Sorghum dry matter yield (DMY) and forage quality were evaluated at two row spacings (75 and 20 cm) and two sowing densities (33 and 65 seeds m-2), with harvest at a 300 g kg-1 whole plant dry matter concentration. Trials covered three consecutive growing seasons (2007, 2008 and 2009) with progressively lower annual rainfall. The year x row spacing interaction had no effect on traits, except for plant height. Year did affect the traits, except for whole plant dry matter concentration (322 g kg-1) and protein content (97.6 g kg-1). Annual DMY ranged from 10 t (2007) to 17 t ha-1 (2009), and 10 t (75 cm row spacing) to 16.6 t ha-1 (20 cm). In 2007, panicle dry weight was 109.4 g kg-1 higher than in 2008 and 158.1 g kg-1 higher compared to 2009. Thousand-grain weight was 13.66 g kg-1 higher in 2007 than the average of the two following years. Compared to 2009, digestibility was 89.5 g kg-1 lower in 2007 and 39.9 g kg-1 lower in 2008. There was correlation between digestibility and ash content (-0.94**), acid detergent fiber (-0.93**) and acid detergent lignin (-0.85*). Protein concentration was 15.2 g kg-1 higher at the 20 cm spacing than at the 75 cm. No year x sowing density interaction was present, and sowing density did not affect DMY or forage quality. Sorghum DMY and forage quality were improved using a 33 seeds m² sowing density and 20 cm row spacing.

El objetivo fue determinar los cambios en rendimiento de materia seca (RMS) y calidad del forraje de sorgo sembrado en surcos distanciados a 75 y 20 cm, y en densidades de 33 y 65 semillas m², cuando la planta tiene una concentración de materia seca de 300 g kg-1. No hubo interacción año x distancia entre surcos en los caracteres, excepto en altura de planta. Efecto de año existió, excepto en concentración de materia seca de la planta (322 g kg-1) y en proteína (97.6 g kg-1). El RMS por año varió de 10 t (2007) a 17 t ha-1 (2009), y de 10 a 16.6 t ha-1 en distancias de 75 y 20 cm, respectivamente. El peso seco de panículas fue 109.4 g y 158.1 g kg-1 mayor en 2007 que en 2008 y 2009, respectivamente, y el peso de mil granos fue 13.66 g kg-1 mayor en 2007 que al promedio de los dos años restantes. La digestibilidad fue 89.5 y 39.9 g kg-1 menor en 2007 y 2008, respectivamente, que en 2009. Hubo correlación entre digestibilidad y cenizas (-0.94**), fibra detergente ácido (-0.93**) y lignina detergente ácido (-0.85*). La proteína fue 15.2 g kg-1 mayor en surcos a 25 cm que a 75 cm. No hubo interacción año x densidad de siembra, ni la densidad afectó el RMS ni la calidad del forraje. El RMS y la calidad del forraje de sorgo fueron mejorados al combinar densidad de siembra de 33 semillas m² con distancia de 20 cm entre surcos.

The aim was to compare yield of dry matter (RMS) and quality of grain and foliage sorghum varieties with and without brown midrib (bmr), by using plants with average concentrations of 300 g kg-1 of DM. Three grain (Solarius, Aralba and Topsilo) and three forage (Sweet Virginia, Big Kauna and Sucrosorgho) varieties were studied. Sweet Virginia and Big Kahuna contain bmr gene. RMS varied from 11.10 t, of Topsilo, to 17.12 t ha-1 of Sweet Virginia, related with plant height and stem/plant proportion. Topsilo had greater number of sprouts (1.5 m-¹). Relationship panicle/plant was similar between varieties. Number of plants m-¹ had variation between varieties but did not affect RMS. Protein concentration was from 75.45 g kg-1 DM in Big Kahuna, up to 104.3 g kg-¹ DM in Solarius, and had inverse relationship with RMS, with plant height and with stem/plant ratio. Varieties with greater protein concentration (Solarius, Aralba and Topsilo), showed least RMS, lower height and lower ratio stem/plant. Foliar area per plant was source of protein variation between grain varieties. Digestibility ranged from 5 96 g kg-1 DM in Aralba, up to 720.4 g kg-¹ DM in Sweet Virginia, and was related with lignin concentration. This last variety with Big Kahuna and Solaris were the best in digestibility. The high digestibility from Solarius (not bmr carrier) was because its low stem/ plant ratio (0.35). Sweet Virginia variety is an important option in animal food since its high RMS and digestibility. Solarius had low RMS, but is useful for high consumption of digestible dry matter (dairy cows), also has better protein concentration.

El objetivo fue comparar el rendimiento de materia seca (RMS) y la calidad de variedades de sorgo de grano y forrajero con o sin nervadura café (bmr), al emplear plantas con concentraciones promedio de 300 g kg-¹ de MS. Se estudiaron tres variedades de grano (Solarius, Aralba y Topsilo) y tres forrajeras (Sweet Virginia, Big Kauna y Sucrosorgho). Sweet Virginia and Big Kahuna contienen el gen bmr. El RMS varió de 11.10 t, de Topsilo, a 17.12 t ha-1 de Sweet Virginia, relacionada con la altura de planta y con la proporción tallo/planta. Topsilo tuvo mayor número de rebrotes (1.5 m-¹). La relación panícula/planta no fue diferente entre variedades. El número de plantas m-¹ varió entre variedades pero no afectó el RMS. La concentración de proteína varió de 75.45 g kg-¹ MS en Big Kahuna, a 104.3 g kg-¹ MS en Solarius, y tuvo relación inversa con el RMS, con la altura de la planta y con la relación tallo/planta. Las variedades con mayor concentración de proteína (Solarius, Aralba y Topsilo), fueron las de menor RMS, menor altura y menor relación tallo/planta. El área foliar por planta fue la fuente de variación de la proteína entre las variedades de grano. La digestibilidad varió de 596 g kg-¹ MS en Aralba, a 720.4 g kg-¹ MS en Sweet Virginia, y estuvo relacionada con la concentración de lignina. Esta última variedad junto con Big Kahuna y Solarius fueron las de mayor digestibilidad. La alta digestibilidad de Solarius (no portador de bmr) se debió a su baja proporción (0.35) tallo/planta. La variedad Sweet Virginia es una importante opción en la alimentación animal dado a su elevado RMS y digestibilidad. Solarius tuvo bajo RMS, pero es útil cuando se requieren altos consumos de materia seca digestible por animal (vacas lecheras), además de contar con la mayor concentración de proteína.

Objetivou-se avaliar os efeitos das silagens de sorgo granífero, sorgo sacarino e milho sobre a ingestão, produção e composição química do leite e a digestibilidade dos nutrientes em vacas em lactação. Foram utilizadas 24 vacas da raça Prim'Holstein (PO), divididas em três lotes de oito vacas para avaliação das seguintes silagens: silagem de milho (SM); silagem de sorgo granífero (SG); e silagem de sorgo sacarino (SS). As silagens foram fornecidas à vontade com dois concentrados comerciais, distribuídos de acordo com o nível de produção leiteira. A silagem de sorgo granífero promoveu maior ingestão de MS (22,98 kg/dia) em comparação às silagens de milho (21,95 kg/dia) e de sorgo sacarino (19,43 kg/dia). A ingestão de água (litros/vaca/dia) foi semelhante entre os animais alimentados com silagem de milho (71,91) e de sorgo granífero (76,30) e menor nos animais alimentados com silagem de sorgo sacarino (56,95). A produção de leite total (28,81; 24,69 e 24,14 kg/dia) corrigida a 4% de gordura (30,65; 25,63 e 26,10 kg/dia) foi maior entre as vacas alimentadas com silagem de milho, no entanto, a porcentagem de gordura do leite das vacas alimentadas com silagem de sorgo sacarino foi maior (4,56%) em comparação àquelas alimentadas com silagem de milho (4,39%) e silagem de sorgo granífero (4,31%). A porcentagem de proteína foi maior (3,25%) no leite das vacas alimentadas com silagem de milho, intermediária no leite das vacas alimentadas com silagem de sorgo sacarino (3,05%) e menor no leite das vacas alimentadas com silagem de sorgo granífero (2,97%). Os coeficientes de digestibilidade dos nutrientes foram maiores nas vacas alimentadas com a ração à base de silagem de sorgo sacarino em comparação às rações à base de silagem de sorgo granífero e de milho.

The effect of feeding grain sorghum silage, sweet sorghum silage, and corn silage on intake, milk production, milk composition, and nutrient digestibility of lactation dairy cows was evaluated. Twenty-four Prim'Holstein (PO) cows were used, forming three groups of eight cows each. The experimental treatments were: 1) corn silage; 2) grain sorghum silage; and 3) sweet sorghum silage, fed ad libitum, with two commercial concentrates, distributed following the cow milk production. Grain sorghum silage promoted greater DM intake (22.98 kg/day) compared to corn silage (21.95 kg/day), and sweet sorghum silage (19.43 kg/day). Dry matter intake was greater for corn silage than for sweet sorghum silage. Water intake (L/cow/day) was similar for the animals fed corn silage (71.91) and grain sorghum silage (76.30), and both were greater than the water intake of animals fed sweet sorghum silage (56.95). Total milk production (28.81; 24.69 and 24.14 kg/day), 4% fat corrected milk (30.65; 25.63 and 26.10 kg/day), and milk chemical composition was greater for cows fed corn silage when compared to the ones receiving grain sorghum silage and sweet sorghum silage. Cows fed sweet sorghum silage, but showed higher milk fat percentage (4.56%) compared to cows fed corn silage (4.39%) or grain sorghum silage (4.31%). Milk protein concentration was higher for cows fed corn silage (3.25%), intermediate for cows fed sweet sorghum silage (3.05%), and lower for the ones fed grain sorghum silage (2.97%). Nutrient digestibility coefficients were greater for cows fed sweet sorghum silage compared to other silages.