Beginning Of Grazing Research Articles

160 Comparison of native to introduced mixed warm-season grass pastures on heifer weight gain and fecal egg count

Abstract The objective of this study was to compare summer body weight gain and fecal egg count change of spring weaned heifers grazing either native grass (NG; predominately big bluestem [Andropogon gerardii)) or mixed warm-season grass (MWS; predominately bermudagrass (Cynodon dactylon) and crabgrass (Digitaria sanguinalis)]. Pastures (n = 3 per treatment and 2.02 ha each) were continuously stocked with 10 heifers each in yr 1 and 2, respectively. All pastures received 56 kg/ha N mid-May. Grazing began at the end of May and all pastures were grazed for 84 d. Heifers were previously treated with an anthelmintic at weaning (benzimidazole in yr 1 and macrocyclic lactone plus benzimidazole in yr 2). Dependent responses were analyzed for the fixed effect of treatment, year, and their interaction and random effect of pasture. Pasture was the experimental unit. Fecal egg counts as eggs per gram were transformed to a log base 10 value (log10:epg). Average daily gain differed between treatments by year (P = 0.05). In yr 1, NG gained 0.22 kg/d more than MWS; whereas, in yr 2, NG gained 0.11 kg/d more than MWS. Heifers grazing NG were 15.9 ± 3.52 kg heavier than MWS by d 84 (P = 0.01). Change in fecal egg count differed by year (P < 0.001) and tended to be less for NG compared with MWS (P = 0.11). Native grass fecal egg count change was 45% of MWS. Impact of forage system on internal parasite load may be attributed to canopy structure. Native grasses averaged 67 and 81 ± 2.3 cm at the beginning of grazing in yr 1 and 2, respectively (P = 0.01). Native grass height in yr 1 and yr 2 was similar (P = 0.68) by wk 12 and averaged 41 ± 3.2 cm. By comparison, grazing in the MWS system would be much closer to the soil surface. Initial forage mass and forage mass change was greater in NG than MWS and differed by year (treatment × year P = 0.02 and 0.05, respectively). While this study demonstrated beneficial responses to grazing NG over MWS during summer months, further information regarding how these summer forage options compare under varied stocking rate and grazing duration is warranted.

41 Effect of grazing cotton crop residue versus Bermudagrass on performance and economic parameters in late gestation beef cows

Abstract The residual lint, seed, and leaf remaining after cotton harvest was evaluated as a feedstuff to reduce the amount of hay fed to beef cows during early winter. A study was conducted utilizing 36 crossbred Angus cross cows (BW 491.04 kg) in late gestation. Cows were stratified by weight and randomly assigned to one of four groups, and each group was assigned to one of two treatments: Bermudagrass hay (Cynodon dactylon) (HAY), or cotton (Gossypium hirsutum) crop residue + Bermudagrass hay (COTTON). All cattle remained on their respective treatments for 30 d, and BW were recorded before and after the feeding period. Hand-grab samples were collected of cotton residue in each field to quantify residue available at the beginning of grazing. Available residue in the cotton groups were 783.17 kg/acre and 911.13 kg/acre. Core samples were collected from each bale of a single lot of hay. The same lot of hay was used for both treatments. Hay was offered ad libitum for the HAY treatment, and hay was offered to the COTTON treatment, starting on d 19. A completely randomized design was used and data were analyzed using a one way analysis of variance. The CP, NDF, and ADF values for hay and cotton residue were 12.3, 62, and 37%, and 23.5, 66, and 57%, respectively. Average daily gain (1.02 and 0.60 kg) and average weight change (34.5 and 20.4 kg) were higher (P < 0.003) for HAY compared to COTTON cows; however, their subsequent calving and breeding performance in the herd were not affected. Average daily hay disappearance for COTTON (5.90 kg/hd) was lower (P < 0.02) compared to HAY (17.19 kg/hd). Overall daily hay cost per head was lower (P < 0.01) for COTTON compared to HAY ($0.65 and $1.89, respectively). These data show that grazing cotton crop residue can reduce feed cost in late gestation beef cows.

Relationship of rumen fill and fermentation to diurnal and seasonal variation of herbage intake in dairy cows grazed on perennial ryegrass pasture.

To clarify the effect of digesta weight in the reticulorumen on diurnal and seasonal fluctuations in herbage intake, six ruminally cannulated, non-lactating dairy cows were grazed on perennial ryegrass/white clover pasture during morning and evening sessions in spring and autumn. The digesta weight of fresh matter, dry matter (DM) and fiber in the reticulorumen at the beginning and the end of each grazing session was lower in spring than in autumn (P < 0.01). Although the digesta weight was similar between the sessions at the beginning of grazing, it was greater for the evening than for the morning at the end of grazing (P < 0.01). The large particles proportion in the digesta was lower for the morning than the evening (P < 0.01), and it was lower in spring than in autumn (P < 0.01). The concentrations of volatile fatty acids in rumen fluid were generally higher in spring compared with autumn. The herbage DM intake during the evening was greater compared with the morning in both seasons (P < 0.01). However, there was no difference in herbage DM intake between seasons. The results showed that the rumen digesta fill was not the sole factor explaining diurnal and seasonal variation of herbage intake in grazing dairy cows.

Paleodietary reconstruction of fossil horses from the Eocene through Pleistocene of North America

Paleodietary trends for North American horses from Hyracotherium (early Eocene) through Equus (late Pleistocene) were examined using dental microwear analysis. Over 1200 fossil specimens were analyzed for enamel microwear and results were compared to an extensive microwear database of extant ungulates. This study tests the hypothesis that Eocene horses browsed on low abrasion foods whereas Oligocene and later horses had more abrasive diets concomitant with the spread of more open habitats and examines the correlation between the acquisition of hypsodonty and the beginning of grazing. Microwear results indicate that early to middle Eocene species engaged mostly in fruit browsing. In contrast, late Eocene to Oligocene taxa have microwear scratch numbers typical of grazing and mixed-feeding ungulates, but with very fine scratch textures which are unusual in modern C4 grazers and indicate consumption of relatively low abrasion grasses. An increase in overall dietary abrasion is evident beginning in the early Miocene but members of the Anchitherinae (sensu stricto) engaged in leaf browsing while other forms committed to grazing or alternating between grass and leaves. Anchitherinae (ss) continue to rely on leaves until they became extinct in the late Miocene, while members of the Equinae were either grazing or mixed feeding through the Pleistocene. Dietary abrasion increased further beginning in the late Miocene and continued to increase through the Pleistocene. Most Pleistocene horses were not grazing but rather alternating between grass and leaves or even browsing. Increased pitting of dental enamel and coarser scratch textures in Plio–Pleistocene horses reinforces the idea that increased abrasion may be due to grit encroachment on food items and/or a shift toward coarser grasses than due to a steady increase in the amount of grass consumed.

Trapping the Pasture Odorscape Using Open-Air Solid-Phase Micro Extraction, a Tool to Assess Grassland Value.

Besides supporting cattle feeding, grasslands are home to a diversity of plants and insects that interact with each other by emitting volatile compounds. The aim of this work was to develop a method to determine permanent grassland odorscape and relate it to flower-visiting insects. Two grasslands were chosen for their contrasting levels of botanical diversity, resulting from differing grazing managements. Measurements were made over two periods of three consecutive days at the beginning of grazing, and just after the cows had left the plots. Volatile compounds were trapped using solid-phase microextraction (SPME) fibers exposed eight hours a day in three exclosures per plot, and then analyzed by gas-chromatography-mass spectrometry (GC-MS). Insects were trapped using pan traps and a net, sorted and counted. The open air SPME method yielded volatile compound profiles that were richer than maize field profiles, comprising the common green leaf volatiles (GLV) and more specific ones. Differences between the odorscapes of the two grasslands were found, but they were not as marked as expected from their botanical composition. By contrast, there were sharp differences between the two periods, resulting from the combined effects of changes in weather conditions, plant phenological stage and grazing progress. Several correlations between insect counts and volatile compounds were found. Although their correlation coefficients were low, some of them were confirmed when tested by Spearman rank correlation, and could be logically explained. This method of grassland odorscape deserves to be developed because it can provide information on many aspects of grassland function and on the stresses that grassland plants undergo.

The Impact of Cattle Grazing in High Elevation Sierra Nevada Mountain Meadows over Widely Variable Annual Climatic Conditions

The impact of summer cattle grazing on water quality during three very different climatic years in the Sierra Nevada was investigated. Water year 2009 had near normal precipitation; 2010 had late precipitation and snowmelt; and 2011 had 150% above normal precipitation. Surface waters were tested for pathogenic bacteria indicators fecal coliform, E. coli, and total coliform before and after cattle were released onto summer grazing allotments. Water samples were collected from meadow stream sites up to 6 weeks before and up to 6 weeks after cattle grazing began. Streams passing through ungrazed meadow served as controls. Eight sample sites were between 1694 m and 2273 m in elevation; one site was lower at 1145 m in elevation. Samples were transported within 6 hours to a water analysis laboratory, where samples were analyzed following standardized laboratory methods. Results showed that individual site and total mean concentrations of E. coli in surface waters were within regulatory standards before cattle arrived during each of the 3 study years. After the beginning of grazing, mean E. coli counts increased as follows: 2009 from 8 to 240 CFU/100mL, 2010 from 7 to 561 CFU/10mL; 2011 from 7 to 657 CFU/100mL (p < 0.05 all years). Total coliform bacteria and fecal coliform concentrations showed the same pattern. This study shows that cattle grazing in the high elevation Sierra Nevada results in a significant increase in indicator bacteria. This impact on the watersheds occurs despite widely variable annual climatic conditions.

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

Foram avaliadas características produtivas e estruturais do milheto (Pennisetum americanum (L.) Leeke) sob pastejo em lotação contínua e sua relação com o desempenho de bezerras exclusivamente em pastejo (PAST) ou sob suplementação com grão de milho (PAST + M) ou polpa cítrica (PAST + P). Não houve diferença entre tratamentos para a massa e oferta de forragem, a massa e oferta de lâminas foliares, a taxa de acúmulo diário e a produção total de forragem. A taxa de acúmulo diário de forragem, a massa e a oferta de lâminas foliares diminuíram linearmente durante o período de pastejo. A participação dos componentes de milheto na estrutura do dossel foi similar entre tratamentos e variou no tempo. A suplementação energética promoveu aumento da taxa de lotação no período inicial de pastejo, quando houve alta participação de lâminas foliares no dossel, e do ganho de peso médio diário nos períodos subseqüentes, quando houve redução da participação de lâminas foliares. Em pastagem de milheto, a resposta à suplementação energética varia com a quantidade e a distribuição de lâminas foliares no dossel. O fornecimento de suplemento energético aos animais em pastejo não interfere nas características produtivas e estruturais do milheto.

Modelo de simulação de sistemas de pastejo rotativo e contínuo de azevém (Lolium multiflorum lam.) na bovinocultura

O principal objetivo do trabalho é propor um modelo de simulação de sistemas dinâmicos para a análise do manejo de pastagens visando a maximizar o consumo de forragem pelos animais. A forrageira utilizada foi o azevém anual, pastado por bovinos adultos. Foram consideradas diversas variáveis como: lotação animal, taxa de crescimento do pasto, taxa de apreensão da forragem pelos animais, primeira entrada dos animais na pastagem após a emergência (início do pastejo) e ciclo de rotação (soma dos dias de pastejo e de descanso do pasto). Para simular o crescimento do pasto, foi utilizada a equação de Verhulst. Simulações efetuadas em um modelo computacional formulado no aplicativo Berkeley Madonna indicaram que, quando a entrada dos animais no pasto foi mais precoce (até os 73 dias), o sistema rotativo proporcionou um maior consumo de matéria seca pelos animais que o sistema de pastejo contínuo. Já quando a entrada dos animais no pasto foi entre os 74 e os 95 dias, o sistema contínuo proporcionou um maior consumo de matéria seca pelos animais que o sistema de pastejo rotativo. As simulações indicaram também que, quando o pastejo rotativo é iniciado precocemente (60 dias), o ciclo de 30 dias (um dia de pastejo e 29 de descanso) proporcionou maior consumo de matéria seca pelos animais. Já quando o pastejo rotativo é iniciado tardiamente (75 dias), variações da extensão do ciclo de rotação tiveram pouca influência sobre o consumo de matéria seca pelos animais.

Preferences of sheep grazing down conterminal monocultures of Lolium perenne– Festuca arundinacea: Test of an energy intake rate maximisation hypothesis using the short-term double weighing technique

We tested an energy intake rate maximisation hypothesis to predict preferences. In experiment 1, five groups of INRA401 dry ewes (G1–G5) grazed down conterminal monocultures of Lolium perenne (L)– Festuca arundinacea (F), 0.50:0.50 by area, at a stocking rate of 92 ewes ha −1. Both plant species were 220-mm high at the beginning of grazing. Time spent grazing either L or F was measured daily from dawn to dusk in groups G1, G2, G4 and G5, composed of six ewes, using automated cameras. In experiment 2, intake-rate from L and F was measured over two periods (P1 and P2) on a group of 8 dry INRA401 ewes (G3), using the short-term double weighing technique. The four ewes that grazed L in P1 grazed F in P2 and vice versa. Sward height at the beginning of grazing was 220-mm high for both plant species in P1, and 195 and 156 mm for L and F, respectively, in P2. Time spent grazing either L or F was measured during P2. During the first 5 days of the grazing down, ewes spent on average 71% of their grazing time on L. A marked switch to F occurred on day 6 on average. Thereafter, there was no more preference for either species. At the time of the switch and thereafter, mean sward height and green leaf mass were, respectively, 25–30 mm and 50% lower for L than for F, whereas they were similar at the beginning of the depletion. From the switch to F onwards, the decrease in preference for L was mediated via an increase in the time spent grazing F, rather than a decrease in the time spent grazing L. For a given sward height, DM and DOM intake rates (DMIR and DOMIR) were lower from L than from F in both periods. Ratio of DOM intake rate between L and F (DOMIR L/DOMIR F) at the beginning of grazing was 0.74 and 1.08 on average for P1 and P2, respectively. Two days before the switch, it decreased to 0.59 and 0.70 in P1 and P2, respectively. After the switch, it remained at 0.60 and 0.73 on average in P1 and P2, respectively. These results demonstrate that diet selection cannot simply be explained by a strategy that maximises energy intake rate. We observed a marked interindividual variability in preferences. The degree of preference for L was repeatable between years ( P < 0.05) in all but one ewe.

The Influence of Experienced Cattle on Grazing Behaviour of Calves in the Novel Pasture

The objecting of this study was to examine and discuss how experienced cattle influence behaviour, especially grazing behaviour, of unexperienced calves. (1) In experiment 1, 10 castrated calves and 2 cows were grazed in an artificial pasture for one month to familiarize and interact with each other. Then they were separated into 2 groups: one had 4 calves (M1) with 2 cows and another had 6 calves only (C1). Two groups grazed separately on each native pasture with vegetation similar to each other. Grazing time, travelling speed and variety of grazed plants and drinking frequency of calves were compared. C1 behaved nervously only at the beginning of grazing: they moved more, grazed less and they drank more than M1. Later calves in both groups behaved in the same way. (2) In experiment 2, 6 grazing unexperienced calves and 2 grazing experienced heifers were grouped into 2: one consisted of 2 calves (M2) with 2 heifers and another consisted of 4 calves only (C2). The 2 groups were each grazed on artificial pasture. Grazing time and rate of eating were compared between groups. Grazing time of M2 was significantly longer (P<0.05) than C2. Rate of eating in M2 was significantly higher (P<0.01) than in C2. It is thought that the existence of experienced cattle influences behaviour of calves under grazing situations.

Comparison of Beef Cattle Performance and Forage Characteristics for Alfalfa or Tall Fescue-Red Clover in a Rotational Grazing System

Cow-calf performance and diet composition were compared between established alfalfa and tall fescue-red clover pastures in a rotational grazing system. Eighty cow-calf pairs were randomly allotted to the two dietary mixtures with three replications. Each of the six pastures was subdivided using a six-paddock rotation so that the paddocks were grazed for 6 d and rested for 30 d throughout the 121-d trial. Put-and-take animals were used to evaluate stocking rate. One ruminally fistulated cow was used in each of the six pastures to determine composition of grazed forage from reticulorumen evacuation at the beginning and end of grazing in paddock 1 (on d 0, 6, 36, 42, 72, 78, 108 and 114). Both treatments sustained similar stocking rates. Cow gain and body condition score change were not different due to treatments (P>0.10). However, weight gains of calves grazing alfalfa were 11.5% higher (P<0.05) than those of calves grazing tall fescue-red clover. Calf gain per hectare for the alfalfa pastures also tended to be higher (P=0.15) than that for tall fescue-red clover. This was due to the improved calf performance on alfalfa with similar stocking rates. Alfalfa was lower in NDF and ADF (P<0.05), and higher in CP at the beginning of grazing (P<0.05). After grazing, alfalfa was lower in NDF and higher in CP (P<0.05). Both alfalfa and tall fescue-red clover effectively maintained cow performance, whereas the alfalfa resulted in improved calf gain.

Comparison of anthelmintic control programs for sheep in Virginia

Summary Haemonchus contortus is the most serious parasitic problem encountered by sheep producers in southwestern Virginia. Four anthelmintic control programs for grazing lambs were tested. Group TR received monthly sc injections of ivermectin (200 μg/kg of body weight). Group SI received the same dose of ivermectin at 0, 3, 6, 9, and 12 weeks after the start of the grazing season. Group SL was given levamisole (8 mg/kg, po) 0, 3, 6, 9, and 12 weeks after the start of the grazing season, and group TA received ivermectin (200 μg/kg) 0, 8, 16, 20, and 24 weeks after the beginning of grazing. None of the 4 programs provided satisfactory control of parasites as indicated by fecal egg counts and serum pepsinogen concentrations, although group-TR lambs gained significantly more weight than lambs in groups SI and TA. Group-TA lambs developed clinical haemonchosis in early August and required additional treatment at that time. These findings suggest that reliance on anthelmintics alone may not provide the most effective and economic control of parasitic infection.

放牧牛の異常寒波による被害とその対策

At the end of May, 1981, extraordinary cold weather attacked the Soya district, Hokkaido, causing great damage on grazing cattle which had been placed on pasture just before. For the prevention of such damage, the following steps should be taken in future: to increase shelter belt, windbreak, and shed of refuge in the pasture, additional supply of hay, and careful supervision and health management especially at the beginning of grazing. A period of acclimatization should be set up for cattle before the placement on pasture. It should be one month for cattle which have never been on pasture before and 2 weeks for cattle experienced in grazing. A paddock may be used for acclimatization.