V. S. Baron

Potential of forages to diversify cropping systems in the Northern Great Plains

cated to cultivated forage crop production in the three Canadian prairie provinces (Manitoba, Saskatchewan, Cultivated forage crops are grown on almost 12 million ha on the and Alberta) and three U.S. states (North Dakota, northern Great Plains. This paper reviews the benefits of diversifying annual crop rotations with forage crops and highlights innovations in South Dakota, and Montana) totals 7.8 million ha of forage systems. Agronomic benefits of rotating forage crops with cultivated hay and 3.8 million ha of cultivated pasture annual grain crops include higher grain crop yields following forages (Alberta Agric., Food, and Rural Dev., 1999; Manitoba (up to 13 yr in one study), shifts in the weed population away from Agric. and Food, 1999; Saskatchewan Agric. and Food, arable crop weeds, and improved soil quality. Perennial legumes in 1999; NASS, 1999). Many farmers and ranchers use culrotation also reduce energy requirements by adding significant tivated forages to complement the approximate 44 milamounts of N to the soil. Soil water availability may limit the extent lion ha (Alberta Agric., Food, and Rural Dev., 1999; to which forages benefit following crops. Under semiarid conditions, Manitoba Agric. and Food, 1999; Saskatchewan Agric. forages can actually reduce yields of the following crops, and as such, and Food, 1999; NASS, 1999) of native rangeland in tillage practices that conserve soil water have been developed to this region. partially address this problem. Forages in rotation provide environmental benefits, such as C sequestration, critical habitat for wildlife, Forage is produced and conserved during the short and reduced NO3 leaching. A wider range of annual plant species are growing season and fed during the remainder of the now used in forage systems in an effort to extend the grazing season year. Hay is the predominant winter feed, followed by and to maximize use of water resources. Intensive pasture managestraw, silage, stockpiled perennial pasture, and swathed ment using cultivated forages is on the increase as is the use of alfalfa annual pastures (Small and McCaughey, 1999). The win(Medicago sativa L.) in grazing systems; in some cases, bloat-reduced ter feeding period for beef cattle (Bos taurus) in western alfalfa cultivars are used. Pasture-based systems appear to provide Canada is widely reported to exceed 200 d per year benefits for both animal and human health and arguably the health (Mathison, 1993). However, this varies by region and of the environment. Pasture systems are less nutrient exhausting than year, mainly depending on period of snow cover. In hay systems. As a result, nutrient management strategies will differ Alberta during 1999, the mixed grassland region, most in the following crop. Additional research is required to optimize the role of cultivated pastures in grain-based cropping systems. representative of the NGP area, had an average 155 winter feeding days compared with 201 in the boreal transition zone, which lies to the north of the prairie (Anonymous, 2000). Approximately 10% of forage proF production in the northern Great Plains duction is used for dairy cows located in the NGP region. (NGP) of the USA and Canada involves cultivated Some forage is also exported outside North America and native pasture and hay production. The area dedi[e.g., dehydrated alfalfa cubes and pellets and compacted timothy (Phleum pratense L.) hay]. Very little M.H. Entz, Dep. of Plant Sci., Univ. of Manitoba, Winnipeg, MB, Canada R3T 2N2; V.S. Baron, Agric. and Agri-Food Can., Lacombe forage is typcially imported into this region although reRes. Cent., Lacombe, AB, Canada T4L 1W1; P.M. Carr, North Dakota distribution of forage does occur when localized droughts State Univ., Dickinson Res. and Ext. Cent., 1089 State Ave., Dickinreduce forage supply. son, ND 58601; D.W. Meyer, Dep. of Plant Sci., North Dakota State Alfalfa is the main forage legume and is grown on Univ., Fargo, ND 58105; S.R. Smith, Jr., Dep. of Crop, Soil, and 61% of cultivated forage hayland in the U.S. NGP. AlEnviron. Sci., 424 Smyth Hall, Virginia Tech, Blacksburg, VA 240610404; and W.P. McCaughey, Agric. and Agri-Food Can., Brandon falfa’s role in grazing systems is increasing (Smith and Res. Cent., Brandon, MB, Canada R7A 5Y3. Received 22 Jan. 2001. *Corresponding author (m_entz@umanitoba.ca). Abbreviations: CLA, conjugated linoleic acid; DM, dry matter; NGP, northern Great Plains. Published in Agron. J. 94:240–250 (2002). ENTZ ET AL.: DIVERSIFYING CROPPING SYSTEMS WITH FORAGES IN THE NORTHERN GREAT PLAINS 241 Singh, 2000). Other forage legumes are also grown 50% higher from land previously cropped to alfalfa for 3 yr than from land previously cropped to nonlegumes where alfalfa is not adapted [e.g., red clover (Trifolium pratense L.) and alsike clover (T. hybridium L.) in wetter such as corn (Zea mays L.), wheat, or flax (Linum usitatissimum L.). Similar results continue to be reported from and acid soil zones, sainfoin (Onobrychis viciafolia L.) in dryland pastures, or where a nonbloating legume is studies at Melfort, SK (Campbell et al., 1990); Winnipeg, MB (Poyser et al., 1957); and Lethbridge, AB (Ellert, desired]. There is significant potential to utilize these better adapted, alternative perennial forage legumes in 1995) as well as from two ongoing classical long-term studies of crop rotation in western Canada: The Univerthe region though grower education is required. Many different grass species are used in cultivated forage syssity of Alberta’s Breton Plots (initiated in 1930) (Ellert, 1995) and Agriculture and Agri-Food Canada’s longtems, ranging from the droughtand salt-tolerant wheatgrasses (Agropyron spp.) to flooding-tolerant reed caterm study at Indian Head, SK (initiated in 1958) (Campbell et al., 1990). narygrasses (Phalaris spp.). Many annual C3 and C4 plant species are used to fill gaps in the feed supply (Kilcher In a survey of Manitoba and Saskatchewan forage producers, 71% of respondents indicated higher grain and Heinrichs, 1961; Baron et al., 1992; Carr et al., 1998). Forage is defined as, “any plant whose vegetation is yields after forages than in annual crop rotations (Entz et al., 1995). Rotational yield benefits were greatest in eaten by livestock” (Heath et al., 1973), and as such, many different plants are used, including crop residues eastern and northern zones and lowest in drier, western and southern zones. In one of the best studies ever (e.g., corn stalks and chaff) and hay harvested for remnant areas and roadside ditches. These forage sources published on the long-term residual yield benefits of including forage in a cropping system (McLennan, AB), are especially important in drought years such as 2000 in Montana. Forage seed production is also an important Hoyt (1990) reported that for the first 8 yr after forage termination, wheat yields were 66 to 114% greater after industry in the region though it occupies a relatively small area compared with forage production. forage relative to continuous wheat. Yield differences started to decline after 8 yr although wheat yields in The percent of arable cropland that is rotated with forage ranges from 5 to 15% in the region. Two recent the alfalfa systems were still higher (P 0.05) than the control in the 10th and 13th year after sward breaking. surveys have characterized forage and beef production in western Canada (Entz et al., 1995; Small and McIn areas of the NGP where water seriously limits crop productivity, inclusion of perennial forages can reduce Caughey, 1999). Objectives of this paper are to (i) review agronomic, crop yield in following crops due to forage-induced drought. Working in west-central Saskatchewan, Brandt economic, and environmental benefits and risks of diversifying cropping systems with forage crops; (ii) idenand Keys (1982) determined that available soil water in spring was lower after a 2-yr alfalfa crop than in a tify means to enhance the positive attributes of forages in NGP cropping systems and to make forages a more continuous grain rotation. A full year of fallow was insufficient to fully replenish the soil profile with water important component of the cropping system; and (iii) highlight research challenges for the future. in the alfalfa system relative to the grain system. In central Saskatchewan, Austenson et al. (1970) reported that alfalfa in rotation depressed wheat yield in the first ROTATIONAL BENEFITS OF FORAGES crop after breaking even after a full year of summer IN THE NORTHERN GREAT PLAINS fallow. Interestingly, they observed that alfalfa with CROPPING SYSTEMS bromegrass (Bromus inermis Leyss.) or bromegrass Forage benefits have received less attention in the alone did not affect wheat yields significantly. Others NGP than elsewhere, such as the humid U.S. Midwest (e.g., C.A. Campbell, personal communication, 2000) where alfalfa has traditionally been rotated with grain have suggested that low cereal yields after alfalfa could crops or areas of Australia where unique, self-regeneratbe due to allelopathic effects from alfalfa, and such ing forage species are grown in grain-based cropping effects are greatest under dry soil conditions. However, systems (Grace et al., 1995). The short growing season no studies have been conducted to substantiate this sugand relatively dry conditions (i.e., low precipitation and gestion. high evaporative demand for water) in the NGP will In wetter areas of the NGP, these water-depleting modify rotational benefits of forages relative to wetcharacteristics of alfalfa and other perennial forages are ter areas. often viewed as desirable. For example, dewatering Some of the best information on forage rotational characteristics of perennial forages play an important benefits in the NGP has come from long-term crop role in soil salinity management. Soil salinization is a rotation studies, many of which were established soon threat to the long-term sustainability of cro

Productivity, Respiration, and Light-Response Parameters of World Grassland and Agroecosystems Derived From Flux-Tower Measurements

Abstract Grasslands and agroecosystems occupy one-third of the terrestrial area, but their contribution to the global carbon cycle remains uncertain. We used a set of 316 site-years of CO2 exchange measurements to quantify gross primary productivity, respiration, and light-response parameters of grasslands, shrublands/savanna, wetlands, and cropland ecosystems worldwide. We analyzed data from 72 global flux-tower sites partitioned into gross photosynthesis and ecosystem respiration with the use of the light-response method (Gilmanov, T. G., D. A. Johnson, and N. Z. Saliendra. 2003. Growing season CO2 fluxes in a sagebrush-steppe ecosystem in Idaho: Bowen ratio/energy balance measurements and modeling. Basic and Applied Ecology 4:167–183) from the RANGEFLUX and WORLDGRASSAGRIFLUX data sets supplemented by 46 sites from the FLUXNET La Thuile data set partitioned with the use of the temperature-response method (Reichstein, M., E. Falge, D. Baldocchi, D. Papale, R. Valentini, M. Aubinet, P. Berbigier, C. Bernhofer, N. Buchmann, M. Falk, T. Gilmanov, A. Granier, T. Grünwald, K. Havránková, D. Janous, A. Knohl, T. Laurela, A. Lohila, D. Loustau, G. Matteucci, T. Meyers, F. Miglietta, J. M. Ourcival, D. Perrin, J. Pumpanen, S. Rambal, E. Rotenberg, M. Sanz, J. Tenhunen, G. Seufert, F. Vaccari, T. Vesala, and D. Yakir. 2005. On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm. Global Change Biology 11:1424–1439). Maximum values of the quantum yield (α  =  75 mmol · mol−1), photosynthetic capacity (Amax  =  3.4 mg CO2 · m−2 · s−1), gross photosynthesis (Pg,max  =  116 g CO2 · m−2 · d−1), and ecological light-use efficiency (εecol  =  59 mmol · mol−1) of managed grasslands and high-production croplands exceeded those of most forest ecosystems, indicating the potential of nonforest ecosystems for uptake of atmospheric CO2. Maximum values of gross primary production (8 600 g CO2 · m−2 · yr−1), total ecosystem respiration (7 900 g CO2 · m−2 · yr−1), and net CO2 exchange (2 400 g CO2 · m−2 · yr−1) were observed for intensively managed grasslands and high-yield crops, and are comparable to or higher than those for forest ecosystems, excluding some tropical forests. On average, 80% of the nonforest sites were apparent sinks for atmospheric CO2, with mean net uptake of 700 g CO2 · m−2 · yr−1 for intensive grasslands and 933 g CO2 · m−2 · d−1 for croplands. However, part of these apparent sinks is accumulated in crops and forage, which are carbon pools that are harvested, transported, and decomposed off site. Therefore, although agricultural fields may be predominantly sinks for atmospheric CO2, this does not imply that they are necessarily increasing their carbon stock.

Relationships between progeny residual feed intake and dam productivity traits

Two hundred and twenty-two yearling calves and their dams were used to examine the phenotypic (rp) relationships between progeny residual feed intake (RFI) and maternal productivity across 10 production cycles. Progeny RFI ranged from -3.95 to +2.72 kg as fed d-1 (SD = 0.94), while RFI adjusted for off-test backfat thickness (RFIadj), ranged from -2.48 to +1.53 kg as fed d-1 (SD = 0.88). Progeny RFI and RFIadj were unrelated to on-test age, body weight, growth rate, and ultrasound longissimus thoracis area and positively related to feed intake (rp = 0.51 to 0.53; P < 0.001), feed to gain ratio (rp = 0.44 to 0.46; P < 0.001), feeding behaviour traits (rp = 0.29 to 0.36; P < 0.001) and cow RFI (rp = 0.30, P < 0.05). Progeny RFI was positively related to measures of body fat (rp = 0.21 to 0.27; P < 0.05), but these relationships disappeared when RFI was adjusted for off-test backfat thickness. Cows that had produced LOW (≤ 0.5 SD), MEDIUM (± 0.5 SD) or HIGH (≥ 0.5 SD) RFIadj progeny were similar in pregnancy...

CONJUGATED LINOLEIC ACID-ENRICHED BEEF PRODUCTION

Canadian beef consumption is approximately 31 kg per annum, or a third of all meats consumed. Beef is a nutrient-rich food, providing good quality protein, vitamins B-6 and B-12, niacin, iron, and zinc. However, animal fats have gained the reputation of being less healthy. The identification of the anticarcinogenic effects of beef extracts due to the presence of conjugated linoleic acid (CLA) has heightened interest in increasing the amount of CLA deposited in beef. Beef cattle produce CLA and deposit these compounds in the meat; thus, beef consumers can receive bioformed CLA. Beef contains both of the bioactive CLA isomers, namely, cis-9, trans-11 and trans-10, cis-12. The relative content of these CLA isomers in beef depends on the feeds consumed by the animals during production. Feeding cattle linoleic acid-rich oils for extended periods of time increases the CLA content of beef. Depending on the type and relative maturity of the pasture, beef from pasture-fed cattle may have a higher CLA content than beef from grain- or silage-fed cattle. In feedlot animals fed high-grain diets, inclusion of dietary oil along with hay during both the growth and finishing phases led to an increase in CLA content from 2.8 to 14 mg/g beef fat, which would provide 77 mg CLA in an 85-g serving of beef. The CLAs appear to be concentrated in intramuscular and subcutaneous fat of beef cattle, with the CLA trans-10, cis-12 isomer being greater in the subcutaneous fat.

Alternative fall and winter feeding systems for spring calving beef cows

This study evaluated the effects of early (EW) and late (LW) weaning on calf post-weaning growth performance and carcass characteristics. It also quantified the effects of EW and LW in combination with three winter feeding strategies on cow growth, reproductive performance and cost of production. EW calves were weaned in late August, while LW calves were weaned 56 d later in late October. The three cow winter feeding strategies were: (1) traditional (TD), or straw fed ad libitum and barley (Hordeum vulgare L.) silage fed every day; (2) alternate day (AD), or straw fed ad libitum and equivalent amounts of barley silage fed every second day (AD); and (3) swath graze (SG), or swath grazing whole-plant barley, cut in the soft dough stage. The study was conducted over three production cycles (1997/1998, 1998/1999 and 1999/2000). EW calves weighing 213 kg and fed a backgrounding diet (82% barley silage: 18% concentrate) for 56 d, grew 0.36 kg d-1 (EW = 0.61 ± 0.02 kg d-1; LW = 0.97 ± 0.02 kg d-1; P < 0.001) slo...

Reducing GHG emissions through genetic improvement for feed efficiency: effects on economically important traits and enteric methane production

Genetic selection for residual feed intake (RFI) is an indirect approach for reducing enteric methane (CH4) emissions in beef and dairy cattle. RFI is moderately heritable (0.26 to 0.43), moderately repeatable across diets (0.33 to 0.67) and independent of body size and production, and when adjusted for off-test ultrasound backfat thickness (RFIfat) is also independent of body fatness in growing animals. It is highly dependent on accurate measurement of individual animal feed intake. Within-animal repeatability of feed intake is moderate (0.29 to 0.49) with distinctive diurnal patterns associated with cattle type, diet and genotype, necessitating the recording of feed intake for at least 35 days. In addition, direct measurement of enteric CH4 production will likely be more variable and expensive than measuring feed intake and if conducted should be expressed as CH4 production (g/animal per day) adjusted for body size, growth, body composition and dry matter intake (DMI) or as residual CH4 production. A further disadvantage of a direct CH4 phenotype is that the relationships of enteric CH4 production on other economically important traits are largely unknown. Selection for low RFIfat (efficient, −RFIfat) will result in cattle that consume less dry matter (DMI) and have an improved feed conversion ratio (FCR) compared with high RFIfat cattle (inefficient; +RFIfat). Few antagonistic effects have been reported for the relationships of RFIfat on carcass and meat quality, fertility, cow lifetime productivity and adaptability to stress or extensive grazing conditions. Low RFIfat cattle also produce 15% to 25% less enteric CH4 than +RFIfat cattle, since DMI is positively related to enteric methane (CH4) production. In addition, lower DMI and feeding duration and frequency, and a different rumen bacterial profile that improves rumen fermentation in −RFIfat cattle may favor a 1% to 2% improvement in dry matter and CP digestibility compared with +RFIfat cattle. Rate of genetic change using this approach is expected to improve feed efficiency and reduce enteric CH4 emissions from cattle by 0.75% to 1.0% per year at equal levels of body size, growth and body fatness compared with cattle not selected for RFIfat.

Soil compaction under grazing of annual and perennial forages

This study investigated the impact of heavy, medium and light grazing of meadow bromegrass an triticale on soil bulk density, relative compaction and penetration resistance. The study was conducted at Lacombe, Alberta, on a Orthic Black Chernozem of loam to silt loam texture. Sampling was conducted in fall 1995, spring 1996, fall 1996 and spring 1997. Core samples to a 15-cm depth were collected for measurement of bulk density and moisture content. Penetration resistance to 15 cm was measured with a hand-pushed cone penetrometer. The standard Proctor test was used to determine maximum bulk density. Relative compaction was the ratio of actual bulk density to the Proctor maximum bulk density expressed as a percentage. Surface (0–2.5 cm) bulk density and penetration resistance were significantly greater under heavily grazed than under medium and lightly grazed meadow bromegrass only for fall 1995. Differences in bulk density, relative compaction and penetration resistance for different grazing intensities in...

Effects of vitamin E and flaxseed on rumen-derived fatty acid intermediates in beef intramuscular fat☆

To elucidate the effects of dietary vitamin E with or without flaxseed on beef fatty acid composition, 80 feedlot steers were fed 4 diets: Control-E (451 IU dl-α-tocopheryl acetate/head/day), Control+E (1051 IU dl-α-tocopheryl acetate/head/day), Flax-E (10% ground) and Flax+E. Vitamin E had no effect on animal growth or carcass weight (p>0.05), while flaxseed-fed steers had greater average daily gain (p=0.007), final live weight (p=0.005) and heavier carcasses (p=0.012). Feeding flaxseed increased the total n-3 fatty acid content of beef and this response was further accentuated by the inclusion of high levels of vitamin E in the diet. Feeding flax increased levels of some 18:3n-3 partial hydrogenation products including c15- and t13/14-18:1 and several 18:2 isomers (p<0.001) but decreased t10-18:1 (p<0.001). Vitamin E enhanced intramuscular levels of 18:3n-3 and its biohydrogenation products leading to greater accumulations of total n-3 fatty acids in lean ground beef. The consequences of increasing the concentrations of partially hydrogenated products on human health have yet to be investigated.

Effects of feeding flaxseed or sunflower-seed in high-forage diets on beef production, quality and fatty acid composition.

Yearling steers were fed 70:30 forage:concentrate diets for 205 d, with either grass hay (GH) or red clover silage (RC) as the forage source, and concentrates containing either sunflower-seed (SS) or flaxseed (FS), each providing 5.4% oil to diets. Feeding diets containing SS versus FS significantly improved growth and carcass attributes (P<0.05), significantly reduced meat off-flavor intensity (P<0.05), and significantly increased intramuscular proportions of vaccenic (t11-18:1), rumenic (c9,t11-CLA) and n-6 fatty acids (FA, P<0.05). Feeding diets containing FS versus SS produced significantly darker and redder meat with greater proportions of atypical dienes (P<0.05). A significant forage × oilseed type interaction (P<0.05) was found for n-3 FA, α-linolenic acid, and conjugated linolenic acid, with their greatest intramuscular proportions found when feeding the RC-FS diet. Feeding GH versus RC also significantly improved growth and carcass attributes, sensory tenderness (P<0.05) and significantly influenced intramuscular FA composition (P<0.05), but overall, forage effects on FA profiles were limited compared to effects of oilseed.

Evidence of residual feed intake reranking in crossbred replacement heifers

The objective of the study was to examine whether residual feed intake (RFI) reranking exists between 2 consecutive periods in replacement heifers fed the same diet. The study collected feed intake and BW data from 190 crossbred heifers over a 3-yr period (61 in 2007, 68 in 2008, and 61 in 2009) during the winter-spring season. The heifers were fed a roughage-based diet (90% barley silage and 10% rolled barley grain) throughout the feeding trial, which was broken down into 2 feeding periods with ADG of 0.94 and 0.90 kg•d(-1) in the first and second periods, respectively. The RFI was calculated for the entire period using different models, which included ADG, mid-metabolic BW, body composition, and feeding activity. Gain:feed ratio and Kleiber ratio were also calculated. Rank correlations among the RFI calculated from different models were obtained, as well as rank correlations between the 2 feeding periods for the feed efficiency measures. Including body composition and feeding activity only improved the R(2) by 1 to 5%. The rank correlations among the different models were high (90 to 95%) for RFI calculated for the entire feeding period. However, the RFI calculated within the second feeding period had greater rank correlation than the RFI calculated from the entire feeding period. Compared with G:F and Kleiber ratio, RFI gave lesser reranking between periods 1 and 2. About 49% of the heifers maintained their RFI class, whereas 51% of the heifers had a different RFI class in period 2. Furthermore, 41% of the heifers changed their RFI in period 2 by <0.5 SD, whereas the rest of the heifers changed by ≥0.5 SD. These results indicate that reranking exists in heifers despite receiving the same diet in the 2 feeding periods and that the reranking may be more serious in heifers (28%) with extreme RFI performances in each period.