The effect of plant structure on the acceptability of different grass species to cattle

The changes in the acceptability to cattle of nine indigenous grass species over the grazing season were related to nine characteristics of the species. Acceptability was positively related to tuft diameter, leaf percentage, leaf table height and leaf crude protein, but was negatively related to stemminess. Species of preferred acceptability were leafy and non‐stemmy, with a high leaf table and had leaves of low tensile strength containing high crude protein. Avoided species were generally stemmy and had leaves containing low crude protein. Acceptability was largely determined by plant structure but was also influenced by leaf crude protein and tensile strength. Plant structure appears to modify acceptability by altering the nutritive value of the plant to the animal through its effect on intake rates. It is suggested that stemminess may increase resistance to herbivory by limiting the degree of tissue loss.     

Researching the plant-animal interface: the investigation of ingestive behavior in grazing animals

Profitable livestock production from forages largely depends on efficiency of converting forages into products. Efficient grazing management systems require an understanding of the roles of system components. However, experimentation should be conducted with regard to the system as a whole rather than on the systems components in isolation. This may necessitate development of computer models. The short-term intake of forage by grazing animals is controlled both by the structure of the forage and by effects of the ingested forage on gut fill as moderated by the hunger-satiety complex. Intake can be defined as the product of bite size, rate of biting and grazing time. Measurement of these variables is facilitated by the use of esophageally fistulated animals and automatic recording devices. Bite size has the greatest influence on intake, with rate of biting and grazing time being compensatory variables. Sward structure influences bite size to varying degrees. In temperate grass swards, leaf surface height appears to be the dominant influence on bite size. But in tropical grass swards, leaf density and leaf:stem ratio have a greater influence on bite size than does leaf surface height. Alternative techniques to conventional grazing trials are described. Diversity of environments and forages in the U.S. requires further research into the development of grazing systems. In the future, small-scale trials and computer simulation techniques likely will be used to a greater extent.     

The horizontal barrier effect of stems on the foraging behaviour of cattle grazing five tropical grasses

The rate of nutrient intake (RNI) is a primary determinant of animal performance in grazing cattle and depends on both diet quality and instantaneous intake rate (IIR). In turn, diet quality and IIR are a function of the foraging behaviour of the animal (selectivity, bite mass and bite rate) and the characteristics of the sward. In this study we evaluated the effect of the stem density and the tensile resistance of stems on the foraging behaviour of cattle grazing tropical pasture species. The methodology involved the use of small sown microswards offered to tethered cattle. The experiment consisted of a factorial combination of five tropical grasses [Bothriochloa pertusa (Bp), Chloris barbata (Cb), Chloris gayana (Cg), Cynodon dactylon (Cd) and Heteropogon contortus (Hc)] and three stem densities (0, 400 and 800 stems m^− 2). Bp and Cd had stems of significantly lower tensile resistance (19 and 15 N respectively) (Group 1) than those of Cb, Cg and Hc (110, 211 and 167 N respectively) (Group 2). The steers avoided stems of Group 2 and thus, reduced bite area, bite mass, IIR and RNI as stem density increased. However, the animals did not avoid stems of Group 1 and there was no effect of stem density on any of the foraging behaviour variables when cattle grazed species in Group 1. These results confirm that RNI and plant part selection is closely associated with the tensile resistance of the stem.     

The scaling of bite force and constriction pressure in kingsnakes (Lampropeltis getula): Proximate determinants and correlated performance

Across the diversity of vertebrates, bite force has been studied and suggested to have important ecological and evolutionary consequences. However, there is a notable lineage of vertebrates that use this performance trait yet are missing from the bite‐force literature: the snakes. Snakes often rely on biting during prey subjugation and handling. Many snakes bite and hold prey while a constriction coil is formed or while venom is being delivered, or both. Others use biting exclusively without employing any additional prey‐handling behaviors. In addition to biting, constriction is an important predation mechanism. Here, I quantify bite force and constriction pressure in kingsnakes (Lampropeltis getula). Furthermore, I explore the proximate determinants of bite force as well as the relationship between biting and constriction performance. Bite force increased linearly with all head and body measures. Of these, head height was the best predictor of bite force. Bite force in kingsnakes was within the range of values reported for lizards, but their relative performance was lower for their head size compared to lizards. Peak constriction pressure also increased with all body measures. Biting and constricting use 2 different parts of the musculoskeletal system and are positively and significantly correlated with one another. Future work targeting a greater diversity of snakes that rely more heavily on biting may reveal a greater range of bite performance in this diverse and successful vertebrate group.     

放牧绵羊行为生态学研究：Ⅳ.放牧绵羊白天主要牧食行为参数间的关系和变化

试验结果表明，在较低放牧率条件下，采食时间、进食速率和采食量相对稳定；采食口数和采食速度随放牧时期的推移而减少，每口采食量有所增大；采食口数、采食速度和每步采食口数均与每口采食量呈负相关；每步采食口数与采食速度呈高度正相关，其回归方程为ｙ∧＝６．１１８１＋４．５５２１ｘ（ｒ２＝０．８１＊＊）；各放牧时期基本上都有３个进食率峰值，且上午进食量只占全天采食量的１／３～１／２，所占比例随放牧时期推移而增大；不同放牧率的研究结果也有类似的关系。     

Changes in the viscoelastic behaviour of the rumenal digesta mat of sheep fed on pasture or chaffed lucerne hay

We examined the changes in the physical properties of the digesta mat over a period of 24 h after cessation of feeding, in sheep that had been maintained on pasture or fed chaffed lucerne hay. The dry matter content of the digesta mat declined at similar rates in both dietary groups, although it was generally higher in sheep fed lucerne. Median particle size declined in the digesta mats of both dietary groups at similar rates in samples taken after 8 h, but median particle size was significantly greater in sheep fed chopped lucerne hay than in those fed grass. Thus, particles were not reduced to a common size suggesting that factors in addition to particle size governed the rate of breakdown of the rumen mat. The relationship between the elastic and loss moduli was of a consistent pattern in all samples taken from the rumen mat indicating that it behaved as a weak gel. The elastic and loss moduli of the digesta mats of sheep that had been fed pasture or chopped lucerne hay converged to similar values after 12 h and declined broadly at similar rates after this. The relationship between these two moduli and the dry matter content of the rumen mat were of similar curvilinear form for sheep on both diets. These findings suggest that the rate of breakdown of the rumen mat is more likely to be governed by its composite behaviour than by the size of the constituent particles.     

Thiamin supplementation and the ingestive behavior of beef cattle grazing endophyte-infected tall fescue

Livestock grazing endophyte (Acremonium coenophialum Morgan-Jones and Gams)-infected tall fescue (Festuca arundinacea Schreb.) perform poorly due to tall fescue toxicosis, especially when animals are under heat stress. In order to determine whether thiamin promotes recovery from tall fescue toxicosis, 1 or 0 g of thiamin per day, as mononitrate, was fed orally to adult Angus (Bos taurus) cows (380 +/- 8 kg) grazing either tall fescue pasture with and without endophyte or alfalfa (Medicago sativa L.). A tethered grazing system employing a split-plot design was used to estimate intake and components of ingestive behavior. No significant differences attributable to thiamin supplements were seen in rates of intake and biting, grazing time and intake per bite when cows grazed endophyte-infected tall fescue during the first 4 d of exposure. When cows grazed endophyte-infected (greater than 95%) tall fescue with 2,091 micrograms/g loline alkaloids after 4 d of exposure, the untreated animals ingested herbage dry matter (DM) at 1.19 kg/h, whereas the cows receiving thiamin ate 1.57 kg/h (P less than .05). Cattle achieved these rates of DM intake by forming bites of 1.0 and 1.2 g DM at 24 and 26 bites/min when treated with 0 and 1 g of thiamin per day, respectively. Thiamin supplements had no effect on ingestive behavior of cows grazing endophyte-free tall fescue or alfalfa after exposure to these forages for 4 d. Responses to thiamin generally were greater when cattle grazing endophyte-infected tall fescue were exposed to heat stress. Oral thiamin supplementation may alleviate tall fescue toxicosis of beef cattle during warm weather.     

Crib‐biting in US horses: Breed predispositions and owner perceptions of aetiology

Reasons for performing study: Crib‐biting is an equine stereotypy that may result in diseases such as colic. Certain breeds and management factors have been associated. Objectives: To determine: breed prevalence of crib‐biting in US horses; the likelihood that one horse learns to crib‐bite from another; and owner perceptions of causal factors. Methods: An initial postal survey queried the number and breed of crib‐biting horses and if a horse began after being exposed to a horse with this habit. In a follow‐up survey, a volunteer subset of owners was asked the number of affected and nonaffected horses of each breed and the extent of conspecific contact. The likelihood of crib‐biting given breed and extent of contact was quantified using odds ratio (OR) and significance of the association was assessed using the Chi‐squared test. Results: Overall prevalence was 4.4%. Thoroughbreds were the breed most affected (13.3%). Approximately half of owners believed environmental factors predominantly cause the condition (54.4%) and crib‐biting is learned by observation (48.8%). However, only 1.0% of horses became affected after being exposed to a crib‐biter. The majority (86%) of horses was turned out in the same pasture with other horses and extent of contact with conspecifics was not statistically related to risk. Conclusion: This is the first study to report breed prevalence for crib‐biting in US horses. Thoroughbreds were the breed more likely to be affected. More owners believed either environmental conditions were a predominant cause or a combination of genetic and environmental factors contributes to the behaviour. Only a small number of horses reportedly began to crib‐bite after being exposed to an affected individual, but approximately half of owners considered it to be a learned behaviour; most owners did not isolate affected horses. Potential relevance: Genetic predisposition, not just intensive management conditions and surroundings, may be a factor in the high crib‐biting prevalence in some breeds, and warrants further investigation. Little evidence exists to suggest horses learn the behaviour from other horses, and isolation may cause unnecessary stress.     

Forage ingestion: effects of sward characteristics and body size

A model of a grazing ruminant in a range environment integrates ingestive behaviors (bite size, chewing rate, movement rate) and processing behaviors (mastication and rumination requirements) with rumen function to predict the combination of behaviors that produces the highest rate of energy digestion per unit of time (DE/T). Ingestive and processing behaviors compensate to maintain DE/T as the environment changes. Compensation for a change in forage density is more complete than for a change in forage quality. Ingestive behaviors alone have limited ability to offset environment changes, and control of passage rate through processing behaviors is an important additional compensatory mechanism. Optimal solutions of the model maintain a high intake by sacrificing diet quality and maintain a high rate of passage by increasing mastication and rumination effort when eating low-quality diets. When the model is scaled to body size, decreases in body size lead to higher selectivity and more pronounced processing behaviors. In no case are optimal solutions characterized by less than maximum rumen fill. The model predicts that the small ruminant derives an increasing proportion of its energy from the cell contents. The model suggests that selection for production has produced plastic ingestive and processing behaviors and has increased body size.     

Grazing behavior and performance of beef cattle as a function of sward structure and herbage quality under rotational and continuous stocking on species‐rich upland pasture

An experiment to reveal functional response and heifers' performance to sward characteristics and forage chemical composition was conducted for 5 years in rotational (RSS) and continuous (CSS) stocking systems on native species‐rich upland grassland. We measured sward characteristics, forage chemical composition, heifers' grazing behavior and live‐weight gains from July to September. Mean sward surface height was lower on CSS than on RSS; grass and forb density, and white clover stolon length, were similar. Herbage on CSS had higher crude protein content and lower crude fiber content than on RSS. No difference existed in time budgets of grazing, ruminating and resting between stocking systems and season, while grazing rates were higher on CSS. Stocking rate was 1671 and 1332 kg per ha on CSS and RSS, individual daily live‐weight gain 683 and 652 g on CSS and RSS. Gain per ha was 20 kg higher on CSS. Results suggested stocking systems on native species‐rich grassland had no effect on activity time budgets or animal performance. Both RSS and CSS allow similar outputs for stocking rates in terms of individual daily live‐weight gain. Key parameters determining heifers' behavior and performance were sward height, grass and forb density in the sward, and content of crude fiber and protein in forage.     

放牧水牛牧食量与胃肠道消化代谢的关系

本实验选用江苏省东台县种畜场9头成年母海仔水牛,于1984年5月至9月在草滩牧场进行了春、秋两期实验。秋季放牧期瘤胃内乙酸/丙酸(A/P)比值和pH值均显著高于春季放牧期;TVFA浓度和可消化干物质采食量也稍高于春季,但差异不显著(P>0.05)。放牧水牛瘤胃中TVFA变化较平稳,与采食量关系不甚明显。春季放牧期采食量和食糜排出速率均显著低于秋季;而表观消化率则显著高于秋季。春季放牧期采食量(Y),表观消化率(X_2)和食糜排出速率(X_1)三项指标两两之间均呈正相关,复回归方程为:Y=-10.48+0.2216X_1+0.1615X_2(r=0.70,P<0.05);秋季放牧期采食量与食糜排出速率呈正相关,但分别与消化率呈负相关,三者的复回归方程为:Y=-4.66+0.5239X_1+0.4662X_2(r=0.88,P<0.01)。本实验中放牧水牛的采食行为虽然受到选择性牧食、草生状态和放牧距离等外界因素的影响,但牧食量受食糜排出率和表观消化率的共同调节。     

标准回肠可消化氨基酸模式下降低饲粮粗蛋白质水平对蛋鸡生产性能、蛋品质及氮平衡的影响

本试验旨在研究标准回肠可消化(SID)氨基酸(AA)模式下,降低饲粮粗蛋白质(CP)水平对海兰灰蛋鸡生产性能、蛋品质及氮平衡的影响。选取540只20周龄体重相近且健康的海兰灰蛋鸡,随机分为5个处理,每个处理6个重复,每个重复18只鸡,预试期1周,正试期12周,采食等代谢能(11.82 MJ/kg)、等赖氨酸(Lys,SID Lys为0.831%)、相同AA模式、不同CP水平(18.0%、17.5%、17.0%、16.5%和16.0%)的试验饲粮。结果表明:SID AA模式下,降低饲粮CP水平可极显著降低平均蛋重和CP摄入量(P<0.01),显著降低鸡蛋浓蛋白高度(P<0.05),显著降低蛋鸡摄入氮和排出氮(P<0.05),有提高氮表观利用率的趋势(P=0.05);数据偏相关分析表明,饲粮中SID AA模式外的精氨酸、苯丙氨酸和亮氨酸水平下降与平均蛋重下降显著相关(P<0.05),与浓蛋白高度下降无显著相关(P>0.05)。结果提示,SID AA模式下,降低饲粮CP水平,除影响平均蛋重和浓蛋白高度外,对其他生产性能、蛋品质及血液生化指标影响较小,平均蛋重的下降与低CP饲粮中精氨酸、苯丙氨酸和亮氨酸不足有关;AA平衡的低CP饲粮,可在维持较高生产性能的同时减轻蛋鸡粪氮排出。     

桑科草原不同草地利用方式土壤呼吸的动态研究

为探寻更加合理的草地利用方式,以甘肃省夏河县桑科乡高寒草原为研究区,分别设置放牧草地,放牧+施肥草地,放牧+划破补播草地、封育草地、人工草地处理,测定不同草地利用方式土壤呼吸的动态变化。结果表明:(1)土壤呼吸速率大小顺序为放牧+施肥人工封育放牧+划破补播放牧,最大值10.41μmol/(m2·s),最小值4.69μmol/(m2·s),日变化和季节变化均呈单峰曲线,日变化峰值出现在13∶00~14∶00,7月各处理土壤呼吸速率达最大。(2)土壤呼吸温度敏感性Q10值为放牧+施肥放牧人工放牧+划破补播封育,最大值1.826,最小值1.157。(3)土壤呼吸与土壤湿度的非线性相关关系P值大小为放牧+划破补播放牧人工封育放牧+施肥。放牧+施肥处理为最优草地利用方式。     

Ingestive behavior of supplemented Nellore heifers grazing palisadegrass pastures managed with different sward heights

Three sward heights (15, 25 and 35 cm) and three supplement types (energy, energy‐protein, and a mineral mix supplement) were evaluated in a 3 × 3 factorial arrangement distributed in a completely randomized design to study changes in forage search patterns in Nellore heifers in a continuous grazing system. Pasture data were collected using two replicates (paddocks) per treatment over four periods during the rainy season. The behavior assessments were made in the first and fourth grazing seasons. It was hypothesized that supplements and pasture management would modify ingestive behavior, considering that animals would require less time grazing if they had energy requirements met through higher digestibility of better managed paddocks, or use of supplements high in energy. Total and green forage masses along with green : dead material ratio were greater in treatments managed with higher sward heights. Sward managed with 35 cm height resulted in lower leaf : stem ratio compared with 15 cm sward height treatments. The animals on the 15 cm pastures spent more time grazing overall and during each meal, but there were no differences observed in meal numbers in comparison to 35 cm treatments. Heifers fed protein and/or energy supplements spent less time grazing in the early afternoon, but overall grazing time was the same for all animals.     

Patterns of selection of Acacia karroo by goats and changes in tannin levels and in vitro digestibility following defoliation

Patterns of browse selection by Boer goats in a representative Acacia karroo community in the eastern Cape were studied. The rate of intake of browse was positively related to the leaf mass per unit length of the shoot. The ease of harvesting leaf material, as determined by the height off the ground, modified the rate of intake. Generally, following browsing, tannin levels increased significantly and in vitro digestibility decreased significantly. These changes in tannin content and digestibility differed in magnitude according to the plant size and age of the shoot and leaf. Generally, the leaf and shoot intake was negatively related to tannin content and positively related to digestibility, thus influencing patterns of selection for different plant parts and size classes of A. karroo. However, some of the results are contradictory.     

Influences of protein ingestion on glucagon‐like peptide (GLP)‐1‐immunoreactive endocrine cells in the chicken ileum

Influences of a specific dietary nutrient on glucagon‐like peptide (GLP)‐1‐containing cells in the chicken intestine are not yet clear. Significance of dietary protein level on GLP‐1‐containing cells in the chicken ileum was investigated. Chickens fed control or experimental diets of varying protein levels were examined using immunohistochemical and morphometrical techniques. We show that the protein ingestion had an impact on the activities of GLP‐1‐immunoreactive cells in the chicken ileum. Weight gains declined with decreasing dietary crude protein (CP) levels, but no significant differences were detected in the daily feed intake and villous height. GLP‐1‐immunoreactive cells with a round or oval shape were frequently observed in the lower CP level groups (4.5% and 0%). Frequencies of occurrence of GLP‐1‐immunoreactive cells were 41.1 ± 4.1, 38.5 ± 4, 34.8 ± 3.1 and 34.3 ± 3.7 (cells/mm², mean ± SD) for dietary CP level of 18%, 9%, 4.5% and 0% groups, respectively and significant differences were recognized between the control and lower CP level groups (P < 0.05). Multiple regression analysis indicated a significant correlation between the daily protein intake and frequencies of occurrence of GLP‐1‐immunoreactive cells. The protein ingestion is one of the signals that influence GLP‐1‐containing cells in the chicken small intestine.     

不同载牧量对苜蓿放牧地植被的影响

研究于１９９２年在甘肃河西半荒漠地区杂花苜蓿型人工草地进行，试验采用单因子设计，衣载牧量分轻牧、中牧、重牧３个处理６个重分区轮牧。结果表明，试验当年，草地类型未发生演变，披碱草随放牧加强而衰退，无芒雀麦和红豆草在中牧下得到促进，紫羊茅在重牧下受抑。由牧草产量和质量的分析表明，在西北干旱地区，苜蓿型草地可于６月初刈草后，连续放牧３次，且载牧量以中等为宜。     

Nutrient sufficiency in beef cows grazing on a dwarf bamboo‐dominated forestland pasture in Japan

The nutritional status of cows grazing on a 120‐ha public alpine forestland pasture dominated by the dwarf bamboo Sasa senanensis located in central Japan was evaluated over the course of 2 years. Data were collected during grazing seasons in three periods: early (June), mid‐ (August) and late (late September–early October) periods. During these periods, the number of experimental Japanese Black cows varied between three and six. With the exception of the dry matter (DM) intake in 2005 and the crude protein (CP) digestibility in 2006, the DM and CP intake and digestibility were lower in the mid‐ and late periods than in the early period for both years (P < 0.05). Metabolizable energy intake was slightly insufficient for the requirement of the cows in the late period of 2005; in the mid‐ and late periods of 2006, the metabolizable energy intake was 0.4 to 0.5 times the requirement. These results suggest that the energy intake of cows grazing on forestland pasture dominated by S. senanensis would not satisfy their requirements starting in the mid‐period (August) grazing, even though the pasture had abundant herbage resources during these periods.     

Stocking Rate and Riparian Vegetation Effects on Physical Characteristics of Riparian Zones of Midwestern Pastures

Grazing at high stocking rates may increase sediment and nutrient loading of pasture streams through transport in precipitation runoff and bank erosion. A 3-yr (2007–2009) grazing study was conducted on 13 cool-season grass pastures to quantify effects of stocking rate and botanical composition on forage sward height, proportions of bare and manure-covered ground, and bank erosion adjacent to streams. Pastures ranged from 2 ha to 107 ha with stream reaches of 306 m to 1 778 m that drained watersheds of 253 ha to 5 660 ha. Bare and manure-covered ground were measured at a 15.2-m distance perpendicular to the stream at 30.5-m intervals at up to 30 locations on each side of the stream by the line transect method in May, July, September, and November of each year. At the midpoint of the 15.2-m line, forage sward height was measured with a falling plate meter (4.8 kg · m^-2) and plant species identified. In November 2006, fiberglass pins (1.6 × 76.2 cm) were driven 73.7 cm into the stream bank at 1-m intervals from the streambed to the top of the bank along 10 equidistant transect locations on each side of the stream to measure bank erosion during spring, summer, and fall of each year. Increasing pasture stocking rates increased manure-covered ground and decreased sward height, but did not affect proportions of bare ground. The greatest, intermediate, and least net soil erosion rates occurred during the winter/early spring, late spring/early summer, and late summer/fall seasons. Stocking rates between measurements, expressed as cow-days · m^-1 stream, were not related to bank erosion. Increasing stocking rates per unit of stream length will increase manure cover and decrease forage sward height, but not affect proportions of bare ground or bank erosion rates adjacent to pasture streams. Therefore, managing stocking rates may reduce nutrient loading of pasture streams.     

补播和划破草皮对退化亚高山草甸植被恢复的影响

在甘肃省甘南州临潭县研究围栏内补播和划破草皮对退化亚高山草甸植被的高度、总盖度、地上生物量和功能群物种多样性总指数的影响。结果表明,在各划破草皮处理中,牧草总盖度、地上生物量和功能群物种多样性总指数随着补播量的增加而增加,植被高度随着补播量的增加呈先增加后降低的趋势。补播和划破草皮有显著互作效果,补播量3[垂穗披碱草(Elymus nutans)播量为49.1 kg·hm-2,老芒麦(Elymus sibiricus) 播量为67.5 kg·hm-2,紫花苜蓿甘农1号(Medicago sativa cv.Gannong No.1)播量为23.3 kg·hm-2]和划破草皮组合的牧草地上生物量(201.5 g·m-2)、总盖度(88.2%)和功能群物种多样性总指数(1.203)达到最大值,补播量1（垂穗披碱草播量为26.7 kg·hm-2,老芒麦播量为37.5 kg·hm-2,紫花苜蓿甘农1号为0）和划破草皮组合的植被高度(11.7 cm)达到最大值。就各补播水平平均值而言,划破草皮植被高度、总盖度、地上生物量和功能群物种多样性总指数显著高于未划破草皮。综合考虑高度、总盖度、地上生物量和功能群物种多样性总指数,经关联度分析可知,补播量2（垂穗披碱草播量为37.5 kg·hm-2,老芒麦播量为52.5 kg·hm-2,紫花苜蓿甘农1号18.3 kg·hm-2）和划破草皮为最优组合。