Degradability characteristics of dry matter and crude protein of forages in ruminants

Twelve corn silages, 22 grass silages and 14 grass hays, obtained from various farms located in the lower Fraser Valley region of British Columbia, and 16 alfalfa hays, grown primarily in the Columbia basin of central Washington State, were evaluated using both the rumen and the mobile nylon bag in situ techniques. Nylon bags containing each forage were incubated in duplicate for 0, 2, 4, 8, 12, 24, 48, 72, or 96 h in two of six non-lactating Holstein cows fitted with rumen and duodenal cannulae. All forage types were evaluated in terms of the following dry matter (DM) and crude protein (CP) digestion characteristics: soluble fraction A, degradable fraction B, degradation rate, lag phase, and effective degradability. The mobile nylon bag technique was used to determine intestinal disappearance of DM and CP from the forages following pre-incubation in the rumen for 12 h. Significant (P < 0.05) differences in degradation characteristics occurred within all forages with regard to the soluble and potentially degradable DM and CP fractions. Soluble CP content in the rumen varied from 44.08 to 75.37% and from 18.74 to 65.38% in the corn and grass silages, respectively, and from 48.27 to 75.43% and from 30.13 to 65.95% in the alfalfa and grass hays, respectively. Significant differences within each forage type were also observed for the degradable CP in fraction B: 10.89 to 45.28% for corn silage, 20.72 to 82.77% for grass silage, 16.67 to 44.88% for grass hay and 25.44 to 62.93% for alfalfa hays. Significant differences (P > 0.05) were observed in fractional rates of ruminal DM degradation of the grass hays and corn silages. Significant differences did exist in the fractional rates of ruminal CP degradation within all forage types with the exception of alfalfa hays. Effective degradabilities of DM and CP were also significantly different between samples of a particular forage type. The mobile nylon bag data indicated that approximately 20% of the original CP in the grass silage, grass hay and alfalfa hay samples disappeared in the intestine and that there was significant variation between individual samples. On average, in the corn silage samples more than 10% of the original nitrogenous material disappeared in the intestine. The results presented in this study clearly demonstrate that the use of tabulated values for describing individual batches of forages in terms of their degradability characteristics is inaccurate since they may not reflect the particular forage being used in the ration and thus may lead to errors in diet formulation.     

Rumen Fungi and Forage Fiber Degradation

The role of anaerobic rumen fungi in in vitro forage fiber degradation was determined in a two forage × two inoculum source × five treatment factorial design. Forages used as substrates for rumen microorganisms were Coastal bermuda grass and alfalfa; inoculum sources were rumen fluid samples from a steer fed Coastal bermuda grass hay or alfalfa hay; treatments were whole rumen fluid (WRF), WRF plus streptomycin (0.2 mg/ml of rumen fluid) and penicillin (1.25 mg/ml of fluid), WRF plus cycloheximide (0.5 mg/ml of fluid), WRF plus streptomycin, penicillin, and cycloheximide, and McDougall buffer. Populations of fungi as shown by sporangial development were greater on bermuda grass leaves than on alfalfa leaflets regardless of inoculum source. However, endogenous fungal populations were greater from the alfalfa hay inoculum. Cycloheximide inhibited the fungi, whereas streptomycin and penicillin, which inhibit bacterial populations, resulted in an increase in numbers of sporangia in the alfalfa inoculum, suggesting an interaction between bacteria and fungi. Bacteria (i.e., WRF plus cycloheximide) were equal to the total population in degrading dry matter, neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and cellulose for both inocula and both forages. Degradation of dry matter, NDF, ADF, and cellulose by anaerobic fungi (i.e., WRF plus streptomycin and penicillin) was less than that due to the total population or bacteria alone. However, NDF, ADF, and cellulose digestion was 1.3, 2.4, and 7.9 percentage units higher, respectively, for bermuda grass substrate with the alfalfa versus bermuda grass inoculum, suggesting a slight benefit by rumen fungi. No substantial loss of lignin (72% H₂SO₄ method) occurred due to fungal degradation. The most active fiber-digesting population in the rumen was the bacteria, even when streptomycin and penicillin treatment resulted in an increase in rumen fungi over untreated WRF. The development of large numbers of sporangia on fiber may not indicate a substantial role as digesters of forage.     

Nutritional Value of Moss for Arctic Ruminants: a Test with Muskoxen

Abstract: Although moss is commonly found in the feces of arctic herbivores, we do not know the digestible value of this forage for ruminants. We compared grass hay (Bromus sp.) with moss (Hylocomium splendens, Tomenthypnum nitens) from 2 locations in Alaska, USA: Cape Krusenstern National Monument and Fairbanks. We evaluated forages by digestion in ruminally fistulated muskoxen (Ovibos moschatus) by suspending forages in polyester bags before and after the rumen was acclimated with moss for 15 consecutive days. Ruminal degradation was not affected by acclimation to moss. Hay lost dry matter during 48 hours of ruminal incubation (-49%), whereas moss gained dry matter (+44-57%). Incubated moss gained nitrogen (+435-680%), as well as fiber (+18%), and one moss gained ash (+121%). Mass gained by moss in the rumen was probably due to the combined effect of microbial colonization and adsorption of fibrous particles onto the sponge-like matrix. We evaluated postruminal degradation of forages by incubation in acid-pepsin. Ruminally incubated mosses lost little nitrogen in acid-pepsin even though ruminally incubated hay lost 23% nitrogen on acid digestion. Consumption of moss during winter may be a net cost of selecting plants within moss communities when lichens and graminoids are scarce. Moss in feces may, therefore, indicate low availability of favored foods for muskoxen and other arctic ruminants that are confined to small winter ranges. Increasing concentrations of moss in the feces and, thus, the diet of muskoxen may alert wildlife managers to shifts in winter range quality or forage access due to changing snow conditions.     

Foraging decisions in a capital breeder: trade-offs between mass gain and lactation

The high energetic costs of lactation can lead to fundamental trade-offs in life-history traits, particularly in young females that reproduce before completing body growth. We assessed whether lactating female mountain goats (Oreamnos americanus) used behavioural tactics at fine spatio-temporal scales to increase energy intake to compensate for the costs of lactation. Lactating females increased bite rate and chewing rate compared with non-lactating females, but selected similar foraging sites in terms of plant quality and abundance. At peak lactation, forage intake of lactating females was >40% greater than that of non-lactating females. For females that had reached asymptotic body mass (i.e. ≥6 years old), summer mass gain of lactating females was similar to that of non-lactating females. At 4 and 5 years of age, however, daily mass gain of lactating females was about 20% lower than that of non-lactating females. We conclude that increased foraging may allow fully-grown lactating females to compensate for the energetic costs of lactation, but that there is a major trade-off between mass gain and lactation for younger females. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Self-grooming induced by sexual chemical signals in male root voles (Microtus oeconomus Pallas)

Sniffing is one-way animals collect chemical signals, and many males self-groom when they encounter the odor of opposite-sex conspecifics. We tested the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles (Microtus oeconomus Pallas). Specifically, we investigated the sniffing pattern of male root voles in response to odors from the head, trunk, and tail areas of lactating and non-lactating females. The self-grooming behavior of males in response to female individual odorant stimuli was documented, and the relationship between self-grooming and sniffing of odors from the head, trunk, and tails areas were analyzed. Sniffing pattern results showed that males are most interested in odors from the head area, and more interested in odors from the tail as compared to the trunk area. Males displayed different sniffing and self-grooming behaviors when they were exposed to odors from lactating females as compared to non-lactating females. Males also spent more time sniffing and engaged in more sniffing behaviors in response to odors from the lactating females’ tail area as compared to the same odors from non-lactating females. Similarly, males spent more time self-grooming and engaged in more self-grooming behaviors in the presence of individual odors from lactating females as compared to individual odors from non-lactating females. Partial correlation analyses revealed that the frequency of self-grooming was significantly correlated with the frequency of tail area sniffs. Results from this experiment suggest that sexual attractiveness of lactating females is stronger than that of non-lactating females. Furthermore, the partial correlation analysis demonstrated that self-grooming in males is induced by odors from the tail area of females. Collectively, these results support the hypothesis that sexual chemical signals from females can induce self-grooming behavior in male root voles. Self-grooming may also reflect the groomer's sexual motivation and facilitate sexual interactions.     

Sexual segregation in ungulates: a comparative test of three hypotheses

In most social ungulate species, males are larger than females and the sexes live in separate groups outside the breeding season. It is important for our understanding of the evolution of sociality to find out why sexual segregation is so widespread not only in ungulates but also in other mammals. Sexual body size dimorphism was proposed as a central factor in the evolution of sexual segregation in ungulates. We tested three hypotheses put forward to explain sexual segregation: the predation-risk, the forage-selection, and the activity budget hypothesis. We included in our analyses ungulate species ranging from non-dimorphic to extremely dimorphic in body size. We observed oryx, zebra, bighorn sheep and ibex in the field and relied on literature data for 31 additional species. The predation-risk hypothesis predicts that females will use relatively predator-safe habitats, while males are predicted to use habitats with higher predation risk but better food quality. Out of 24 studies on different species of ungulates, females and their offspring chose poorer quality but safer habitat in only eight cases. The forage-selection hypothesis predicts that females would select habitat based on food quality, while males should prefer high forage biomass. In fact, females selected higher quality food in only six out of 18 studies where males and females segregated, in eight studies there was no difference in forage quality and in four studies males were in better quality habitat. The activity budget hypothesis predicts that with increasing dimorphism in body size males and females will increasingly differ in the time spent in different activities. Differences in activity budgets would make it difficult for males and females to stay in mixed-sex groups due to increased costs of synchrony to maintain group cohesion. The predictions of the activity budget hypothesis were confirmed in most cases (22 out of 23 studies). The heavier males were compared to females, the more time females spent foraging compared to males. The bigger the dimorphism in body mass, the more males spent time walking compared to females. Lactating females spent more time foraging than did non-lactating females or males. Whether species were mainly bulk or intermediate feeders did not affect sexual differences in time spent foraging. We conclude that sexual differences in activity budgets are most likely driving sexual segregation and that sexual differences in predation risk or forage selection are additive factors.     

Habitat choice of Grevy's zebras (Equus grevyi) in Laikipia, Kenya

Characterizing habitat choice is essential for endangered species conservation. For the endangered Grevy's zebra ( Equus grevyi ), as with many widely ranging vertebrates, human activities may be an important factor affecting space use. Grevy's zebras are grazing ungulates inhabiting the savannahs of central-northern Kenya and Ethiopia. Past research on their social organization indicates that reproductive status shapes associations and movements. Here, we examine how habitat use varies across four reproductive classes: lactating and nonlactating females, bachelors and territorial males. We also test whether Grevy's zebra avoid locations close to active livestock corrals, or bomas . We find that forage quality, forage quantity and habitat openness of locations used by Grevy's zebra vary significantly depending on individual reproductive state. Lactating females and bachelors use areas with green, short grass and medium-dense bush more frequently than nonlactating females or territorial males. We hypothesize that lactating females trade off forage quantity and safety to access nutrients in growing grass. Across reproductive classes, Grevy's zebra choose locations further from active bomas than if they used the area randomly. Our results suggest that Grevy's zebra may require a range of vegetation characteristics for different reproductive classes. Further, they may need areas free from competition or disturbance by livestock.     

Harvesting, rumination, digestion, and passage of fruit and leaf diets by a small ruminant, the blue duiker

Because small ruminants (<15 kg) have a high ratio of metabolic rate to fermentation capacity, they are expected to select and require low-fiber, nutrient-dense concentrate diets. However, recent studies suggest that small ruminants may not be as limited in their digestive capacity as previously thought. In this study, we examined harvesting, rumination, digestion, and passage of three diets (domestic figs Ficus carica, fresh alfalfa Medicago sativa, and Pacific willow leaves Salix lasiandra) ranging from 10 to 50% neutral detergent fiber content (NDF) in captive blue duikers (Cephalophus monticola, 4 kg). Harvesting and rumination rates were obtained by observing and videotaping animals on each diet, and digestibility and intake were determined by conducting total collection digestion trials. We estimated mean retention time of liquid and particulate digesta by administering Co-EDTA and forages labelled with YbNO₃ in a pulse dose and monitoring fecal output over 4 days. Duikers harvested and ruminated the fig diet faster than the alfalfa and willow diets. Likewise, they achieved higher dry matter, energy, NDF, and protein digestibility when eating figs, yet achieved a higher daily digestible energy intake on the fresh willow and alfalfa than on the figs by eating proportionately more of these forages. Duikers maintained a positive nitrogen balance on all diets, including figs, which contained only 6.3% crude protein. Mean retention time of cell wall in the duikers’ digestive tract declined with increasing NDF and cellulose content of the diet. Digestibility coefficients and mean retention times of these small ruminants were virtually equivalent to those measured for ruminants two orders of magnitude larger, suggesting that they are well adapted for a mixed diet. Received: 10 August 1999 / Accepted: 16 November 1999     

Nitrogen metabolism and kidney function in the Nubian ibex (Capra ibex nubiana)

The nitrogen economy of the Nubian ibex (Capra ibex nubiana), a ruminant that inhabits harsh deserts, was studied in the laboratory when fed three diets of different quality. Even on the low quality roughage (wheat straw) the ibex was found capable of balancing its nitrogen economy. On feeds low in protein, recycling of urea played a major role in helping the ibex maintaining a balanced nitrogen metabolism. When on wheat straw, the ibex recycled 71.6% of the urea synthesized in its liver. When on feeds lower in protein, blood urea concentration dropped (from 11.4 mM when on alfalfa hay to 3.2 mM when on wheat straw). GFR that amounted to 44.28 ml/min when on alfalfa hay decreased to 28.97 ml/min when on wheat straw. Reabsorption of urea amounted to 48% of the urea filtered when on alfalfa hay and increased to 78.8% on wheat straw.     

The integrated processing response of voles to fibre content of natural diets

1. Two species of voles were fed high fibre (barnyard grass) and low fibre (alfalfa) diets to test the integrated processing response (IPR) hypothesis. This hypothesis states that many herbivores are able to maintain their required intake of digestible nutrients and energy on diets with very different fibre content because of compensatory changes in intake of food, size of gastro-intestinal (GI) tract, passage rates of fibre and absorptive capacity of the GI tract.
2. As predicted by the IPR hypothesis, each species of vole maintained a similar intake of digestible dry matter on the two different diets. Both species also had greater intake, larger GI size, shorter mean retention times and greater GI mass (an indicator of epithelial mass and absorptive capacity) when fed grass than when fed alfalfa.
3. The two species differed in that meadow voles, the more active species, had greater total intake and obtained a greater amount of digestible dry matter from either diet than did prairie voles. Meadow voles also consume more grass in the field than do prairie voles, and they digested grass better than did prairie voles. Prairie voles, which consume more dicots in the field, digested alfalfa better than did meadow voles.
4. Meadow voles had longer GI tracts, particularly small intestines, than did prairie voles, which may be linked to their greater ability to digest grass. However, meadow voles did not have larger caeca than prairie voles, even though caecal size increased on grass diets for both species. The GI size of prairie voles fed grass increased more than did the GI size of meadow voles, and this may have enabled prairie voles to utilize a grass diet, though they prefer to eat dicots. Greater selection of leaves, which have less fibre than stems, and longer mean retention times of food may account for better digestion of alfalfa by prairie voles.     

In vivo and in situ measurements of the digestive characteristics of sainfoin in comparison with lucerne fed to sheep as fresh forages at two growth stages and as hay

In vivo and in situ digestive characteristics of sainfoin (Onobrychis viciifolia L., a tannin-rich forage) and lucerne (Medicago sativa L., a tannin-free forage) were compared to evaluate the effects of condensed tannins (CT) and growth stage (vegetative v. early flowering) in experiment 1. In experiment 2, the hays of the two forages, harvested at early flowering, were compared. Ingestibility, organic matter digestibility (OMD) and nitrogen (N) retention were measured in sheep fed sainfoin and lucerne fresh forages and hays. The loss of dry matter (DM) and N from polyester bags suspended in the rumen, abomasum and small intestine was also measured using rumen fistulated sheep and other intestine fistulated sheep. Nitrogen content was lower in sainfoin than in lucerne. Content of CT in sainfoin decreased with growth stage (3.5 to 2.5 g CT/kg DM) and was lower for sainfoin hay (0.6 g CT/kg DM). Ingestibility and OMD did not differ between fresh-fed forage species. Total N tract digestibility in vivo was much lower for sainfoin than for lucerne fresh forages (mean value 0.540 v. 0.721, P < 0.001) and for sainfoin hay than lucerne hay (0.464 v. 0.683, P < 0.001). In both species, N digestibility was not altered by growth stage. The rumen degradation of N was lower in sainfoin than in lucerne, resulting in a lower proportion of N intake excreted in urine. The intestinal digestibility of sainfoin was also lower than that of lucerne, resulting in a higher N excretion in faeces. Hence the efficiency of N utilisation by sheep (ENr) was similar (mean value 0.205 and 0.199 g N retained/g N intake for fresh sainfoin and lucerne, respectively). The coefficient of N retention by the animal was higher for sainfoin at the vegetative stage than for all the other forages. Nitrogen degradability in the rumen determined by the nylon bag technique (DegN) was lower for sainfoin than for lucerne when forages were studied both fresh (mean value 0.608 and 0.818, respectively) and as hays (0.631 and 0.767). The efficiency of forage N digestion (ENd) was higher for sainfoin at the vegetative stage. Compared with lucerne, sainfoin greatly increased the in situ estimate of forage N escaping the rumen but decreased its intestinal digestibility.     

Use of principal component analysis to classify forages and predict their calculated energy content

A set of 180 forages (47 alfalfa hays, 26 grass hays, 52 corn silages, 35 small grain silages and 20 sorghum silages) were randomly collected from different locations of the Po Valley (Northern Italy) from 2009 to 2010. The forages were characterised for chemical composition (11 parameters), NDF digestibility (five parameters) and net energy for lactation (NE_L). The latter was calculated according to the two approaches adopted by the 2001 Nutrient Research Council and based on chemical parameters either alone (NE_L3x-Lig) or in combination with 48 h NDF degradability in the rumen (NE_L3x-48h). Thereafter, a principal component analysis (PCA) was used to define forage populations and limit the number of variables to those useful for obtaining a rapid forage quality evaluation on the basis of the calculated NE_L content of forages. The PCA identified three forage populations: corn silage, alfalfa hay and a generic population of so-called ‘grasses’, consisting of grass hays, small grain and sorghum silages. This differentiation was also confirmed by a cluster analysis. The first three principal components (PC) together explained 79.9% of the total variation. PC1 was mainly associated with protein fractions, ether extract and lignin, PC2 with ash, starch, NDF and indigestible NDF (iNDF) and PC3 with NDF digestibility. Moreover, PC2 was highly correlated to both NE_L3x-Lig (r = −0.84) and NE_L3x-48h (r = −0.94). Subsequently, forage-based scores (FS) were calculated by multiplying the original standardised variables of ash, starch, NDF and iNDF with the scoring factors obtained from PCA (0.112, −0.141, 0.227 and 0.170, respectively). The FS showed a high determination coefficient for both NE_L3x-Lig (R² = 0.86) and NE_L3x-48h (R² = 0.73). These results indicate that PCA enables the distinction of different forage classes and appropriate prediction of the energy value on the basis of a reduced number of parameters. With respect to the rumen in situ parameters, iNDF was found to be more powerful at discriminating forage quality compared with NDF digestibility at different rumen incubation times or rates of NDF digestion.     

The effects of sulphur supplementation on cellulose digestion in vitro and on nutrient digestion,nitrogen metabolism and rumen characteristics of lambs fed on good quality fescue and tropical star grass hays

Experiments were conducted in vitro and in vivo to determine the effects of sulphur (S) supplementation of a good quality fescue hay containing 0.27% total S and a tropical star grass hay containing 0.20% total S. Addition of S was on an isosulphurous basis of either sodium sulphate or D,L-methionine. Cellulose digestion in vitro was improved (P < 0.001) by the addition of 1% urea. Supplementation of forage with 0.05, 0.10 or 0.15% S from either sodium sulphate or methionine also stimulated cellulose digestion in vitro. There were no differences between S sources. The addition of 0.4 or 0.8% nitrate-nitrogen (nitrate-N) (potassium nitrate) depressed (P < 0.05) cellulose digestion in vitro of both hays. No effect of animal adaptation to nitrate was evident. Addition of S partially counteracted the depression in cellulose digestion due to nitrate. Trials were conducted in vivo in which 12 crossbred wether lambs (fescue experiment) or 12 crossbred intact male lambs (star grass experiment) were randomly assigned to one of three treatments: control (forage with no addition of S); forage plus 0.15% S as sodium sulphate; and forage plus 0.15% S as D,L-methionine. Lambs were housed in metabolism crates and each experiment was replicated twice. Dry matter intakes were highest for methionine-supplemented fescue and for S-supplemented star grass, regardless of S source. Dry matter digestibility tended to increase with S addition (fescue experiment) and was significantly higher for S-supplemented star grass. There was a significant increase (P < 0.05) in neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility due to supplemental S, regardless of S source. Nitrogen retention, ammonia-N and ruminal volatile fatty acids were unaffected by S supplementation.     

To Feed or Not to Feed? Testing Different Hypotheses on Rut‐Induced Hypophagia in a Mountain Ungulate

In many ruminant species, males dramatically reduce forage intake during the rut. To date, different hypotheses have been suggested to explain this rut‐induced hypophagia. To assess the predictions of the main hypotheses, we analysed Alpine ibex (Capra ibex) activity budget and compared the behaviour of males and females before, during, and after the rut. Only males spent significantly less time foraging during the rut than outside of it, whereas females allocated a similar proportion of time to foraging before, during, and after the rut. Our results showed that during the rut males also reduced lying time, while the ratio of time spent feeding to time spent lying did not change for males among periods. In conclusion, during the breeding season males maximized energy intake when not actively engaged in mating activities and rut‐induced hypophagia appeared to result from time budget constraints generated by mating‐related activities. Accordingly, the foraging constraint hypothesis seems appropriate to explain this phenomenon in Alpine ibex males.     

Weights and hematology of wild black bears during hibernation.

We compared weights and hematological profiles of adult (greater than 3-yr-old) female black bears (Ursus americanus) during hibernation (after 8 January). We handled 28 bears one to four times (total of 47) over 4 yr of varying mast and berry production. Mean weight of lactating bears was greater (P less than 0.0001) than that of non-lactating females. White blood cells (P less than 0.05) and mean corpuscular volume (P = 0.005) also differed between lactating and non-lactating bears. Hemoglobin (P = 0.006) and mean corpuscular hemoglobin concentration (P = 0.02) varied among years; values were lowest during 1975, following decreased precipitation and the occurrence of a second year of mast and berry crop shortages in a three-year period. Significant (P less than 0.05) interaction between reproductive status (lactating versus non-lactating) and study year for hemoglobin, red blood cells, and packed cell volume, and increased mean corpuscular volume, suggested a greater nutritional challenge for lactating females compared to non-lactating females during the 1975 denning season. Our data suggest that hematological characteristics of denning bears may be more sensitive than weights as indicators of annual changes in nutritional status; however, other influential factors, in addition to mast and berry crop production, remain to be examined.     

The digestibility and nutritive value for dairy heifers of rations containing cellulose fibre

Cellulose residue (cellufiber) from an ammonium base acid sulphite paper process was accepted by dairy heifers to the extent of 40% of the dry matter of an all-roughage ration when mixed with maize (Zea mays) silage at time of feeding. No adverse physiological effects were observed during digestion trials lasting 80 days in which cattle were given successively diets containing 10, 20, 30 or 40% of the ration dry matter as cellufiber. Apparent digestibility of crude protein decreased and digestibility of crude fibre and acid detergent fibre increased as the cellufiber level in the ration increased. Digestibility coefficients of dry matter, nitrogen-free extract and gross energy were unaffected.Uniformity of values for total digestible nutrients, digestible energy and metabolizable energy and, also, of the body weight gains by the test animals indicated only small differences in nutritive value between rations. However, estimated nutritive values of ration components indicated appreciable differences. The TDN of cellufiber was 56% which was approximately equal to that of alfalfa (Medicago sativa) hay and was 82% of the value of maize silage. However, the digestible energy value of cellufiber (1.93 Mcal/kg DM) was only 77% of alfalfa hay and 69% of maize silage. Similarly, its metabolizable energe value of 1.41 Mcal/kg DM was 69% of that of alfalfa hay and 61% of that of maize silage.     

不同年龄雄性北山羊发情期时间分配特征

前人研究表明,可多次繁殖的反刍物种其雄性个体在发情期采食时间显著减少。目前有两个假说解释这一现象,即能量摄入最大化假说和能量保存假说。为验证雄性北山羊在不同发情阶段所采取的能量保存策略,作者于2014年10-12月在新疆天山中部采用焦点动物取样法采集数据,采用Kruskal-Wallis检验和Spearman秩相关性检验分析数据。研究发现雄性北山羊成体和亚成体发情期采食时间均显著低于发情前期和发情后期,但二者在不同发情阶段卧息时间无显著变化,发情期采食和卧息时间比亦显著降低。发情期发情行为时间显著高于发情前期和发情后期,非发情时间主要用于采食。发情期采食时间和卧息时间都与发情行为时间呈显著的负相关关系。雌性北山羊发情期采食时间亦显著低于发情前期和发情后期,发情期和发情后期卧息时间显著高于发情前期。本研究结果表明,发情期不同年龄阶段雄羊都主要采取能量摄入最大化策略,但同时也具有部分能量保存策略的特征。     

Effects of species-diverse high-alpine forage on in vitro ruminal fermentation when used as donor cow's feed or directly incubated

Alpine forages are assumed to have specific effects on ruminal digestion when fed to cattle. These effects were investigated in an experiment from two perspectives, either by using such forages as a substrate for incubation or as feed for a rumen fluid donor cow. In total, six 24-h in vitro batch culture runs were performed. Rumen fluid was collected from a non-lactating donor cow after having grazed pastures at ∼2000 m above sea level for 2, 6 and 10 weeks. These ‘alpine runs’ were compared with three lowland samplings from before and 2 and 6 weeks after the alpine grazing where a silage–concentrate mix was fed. In each run, nine replicates of four forages each were incubated. These forages differed in type and origin (alpine hay, lowland ryegrass hay, grass–maize silage mix, pure hemicellulose) as well as in the content of nutrients. Concentrations of phenolic compounds in the incubated forages were (g/kg dry matter (DM)): 20 (tannin proportion: 0.47), 8 (0.27), 15 (0.52) and 0 (0), respectively. Crude protein was highest in the silage mix and lowest with hemicellulose, whereas the opposite was the case for fiber. The total phenol contents (g/kg DM) for the high altitude and the lowland diet of the donor cow were 27 (tannins: 0.50 of phenols) and 12 (0.27), respectively. Independent of the origin of the rumen fluid, the incubation with alpine hay decreased (P < 0.05) bacterial counts, fermentation gas amount, volatile fatty acid (VFA) production as well as ammonia and methane concentrations in fermentation gas (the latter two being not lower when compared with hemicellulose). Alpine grazing of the cow in turn increased (P < 0.001) bacterial counts and, to a lesser extent, acetate proportion compared with lowland feeding. Further, alpine grazing decreased protozoal count (P < 0.05) and VFA production (P < 0.001) to a small extent, whereas methane remained widely unchanged. There were interactions (P < 0.05) between forage type incubated and feeding period of the donor cow in protozoal counts, acetate:propionate ratio, fermentation gas production and its content of methane, in vitro organic matter digestibility and metabolizable energy. Although increased phenolic compounds were the most consistent common property of the applied alpine forages, a clear attribution to certain effects was not possible in this study. As a further result, adaptation (long-term for donor cow, short term for 24 h incubations) appears to influence the expression of alpine forage effects in ruminal fermentation.     

Feeding-patch choice by red deer in relation to foraging efficiency

We tested the idea that ruminants allocate their feeding time to habitat patches in relation to foraging efficiency. We used five tame red deer (Cervus elaphus) in an enclosure planted with four treatment of timothy grass (Phleum pratense) differing in their stage of growth. Older swards offered higher biomass but lower nutritional quality than younger swards. We observed time spent feeding in each treatment during each of seven trials. We measured goodness-of-fit between observed times and predictions from two alternative hypotheses differing in optimization strategy (maximizing versus matching), and a third, null hypothesis. We tested the hypotheses using two alternative currecies: digestible protein, and digestible dry matter or energy. Although digestible protein concentration and dry-matter digestibility were highly correlated (r=0.763, P<0.001), the wider range of digestible protein made it the much more sensitive measure of forage quality. Distributions of feeding time closely matched estimated intake rates of digestible protein (R _infPred ^sup2 =0.899) across all animals and trials. The other hypotheses were rejected. The results have important ecological implications in showing the underlying role of food in the selection of habitat by ruminants, and that simple, mechanistic models of forage intake and digestion can be scaled up to the level of animal behavioural choices.     

Energy and mineral nutrition and water intake in the captive Indian rhinoceros (Rhinoceros unicornis)

In the captive Indian rhinoceros (Rhinoceros unicornis), two disease complexes with a high incidence—chronic foot problems and uterine leiomyomas—may be linked to excess body weight (BW). In this study, intake and digestion trials were conducted (by means of 7‐day weigh‐backs, and 5‐day total fecal collections, respectively) with 11 Indian rhinoceroses at four zoological institutions in Europe and the United States to quantify energy and mineral nutrition on conventional or roughage‐only diets. Diets comprising a variety of forages (grass hay only, a combination of grass hay and grass silage, straw, or a mixture of grass and legume hay) were offered as the roughage source, along with various concentrates, produce, and supplements. Water intake was quantified, and urine samples were obtained opportunistically. The animals consumed 0.5–1.1% of their BW in dry matter (DM) daily, with calculated digestible energy (DE, in megajoules MJ) values ranging from 0.27 to 0.99 MJ DE/kg BW^0.75/day compared to an estimated requirement of 0.49–0.66 MJ DE/kg BW^0.75/day. Seven of 11 rhinos (64%) fed restricted levels of concentrate plus forage consumed DE in excess of this estimate. Even on roughage‐only diets, some individuals consumed energy well above the presumed metabolic requirements. Hence, restriction of both concentrates and roughage may be important for weight management in this species. Water intake ranged from 30 to 49 mL/kg BW daily (3.4–5.2 L/kg ingested DM), similar to values that have been reported for domestic equids. Excretion amounts and patterns also resembled those found in horses. Endogenous fecal losses measured for Ca, P, Cu, Fe, and Zn indicate that the maintenance requirements of these minerals should be met in Indian rhinoceroses by diets that meet recommendations for domestic horses. It is particularly important to evaluate dietary adequacy in mineral nutrition in this species in concert with the need for restricted energy intake, especially with regard to the hypothetical involvement of a low Zn supply in chronic foot problems. Zoo Biol 24:1–14, 2005. © 2005 Wiley‐Liss, Inc.