Biological and economic responses to increasing nitrogen rates in Mombaça guinea grass pastures

Nitrogen fertilization has been recognized as an essential tool towards the establishment of sustainable intensification of pasture-based livestock systems using tropical perennial grasses if, for a given ecosystem it is capable of increasing forage growth, stocking rates and animal performance. This study assessed pasture growth traits, nutritive value, animal and economic responses of Panicum maximum cv. Mombaça guinea grass pastures subjected to different levels of N fertilization (100 (N100), 200 (N200), and 300 (N300) kg N ha⁻¹ yr⁻¹). Pastures were managed under rotational stocking to maintain similar pre (80–90 cm) and post-grazing (45 cm) canopy heights. A partial budget and a Benefit–Cost Analysis were used to assess the economic returns on increasing N fertilization. N300 resulted in greater post-grazing herbage mass. A slightly higher neutral fiber and acid lignin detergent was observed at N100 (P < 0.05); crude protein increased linearly, and in vitro digestible organic matter reached maximum value at 265.4 kg N ha⁻¹ yr⁻¹. Annual averages of animal weight gain were 515, 590 and 660 g d⁻¹, respectively, for N100, N200 and N300. There was a decrease from 3.7 to 1.9 kg of body weight gain per kg of additional N applied when increasing N rates from 100 to 200 and from 100 to 300 kg ha⁻¹. The net profit improved with increasing N levels, but at reducing rates, reaching its maximum at the N300 level. The change from 100 to 200 kg N ha⁻¹ presented the best return, with USD 3.73 for each additional dollar invested, while the change from 200 kg N ha⁻¹ to 300 kg N ha⁻¹ was economically less than optimal, recouping only USD 1.60 for each dollar. The N300 rate presented the highest net profit per hectare (accounting profit), even in a pessimist scenario (25% reduction in production). Despite being profitable, the N300 rate was less than optimal from an economic standpoint, since an additional 100 kg of Nitrogen ha⁻¹ to change from N200 to N300 level reduced both the net returns and the Benefit–Cost ratio. Our results suggest that the economically optimal level of N fertilization for Mombaça guinea grass pasture should be between 200 and 300 kg ha⁻¹.

Ewe performance in the post-weaning phase and structural characteristics of Brachiaria brizantha cultivars in the dry season

The objective of this study was to examine the performance of ewes in the post-weaning phase and the structural characteristics of Brachiaria brizantha cultivars in the dry season. The treatments were represented by four Brachiaria brizantha cultivars (Piatã, Marandu, Paiaguás, and Xaraés), which were evaluated in a randomized-block design with two replicates for the forage variables and eight replicates for the animal performance variables. Canopy height, masses of forage and morphological components and chemical composition of morphological components were evaluated. Thirty-two ½ Santa Inês and ½ Dorper sheep with an initial body weight (BW) of 22.7 ± 1.2 kg were used. Average daily gain (ADG – kg animal-1 day-1), stocking rate (in animal units [AU] = 30 kg of body weight) and weight gain per area (kg ha-1 day-1) were measured. There was no cultivar effect (p > 0.05) on the structural characteristics of the pasture. The highest crude protein content in the leaf blade (11.8%) were found in cultivar Marandu. Average daily gain was higher in the animals that grazed on cultivar Marandu (0.08 kg animal-1 day-1) as compared with cultivars Xaraés (0.05 kg animal-1 day-1) and Piatã (0.04 kg animal-1 day-1), whereas the ewes that grazed on cultivar Paiaguás showed intermediate ADG values (0.06 kg animal-1 day-1). There was no difference between the cultivars for stocking rate (9.2 AU). Weight gain per area was highest in cultivar Marandu (0.33 kg ha-1 day-1) and lowest in cv. Piatã (0.16 kg ha-1 day-1). Brachiaria brizantha cultivars Piatã, Marandu, Paiaguás and Xaraés proved to be forage options for the post-weaning phase of ewes supplemented with concentrate in the dry season.

Prediction of dry matter intake by meat sheep on tropical pastures

This study was undertaken to determine whether equations for prediction of dry matter intake (DMI) by meat sheep are valid for animals raised solely on tropical pastures and to propose a new equation to predict the DMI of sheep raised on tropical pastures. The DMI prediction from published equations was evaluated by regressing the predicted and observed values, using the F test, for the identity of the parameters (β0 = 0 and β1 = 1) of the regression of predicted on observed data. If the null hypothesis is not rejected, the tested equation accurately estimates DMI. The proposed equation was evaluated in the same way as the published equations. The animal performance and pasture structure and chemical composition data used originated from an experiment conducted with 32 Santa Inês sheep raised on tropical pastures. In the analysis of model adequacy, the null hypothesis was rejected (P < 0.001) and the equations generated predictions that differ (β0 = 0 and β1 = 1) from the DMI observed under practical feeding conditions for grazing sheep. The proposed equation, DMI (%LW) = 7.16545 (± 0.76522) - 0.21799 (± 0.01812) * LW + 0.00273 (± 0.00034) * LW²-0.00688 (± 0.00299) * GT + 0.000007 (± 0.000002) * GT² + 0.00271 (± 0.00108) * GHA, where LW is live weight (kg), GT is grazing time (min/day), and GHA is green herbage allowance (kg DM/100 kg LW), should be used to more accurately predict DMI by grazing sheep.

Grazing intensity as a management strategy in tropical grasses for beef cattle production: a meta-analysis

Correct pasture management associated with the adjustment of grazing intensity determines pasture persistence and the level of production per animal and per land area. The objective of this review was to examine the effect of grazing intensity in tropical pastures on the performance and productivity of beef cattle by a meta-analytical approach. The review followed a protocol developed and tested based on the PICOS strategy to formulate the guiding question: population (beef cattle), intervention (high grazing intensities), comparison (low grazing intensities), outcome (animal performance and productivity), and study design (experimental). Data were collected from papers published in the electronic databases of SCOPUS (Elsevier), Web of Science (Main collection), SpringerLink, Wiley Online Library, and Science Direct (Elsevier) by a single cross-reference search. The selected studies were considered relevant when they: (1) were primary research published in the format of a research article; (2) included grazing intensities as a management strategy; and (3) evaluated average daily gain (ADG, kg/animal per day), stocking rates (SR, animal unit (AU)/ha; AU = 450 kg), and weight gain per area (WGH, kg/ha). Thirteen manuscripts were selected due to their methodological strength for data extraction. The means under continuous stocking were 0.67 kg/animal per day for ADG, 518.12 kg/ha for WGH, and 4.19 AU/ha for SR. Under intermittent stocking, the means were 0.62 kg/animal per day for ADG, 980.18 kg/ha for WGH, and 5.10 AU/ha for SR. In tropical forages, the heights of 20 to 40 cm for pastures under continuous stocking and the defoliation intensities of 40 to 50% for those under intermittent stocking result in greater individual performance and animal productivity per land area.

Intake, digestibility and feeding behaviour of grazing dairy cows supplemented with common bean (Phaseolus vulgaris L.) residue

Context In Brazil, dairy cattle pasture-based systems use grass pasture as the main feed source, with little or no supplementation. However, it is necessary to invest in nutritional technologies that allow dairy cattle systems to produce milk with a high protein and energy content, and better total bacterial counts at low costs. Aims This study aimed to evaluate the effect of adding a common bean residue (CBR) to cattle diets on feed intake, digestibility and feeding behaviour of lactating dairy cows. Methods Eight lactating Holstein × Zebu crossbred cows, with an average bodyweight of 500 ± 30 kg (mean ± s.d.) and a mean daily milk yield of 13 ± 2 kg/cow were randomly assigned in a double 4 × 4 Latin square. The treatments consisted of four increasing levels of CBR (134, 240, 348 and 449 g/kg) in the concentrate. Key results The inclusion of CBR linearly decreased (P ≤ 0.034) the DM intake and neutral detergent fibre intake of pasture, sugarcane and the total diet. The inclusion of CBR did not affect (P ≥ 0.111) grazing, rumination or idle time. The feeding efficiency in kg DM/h and kg neutral detergent fibre corrected for ash and protein/h linearly decreased (P &lt; 0.001), with an estimated decrease of 39.1 and 23.4 g/h respectively for every 10 g/kg of CBR added to the concentrate. The number of boluses per day and the time spent per ruminated bolus were not affected (P ≥ 0.086) by CBR inclusion. Conclusions The results obtained in this study indicate that the inclusion of up to 240 g/kg of CBR to the diets of lactating dairy cows with a mean daily milk yield of 13 kg, managed on pastures, is recommended. Implications The use of CBR, which has high availability in several countries, may be an alternative to supplying small ruminants.

Performance and ingestive behavior of steers on integrated system using legume and/or energy supplementation

This study aimed to evaluate the effect of a mixture of temperate and legume grasses with or without energy supplementation on the performance and feeding behavior of finishing beef steers. Eighteen Nellore-Zebu steers, average 23 months old and body weight (BW) of 380 kg, were used in a continuous grazing system, in a randomized block experimental design. Treatments were ORS: oat (Avena strigosa Schreb) + annual ryegrass (Lolium multiflorum Lam) + supplementation with corn bran; ORVS: oat + ryegrass + vetch (Vicia sativa L.) + supplementation with corn bran; and ORV: oat + ryegrass + vetch. Evaluations were conducted on pasture (forage mass, sward height, herbage accumulation, botanical composition, and chemical composition) and animal (performance and ingestive behavior). Stocking rate and forage mass were greater in treatments with energy supplementation (ORVS and ORS), thus presenting greater sward heights compared to the treatment without supplementation. There was greater participation of oats and ryegrass when vetch was absent (ORS). The presence of supplement (ORS and ORVS) increased the presence of oat stem. The presence of the supplement caused the contribution of the vetch to be lower, likely because of the higher animal load of these treatments. The higher presence of vetch increased crude protein content in the ORV treatment. The ORS exhibited greater gain per area compared to the ORV. Supplemented animals had lower grazing and greater idle time. The ORS treatment animals spent more time in other activities and consumed supplementation and less time grazing than the other treatments. The absence of supplement (ORV) caused the animals to spend more time grazing. Animals not supplemented showed a higher duration of daily chewing, number of chews per minute, number of daily chews, daily number of bites, and station numbers.

Pasture productivity and quality of Urochloa brizantha cultivar Marandu evaluated at two grazing intervals and their impact on milk production

The present study aimed to evaluate two rotational stocking intervals (GI) over three consecutive grazing periods on forage productivity, crude protein and neutral detergent fibre of Urochloa brizantha cv. Marandu pastures, and the subsequent impact on milk production. Grazing treatments were (1) fixed rest period at 30 days (30-FG) and (2) grazing interval when canopy was intercepting 95% photosynthetically active radiation (95-LI). Eighteen multiparous Holstein × Zebu cows (548 ± 61.0 kg bodyweight, BW) and 70 ± 18.1 days in milk were used. Experiment lasted for 99 days (i.e. 33 days per period). Nine cows with similar milk production and BW were randomly allocated to each GI treatment balanced on milk production and BW. The adjustment of carrying capacity per paddock was made aiming to achieve a post-grazing residual height of 20 cm. For this, additional dry Holstein × Zebu cows (averaging 550 kg BW) were added and removed from the paddocks according put-and-take technique. Data were statistically analysed considering field sites as block (n = 2), GI (30-FG vs 95-LI), periods (three consecutive) and interaction GI × periods. Interactions occurred between GI and periods for pre- and post-grazing height (P ≤ 0.05). Greater pre-grazing height was observed for 30-FG (P < 0.01), but post-grazing height was greater (P < 0.01) for 30-FG only in the third period. GI for treatment 30-FG was ~6 days longer (P = 0.01) than that for 95-LIand light interception was greater (2%) for 30-FG. Total forage, stem and dead material mass per area were greater (P < 0.01) for 30-FG than 95-LI. However, stocking rate was 11.3% greater (P = 0.02) for 95-LI than 30-FG. In the pre-grazing period, 95-LI had greater (P < 0.01) proportion of leaves and a greater leaf : stem ratio, whereas neutral detergent fibre concentration tended to be lower (P = 0.08) and crude protein concentration greater (P < 0.01) in 95-LI than in 30-FG. Daily milk productivity per area and its components were 16–28% greater (P < 0.01) for 95-LI than for 30-FD. These results suggest that GI of Marandu grass determined by light interception at 95% (95-LI) enabled the reduction of GI, improved forage nutritive value and increased milk productivity compared with a fixed 30 days (30-FG) of rest.