.22; 95% CI = -0.50-0.07; P = 0.129) between cattle supplemented with probiotics and the control group. However, subgroup analyses revealed that multiple-strain bacterial probiotics (SMD = -0.36; 95% CI = -0.62 to -0.11; P = 0.005), specifically the combination of bacteria involved in reductive acetogenesis and propionate production (SMD = -0.71; 95% CI = -1.04 to -0.36; P = 0.001), emerged as better interventions. Likewise, crossbreeds (SMD = -0.48; 95% CI = -0.78 to -0.18; P = 0.001) exhibited a more favorable response to the treatments. Furthermore, meta-regression demonstrated that longer periods of supplementation led to significant reductions in methane emissions (P = 0.001), yield (P = 0.032), and intensity (P = 0.012) effect sizes. Overall, the results of the current study suggest that cattle responses to probiotic interventions are highly dependent on the probiotic category. Therefore, extended trials performed with probiotics containing multiple bacterial strains are showing the most promising results. Ideally, further trials focusing on the use of probiotics to reduce ruminal methane in cattle should be conducted to complete the available literature.

Methane Emission, Carbon Footprint and Productivity of Specialized Dairy Cows Supplemented with Bitter Cassava (Manihot esculenta Crantz)

The objective of this research was to determine the effect of cassava (Manihot esculenta Crantz) supplementation on enteric methane (CH4) emissions, carbon footprint, and production parameters in dairy cows. Daily concentrate supply for Jersey and Jersey * Holstein breeds was evaluated in four treatments (T): T1: 100% commercial concentrate; T2: 70% concentrate + 30% cassava leaves; T3: 70% concentrate + 30% cassava roots; and T4: 70% concentrate + 15% cassava leaves + 15% cassava root chips. Measurements of CH4 emissions were performed using the polytunnel technique. Average daily dry matter intake ranged from 7.8 to 8.5 kg dry matter (DM). Cassava leaves were characterized by a high crude protein (CP) content (171 g CP/kg DM), with 5 times more neutral detergent fiber (NDF) content than cassava root (587 vs. 108 g NDF/kg DM). Average enteric CH4 emissions per animal ranged from 194 to 234 g/d (p > 0.05). The carbon footprint was reduced by replacing 30% of the concentrate with cassava leaves and/or roots. Energy-corrected milk production was 1.15 times higher in Jersey * Holstein animals than Jersey cows (47 vs. 55 kg). Therefore, supplementation with cassava leaves and/or roots is a nutritionally and environmentally sustainable strategy.

Effects of the Breeding Strategy Beef-on-Dairy at Animal, Farm and Sector Levels

The decline in farm revenue due to volatile milk prices has led to an increase in the use of beef semen in dairy herds. While this strategy ("Beef-on-dairy" (BoD)) can have economic benefits, it can also lead to unintended consequences affecting animal welfare. Semen sale trends from breeding organizations depict increasing sales of beef semen across the globe. Calves born from such breeding strategies can perform better when compared to purebred dairy calves, especially in terms of meat quality and growth traits. The Beef-on-dairy strategy can lead to unintentional negative impacts including an increase in gestation length, and increased dystocia and stillbirth rates. Studies in this regard have found the highest gestation length for Limousin crossbred calves followed by calves from the Angus breed. This increase in gestation length can lead to economic losses ranging from 3 to 5 US$ per animal for each additional day. In terms of the growth performance of crossbred animals, literature studies are inconclusive due to the vast differences in farming structure across the regions. But almost all the studies agree regarding improvement in the meat quality in terms of color, fiber type, and intra-muscular fat content for crossbred animals. Utilization of genomic selection, and development of specialized Beef-on-dairy indexes for the sires, can be a viable strategy to make selection easier for the farmers.

Beef Steers and Enteric Methane: Reducing Emissions by Managing Forage Diet Fiber Content

Understanding the methane (CH4) emissions that are produced by enteric fermentation is one of the main problems to be solved for livestock, due to their GHG effects. These emissions are affected by the quantity and quality of their diets, thus, it is key to accurately define the intake and fiber content (NDF) of these forage diets. On the other hand, different emission prediction equations have been developed; however, there are scarce and uncertain results regarding their evaluation of the emissions that have been observed in forage diets. Therefore, the objectives of this study were to evaluate the effect of the NDF content of a forage diet on CH4 enteric emissions, and to evaluate the ability of models to predict the emissions from the animals that are consuming these forage diets. In total, thirty-six Angus steers (x¯ = 437 kg live weight) aged 18 months, blocked by live weight and placed in three automated feeding pens, were used to measure the enteric CH4. The animals were randomly assigned to two forage diets (n = 18), with moderate (<50%, MF) and high (>50%, HF) NDF contents. Their dry matter intake was recorded individually, and the CH4 emissions were measured using the SF6 tracer gas technique. For the model evaluation, six prediction equations were compared with 29 studies (n = 97 observations), analyzing the accuracy and precision of their estimates. The emission intensities per unit of DMI, per ADG, and per gross energy intake were significantly lower (p < 0.05) in the animals consuming the MF diet than in the animals consuming the HF diet (21.7 vs. 23.7 g CH4/kg DMI, 342 vs. 660 g CH4/kg ADG, and 6.7% vs. 7.5%, respectively), but there were no differences in the absolute emissions (p > 0.05). The best performing model was the IPCC 2006 model (r2 = 0.7, RMSE = 74.04). These results show that reducing the NDF content of a forage diet by at least 10% (52 g/kg DM) reduces the intensity of the g CH4/kg DMI by up to 8%, and that of the g CH4/kg ADG by almost half. The use of the IPCC 2006 model is suitable for estimating the CH4 emissions from animals consuming forage-based diets.

Feed intake, emission of enteric methane and estimates, feed efficiency, and ingestive behavior in buffaloes supplemented with palm kernel cake in the Amazon biome

The use of palm kernel cake as an alternative to conventional ingredients, due to the presence of residual fat, can also reduce methane emissions. The objective of the study was to evaluate, in two different experiments, the effects of palm kernel cake supplementation on feed intake, enteric methane production and estimates, and the ingestive behavior of buffaloes in the Amazon biome. In experiment 1, to evaluate feed intake, methane production, and feed efficiency, 20 crossbred females, dry and empty, with a mean age of 34 months and an initial body weight of 514 ± 69 kg, were supplemented with palm kernel cake for 60 days. The supply was calculated in relation to body weight (BW) in four treatments: 0% (control); 0.25, 0.50, and 1% of palm kernel cake, distributed in a completely randomized design. In experiment 2, to evaluate the ingestive behavior, 24 mixed-breed, dry, and non-pregnant buffaloes supplemented with palm kernel cake were evaluated in the less rainy season (LR) and the wettest season (WS) of the eastern Amazon, distributed in a completely randomized in the same treatments as experiment 1. The inclusion of palm kernel cake in the supplementation increased the feed intake of dry matter and components (MM, OM, CP, NDF, ADF, and EE) (P < 0.01), reducing the production of enteric methane intake (P < 0.01), the ratio per kg of meat produced (P < 0.01) and feed efficiency (P < 0.01), and influenced the ingestive behavior (time grazing, rumination, and idleness) during the day. We suggest that further research be carried out to verify the results and improve the use of this co-product as a methanogenesis mitigator.

Taxonomy and Functional Diversity in the Fecal Microbiome of Beef Cattle Reared in Brazilian Traditional and Semi-Intensive Production Systems

The importance of beef production for economy of Brazil and the growing demand for animal protein across the globe warrant an improvement in the beef production system. Although most attention has been on modulation of the rumen microbiome to improve ruminant production, the role of the lower gut microbiome in host health and nutrition remains relatively unexplored. This work aimed to investigate the taxonomy and functional variations in the fecal microbiome of Brazilian beef cattle reared in two different production systems using a metagenomic approach. Sixty male beef cattle from six farms representing semi-intensive (I, n = 2) and traditional (T, n = 4) Brazilian beef production systems were enrolled in the study. Shotgun sequencing was used to characterize taxonomic and functional composition and diversity of the microbiome in fecal samples collected from each animal. Fecal samples were analyzed for copper (Cu), lead (Pb), nitrogen (N), phosphorous (P), selenium (Se), and zinc (Zn) and stable isotopes of carbon (¹³C) and nitrogen (¹⁵N). The fecal microbiome was influenced by the beef production systems with greater functional and lower taxonomic diversity in beef cattle feces from I systems compared with that from T systems. The concentration of N, P, and Zn was higher in beef cattle feces from I systems compared with that from T systems and was associated with taxonomic and functional profile of fecal microbiome in I system, suggesting the role of fecal nutrients in shaping system-specific microbiome. Semi-intensive management practices led to a more complex but less connected fecal microbiome in beef cattle. The microbial community in beef cattle feces from I systems was characterized by greater abundance of beneficial bacteria (phylum Firmicutes and butyrate-producing bacteria family Lachnospiraceae and genera Anaerostipes, Blautia, Butyrivibrio, Eubacterium, Roseburia, and Ruminococcus). In addition, the fecal abundance of microbial genes related to immune system, nutrient metabolism, and energy production was greater in beef cattle raised under I systems compared with that under T systems. Findings of the current study suggest that semi-intensive management practices could facilitate the development of a healthier and more efficient fecal microbiome in beef cattle by driving an increase in the abundance of beneficial bacteria and functional genes.

Effects of Feeding Level and Breed Composition on Intake, Digestibility, and Methane Emissions of Dairy Heifers

The dairy Nutrients Requirements of Cattle (NRC) was developed using data from purebred Holsteins and it might not accurately predict the performance of crossbred cattle. Our objectives were to evaluate the effects of two feeding levels (FLs) and three breed compositions (BCs) on nutrient intake, digestibility, performance, and methane (CH₄) emissions of prepubertal dairy heifers. We used thirty-six heifers from three BCs: purebred Holstein (H), purebred Gyr (G), and F1 Holstein × Gyr (HG). Each BC had 12 animals and the experiment was designed as twelve incomplete three by three Latin squares, in a factorial arrangement three by two, with three BCs and two FLs (400 and 800 g/day). Total tract nutrient digestibility was determined using total fecal collection and DMI was individually measured. The data were analyzed using the PROC MIXED in SAS. Dry matter intake of all nutrients increased from the medium to high feeding level and the nutrients digestibility coefficients did differ among BCs. Achieved body weight gain in the medium FL treatment was greater than those predicted using the NRC, suggesting that crossbred and Gyr heifers have similar performance to Holsteins. Breed composition does not influence body weight gain of confined dairy heifers, but Holstein heifers fed a medium FL had higher feed efficiency and reduced CH₄ emissions intensity.

Does grazing management provide opportunities to mitigate methane emissions by ruminants in pastoral ecosystems?

Agriculture, and livestock production in particular, is criticized for being a contributor to global environmental change, including emissions of greenhouse gases (GHG). Methane (CH₄) from grazing ruminants accounts for most of livestock's carbon footprint because a large share of them are reared under suboptimal grazing conditions, usually resulting in both low herbage intake and animal performance. Consequently, the CH₄ quota attributed to animal maintenance is spread across few or no animal outputs, increasing the CH₄ intensity [g CH₄/kg live weight (LW) gain or g CH₄/kg milk yield]. In this review, the generalized idea relating tropical pastures with low quality and intrinsically higher CH₄ intensity is challenged by showing evidence that emissions from animals grazing tropical pastures can equal those of temperate grasses. We demonstrate the medium-to-high mitigation potential of some grazing management strategies to mitigate CH₄ emissions from grazing ruminants and stress the predominant role that sward canopy structure (e.g., height) has over animal behavioral responses (e.g., intake rate), daily forage intake and resulting CH₄ emissions. From this ecological perspective, we identify a grazing management concept aiming to offer the best sward structure that allows animals to optimize their daily herbage intake, creating opportunities to reduce CH₄ intensity. We show the trade-off between animal performance and CH₄ intensity, stressing that mitigation is substantial when grazing management is conducted under light-to-moderate intensities and optimize herbage intake and animal performance. We conclude that optimizing LW gain of grazing sheep and cattle to a threshold of 0.14 and 0.7 kg/day, respectively, would dramatically reduce CH₄ intensity to approximately 0.2 kg CH₄/kg LW gain, as observed in some intensive feeding systems. This could represent a mitigation potential of around 55% for livestock commodities in pasture-based systems. Our results offer new insights to the debate concerning mitigation of environmental impacts of pastoral ecosystems.