Pasture Height of A Tropical Erect Grass Affecting Young Lamb Herbage Intake And Performance

Tropical erect grass pastures have high forage production potential in subtropical and tropical regions of the world. However, in this kind of pasture, the body weight gain of weaned lambs is usually below of their potential. We determined the effect of pasture height of an erect tropical grass, consequently its structure, on intake and performance of young lambs. The experiment was repeated in two years. Thirty young weaned lambs (4-5 months) were assigned, each year, to three Panicum maximum pasture heights: 1) Tall-75 cm; 2) Medium-50 cm and 3) Short-25 cm. Herbage mass, pasture height, plant morphological composition, pasture nutritional quality, lamb’s average daily gain, gain per hectare and herbage intake were measured. The experiment was installed in a completely randomized design, evaluated in two periods each year. The Short treatment presented, on average and for longer, the highest leaf:stem ratio (1.3 ± 0.23) and average daily gain (91 ± 10 g/day) in relation to the Medium and Tall treatments (68 ± 10 and 40 ± 13 g, respectively). There was a significant interaction between treatment*period for herbage intake. The Tall treatment showed a marked decrease in intake from the first to the second period. The pasture height management interferes in the speed at which the number of stems increases of a tropical erect grass, in relation to leaves. For a better performance of weaned young lambs during summer-autumn period, it is important to manage tropical erect grass pastures at lower height than is generally recommended, lower than 25 cm.

Low-Intensity, High-Frequency Grazing Strategy Increases Herbage Production and Beef Cattle Performance on Sorghum Pastures

We assessed the effects of high-intensity and low-frequency (HILF) vs. low-intensity and high-frequency (LIHF) grazing on herbage production and performance of beef cattle grazing sorghum pastures. The experimental design was a complete randomized block with two treatments and four replicates (paddocks), carried out in 2014/15. The management target of 50 and 30 cm for pre- and post-grazing, respectively, a LIHF grazing management strategy oriented to maximize beef cattle herbage intake per unit time, was compared with a HILF grazing management strategy of 80 and 20 cm for pre- and post-grazing, respectively, aiming to maximize herbage accumulation and harvest efficiency. Sixteen Brangus steers of 15-month-old and 265 ± 21 kg of live weight (LW) were randomly distributed to paddocks (experimental units). The LIHF resulted in shorter rest periods when compared with the HILF. The greater leaf lamina mass in LIHF allowed greater sward light interception at post-grazing, resulting in greater total herbage production than HILF (7581 and 4154 kg DM/ha, respectively). The average daily gain (ADG) of steers was greater for the LIHF than for the HILF treatment (0.950 and 0.702 kg/animal, respectively); however, even with a greater stocking rate in the HILF, there was no difference for LW gain per ha, with an average of 4 kg LW/ha/day. Our findings demonstrated that the LIHF strategy that is based on offering to the animals an optimal sward structure to favor the maximum herbage intake rate fosters greater herbage production, harvesting efficiency, and ADG without compromising LW gain per area of beef steers, despite the lower herbage harvested per stocking cycle.

PSIV-8 Effect of pre-grazing herbage mass, post-grazing sward height and finishing diet on performance of late-maturing beef steers

Grazing sward structure can influence animal performance in forage-only and forage plus concentrate-based production systems. The objective was to determine the effects of pre-grazing herbage mass (PGHM), post-grazing sward height (PGSH) and indoor finishing diet on performance of weaned, spring-born beef steers. Steers (n = 96, ca. 12 months of age, 396 ± 20.1 kg) previously fed grass silage only over the first winter, were assigned to one of twelve grazing groups, balanced for live weight. Grazing groups were randomly assigned to a two PGHM (1500 or 2500 kg DM/ha) × two PGSH (4 or 6 cm) factorial arrangement of treatments (n = 3 groups/treatment). Steers rotationally grazed Lolium perenne-dominant swards (not mechanically topped) for 222 days. Steers were then accommodated indoors and offered grass silage only (SO) or grass silage + 3.8 kg concentrate DM/head daily (SC) for a 146 day finishing period. Data were analysed using the mixed procedure of SAS with terms for PGHM, PGSH, finishing diet and their interactions in the model. Grazed herbage intake was unaffected by PGHM but was greater for PGSH-6 than PGSH-4 (6.94 vs. 6.18 kg DM/day; P < 0.001). Steer average daily gain at pasture was greater for PGHM-1500 than PGHM-2500 (0.65 vs. 0.60 kg; P < 0.05) and for PGSH-6 than PGSH-4 (0.70 vs. 0.55 kg; P < 0.001). After indoor finishing, carcass weight was unaffected by PGHM, but was heavier for PGSH-6 than PGSH-4 (386 vs. 367 kg; P < 0.01); carcass traits were unaffected by PGHM or PGSH. Carcasses were heavier (+43 kg), fatter (P < 0.001) and more conformed (P < 0.01) for SC than SO. In conclusion, both PGHM-2500 and PGSH-4 restricted animal growth at pasture; however, following an indoor finishing period, carcass weight did not differ between PGHM, but was heavier for PGSH-6 than PGSH-4.

Herbage mass and allowance and animal genotype affect daily herbage intake, productivity, and efficiency of beef cows grazing native subtropical grassland

The beef sector in Campos grasslands must increase animal productivity without external inputs while reducing environmental impact. The objective of this study was to estimate herbage intake [g/metabolic body weight (MBW)/d] of straightbred (Hereford/Angus) and crossbred (F1 of Hereford x Angus) beef cows grazing subtropical native grassland with High and Low herbage allowance (HA, 5 vs 3 kg DM/kg BW) during gestation and lactation and its relationship with biological efficiency of cow-calf productivity. Herbage intake (estimated via n-alkanes C32:C33 ratio) was measured during early (Ge1, -163 d prior calving) and mid to late [Gm1 (-83) and Gm2, (-90 d prior calving)] gestation and lactation (L0, L1 and L2, 60, 47 and 31d following calving) periods in 24-36 cows, selected to create 8 groups (4 per block) of HA x cow genotype treatment. Cows grazed native grassland year-round, under High and Low HA (except in winter). We analyzed the effect of cow genotype (straightbred vs. crossbred cows) and HA (High vs. Low) on herbage mass and height, daily herbage intake rate (DMI), cow body condition score (BCS), calf average daily gain (ADG) and body weight at weaning (BWW) and g of calf weaned/kg DMI. High allowance improved DMI during lactation periods (High 115.6 vs Low 94.1±5.3 P<0.05 g/MBW/d). Crossbred cows decreased DMI during gestation (crossbred 81 vs. straightbred 94±4.3 P=0.05 g/MBW/d) compared to straightbred cows. Crossbred and High HA improved biological efficiency, 40.0 vs. 26.2 and 36.0 vs. 29.7 g of calf/kg DMI respectively. High allowance increased herbage mass and sites with greater canopy height which allow greater DMI, positively associated with cow BCS at weaning, calf ADG, BWW, and g of calf/kg DMI. Crossbred cows reduced DMI during gestation showing no greater annual DMI. Animal productivity and biological efficiency can be improved using High HA and crossbred cows, which should decrease the environmental impact of cow-calf systems.

Herbage intake by steers grazing in a natural grassland with predominance of Andropogon lateralis Nees managed under different canopy heights

ABSTRACT: The animal performance on pasture is directly correlated to canopy structure since this influences the herbage consumption. This study was evaluated the effects of four pre-grazing canopy heights (12, 20, 28 and 36 cm) of Andropogon lateralis Ness on herbage intake and feeding behavior of steers in a natural grassland under intermittent stocking management, using the same proportion of defoliation (40% reduction in pre-grazing height, i.e., post-grazing heights of 7.2, 12.0, 16.8 and 21.6 cm). The experiment was conducted on a total area of 14,000 m2, divided into sixteen paddocks of 875 m2. Thirty-two steers were used, divided into uniform pairs according to the live weight (LW) at the start of the experiment (244 ± 23.0 kg). Each paddock was subdivided into three plots of identical area; the first two plots were used for the adaptation period and the third for the assessment period. A randomized block design was used with four replicates and two assessment periods. Herbage mass and neutral detergent fiber content increased linearly (P < 0,001) with the increase of pre-grazing canopy heights. In contrast, was not affected by treatments, with mean values of 75 g/kg of dry matter (DM) in the upper stratum and 83 g/kg of DM in lower stratum. The herbage intake was similar between treatments (P = 0.255), averaging 1.78% LW. Grazing time increased linearly in the upper stratum and decreased linearly in the lower stratum with increasing pre-grazing canopy heights. Total time spent grazing, ruminating, and idling did not differ between treatments, with means of 52.6%, 23.0%, and 24.2%, respectively. Pre-grazing canopy heights treatments, based on the predominant species A. lateralis, did not affect the daily herbage intake of steers.

Defoliation Dynamics in Kikuyugrass Pastures Subjected to Intensities of Defoliation

Some recent papers have recommended moderate intensities of defoliation in order to maximize herbage intake at different time-scales. Most of them, however, did not assess the grazing dynamics of individual tillers during the stocking period. Therefore, the objective of this work was to describe the defoliation dynamics of kikuyugrass (Pennisetum clandestinum Hochst ex. Chiov) pastures subjected to different intensities of defoliation (40, 50, 60, and 70% of the initial height). Twelve 1500 m2 plots were strip-grazed over 24 h, and the frequency and severity of defoliation of individual tillers were assessed in 40 tagged tillers per experimental unit. From these data (n = 1920), we calculated the grazed area in the upper, second, and third horizon, and the total grazed area. We found that the frequency of defoliation by leaf category (expanding, mature, and senescent) increased linearly with the intensity of defoliation, and that reductions in extended tillers could not be used as a proxy to estimate the frequency of defoliation. Moreover, 22% of the second and third horizons were already exploited with intensities of defoliation of 40%, raising the possibility that the exploitation of lower grazing horizons could be more related to stocking density and relatively independent of the grazed area.

Wild Herbivore Forage Preferences in Semi-Natural Mountain Hay-Meadows

In the context of increasing grassland abandonment we observed wild herbivore impact on the vegetation in order to understand their influence. To quantify semi-natural grassland usage by wild herbivores, we determined grazing intake in semi-natural hay-meadows surrounded by forest vegetation. Grazing exclusion cages were placed at three locations in the Valea Mare village area situated in Bistriţa-Năsăud County, Romania, from 1 April 2014 – 5 October 2014. Sampling took place at two times during this period, first shortly before the hay meadows were mowed and second at the end of the vegetation growing season. Herbage air dry matter yield was measured using two types of observation plots (cage protected plots and unprotected plots). Plant composition on the studied hay-meadows was analyzed using PC-ORD (in order to explain the preference of herbivores for each location. Although herbage production did not vary significantly between locations, the herbage intake of total dry matter production did vary between locations. Wild animals grazed through the entire growing season and based upon the floristic composition analyses we explained differences in herbage intake based on plant species preference. The management of these meadows maintains an offer of good quality forage throughout summer, and the forest surrounding grasslands provides cover when needed. In order to inhibit woody vegetation and to conserve species-rich open landscape further observation need to be made about the optimal deer species densities.

An on-farm rotational grazing trial: restricting access time to pasture did not affect the productivity of a dairy sheep flock in spring

In the Mediterranean area, semi-extensive mixed farming systems characterise the inland landscape and guarantee the maintenance of several agroecosystem services. Rationed and rotational grazing have been proposed as efficient agroecological practices for sustainable intensification. Previous studies have highlighted that, during spring, restricted access time to pasture of below four hours per day decreases herbage intake and milk production of rotationally stoked ewes. The aim of this study was to assess the effect of restricted access time on daily herbage intake and milk productivity of Sarda ewes under rotational grazing management in a real farm located in southern Tuscany. The entire flock of 145 lactating ewes was allotted two homogenous groups and rotationally stoked on a grass-legume mixed pasture and fed about 1.7 kg of DM ewe-1 d-1 of supplementation. Each group was then assigned to the following treatments: two hours per day of access time to pasture, from 10:00 to 12:00 CET, and four hours per day of access time to pasture, from 10:00 to 14:00 CET. Data on herbage yield and quality, dry matter intake and milk yield were collected from April 5 to May 10, 2018. The rotational grazing schedule was conducted allowing for abundant herbage and exploiting high-nutritive biomass of the upper horizon sward. The results of our on-farm experiment showed that restricting daily access time to pasture down two hours did not reduce the potential daily herbage intake and the milk performance of dairy ewes rotationally stocked on a mixed pasture in spring. Our study also highlighted the capacity of ewes to self-regulate the herbage intake in order to meet their energy requirements, when neutral detergent fiber is not a limiting factor. Our outcomes should encourage researchers and farmers to co-design further on-farm experiments.