Herbage yield and quality of 12 Urochloa cultivars and lines in Northeast Thailand

Forage accumulation yields and nutritive value of 12 Urochloa cultivars and pre-commercial lines (Mulato II, Cayman, Cobra, Marandu, Toledo, BRS Piatã, BRS Paiaguás, Ruzi, Humidicola, BRO4/3025, BRO4/3207 and BRO4/2515) were evaluated in a field trial in Northeast Thailand during 2015–2018. Total herbage yields for cultivars and lines over 3 years ranged from 15,800 kg DM/ha (Ruzi) to 33,800 kg DM/ha (Toledo). Toledo produced the highest total biomass across the 3 wet and dry seasons. BRS Piatã and BRS Paiaguás showed good performance, out-yielding Ruzi and Mulato II in total DM in both wet and dry seasons. The 6 hybrid Urochloa cultivars/lines (Mulato II, Cayman, Cobra, BRO4/3025, BRO4/3207 and BRO4/2515) all accumulated similar total DM yields over 3 years, outyielding Ruzi (P<0.05). Crude protein concentrations in forage were higher (P<0.05) in the dry season than wet season and in leaf than stem. In the second and third dry seasons, Ruzi had higher CP concentrations in both leaf and stem than all other cultivars and lines. ADF and NDF concentrations were lower in the dry season than the wet season. This trial has shown that BRS Piatá and BRS Paiaguãs would be ideal replacements for Mulato II and Ruzi in Northeast Thailand because of their superior dry season production for smallholder farmers for either cut-and-carry forage or grazing.

Toledo produced higher wet and dry season DM yields than Mulato II in one series of trials (Hare et al. 2009), but in another series of trials, DM yields of Toledo were similar to or lower than those of Mulato II (Hare et al. 2009;2015a).DM yields of Marandu were similar to those of Mulato II in the wet season, but lower than those of Mulato II in the dry season (Hare et al. 2009).In all trials, Mulato II consistently produced the highest percentage of leaf compared with other Urochloa cultivars and lines.
BRS Piatã and BRS Paiaguás were reported to have high DM production during the dry season in Brazil (Euclides et al. 2001(Euclides et al. , 2009;;Valle et al. 2013).These cultivars are potential alternatives to existing Urochloa grasses for sowing in Thailand.In addition, 3 new Urochloa hybrid pre-commercial lines from Brazil (BRO4/3025, BRO4/3207 and BRO4/2515) selected for good drought tolerance and Humidicola were made available from Tropical Seeds LLC.
The objective of this research was to examine the seasonal production and quality in a field trial over 3 years of 2 U. brizantha grasses (BRS Piatã and BRS Paiaguás),

Introduction
Urochloa (formerly Bracharia) species are the second most common pasture grasses grown in Thailand after Megathyrsus maximus cultivars (Hare 2020).U. ruziziensis is grown widely in Thailand because of the availability of large quantities of relatively cheap seed (US$4-6/kg), although its dry season production is very low (1,000-2,000 kg dry matter (DM)/ha) (Hare et al. 2005;2009).Several new cultivars and pre-commercial lines of Urochloa have been produced, which could be suitable for sowing in Thailand (Table 1).Among them, Urochloa hybrid Mulato II is now increasing rapidly in popularity, because of its superior dry season production (3,000-4,000 kg DM/ha), high leaf production (77-90 % leaf) and high nutritive value (Hare et al. 2009;2015a), despite its relatively high seed price (US$12-14/kg).
Several field trials in Thailand over time have examined production and quality of a range of Urochloa hybrids and species compared with Mulato II (Hare et al. 2005;2009;2013;2015a) and found inconsistent differences in production between Mulato II and the other Urochloa grasses.For example, Cayman produced more total DM than Mulato II in only one wet season and one dry season, with significantly lower leaf production (Hare et al. 2013;2015a).Cobra had similar DM production to Mulato II, but with lower leaf production (Hare et al. 2015a).

Materials and Methods
A field experiment was conducted at Ubon Ratchathani University, Thailand, (15°14'38" N, 104°50'55" E; 130 masl) from 2015 to 2018.The site was an upland sandy low humic gley (Paleaquult) soil (Roi-et series) (Mitsuchi et al. 1986).Soil samples, taken at seed sowing in July 2015, showed that the soil was acidic (pH 4.4; water method) and low in organic matter (0.7 %), N (0.03 %), P (8.9 ppm; Bray II extraction method) and K (7.1 ppm; Flame Photometer method).During the 5 years prior to the commencement of the experiment, the site was used for a series of Megathyrsus grass trials.The site was prepared and 12 Urochloa grass cultivars and pre-commercial lines (Table 1) were sown in 3 × 5 m plots in a randomized complete block design with 4 replications.Details of field crop management are presented in Table 2. Seed germination laboratory tests (alternating temperatures of 12 h light at 35 ⁰C and 12 h dark at 25 ⁰C) prior to sowing indicated percentage germination of Mulato II 50 %, Cayman 50 %, Cobra 50 %, Marandu 30 %, Toledo 30 %, BRS Piatã 10 %, BRS Paiaguás 28 %, Ruzi 30 %, Humidicola 50 %, BRO4/3025 50 %, BRO4/3207 50 % and BRO4/2515 50 %.Sowing rates were adjusted to 10 kg pure-live-seed/ha.At each sampling cut (Table 2), when the grasses were at about 40-60 cm above ground level, herbage in six 0.25 m 2 quadrats per plot was cut at 5 cm from ground level and weighed fresh.A 300 g subsample, taken from the bulked sample, was divided into leaf and stem and subsamples dried separately at 70 °C for 48 h to determine dry weight.Dry weight data were accumulated each season to give total dry matter, stem and leaf yields for each season.
The dried subsamples were bulked for each season and analyzed for total N using the Kjeldahl method (Kjeldahl 1883) and crude protein (CP) estimated (CP, % N × 6.25).Acid detergent fiber (ADF) and neutral detergent fiber (NDF) concentrations were measured from seasonal bulked subsamples using the Van Soest method (Van Soest 1963).At each sampling cut, observations were recorded for emergence of inflorescences.After each sampling cut, remaining herbage in the plots was cut to 5 cm from ground level and removed.
Data from the experiments were subjected to analysis of variance, using the IRRISTAT program from the International Rice Research Institute (IRRI).Means of variables were compared using Fisher's protected LSD (P≤0.05).

Rainfall
Rainfall during the wet season (May-Oct) in 2016 and 2017 was 18 and 10 %, respectively, above the 20-yr mean (Figure 1).In the dry season (Nov-Apr) rainfall was close to average in the 2015/2016 season, 13 % below average in the 2016/2017 season and 26 % above average in the 2017/2018 season.

Forage accumulation and feed quality
For all cultivars and lines, as expected DM production during the wet seasons (Table 3) far exceeded that in the dry seasons.Over 3 wet seasons, Toledo accumulated 31, 41, 44, 83 and 111 % more total DM than BRS Humidicola during the wet season (P<0.05;Table 3), while in the first dry season, BRS Piatã (600 kg DM/ ha) produced higher DM yields (P<0.05)than Mulato II, Cayman, Cobra, Marandu and Toledo.Overall yields more than doubled in the second wet season (mean yield 4,478 kg DM/ha in 2015 vs. 9,952 kg DM/ha in 2016) and BRS Piatã (13,000 kg DM/ha) out-yielded all other cultivars and lines (P<0.05),except for Toledo, while Ruzi (6,300 kg DM/ha) had significantly (P<0.05)lower yields than the other cultivars, except for Cobra and Humidicola.
Paiaguás, Mulato II, Cobra, Humidicola and Ruzi, respectively (P<0.05;Growth differences between cultivars and lines occurred in the second dry season, when growth far exceeded that in the first dry season, with BRS Paiaguás, Humidicola, Toledo and BRO4/2515 having higher yields (P<0.05)than Mulato II, Cobra and Ruzi.High DM yields persisted in the third wet season (mean 8,734 kg DM/ha), with Toledo (12,300 kg DM/ha) out-yielding all other cultivars and lines, while BRS Piatã and BRS Paiaguás out-yielded Mulato II, Cobra, Ruzi and Humidicola.During the third dry season, DM yields for BRS Piatã (1,500 kg DM/ha) exceeded those for Mulato II, Cayman, Cobra, Marandu, Ruzi and Humidicola (P<0.05).
Overall DM yields for the various cultivars and lines over the 3 years ranged from 15,840 kg/ha for Ruzi to 33,789 kg/ha for Toledo.Accumulated DM yields for Ruzi were significantly lower than for all other cultivars and lines except for Humidicola in the wet season (Table 3).
In the first wet season, Cayman and Marandu produced more leaf DM (3,700 kg leaf DM/ha) than Mulato II, BRS Piatã, BRS Paiaguás, Ruzi, Humidicola and BRO4/3207 (P<0.05;Table 4).In the second wet season, both Toledo (8,400 kg leaf DM/ha) and BRS Piatã (7,900 kg leaf DM/ha) accumulated more leaf DM/ha than all other cultivars (P<0.05).Mulato II and Marandu produced more leaf DM (6,700 kg leaf DM/ha) in the second wet season than Ruzi, Humidicola, BRS Paiaguás, BRO4/3025, BRO4/3207 and BRO4/2515.Similarly in the third wet season, Toledo produced more leaf dry matter (8,500 kg leaf DM/ha) than all other cultivars and lines (P<0.05) and in the same season, Mulato II produced more leaf DM (6,000 kg leaf DM/ha) than Cobra, Ruzi, Humidicola, BRO4/3025, BRO4/3207 and BRO4/2515.Differences between cultivars and lines in leaf production during the dry seasons when yields were low tended to be relatively small, with Toledo consistently the highest and Ruzi the lowest.
Mulato II produced a higher proportion (P<0.05) of leaves than all other cultivars and lines in all seasons (wet season average 72 %; dry season average 90 %), except in the first wet season, when Toledo and BRS Paiaguás had similar leaf proportions to Mulato II (P>0.05;Table 6).Leaf proportions of all cultivars and lines were higher in the dry season than in the wet season.BRO4/3025, BRO4/3207 and BRO4/2515 produced a dense population of inflorescences in September in the first year and in July and September in the second and third years, but inflorescence emergence of other species and lines was negligible.Indices used to compare feed value of the grasses varied between sampling period (wet vs dry seasons) and cultivar/line.Crude protein concentrations in forage were higher in the dry season than in the wet season and in leaf than in stem (Table 7).Humidicola had higher CP concentrations in both stem and leaf in the first wet season than all other cultivars and lines (P<0.05).In the second and third dry seasons, Ruzi, the other low-yielding grass, had higher CP concentrations in both leaf and stem than all other cultivars and lines.In the second wet season, BRS Piatã had higher CP concentrations in leaf than other cultivars and lines, except for BRS Paiaguás, Ruzi and Humidicola, which had similar CP concentrations.In the third wet season, CP concentrations in leaf of Cobra were similar to those in leaf of Mulato II, Cayman and Ruzi, but higher than for all other cultivars and lines.ADF (26-50 %) and NDF (45-78 %) concentrations varied between cultivars and lines, seasons and plant parts (Tables 8 and 9).Dry season concentrations were lower than those in the wet season and leaf concentrations were lower than in stems.In most wet seasons, Mulato II, Cayman, Cobra and Ruzi had lower leaf ADF and NDF concentrations than many of the other cultivars and lines (P<0.05;Tables 8 and 9).

Urochloa in NE Thailand
The hybrid Urochloa cultivars (Mulato II, Cayman and Cobra) and lines (BRO4/3025, BRO4/3207 and BRO4/2515) all accumulated similar total DM yields throughout the study, which were significantly higher than those of Ruzi.Mulato II was slower to establish in the first wet season than the other hybrid cultivars and lines.However, Mulato II had a significantly higher proportion of leaf than the other hybrid cultivars and lines in all seasons.Previous studies have shown that Cayman and Cobra did not show any production and nutritive advantages over Mulato II (Hare et al. 2013(Hare et al. , 2015a;;Vendramini et al. 2014).Cayman was released for its waterlogging tolerance and Cobra for its strong upright nature for cut-and-carry forage (Hare et al. 2015a).Owing to lack of production advantages over Mulato II and their lower seed yields in village seed production programs, these cultivars are not currently promoted in Thailand.BRO4/3025 has now been released by Grupo Papalotla as cultivar 'Camello' (bit.ly/3Bq5wnF) for its good drought tolerance and decumbent nature making it suitable for grazing.Camello displayed no production advantages over Mulato II and in Mexico, DM production of Camello was lower than that from Toledo, Cobra and Cayman in the dry season (Robles-Vega et al. 2020).Camello has an extended flowering period in the middle of the wet season, July to September, and in trials in Thailand seed yields were negligible (Hare unpublished data).
Marandu established very quickly and, over 3 years, accumulated DM yields that were similar to those of the other cultivars and lines in the dry season, except for Ruzi.Other studies in Thailand have shown that DM yields of Marandu were consistently intermediate between those of Mulato II and Ruzi (Hare et al. 2009).Humidicola grew poorly in the wet season when over 80 % of the herbage is produced.A previous study in Thailand showed that Humidicola compared with several other grass species had intermediate wet season DM production and above average dry season DM production (Hare et al. 1999).Humidicola has a reputation for being invasive, which is not desirable for many pasture species.In the current study after 3 years, Humidicola was spreading out and invading surrounding plots from stolons.Seed production in Thailand is difficult, due to its extended flowering period in the wet season (Hare unpublished data), so it was not evaluated further.
This trial has shown that BRS Piatã and BRS Paiaguás would be ideal replacements for Mulato II and Ruzi in Northeast Thailand for their superior dry season production and they would appeal to smallholder farmers for either cut-and-carry forage or grazing.If seeds of Toledo could be produced in Thailand, this cultivar should be considered for grazing because of its superior DM production over Mulato II and Ruzi.

Table 1 .
Background of cultivars/pre-commercial lines of Urochloa species and hybrids.

Table 2 .
Field crop management during the evaluation of Urochloa cultivars and lines.

Table 3
Rainfall at the Ubon Ratchathani University meteorological station, 200 m from the research site, during the experiment compared with the medium-term mean.

Table 3 .
Total dry matter accumulation (kg/ha) of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons during 2015 to 2018 at Ubon Ratchathani, Thailand.

Table 4 .
Total leaf accumulation (kg DM/ha) of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons from 2015 to 2018 in Ubon Ratchathani, Thailand.
1Not measured; 2 Means within columns followed by the same letter are not significantly different (P>0.05).

Table 5 .
Total stem accumulation (kg DM/ha) of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons from 2015 to 2018 in Ubon Ratchathani, Thailand.
1Not measured; 2 Means within columns followed by the same letter are not significantly different (P>0.05).

Table 6 .
Leaf proportion (% DM) of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons from 2015 to 2018 in Ubon Ratchathani, Thailand.
1Not measured; 2 Means within columns followed by the same letter are not significantly different (P>0.05).

Table 7 .
Crude protein concentrations (%) in stem and leaf of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons from 2015 to 2018 in Ubon Ratchathani, Thailand.Means within columns followed by the same letter are not significantly different (P>0.05).

Table 8 .
Acid detergent fiber concentrations (%) in stems and leaves of Urochloa cultivars and lines in wet (May-Oct) and dry (Nov-Apr) seasons from 2015 to 2018 in Ubon Ratchathani, Thailand.
1Not measured; 2 Means within columns followed by the same letter are not significantly different (P>0.05).