Effects of brown midrib 3 mutation in corn silage on dry matter intake and productivity of high yielding dairy cows

The effect of replacing conventional alfalfa hay with lower-lignin alfalfa hay on feed intake, nutrient digestibility, and energy utilization in lactating Jersey cows

Lower-lignin (LoL) varieties of alfalfa (Medicago sativa L.) have been developed in recent years, and have the potential to positively impact animal performance. The objective of this study was to evaluate the effects of increasing the proportion of LoL alfalfa hay in diets fed to lactating dairy cows. Research plots were planted with a conventional variety (CON; Dairyland Hybriforce 3400), and 2 LoL varieties (LLG; 54HVX42 and LLB; Aflorex HiGest 460). After harvest, the LoL varieties were blended in equal proportions for feeding. Twelve multiparous Jersey cows (100 ± 4 d in milk) were used in a 3 × 3 Latin square with 3 periods of 28 d. Cows were assigned to 3 diets containing 0 (CNTRL), 16.1 (MdLL), and 32.2% (HiLL) of the diet DM as LoL alfalfa hay, which replaced CON. The CON alfalfa had average CP, NDF, and lignin contents (DM basis) of 20.5 ± 1.15, 42.1 ± 1.37, and 6.81 ± 0.57%, respectively, while the LoL alfalfa averaged 19.8 ± 0.75, 39.9 ± 1.56, and 6.07 ± 0.28%, respectively. No difference was observed in DMI (20.4 ± 0.61 kg/d). No difference in milk yield was observed, averaging 31.0 ± 1.02 kg/d across treatments. Similarly, no difference was observed in ECM yield (averaging 36.2 ± 1.43 kg/d). Feed conversion (ECM/DMI) tended to increase linearly with LoL alfalfa inclusion (1.74 to 1.80 ± 0.03). No difference was observed for milk fat yield and content (1.39 ± 0.075 kg/d and 4.51 ± 0.219%) or milk protein yield and content (1.06 ± 0.041 kg/d and 3.43 ± 0.096%). Total methane production quadratically decreased from CNTRL to MdLL then increased to HiLL (441, 389, 412 ± 18.2 L/d, respectively). No differences were observed on total-tract digestibility of DM (averaging 67.2 ± 0.55%) and NDF (averaging 50.9 ± 1.56%). No difference was observed in the concentration of DE, ME or NEL was observed averaging 2.82 ± 0.021, 2.51 ± 0.027, and 1.72 ± 0.030 Mcal/kg respectively. Our results suggest that replacing CON alfalfa with LoL alfalfa has no effects on milk production, milk composition, or nutrient digestibility but may improve feed efficiency.

Silage maize as a potent candidate for sustainable animal husbandry development-perspectives and strategies for genetic enhancement

Maize is recognized as the queen of cereals, with an ability to adapt to diverse agroecologies (from 58^oN to 55^oS latitude) and the highest genetic yield potential among cereals. Under contemporary conditions of global climate change, C₄ maize crops offer resilience and sustainability to ensure food, nutritional security, and farmer livelihood. In the northwestern plains of India, maize is an important alternative to paddy for crop diversification in the wake of depleting water resources, reduced farm diversity, nutrient mining, and environmental pollution due to paddy straw burning. Owing to its quick growth, high biomass, good palatability, and absence of anti-nutritional components, maize is also one of the most nutritious non-legume green fodders. It is a high-energy, low-protein forage commonly used for dairy animals like cows and buffalos, often in combination with a complementary high-protein forage such as alfalfa. Maize is also preferred for silage over other fodders due to its softness, high starch content, and sufficient soluble sugars required for proper ensiling. With a rapid population increase in developing countries like China and India, there is an upsurge in meat consumption and, hence, the requirement for animal feed, which entails high usage of maize. The global maize silage market is projected to grow at a compound annual growth rate of 7.84% from 2021 to 2030. Factors such as increasing demand for sustainable and environment-friendly food sources coupled with rising health awareness are fueling this growth. With the dairy sector growing at about 4%-5% and the increasing shortage faced for fodder, demand for silage maize is expected to increase worldwide. The progress in improved mechanization for the provision of silage maize, reduced labor demand, lack of moisture-related marketing issues as associated with grain maize, early vacancy of farms for next crops, and easy and economical form of feed to sustain household dairy sector make maize silage a profitable venture. However, sustaining the profitability of this enterprise requires the development of hybrids specific for silage production. Little attention has yet been paid to breeding for a plant ideotype for silage with specific consideration of traits such as dry matter yield, nutrient yield, energy in organic matter, genetic architecture of cell wall components determining their digestibility, stalk standability, maturity span, and losses during ensiling. This review explores the available information on the underlying genetic mechanisms and gene/gene families impacting silage yield and quality. The trade-offs between yield and nutritive value in relation to crop duration are also discussed. Based on available genetic information on inheritance and molecular aspects, breeding strategies are proposed to develop maize ideotypes for silage for the development of sustainable animal husbandry.

Symposium review: Integrating the control of energy intake and partitioning into ration formulation

Energy intake and partitioning are determined by many interacting factors and their prediction is the Achilles' heel of ration formulation. Inadequate energy intake can limit milk yield and reproductive performance, whereas excessive energy intake will increase body condition, increasing the risk of health and reproductive issues in the subsequent lactation. Ration composition interacts with the physiological state of cows, making it difficult to predict DMI and the partitioning of energy accurately. However, understanding the factors controlling these allows us to devise grouping strategies and manipulate rations to optimize energy intake through lactation. Eating is controlled by the integration of signals in brain feeding centers. Ration composition affects DMI of cows via signals from ruminal distention and the hepatic oxidation of fuels. Dairy cow rations must contain a minimal concentration of relatively low-energy roughages for proper rumen function, but signals from ruminal distension can limit DMI when the drive to eat is high. Signals from the hepatic oxidation of fuels likely dominate the control of DMI in the peripartum period when cows are in a lipolytic state and later in lactation when signals from distension diminish. Therefore, the effects of the ration on DMI vary with the physiological state of the animal. Furthermore, they interact with environmental stressors such as social (e.g., overcrowding) and thermal stress. The objective of this article is to discuss the effects of ration composition on energy intake and partitioning in lactating cows and how they can be manipulated to optimize productive performance.

Symposium review: Effects of carbohydrate digestion on feed intake and fuel supply

Carbohydrates are the primary energy source for lactating dairy cows, and dairy diets are usually formulated for certain concentrations of forage neutral detergent fiber (NDF) and starch due to their direct effects on dry matter intake and milk production. Forage NDF exerts greater filling effects in the rumen than other dietary components and can limit maximum voluntary feed intake of lactating dairy cows. Since an analytical method for NDF was developed more than a half century ago, it has been used widely to characterize forages and diets for dairy cows. However, because NDF is a chemical measurement varying in its digestibility, in vitro digestibility measurements were developed as a biological approach to assess forage quality. Research efforts over the last several decades led to the development of forage cultivars or hybrids with enhanced in vitro NDF digestibility, such as brown midrib, and management practices considering differences in NDF digestibility of forages. In addition, in vitro NDF digestibility and undigested NDF are commonly measured in commercial labs, and estimated rates of digestion are used in dynamic models in an effort to improve the accuracy and precision of diet formulation. Starch digestion in the rumen also varies among starch sources, being affected by grain type, extent of processing, and conservation method. The site and rate of starch digestion affect dry matter intake and nutrient partitioning in dairy cows by modifying temporal supply of fuel. In addition, dietary starch content and its fermentability can affect digestion rates of starch itself and NDF in the rumen. Previous research has increased our understanding of dietary carbohydrates, but its application for diet formulations requires integrated approaches accounting for factors affecting the filling effects of forage NDF, starch digestion, and temporal fuel supply.

Yield, Nutritional Composition, and Digestibility of Conventional and Brown Midrib (BMR) Pearl Millet as Affected by Planting and Harvesting Dates and Interseeded Cowpea

The objective of this study was to evaluate the yield, nutritional composition, and digestibility of conventional (CON) and brown midrib (BMR) pearl millet (PM) with different establishment dates, maturity at harvest and when mixed with cowpea (CWP). In trial 1, CON and BMR were planted on two different dates. In trial 2, CON and BMR, mixed or not with CWP, were harvested when PM was at the boot or heading stages. In trial 1, dry matter (DM) yield was similar between both PM genotypes but delaying establishment reduced DM yield by 30%. Additionally, BMR had a lower concentration of acid detergent lignin (ADL) and a higher in vitro neutral detergent fiber digestibility (IVNDFD) compared to CON. In Trial 2, the DM yield was 7.3% higher for CON compared to BMR, and PM with the BMR trait had a lower level of ADL and higher IVNDFD compared to CON. Mixing PM with CWP had negligible effects on nutritional composition but reduced DM yield by 8.3%. Results of these studies indicated that fiber from BMR PM is more digestible than CON but, in one of the trials, this occurred at the expense of lower DM yield. Mixing CWP with PM negatively impacted DM yield.

Ruminal Fiber Degradation Kinetics within and among Warm-Season Annual Grasses as Affected by the Brown Midrib Mutation

Simple Summary

Warm-season annual grasses alternative to corn are an attractive option for feeding dairy cattle due to decreased seeding costs and tolerance to drought stress. Warm-season annual grasses include corn, sorghum, and pearl millet. Similar to corn, some varieties of sorghum and pearl millet can contain the brown midrib (BMR) mutation in their genome, which may result in a greater degradability of neutral detergent fiber (NDF). In this study, we evaluated whether forages containing the BMR mutation exhibit the highest NDF digestibility regardless of forage type. For this evaluation, we determined the degradability of NDF by placing forage samples in porous bags within the rumen of lactating dairy cows and measuring how much NDF disappeared over time. Results from this study show that, although forages containing the BMR mutation may show greater NDF degradability than non-BMR forages of the same grass type, forages containing the BMR mutation do not always have the greatest fiber degradability when compared to conventional varieties of other grasses.

Abstract

The objective of this study was to compare the nutritional composition and the neutral detergent fiber (NDF) degradation kinetics of brown midrib (BMR) and non-BMR genotypes within and across warm-season annual grasses. Four commercial varieties (two non-BMR and two BMR) of corn, sorghum, and pearl millet were planted in plots. Forage samples were incubated in the rumen of three rumen-cannulated cows for 0, 3, 6, 12, 24, 48, 96, and 240 h. On an NDF basis, all forage types showed lower acid detergent lignin (ADL) concentrations for BMR genotypes, but the magnitude of the difference differed among forage types. The concentration of undegraded NDF (uNDF; NDF basis) differed among forage types and between genotypes. Corn had the least, pearl millet had the intermediate, and sorghum had the greatest concentration of uNDF. Non-BMR genotypes had greater concentrations of uNDF than BMR genotypes. No interaction existed between forage type and genotype for the concentration of uNDF. In conclusion, although BMR forages may show lower ADL concentrations in the cell wall and greater NDF degradability than non-BMR forages of the same forage type, BMR forages do not always have the least ADL concentration or the greatest NDF degradability when comparing different forage types.

Meta-analysis of rumination behavior and its relationship with milk and milk fat production, rumen pH, and total-tract digestibility in lactating dairy cows

Time spent ruminating is affected by diet and affects the rumen environment. The objective of the current study was to conduct a meta-regression to characterize the variation in rumination time and its relationship with milk and milk fat yields and variables mechanistically associated with milk fat synthesis, including rumen pH and total-tract digestibility. The analysis included 130 journal articles published between 1986 and 2018 that reported 479 treatment means from lactating Holsteins cows during established lactation. Milk yield averaged 34.3 kg/d (range 14.2-52.1 kg/d), milk fat averaged 3.47% (range 2.20-4.60%), and rumen pH averaged 6.1 (range 5.3-7.0). Rumination observation systems were categorized into 6 groups, but there was little difference in average rumination time among systems. The total time spent ruminating averaged 444 min/d (range 151-638 d) and occurred in 13.8 bouts/d (range 7.8-17.4 bouts/d) that averaged 32.7 min (range 20.0-48.1 min). Bivariate regressions were modeled to include the random effect of study, and correlations were evaluated through the partial R² that excluded variation accounted for by the random effect. Rumination time was quadratically increased with increasing milk fat yield (partial R² = 0.27) and milk fat percent (partial R² = 0.17). Rumination was also increased with increasing milk yield, dry matter intake, and rumen pH, and was quadratically related to dietary neutral detergent fiber (NDF) and total-tract NDF digestibility (partial R² = 0.10-0.27). Similar relationships were observed for rumination per unit of dry matter and NDF intake. The best-fit multivariate model predicting total rumination time included milk yield, milk fat yield, and concentration and accounted for 37% of the variation. Total-tract digestibility was available for 217 treatment means; when included in the model, the partial R² increased to 0.41. Last, principal component analysis was conducted to explore the relationship among variables. The first 2 principal components in the broad analyses explained 36.7% of the 39 variables evaluated, which included rumination bouts and time spent ruminating. In conclusion, rumination time was related to milk fat across a large number of studies, although it explained only a limited amount of the variation in milk fat.

Thiamine modulates intestinal morphological structure and microbiota under subacute ruminal acidosis induced by a high-concentrate diet in Saanen goats

Ruminant animals are generally fed with starch-rich grain as the main energy source, and the incidence of metabolic diseases such as subacute ruminal acidosis (SARA) is high due to the intensive farming. Thiamin has been reported to alleviate SARA caused by high-concentrate diets, but the exact mechanism is not well understood. The goal of this study was to examine the role of thiamine in intestinal inflammation and microbiota caused by high-concentrate diets. The SARA model was induced by low neutral detergent fibre/starch ration to study the effects of thiamine on intestinal tissue structure and microbiota. 18 mid-lactation (148 ± 3 d in milk; milk yield = 0.71 ± 0.0300 kg/d) Saanen goats (BW = 36.5 ± 1.99 kg; body condition score = 2.73 ± 0.16, where 1 = emaciated and 6 = obese) in parities 1 or 2 were selected. The goats were randomly divided into three groups with six replicates: (1) control diet (C; concentrate:forage 30:70), (2) high-concentrate diet (H; concentrate:forage 70:30), and (3) high-concentrate diet with 200 mg of thiamine/kg of DM intake (H + T;concentrate:forage 70:30). The experimental period was lasted for 56 d. The small and large intestine, expression of inflammatory factor genes, tight junction protein genes, total antioxidant capacity, and intestinal microbiota were measured. The results showed that SARA was observed in treatment H, whereas rumen fluid pH was improved in treatment H + T. Treatment H + T also significantly repaired the intestinal tissue structure damaged by SARA, improved the total antioxidant capacity of the small intestinal mucosa, reduced mRNA expression of inflammatory factors in the small intestine tissue, and increased the mRNA expression of tight junction genes in small intestine tissue. The high-concentrate diet reduced the diversity of intestinal microbiota. When thiamine is added to the high-concentrate diet, the relative abundance of intestinal Firmicutes and beneficial bacteria represented by Lactobacilli were upregulated, and the relative abundance of Proteus, a marker of intestinal dysbacteriosis, returned to normal. In conclusion, thiamine supplementation could alleviate the damage to the intestinal tissue structure and microbial environment caused by SARA condition in dairy goats fed a high-concentrate diet.

Effects of ecotrofin™ on milk yield, milk quality and serum biochemistry in lactating goats

A nutritional supplement (Ecotrofin™, by Vetoquinol Italia S.r.l) recommended in ruminants feeding to strengthen the physiological condition and improve digestive performance was tested in 20 pluriparae grazing goats divided in two groups (control and treated) to assess its possible effects on milk yield and quality and to assess eventual adverse effects. Animals from both groups also received 400 g/day of corn meal, and the treated group was supplemented with 20 g/head/day of the nutritional supplement. At the doses suggested by the manufacturer, despite a transient increase after 30 days of supplementation, Ecotrofin™ did not show significant effects on milk yield and, although some changes were found in the fatty acids profile, no significant improvement of MUFA and PUFA, as well as of omega‐6:omega‐3 ratio and CLA content were seen. Therefore, in our experimental conditions the supplementation of diet with Ecotrofin™ did not appear useful to improve goat's performance. A significant effect on kidney health markers (27 vs. 22.5 for urea and 0.83 vs. 0.76 for creatinine, p < 0.05) suggested a beneficial effect on renal function but, since levels fell in the normal ranges in both groups, such hypothesis would need further studies to be addressed.

A mixed-linkage (1,3;1,4)-β-D-glucan specific hydrolase mediates dark-triggered degradation of this plant cell wall polysaccharide

The presence of mixed-linkage (1,3;1,4)-β-d-glucan (MLG) in plant cell walls is a key feature of grass species such as cereals, the main source of calorie intake for humans and cattle. Accumulation of this polysaccharide involves the coordinated regulation of biosynthetic and metabolic machineries. While several components of the MLG biosynthesis machinery have been identified in diverse plant species, degradation of MLG is poorly understood. In this study, we performed a large-scale forward genetic screen for maize (Zea mays) mutants with altered cell wall polysaccharide structural properties. As a result, we identified a maize mutant with increased MLG content in several tissues, including adult leaves and senesced organs, where only trace amounts of MLG are usually detected. The causative mutation was found in the GRMZM2G137535 gene, encoding a GH17 licheninase as demonstrated by an in vitro activity assay of the heterologously expressed protein. In addition, maize plants overexpressing GRMZM2G137535 exhibit a 90% reduction in MLG content, indicating that the protein is not only required, but its expression is sufficient to degrade MLG. Accordingly, the mutant was named MLG hydrolase 1 (mlgh1). mlgh1 plants show increased saccharification yields upon enzymatic digestion. Stacking mlgh1 with lignin-deficient mutations results in synergistic increases in saccharification. Time profiling experiments indicate that wall MLG content is modulated during day/night cycles, inversely associated with MLGH1 transcript accumulation. This cycling is absent in the mlgh1 mutant, suggesting that the mechanism involved requires MLG degradation, which may in turn regulate MLGH1 gene expression.

Effects of varying proportions of corn grain to barley grain in corn silage-based diet on feed sorting behaviour and productivity of dairy cows

Context Although several studies investigated the dairy cow performance in response to varying ratios of corn to barley grain, little attention has been paid to the forage component of the diet. We hypothesised that a diet based on corn silage with coarse particles might promote chewing and saliva secretion, neutralising acids produced during excess fermentation of high-barley diet and, thus, improve dairy cow productivity. Aims Feed sorting behaviour, nutrient digestibility, rumen fermentation, and milk production were recorded in Holstein cows offered a corn silage-based diet in which corn grain was incrementally substituted with barley grain. Methods Eight multiparous cows, averaging 189 ± 24 days in milk, 577 ± 47 kg bodyweight and 33 ± 5 kg/day milk yield, were distributed according to two 4 × 4 Latin squares. Four total mixed rations were designed, differing in corn to barley ratios as follows: (1) 100:0, (2) 67:33, (3) 33:67 and (4) 0:100. Corn silage and alfalfa hay constituted 31.0% and 9.0% of diet DM respectively. Key results Although no treatment difference existed on sorting of long, medium or fine particles, the extent of sorting for 1.18-mm particles tended to increase linearly as corn to barley ratio decreased. The ruminal pH declined linearly from 5.90 to 5.60 as the barley grain proportion increased from 0 to 100. Acetate to propionate ratio decreased linearly (P &lt; 0.01) as the barley grain proportion increased. No differences were seen in feed consumption and organic matter, crude protein, neutral detergent fibre and fat digestion in total tract. However, non-fibre carbohydrate digestibility tended to increase linearly (P = 0.07) as the ratio of corn to barley grain decreased. Time spent eating, ruminating and chewing remained largely unaffected by treatment. Treatments had no effect on fat-corrected milk production and milk composition, with the exception that actual milk production tended to increase linearly as the corn to barley ratio decreased. Feed efficiency (milk production/DM intake (DMI)) increased linearly from 1.22 to 1.32 as the barley grain proportion increased from 0 to 100. Conclusions Although the differences in feeding behaviour, DMI, and milk production and composition were negligible among experimental diets, cows consuming a corn silage-based diet with incremental substitution of corn grain with barley grain produced more milk per kilogram of DMI. Implications Increased proportion of barley grain in replacement of corn grain in corn silage-based diet might be advised as it increased the efficiency of feed conversion to milk.

Influence of fiber degradability of corn silage in diets with lower and higher fiber content on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows

The effect of neutral detergent fiber (NDF) degradability of corn silage in diets containing lower and higher NDF concentrations on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows was measured. Eight ruminally cannulated Holstein cows averaging 91 ± 4 (standard error) days in milk were used in a replicated 4 × 4 Latin square design with 21-d periods (7-d collection periods). Dietary treatments were formulated to contain either conventional (CON; 48.6% 24-h NDF degradability; NDFD) or brown midrib-3 (BM3; 61.1% 24-h NDFD) corn silage and either lower NDF (LNDF) or higher NDF (HNDF) concentration (32.0 and 35.8% of ration dry matter, DM) by adjusting the dietary forage content (52 and 67% forage, DM basis). The dietary treatments were (1) CON-LNDF, (2) CON-HNDF, (3) BM3-LNDF, and (4) BM3-HNDF. Data were analyzed as a factorial arrangement of diets within a replicated Latin square design with the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with fixed effects of NDFD, NDF, NDFD × NDF, period(square), and square. Cow within square was the random effect. Time and its interactions with NDFD and NDF were included in the model when appropriate. An interaction between NDFD and NDF content resulted in the HNDF diet decreasing dry matter intake (DMI) with CON corn silage but not with BM3 silage. Cows fed the BM3 corn silage had higher DMI than cows fed the CON corn silage, whereas cows fed the HNDF diet consumed less DM than cows fed the LNDF diet. Cows fed the BM3 diets had greater energy-corrected milk yield, higher milk true protein content, and lower milk urea nitrogen concentration than cows fed CON diets. Additionally, cows fed the BM3 diets had greater total-tract digestibility of organic matter and NDF than cows fed the CON diets. Compared with CON diets, the BMR diets accelerated ruminal NDF turnover. When incorporated into higher NDF diets, corn silage with greater in vitro 24-h NDFD and lower undegradable NDF at 240 h of in vitro fermentation (uNDF240) allowed for greater DMI intake than CON. In contrast, for lower NDF diets, NDFD of corn silage did not affect DMI, which suggests that a threshold level of inclusion of higher NDFD corn silage is necessary to observe enhanced lactational performance. Results suggest that there is a maximum gut fill of dietary uNDF240 and that higher NDFD corn silage can be fed at greater dietary concentrations.

Evaluation of source of corn silage and trace minerals on rumen characteristics and passage rate of Holstein cows

The effects of source of corn silage and trace mineral on rumen fermentation, turnover, and particle passage rates were evaluated with 8 ruminally cannulated Holstein cows averaging 83 (standard error = 5) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments and 28-d periods. The diets consisted (dry basis) of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) source of Cu, Zn, and Mn trace minerals. The targeted supplemental amount of Cu, Zn, and Mn was 194, 1,657, and 687 mg/d, respectively. The dietary treatments were (1) CON-STM, (2) CON-HTM, (3) BM3-STM, and (4) BM3-HTM. Dietary nutrient composition of BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h of in vitro fermentation (uNDF240om; % of dry matter), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of dry matter). Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace mineral, corn silage and trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS (version 9.4, SAS Institute Inc., Cary, NC). Cow within replicate was a random effect. Daily mean, standard deviation, minimum, and maximum for rumen pH were unaffected by corn silage or trace mineral source. Cows fed the CON diets had greater rumen acetate percentage than cows fed the BM3 diets (65.7 vs. 64.7 molar %). In contrast, cows fed the BM3 diets had greater rumen propionate percentage than cows fed the CON diets (21.4 vs. 20.4 molar %). Total volatile fatty acid concentration was lower for cows fed STM versus HTM in BM3 diets, but not for the cows fed the CON diets. Cows fed the BM3 diets had faster turnover rate and shorter turnover time for uNDF240om than cows fed the CON diets (3.12 vs. 2.86%/h and 33.3 vs. 36.5 h, respectively). Cows fed the BM3 diets had a faster passage rate of small and medium corn silage neutral detergent fiber particles than cows fed the CON diets (5.73 vs. 5.37%/h and 4.74 vs. 4.31%/h, respectively). We observed a corn silage by source of trace mineral interaction on organic matter and uNDF240om rumen pool size and organic matter turnover. Overall, source of corn silage had a pronounced influence on rumen dynamics presumably related to greater in vitro neutral detergent fiber digestibility and lower uNDF240om content of BM3 corn silage that allowed for faster turnover of indigestible neutral detergent fiber and greater passage rate of corn silage particles. In contrast, the source of trace mineral had much less significant effects on rumen fermentation, turnover, and particle passage rates. Corn silage-based diets intended to enhance rumen fiber fermentation, turnover, and passage are more affected by source and digestibility of neutral detergent fiber than source of dietary trace minerals.

Quantifying non-fibrous carbohydrates, acid detergent fiber and cellulose of forage through an in vitro gas production technique

BACKGROUND

The in vitro gas production (GP) technique has been useful for evaluating the potential degradability of feedstuffs in ruminal environments; GP is related to the components of feedstuff ingredients.

RESULTS

Linear models were generated and validated as alternatives of quantifying neutral detergent-soluble fiber, starch (St)/hemicellulose (Hem) and cellulose (Cel) through GP. Residuals of models obtained from the peaks of GP [0-8 h (GP-8), > 8-24 h (GP-24), > 24-48 h (GP-48) and > 24-81 h (GP-81)] of 0.02, 0.04, 0.08, 0.12 and 0.20 g of glucose (Glu), St and Cel respectively. The incubations were analyzed in mixtures of Glu, St and Cel. The best fitting models (r² from 0.709 to 0.935) were tested on corn stover (CS) to quantify rapid fermentation fractions (RF; equivalent to Glu), medium fermentation fractions (MF; equivalent to St) and low fermentation fractions (LF48; equivalent to Cel); in CS, RF, MF and LF models had standardized residuals < 0.09. The analysis with Leucaena (Leucaena leucocephala Lam. de Wit) and star grass (Cynodon nlemfuensis Vanderyst) consider high-protein ingredients.

CONCLUSION

The in vitro GP of RF, MF and LF48 fractions equivalent to Glu, St and Cel are affected by maturity and harvest time even when the chemical composition remains similar, and so RF, MF and LF48 should be considered during the design of ruminant diets. In vitro GP could be used to quantify the components of some forages, although further studies are necessary. © 2020 Society of Chemical Industry.

Lactational response of early-lactation Holstein cows fed starch or floury corn silage

The study objective was to evaluate the lactational performance of early-lactation dairy cows fed a total mixed ration (TMR) based on corn silage produced from a standard starch hybrid compared with 2 floury starch hybrids. Twenty-one (6 primiparous and 21 multiparous) high-producing, early-lactation Holstein cows were blocked by calving date and parity and randomly assigned to 1 of 3 experimental corn silages from wk 4 through wk 12 postpartum using a randomized complete block design with wk 3 as a covariate. The Dekalb blend (STA; Monsanto Company, St. Louis, MO), Masters Choice 527 (LF₁; Masters Choice, Anna, IL), and Masters Choice 5250 (LF₂) treatments were planted and harvested as corn silage using a kernel processor silage harvester, inoculated, and ensiled in individual Ag-Bags (Ag-Bag, St. Nazianz, WI). The TMR were formulated to be isonitrogenous at 17.5% crude protein consisting of 15.9% alfalfa hay, 35.1% concentrate mix, and 48% of the respective experimental corn silage on a dry matter basis. Crude protein content of STA and LF₂ was lower than LF₁ corn silage. Starch content was higher for STA compared with LF₁ and LF₂ silage. The TMR digestible fiber (neutral detergent fiber) concentration was lower for STA than LF₁ and LF₂ (14.0, 15.5, and 17.9% dry matter for STA, LF₁, and LF₂, respectively). Growing crop year affected corn silage vomitoxin (0.60, 1.45, and 1.56 mg/kg) concentrations, which may have affected lactational performance as STA corn silage was from 2013, whereas LF₁ and LF₂ were from the 2012 crop year. Dry matter intake (22.9, 23.5, and 22.4 kg/d), milk yield (35.6, 34.8, and 36.1 kg/d), 3.5% fat-corrected milk yield (38.7, 36.5, and 37.6 kg/d), energy-corrected milk yield (38.2, 36.1, and 38.1 kg/d), feed efficiency (1.79, 1.61, and 1.67 kg/kg; 3.5% fat-corrected milk/dry matter intake), milk fat (4.17, 3.94, and 3.71%), milk protein (3.12, 3.09, and 3.03%), lactose (4.93, 4.92, and 4.92%), solids-not-fat (8.96, 8.92, and 8.85%), body weight change (-0.10, -0.06, and -0.08 kg/d), and body condition score change (-0.05, -0.04, and -0.05 score/d) were similar for early-lactation dairy cows fed all corn silage hybrids. Lower ruminal pH and acetate along with higher propionate molar percentages were reported for cows fed STA compared with cows fed LF₁ and LF₂. Early-lactation dairy cows fed a corn silage with lower starch and higher digestible fiber concentrations resulted in similar milk production compared with cows fed higher starch and lower digestible fiber concentrations.

Evaluation of source of corn silage and trace minerals on lactational performance and total-tract nutrient digestibility in Holstein cows

We evaluated the effects of source of corn silage and trace minerals on lactational performance and total-tract digestibility (TTD) of nutrients in 16 Holstein cows averaging 82 (standard error = 3) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments with 28-d periods. The diets consisted [dry matter (DM) basis] of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) sources of copper, manganese, and zinc trace minerals. The targeted supplemental concentrations of copper, zinc, and manganese were 194, 1,657, and 687 mg/d, respectively. The dietary treatments were CON-STM, CON-HTM, BM3-STM, and BM3-HTM. The dietary nutrient composition of the BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h (uNDF240om; % of DM), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of DM). The average supplemental concentrations of copper, zinc, and manganese for the STM diets were 10, 41, and 64 mg/kg, respectively, and the average supplemental concentrations of copper, zinc, and manganese for the HTM diets were 10, 40, and 62 mg/kg, respectively. The average total dietary concentrations of copper, zinc, and manganese for the STM diets were 17, 104, and 60 mg/kg, respectively, and the average total dietary concentrations of copper, zinc, and manganese for the HTM diets were 17, 91, and 66 mg/kg, respectively. Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace minerals, corn silage × trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS. Cow within replicated square was a random effect. Cows fed the BM3 diets had greater dry matter intake (DMI) and milk yield (28.1 and 47.0 kg/d) than cows fed the CON diets (27.5 and 44.7 kg/d). We found no significant interaction between corn silage and trace minerals for DMI and milk yield. Cows fed the HTM diets (28.1 kg/d) had a greater DMI than cows fed the STM diets (27.5 kg/d). Cows fed the BM3 diets had greater TTD of DM and OM (72.8 and 74.1% of DM) than cows fed the CON diets (71.1 and 72.3% of DM). Cows fed the HTM diets had a tendency for greater TTD of aNDFom than cows fed the STM diets (56.8 vs. 54.9% of DM). Cows fed the CON diets ruminated longer during the day than cows fed the BM3 diets (524 vs. 496 min/d). Corn silage with greater NDF digestibility and lower uNDF240om enhanced DMI, milk yield, and TTD of DM and OM, and hydroxy trace minerals improved DMI and tended to improve TTD of aNDFom. The source of corn silage and trace minerals should be taken into consideration when formulating diets for high-producing dairy cows.

Relationships between chemical composition and in vitro gas production parameters of maize leaves and stems

This study investigated the chemical composition (proximate and Van Soest analysis) and in vitro gas production parameters of maize leaves and stems separately, and related the in vitro gas production parameters with the chemical composition, of thirteen maize cultivars. After harvest in September 2016, all plants were separated into two morphological fractions: leaves and stems. The crude protein (CP) content was greater, and the ratio of acid detergent lignin (ADL) to potentially rumen degradable fibre (calculated as the difference between neutral detergent fibre and ADL; ADL:pRDF) was lower in the leaves than in the stems in all 13 cultivars. For the leaves, the cumulative gas production between 3 and 20 hr (A2), representing cell wall fermentation in the rumen fluid, and the cumulative 72‐hr gas production (GP72), representing total organic matter (OM) degradation, were moderately to weakly correlated with the chemical composition, including hemicellulose, cellulose, ADL and CP content (R² < 0.40), whilst the best relationship between the half‐time value (B2), representing the rate of cell wall degradation, and chemical composition had an R² of 0.63. For the stems, the best relationship between A2, B2 and GP72 with chemical composition was greater (R² ≥ 0.74) and the best relationship included hemicellulose (A2 only), cellulose and ADL (GP72 and A2 only) contents. In conclusion, maize leaves and stems differed in chemical composition, in particular CP content and ADL:pRDF. The A2 and GP72 of the stems, but not of the leaves, were highly correlated with the chemical composition, indicating that the cell wall and OM degradation of maize stems can be better predicted by its chemical composition.

Effects of ruminal degradability of ensiled whole crop maize varieties on feed intake and milk production of dairy cows

The feed value of whole crop maize silage (WCMS) depends on nutrient composition, ruminal degradability and whole tract digestibility. However, as the ruminal degradation rate is involved in physical regulation of feed intake, ruminal degradability of WCMS may also affect feed intake and milk production of dairy cows. Thus, the aim of this study was to examine relationships between nutrient composition, ruminal degradability, and whole tract digestibility of WCMS and feed intake and milk production of dairy cows. Nine varieties were tested in 3 consecutive years. Nutrient composition analyses included proximate analysis and determination of cell wall constituents. Whole tract digestibility was determined in vivo using wethers and ruminal degradability was examined in situ using four rumen-fistulated steers. Feed intake and milk production were measured using nine cows per variety. Cows were fed a ration consisting of 75.0% WCMS, 8.5% hay and 16.5% soya bean meal (dry matter basis) ad libitum. Variety did not influence nutrient composition, except for the concentration of ADF (ADFom), ADL and utilisable CP (uCP). In contrast, variety had a significant effect (P < 0.05) on ruminal degradability of NDF (aNDFom) and on whole tract digestibility of organic matter (OM) and non-fibre carbohydrates. Dry matter intake (DMI) of WCMS tended to be affected by variety (0.05

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Key Words

• feed intake regulation
• feed value
• nutrient composition
• whole crop maize silage
• whole tract digestibility

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MESH Headings

• Animals
• Cattle/physiology
• Dairying
• Diet/veterinary
• Digestion
• Eating
• Female
• Lactation
• Milk/metabolism
• Rumen/metabolism
• Silage/analysis
• Glycine max
• Zea mays

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Affiliation(s)

G Terler Institute of Livestock Research, Agricultural Research and Education Centre Raumberg-Gumpenstein, Raumberg 38, 8952 Irdning-Donnersbachtal, Austria Division of Livestock Sciences, Department of Sustainable Agricultural Systems, University of Natural Resources and Life Sciences, Gregor Mendel-Straße 33, 1180 Vienna, Austria
L Gruber Institute of Livestock Research, Agricultural Research and Education Centre Raumberg-Gumpenstein, Raumberg 38, 8952 Irdning-Donnersbachtal, Austria
W Knaus Division of Livestock Sciences, Department of Sustainable Agricultural Systems, University of Natural Resources and Life Sciences, Gregor Mendel-Straße 33, 1180 Vienna, Austria

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Equation to predict feed intake response by lactating cows to factors related to the filling effect of rations

Our objective was to predict the dry matter intake (DMI) response during ration formulation to factors related to the filling effect of rations and their interaction with milk yield (MY) by lactating cows past peak lactation. A data set was developed consisting of 134 treatment means from 34 experiments reported in 32 peer-reviewed articles published from 1990 through 2015. The data set included data for cows ranging from 60 to 309 d postpartum with mean DMI ranging from 17.6 to 30.6 kg/d and MY ranging from 20.3 to 51.1 kg/d. Ration composition among treatments ranged from 12.7 to 21.8% of dry matter (DM) for crude protein, 11.5 to 31.0% of DM for acid detergent fiber (ADF), 25.5 to 48.2% of DM for neutral detergent fiber (NDF), 9.9 to 39.3% of DM for forage NDF (FNDF), and 0.45 to 0.84 for the ratio of ADF% to NDF% (ADF/NDF). Laboratory measures of digestibility of NDF (in vitro or in situ, FNDFD) for the sole or major forage ranged from 24.1 to 72.7%. The model included the random effect of study to account for various experiment-specific effects including different methods of measurement of NDF and FNDFD among studies. The full model also included linear and quadratic effects of crude protein, ADF, NDF, FNDF, ADF/NDF, and FNDFD, as well as their linear and quadratic interactions, and mean MY for each study and its interaction with ration factors. The proposed prediction equation is DMI (kg/d) = 12.0 - 0.107 × FNDF + 8.17 × ADF/NDF + 0.0253 × FNDFD - 0.328 × (ADF/NDF - 0.602) × (FNDFD - 48.3) + 0.225 × MY + 0.00390 × (FNDFD - 48.3) × (MY - 33.1) with mean bias = 0.00 kg/d, root mean square error = 1.55 kg/d, and concordance correlation coefficient = 0.827. Dry matter intake was positively related to MY and ADF/NDF and negatively related to FNDF, and FNDFD was positively related to DMI for cows with high MY but negatively related to MY for cows with low MY. In addition, DMI was positively related to FNDFD for low ADF/NDF but negatively related to FNDFD for high ADF/NDF. The ADF/NDF was included to represent differences in forage fragility between grasses and legumes. The proposed model was compared with the equation recommended by the National Research Council (2001) that was developed using only animal factors by fitting each equation to a subset of the data set that included the required inputs for both. The National Research Council (2001) equation without diet factors had a higher root mean square error and over-predicted DMI at high DMI and under-predicted DMI at low DMI. Our proposed equation should be useful to predict DMI response to factors related to the filling effects of rations during ration formulation.

Altering undigested neutral detergent fiber through additives applied in corn, whole barley crop, and alfalfa silages, and its effect on performance of lactating Holstein dairy cows

OBJECTIVE

We hypothesized that silage additives may alter the undigested neutral detergent fiber (uNDF) content through ensiling. Therefore, urea and formic acid were applied to corn, whole barley crop (WBC) and alfalfa to change uNDF content of the ensiled forages.

METHODS

Six experimental diets at two groups of high uNDF (untreated corn and alfalfa silages [CSAS] and untreated whole barley and alfalfa silages [BSAS]) and low uNDF (urea-treated corn silage+untreated alfalfa silage [CSUAS], urea-treated whole barley silage+untreated alfalfa silage [BSUAS], untreated corn silage+formic acid-treated alfalfa silage [CSASF], and untreated whole barley silage+formic acid-treated alfalfa silage [BSASF]), were allocated to thirty-six multiparous lactating Holstein dairy cows.

RESULTS

The untreated silages were higher in uNDF than additive treated silages, but the uNDF concentrations among silages were variable (corn silage0.05). Milk yield tended to increase in the cows fed high uNDF diets than those fed low uNDF (p = 0.10). The cows fed diet based on urea-treated corn silage had higher milk yield than those fed other silages (p = 0.05). The substitution of corn silage with the WBC silage tended to decrease milk production (p = 0.07). Changing the physical source of NDF supply and the uNDF content from the corn silage to the WBC silage caused a significant increase in ruminal NH3-N concentration, milk urea-N and fat yield (p< 0.05). The cows fed diets based on WBC silage experienced greater rumination time than the cows fed corn silage (p<0.05).

CONCLUSION

Administering additives to silages to reduce uNDF may improve the performance of Holstein dairy cows.

Production performance, nutrient digestibility, and milk fatty acid profile of lactating dairy cows fed corn silage- or sorghum silage-based diets with and without xylanase supplementation

The objective of this study was to evaluate the effects of supplementing xylanase on production performance, nutrient digestibility, and milk fatty acid profile in high-producing dairy cows consuming corn silage- or sorghum silage-based diets. Conventional corn (80,000 seeds/ha) and brown midrib forage sorghum (250,000 seeds/ha) were planted, harvested [34 and 32% of dry matter (DM), respectively], and ensiled for more than 10 mo. Four primiparous and 20 multiparous Holstein cows were randomly assigned to 1 of 4 diets in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments and 19-d periods. Treatment diets consisted of (1) corn silage-based diet without xylanase, (2) corn silage-based diet with xylanase, (3) sorghum silage-based diet without xylanase, and (4) sorghum silage-based diet with xylanase. The xylanase product was supplemented at a rate of 1.5 g of product/kg of total DM. Corn silage had higher concentrations of starch (31.2 vs. 29.2%), slightly higher concentrations of crude protein (7.1 vs. 6.8%) and fat (3.7 vs. 3.2%), and lower concentrations of neutral detergent fiber (36.4 vs. 49.0%) and lignin (2.1 vs. 5.7%) than sorghum silage. Xylanase supplementation did not affect DM intake, milk yield, milk fat percentage and yield, milk protein percentage and yield, lactose percentage and yield, and 3.5% fat-corrected milk yield. Cows consuming corn silage-based diets consumed 13% more DM (28.8 vs. 25.5 kg/d) and produced 5% more milk (51.6 vs. 48.9 kg/d) than cows consuming sorghum silage-based diets. Milk from cows consuming sorghum silage-based diets had 16% greater fat concentrations (3.84 and 3.30%) than milk from cows consuming corn silage-based diets. This resulted in 8% greater fat yields (1.81 vs. 1.68 kg/d). Silage type did not affect milk protein and lactose concentrations. Xylanase supplementation did not affect nutrient digestibility. Cows consuming corn silage-based diets showed greater DM (77.3 vs. 73.5%), crude protein (78.0 vs. 72.4), and starch (99.2 vs. 96.5%) digestibilities than cows consuming sorghum silage-based diets. In conclusion, xylanase supplementation did not improve production performance when high-producing dairy cows were fed corn silage- or sorghum silage-based diets. In addition, production performance can be sustained by feeding sorghum silage in replacement of corn silage.

Brown-midrib corn silage in finishing steer diet: effects on animal performance, in vivo digestibility and ruminal kinetics disappearance

Lower lignin content in brown-midrib corn silage (BMRCS) than in conventional corn silage results in greater digestibility and dry-matter intake. Despite this advantage, the use of BMRCS has not been widely evaluated in beef cattle. The aim of the present study was to determine the effects of BMRCS chopped at 22-mm as the main component (79% DM basis) for finishing steer diet on digestion, animal performance and ruminal kinetics disappearance. In a first trial, 56 Angus and crossbred steers (339 ± 18 kg initial bodyweight) were divided into 14 pens that were randomly assigned to one of the following two treatments: BMR total mixed ration (BMRT) or conventional total mixed ration. Data were analysed under a completely randomised design using pen as the experimental unit (n = 7). In a second trial, BMRCS and conventional corn silage were incubated (0, 3, 6, 12, 24, 36, 72 and 120 h) in the rumen of three ruminally cannulated cows. Data were analysed under a completely randomised block (cow) design. The inclusion of BMRCS in 79% corn silage diet for finishing steers improved total diet neutral detergent fibre and acid detergent fibre digestibility, but did not improve DM digestibility. While there was no significant improvement in animal performance, carcass yield was improved in BMRT. Future studies are needed to evaluate the improvement of carcass weight in steers fed BMRT.

Methane production, ruminal fermentation characteristics, nutrient digestibility, nitrogen excretion, and milk production of dairy cows fed conventional or brown midrib corn silage

The objective of this study was to examine the effect of replacing conventional corn silage (CCS) with brown midrib corn silage (BMCS) in dairy cow diets on enteric CH₄ emission, nutrient intake, digestibility, ruminal fermentation characteristics, milk production, and N excretion. Sixteen rumen-cannulated lactating cows used in a crossover design (35-d periods) were fed (ad libitum) a total mixed ration (forage:concentrate ratio = 65:35, dry matter basis) based (59% dry matter) on either CCS or BMCS. Dry matter intake and milk yield increased when cows were fed BMCS instead of CCS. Of the milk components, only milk fat content slightly decreased when cows were fed the BMCS-based diet compared with when fed the CCS-based diet (3.81 vs. 3.92%). Compared with CCS, feeding BMCS to cows increased yields of milk protein and milk fat. Ruminal pH, protozoa numbers, total VFA concentration, and molar proportions of acetate and propionate were similar between cows fed BMCS and those fed CCS. Daily enteric CH₄ emission (g/d) was unaffected by dietary treatments, but CH₄ production expressed as a proportion of gross energy intake or on milk yield basis was lower for cows fed the BMCS-based diet than for cows fed the CCS-based diet. A decline in manure N excretion and a shift in N excretion from urine to feces were observed when BMCS replaced CCS in the diet, suggesting reduced potential of manure N volatilization. Results from this study show that improving fiber quality of corn silage in dairy cow diets through using brown midrib trait cultivar can reduce enteric CH₄ emissions as well as potential emissions of NH₃ and N₂O from manure. However, CH₄ emissions during manure storage may increase due to excretion of degradable OM when BMCS diet is fed, which merits further investigation.

A nutritional evaluation of common barley varieties grown for silage by beef and dairy producers in western Canada

This study evaluated the nutritional and neutral detergent fiber digestibility (NDFD) characteristics of seven barley varieties (‘Conlon’, ‘CDC Copeland’, ‘CDC Cowboy’, ‘Falcon’, ‘Legacy’, ‘AC Metcalfe’, and ‘Xena’) grown for silage. Commercial samples (n = 80) harvested at the mid-dough stage were collected over 2 years (2012 and 2013). Average pH and dry matter (DM) content were 4.05% ± 0.17% and 36.8% ± 4.1%, respectively. ‘Falcon’ and ‘AC Metcalfe’ had higher (P < 0.05) CP relative to ‘CDC Copeland’ and ‘Xena’, with intermediate values for the other varieties. Acid (ADF) and neutral (NDF) detergent fiber contents were higher (P < 0.05) for ‘CDC Cowboy’ relative to ‘Conlon’. Starch was higher (P < 0.05) for ‘Legacy’ and ‘Conlon’ than ‘CDC Cowboy’, with intermediate values for other varieties. Legacy had a greater (P < 0.05) 6-h NDFD while ‘CDC Cowboy’ had a greater (P < 0.05) 30-h NDFD. Indigestible NDF (INDF; % NDF) was greater (P < 0.05) for ‘AC Metcalfe’ relative to ‘CDC Cowboy’ and ‘Falcon’. These results indicate that barley varieties vary with respect to chemical composition and NDFD and INDF contents. Selection for higher 30-h NDFD could result in improvements in DM and DE intake and performance of growing beef cattle.

Replacing conventional with brown midrib corn silage in a total mixed ration: the impact on early and late lactation dairy cow intake, milk yield and composition, and milk fatty acids profile

Brown midrib corn silage (BMRS) is used as an alternative to conventional corn silage (CS) to increase milk yield because of its higher neutral detergent fibre digestibility (NDFD) and DM intake (DMI). Forty Holstein dairy cows were used in a completely randomised design with a 2 × 2 factorial arrangement. Two groups of 13 cows in early lactation (EL) and 7 in late lactation (LL) were fed with a total mixed ration including brown midrib (BMR) or conventional corn silage (C), for a period of 42 days. The cows were milked twice a day, milk yield and DMI were recorded, and NDFD was estimated. Milk composition was measured twice a week and milk fatty acid profile was quantified on the final week of the experiment. In EL, BMR diet increased DMI, NDFD, milk and protein yield whereas milk fat content and yield were decreased. Concentrations of trans-10 C18:1 and trans-10, cis-12 C18:2 in milk were higher in BMR. In LL cows DMI was similar between BMR and C whereas milk and fat yields tended to be higher in C. Fat-corrected milk yield was greater in the C diet. The effect of the BMRS on DMI and milk yield depended on stage of lactation, justifying its use in early lactation. The lower milk fat concentration, observed when BMRS was included in the diets, could be explained in part by an increased concentration of trans-10 C18:1 and trans-10, cis-12 C18:2.

Feeding a brown midrib corn silage-based diet to growing beef steers improves growth performance and economic returns

Saunders, C. S., Yang, S. Y., Eun, J.-S., Feuz, D. M. and ZoBell, D. R. 2015. Feeding a brown midrib corn silage-based diet to growing beef steers improves growth performance and economic returns. Can. J. Anim. Sci. 95: 625–631. A feedlot experiment was performed to determine growth performance, ruminal fermentation characteristics, and economic returns for growing beef steers when fed a brown midrib corn silage-based total mixed ration (BMRT) compared with a conventional corn silage-based total mixed ration (CCST). Twenty-four Angus crossbred steers (initial body weight=258±23.2 kg) in individual pens were used in a completely randomized design (n=12). Intake of dry matter was not different between the treatments. Steers fed the BMRT tended to have greater average daily gain (1.54 vs. 1.42 kg d−1; P=0.09) and gain-to-feed ratio (0.165 vs. 0.146; P=0.07) compared with those fed the CCST. Feeding the BMRT increased total volatile fatty acid (VFA) concentration (P=0.01) compared with the CCST, while it decreased molar proportion of acetate (P<0.01), and increased propionate proportion (P=0.01), resulting in decreased acetate-to-propionate ratio compared with the CCST (P<0.01). Steers fed the BMRT increased feed margin (P=0.05) and net return (P=0.02) compared with those fed the CCST throughout the trial. Overall results of this study indicate that feeding the BMRT to growing beef steers enhanced ruminal fermentation and beneficially shifted VFA profiles, which contributed to improved growth and economic performance of steers.

Influence of corn silage hybrid type on lactation performance by Holstein dairy cows

The primary objective of this study was to determine lactation performance by dairy cows fed nutridense (ND), dual-purpose (DP), or brown midrib (BM) corn silage hybrids at the same concentration in the diets. A secondary objective was to determine lactation performance by dairy cows fed NutriDense corn silage at a higher concentration in the diet. One hundred twenty-eight Holstein and Holstein × Jersey cows (105 ± 38 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each. Pens were then randomly assigned to 1 of 4 treatments. Three treatment total mixed rations (TMR; DP40, BM40, and ND40) contained 40% of dry matter (DM) from the respective corn silage hybrid and 20% of DM from alfalfa silage. The fourth treatment TMR had ND corn silage as the sole forage at 65% of DM (ND65). A 2-wk covariate adjustment period preceded the treatment period, with all pens receiving a TMR with equal proportions of DP40, BM40, and ND40. Following the covariate period, cows were fed their assigned treatment diets for 11 wk. nutridense corn silage had greater starch and lower neutral detergent fiber (NDF) content than DP or BM, resulting in ND40 having greater energy content (73.2% of total digestible nutrients, TDN) than DP40 or BM40 (71.9 and 71.4% TDN, respectively). Cows fed BM40 had greater milk yield than DP40, whereas ND40 tended to have greater milk yield and had greater protein and lactose yields compared with DP40. No differences in intake, component-corrected milk yields, or feed efficiency were detected between DP40, BM40, and ND40. Milk yield differences may be due to increased starch intake for ND40 and increased digestible NDF intake for BM40 compared with DP40. Intake and milk yield and composition were similar for ND40 compared with BM40, possibly due to counteracting effects of higher starch intake for ND40 and higher digestible NDF intake for BM40. Feeding ND65 reduced intake, and thus milk and component yields, compared with ND40 due to either increased ruminal starch digestibility or increased rumen fill for ND65. Nutridense corn silage was a viable alternative to both DP and BM at 40% of diet DM; however, lactation performance was reduced when nutridense corn silage was fed at 65% of DM.

Effects of altering alfalfa hay quality when feeding steam-flaked versus high-moisture corn grain on ruminal fermentation and lactational performance of dairy cows

This experiment was performed to test a hypothesis that nutritive benefits of feeding high-moisture corn (HMC) would be different when fed with different qualities of alfalfa hay (AH) due to associative effects on ruminal fermentation and nutrient utilization efficiency. Eight multiparous lactating Holstein cows were used; 4 were surgically fitted with ruminal cannulas. Days in milk averaged 184 ± 10.7 at the start of the experiment. The experiment was performed in a duplicate 4 × 4 Latin square design. Within each square, cows were randomly assigned to a sequence of 4 diets during each of the four 21-d periods (14 d of treatment adaptation and 7 d of data collection and sampling). A 2 × 2 factorial arrangement was used; fair-quality AH [FAH; 39.6% neutral detergent fiber (NDF) and 17.9% crude protein (CP)] or high-quality AH (HAH; 33.6% NDF and 21.9% CP) was combined with steam-flaked corn (SFC) or HMC to form 4 treatments: FAH with SFC, FAH with HMC, HAH with SFC, and HAH with HMC. The AH was fed at 32% dry matter (DM) content, whereas SFC or HMC was included at 17% DM content. Quality of AH did not affect DM intake, whereas feeding HMC decreased DM intake, regardless of quality of AH. Digestibility of DM was greater for cows fed HAH compared with those fed FAH (70.1 vs. 67.6%). Digestibility of NDF increased by feeding HMC (67.6 vs. 58.4%), but not by quality of AH. Under FAH, starch digestibility decreased by feeding HMC compared with SFC (85.7 vs. 95.0%), but it was similar under HAH, resulting in an interaction between quality of AH and type of corn grain (CG). Feeding different qualities of AH did not affect milk yield; however, feeding HMC decreased milk yield in FAH diet, causing an AH × CG interaction. Efficiency of milk yield/DM intake was improved due to feeding HMC, regardless of the quality of the AH. In addition, dietary N utilization for milk N tended to increase by feeding HMC, but it was not influenced by quality of AH. Yield of microbial protein increased by feeding HAH diets compared with FAH diets, whereas feeding the HMC diet increased microbial protein yield under the HAH diet, leading to an interaction between and AH and CG. Overall results in this experiment indicate that feeding HMC in AH-based diets improved feed efficiency as well as N utilization efficiency, regardless of quality of AH.

Drives and limits to feed intake in ruminants

The control of energy intake is complex, including mechanisms that act independently (e.g. distention, osmotic effects, fuel-sensing) as well as interacting factors that are likely to affect feeding via their effects on hepatic oxidation. Effects of ruminant diets on feed intake vary greatly because of variation in their filling effects, as well as the type and temporal absorption of fuels. Effects of nutrients on endocrine response and gene expression affect energy partitioning, which in turn affects feeding behaviour by altering clearance of fuels from the blood. Dominant mechanisms controlling feed intake change with physiological state, which is highly variable among ruminants, especially through the lactation cycle. Ruminal distention might dominate control of feed intake when ruminants consume low-energy diets or when energy requirements are high, but fuel-sensing by tissues is likely to dominate control of feed intake when fuel supply is in excess of that required. The liver is likely to be a primary sensor of energy status because it is supplied by fuels from the portal drained viscera as well as the general circulation, it metabolises a variety of fuels derived from both the diet and tissues, and a signal related to hepatic oxidation of fuels is conveyed to feeding centres in the brain by hepatic vagal afferents stimulating or inhibiting feeding, depending on its energy status. The effects of somatotropin on export of fuels by milk secretion, effects of insulin on gluconeogenesis, and both on mobilisation and repletion of tissues, determine fuel availability and feed intake over the lactation cycle. Control of feed intake by hepatic energy status, affected by oxidation of fuels, is an appealing conceptual model because it integrates effects of various fuels and physiological states on feeding behaviour.

The effect of brown midrib corn silage and dried distillers' grains with solubles on milk production, nitrogen utilization and microbial community structure in dairy cows

Ramirez, H. A. R., Nestor, K., Tedeschi, L. O., Callaway, T. R., Dowd, S. E., Fernando, S. C. and Kononoff, P. J. 2012. The effect of brown midrib corn silage and dried distillers' grains with solubles on milk production, nitrogen utilization and microbial community structure in dairy cows. Can. J. Anim. Sci. 92: 365–380. Thirty-six Holstein cows (24 multiparous and 12 primiparous), four multiparous were ruminally cannulated, (mean±SD, 111±35 days in milk; 664±76.5 kg body weight) were used in replicated 4×4 Latin squares with a 2×2 factorial arrangement of treatments to investigate the effects of brown midrib (bm3) and conventional (DP) corn silages, and the inclusion of dried distillers' grains with solubles (DDGS) on milk production and N utilization. Experimental periods were 28 d in length. Treatments were DP corn silage and 0% DDGS; bm3 corn silage and 0% DDGS; DP corn silage and 30% DDGS; and bm3 corn silage and 30% DDGS. Compared with DP hybrid, total tract fiber digestibility was greater for cows consuming bm3 (32.5 vs. 38.1±1.79%) and DDGS (40.0 vs. 35.2±1.76%). Milk yield was not affected by treatment, and averaged 30.5±1.09 kg d−1. Milk protein yield was positively affected by bm3 corn silage and the inclusion of DDGS. An interaction between hybrid and DDGS on milk fat was also observed. The nature of the interaction was such that milk fat was only affected when DDGS were included in the diet and the lowest milk fat was observed when bm3 corn silage was fed (3.46, 3.59, 2.84 and 2.51±0.10% DP 0% DDGS, bm3 0% DDGS, DP 30% DDGS and bm3 30% DDGS, respectively). As a proportion of the total N consumed, manure N was significantly reduced by the inclusion of bm3 corn silage and DDGS (64.1, 57.1, 52.0, 51.2% for DP 0% DDGS, bm3 0% DDGS, DP 30% DDGS and bm3 30% DDGS, respectively). The Firmicutes:Bacteriodetes ratio in the rumen decreased when cattle consumed DDGS. When cows were fed bm3 corn silage, the population of Fibrobacter sp. tended to represent a larger proportion of the total bacterial population (1.8 vs. 2.3±0.28% for DP and bm3, respectively) and this shift may have been driven by the fact that bm3 corn silage has less lignin, therefore the cellulose digesting bacteria may have more access to the cellulose.