Animal board invited review: The effect of diet on rumen microbial composition in dairy cows.

Palmonari A ，Federiconi A ，Formigoni A 《-》

Milk production responses, rumen fermentation, and blood metabolites of dairy cows fed increasing concentrations of forage rape (Brassica napus ssp. Biennis).

The aim of this study was to determine animal performance, rumen fermentation, and health-related blood metabolites of dairy cows in mid lactation fed with increasing levels (30 and 45%) of forage rape (FR) in the diet. Twelve pregnant multiparous lactating Holstein-Friesian dairy cows were randomly allocated to 1 of 3 dietary treatments in a replicated 3 × 3 Latin square design. The experiment was divided into three 21-d periods. For the control diet, 13.0 kg (dry matter, DM) of grass silage, 3.0 kg DM of commercial concentrate, 2.7 kg of DM cold-pressed extracted canola meal, and 0.45 kg DM of solvent-extracted soybean meal were offered daily. For the other two treatments, 30 and 45% of the DM from silage, canola meal, and commercial concentrate were replaced in equal proportions with FR. Data were analyzed individually using linear and quadratic orthogonal polynomials. Ingestive behavior was altered by the inclusion of FR. We observed a linear increase in eating time at the expense of rumination time. Nevertheless, total DM intake was not affected by dietary treatments, averaging 19.5 ± 0.24 kg of DM/d. Milk yield increased linearly with increasing concentration of FR in the diet. Thus, feed efficiency of cows (kg of milk/kg of DM intake) increased linearly with the percentage of FR in the diet. Inclusion of FR in the diet had no effect on milk composition or milk sensory characteristics. Mean rumen pH of cows decreased linearly from the control to the 45% FR diet; however, dietary treatments had no effect on the daily amount of time that rumen pH was below 5.8 (252 ± 71.4), indicating no risk of subacute ruminal acidosis. Concentrations of total volatile fatty acids in the rumen and molar proportions of acetate and butyrate were increased with FR inclusion, whereas the proportion of propionate was linearly reduced. Excretion of uric acid and total purine derivatives tended to be greater for cows fed FR, which resulted in a trend toward a linear increase in estimated microbial N flow. However, N use efficiency was not affected by FR inclusion. Although differences for some hematological measures (increased white blood cell and neutrophils counts) and a quadratic response for glutamate dehydrogenase for cows fed FR in the diet (decreased with inclusion of 30% and increased with 45% in the diet) were observed, all values were within appropriate ranges for dairy cows. These results indicated that including FR to dairy cow diets, up to 45% of diet DM, improved milk production due to changes in volatile fatty acids and predicted microbial N flow and had no negative effects on dairy cow health or sensory characteristics of milk.

Keim JP ，Daza J ，Beltrán I ，Balocchi OA ，Pulido RG ，Sepúlveda-Varas P ，Pacheco D ，Berthiaume R ... -  《-》

Impact of oil type and savory plant on nutrient digestibility and rumen fermentation, milk yield, and milk fatty acid profile in dairy cows.

Fat supplements are well known for their multiple beneficial effects on ruminant health, reproduction and productivity, and as a source for certain bioactive compounds in ruminant products. On the other hand, numerous phytochemicals have demonstrated the potential to improve rumen fermentation through modifying the volatile fatty acid (VFA) pattern to favour those with greater energy efficiency, boosting microbial protein synthesis, and decreasing methane emission and ruminal ammonia concentration. Savory is an aromatic plant rich in various phytochemicals (mainly carvacrol and flavonoids) that can alter ruminal metabolism of dietary fatty acids, potentially increasing the production of some bioactive compounds such as conjugated linoleic acids (CLAs). This study aimed to investigate combined effects of oil type (fish oil (FO) versus soybean oil (SO)) and the inclusion of savory (Satureja khuzistanica) plant (SP) in the diet on total tract digestibility of nutrients, rumen fermentation, milk yield and milk fatty acid profile in dairy cattle. Eight multiparous lactating Holstein cows were used in a replicated 4 × 4 Latin square design experiment with four diets and four 21-d periods. During each experimental period consisted of 14 days of adaptation and a 7-day sampling period, cows were randomly assigned to one of the four dietary treatments: the diet supplemented with 2% (DM basis) fish oil (FOD) or soybean oil (SOD), the FOD or SOD plus 370 g DM/d/head SP (FODs, SODs, respectively). The experimental diets were arranged in a 2 × 2 factorial design, with the fat sources as the first and SP as the second factor. The FO-supplemented diets had lower dry matter intake (DMI) and higher total tract digestibility than SO-supplemented diets (P < 0.05), and including SP in the diet improved total tract digestibility of dry matter (DM), organic matter (OM), ether extract (EE), and non-fibrous carbohydrates (NFC) (P < 0.05) without negatively affecting DMI. Rumen pH was lower with SO than with FO diets (P < 0.01) and increased with SP inclusion in the diet (P < 0.05). Total protozoa count and ruminal ammonia concentration decreased, and the branched-chain VFA (BCVFA) proportion increased with SP inclusion in the diet (P < 0.05). Milk production, as well as the concentration and yield of milk components (except lactose concentration) were higher with SO than with FO diets (P < 0.05), but these variables remained unaffected by SP. The milk concentrations of both non-esterified fatty acids (NEFA) and beta-hydroxybutyrate (BHB) were lower with SO compared to FO diets, and these variables were reduced by SP (P < 0.01). The proportions of both mono- and polyunsaturated FA (MUFA and PUFA, respectively) in milk were higher with FO than with SO diets (P < 0.01), and their proportions increased by SP at the expense of saturated FA (SFA) (P < 0.01). Including SP in the diet increased the proportions of all the milk n-3 FA (C18:3c, C20:5, and C22:6) by 21%, 40%, and 97%, respectively, and those of conjugated linoleic acids (C18:2 (c9,t11-CLA) and C18:2 (t10,c12-CLA)) by 23% and 62%, respectively. There was no interaction between oil type and SP for the assessed variables. Fish oil, despite reducing milk production and milk components, was more effective than soybean oil in enriching milk with healthy FA. These findings also show promise for SP as a feed additive with the potential to improve total tract digestibility, rumen fermentation and milk FA composition.

Golbotteh MM ，Malecky M ，Aliarabi H ，Zamani P ... -  《Scientific Reports》

Increasing linseed supply in dairy cow diets based on hay or corn silage: Effect on enteric methane emission, rumen microbial fermentation, and digestion.

We investigated the effects of increasing extruded linseed supply in diets based on hay (H; experiment 1) or corn silage (CS; experiment 2) on enteric methane (CH4) emission, rumen microbial and fermentation parameters, and rumen and total-tract digestibility. In each experiment, 4 lactating Holstein cows fitted with cannulas at the rumen and proximal duodenum were used in a 4×4 Latin square design (28-d periods). Cows were fed ad libitum a diet [50:50 and 60:40 forage:concentrate on a dry matter (DM) basis for experiments 1 and 2, respectively] without supplementation (H0, CS0) or supplemented with extruded linseed at 5% (H5, CS5), 10% (H10, CS10), and 15% (H15, CS15) of dietary DM (i.e., 1.8, 3.6 and 5.4% total fatty acids added, respectively). All measurements were carried out during the last 8 d of each period. Linseed supply linearly decreased daily CH4 emission in cows fed H diets (from 486 to 289g/d for H0 to H15, on average) and CS diets (from 354 to 207g/d for CS0 to CS15, on average). The average decrease in CH4 per kilogram of DM intake was, respectively, -7, -15, and -38% for H5, H10, H15 compared with the H0 diet, and -4, -8, and -34% for CS5, CS10, and CS15 compared with the CS0 diet. The same dose-response effect was observed on CH4 emission in percent of gross energy intake, per kilogram of nutrient digested, and per kilogram of 4% fat- and 3.3% protein-corrected milk (FPCM) in both experiments. Changes in the composition of rumen volatile fatty acids in response to increasing linseed supply resulted in a moderate or marked linear decrease in acetate:propionate ratio for H or CS diets, respectively. The depressive effect of linseed on total protozoa concentration was linear for H diets (-15 to -40%, on average, for H5 to H15 compared with H0) and quadratic for CS diets (-17 to -83%, on average, for CS5 to CS15 compared with CS0). Concentration of methanogens was similar among H or CS diets. The energetic benefits from the decreased CH4 emission with linseed supply in diets based on hay or corn silage did not improve digestibility or milk yield. Milk efficiency (kg of FPCM/kg of DM intake) was improved with linseed supply up to H10 in H diets and was unchanged in CS diets. Lower CH4 enteric emission from dairy cows fed linseed helps limit the environmental footprint of ruminant livestock.

Martin C ，Ferlay A ，Mosoni P ，Rochette Y ，Chilliard Y ，Doreau M ... -  《-》

Diet Influences Early Microbiota Development in Dairy Calves without Long-Term Impacts on Milk Production.

Gastrointestinal tract (GIT) microorganisms play important roles in the health of ruminant livestock and affect the production of agriculturally relevant products, including milk and meat. Despite this link, interventions to alter the adult microbiota to improve production have proven ineffective, as established microbial communities are resilient to change. In contrast, developing communities in young animals may be more easily altered but are less well studied. Here, we measured the GIT-associated microbiota of 45 Holstein dairy cows from 2 weeks to the first lactation cycle, using Illumina amplicon sequencing of bacterial (16S rRNA V4), archaeal (16S rRNA V6 to V8), and fungal (internal transcribed region 1 [ITS1]) communities. Fecal and ruminal microbiota of cows raised on calf starter grains and/or corn silage were correlated to lifetime growth as well as milk production during the first lactation cycle, in order to determine whether early-life diets have long-term impacts. Significant diet-associated differences in total microbial communities and specific taxa were observed by weaning (8 weeks), but all animals reached an adult-like composition between weaning and 1 year. While some calf-diet-driven differences were apparent in the microbiota of adult cows, these dissimilarities did not correlate with animal growth or milk production. This finding suggests that initial microbial community establishment is affected by early-life diet but postweaning factors have a greater influence on adult communities and production outcomes.IMPORTANCE The gut microbiota is essential for the survival of many organisms, including ruminants that rely on microorganisms for nutrient acquisition from dietary inputs for the production of products such as milk and meat. While alteration of the adult ruminant microbiota to improve production is possible, changes are often unstable and fail to persist. In contrast, the early-life microbiota may be more amenable to sustained modification. However, few studies have determined the impact of early-life interventions on downstream production. Here, we investigated the impact of agriculturally relevant calf diets, including calf starter and corn silage, on gut microbial communities, growth, and production through the first lactation cycle. Thus, this work serves to further our understanding of early-life microbiota acquisition, as well as informing future practices in livestock management.

Dill-McFarland KA ，Weimer PJ ，Breaker JD ，Suen G ... -  《-》