Rotational grazing increases purple prairie clover frequency in the rangeland plant communities under semi-arid environment

Purple prairie clover (PPC, Dalea purpurea Vent.) is a grazing tolerant perennial legume with good nutritional quality and is widely distributed across North America. Deferred rotational grazing (DR) and continuous grazing (CG) are the most widespread grazing systems on North American grasslands. We conducted a 10-year grazing study to assess the effects of environmental factors and grazing on the frequency of PPC in plant communities. The results showed that the frequency of PPC decreased and then increased with increasing precipitation under CG (P<0.05), while there was no significant change under DR (P>0.05). Meanwhile, PPC frequency increased with temperature under DR (P<0.05), but did not change under CG (P>0.05). Both grazing systems and the number of grazing years had a significant effect on PPC frequency (P<0.05), and there is no interaction between those two factors (P>0.05). We found that from 2011 to 2020, the growth rate of PPC population is 18.24% and 11.69% per year under DR and CG grazing, respectively. Moreover, after 10 years of grazing, the PPC increase in DR was 22.86% higher than that of CG. Thus, selecting the DR grazing system can increase PPC and is an effective practice for coping with environmental changes.

Seasonal epidemiology of gastrointestinal nematodes of cattle in the northern continental climate zone of western Canada as revealed by internal transcribed spacer-2 ribosomal DNA nemabiome barcoding

Background Gastrointestinal nematode (GIN) epidemiology is changing in many regions of the world due to factors such as global warming and emerging anthelmintic resistance. However, the dynamics of these changes in northern continental climate zones are poorly understood due to a lack of empirical data. Methods We studied the accumulation on pasture of free-living infective third-stage larvae (L3) of different GIN species from fecal pats deposited by naturally infected grazing cattle. The field study was conducted on three organic farms in Alberta, western Canada. Grass samples adjacent to 24 fecal pats were collected from each of three different pastures on each farm. Internal transcribed spacer-2 nemabiome metabarcoding was used to determine the GIN species composition of the harvested larvae. The rotational grazing patterns of the cattle ensured that each pasture was contaminated only once by fecal pat deposition. This design allowed us to monitor the accumulation of L3 of specific GIN species on pastures under natural climatic conditions without the confounding effects of pasture recontamination or anthelmintic treatments. Results In seven out of the nine pastures, grass L3 counts peaked approximately 9 weeks after fecal deposition and then gradually declined. However, a relatively large number of L3 remained in the fecal pats at the end of the grazing season. Nemabiome metabarcoding revealed that Cooperia oncophora and Ostertagia ostertagi were the two most abundant species on all of the pastures and that the dynamics of larval accumulation on grass were similar for both species. Daily precipitation and temperature across the whole sampling period were similar for most of the pastures, and multiple linear regression showed that accumulated rainfall 1 week prior to sample collection had a significant impact on the pasture L3 population, but accumulated rainfall 3 weeks prior to sample collection did not. Conclusions The results suggest that the pasture L3 population was altered by short-term microclimatic conditions conducive for horizontal migration onto grass. Overall, the results show the importance of the fecal pat as a refuge and reservoir for L3 of cattle GIN on western Canadian pastures, and provide an evidence base for the risk assessment of rotational grazing management in the region. Graphical Abstract

Rotated grazing in Brachiaria brizantha cv. marandu to improve milk production

In dairy properties, in order for there to be an increase in profit, it is necessary to increase the efficiency of production factors, especially nutrition, which impacts the fixed cost. Increasingly, a balance is sought between the supply of feed and pasture. The rotational grazing method has been adopted by several producers, as it has good productivity in a smaller area. However, the pastures used in this type of grazing, despite their excellent quality, have higher nutritional requirements. The objective of this work was to carry out an economic analysis of the cost of milk production, through the implantation of rotational grazing, and exchange of native pasture for Brachiaria brizantha cv. marandu, on a family farm. This work was prepared in the city of Foz do Iguaçu. An area of ​​6300m2 was used, divided into 28 paddocks of 225m2 using an electric fence. The total cost of production was R$6,047.40, with a positive margin of R$5.143.61 per year. According to the results obtained in the economic analyses, it is concluded that the implantation of rotational grazing and the exchange of native pasture for Brachiaria brizantha cv. Marandu is a viable management, since the income generated by the sale of milk was sufficient to cover the total costs of production.

Does Rotational Grazing Based on Leaf Expansion Duration Modify Grazing Behavior and Feed Intake of Beef Heifers on Natural Grassland?

Grasslands develop a multifunctional role to humanity, with unique fauna and flora, besides being the primary feed source for herbivores. However, grasslands are usually considered a low-efficiency production system, often converted into other land uses such as crops and forestation (e.g., south Brazil). This study aimed to evaluate the effect of two rest intervals between grazing occupations in rotational grazing on the grazing behavior and feed intake of beef heifers. Two grazing intervals, 375 and 750 DD (degree-days) were used; based on the cumulative thermal sum necessary for the leaf expansion of native grasses of two functional groups. The experiment was conducted as a completely randomized block design, with two treatments, three replications, and repeated measures over time. The grazing behavior was evaluated continuously for 18 hours (7 a.m. to 11h59 p.m.). Herbage intake was estimated using an external marker (Cr2O3) in four periods (one for each season). The green leaf mass was similar between treatments, with a mean of 40% of the pregrazing mass (kg DM ha-1). On average grazing, time was 50% of the period, and the bite rate was 38.7 bites min-1. The number of daily meals was 6.5, with an average of 84 minutes for each meal. The number of feeding times (feeding stations by minute) visited was 6.4. On average, there was a 2.23% difference in dry matter intake (% BW) among seasons. Neither ingestive behavior or forage consumption of heifers was affected by the treatments, both maintain similar chemical composition on natural grassland.

DETERMINATION OF ANIMAL LOAD AND GRAZING SYSTEM IN THE WEIGHT GAIN OF BOVINES WITH SECONDARY VEGETATION FEEDING

The present study was to evaluate the weight gain of bovinesin three animal loads with two grazing systems and three levels of grazing, furthermore to evaluate the botanic composition of secondary vegetation areas. The study was carried out during two years, in the first year, the animal loads used were 0.25, 0.50 and 0.75 animal unit per hectare (AU/ha).The vegetation which animals were evaluated was secondary vegetation of 8 years old. Botanic composition was determined by transects at the beginning of experiment. The two systems used were rotational and alternate grazing with three animals per each load and system.The initial average weights were 175 kg and evaluation were carried out each 56 days. The experimental design used was random totally with factorial arrange of 3X2, the first factor was the animal load and the second was the grazing system. Results indicated changes in botanic composition caused by grazing effect (P≤0.05), furthermore, grazing system and animal loads showed significative statistical differences between treatments and interaction. The best weight gain was 520 g of weight gain average per day detected in 0.50AU/ha with rotational grazing system (P≤0.05).