No abstract

Pasture intensification through higher stocking rates, nitrogen fertilization and intensified grazing management in beef cattle production optimizes pasture use by increasing the forage harvested. We aimed to assess its effects on the morphogenesis and canopy structure of Urochloa brizantha ‘Marandu’ (marandu palisadegrass) pastures. The treatments consisted of marandu palisadegrass pastures managed under continuous stocking and a canopy height of 25 cm, with different levels of intensification: extensive, semi-intensive, and intensive systems N-fertilized with 0 kg, 75 kg, and 150 kg N ha−1 year−1, respectively, as ammonium nitrate (32% of N), with four replicates (paddocks) in a completely randomized design. Phyllochron (9.8 days) and leaf lifespan (34.7 days) were shorter in intensified pastures, whereas herbage mass was similar among treatments. Extensive pastures had a higher proportion of senescent material; thus, more intensive systems showed higher proportions of leaves and stems, although the leaves-to-stem ratio remained similar across production systems. The defoliation interval was lower in intensive (14.4 days) and higher in extensive (18.7 days) treatments. Thus, pasture intensification accelerates leaf appearance, decreases leaf lifespan, shortens the tiller defoliation interval and increased herbage accumulation rate but does not change herbage mass. The extensive system produces excessive forage losses due to dead material.

This study aimed to evaluate the emission factor of N2O, CH4, and the volatilization of NH3 for the combination of feces or urine with increasing doses of ammonium nitrate in tropical palisade grass pastures. The emission of greenhouse gases was assessed in eight treatments combining feces and urine with doses (75 and 150 kg of N ha−1) of ammonium nitrate, (32% N). The emission factor of N2O was 0.11, 0.19, and 0.17% for feces, urine, and 75 kg N ha−1 year−1 (as ammonium nitrate) and showed an additive linear effect when feces or urine were combined with increasing doses of N fertilizer. The emission factor of CH4 of feces (0.18 kg CH4 animal−1 year−1) was similar irrespective of combination with ammonium nitrate. The N loss by volatilized NH3 has a decreasing linear effect (p < 0.05) for the combination of feces or urine with ammonium nitrate. We concluded that N2O and CH4 emission factors of feces and urine in tropical climate conditions are lower than those reported by the IPCC. However, their N2O emission factors are sharply enhanced when combined with ammonium nitrate. These results may contribute to improvements in national and regional greenhouse gas inventories of livestock production.

Objetivou-se avaliar o efeito da inclusão de níveis crescentes (0, 5, 10, 15 e 20%) de polpa cítrica peletizada (PCP) e melaço em pó (MP) na ensilagem de capim-elefante. O delineamento experimental foi inteiramente casualizado, com 10 tratamentos e cinco repetições. Determinou-se o conteúdo de matéria seca (MS), teores de proteína bruta (PB), fibra em detergente neutro (FDN) e ácido (FDA), lignina (LIG), proteína insolúvel em detergente ácido (PIDA), carboidratos solúveis (CS), potencial hidrogeniônico (pH), nitrogênio amoniacal (N-NH3), perdas por efluentes (PE), perdas por gases (PG) e recuperação da matéria seca (RMS). Foram observados efeitos dos níveis de inclusão da PC e do MP sobre a massa de forragem ensilada. A PCP promoveu aumento de MS e CS, diminuição de FDN, FDA e LIG, e efeito quadrático para a PB. Observou-se redução na PE e PG, resultando em maior RMS com a inclusão deste aditivo. O MP aumentou o teor de MS e diminuiu a FDN, FDA e LIG linearmente. Entretanto, este aditivo promoveu aumento na PE e menor RMS. A PC proporcionou efeitos positivos sobre a silagem e sua inclusão até 10% melhora a qualidade nutricional e evita a redução do teor proteico do material. Por outro lado, o MP apresentou efeitos negativos sobre o teor proteico, perda por EFLU e produção de N.NH3, porém aumentou os teores de MS e CS, bem como as perdas via gás.

The aim of this study was to evaluate the effect of alfalfa hay replacement by tropical legume hay on goat diets. Four diets were formulated using: 1) perennial soybean hay; 2) tropical kudzu; 3) macrotiloma and 4) alfalfa, in a roughage/concentrate ratio of 25/75. Eight castrated crossbred (Boer x Saanen) animals, with a mean weight of 17.8 kg (4 months of age), were arranged in a 4 x 4 double Latin Square Design. Intake of dry matter (DM), organic matter (OM), crude protein (CP), total carbohydrates (TC), ether extract (EE), non-fibrous carbohydrates (NFC) and total digestible nutrients (TDN) were not affected by the legume species. On the other hand, the intake of acid detergent fiber (ADF) was lower in the diet formulated with alfalfa, compared to the other legumes (P<0.05), since this presented lower levels in this diet. The digestibility of DM, OM, CP, ADF, TC and NFC did not differ among the four treatments (P>0.05). However, EE digestibility was lower in the diet with alfalfa compared to ration with tropical kudzu and perennial soybeans. The digestibility of this constituent between the diet formulated with tropical kudzu and those formulated with macrotiloma and perennial soybean (P < 0.05), and the digestibility of the NDF of the ration prepared with perennial soybean was higher than the other legumes. There was no difference for the nitrogen balance between the different diets, indicating that these legumes are options for replacement of alfalfa hay in goat diets.