Introduction

The Laguna Region is the main dairy basin of Mexico and at critical times such as winter period requires nutritional quality forage options enabling it to maintain production. In the north of the country recurrently drastic climate variations in winter, as the frozen registered on 3 and 4 February 2011 that wreaked havoc on domestic agriculture are presented. Cereals represent important alternatives to sustain livestock production have frost tolerance during vegetative development and its use has spread in recent years, using them grazing, green onions, henificado, chopped and silage. (^{Hughes et al., 1974}; ^{Flores et al., 1984}; ^{Colín et al., 2004}).

During the spring and summer high evaporation occur in semi-arid areas as it is where the Laguna Region is located and an option to avoid is making planting in winter, which favors the use of cereals and legumes to meet the demand of adequate quality forage . It has been proposed that a wheat, triticale or barley fodder should be soft or preferably beardless beard cover pin (^{Flores, 1977}), which will extend the period of harvest to milky-doughy or later stages grain, but represent a risk animal.

Cereals have characteristics that make them especially useful for fodder, producing high yields and are rich in protein, vitamins and carbohydrates, (^{Cherney and Marten, 1982}; ^{Cash et al., 2004}), has been classified as a good quality forage resource calidad (^{Hart et al., 1971}; ^{Juskiw et al., 2000}). ^{Herrera (1999)}, referring to the quality forage sources mentioned that low quality forages are those whose percentage of neutral detergent fiber (FDN) is greater than 60%, acid detergent fiber (FDA) greater than 35%, net energy lactation (ENL) of less than 1.4 Mcal/kg. The protein content is an important dietary factor per se; so foods high in protein, are also considered high quality (^{Juskiw et al., 2000}). In evaluating forage quality, ^{Castro (1976)} reports that in barley, oats, wheat and triticale, no difference in protein content between species, finding an average of 35 percent in the early stages of development and 7% in half seed head.

The maturity stage at harvest has the greatest effect on the biomass yield and quality of cereals (^{Cherney y Marten, 1982}; ^{Bergen et al., 1991}). It increases performance and quality declines as the crop matures, although cereal quality can be maintained or improved when grain growth occurs (^{Khorasani et al., 1997}; ^{González, 2007}).

In forages it is vital to consider the nutritional value, reporting a decrease in general the same as the plant matures (^{Juskiw et al., 2000}). Thus, the increase of FDA and FDN has been reported in response to the advance grain maturity (^{Cherney et al., 1983}). The leaves and spikes generally have higher digestibility and protein stems (^{Baron and Kibite, 1987}) and therefore may contain higher forage quality, however, there are few studies on the nutritional value of these fractions is studied although in some of them and barley has been established that an increase of the energy value associated with a higher proportion of grain in stages grain maturity, which also favors the protein content and increases the quality indicators, due to dilution indigestible fiber from grain (^{Ben-Ghedalia et al., 1995}; ^{Juskiw et al., 2000}).

Under these assumptions, the Program Grain UAAAN has developed new beardless wheat genotypes in order to provide good forage production options and quality, however the nutritional contribution of the fractions that make up the forage is unknown. To this end, the present study aimed to evaluate the dry matter production and nutritional value of its fractions (leaves, stems and spikes) in beardless wheat lines compared to witness different species (oats and barley) under the hypothesis that there are wheat genotypes that equal or exceed those witnesses in total dry forage production and nutritive value of its fractions within genotypes evaluated.

Materials and methods

Twenty-seven advanced lines of feed wheat beardless developed by the Grains Program UAAAN and commercial varieties: Oats cv. Cuauhtemoc and Triticale cv. Eronga-83 plus an experimental line beardless barley (Narro 95) were evaluated during the season autumn-winter 2010-2011 at the ranch "Las Vegas" town of Francisco I. Madero, Coahuila, using alph- lattice design with three replications.

Land preparation consisted of traditional work used for the establishment of small grains of winter in regions where it is grown under irrigation, being planted dry manually at a seed rate of 120 kg ha^-1, using 60 units of nitrogen using urea as a source, plus 80 units of phosphorus using monoammonium phosphate (MAP) to meet the nutrient; the first auxiliary irrigation 60 units of nitrogen to the same source was applied. Weeds were controlled manually, and no insecticide or fungicide was applied. A 118 days after planting watering sampling of forage and the rest of the experimental plot was conducted was allowed to come to grain production. The approximate total film during the crop cycle was 40 cm.

The experimental plot consisted of 6.3 m² (6 rows of 3 m length 0.35 m between rows), sampling 50 cm of one of the rows fully competitive, cutting at a height of 5 cm above the soil surface. plant height (height), forage yield (FV), phenological stage (stage) by the scale of Zadoks et al: when cutting the variables were recorded. (1974), and the percentage of land cover (COB); green fodder is dried in a covered sundeck until constant weight and then the production of dry matter or dry forage was determined in t ha^-1 (PSTON) separating the feed into its components: leaves, stems and spikes. Forage samples of the materials and rendidores oats and barley witnesses were sent to the laboratory AGROLAB of Mexico, S. A. de C. V., based in Gomez Palacio, Durango, for compositional analysis, determining values: percentage of crude protein (PC), acid detergent fiber (FDA), neutral detergent fiber (NDF) and net energy for lactation (NEL) for each of the fractions leaf (H), stem (T) and pin (E), literal spiked to identify their respective values.

Field data were analyzed using an alpha-lattice (0.1), comparing averages with proof of DMS. With average values of field variables and the results of nutritional value principal component analysis (ACP) in order to analyze the structure of covariance and detect the association of variables and genotypes it was carried out following the methodology described by Johnson and Wichern (1988).

Results and discussion

The analysis of variance showed differences (p< 0.01) between genotypes for plant height, phenological stage at cutting production of fodder and its fractions, while coverage only significant differences (p< 0.05) were detected, of witnesses used, triticale showed the highest plant height of 118 cm being statistically equal to three lines beardless wheat, oats reached 83 cm being the genotype lower height recorded in the experiment, possibly because of lower recovery after registered on 2 and 3 february 2011, the overall average frost stood at 102 cm. When cutting fodder, triticale was at the beginning of grain formation (aqueous or maturity stage 71 of the sacale fo ^{Zadoks et al., 1974}), while barley was in step 74 (milky medium) behaving as earlier materials, meanwhile oats were in the issue stage of the pin (step 59); the mean of this variable is registered in 66 or flowering stage. Most coverage was achieved barley field, followed by several wheat in the same group of significance, triticale showed middle ground cover (75%), and oats (65%) who presented lower ground cover, probably because his poor recovery after frost.

In the production of dry matter (PSTON) 15 callow wheat lines were located along with barley in the first group of significance in the following order: AN- 326-09, AN-26899, AN-220-09, barley, AN-228-09- AN-264-09, AN-26399, AN-244-99, AN-258-99, AN-216-09, AN- 217-09, AN230-09, AN-251-99, AN.272-99, AN226-09 and AN-229-09 who produced more than 12.0 t ha^-1 of dry matter. These genotypes, more oats and lines AN-209-09, AN-336-09 and AN-267-99 were considered for conducting analyzes nutritional value of fractions: leaf, stem and spigot. The mean of this variable was located in 13.32 t ha^-1.

With respect to fractions of forage stems (PSTALLO) provided a 50.98% of the total dry matter, while the leaves (PSHOJA) and pins (PSESPIGA) contributed 36.11 and 12.91% respectively. Among the 16 materials that made up the first group of significance in the production of total dry forage increased production of PSTALLO the genotypes obtained: AN-326-09, AN-228-09, AN-268-99, AN-26399 and 220-09 and others, who produced statistically like barley and they outperformed oats. The 28 genotypes of the first group of significance to PSHOJA included barley, oats and genotypes as AN-220-09, AN-217-09, AN-33609, AN-216-09, AN-264-09 and AN-209-09; all visually selected for highest leaf. Regarding PSESPIGA only six genotypes (including triticale Eronga 83) joined the first group of significance highlighting genotypes AN-268-99, AN-326-09 and AN-228-09.

The results of the analysis showed that there bromatological beardless wheat lines with higher crude protein content of oats in fractions studied, as well as oats showed the stem 8.3% protein (PCT) was wheat with 10% of PCT; Oat showed a 11.1% protein in wheat leaves exhibiting exist to 17.2% protein in leaf (PCH). Similarly occurred with the protein content in the pin (PCE) where oats while 19% showed some wheats reached to 25.6%. Barley consistently showed higher amounts of PC oats in all fractions tested.

All species showed a similar trend in PC contents: fewest in the stalks, leaves and intermediate to higher spikes.

Acid detergent fiber stem (FDAT) and leaf (FDAH) something similar occurred in the studied species, with wheat beating oats in content, but in FDA Tang (fdae) several wheats showed lower content the oats. A trend prevailed in the cereals: more FAD in stems, leaves and lower intermediate in FAD in spikes.

Similar behavior presented neutral detergent fiber (FDN) for the listed fractions with beating wheat oats in stems (FDNT) and leaves (FDNH), while the pin (FDNE) only some wheats showed fewer this fiber (range 54.7 to 64.9%).

These quality components could be affected by phenological stage as shown by some materials have shown (^{Cherney y Marten, 1982}; ^{Bergen et al., 1991}).

The contents of net energy for lactation were higher for both oat stalks (ENLT) and leaves (ENLH), but in the ENL Tang (ENLT) several beardless wheats the beat, no doubt because most phenological stage which allowed them to have grain in the ear and achieve more energy.

To jointly analyze the above variables by principal components, three components with which 71.7% of the total variance (Table 1) were retained explained. The first component contained 29.7% of the variance and explained the positive relationship with each other and with the component of net energy of lactation stem (ENLT), leaf (ENLH) and pin (ENLE) with crude protein pin (PCE) and stems (PCT), neutral detergent fiber shank (FDNE) and dry matter production of the sheet (PSHOJA), while the phenological stage (ETAPA), plant height (ALTURA), production Total dry matter (PSTON), dry matter production of stems and spikes (PSTALLO and PSESPIGA) fibers (FDAH, FDNT, FDNH) and land cover (COB) showed a positive association with each other but negative with the component; whereby said first component can be interpreted in terms of the change that occurs to advance phenological stage, reflecting higher production of dry matter but fodder become more fibrous and woody, reducing protein and energy content, as shown in Figure 1; and this component separates the fibrous and woody those higher protein content and high energy genotypes, higher production. This has been well established and documented for most fodder obtained with small grains (^{Stark and Wilkinson, 1992}; ^{Mc Cartney and Vaage, 1994}; ^{Royo et al., 1998}; ^{Carr et al., 1998}), although overall, without explaining what happens in fractions that compose it.

Figure 1 Distribution of the variables in the first two principal components. 

The second component contained 25.9% of the variance explained mainly negative relationship between the content of neutral detergent fiber in leaves and stems (FDNH and FDNE) protein spikes (PCE) and acid detergent fiber sheet with net energy lactation stems and leaves (ENLT and ENLH) phenological stage of materials (ETAPA) and the protein content of the sheet (PCH), suggesting that some of the materials showed high levels of energy and protein in the feeding fractions brought to advanced stages of the formation of grain presenting smaller and less protein fibers in the ear. This is true for some wheats habit similar to that of barley growth, the highest dry matter production is associated with lower fiber content (Table 1 and Figure 1). The third component contained 13.6% of the variance, mainly explaining the higher amount of crude protein in stems, leaves and spikes associated with the coverage and production, albeit on a smaller stage oats.

By plotting the genotypes in the plane spanned by the two main components (Figure 2) we can characterize partially by production and nutritional value, and the beardless wheat lines AN-230-09, AN-326-09, AN-268-99, AN-228-09, AN229-09 and AN-63-99 are high, early materials, excellent producers of dry matter (with a high proportion of spikes and stems) and good crude protein content in the leaves, but smaller crude protein stems and spikes, as well as lower energy and neutral detergent fiber in the combined shank with fewer leaves.

Figure 2 Distribution of genotypes in the first two principal components. 

Conversely, lines such as the AN-216-09, AN-217-09, AN-258-99, AN-267-99 and AN-336-09 spikes have higher protein content, with more energy and detergent fiber neutral, increased leaf production and higher protein content in the stem, but produce fewer pegs and stems which confers lower yield of total dry matter, have lower height, are more delayed and less protein content in leaves.

Genotypes as AN-244-99, AN-272-99, AN-52-99 and AN209-09 are materials with higher ground cover, but are more fibrous and less energy content.

Oats and barley for its part, along with the AN-220-09, AN-264-09 and AN-226-09 lines have more net energy for lactation in stems and leaves, lower acid detergent fiber content in all fractions forage and lower NDF content in stems and leaves (Figure 2). This group of wheat lines is interesting since they have similar production and quality oats and barley, with the additional advantage of the absence of edges in the ear, which would avoid damage to the mucous membranes of cattle. Oats location at the far right, indicating their higher energy value stems and leaves, but lower production and stage characteristics that differ from the rest of the materials evaluated is highlighted.

Conclusions

There beardless wheat lines that have adequate production and quality of forage, similar to oats and barley can be used in livestock feed. This provides an option to diversify and flexible schemes intensive forage production as in dairy areas. In cereals evaluated the greatest contribution of dry matter had it stems, followed by leaves and finally the ears. The spikes showed greater nutritional value than the leaves and stems.