Teresa Cristina Moraes Genro

From the bite to precision grazing: understanding the plant-animal interface to exploit the multi-functionality of grasslands.

Precision livestock involves innovative technologies to monitor the animal within its pastoral environment. Understanding ingestive behaviour is fundamental to management decisions based upon animal and vegetation monitoring. The way such information can be used is not yet clear. In precision agriculture, the governing principle has been to correct or manage variability so as to homogenise yield at maximized levels. If the same reasoning is applied in livestock production, it can foster classical mistakes in grazing management. However, if precision livestock production can help integrate heterogeneity in managing animals on pasture, then we have a powerful new tool for responding to the new paradigms involving the multi-functionality of grasslands. This paper discusses this concept, and presents the bite as the basic unit of the process to be monitored. A few types of equipment and their application in monitoring site use and the spatial-temporal dynamics of animal biting are presented. The discussion concludes with how to build pastoral environments with precision bite management, and how to create sward structures to influence the temporal and spatial dynamics of animal biting.

Forage Allowance as a Target of Grazing Management: Implications on Grazing Time and Forage Searching

Abstract This work aimed to evaluate the following hypotheses: 1) the daily grazing time (GT) and 2) forage searching are more associated with the sward structure than with the levels of daily forage allowance (FA). To this end we proposed a model that was tested through an analysis of the sward structure, grazing time, and displacement in grazing by heifers on the natural grassland of the Pampa Biome (southern Brazil), which has been managed by FA levels since 1986. For three seasons, between January 2009 and February 2010, we evaluated the effect of FA on the main descriptors of the sward structure (herbage mass, sward height, and tussocks frequency) and the effect of these on the GT, displacement rate (DR), and daily displacement (D) in grazing. The data were analyzed with the use of regression and descriptive analyses from three-dimensional contour graphs with the data of the sward structure and GT. The DR was not associated with the FA levels or sward structure; however, the DR presented a positive linear relationship with the D and GT. The incremental change in the GT was accompanied by an increase in the D. Lastly, independently of the level of the FA and season evaluated, the lower values of GT were always associated with the following structural configuration: forage mass between 1 400 and 2 200 kg DM · ha−1, sward height between 9 and 13 cm, and tussock levels not exceeding 35%. Outside these limits, a penalty occurred in the GT and displacement patterns of the heifers. We found evidence that a better understanding of the cause–effect relationships between the sward structure and the ingestive behavior of the animals demonstrates the possibility of increasing the performance of domestic herbivores with important economic and ecological consequences. Resumen El objetivo del estudio fue evaluar las siguientes hipótesis: (i) si el tiempo de pastoreo diario (TP) y (ii) la búsqueda de forraje están más estrechamente relacionados a la estructura del pasto que a los niveles diarios de oferta de forraje (OF). Con este fin, propusimos un modelo que se puso a prueba en base al análisis de la estructura del pasto, el tiempo de pastoreo y el desplazamiento en pastoreo en terneras sobre un pastizal natural del Bioma Pampa (sur de Brasil) que, desde 1986, se ha manejado con distintos niveles de OF. En tres épocas, entre Ene/2009 y Feb/2010, se evaluó el efecto de la OF sobre los principales descriptores de la estructura del pasto (biomasa de forraje, altura y frecuencia de matas) y el efecto de éstos sobre el tiempo de pastoreo (TP), la tasa de desplazamiento (TD) y el desplazamiento diario (D). Los datos fueron analizados mediante regresión y por análisis descriptivos a partir de gráficos de contorno tridimensionales en base a los datos de estructura del pasto y TP. La TD no tuvo relación con OF ni con la estructura del pasto, pero mostró una relación lineal positiva con D. Incrementos en TP estuvieron asociados a incrementos en D. El estudio demostró la importancia de la estructura del pasto al constatar que, independientemente del nivel de OF y de la época del año evaluada, los valores más bajos de TP siempre estuvieron asociados a estructuras del pasto caracterizadas por una masa de forraje de 1 400 a 2 200 kg MS · ha−1, alturas de 9 a 13 cm y frecuencia de matas en el pastizal menores al 35%. Fuera de estos límites hubo una penalización en el TP y en el patrón de desplazamiento en pastoreo de las vaquillas. Encontramos evidencias de que el mejor entendimiento de las relaciones causa-efecto entre la estructura del pasto y el comportamiento en pastoreo harían posible incrementar el rendimiento de los herbívoros domésticos, con importantes consecuencias económicas y probablemente ecológicas.

Suplementos energéticos para recria de novilhas de corte em pastagens anuais: desempenho animal

It was evaluated beef heifers performance from three until twelve months of age, when they were reared in cultivated pasture soon after their weaning (experiment 1) and in the first winter post-weaning (experiment 2), with or without the supply of energy supplements to the animals. From 02/16 to 04/21/2001, the heifers stayed in Pearl Millet pasture, exclusively under grazing (PAST1); supplemented with milled corn grain (PAST1/C) or supplemented with pellet citric pulp (PAST1/P). From 07/13 to 10/09/2001, the heifers were maintained in oat plus italian ryegrass pasture without supplementation to the animals (PAST2); supplemented with milled corn grain (PAST2/C) or supplemented with soy hull (PAST2/H). The evaluated variables of animal performance were live weight (LW), average daily gain (ADG) and body condition score (BCS). In the experiment 1, supplemented animals presented larger values of final LW, ADG and BCS in relation to the non supplemented, ones the supplemented treatments not differing to each other. In experiment 2, the soy hull supplemented heifers showed greater ADG and final LW than non supplemented heifers, with the corn grain supplemented group in an intermediary position. The highest BCS was obtained by the animals of PAST2/H, followed by PAST2/C and, at last, of PAST2. Beef heifers weaned at 60-90 days should be supplemented in the initial post-weaning period, enabling them to reach satisfactory development in this phase of growth. The by-products citric pulp and soy hull can substitute the corn grain as energy supplements for rearing of beef heifers.

Produção agronômica de uma coleção de acessos de Paspalum nicorae Parodi

This study was carried out to evaluate a collection of 53 accessions of Paspalum nicorae, introduced in two physiographically distinct regions over two years, with the objective of characterizing production and quality of forage of access for subsequent phases of a forage plant breeding program. The accessions were established in lines in randomized block design with three replications and the evaluations were performed from October 2007 to February 2009 by using cuts. There was variation of forage production among access over time and among sites. The majority of the accessions of P. nicorae presented high forage yield when compared with the control (P. notatum cv. Pensacola) and some accessions presented very expressive performances. The percentages of crude protein obtained from accessions in the collection were similar to the ones found in the control access. The accessions 28B and 26A of P. nicorae are indicated for subsequent stages in a program of forage plant breeding.

Suplementos energéticos para recria de novilhas de corte em pastagens anuais: análise econômica

An economic evaluation was accomplished of two experiments with intensive feeding systems for rearing of beef heifers weaned with 60-90 days. In experiment 1, the heifers reared in Pearl Millet pasture, exclusively under grazing (PAST1); supplemented with milled corn grain (PAST1/C) or supplemented with pellet citric pulp (PAST1/P). In experiment 2, the heifers were reared in Oat plus Italian Ryegrass pasture without supplementation to the animals (PAST2); supplemented with milled corn grain (PAST2/C) or supplemented with soy hull (PAST2/H). With the results of animal production per hectare and composition of the costs was realized an evaluation of the direct financial response of the studied feeding systems. Based on the live weight of the heifers at twelve months of age a bioeconomic analysis of the employed technologies was presented. In experiment 1, the milled corn grain supplemented presented financial loss, while other systems just only covered costs, without surplus gross margin. In experiment 2, the corn grain system covered only costs, and the exclusive use of the pasture and the soy hull supplementation provided satisfactory values of gross margin for hectare. The increase of birth rate from 50 to 80% or the reduction of the age at first mating of the heifers from three to two years could reduce, respectively, in 62 and 23% the number of unproductive females in the herd for each 100 pregnant cows. These practices present potentiality to reduce this number of animals in 74%, when accomplished jointly.

Can animal performance be predicted from short-term grazing processes?

Despite all the biotic and abiotic factors affecting foraging by ruminants, there is a common and fundamental process, which is bite gathering. We hypothesised that because the mechanics of bite formation dominate the foraging process, changes in short-term bite mass are reflected in longer-term animal performance across a wide range of sward conditions. We focus at the meal level of foraging, using experiments in which the effect of abiotic factors and digestive constrains are minimised, making intake rate the main currency. We estimated bite mass across a wide range of structural challenges to large-herbivore foraging in a long-term experiment with heterogeneous native grasslands. A conceptual model was developed for average daily gain, where energy gain and energy costs were proximate causal variables. Energy gain was a function of diet quality and components of daily intake rate, where bite mass was the main component estimated. In turn, components of intake rate were determined by sward structure and bodyweight. Energy costs were a function of bodyweight and abiotic conditions. Finally, sward structure, bodyweight and abiotic conditions were determined by experimental treatments, seasons and years. Then, the conceptual model was translated into statistical models that included variables measured or estimated, and coefficients representing all links in the conceptual model. Weight gain was a function of bite mass, forage characteristics, and animal and abiotic conditions. Models were set up to test whether forage and stocking conditions affected monthly gain beyond the effects through bite mass, after correcting for abiotic factors. Forage mass, height and disappearance did help predict monthly gain after bite mass was included in the model, which supported our hypothesis. However, stocking treatments and season had significant effects not incorporated in bite mass. Although the model explained 77.9% of liveweight gain variation, only 35.2% was due to fixed effects, with 10.8% accounted by bite mass and its interactions. Concomitant experiments showed that sward structure (first with sward height and the second with tussock cover) does determine bite mass and short-term intake rate in the complex native grasslands we studied. Yet, other temporal varying components of monthly gain not correlated with bite mass, temperature or wind, added most of the observed variation in monthly animal performance. Part of the model failure to account for variation in performance may be related to a significant and temporally variable grazing of tussocks. We used a bite mass model that assumed no tussock grazing. In light of these results and a parallel experiment, we conclude that tussock grazing must be incorporated in future versions of the model.

Características produtivas e estruturais do milheto e sua relação com o ganho de peso de bezerras sob suplementação alimentar

The productive and structural characteristics of Pearl millet (Pennisetum americanum (L.) Leeke) under continuous stocking rate and their relationship with beef heifers performance exclusively under grazing (PAST), supplemented with corn grain (PAST + C) or citric pulp (PAST + P) was evaluated. There was no difference among treatments for herbage mass, forage allowance, leaf lamina mass, leaf lamina allowance, daily accumulation rate of forage and herbage total production. Daily accumulation rate of forage, leaf lamina mass and leaf lamina allowance decreased linearly during the grazing period. The participation of Pearl millet components in the sward structure was similar among treatments and changed during the time. The energetic supplementation increased the stocking rate at beginning of grazing, with high leaf lamina participation in the canopy and increased the average daily gain in subsequent periods, with decreasing of the leaf lamina participation. The effect of energetic supplementation on Pearl millet pasture is linked with the amount and distribution of leaf lamina in the canopy structure. The energetic supplementation does not affect the structural and productive characteristics of pearl millet.

Produção e qualidade de silagens de híbridos de milho (Zea mays) e de híbridos de sorgo (Sorghum bicolor)

Com o objetivo de avaliar a producao e a qualidade de cinco hibridos de milho (Zea mays) e tres hibridos de sorgo (Sorghum bicolor), foi conduzido um experimento no Departamento de Zootecnia, UFSM. O delineamento experimental foi de blocos casualizados com tres repeticoes. Os tratamentos foram: hibridos de milho - Pioneer 3072 (P 3072), Agroceres 211 (AG 211), Cargill 525 (C 525), Pioneer 3232 (P 3232) e Agroceres 213 (AG 213); sorgo -todos os hibridos foram da Agroceres: AG 2004E, AG 2002 e AG 2005E. A populacao estabelecida foi de 50.000 e 160.000 plantas/ha para milho e o sorgo, respectivamente. As plantas foram cortadas a 15cm do solo, quando atingiram o estadio de grao farinaceo. Posteriormente, os hibridos foram picados e ensilados em vidros vedados, colocados em tubos de concreto e tapados com o material verde restante. Com relacao a producao de Materia Seca, o hibrido P 3072 destacou-se em relacao aos demais, sendo superior (P<0,05) ao AG 213 e aos tres hibridos de sorgo. Para as variaveis de qualidade da silagem, houve diferenca significativa (P<0,05) apenas para o pH, apesar de todos os valores medios obtidos serem adequados para a conservacao da silagem. As estimativas de digestibilidade indicam bom potencial de qualidade para todos os hibridos, especialmente P 3072 e P 3232.

Alterações bromatológicas nas silagens de milho submetidas a crescentes tempos de exposição ao ar após "desensilagem"

The experiment in a completely randomized design aimed at testing the effect of air exposure of maize silages at “feed-out” on chemical composition. Silages were prepared on May 18 th , 2004 from a late season harvest of a crop at the half milky half dough kernel stage and chopped materials were packed in 30 liters mini-silos. Four treatments with four replicates consisted of air exposure of silages removed from the mini-silos after periods of zero, 12 hours, 24 hours or 36 hours until sampling for chemical analysis. Air exposure affected significantly (P<0.05) neutral detergent fiber values (corrected for ashes and protein) and lignin contents, without effects on non-structural carbohydrates and nitrogenous fractions. It is concluded that a 12 hour air exposure period after “feed-out” can affect the nutritive value of maize silage.

Alterações bromatológicas nas frações dos carboidratos de silagens de milho "safrinha" sob diferentes tempos de exposição ao ar antes da ensilagem

The objective of this experiment was to evaluate the effect of corn grain maturity and air exposure time prior to ensiling on the carbohydrate concentration of corn silage from corn crop planted late in the season. A complete randomized design was used with a 2 x 4 factorial arrangement, testing two stages of maturity at harvest (MK - milky kernel and MDK - ½ milky and ½ dough kernel) of maize crops and four air exposure time prior to ensiling: 0, 12, 24 and 36 hours. Harvests occurred in 2004 on April 26th and May 18th. Stage of maturity (M) and periods of air exposure (TE) showed significant effects as well as interactions in most of tested variables. DM content was different according to M and TE. The MK and MDK silages showed different residual sugar and starch concentrations, respectively, 1.51 and 1.31% and 4.23 and 13.21% of DM. Soluble sugars decreased with TE with values of 1.64% (DM basis) with zero h air exposure to 1.05% after 36 hours exposure. The greatest impact of TE was observed on NDFap values (NDF corrected for ash and protein). Even a short 12-hour period of air exposure before ensiling affects negatively the nutritional value of corn silages.