Desempenho de novilhas de corte em pastagens perenes de verão e anuais de inverno em sistema de integração lavoura-pecuária

Abstract

The growth and evolution of Brazilian cattle production are related to methods of improvement on the management and the use of pastures. This research was designed with the objective of developing processes that can contribute to the improvement of integrated agricultural production systems. This study consists of two experiments; in the first one, the evaluated treatments were two genera of tropical perennial forage Megathyrsus maximus cv 'BRS Quênia' and Cynodon spp cv 'Tifton 85' in a grazing system without supplementation. Twenty-seven Purunã heifers with an average age of 18 months and initial average body mass of 312.15 kg were used in a completely randomized design. Weighing was carried out in periods of 28 days, after fasting for 18 hours. In addition to bromatological analysis, average daily gain (ADG) and gain per area (GPA), stocking rate, and subcutaneous fat thickness were evaluated. Bromatological analysis showed no differences in Crude Protein (CP) values (P=0.30); Neutral Detergent (NDF) and Acid (ADF) Fibers, and Lignin (P=0.07) between Tifton 85 and BRS Kenya. The Kenya cultivar allowed greater gain per area when compared to Tifton 85 in the first two periods of pasture use (P<0.05), which did not occur in the other cycles (P>0.05). The second experiment took place in a period subsequent to the previous study and evaluated three different pasture-mixture of temperate forages, examining the same parameters previously evaluated. Thus, the treatments were: T1 – White oat (Avena sativa L.) cv. IPR Esmeralda + triticale (X Triticosecale Wittmack) cv. IPR Prata; T2 – Black oat (Avena strigosa Schreb) cv. IAPAR 61 + rye (Secale cereale L.) cv. IPR 89 and T3 – Black oat cv. IAPAR 61 + vetch (Vicia sativa L.) cv. IAPAR 83. All treatment combinations were supplemented with 0.8% of BW. Twenty-seven Puruna heifers were utilized. Crude protein (CP) concentration was greater in T1 (16.14%), intermediate in T2 (14.91%), and lower in T3 (14.68%); (P<0.05). Treatments did not affect the adipose tissue deposition (P>0.05), loin and rump adipose tissue mass – similar results were observed for average daily gain (ADG). Treatment 1 (White oat + triticale) increased the gain per area compared to the other two pasture mixes (P<0.05). Based on the results, pasture-mixtures along with grain supplementation are important feeding strategies for the diversification of winter crops in Southern Brazil, increasing stocking rates, and greater ADG and GPA when compared to conventional animal production systems nationwide.