Influencia de la calidad del heno suplementario y la localización de la pastura sobre el rendimiento de bovinos de carne a pastoreo sobre avena

Heifers grazing oat pasture (OP) at two locations in Argentina, Argerich (ARG) and Pasman (PAS), were subjected to one of three different dietary supplement treatments: (1) control (CON, no supplement), (2) sorghum hay (SH), or (3) alfalfa-grass hay (AGH), all provided ad libitum in individual pens. The variables measured were: dry matter (DM) yield and composition of OP, hay intake, average daily weight gain (ADG), rumen pH and NH3-N, and blood mineral levels. DM availability did not limit OP intake. OP crude protein (CP) content ranged from 11.3 to 13% at ARG, and 10.7 to 13.3% at PAS. OP-minerals varied with location; the mean K/(Ca +Mg) ratios were 5.68 meq (ARG) and 4.82 meq (PAS). Heifers ate more AGH (785 g) than SH (684 g; P = 0.08). Hay consumption was 2.88 times greater at PAS than at ARG (P < 0.05). ADG was larger with SH (558 g) and AGH 594 g than with CON treatment (454 g); the average for ARG animals was 571 g compared to 500 g for PAS animals (PSe realizaron tres tratamientos con novillas pastoreando verdeos de avena (VA) en dos localidades de Argentina, Argerich (ARG) y Pasman (PAS): (1) Control (CON, sin suplemento), (2) heno de sorgo (HS), y (3) heno de alfalfa y gramíneas (HAG), suplementados ad libitum en corrales individuales. Evaluamos rendimiento de materia seca (MS) y composición en VA; y en los animales consumo del heno, ganancia diaria de peso (GDP), pH y N-NH3 en rumen, y minerales en sangre. La disponibilidad de MS no limitó el consumo de VA; su proteína bruta (PB) osciló entre 11,3 y 13% (ARG), 10,7 y 13.3% (PAS). Los minerales en VA variaron entre localidades, la relación K/(Ca + Mg) promedió 5,68 meq (ARG) y 4,82 meq (PAS). Las novillas consumieron diariamente más HAG (785 g) que HS (684 g; P = 0.08), y 2,88 veces más heno en PAS que en ARG (P < 0,05). En GDP, HS (558 g) y HAG (594 g) superaron al CON (454 g), y la media de ARG (571 g) a PAS (500 g; P < 0,05). En el rumen el pH decreció a las 14:30 h (6,7) vs. 10:00 h (7,5; P < 0,05), y el N-NH3 (mg dl-1) aumentó a las 14:30 h (19,59) vs. 10:00 h (4,69; P < 0,05). Ca (15.50 mg dl1) y Mg (2.84 mg dl1) en plasma fue mayor en PAS (P < 0,05). El rendimiento animal mejoró con la suplementación, pero la magnitud de respuesta estuvo afectada por la localidad

Efecto de la adición a la dieta de Zn y/o monensina sobre la respuesta productiva, fermentación ruminal y cinética digestiva en bovinos de carne

Two experiments (Exp1 and Exp2) were conducted to investigate the effect of dietary inclusion of Zn and(or) monensin on performance and rumen fermentation in beef cattle fed a barley grain, alfalfa hay and sunflower meal. In Exp1, 20 calves were assigned to one of the following treatments: CON = control; Z = 430 mg Zn/kg of DM; M = 35 mg monensin/kg of DM; and ZM = both Zn and monensin. Dry matter intake (DMI), DM digestibility (DMD), average daily gain (ADG), and feed to gain (F/G) ratio were determined. Blood analyses included hematocrit, glucose, urea, total protein, alkaline phosphatase and creatinine. In Exp2, the rumen fluid of four cannulated steers, in identical treatments, was studied for Zn concentration, pH, NH3-N, VFA. Rumen dilution rate, turnover time, and volume; in situ DM disappearance of barley and alfalfa were also determined. In Exp1, no treatment response was observed for DMI, ADG or DMD (P > 0.10). Differences in F/G were not significant, despite a numeric F/G decrease in M (6.6 kg/kg). No differences were detected in blood variables. In Exp2, an interaction of treatment x time (P = 0.0174) for Zn concentration was detected, where ZM, followed by Z, had highest mean values at all time intervals. Ruminal parameters, kinetics or DM degradability were not modified by treatments; pH reached the lowest value (6.1; P < 0.05) 12 h after supplement feeding. Overall, supplying more than 20 times the Zn requirement has not substantially affected performance or digestion.En dos experimentos (Exp1 y Exp2) se investigó el efecto de la inclusión en la dieta de Zn y/o monensina sobre la productividad y fermentación ruminal de bovinos alimentados con grano de cebada, alfalfa y harina de girasol. En Exp1, 20 terneros fueron asignados a tratamientos: CON = control; Z = 430 mg Zn/kg de MS; M = 35 mg monensina/kg de MS y ZM = Zn + monensina. Se determinó consumo de materia seca (DMI), digestibilidad (DMD), ganancia de peso (ADG) y eficiencia de conversión alimenticia (F/G). Análisis de sangre incluyeron: hematocrito, glucosa, urea, proteína total, fosfatasa alcalina y creatinina. En Exp2, el líquido ruminal de cuatro novillos fistulados sujetos a tratamientos idénticos fue analizado para: concentración de Zn, pH, NH3-N, VFA. Se determinó dilución de fase líquida, tiempo de recambio y volumen ruminal; y degradación in situ de cebada y alfalfa. En Exp1 no se observó respuesta a los tratamientos para DMI, ADG y DMD. Las diferencias no fueron significativas para F/G, a pesar de una disminución en M (6,6 kg/kg). Tampoco fueron observadas diferencias para variables sanguíneas. En Exp2, se detectó una interacción tratamiento x tiempo (P = 0,0174) para concentración de Zn; ZM resultó mayor para todos los intervalos de tiempo, seguido de Z. Los tratamientos no alteraron parámetros y cinética ruminal o desaparición de DM; pH decreció (6,1; P < 0,05) 12 h posterior a la suplementación. Suministrando más de 20 veces el requerimiento de Zn no afectó substancialmente productividad o digestión

Parâmetros ruminais e síntese de proteína metabolizável em bovinos de corte sob suplementação com proteinados contendo diversos níveis de proteína bruta Ruminal fermentation characteristics and protein fraction effects on metabolizable protein synthesis of beef cattle fed different levels of crude protein

Avaliaram-se os efeitos dos níveis de nitrogênio de suplementos proteicos sobre as concentrações de nitrogênio amoniacal (N-NH3) e ácidos graxos voláteis (AGV) e o pH em bovinos de corte em pastagem de capim-marandu (Brachiaria brizantha, cv. Marandu). Foram realizadas estimativas da síntese microbiana, do aporte de proteína nãodegradável no rúmen (PNDR) e proteína endógena e das suas contribuições no pool de proteína metabolizável (PM). Quatro bovinos Nelore com 395 &plusmn; 9 kg, fistulados no rúmen, foram utilizados nas medidas dos parâmetros ruminais e nas avaliações da degradabilidade, da cinética ruminal e das estimativas de síntese microbiana em um delineamento quadrado latino 4 &#215;4. Suplementos com 30, 40 ou 50% de proteína bruta (PB) foram fornecidos na quantidade de 400 g/animal.dia para comparação a um grupo controle, sem suplementação proteica. Os animais foram mantidos em pastagens de Brachiaria brizantha, cv. Marandu, distribuídos em quatro piquetes com área de 1,0 ha cada, com oferta do suplemento e retirada das sobras, realizada diariamente. As concentrações de N-NH3 nos animais que receberam o suplemento com 50% PB foram superiores às observadas naqueles sob suplementação com 40% PB e no grupo controle, mas foram semelhantes às observadas no grupo sob suplementação com 30% PB. As concentrações de AGV no grupo sob suplementação com 30% PB foram superiores às observadas no grupo controle e semelhantes às obtidas com suplementação com 40 e 50% PB. O pH não diferiu entre os grupos. A estimativa de oferta de proteína microbiana e de PNDR foi maior para os animais sob suplementação com proteína em relação à observada no grupo controle.<br>The effects of nitrogen levels of protein supplements were evaluated on the concentrations of ammonical nitrogen (N-NH3), volatile fatty acids (VFA's) concentrations and pH in beef cattle grazing Brachiaria brizantha cv. Marandu. The microbial protein synthesis, ruminal undegradable protein (RUP) and endogenous crude protein (ECP) and their contributions to the pool of metabolizable protein (MP). Four Nelore steer, 395 &plusmn; 9 kg, fitted with ruminal cannulas, were used to evaluate ruminal parameters, degradability, ruminal kinetics and microbial synthesis in a 4 &#215;4 Latin square design. The animals were supplied with 400g/head/day of supplements containing 30, 40, and 50% crude protein (CP) for comparison with a control group without protein supplementation (C). The animals grazed Brachiaria brizantha cv Marandu, distributed in four one-hectare paddocks where the supplements were offered and the orts removed daily. The N-NH3 levels in the animals that received 50% CP were higher than those observed in animals receiving 40% CP and C, but were similar to the levels observed in the animals supplemented with 30% CP. The VFA concentrations in the group supplemented with 30% PB were higher than the control treatment (C) and similar to those obtained with 40 and 50% CP supplementation. The pH did not differ among the groups. The microbial synthesis and RUP were greater for the animals that received protein supplementation compared to the control treatment