Primary Forage Source Research Articles

Management strategies to improve the nitrogen use efficiency in grasslands and the protein quality in grass silages: Lessons from a practical study on dairy farms in Flanders

AbstractBackgroundGrasslands are the primary source of forage for ruminants. Legal restrictions on nitrogen fertilization force farmers to optimize nitrogen use efficiency (NUE) of grassland and protein quality in grass silage.MethodsThe present study included grassland data from 10 dairy farms in Flanders. For each grassland field, the presence of clover was determined based on the seed mixture composition. Soil and manure were sampled before the first application and analyzed to determine plant available N content. The annual NUE was calculated for each field possible (n = 28). Prewilted grass samples were taken just before ensiling (n = 65) and grass silage samples (n = 41) were collected from the same fields.ResultsClover fields demonstrated improved NUE due to a lower nitrogen input from fertilizers compared to pure grassland fields (75 vs. 265 kg ha−1). The protein quality of the grass silage was positively correlated with the organic matter digestibility, sugar content, and dry matter content of the prewilted grass. Conversely, crude ash content had a negative effect.ConclusionsThese findings underscore the importance and potential of clover and the practical feasibility of optimizing grassland management to improve both NUE in grasslands and protein quality of the silage.

Effect of feeding corn silage on semen quality and spermatogenesis of bulls.

Bovine reproduction, including male fertility traits like semen quality, are influenced by a variety of different factors like breed, nutrition, environment, and feeding management. Diet in a crucial determinant, and in this regard although corn silage is generally considered to be a favorable roughage for fattening meat type breeds, it tends to have a negative impact on semen quality. In the current study, alfalfa hay was substituted by corn silage as a roughage source in the diet of bulls to investigate its effects on the fertility of breeding bulls. A feeding trail spanning 140 days was conducted, with semen collection occurring twice a week commencing 60 days after the start of trial. Semen quality parameters, serum antioxidant indexes, sex hormone content in semen, rumen microflora, and sperm transcriptome were characterized. Feeding corn silage enhanced host antioxidant capacity, significantly decreased spermatozoal motility and increased sperm deformity rate in bulls. Furthermore, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) content in semen were significantly decreased (P < 0.05), and the inhibin B (INHB) content was significantly increased (P < 0.01). Feeding corn silage led to significant changes in the diversity of rumen microbiota of cattle at the phylum and genus levels, some of which were significantly correlated with semen quality. Subsequent RNA sequencing indicated that DHH and PITHD1, two genes related to sperm and reproductive development, were differentially expressed, and enrichment analysis also identified several pathways and biological functions relevant to sperm development and reproduction. These results indicate that feeding corn silage modulates semen quality via different pathways. Firstly, corn silage metabolites likely affect the secretion of INHB through the testicular capillaries, which affects semen quality by regulating genes involved in spermatogenesis. Secondly, low lignin content in silage corn appears to reduce abundance of rumen flora that are positively correlated with semen quality. Overall, results indicate that feeding bulls corn silage as the primary source of forage could negatively impact semen quality and may not be appropriate as the primary roughage of forage for breeding bulls.

Range grasses to improve soil properties, carbon sustainability, and fodder security in degraded lands of semi-arid regions

Tropical grasses are the primary source of forage for livestock and a valuable resource for improving soil health and environmental sustainability in semi-arid regions. A study was carried out in a semi-arid region of central India to determine the short-term (6-year) impact of nine range grasses on soil physio-chemical and biological properties, carbon stock, and forage security. The experiment was carried out in a randomized block design with three replications. Results show that the majority of the grass roots were distributed in the upper soil layer (0–10 cm, 63.5–76.5 %), and then in the middle (10–20 cm, 21.3–25 %) and lower (20–30 cm, 2.2–11.5 %) layers. Perennial tussock grass (Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult) had a higher root volume (2219 mm3), followed by Guinea grass [Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs] (1860 mm3). A lower soil bulk density (BD, 1.11–1.23 g cm−3), higher gravimetric water content (GMW, 14.0–17.8 %), and soil organic carbon (0.38–0.73 %) were recorded for grass-cultivated plots compared to the barren land (1.38 g cm−3, 13.0 %, and 0.28 %, respectively). The perennial tussock grass and Guinea grass resulted in the highest soil microbial biomass carbon (SMBC, 70.1 mg kg−1 soil) and enzyme activities (dehydrogenase, 17.09 μg TPF g−1 day−1 and fluorescein diacetate activity 4.94 μg fluorescein g−1 h−1). The considerable improvement in soil properties with minimal inputs resulted in a higher sustainable yield index and carbon sustainability index in plots planted with Guinea grass (0.9 and 89.29) and perennial tussock grass (0.89 and 71.61). Therefore, the cultivation of either Guinea grass or perennial tussock grass as an intercrop or sole crop in the semi-arid environment can be an ecologically sound strategy to improve soil health, C sequestration, and fodder supply.

Budidaya Sorgum (Sorghum bicolor L. Moench) Sebagai Alternatif Penyediaan Pakan Ternak Berkelanjutan

The cow farmer in Padang was changed from semi-intensive to intensive because of city development. The intensive system requires farmers to be forage feeding cut and carried from field margins. The limited knowledge of smallholder farmers about the high quality of forage causes native grass to become the primary source of forage; meanwhile, the low nutrient content of native grass causes the low production and reproduction in cows. To overcome the adequacy of feed forage, both in quality and quantity, thus cultivation of forage was conducted on unproductive land such as peatlands. Generally, peatland with a shallow category and low pH is widespread on the coast of Padang city. Sorghum is tolerant to acid soil and can be the solution to overcome forage feeding in the dry season. The community service activities were carried out from October 2021 until January 2022 and aimed to increase farmers' knowledge in feed diversification and skills in cultivating sorghum as a superior feed crop. The activities were conducted using counselling and discussion methods and the practice of sorghum cultivation on peatlands. Results showed that cow farmers know the importance of providing quality sustainable forage to increase livestock productivity, especially brood cows. The conclusion is that sorghum can be a substitute for native grass and as a concentrate; hence it can be an alternative solution to the problem of supplying feeding in Padang city.&#x0D;

Long-term ecosystem carbon losses from silage maize-based forage cropping systems

Intensification of the US dairy industry has driven increased reliance on maize (Zea mays L.) silage as a primary forage source in place of perennial forages such as alfalfa (Medicago sativa L.). Using 29 site-years of eddy covariance, plant, and manure measurements, we calculated net ecosystem C balances (NECB) for two silage maize-based forage cropping systems and a soybean-maize grain rotation. We found that C losses were over threefold greater from continuous silage maize (-4.9 Mg C ha−1 yr−1) than from the predominant grain cropping system in the region, the soybean-maize rotation (-1.3 Mg C ha−1 yr−1). Including alfalfa in rotation reduced C losses by 23% relative to continuous silage maize, but net losses were still observed (-3.8 Mg C ha−1 yr−1). For every megagram of crop residue C left in-field, net C balances increased by +0.9 Mg C ha−1. A winter rye (Secale cereale L.) cover crop and applications of liquid dairy manure marginally improved C-balances but were insufficient to offset C losses in respiration and crop harvest. Increasing manure application rates could bring these systems to a net equilibrium C balance but would also result in soil N and P surpluses and unacceptable loss of nutrients to air and water. Since 1980, over 800,000 hectares of alfalfa have been lost across the Upper Midwest US, and C export in harvested maize grain and silage have increased dramatically. This shift implies a substantial reduction in SOC on forage cropped soils in the region.

Characterization of Forage Utilization and Pasture Management Practices on Florida Horse Operations

This study used an online survey to gather information on forage utilization and pasture management practices implemented on horse farms in Florida. We hypothesized that pastures were inadequately managed and underutilized, resulting in greater reliance on hay. Data from 80 complete responses were submitted to descriptive analysis and Fisher’s exact test. Significantly associated variables were also evaluated using multiple correspondence analysis. The primary function of the facility most reported was recreational horse use (62%). Nearly all operations (n = 79) had pasture available, with 57% reporting housing horses on pasture full time (24 hr/d) and 48% reporting implementation of rotational stocking. Most respondents reported using a combination of hay and pasture (57.5%) as their primary source of forage, followed by pasture only (32.5%) and hay only (10%). Pasture maintenance was performed by 82% of respondents, and 6% did not implement any type of pasture management. Primary forage fed to the horses was related to the type of pasture management implemented (P = .0313) and turnout practices (P = .0003). The multiple correspondence analysis showed that relying on hay as the primary source of forage was associated with a shorter duration of pasture access and lack of pasture management. Most operations did not have their hay (89%) or pasture (94%) analyzed for nutrient composition. Despite pasture availability, lack of adequate pasture management appeared to contribute to a greater dependence on hay feeding. Pasture management practices and forage analysis are potential areas for horse owner education in Florida.

Optimal management of cattle grazing in a seasonally dry tropical forest ecosystem under rainfall fluctuations

Climate change will likely trigger shifts in rainfall regimes that may intensify water scarcity in semi-arid regions. In the semi-arid region of Brazil, the seasonally dry ecosystem is the primary source of forage for livestock. Because the correct stocking rate of livestock (animals per area) is not well understood, overgrazing tends to advance rangeland degradation in this ecosystem. This implies that the region may become even more vulnerable under changing rainfall regimes, which in turn may exacerbate livestock and food insecurity. We developed a coupled soil water balance, vegetation, and cattle biomass model to illustrate the impacts of rainfall seasonality on the dynamics of vegetation and animal growth. The outcomes were simulated by considering different stocking rates and the timing of animal placement and removal from the rangeland. A more pronounced reduction in vegetation biomass was found in grazed vs. non-grazed paddocks. Under strongly seasonal rainfall patterns, the maximum animal weight gain decreases with average rainfall inter-arrival time and increases with total annual rainfall. Thus, a forecast of dry spells could benefit farmers in planning grazing management strategies. Our model can be used to test different management scenarios and give feedback for local herders, and to guide future experiments to reduce the time and cost of acquiring data.

To chop or not to chop? Tackling shrub encroachment by roller-chopping preserves woody plant diversity and composition in a dry subtropical forest

Shrub encroachment is a frequently observed phenomenon in the arid and semi-arid biomes. In the dry forests of the Argentine Chaco ecoregion that are affected by shrub encroachment, the growing demand for grazing areas has led to the creation of a silvopastoral system. Under the Chaco silvopastoral system, a commonly used treatment to disrupt the excessive shrub layer and promote the growth of grasses is roller-chopping by a tractor-pulled iron drum. While previous studies evaluating the effects of roller-chopping on diversity have focused mostly on the herbaceous stratum as the primary source of forage, much less is known about the effects of roller-chopping on woody plants. To fill this gap, we measured woody plants of the shrub layer in a low-intensity roller-chopping experiment in northern Argentina after applying different frequencies of roller-chopping in a semi-arid Chaco forest area with a well-developed shrub layer. Data were collected in an experiment in which 3 different roller-chopping treatments were applied: a single two-pass roller-chopping in the summer of 2006/2007 (RCh1); a one-pass roller-chopping in the summer of 2006/2007, repeated in the summer of 2014/2015 (RCh2); and no treatment (Control). In each treatment, 16 circular, randomly placed plots with a radius of 9m were sampled, and all woody plants in the shrub layer with a diameter ≥10mm at the base were recorded. The diversity was analysed using profiles of alpha and beta diversity and by calculating the average distance from an individual circular plot to the treatment group centroid defined in the principal coordinate space. In total, 26 species of woody plants were recorded, of which 24 were found in Control, 22 in RCh1, and 23 in RCh2. Although the alpha diversity differed only slightly among the treatments, the beta diversity of the roller-chopped treatment areas was generally higher than that of the untreated plots. The species composition of the roller-chopped plots differed little from that of the control plots. Our study revealed little overall effect of roller-chopping on the species diversity and composition of woody plants. The transformation of the Chaco forest degraded by shrub encroachment to a silvopastoral system by roller-chopping is changing the structure of the forest but to a large extent has retained the presence and the relative abundance of woody plant species. We conclude that roller-chopping is a good management tool to reduce woody plant encroachment and create a silvopastoral system while preserving ecosystem functions.

The utilization and apparent ruminal digestibility of dual-purpose food plots for wildlife and cattle grazing

Abstract The objective of this study was to examine cattle and deer utilization of nine different varieties of forage cereal grains. Yield and forage quality were also determined as well as apparent ruminal digestibility of select forage cereal grains. Cattle preferred annual ryegrass, followed by the oat varieties compared to wheat varieties. Deer preferred the wheat varieties and utilized the plots for the first nine weeks of the study but utilization decreased when cattle were introduced to the area. The annual cereal rye yielded the most tons per hectare followed by wheat varieties then the oat and other rye varieties. Apparent ruminal digestibility was determined through the use of fermenters that were randomly assigned to one of the following primary forage source: 1) fescue grass hay (GH); 2) ryegrass (RYE); 3) Buck Master Wheat (BMW); or 4) Buck Forage Oat (BFO). Dry matter digestibility was greater for RYE and BMW compared to GH and BFO. Neutral detergent fiber and CP digestibility were greater for RYE and BMW compared to GH and BFO. All varieties have the ability to extend grazing but more research needs to be done to determine best management practices for common use land areas.

Competition, Nitrogen Use Efficiency, and Productivity of Millet–Soybean Intercropping in Semiarid Conditions

ABSTRACTIncreased frequency of drought and shortage of irrigation water has challenged forage production in arid and semiarid regions. Farmers have shifted from corn (Zea mays L.), as their primary source of forage, to more drought‐tolerant species such as millet (Pennisetum glaucum L.); however, protein content of millet may be too low to meet the needs of high‐producing animals. A 2‐yr field experiment was conducted to determine if mixtures of millet with soybean (Glycine max L.) could produce acceptable forage and protein yield and at the same time maintain farmers' profit level. Main plots consisted of nitrogen (N) rates of 0, 37, and 74 kg N ha−1, and subplots were assigned to intercropping ratios (50:50, 60:40, and 40:60 millet–soybean) along with sole crops. Nitrogen application increased total dry matter yield, and millet sole crop had the highest yield (13.6 t ha−1) followed by 60:40 millet–soybean (13.1 t ha−1). The land equivalent ratio (LER) was highest (1.17) in 60:40 millet–soybean intercrops, indicating 17% more efficient use of land than sole crops. On the basis of the results from LER, relative crowding coefficient, and monetary advantage index, 60:40 millet–soybean was superior to the other intercropping ratios and sole crops. Also, the highest protein yield (2.49 t ha−1) was obtained from 60:40 millet–soybean intercrops. Considering both yield and nitrogen use efficiency, 60:40 millet–soybean intercropping ratio, fertilized at 74 kg N ha−1, was advantageous and could be recommended as an alternative to millet sole crop to produce forage of high quality with no significant yield loss.

Effects of 3-nitrooxypropanol on methane emission, digestion, and energy and nitrogen balance of lactating dairy cows

The objective was to measure effects of 3-nitrooxypropanol (3NP) on methane production of lactating dairy cows and any associated changes in digestion and energy and N metabolism. Six Holstein-Friesian dairy cows in mid-lactation were fed twice daily a total mixed ration with maize silage as the primary forage source. Cows received 1 of 3 treatments using an experimental design based on two 3×3 Latin squares with 5-wk periods. Treatments were a control placebo or 500 or 2,500mg/d of 3NP delivered directly into the rumen, via the rumen fistula, in equal doses before each feeding. Measurements of methane production and energy and N balance were obtained during wk 5 of each period using respiration calorimeters and digestion trials. Measurements of rumen pH (48 h) and postprandial volatile fatty acid and ammonia concentrations were made at the end of wk 4. Daily methane production was reduced by 3NP, but the effects were not dose dependent (reductions of 6.6 and 9.8% for 500 and 2,500mg/d, respectively). Dosing 3NP had a transitory inhibitory effect on methane production, which may have been due to the product leaving the rumen in liquid outflow or through absorption or metabolism. Changes in rumen concentrations of volatile fatty acids indicated that the pattern of rumen fermentation was affected by both doses of the product, with a decrease in acetate:propionate ratio observed, but that acetate production was inhibited by the higher dose. Dry matter, organic matter, acid detergent fiber, N, and energy digestibility were reduced at the higher dose of the product. The decrease in digestible energy supply was not completely countered by the decrease in methane excretion such that metabolizable energy supply, metabolizable energy concentration of the diet, and net energy balance (milk plus tissue energy) were reduced by the highest dose of 3NP. Similarly, the decrease in N digestibility at the higher dose of the product was associated with a decrease in body N balance that was not observed for the lower dose. Milk yield and milk fat concentration and fatty acid composition were not affected but milk protein concentration was greater for the higher dose of 3NP. Twice-daily rumen dosing of 3NP reduced methane production by lactating dairy cows, but the dose of 2,500mg/d reduced rumen acetate concentration, diet digestibility, and energy supply. Further research is warranted to determine the optimal dose and delivery method of the product.

Energy efficiency of growing ram lambs fed concentrate-based diets with different roughage sources

Poor-quality roughages are widely used as fiber sources in concentrate-based diets for ruminants. Because roughage quality is associated with the efficiency of energy use in forage-based diets, the objective of this study was to determine whether differing the roughage source in concentrate-based diets could change the energy requirements of growing lambs. Eighty-four 1/2 Dorper × 1/2 Santa Inês ram lambs (18.0 ± 3.3 kg BW) were individually penned and divided into 2 groups according to primary source of dietary roughage: low-quality roughage (LQR; sugarcane bagasse) or medium-quality roughage (MQR; coastcross hay). Diets were formulated to be isonitrogenous (2.6% N) and to meet 20% of physically effective NDF. After a 10-d ad libitum adaptation period, 7 lambs from each group were randomly selected and slaughtered (baseline). Twenty-one lambs in each diet group were fed ad libitum and slaughtered at 25, 35, or 45 kg BW. The remaining 28 lambs (14 from each diet group) were submitted to 1 of 2 levels of feed restriction: 70% or 50% of the ad libitum intake. Retentions of body fat, N, and energy were determined. Additionally, 6 ram lambs (44.3 ± 5.6 kg BW) were kept in metabolic cages and used in a 6 × 6 Latin square experiment designed to establish the ME content of the 2 diets at the 3 levels of DM intake. There was no effect of intake level on diet ME content, but it was greater in the diet with LQR than in the diet with MQR (3.18 vs. 2.94 Mcal/kg, respectively; P < 0.01). Lambs fed the diet with LQR had greater body fat (g/kg of empty BW) and energy concentrations (kcal/kg of empty BW) because of a larger visceral fat deposition (P < 0.05). Using a low-quality roughage as a primary source of forage in a concentrate-based diet for growing lambs did not change NEm and the efficiency of ME use for maintenance, which averaged 71.6 kcal/kg(0.75) of shrunk BW and 0.63, respectively. On the other hand, the greater nonfibrous carbohydrate content of the diet with LQR resulted in a 17% better efficiency of ME use for gain (P < 0.01), which was associated with a greater partial efficiency of energy retention as fat (P < 0.01). This increased nutritional efficiency, however, should be viewed with caution because it is related to visceral fat deposition, a nonedible tissue.

An Assessment of Current Feeding Practices in Louisiana Dairy Farms

A survey of producers was conducted to determine feeding practices on Louisiana dairy farms. A 38.5% response rate among dairy farmers was obtained. Declared herd size averaged 108 Holstein milking cows producing 15,613 lbs/cow/year. Most producers relied on pastures as primary forage source for the cows. Pastures were supplemented with concentrates offered twice daily. Most farmers formulated rations and reported knowing dietary protein, but less than 20% of the respondents acknowledged dietary P content. Producers and company nutritionists should be targeted by Extension programs intended to inform about P feeding recommendations and environmental effects of excess P.

Dried Distillers Grains Plus Solubles with Corn Silage or Alfalfa Hay as the Primary Forage Source in Dairy Cow Diets

Nine multiparous (250±6 d in milk) and 3 primiparous (204±6 d in milk) Holstein cows were utilized in a 3×3 Latin square design to evaluate the lactation performance of cows fed a diet containing dried distillers grains plus solubles (DDGS) with either corn silage or alfalfa hay as forage. Cows were fed total mixed diets containing corn silage (CS), 50% corn silage and 50% alfalfa hay (CSAH), or alfalfa hay (AH) as the forage source. All diets had a 50:50 forage-to-concentrate ratio, contained 15% DDGS, and were formulated to be equal in metabolizable protein. Dry matter intake increased when cows were fed CSAH (24.9kg/d) compared with CS (21.9kg/d) and AH (20.9kg/d). Yields of milk (26.5, 28.4, 29.0kg/d for CS, CSAH, and AH, respectively) increased linearly as proportions of alfalfa fed increased but 4% fat-corrected milk and energy-corrected milk were not affected by treatment. Feed efficiency (1.28, 1.23, and 1.45kg of energy-corrected milk/kg of intake) improved when AH was fed compared with CS or CSAH. Milk fat concentration (3.67, 3.55, and 3.49%) decreased linearly when alfalfa replaced corn silage, but was observed only in primiparous cows, not multiparous cows. Milk protein concentration (3.32, 3.29, and 3.29%) was not affected by diet although yield (0.90, 0.96, and 0.98kg/d) tended to increase linearly when alfalfa was added to the diet. This may have been due to an increase in essential amino acid (AA) availability and uptake by the mammary gland or to greater crude protein intake in cows fed AH. In addition, replacing corn silage with alfalfa increased the uptake of Lys by the mammary gland. Methionine was the first-limiting AA based on the transfer efficiency of AA in arterial plasma to milk protein. However, Lys was the first-limiting AA in CS and CSAH and Met was first limiting in AH for mammary gland extraction efficiency of AA from plasma. In conclusion, replacing corn silage with alfalfa hay in diets containing 15% DDGS increased milk yield and tended to increase milk protein yield linearly in cows during late lactation. Feeding alfalfa hay as the sole forage source improved feed efficiency compared with diets containing corn silage.

Effect of raw or roasted whole soybeans on early lactational performance and ruminal and blood metabolites in Iranian cows

SUMMARYThe current study evaluated responses of early lactation Iranian Holstein cows to feeding roasted whole soybeans (SB) plus cottonseed meal (CSM), raw SB plus CSM and soybean meal (SBM) plus cottonseed (CS) in diets with lucerne hay and maize silage as the primary forage source. Treatments consisted of a total mixed ration that included 387 g forage/kg, supplemented with: (1) 120 g roasted SB/kg and 82 g CSM/kg, (2) 120 g raw SB/kg and 82 g CSM/kg, or (3) 120 g SBM/kg and 82 g CS/kg on a dry matter (DM) basis. Diets were offered to 14 multiparous Holstein cows (body weight=617·0 kg, days in milk=16·9) that were assigned randomly to one of three experimental diets for a 45-day trial. Dry matter intake (DMI) was significantly higher for the roasted SB plus CSM diet than for the raw SB plus CSM diet but the difference between the SB plus CSM diets and SBM plus CS was not significant. Yields of milk and 35 g fat-corrected milk (FCM)/kg and milk fat were significantly higher for the roasted SB plus CSM diet than for raw SB plus CSM and also for the SB plus CSM diets than for SBM plus CS. Milk protein concentration was significantly increased by about 2·0 g/kg by the SBM plus CS diet, but milk protein yield was the same for cows fed SBM plus CS, roasted SB plus CSM and raw SB plus CSM diets. Rumen ammonia N, plasma urea N (PUN) and milk urea N (MUN) concentrations were lower when the roasted SB plus CSM diet was fed. Ruminal pH and plasma glucose and β-hydroxybutyrate concentrations were not affected by dietary treatments. Plasma concentrations of essential amino acids (EAA), except Leu and Phe, were higher in cows fed the roasted SB plus CSM diet than in those fed raw SB plus CSM. The cows fed the SBM plus CS diet had the same concentrations of EAA, except Phe, as cows fed SB plus CSM diets. For diets based on lucerne hay and maize silage as the primary forage source, roasting of SB provides additional benefits over raw SB.

Protein Level for Alfalfa and Corn Silage-Based Diets: I. Lactational Response and Milk Urea Nitrogen

This study was designed to evaluate lactational responses of cows fed corn silage (CS) or alfalfa silage (AS) as primary forage source when the diet was balanced for recommended (RP) or excessive (HP) amounts of rumen degradable protein (RDP) and undegradable protein (RUP) according to the recommendations of the National Research Council (NRC). A second objective was to evaluate different sources of variations in milk urea N (MUN). The total mixed rations included 55% forage on a dry matter (DM) basis as either 14% CS and 41% AS or 14% AS and 41% CS. Diets were offered to 48 multiparous Holstein cows (body weight = 652kg) that were assigned randomly to treatments arranged as a 2×2 factorial in 12 complete blocks based on calving date. Data collected during wk 4 to 12 of lactation were adjusted to those obtained from a pretreatment diet fed during wk 1 to 3. Crude protein (CP) averaged 16.5, 18.0, 16.2, and 17.1% of DM in the AS-RP; AS-HP; CS-RP; and CS-HP diets, respectively. Overall DM intake (DMI) was 1.5kg/d lower than predicted by NRC (24.6 vs. 26.1kg/d), but 3.5% fat-corrected milk (FCM) was higher than expected (46.1 vs. 45.0kg/d). The responses to a reduction in dietary protein were independent of primary forage source, except for milk true protein (TP) percentage. Primary forage source did not influence DMI, 3.5% FCM, TP yield, or MUN. However, compared with the AS-based diets, cows fed CS-based diets produced more milk (49.0 vs. 46.4kg/d), less fat (3.07% vs. 3.54% and 1500 vs. 1651g/d), and tended to gain more body weight. There were no benefits to feeding diets above NRC protein recommendations, regardless of forage source. Reducing CP from 17.5 to 16.4% of diet DM did not alter milk yield (47.7kg/d) or milk TP yield (1293g/d), but lowered N intake by 65g/d (700 vs. 635g/d) and lowered MUN by 1unit (12.7 vs. 11.7mg/dL). A positive correlation between MUN and production efficiency (3.5% FCM/DMI) on wk 3 of lactation suggested that body protein mobilization might impact MUN in early lactation. The correlation between MUN and DMI tended to be negative in wk 3, but was positive in wk 6 to 12 of lactation. The same was true for the correlation between MUN and somatic cell score. Regression analysis of the postpeak lactation data of this study indicated that the expected MUN was essentially 12mg/dL when NRC-predicted RDP and RUP balances were 0g/d, with a linear deviation of 0.1 and 0.03mg/dL per 10g of change in RDP and RUP balance, respectively.

Protein Level for Alfalfa and Corn Silage-Based Diets: II. Nitrogen Balance and Manure Characteristics

This N balance study was completed with 48 multiparous Holstein cows (body weight [BW]=653kg; days in milk=89) blocked by calving date and assigned to a 2×2 factorial arrangement of dietary treatments. The total mixed ration included alfalfa silage (AS) or corn silage (CS) as the primary forage source (41 and 14% vs. 14 and 41% of diet dry matter (DM), respectively) and were formulated for recommended (RP) or excessive (HP) amounts of rumen degradable protein (RDP) and rumen undegradable protein (RUP) according to the guidelines of the National Research Council (NRC). Crude protein (CP) averaged 16.5, 18.0, 16.4, and 17.3% for the AS-RP; AS-HP; CS-RP; and CS-HP diet, respectively (DM basis). Regardless of primary forage source, the reduction in dietary CP to the NRC guidelines tended to improve milk yield (43.4 vs. 41.0kg/d) but did not alter 3.5% fat-corrected milk (37.0kg/d) or milk true protein yield (1167g/d). In this trial, cows fed the CS-based diets consumed less DM than those fed the AS-based diets in part because of rumen acidosis. The adverse effect of low rumen pH was accompanied by an increase in urinary N (UN) as a percentage of N intake, but did not alter milk yield. Notwithstanding partial confounding, fecal N (FN) was 49g/d lower (213 vs. 164g/d), UN was unchanged (229g/d), but milk N tended to be higher (194 vs. 206g/d) when cows were fed the CS-based diets compared with AS-based diets. Compared with the HP diets, cows fed the RP diets had similar FN (189g/d) and milk N (200g/d), but UN and urine urea N were reduced by 41g/d (249 vs. 208g/d) and 40g/d (210 vs. 171g/d), respectively. Fecal N concentration was higher for CS-based diets, but urinary N concentration was higher for AS-based diets. The reduction in dietary CP did not influence these concentrations but lowered urine volume. The metabolic relationships between energy and protein in determining the fate of excess dietary N (primarily in the form of excess RUP in this trial) was illustrated by a 17% increase in the UN to FN ratio for cows fed AS-HP compared with the AS-RP diet and a 42% increase in the UN to FN ratio for CS-HP compared with CS-RP diet, when cows’ energy status was compromised because of rumen acidosis. In this trial, UN ranged from 150 to 320g/d, and was best predicted as UN (g/d)=0.0283×BW (kg)×milk urea N (mg/dL). The NRC protein guidelines should not be exceeded to avoid unnecessary losses of manure N and, in particular, urine urea N.

Forage Legumes for Sustainable Cropping Systems

SUMMARY Perennial and annual forage legumes are important components of sustainable cropping systems. Forage legumes are a primary source of forage to supply protein and fiber for livestock rations. They can be grazed, or stored as hay or silage. They contribute biologically fixed N and sustain the soil by reducing erosion and increasing soil organic matter levels. Diversifying cropping systems by including legumes can also reduce weed, insect, and disease incidence. Potential new uses of legumes include phytoremediation of N contaminated sites and capturing N lost from cropping systems. Legumes also have potential use as a feedstock for renewable energy production. Legumes have traditionally been used in rotation with grain crops but more recently have been shown promise as winter cover crops, intercrops with grain crops, and as living mulches. In this review, we discuss traditional and new roles of forage legumes in sustainable cropping systems with examples primarily chosen from northern USA and Canada.

Effects of a Live Yeast Culture and Enzymes on In Vitro Ruminal Fermentation and Milk Production of Dairy Cows

Live yeast culture (Saccharomyces cerevisiae) grew best on malt extract agar and required incubation under aerobic conditions to maximize the number of viable cells. In sterile, anaerobic ruminal fluid that had been supplemented with malt extract, yeast cells remained viable and metabolically active for up to 48h, as indicated by the production of ethanol. A supplement containing live yeast and enzymes was fed twice daily with a diet of 50:50 (wt/wt) forage to concentrate (dry matter basis) to continuous fermentors inoculated with mixed ruminal microorganisms. The supplement had no effect on major fermentation acids or pH. After the last supplement with yeast was fed, numbers of yeast immediately decreased in the fermentors and were not detectable after 24h. In the first of two lactation experiments, Holstein cows in midlactation were offered a diet with corn silage as the primary forage source. Half of the cows received a top-dressing based on corn that contained 10 g/d of the yeast and enzyme supplement. The supplement had no effect on milk production, milk composition, or dry matter intake. In a second lactation experiment, high producing cows in early lactation were fed 0, 10, and 20 g/d of the supplement. Cows fed the control diet produced 36.4kg of milk/d, and milk production was 39.3 and 38.0 kg/d from cows fed 10 and 20g of yeast/d, respectively.

Nitrogen Mineralization, Plant Growth and Goose Herbivory in an Arctic Coastal Ecosystem

1 Lesser snow geese feed intensively on graminoid vegetation in intertidal salt marshes at La Perouse Bay, Manitoba. Relatively little grazing occurs in more inland sites, where the same vegetation persists but tidal inundations are infrequent. At some sites geese have grubbed vegetation exposing sediments. 2 Feeding preferences of geese may be linked to the availability of nitrogen for plant growth in the different areas. Total soil nitrogen, exchangeable inorganic nitrogen, net mineralization of nitrogen, together with soil properties, were measured in intertidal and inland sites (both grazed and ungrazed), and in intertidal grubbed sites. Where applicable, rates of net mineralization of nitrogen were compared with aboveground biomass and with the nitrogen content of shoots of graminoids in both grazed and ungrazed (exclosed) swards. 3 All soils were regosolic static cryosols with a thin Ah humus horizon. Most graminoid roots were confined to the top 2 cm of soil, few penetrated deeper than 5 cm. Bulk density of soil 1-2 cm below the surface was 0.87 g cm3 and 0.53 g respectively, in the intertidal and inland marsh, and water content and salinity of soil were higher in the inland marsh. 4 Total nitrogen in soils (0-2 cm below the surface) in the inland marsh was 118 g ? 6g N m-2 compared with 80 + 2 g N m2 in the intertidal marsh. Total soil nitrogen, exchangeable inorganic nitrogen and net mineralization of soil nitrogen were significantly greater beneath intact swards compared with grubbed swards in the intertidal marsh. 5 Seasonal net cumulative amount of nitrogen mineralized in the intertidal marsh (86 days) in 1991 was 0.53 g N m-2 at a soil depth of 1-2 cm. The comparable value for the inland marsh was 0.06 g N m2. In 1992 (54 days) the net amount of nitrogen mineralized in vegetated intertidal sites was 0.18g N m-2 (1-2cm) and in grubbed sites it was 0.06 g N m2. 6 Cumulative above-ground biomass of graminoid species in exclosed plots was greater in the intertidal marsh compared with that in the inland marsh. The amount of nitrogen (as percentage) in above-ground biomass was also higher in plants from the intertidal marsh. 7 Differences in the quantity and quality of vegetation are associated with variation in biogeochemical cycling in soils. Geese exploit patches of vegetation as their primary source of forage where net above-ground primary production is high and plant tissues are rich in nitrogen.