Trop Anim Health Prod (2009) 41:827–834 DOI 10.1007/s11250-008-9258-7
ORIGINAL PAPER
Intercropped oats (Avena sativa) - common vetch (Vicia sativa) silage in the dry season for small-scale dairy systems in the Highlands of Central Mexico Y. Garduño-Castro & A. Espinoza-Ortega & C. E. González-Esquivel & B. Mateo-Salazar & C. M. Arriaga-Jordán
Accepted: 21 October 2008 / Published online: 11 November 2008 # Springer Science + Business Media B.V. 2008
Abstract Small-scale dairy systems in the highlands of central Mexico require feeding strategies based on quality home-grown forage that may reduce high concentrate costs. Eight Holstein cows paired by parity and date of calving were used in a split-plot experiment to evaluate supplementing 6 kg DM/cow/d of oat-vetch silage (OVS) in comparison to maize silage (MS) as dry season feeding, for a more intensive use of the land through an oat-vetch catch crop. Cows had 9 h/d access to continuous grazing of perennial ryegrass – white clover pasture and 4 kg/d of commercial concentrate. The 9 week experiment, recorded weekly milk yield and composition, and body condition score and live-weight every fortnight. Milk yield was 20.1 kg/cow/d for OVS and 15.4 for MS (SEM ±2.9, P>0.05), with no differences for fat or protein content, body condition score, or live-weight (P>0.05). The economic analysis showed that although feeding costs were higher for OVS, margins were Y. Garduño-Castro : A. Espinoza-Ortega : C. E. González-Esquivel : B. Mateo-Salazar Centro de Investigación en Ciencias Agropecuarias (CICA), Toluca, México C. M. Arriaga-Jordán (*) Secretaría de Investigación y Estudios Avanzados, Universidad Autónoma del Estado de México, Instituto Literario # 100, 50000 Toluca, Estado de México, México e-mail:
[email protected]
greater than for MS, with feeding cost per litre of $0.21 for MS and $0.16 for OVS. OVS is a viable catch crop after the MS harvest that can substitute MS in the dry season enabling a more intensive use of the land. Keywords Dry season feeding . Oats – vetch silage . Maize silage . Grazing . Small-scale dairy systems . Highlands . Mexico Abbreviations ADF Acid Detergent Fibre ADL Acid Detergent Lignin CP Crude Protein DM Dry Matter m.a.s.l. metres above sea level NHA Net Herbage Accumulation NDF Neutral Detergent Fibre OM Organic Matter SEM Standard Error of the Mean
Introduction Small-scale campesino dairy systems in the highlands of central Mexico have herds with 3 to 20 cows plus replacements in small farms (< 6.0 ha), and are considered an option to alleviate poverty given their capacity to generate daily incomes and occupation. These systems face frosts from October to early March and have traditionally relied on one long cycle
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crop of maize for grain, moving to small-scale dairying given its potential for productive use of land (Espinoza-Ortega et al. 2007). The small size of farms calls for the intensive use of the land, particularly where some irrigation is available; here intensively grazed perennial temperate pastures have shown their potential, complemented with conserved forages in the winter-spring dry season when there are low growth rates of pasture, and ensiled maize has also shown good results (Arriaga-Jordán et al. 2002). Availability of irrigation allows a forage catch crop to be sown between the harvest of maize forage in October, and the planting of the new maize crop in spring. Small-grain winter cereals like oats may be an option given their winter hardiness and short growth cycle. Double cropping of forages for dairy farms has been promoted over the past decades in other countries like in the American Midwest, where growing small grain forage for silage followed by warm season forages enables two forage crops per year in Illinois. Jaster et al. (1985) described a double cropping system involving oats sown in early spring and harvested in late spring or early summer and the land immediately replanted with sorghum, to be harvested in the fall. Integrating a double crop for conserved forage in campesino systems coupled with the land destined to perennial pasture would enable full use of available land resources. It has been shown that the higher reliance in home-grown forage results in lower production costs and a better economic performance of these systems (Espinoza-Ortega et al. 2007). There is no vast experience in Mexico on the use of silages from small grain forages for dairy cattle feeding; since oats and other cereals like barley (Hordeum vulgare) or triticale (X. Trititicosecale Witt) are usually utilised as green chop or hay. NavarroGarza et al. (2007) evaluated oats as cover crop in the central highlands and recorded a mean DM yield at 70 days post sowing of 6,405 kg DM/ha. Intercropping of oats with common vetch (Vicia sativa L.) is common practice in Mexico as it is in other countries (e.g. Haj-Ayed et al. 2000; Assefa and Ledin 2001; Lauriault and Kirksey 2004); since the legume component is sought to improve yield and protein content of the final forage (Anil et al. 1998). There is a need to evaluate silage from oats intercropped with vetch in the dry season feeding of
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dairy cows in small-scale production systems so that the objective was to assess the inclusion of silage from an oat - common vetch intercrop in the dry season feeding of dairy cows under grazing of perennial ryegrass (Lolium perenne) – white clover (Trifolium repens) pasture at high stocking rates, and receiving moderate amounts of concentrate, in comparison with the use of maize silage; since preliminary work showed promising results (Guadarrama-Estrada et al. 2007).
Materials and methods The study was undertaken in the campesino village of Ejido San Cristóbal located in the central highlands of Mexico at 19° 24′ N and 99° 51′ W, an altitude of 2,650 m.a.s.l., a subhumid temperate climate with a mean annual temperature of 13°C, summer rains (May – October) and an annual rainfall between 800 and 1,000 mm with less than 5% of rains in winter, where a demonstration module in appropriate feeding strategies for small dairy herds has been established between the university and the community. Oat – vetch crop The land was ploughed and harrowed in late January, and oat – vetch sown on 14 February on 1.5 ha after a flood irrigation, broadcasting 100 kg of a local variety of oat seed (Avena sativa) and 40 kg of a local variety of common vetch seed (Vicia sativa) per ha, and fertilised at sowing with 46 kg N – 46 kg P2O5 – 48 kg K. Ensiling took place on 12 May at the dough stage, harvesting 88 days after sowing with a forage harvester and placed in a 1.5× 3 × 10 m trench silo excavated in the ground, compacting the herbage with a tractor, added with 200 ℓ of molasses diluted at 1: 1 with water to increase soluble carbohydrate concentration to enhance fermentation, and covered with a 600 calibre black plastic sheet and soil. Maize crop After harvesting the oat crop, the land was ploughed, harrowed, irrigated and sown on 28 May following farmers’ procedures with 36 kg of a local early maturing variety. Fertilising with urea, triple super
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phosphate, and potassium chloride applied at sowing, and a second dose of urea was applied following local practice at the first mechanical cultivation 30 days postsowing. The second cultivation was 60 after sowing. Herbicides were also applied at sowing and at the first cultivation. Maize growth was less than obtained when sown by early April as is usual practice. Two quadrants of 5 m long × 7 rows deep (approximately 6 m) were located randomly after sowing, to determine forage maize yield. The total forage mass was collected from the two 30 m2 quadrants and maize forage yield expressed as kg DM/ha. Harvesting took place when the grain was in the hard dough stage on 3 November, 159 days after sowing, and ensiled in a trench silo following similar procedures as for the oat-vetch, but no molasses was added. The feeding experiment started after two months of ensiling the maize. Grazing pastures The pasture was 1.5 ha sown on 16 May 1999 to perennial ryegrass (Lollium perenne cv Nui), intermediate ryegrass (L. perenne × L.multiflorum cv. Tama), and white clover (Trifolium repens cv. Pitaw). It was irrigated and fertilised every 28 days with 27.6 kg N/ha, and every six months with 46 kg P2O5 and 60 kg K/ha. Stocking rate was 5.3 cows/ha. Net herbage accumulation (NHA) (kg OM/ha) of the pasture was estimated every 28 days using ten grazing exclusion cages (2.5×0.5×0.7 m), five on each plot, and a metal quadrant of 0.50 m2 (0.25× 2.0 m) (Hodgson 1990). Cages were distributed at random at the beginning of the experiment and every 21 days thereafter. Grass was cut to ground level using hand shears. Samples were dried in a draught oven at 65 C – 75 °C to constant weight to determine dry matter (DM) and NHA was estimated by difference between day 21 and day 1. A sub-sample was ground and ashed at 600 °C for three hours in a muffle furnace to express results of NHA as organic matter (OM)/ha. The pasture received limited flood irrigation every 28 days during the dry season, totalling 5 irrigations. Hand plucked samples of herbage were taken randomly every 28 days simulating grazing for chemical analyses of Neutral Detergent Fibre (NDF), Acid Detergent Fibre (ADF) and Acid Detergent Lignin following the procedures of Ankom Technology (2005), Kjeldahl
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Crude Protein, and Organic Matter by ashing at 600°C in a muffle furnace. Experimental cows Eight multiparous Holstein dairy cows were paired according to date and number of calving and mean daily yield before the experiment. Days in milk were between 10 and 173 d with mean milk yields of 16.6 kg/cow/day. Cows had access to continuous grazing for 9 hours (6:00 to 15:00 h) between the morning (4:00 h) and afternoon milking (15:00 h), and had access to drinking water at pasture. Silages and 4.0 kg of commercial dairy concentrate were fed at milking times, and the cows stayed overnight in a tie stall. Milk yield was recorded (kg/cow/day) for four consecutive milkings at the end of each week; and milk samples were taken to determine milk fat and protein concentration (g/kg) every 14 days from the morning milking. Liveweight (kg/cow) was recorded every 14 days using a portable weigh bridge, when body condition score (Edmonson et al. 1989) was also recorded. Treatments Treatments were: Maize silage (MS): Continuous grazing for 9 h/day, 4.0 fresh basis of commercial dairy concentrate (18% CP) and 6 kg DM of maize silage. Oat-vetch silage (OVS): Continuous grazing for 9 h/day, 4.0 fresh basis of commercial dairy concentrate (18% CP) and 6 kg DM of oat-vetch silage. Samples of silages and concentrate were taken every 14 d for chemical analysis. Economic analysis Partial budgets were used to compare feeding costs between the two silage treatments, considering the costs and returns for the treatments including the cost of pasture, concentrates, and all silage costs comprising land preparation, seed, irrigation (OVS), fertilisers, sowing, mechanical cultivations and herbicides (MS), and ensiling. This method has been used successfully in the economic analysis of campesino dairy production systems in Mexico (Espinoza-Ortega et al. 2007).
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Statistical analysis Data were analysed as a random split-plot design where treatments (MS or OVS silage feeding) were main plots, and weeks were random effects (splitplots) according to the following model (Mead et al. 2002): Yijkl ¼ m þ bi þ Tj þ Ek þ pl þ Tpjl þ eijk Where: μ b T E p
Tp e
General mean Effect of Blocks (cow paired by days in milk) i=1,2,3,4 Effect of silage treatment (Main Plot) j=1, 2 Error term for Main Plots [b(T)ij] Effect of measurement periods (weeks or periods) (split - plot) k=1,..., 9 (or 4 periods for live weight and condition score) Interaction term between Feeding Strategy and Measurement Period Error term for split plots
Results The experiment took place in the spring dry season, beginning on 18th March and ending on 13 May 2005, with a total duration of 9 weeks. Weather conditions Mean temperature over the experiment was 13.4°C, with a mean maximum of 23.4°C and a mean minimum of 3.4°C, with some nights recording frost. Accumulated rainfall was 20 mm. Weather variables fall within historic records for the study area. Net Herbage Accumulation (NHA) and chemical composition of grazed herbage NHA of the grazed pasture over the 9 experimental weeks was 3,655.5 kg OM/ha with a mean of 63.7 kg OM/ha per day and 11.9 kg OM/cow/day. NHA was lowest for measurement Period 1 with only 801.6 kg OM/ha or 38.2 kg OM/ha/day. However, NHA increased for Period 2 at 1,636.9 kg OM/ha or
77.9 kg OM/ha/day, and declines slightly for Period 3 to 1,127.0 kg OM/ha or 53.7 kg OM/ha per day. Chemical composition of feeds is shown in Table 1.
Milk yield and composition Table 2 shows the results for milk yield. Mean milk yield was 17.8 kg/cow/day, with no significant differences between MS and OVS (P>0.05) due to large variation despite the higher yield in the OVS treatment. In both treatments, milk yields were stable with little change over the nine experimental weeks. Differences between periods were also no significant, as well as the interaction which was not significant (P>0.05). There were no differences for milk fat or protein content, body condition score or live-weight changes (P>0.05) (Table 2), and the effect of Periods or the interaction were also not significant (P>0.05). Economic analysis The cost of MS per hectare was 7% higher than for OVS, but MS yield, although low, was 2.2 times higher than for OVS (8,418 kg DM/ha in MS vs. 3,841 kg DM/ha for OVS). Therefore, the cost per kg of DM was US$ 0.051/kg DM for MS while US$ 0.104/kg DM for OVS (Table 3). The economic analysis of milk production over feed costs (Table 4) showed a lower cost per litre of milk for OVS, despite higher feeding costs than for the MS treatment. Although milk yield was not statistically different between treatments due to high variation, the higher milk yield recorded for cows on OVS resulted in significantly higher returns for milk sales, which meant margins 36% higher than for the MS treatment. The ratio of returns over feeding costs Table 1 Chemical composition (g/kg DM) of maize silage (MS), oat-vetch silage (OVS), grazed pasture and commercial concentrate
Organic matter Crude protein Neutral detergent fibre Acid detergent fibre Acid detergent lignin
MS
OVS
Grazed Pasture
Concentrate
886.4 75.2 641.1 415.6 108.2
800.8 100.8 419.1 316.1 124.1
886.5 210.0 517.2 310.8 120.9
939.5 179.6 368.3 148.7 53.7
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Table 2 Milk yield, milk composition, live-weight and body condition score
Milk yield (kg/cow/d) Milk fat (g/kg) Protein (g/kg) Live weight (kg) Body condition score
MS
OVS
SEM
15.4 29.9 31.9 476.0 1.7
20.1 27.4 30.7 533.7 1.7
2.9 ns 2.0 ns 0.72 ns 69.98 ns 0.1 ns
ns=p>0.05.
was very high and favourable for both treatments, although higher for the OVS treatment.
Discussion Climatic conditions Recorded temperatures were within normal ranges for the area and time of year, with temperatures under 6°C at night and frost during four days, which hinder herbage growth in winter and early spring, particularly the clover component of pastures. Chemical composition of feeds Hand plucked pasture was of good quality, with a composition similar to that observed in other work in the area (Guadarrama-Estrada et al. 2007) and similar
to that reported from England under continuous grazing (Hernández-Mendo and Leaver 2006). Intensive use of the land, with two crops per year, meant that the maize was sown on 28th May after the OVS was harvested; 60 days later than usual practice. Therefore, an early maturing variety was sown instead of the usual long cycle varieties used by local farmers (sown in late March or early April). The ensuing MS showed similar CP contents, but higher ADF and ADL contents than other observations in the area with long cycle maize varieties (Guadarrama-Estrada et al. 2007; Anaya-Ortega et al. 2008). MS also had a similar protein content to that reported by Phipps et al. (2000) with 303 g DM/kg and 74 g CP/kg DM. However, MS had almost 50% more NDF and 82% more ADF. The suboptimal growing conditions due to late sowing, and the use of a short cycle variety, resulted in a low yielding, poor quality, fibrous maize silage crop, which may explain the lower productive response from that observed in other work (Guadarrama-Estrada et al. 2007; Anaya-Ortega et al. 2008). OVS had higher CP content than MS, reflecting the advantage of the cereal-legume intercrop; and a lower NDF and ADF content which explains the better animal response. Chemical composition of OVS was similar to several of the hay samples evaluated by Haj-Ayed et al. (2000), and much lower in NDF than the oat-vetch hays reported by Assefa and Ledin (2001) from the highlands of Ethiopia. OVS was also lower in NDF and ADF than that reported by Guadarrama-Estrada et al. (2007) from a parallel work. The lower fibre content of OVS
Table 3 Silage costs CONCEPT
MS
OVS
Silages Land preparation and sowing Seeds Fertilisers Mechanical cultivations Irrigation Herbicides Silage making (hiring in machinery and labour) Others: Molasses Total Silage Costs
(US$/ha) $ 117.00 $ 42.00 $ 102.00 $ 54.00 $ 0.00 $ 32.00 $ 81.00
(US$/ha) $ 95.00 $ 94.00 $ 72.00 $ 0.00 $ 36.00
DM Yield Silage Cost/kg DM
$ 428.00 (kg DM/ha) 8,418 (US$/kg DM) $ 0.051
$ 81.00 $ 20.00 $ 398.00 (kg DM/ha) 3,481 (US$/kg DM) $ 0.104
Table 4 Economic analysis (US dollars)
Feeding costs Concentrate Silage Pasture Total Returns Milk produced (ℓ) Sale price ($/ℓ) Income from milk sales Margin over feed costs Returns/ Feeding Cost Ratio ($) Feeding Cost ($/ℓ)
MS
OVS
$ $ $ $
$ $ $ $
226.04 76.88 32.00 334.92
3815.3 $ 0.31 $ 1,182.74 $ 847.82 $ 3.53 $ 0.09
226.04 156.67 32.00 414.71
5065.2 $ 0.31 $ 1,570.21 $ 1,155.50 $ 3.79 $ 0.08
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compared to MS may explain the differences (albeit not significant) in milk yield. Milk yield and composition Milk yields were similar to those reported by AnayaOrtega et al. (2008), Guadarrama-Estrada et al. (2007), and Heredia-Nava et al. (2007) from work in the area. Yields were also similar to those reported by Hargreaves et al. (2001) from studies on the use of supplementary silage for grazing dairy cows in Chile, using a similar stocking rate, but lower concentrate supplementation, concluding that silage supplementation enables cows to sustain yields under restrictive pasture conditions. Fike et al. (2002) report similar milk yields when supplementing maize silage to grazing dairy cows in Florida, USA. There are few recent reports on feeding oats silage to grazing dairy cows, and even reports on feeding dairy cows on oat forage are scarce. Earlier work by Schroeder et al. (1979) reported the use of oat forage envisaging that increasing oil prices would make it more appropriate for American dairy systems due to lower cost than maize silage. Helsel and Thomas (1987) compared cultivars of four small grain cereals for forage concluding that oats have lower DM yield than rye or wheat and comparable to barley, but that the oat forage produced was of better feeding quality due to higher CP and lower fibre content. Milk fat content was low in both treatments, a condition that has been observed in other work in the area (Heredia-Nava et al. 2007; Anaya-Ortega et al. 2008). The low milk fat contents might be attributed to the strong influence of the American Holstein breed in the upgraded cattle of small-scale farmers in central Mexico who have also paid no particular attention to the milk fat and protein content or yields in the breeding value of the selected sires for artificial insemination since there are no price premiums or penalties in these systems for milk quality (Lara-Covarrubias et al. 2003). In body condition score there was a slight albeit non significant improvement in both treatments given that cows began the experiment with a very low condition score. Améndola (2002) states that the use of forage supplementation at pasture may be a means to sustain body condition in grazing dairy cows. At the end of the trial cows had gained 23 kg more than at the beginning, which may reflect improved nutrition of the cows.
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Economic analysis The main objective of farmers involved in dairy production is to improve their income and life conditions. In small-scale systems in Mexico, feeding costs represent the highest component of total costs (Lara-Covarrubias et al. 2003). Therefore, the work herein reported is aimed at developing feeding strategies so that these systems rely mostly on good quality home grown forage with moderate amounts of concentrates; since the profitability of small-scale systems is strongly related to off farm expenditures of which concentrates comprise up to 40% of the total cost of production (Espinoza-Ortega et al. 2007). This issue will be even more important given the rise in grain prices worldwide, a situation that as the World Bank report indicates is not a temporary phenomenon, but likely to persist at least in the mid term (Revenga 2008). Although feeding costs were 24% higher in the OVS treatment, the recorded higher milk yields (although statistically non significant) resulted in a lower feeding cost per litre since the feeding cost per litre of the MS treatment was higher than OVS. The higher feeding cost for the MS system was due to the low yield of the maize crop given the fact that the late seeding meant that cultivations were due at the height of the rainy season, so machinery could not enter the maize field adequately due to water logging; coupled with a rainy year that hampered the good development of the maize crop. Nonetheless, margins over costs are competitive, and would enable farmers a higher income than what they could obtain as non qualified labour in the city. The inclusion of the OVS treatment was a sound proposal in order to obtain higher forage availability and a more intensive use of the land. The oat-vetch crop occupied the land for 88 days, at a time when there are usually no crops in the fields, making a more efficient use of the limited land resource and of the access to irrigation. Also, the cereal – legume intercrop provides other benefits as increasing the nitrogen content of the soil as well as the organic matter once the remaining herbage is ploughed in after the silage harvest, improving soil structure (Ross et al. 2004), and water retention. Results show the advantage of including oats as a catch crop after the maize providing good quality silage which can substitute or complement maize
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silage, particularly when the maize crop is suboptimal as in this work (low yield and high fibre content). However, oats should be sown soon after the maize is harvested. In the current work, oats were sown on 14 February and harvested in mid-May, to late for planting maize. Therefore, oats should be sown in late October or early November before severe frost kills the emerging plants, and harvested in mid-March at the latest to enable the timely sowing of the maize. Acknowledgements The authors express gratitude to the village of Ejido San Cristóbal, particularly Mr. Hermenegildo Reyes – Valdés who ran the demonstration module where the experiment took place, to Ms. Laura Edith Martínez-Contreras and Ms. María de Lourdes Maya-Salazar from Centro de Investigación en Ciencias Agropecuarias (CICA) for the chemical analyses. This work was undertaken with funds from the Universidad Autónoma del Estado de México (project UAEM 1822/2004); our gratitude also to the Mexican National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología - CONACYT) for the grant received by Yesenia Garduño-Castro.
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