Low Crude Protein Concentration Research Articles

Metabolic Profile of F1 Holstein × Zebu Lactating Dairy Cows Under Grazing Supplemented with Two Non-Protein Nitrogen Sources

Pastures dedicated to cattle production in Venezuela have a low crude protein concentration. One of the nutritional strategies to correct the forage protein deficit is using non-protein nitrogen in the diet. To evaluate the effect of two non-protein nitrogen sources on the metabolic profile of lactating dairy cows, 31 F1 Holstein × Zebu multiparous cows averaging 419 ± 46 kg body weight and 17.1 ± 3.3 kg milk·animal·d-1 were randomly assigned to two treatments for 91 days: 1) 59 g·animal-1·d-1 of urea and 2) 64 g·animal-1·d-1 of Optigen II® as slow-release urea (SRU). The animals were grazing (2.12 AU·ha-1) on Urochloa decumbens, U. humidicola, and U. brizantha (7.98-9.61 % CP) and supplied with 4 kg·animal·d-1 of concentrate (15 % CP), and 108, 60, and 108 g·animal·d-1 of mineral, molasses, and bypass fat, respectively. Glucose, total protein, albumin, cholesterol, urea, and β-hydroxybutyrate concentrations, aspartate aminotransferase, and gamma-glutamyl transferase activities were determined in blood serum samples every 28 days. ANOVA analyzed data in a completely randomized design with repeated measures. There were no differences among treatments in the parameters investigated; however, collecting time influenced all of them. No treatment × time interactions were found except for albumin concentration, higher in urea at day 0. The results indicate that under the conditions assayed in the present work, Optigen II® offers no advantage over urea concerning blood indicators of energy and protein metabolism and hepatic functionality in dairy cows.

The effects of grass biomass preservation methods, organic acid treatment and press type on the separation efficiency in the green biorefinery

Processing green biomass into novel products provides opportunities to improve the sustainability of the bioeconomy. The objective of this study was to evaluate the effects of biomass types (fresh, frozen-and-thawed, dried-and-rehydrated and ensiled grass) as well as formic and propionic acid-based additive on the efficiency of liquid-solid separation and crude protein (CP) yield. Three different pressing methods for liquid-solid separation were used. All preservation methods improved biorefinery efficiency compared to fresh grass, and the effect of additive was more profound on the fresh biomass than other materials. However, due to lower CP concentration in the liquid, presumably caused by lower nitrogen solubility, the amount of CP retained in the liquid was not improved in response to the additive treatment. The type of processing technology plays a key role in the extraction of relevant compounds from biomass. With less efficient separation methods, the effects of pretreatments were more pronounced.

FORAGE YIELD AND COMPOSITION OF BLACK OAT IN MONOCULTURE AND IN ASSOCIATION WITH WINTER VETCH

Associated grass-legume pastures have advantages over grass monoculture; in order to evaluate them the association of black oat (Avena strigosa Schreb) with winter vetch (Vicia villosa Roth) was analysed. The objective of the study was to evaluate forage yield, the botanical, morphological, and chemical composition of black oat in monoculture and in association with winter vetch, at different crop heights and residual stubble heights. Eighteen treatments were evaluated in randomized complete blocks with divided plots. In large plots, the culture type (monoculture or association); and in small plots, nine harvest management options (combinations) of three crop heights (Ch: 40, 50 and 60 cm) and three residual stubble heights (Rsh: 8, 14 and 20 cm). Forage yield was higher (p ≤ 0.05) in Ch50-Rsh8, Ch60-Rsh8 and Ch60-Rsh14 during the second crop cycle, with an average 8555 kg DM ha-1. In monoculture and in association, more cuts were made (three to four) with Ch40-Rsh14 and Ch40-Rsh20 and fewer cuts (one to two) with Ch60-Rsh8, Ch60-Rsh14 and Ch60-Rsh20. Crude protein concentration was 19 % higher (p ≤ 0.05) in monoculture than in association (19.2 and 16.2 %); the highest concentrations (p ≤ 0.05) of crude protein were obtained in Ch40-Rsh8, Ch40-Rsh14 and Ch40-Rsh20 (average 20.5 %), and the lowest was recorded in Ch60-Rsh8 (13.2 %). The forage with the least neutral detergent fibre (p ≤ 0.05) was harvested in Ch40-Rsh8, Ch40-Rsh14 and Ch50-Rsh14 (average 43.4 %), and the highest (49.3 %) was obtained in Ch60-Rsh20. In monoculture and in association, a greater amount of forage was harvested, distributed in at least two harvests, with Ch of 50 and 60 cm in combination with 8 and 14 cm of Rsh. However, the forage did not have the best composition, due to higher concentrations of neutral detergent fibre and lower crude protein concentration.

Fodder Galega vs. Alfalfa: Yield and Feed Value of Leaves, Stems, and Whole Plants

Fodder galega (Galega orientalis Lam.) is a perennial forage legume that can be an alternative to alfalfa (Medicago sativa L.) under more difficult environmental conditions. Galega is characterized by leafiness, and technology is now available to harvest leaves separately from stems, providing opportunity to utilize the more nutritious leaves as a feed protein source, and stems for alternative purposes. Our objective was to assess leaf, stem, and whole plant production and nutritive value of galega relative to alfalfa. Field-grown galega and alfalfa were sequentially harvested from bud to late flower maturity stages in first and second growth over two years. The proportion of leaves in galega at each harvest was greater than that of alfalfa, on average by 35%. The yield of galega leaves and yield of crude protein (CP) from leaves was also greater, on average by 31% and 18%, respectively. However, galega leaves had lower CP concentration, contained more fiber, and were less digestible than alfalfa leaves. Although the proportion of stems in galega was lower, the mean dry matter yield of stems of both species was similar. Crude protein concentration in the stems of both species was similar, but galega stems tended to contain more fiber and be less digestible than alfalfa stems. The dry matter yield of whole plant galega was greater than that of alfalfa, especially in the spring cut. Whole plant galega contained, on average, 6% more CP, and galega protein yield was also 16% greater than that of alfalfa. Whole plants of both species were generally characterized by similar levels of fiber and digestibility. The relatively high leaf-protein yield of galega under a two-harvest regime makes fractional harvest of this crop an attractive management strategy.

Canopy characteristics of ‘Mavuno’ hybrid brachiariagrass and ‘Marandu’ palisadegrass harvested at different harvest intensities

‘Mavuno’ is a newly released brachiariagrass (Urochloa hybrid) cultivar with limited information available in the literature. The objective of this study was to compare forage characteristics of this cultivar and ‘Marandu’ palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster cv. Marandu] harvested at 2 different stubble heights during 2 growing seasons (January‒April). The study was conducted in Araguaína, TO, Brazil in 2017 and 2018. Treatments were the factorial arrangement of 2 brachiariagrass cultivars, Mavuno and Marandu, harvested at 2 harvest intensities, 5 and 15 cm stubble height, distributed in a randomized complete block design with 4 replicates. Response variables were canopy height, forage accumulation, proportion of leaf, stem and dead material, and concentration of crude protein (CP) and in vitro digestible organic matter (IVDOM). Mavuno and Marandu did not differ (P>0.05) in forage accumulation (mean = 3,800 kg DM/ha/harvest) and IVDOM concentration (mean = 637 g/kg); however, Mavuno had lower CP concentration (101 vs. 110 g/kg), greater proportion of stems (16 vs. 13%) and less dead material (4 vs. 6%) than Marandu (P<0.05). Harvesting at 5 cm stubble height rather than 15 cm increased herbage accumulation per harvest (4,100 vs. 3,500 kg DM/ha) with decreased proportion of leaves (77 vs. 84%) and CP concentration (101 vs. 115 g/kg) (P<0.05). Our data suggest that Mavuno is a useful addition to the range of brachiaria grass cultivars for sowing in tropical regions and further studies are needed to evaluate the long-term persistence of Mavuno under different management practices in a range of environmental situations. While harvesting at 5 cm stubble height rather than 15 cm increased forage accumulation but reduced CP concentration, regardless of cultivar, longer-term effects on the stability of these pastures with these harvest frequencies and heights are open to question and studies should be continued for longer periods to assess longevity of stands under the 2 management strategies. Applying maintenance fertilizer during the growing season might have prevented the marked decline in dry matter accumulation as the season advanced and this hypothesis should be tested.

Low crude protein diets supplemented with casein hydrolysate enhance the intestinal barrier function and decrease the pro-inflammatory cytokine expression in the small intestine of pigs.

To reduce nitrogen excretion and lower feeding costs, low crude protein (CP) diets are sometimes proposed, however, a great reduction of dietary CP concentration (>4% reduction vs. recommended concentration), even supplemented with essential and nonessential amino acids (AA) can detrimentally affect small intestinal barrier function and immunity, possibly due to the excessive lack of peptides. Here we hypothesize that with an extremely low CP concentration diet, protein-derived peptides, rather than AA supplementation, can improve intestinal barrier development and health. To test this hypothesis, 21 growing pigs (19.90 ± 1.00 kg body weight) were randomly assigned to 3 treatments with control diet (16% CP), or low CP diets (13% CP) supplemented with AA (LCPA) or casein hydrolysate (LCPC) for 28 days. In comparison with the control diet, the LCPA diet decreased the protein expression level of jejunal barrier factor zonula occludens-1 (ZO-1) and stem cell proliferation factor leucine-rich repeat-containing G-protein-coupled receptor-5, whereas the LCPC diet enhanced intestinal barrier function by increasing the protein expression level of jejunal occludin and ZO-1 and ileal mucin-2. The LCPA diet reduced Lactobacillus counts, whereas the LCPC diet increased Lactobacillus counts and reduced Escherichia coli counts in the ileum. The LCPA diet also increased protein expression levels of pro-inflammatory cytokine interleukin-6 (IL-6) and IL-22, whereas the LCPC diet decreased protein expression levels of pro-inflammatory IL-1β, IL-17A and tumor necrosis factor-α in the ileum. Collectively, the casein hydrolysate supplementation of low CP diets showed beneficial effects on the small intestinal barrier, bacterial community, and immunity in pigs, pointing to the important role of protein-derived peptides in small intestinal health in cases of low crude protein diets.

Multi-carbohydrase enzymes improve feed energy in broiler diets containing standard or low crude protein.

This study evaluated the effect of multi-carbohydrase (MC) on energy and nitrogen (N) balance and gene expression in broilers fed diets with different crude protein (CP) contents. The study employed a 2 × 2 factorial arrangement of treatments. The factors were presence or absence of MC, and standard (SCP) or low (LCP) dietary CP concentration. A 3-phase feeding program was used, including starter (0 to 7 d), grower (8 to 17 d) and finisher (18 to 28 d) phases. The study was undertaken in closed calorimetry chambers. Each of the 4 dietary treatments was replicated 8 times in total across 2 runs, with 2 birds per replicate (n = 64). Data for energy partitioning and N balance were collected from d 25 to 28. On d 28, birds were euthanized to collect muscle and intestinal tissue samples for gene expression. The results showed that the MC increased apparent metabolizable energy (AME, P < 0.01) and net energy (NE, P < 0.05), and reduced the feed conversion ratio (FCR, P < 0.01) in all diets. The proportion of energy retained as fat per total energy retention (REf/RE) was positively correlated with feed AME and NE (r = 0.541, P < 0.01 and r = 0.665, P < 0.001, respectively), suggesting that feed energy augmented with increased fat gain. Muscle ATP synthase subunit alpha (ATP5A1W) gene expression had a positive correlation with REf/RE and feed NE (r = 0.587, P < 0.001 and r = 0.430, P < 0.05, respectively). Similarly, muscle peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1A) expression was negatively correlated with weight gain and positively correlated with FCR (r = −0.451, P < 0.05 and r = 0.359, P < 0.05, respectively). These correlations show that over-expressions of muscle genes related to energy production reduce bird performance. This study demonstrated that MC increase dietary energy utilization, regardless of dietary CP concentration. However, the energy released by the enzymes increases feed energy-to-CP ratio, meaning there is excess energy that is then deposited as body fat. This suggests that supplemental MC in broiler feeds is beneficial if diets are formulated to contain marginal energy levels.

Incorporating a Fresh Mixed Annual Ryegrass and Berseem Clover Forage Into the Winter Diet of Dairy Cows Resulted in Reduced Milk Yield, but Reduced Nitrogen Excretion and Reduced Methane Yield.

The winter diet of dairy cows in Mediterranean climate regions is usually a total mixed ration with a base of conserved summer crops such as corn silage and alfalfa hay. However, there is increased labor and financial cost related to this kind of feeding, which could be reduced if fresh forages were used in place of some of the conserved forage in the cow diet. The objective of our study was to evaluate the effect of including fresh mixed annual ryegrass and berseem clover into the diet of dairy cows on milk, nitrogen utilization, and methane emission. Twenty-four lactating dairy cows were split into two groups and offered either a diet similar to that usually offered to the cows (CON) or one where a mixture of fresh annual ryegrass and berseem clover was used to partially substitute the corn silage and alfalfa hay in the diet (MIX). Milk yield was recorded automatically, and methane emissions were estimated using the SF6 tracer technique. The MIX diet had lower crude protein concentration (148 vs. 170 g/kg DM) but higher DM digestibility (81.6 vs. 78.6%) than the CON diet. Compared to the cows offered the CON diet, milk yield was reduced when cows were fed the MIX diet (36.4 vs. 31.9 kg/d), but methane emissions (381 vs. 332 g/d) and nitrogen excretion were also reduced (238 vs. 180 g/d). Nitrogen use efficiency was unaffected (30.8%). In addition, milk from cows fed the MIX diet had a fatty acid profile considered to be more beneficial to human health than that of the milk from cows fed the CON diet. Increasing the protein concentration in the MIX diet, either by direct supplementation or increasing the proportion of legume in the mixed herbage, could overcome the reduction on milk and positively affect methane emission and N use efficiency.

The effect of grazing by cattle and sheep on diverse pastures>

The aim of this research was to assess differences in pasture properties associated with grazing diverse swards. A total of six fields were studied on commercial farms in the west of the UK, with three fields being permanent pastures (M1, V2 and M2) and three temporary ley pastures (V1, V3 and M3). Each field was monitored monthly for three months during the autumn when all fields were being grazed. Pastures included a diverse range of grass, legume, herb, flower and weed species. Pasture properties assessed included measurements of grass content, greenness (both %), height (in centimeters), pasture cover (fresh and dry matter in kg per hectare) and pasture density (fresh and dry matter in kg per hectare per centimeter) and nutrient concentrations. The nutrient concentrations measured were dry matter, crude protein, acid detergent fibre (ADF), neutral detergent fibre (NDF), sugars, ash, digestible organic matter in the dry matter (DOMD), oil, nitrate nitrogen, and metabolisable energy (ME). A linear mixed model was used to assess the effect of field, month of study and grazing on pasture properties. This study showed that across fields studied grazed swards were shorter with a higher grass content and fresh/dry herbage density compared to ungrazed swards. Across diverse pastures studied grazed swards had higher nutrient concentrations of dry matter, ADF, NDF and nitrate nitrogen, but lower concentrations of crude protein, sugars and ash. There was no difference in digestibility among grazed and ungrazed swards. While grazing may reduce pasture biomass and certain nutrient concentrations within a pasture, it appears to enhance the grass content and density of the sward, which may provide more sustainable grassland systems.

Effects of supplemented nonessential amino acids and nonprotein nitrogen on growth and nitrogen excretion characteristics of broiler chickens fed diets with very low crude protein concentrations

Reducing dietary CP for broiler chickens below a certain threshold results in decreased growth, even when the supply of essential amino acids and glycine equivalent (Glyequi) is adequate, probably because other nonessential amino acids (neAA) are growth-limiting. Nonprotein nitrogen (NPN) might be used for the synthesis of neAA. Therefore, the effects of specific neAA and ammonium chloride (NH4Cl) supplementation on the growth and N-excretion characteristics of broiler chickens were investigated. Nine male Ross 308 broiler chickens were kept in each of 81 metabolism units from day 7 to 21 and received 1 of 9 diets in 9 replicates in a one-factorial arrangement of treatments. Two diets with different neAA concentrations, except for Glyequi, were mixed resulting in CP levels of 180 (CP180) and 160 (CP160) g/kg. In six other diets, CP160 was supplemented with either l-Ala, l-Pro, l-Asp, a mix of l-Asp and l-Asn·H2O, l-Glu, or a mix of l-Glu and l-Gln to achieve concentrations of the respective neAA as formulated in CP180. In a further diet, NH4Cl was added to CP160 to achieve the CP concentration of CP180. The ADG and gain:feed ratio (G:F) from day 7 to 21 were highest at CP180. Reduced neAA concentrations in CP160 decreased ADG and G:F. Supplementation of Asp+Asn, Glu, and Glu+Gln to CP160 increased ADG and G:F, but not to the level found for CP180. Compared with CP160, addition of Asp increased G:F but not ADG. Supplementation of Asp+Asn caused higher ADG and G:F than supplementation of Asp alone. The N-utilization efficiency was highest at CP160 and at CP160 supplemented with Ala, Pro, and Glu. Lower N-utilization efficiency was found at CP180 than at CP160, without and with supplemented neAA. The treatment containing NH4Cl presented the lowest ADG, G:F, and N-utilization efficiency. These results showed that individual supplementation of Asp+Asn, Glu, and Glu+Gln partly compensates for the growth-reducing effects of very low CP diets. Supplementation of NH4Cl as NPN source is not suitable for broiler chickens.

Investigation on the variation of chemical composition and in vitro nutritive value of spelt (Triticum aestivum ssp. spelta) for ruminants.

Spelt has gained growing interest in Europe in human and animal nutrition. Data on the chemical composition of spelt and its variations, especially their nutritional value for ruminants, are scarce. Therefore, hulled kernels, dehulled kernels and hulls of six spelt cultivars grown on three different locations were analysed for their chemical composition and nutritive value for ruminants using the Hohenheim Gas Test. Most of the analysed constituents varied considerably and were significantly affected by the cultivars or location, or both. Hulled spelt and spelt kernels of more recent cultivars had higher starch and energy concentrations and lower concentrations of crude protein and fibre fractions than those of traditional cultivars. Significant differences between cultivars were found in the energy values for ruminants for hulled spelt but not for fractionated kernels. Spelt hulls of different cultivars and locations showed a high variation in chemical composition with overall high concentrations of fibre fractions and crude ash. The nutritive values for ruminants of hulled spelt and spelt kernels were similar to those of oats and wheat respectively. Pure spelt hulls cannot be recommended for use in ruminant feeding because of their high concentrations of fibre fractions and crude ash. However, when some part of the kernel (~20%) or small kernels remain with the hull in the dehulling process, the resulting hull fraction has a metabolizable energy value for ruminants that is similar to that of wheat straw.

ESTIMATION OF THE REQUIREMENT OF METABOLIZABLE ENERGY AND CRUDE PROTEIN FOR GROWING IN RHODE ISLAND RED CHICKENS, UNDER TROPICAL CONDITIONS OF SOUTHEASTERN MEXICO

&lt;p&gt;The objective of the current study was to estimate the requirement of metabolizable energy (ME) and crude protein (CP) for growing Rhode Island Red male chickens from 17 to 119 days-old, under tropical conditions of Yucatan, Mexico. The experiment consisted in three feeding phases (17–56, 57–91, 92–119 days old), using a factorial 2x3 design for each one. Two constant ME (2900 and 3100 kcal/kg DM), and three CP concentrations (% DM) that varied with age: 22, 20 and 18% (17–56 days-old); 20, 18 and 16% (57–91 days-old); and 18, 16 and 14% (92–119 days-old) were used. Two batches of 72 Rhode Island Red male chickens each one was used; the first one for the first feeding phase and the second batch for the second and third feeding phases. Response surface procedures to obtain the best ME and CP concentrations were carried out. The body weight gain (BWG) and feed intake (FI) were greater in the first feeding phase with 2900 kcal ME/kg DM in the diet; however, in the second phase there was not significant effect of energy concentration. From 17–91 days-old, the FI increased with 2900 kcal ME/kg DM in the diet. Chickens had a higher BWG from 92–119 days-old when 16% CP was included in the diet. Protein efficiency was better from 17–119 days-old when the lower CP concentration was included in the diet. In conclusion, the greatest BWG were obtained, when 2900 kcal ME/kg DM, for the three feeding phases, was used. The best approximations of CP requirement in the diet for the first, second and third feeding phases were 21.3%, 19.2% and 17.1%, respectively.&lt;/p&gt;

Variation in rate of phenological development and morphology between red clover varieties: Implications for clover proportion and feed quality in mixed swards

AbstractRed clover (Trifolium pratense) grown in mixtures with grasses often constitutes a lower proportion of total yield in spring than in summer growth. A more even red clover proportion between the harvests would benefit forage quality and management at feeding. We investigated whether inclusion of early versus late‐maturing red clover varieties could reduce this disproportionality. In a two‐year field trial harvested three times per season, each of six red clover varieties was grown in two grass mixtures. Rate of phenological development did not differ during spring growth, but did so in regrowth after first and second cuts. Here, the earliest varieties constituted the highest proportion. At all harvests, the early varieties had lower crude protein concentrations and a higher content of neutral detergent fibre (NDF) and indigestible NDF than the late varieties. Clover proportion was higher in swards with a mixture of timothy and meadow fescue than in swards with perennial ryegrass during the first year and lower in the second year. It is concluded that developmental rate should be explored further as a key character for red clover competiveness in spring growth of rapidly elongating grasses.

An on-farm study of the herbage quality and sward characteristics of plantain-clover mixes during late summer and autumn and resulting lamb growth rates

An on-farm study investigated the herbage quality and sward characteristics of plantain-clover mixes and resulting lamb growth rates during late summer and autumn. Three farms were chosen, each with a minimum of 10 ha of plantain-clover mix (Plantago lanceolata ‘Ceres Tonic’, Trifolium pratense, Trifolium repens) used for lamb finishing. Each farm managed the plantain-clover mix area using their routine management without advice or comment from research staff. Throughout autumn, at approximately monthly intervals on the three farms, the pre- and post-grazing herbage masses, botanical composition, herbage quality, plantain dry matter content, secondary chemical composition and lamb growth rates were monitored. A low percentage of clover in the sward, a high percentage of dead stem material and a low crude protein concentration in plantain during dry periods, were identified as the most likely causes of low lamb liveweight gains during autumn. Grazing management during spring that maintains control of plantain stems and encourages the presence of clover, appears to be a key management technique for ensuring high lamb liveweight gains on plantain-clover mixes in late summer and autumn.

Effects of dietary crude protein concentration on late-lactation dairy cow performance and indicators of nitrogen utilization

The objectives of this study were to measure performance responses and to evaluate indictors of N utilization in late-lactation cows fed diets with incremental reductions in crude protein (CP) concentration. Holstein cows (n = 128; 224 ± 54 d in milk) were stratified by parity and days pregnant (86 ± 25 d) and randomly assigned to 1 of 16 pens in a randomized complete block design. For 3 wk, all cows received a covariate diet containing 16.9% CP [dry matter (DM) basis]. For the subsequent 12 wk, pens were randomly assigned to 1 of 4 treatments that contained 16.2, 14.4, 13.1, or 11.8% CP (DM basis). Diets were offered once daily and contained 32.5% corn silage, 32.5% alfalfa silage, 13.5% high-moisture corn, and 21.5% concentrate mix. A reduction in dietary CP was achieved by replacing soybean meal with soy hulls in the concentrate mix (DM basis). Dry matter intake, milk urea N (MUN; mg/dL), and the yield of milk urea N (g/d) decreased linearly with dietary CP. Compared with a 16.2% CP diet, a 14.4% CP diet did not alter milk yield throughout the study, but the 13.1 and 11.8% CP diets reduced milk yield after 4 and 1 wk, respectively. Furthermore, milk protein percentage was reduced for all dietary CP less than 16.2%, but this negative effect was temporary and disappeared after 7 wk for the 14.4% CP diet. In contrast, MUN adjusted to a new steady state within 1 wk for all dietary treatments. Modeling quadratic responses with a plateau led to predictions of no reduction in fat- and protein-corrected milk (32.6 kg/d) and yields of fat (1.31 kg/d), lactose (1.49 kg/d), and true protein (1.12 kg/d) until dietary CP decreased below 15.5, 15.3, 15.9, and 16.2%, respectively. In this study, MUN and the yield of MUN were highly correlated with N intake, milk protein yield, and fat- and protein-corrected milk. Surprisingly, N use efficiency (milk protein N/intake N) was not correlated with any variables related to N utilization and reached an apparent upper limit of approximately 30%. Although this observation may be associated with feeding diets deficient in metabolizable protein, late-lactation cows in this study adjusted to low dietary CP concentration better than anticipated as milk production was 2.6, 3.6, 6.4, and 8.0 kg/d higher than National Research Council (2001)-predicted metabolizable protein-allowable milk for dietary CP of 16.2, 14.4, 13.1, and 11.8%, respectively.

Herbage Mass and Nutritive Value of Bermudagrass Influenced by Non‐Growing‐Season Herbicide Application

Core Ideas Dormant‐season herbicide applications are effective in controlling cool‐season weeds in bermudagrass. Some dormant‐season herbicide products can negatively impact bermudagrass forage production. Dormant‐season application of glyphosate did not cause significant damage to the bermudagrass stand. Elimination of cool‐season weeds in bermudagrass may not always be advantageous. Application of herbicides to dormant bermudagrass [Cynodon dactylon (L.) Pers] in late winter to control cool‐season weeds is a possible management practice for more marketable hay harvests. The objective of this study is to determine dormant‐season herbicide effects on bermudagrass herbage mass and nutritive value at four harvest dates typical for Louisiana. The experimental design was a randomized complete block of Roundup (glyphosate), Plateau (imazapic), Journey (imazapic + glyphosate), Pastora (nicosulfuron + metsulfuron methyl), and a control (no herbicide treatment). The treatments were applied mid‐February of 2013 and 2014. Cool‐season weeds contain lower neutral detergent fiber (NDF) concentration than bermudagrass while containing higher acid detergent fiber (ADF), crude protein (CP), and in vitro dry matter digestibility (IVDMD). Pastora resulted in the highest bermudagrass composition of 65.2% (DM basis) at the first harvest, followed by Journey, Plateau, Roundup, and control treatment with 44.2, 33.6, 28.3, and 20.7%, respectively. Herbicide × harvest interaction was significant for herbage accumulation and nutritive value. Pastures receiving Pastora and Journey accumulated less herbage with lower CP concentration than pastures receiving Roundup and control due to lower weed composition. Year × herbicide interaction was significant and herbage mass from Pastora treated pasture was lower in 2014 than 2013. It was concluded that dormant‐season herbicide applications may be beneficial for producing a weed‐free first harvest of bermudagrass hay, but may sacrifice some nutritive value provided by the inclusion of cool‐season herbage mass, grass, and broadleaf weeds, in the harvested product.

Continental-Scale Patterns Reveal Potential for Warming-Induced Shifts in Cattle Diet.

In North America, it has been shown that cattle in warmer, drier grasslands have lower quality diets than those cattle grazing cooler, wetter grasslands, which suggests warming will increase nutritional stress and reduce weight gain. Yet, little is known about how the plant species that comprise cattle diets change across these gradients and whether these shifts in dietary quality coincide with shifts in dietary composition, i.e. the relative abundance of different plant species consumed by cattle. To quantify geographic patterns in dietary composition, we analyzed the dietary composition and dietary quality of unsupplemented cattle from 289 sites across the central US by sequence-based analyses of plant DNA isolated from cattle fecal samples. Overall, assuming that the percentage of reads for a species in a sample corresponds to the percentage of protein derived from the species, only 45% of the protein intake for cattle was derived from grasses. Within the Great Plains, northern cattle relied more on grasses than southern cattle, which derived a greater proportion of their protein from herbaceous and woody eudicots. Eastern cattle were also more likely to consume a unique assemblage of plant species than western cattle. High dietary protein was not strongly tied to consumption of any specific plant species, which suggests that efforts to promote individual plant species may not easily remedy protein deficiencies. A few plant species were consistently associated with lower quality diets. For example, the diets of cattle with high amounts of Elymus or Hesperostipa were more likely to have lower crude protein concentrations than diets with less of these grasses. Overall, our analyses suggest that climatic warming will increase the reliance of cattle on eudicots as protein concentrations of grasses decline. Monitoring cattle diet with this DNA-based sequencing approach can be an effective tool for quantifying cattle diet to better increase animal performance and guide mitigation strategies to changing climates.

Effect of a type of hybrid on the chemical composition and digestibility of organic matter of whole maize plant silage

A three-year long study (2009-2011) was conducted on seven single-cross and seven three-way-cross corn varieties. Entire chopped plant silage was ensiled in microsiloses of 1.7 l capacity. The content of dry matter, crude, crude protein, crude fat, crude fibre and starch were determined in the forage produced from silage. The levels of detergent fibre NDF and ADF, as well as ADL-lignin and organic matter digestibility of silage via in vitro method were also determ­ined. Single-cross hybrids showed lower concentrations of crude protein and crude fat and more NFC than three-way-cross (P ≤ 0.01). Other nutrients showed no statistically significant differences. Hybrid type did not affect the digestibility of organic matter. The year of the research had a high statistically significant effect on the nutrient content of dry matter and organic matter digestibility of whole corn plant silage. Influence was stated of the hybrid type and year of the research on crude protein concentration (P ≤ 0.05), acid detergent lignin and crude lignin concentration (P ≤ 0.01) in the studied hybrids of corn.

The inclusion of forage mixtures in the diet of growing dairy heifers: Impacts on digestion, energy utilisation, and methane emissions

Intensive farming focusing on monoculture grass species to maximise forage production has led to a reduction in the extent and diversity of species-rich grasslands. However, plant communities with higher species number (richness) are a potential strategy for more sustainable production and mitigation of greenhouse gas (GHG) emissions. Research has indicated the need to understand opportunities that forage mixtures can offer sustainable ruminant production systems. The objective of the two experiments reported here were to evaluate multiple species forage mixtures in comparison to ryegrass-dominant pasture, when conserved or grazed, on digestion, energy utilisation, N excretion, and methane emissions by growing 10–15 month old heifers. Experiment 1 was a 4×4 Latin square design with five week periods. Four forage treatments of: (1) ryegrass (control); permanent pasture with perennial ryegrass (Lolium perenne); (2) clover; a ryegrass:red clover (Trifolium pratense) mixture; (3) trefoil; a ryegrass:birdsfoot trefoil (Lotus corniculatus) mixture; and (4) flowers; a ryegrass:wild flower mixture of predominately sorrel (Rumex acetosa), ox-eye daisy (Leucanthemum vulgare), yarrow (Achillea millefolium), knapweed (Centaurea nigra) and ribwort plantain (Plantago lanceolata), were fed as haylages to four dairy heifers. Measurements included digestibility, N excretion, and energy utilisation (including methane emissions measured in respiration chambers). Experiment 2 used 12 different dairy heifers grazing three of the same forage treatments used to make haylage in experiment 1 (ryegrass, clover and flowers) and methane emissions were estimated using the sulphur hexafluoride (SF6) tracer technique. Distribution of ryegrass to other species (dry matter (DM) basis) was approximately 70:30 (clover), 80:20 (trefoil), and 40:60 (flowers) for experiment 1. During the first and second grazing rotations (respectively) in experiment 2, perennial ryegrass accounted for 95 and 98% of DM in ryegrass, and 84 and 52% of DM in clover, with red clover accounting for almost all of the remainder. In the flowers mixture, perennial ryegrass was 52% of the DM in the first grazing rotation and only 30% in the second, with a variety of other flower species occupying the remainder. Across both experiments, compared to the forage mixtures (clover, trefoil and flowers), ryegrass had a higher crude protein (CP) content (P<0.001, 187 vs. 115gkg −1 DM) and DM intake (P<0.05, 9.0 vs. 8.1kgday −1). Heifers in experiment 1 fed ryegrass, compared to the forage mixtures, had greater total tract digestibility (gkg −1) of DM (DMD; P<0.008, 713 vs. 641) and CP (CPD, P<0.001, 699 vs. 475), and used more intake energy (%) for body tissue deposition (P<0.05, 2.6 vs. −4.9). For both experiments, heifers fed flowers differed the most compared to the ryegrass control for a number of measurements. Compared to ryegrass, flowers had 40% lower CP content (P<0.001, 113 vs. 187gkg −1), 18% lower DMD (P<0.01, 585 vs. 713gkg −1), 42% lower CPD (P<0.001, 407 vs. 699gkg −1), and 10% lower methane yield (P<0.05, 22.6 vs. 25.1gkg −1 DM intake). This study has shown inclusion of flowers in forage mixtures resulted in a lower CP concentration, digestibility and intake. These differences were due in part to sward management and maturity at harvest. Further research is needed to determine how best to exploit the potential environmental benefits of forage mixtures in sustainable ruminant production systems.

Milk production response to varying protein supply is independent of forage digestibility in dairy cows

The aim of this experiment was to examine whether the positive response in milk production to increased crude protein (CP) supply in dairy cows was dependent on the digestibility of the forage. Forty-eight lactating Danish Holstein cows were used in a 4×4 Latin square design experiment with 4 rations: (1) high digestibility and high CP concentration (HdHp), (2) high digestibility and low CP concentration (HdLp), (3) low digestibility and high CP concentration (LdHp), and (4) low digestibility and low CP concentration (LdLp). All rations contained 30% corn silage, 25% grass-clover silage, and 45% concentrate on a dry matter (DM) basis. Different digestibilities were obtained by replacing a high-digestible grass-clover silage combined with a high-digestible corn silage with a low-digestible grass-clover silage combined with a low-digestible corn silage. Organic matter digestibilities were 79.8 and 74.7% in the high- and low-digestibility rations, respectively. Dietary CP concentration in the ration was increased by substituting barley and sugar beet pulp with rapeseed meal and soybean meal, whereby CP increased from 13.9 to 14.0% (Lp) to 15.7 to 16.0% (Hp). All cows were offered 3kg of the same concentrate per day in the automatic milking system in addition to the mixed ration. Every feeding period lasted 3 wk, and DM intake and milk yield were measured in the last week in each period, and milk samples for determining milk composition, including fatty acid content, and blood samples were taken during the last 3d of each period. Dry matter intake increased by 2.2kg/d on Hd compared with Ld and by 0.7kg/d on Hp compared with Lp. The positive effect on DM intake was reflected in the energy-corrected milk (ECM) yield, as a higher ration digestibility increased the ECM yield by 1.7kg/d and a higher CP concentration increased it by 1.2kg/d. We detected no interaction between forage digestibility and CP concentration on milk production. Reduced digestibility was accompanied by an increase in the plasma level of glucose, suggesting that other nutrients were limiting to milk production. In conclusion, milk production responses to dietary CP supply appeared independent of forage digestibility.