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PubMed2001

Genotype x environment interactions in milk yield and quality in Angus, Brahman, and reciprocal-cross cows on different forage systems.

Milk yield and quality were observed on 93 Angus, Brahman, and reciprocal-cross cows over 3 yr to evaluate the interactions of direct and maternal breed effects and heterosis with forage environment. Forage environments were common bermudagrass (BG), endophyte-infected tall fescue (E+), and a rotational system (ROT) of both forages, in which each forage (BG or E+) was grazed during its appropriate season, usually June through October for BG and November through May for E+. Milk yield was estimated each of 6 mo (April through September) via milking machine and converted to a 24-h basis. Milk fat, milk protein, and somatic cell count were analyzed by a commercial laboratory. Heterosis for milk yield was similar among forages, averaging 2.4 kg (P < 0.01). Expressed as percentages of purebred means, heterosis for milk yield was largest on E+ (52.8%), intermediate on ROT (39.3%), and smallest on BG (23.7%). Direct breed effects for milk yield favored Brahman, and they were similar among forages but tended to be larger for E+ (2.5 kg) and ROT (2.8 kg) than for BG (1.3 kg). Direct breed effects for milk fat favored Brahman and were similar among forages but tended to be larger for E+ (1.0%) and ROT (1.0%) than for BG (0.6%). Purebred cows exceeded crossbreds in milk protein by 0.1% on ROT (P < 0.10). Crossbred cows had lower somatic cell counts than purebreds on BG (P < 0.05), E+ (P < 0.01), or ROT (P > 0.30). Heterosis for somatic cell counts as percentages of purebred means was similar for BG (-68.3%) and E+ (-68.9%) and less favorable for ROT (-31.6%). Maternal breed effects for somatic cell count favored Angus on ROT (P < 0.10) with a similar nonsignificant trend on BG and E+. Direct breed effects for somatic cell count favored Brahman on ROT (P < 0.10) with similar nonsignificant trends on BG and E+. These results suggested that a rotation of cows from E+ to BG in the summer can partially alleviate negative effects of E+ on milk yield. Conclusions also indicated an advantage to crossbred cows in somatic cell count and provided evidence of both direct and maternal breed effects for this trait. The results also suggested that direct breed effects for milk yield, milk fat, and somatic cell count and heterosis for milk yield and somatic cell count (as percentages of purebred means) tended to vary with forage environment, indicating a potential for genotype x environment interaction for these traits.

Animal Feed↗
PubMed2002

Effects of supplementation on intake, digestion, and performance of beef cattle consuming fertilized, stockpiled bermudagrass forage.

Experiments were conducted to determine the effects of increasing supplement protein concentration on performance and forage intake of beef cows and forage utilization of steers consuming stockpiled bermudagrass forage. Bermudagrass pastures were fertilized with 56 kg of N/ha in late August. Grazing was initiated during early November and continued through the end of January each year. Treatments for the cow performance trials were: no supplement or daily equivalents of 0.2, 0.4, and 0.6 g of supplemental protein per kilogram of BW. Supplements were formulated to be isocaloric, fed at the equivalent of 0.91 kg/d, and prorated for 4 d/wk feeding. Varying the concentration of soybean hulls and soybean meal in the supplements created incremental increases in protein. During yr 1, supplemented cows lost less weight and condition compared to unsupplemented animals (P < 0.05). During yr 2, supplemented cows gained more weight (P = 0.06) and lost less condition (P < 0.05) compared to unsupplemented cows. Increasing supplement protein concentration had no affect on cumulative cow weight change or cumulative body condition score change. Forage intake tended to increase (P = 0.13, yr 1 and P = 0.07, yr 2) in supplemented cows. Supplement protein concentration did not alter forage intake. In a digestion trial, four crossbred steers were used in a Latin square design to determine the effects of supplement protein concentration on intake and digestibility of hay harvested from stockpiled bermudagrass pasture. Treatments were no supplement; or 0.23, 0.46, and 0.69 g of supplemental protein per kilogram of BW. Forage intake increased (P < 0.05) 16% and OM intake increased (P < 0.01) 30% in supplemented compared to unsupplemented steers. Diet OM digestibility increased (P = 0.08) 14.5% and total digestible OM intake increased (P < 0.05) 49% in supplemented compared to unsupplemented steers. Supplement protein concentration did not alter forage intake, total digestible OM intake, or apparent digestibility of OM or NDF. During the initial 30 d after first killing frost, beef cows did not respond to supplementation. However, later in the winter, supplementation improved utilization of stockpiled bermudagrass forage.

Animal Feed↗
PubMed2002

Effects of forage particle size and grain fermentability in midlactation cows. II. Ruminal pH and chewing activity.

Our study investigated the effects of, and interactions between, level of dietary ruminally fermentable carbohydrate (RFC) and forage particle size on rumen pH and chewing activity for dairy cows fed one level of dietary NDF. Also, correlations between intake, production, chewing, and ruminal pH parameters were investigated. Eight cows (61 days in milk) were assigned to four treatments in a double 4 x 4 Latin square. Treatments were arranged in a 2 x 2 factorial design; finely chopped alfalfa silage (FS) and coarse alfalfa silage (CS) were combined with concentrates based on either dry, cracked-shelled corn (DC; low RFC) or ground, high-moisture corn (HMC; high RFC). Diets were fed ad libitum as a total mixed rations with a concentrate:forage ratio of 60:40. Diets averaged 18.7% crude protein, 24.0% neutral detergent fiber, 18.3% , acid detergent fiber and 27.4% starch on a DM basis. Mean particle size of the four diets were 6.3, 2.8, 6.0, and 3.0 mm for DCCS, DCFS, HMCCS, and HMCFS, respectively. Decreasing forage particle size decreased ruminal pH from 6.02 to 5.81, and increasing level of RFC decreased pH from 5.99 to 5.85. Minimum daily ruminal pH decreased from 5.66 to 5.47 when level of RFC was increased, and decreased from 5.65 to 5.48 when forage particle size decreased. Time below pH 5.8 per day increased from 7.4 h to 10.8 h when level of RFC increased, and increased from 6.4 h to 11.8 h when forage particle size was decreased. Area below 5.8 showed the same relationship with RFC and forage particle size. Also, forage particle size affected the postprandial pH pattern. Cows spent more time eating when fed CS compared with FS (274 vs. 237 min/d), and time spent eating decreased when level of RFC was increased (271 vs. 241 min/d). Decreasing forage particle size decreased time spent ruminating (485 vs. 320 min/d), rumination periods (15.3 vs. 11.7), and duration of rumination periods (29 vs. 26 min). Increasing level of RFC increased time spent ruminating per kg NDF intake (68.5 vs. 79.5 min/kg). Milk fat percentage was correlated to mean ruminal pH (r = 0.41), time spent below pH 5.8 (r = -0.55), and area below 5.8 (r = -0.57), but not to intake or chewing variables. DMI of particles retained on a screen equivalent in size to the top screen of the Penn State particle separator was the intake parameter explaining most of the variation in mean ruminal pH (r = 0.27) and was correlated to time spent ruminating (r = 0.61) and chewing (r = 0.61).

Animal Feed↗
PubMed2003

Pasture forages, supplementation rate, and stocking rate effects on dairy cow performance.

Objectives were to evaluate effects of forage species, stocking rate, and supplementation rate on performance and physiology of grazing lactating Holstein cows under intensive rotational stocking management during summer. Eight treatments were arranged in a 2 x 2 x 2 factorial design. Animals (n = 62) grazed pastures of Tifton 85 bermudagrass or Florigraze rhizoma peanut, a tropical legume. Low and high stocking rates were 7.5 and 10.0 cows/ha for bermudagrass and 5.0 and 7.5 cows/ha for rhizoma peanut. Within each forage-stocking rate combination, cows were fed supplement at 0.33 or 0.5 kg of supplement (as-fed basis)/kg daily milk production. Cows grazing rhizoma peanut pastures produced more milk (16.9 vs. 15.4 kg/d) but had higher rectal temperatures (39.4 vs. 39.1 degrees C). Milk production per cow was improved at the higher stocking rate for bermudagrass but was reduced at the higher stocking rate for peanuts. Increasing supplementation rate boosted plasma glucose, milk production, and milk protein percent. Increased supplementation rate had a greater positive impact on milk production of cows grazing bermudagrass compared to rhizoma peanut (21.9 vs. 10.6% increase) due to a lower substitution of grain for forage intake. Organic matter intakes of forage, supplement, and total diet were greatest by cows grazing rhizoma peanut pastures and averaged 12.4, 6.1, and 18.5 kg/d compared to 9.2, 5.4, and 14.6 kg/d for cows grazing bermudagrass. Despite lower individual feed intake and performance, production per unit land area was 29% greater (112 vs. 90 kg of milk/ha per d) for cows grazing bermudagrass due to the greater stocking rate possible with that forage. Only cows supplemented at the high rate and kept at the high stocking rate on bermudagrass maintained body weight. Cows on other treatments lost body weight. Tifton 85 bermudagrass appears to be an excellent summer forage for dairy cows grazing in the southeastern U.S. given its nutritive value characteristics and high yields. Optimum stocking rate may be as high as 10 cows/ha during times of peak growth of forage for low-to-moderately producing cows fed supplement. Furthermore, the positive milk production response to additional supplement when cows grazed Tifton 85 pastures (0.8 kg/kg of supplement), indicates the value of providing supplement to cows grazing this moderate quality forage.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Fresh forage and solin supplementation on conjugated linoleic acid levels in plasma and milk.

Two experiments were run concurrently to determine the effect of fresh forage consumption on the production and proportions of plasma and milk fat vaccenic acid (VA), conjugated linoleic acid (CLA), and linolenic acid in diary cattle. In experiment 1, the cows consumed 50, 65, and 80% of their feed intake as pasture with the remainder of intake as a barley-based concentrate. The proportion of VA in milk fatty acids increased 12% when pasture intake increased from 50 to 65% of total dry matter intake and VA, CLA, and linolenic acid proportions increased 26, 18, and 27%, respectively, as pasture increased from 65 to 80% of dietary intake. In experiment 2, fresh forage was compared to conserved hay (cut from the same pasture the previous summer) to determine the effect on plasma and milk fat VA, CLA, and linolenic acid. Also, the effect of crushed solin seed (a flax cultivar that is high in linoleic acid) supplementation to the fresh forage diet was determined. Fresh forage compared to conserved hay in the diet, increased the proportion of CLA in the plasma very low density lipoproteins (VLDL) fraction by 71% but had no effect on linolenic acid. Supplementation of the fresh forage diet with a linoleic acid source increased VA and CLA in the plasma VLDL fraction 25 and 58% and slightly decreased the proportion of linolenic acid. Fresh forage, compared to conserved hay, increased milk fat VA and CLA proportions by 22 and 15%. Supplementing the fresh forage diet with linoleic acid from crushed solin seed further increased milk fat VA and CLA proportions 41 and 25%. Solin supplementation in a lactation diet is a superior method to increase CLA levels in milk fat than feeding fresh forage alone.

Animals↗
PubMed1997

Effect of percentage of dietary forage neutral detergent fiber and source of starch on performance of lactating Jersey cows.

Five Jersey cows were used in a 5 x 5 Latin square design to determine the effects of decreasing dietary forage neutral detergent fiber (NDF) and different sources of dietary starch on performance and nutrient digestibilities. The control diet was balanced to consist of 21% forage NDF and 43% nonfiber carbohydrates. Four other diets were balanced to contain 35% nonfiber carbohydrates and either 16 or 11% forage NDF; diets were arranged in a 2 x 2 factorial design with either corn or corn and wheat as the sources of starch. Dry matter intake decreased linearly as forage NDF decreased; however, most of the decrease occurred when forage NDF was reduced from 16 to 11%. Milk production, yield of 4% fat-corrected milk, and percentages of milk fat and protein were similar among diets. Digestibility of NDF and acid detergent fiber increased as forage NDF decreased, but fiber digestibilities decreased with the addition of wheat to the diets. Starch digestibility was similar among diets. Source and amount of starch may be equally important or more important than the percentage of forage NDF for maintaining nutrient digestibilities of the total tract. Forage NDF in the diets of high producing cows can be reduced to 16% when sources and concentrations of starch are adequately balanced.

Animal Feed↗
PubMed1997

Interactions among forages and nonforage fiber sources.

Source, amount, and physical characteristics of dietary forage can interact with nonforage fiber sources and influence ruminal and total tract fiber digestion, passage, and performance of dairy cows fed diets containing substantial nonforage fiber in place of forage. Dietary NDF from forage can be reduced to < = 60% and still provide sufficient amounts of effective fiber for FCM production that is similar to or superior to that with high forage diets. Because of small particle size and high specific gravity, increased ruminal rate of passage may be responsible for lower ruminal NDF digestibility of nonforage fiber sources fed at high dietary amounts. As the amount of soybean hulls increased from 50 to 95% of a pelleted mix for dairy cows, passage rate increased by 8%. In five studies, the digestion of soybean hull diets was improved by the addition of coarse forage. Fiber digestibility might have improved because coarse hay increased ruminal retention time of nonforage fiber sources and allowed more complete digestion. Addition of coarsely chopped alfalfa hay to diets based on silage containing 25% soybean hulls increased ruminal mat consistency by 49% and tended to slow the ruminal escape rate of soybean hulls by 16%. When high percentage of nonforage fiber are fed, the amount of dietary forage is necessarily low, and forage particle size should be adequate to stimulate rumination and entrap small feed particles. The amount and particle size of forage in the diet interacts with the substituted nonforage fiber source to determine the net impact on the rate of ruminal digestion and passage of nonforage fiber.

Animal Feed↗
PubMed1999

In situ dry matter and crude protein degradation of fresh forages during the spring growth.

We compared ruminal dry matter (DM) and crude protein (CP) degradation kinetics of fresh forages of alfalfa (vegetative, early bud, early flowering, and late flowering stages) and bromegrass with endophyte-free and endophyte-infected tall fescue (tillering, stem elongation, heading, and flowering stages) by using nonlinear models. Duplicate Dacron bags were incubated for 0, 3, 6, 9, 12, 16, 24, 36, 48, and 60 h in 2 Simmental x Angus steers fitted with ruminal cannulas. The effects of animal, forage species, and maturity within forage species were evaluated. A first-order kinetics model was determined to be suitable for estimation of degradation profiles relative to models with variable rate of degradations. Alfalfa had higher soluble DM (36.6%), lower insoluble potentially digestible DM (43.0%), higher rate (13.8%/h), and higher extent of DM degradation (66.3%) than grasses (27.2, 53.5, 6.7%/h, and 54.6% for soluble DM, insoluble potentially digestible DM, rate, and extent of DM degradation, respectively). The extent of CP degradation was similar among forages (74.7%), but alfalfa had a higher CP degradation rate than grasses (16.1 vs. 12.5%/h). Extents of degradation of DM and CP decreased with maturity in alfalfa and in grasses. Ruminally undegradable CP (RUP) was higher in alfalfa (40.0 g/kg of DM) than in grasses (34.9 g/kg of DM), and decreased with maturity in grasses (40.4 to 28.3 g/kg of DM) but not in alfalfa. The amount of RUP that was potentially degradable in the rumen was not different among forage species (22.1 g/kg). As forage CP concentration decreased, the RUP (as a percentage of CP) increased but, as a percentage of forage DM, decreased. Species of forage had important effects on ruminal DM and CP degradation when incubated in fresh form.

Animal Feed↗
PubMed2001

Nutrient foraging in woodland herbs: a comparison of three species of Uvularia (Liliaceae) with contrasting belowground morphologies.

We compared the ability of three closely related species, Uvularia perfoliata, U. sessilifolia, and U. puberula, to forage and explore patches in nutritionally homogeneous and heterogeneous environments. The species differed in type and function of plagiotropic stems and the extent of clonality and physiological integration. Our aim was to determine (1) whether selective placement of roots in high-nutrient patches, i.e., foraging, was accompanied by facilitatory morphological changes such as internode elongation or increased branching, (2) whether foraging ability of species depended on the extent of physiological integration, and (3) how variability in environmental quality influenced the performance of each species. We studied the growth of each species over two seasons in experimental environments. Uvularia perfoliata and U. puberula foraged in high-nutrient patches in heterogeneous environments. Uvularia sessilifolia did not show selective placement of roots. The two clonal species, U. perfoliata and U. sessilifolia, did not show any changes in architectural traits predicted to facilitate foraging. The nonclonal species, U. puberula, was the strongest forager and the most physiologically integrated species, U. sessilifolia, was the weakest forager, in line with the view that physiological integration limits foraging efficiency. Variability in environmental quality had little effect on the performance of the three species. Yield and estimators of fitness were not greater in treatments where more high-quality patches were encountered consecutively than in treatments where fewer high-quality patches were encountered consecutively during growth.

Journal Article↗
PubMed2026

Uncovering the early and conserved molecular mechanisms of root nitrogen foraging in model and crops.

BACKGROUND: Nitrogen (N) foraging, the ability of plants to promote preferential root growth in N-rich patches of soil, is fundamental to the competitiveness and wellbeing of plants. A unique &#x201c;split-root&#x201d; system, where a heterogenous N environment stimulates root foraging, provides a powerful experimental model to study the mechanisms underlying root foraging in model (Arabidopsis) and/or crop plants. RESULTS: We used the split-root set up to capture early molecular events involved in systemic N-signaling after exposure to a heterogeneous N signal, through time-course transcriptomic analysis across shoots and roots of Arabidopsis. We found that a histone methyltransferase, SET DOMAIN GROUP 8 (SDG8), is necessary for root N-foraging, suggesting a previously unknown role for chromatin regulation in mediating the preferential root growth response to colonize N-rich patches. To determine if the underlying molecular mechanism is conserved in evolution, we compared the root foraging behavior from model-to-crop (Arabidopsis, tomato and maize). Our analysis showed the model and crop species shared a root N-foraging growth response, with some variation among specific genotypes. Interestingly, we observed both shared and distinct transcriptional responses to heterogenous N environments among these three species. CONCLUSIONS: Our study has generated insights into the molecular basis of root N-foraging, with the potential to improve nutrient use efficiency in crop plants in a heterogeneous field environment.

Crops, Agricultural↗
PubMed1992

Response of bonnet macaque dyads to an acute foraging task under different motivational conditions.

To explore behavioral patterns in bonnet macaque mother-infant dyads under environmental challenge, the motivation of infants to contact their mothers during a 1-hr foraging period was manipulated in two ways. First, sessions were given in which the infants were separated from their mothers for 3 hr prior to the foraging period. Second, sessions were given in which the infants were allowed access to food prior to the foraging period, thereby presumably reducing their motivation to separate from mother to seek food for themselves during the foraging period. Neither manipulation resulted in heightened conflict within the dyads. Separation of the infants prior to the foraging period did result, in general, in mothers forfeiting foraging task engagement to attend to their infants. The extent to which a mother exhibited this pattern correlated with her level of foraging effectiveness.

Animals↗
PubMed1997

Foraging currencies for non-energetic resources: pollen collection by bumblebees

Animals sometimes forage for resources whose benefits are not energy-based. In such cases, the benefits and costs of foraging cannot be directly compared, making it difficult to evaluate the currency of fitness maximized by the animal's behaviour. For bees, pollen represents such a resource, because they collect pollen as the sole protein source for developing larvae, rather than as a source of energy. This study compared three currencies that could be maximized during pollen collection by bumblebees (Bombus spp.) foraging on different lupin species (Lupinus spp.): pollen collected per inflorescence, pollen collection rate (gross benefits/time) and pollen collection efficiency (gross benefits/costs). Bees visiting lupin inflorescences begin foraging low on an inflorescence and then move upward through a gradient of increasing pollen availability. To maximize each currency, we predicted that a bee would begin foraging at a different position along a lupin inflorescence, depending on the relative influences of the time and energy costs associated with handling flowers and flight. Based on comparisons of observed and predicted starting positions for seven situations, maximization of gross pollen-collection efficiency predicted observed behaviour better than either pollen collected per inflorescence or gross rate of pollen collection. Such maximization of pollen-collection efficiency would enhance a bee's lifetime input of pollen to her colony, as has been demonstrated for nectar-collecting bees. Hence, the economics of foraging for non-energetic resources do not differ qualitatively from foraging for energy.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗
PubMed2000

Learning rules for social foragers: implications for the producer-scrounger game and ideal free distribution theory.

In population games, the optimal behaviour of a forager depends partly on courses of action selected by other individuals in the population. How individuals learn to allocate effort in foraging games involving frequency-dependent payoffs has been little examined. The performance of three different learning rules was investigated in several types of habitats in each of two population games. Learning rules allow individuals to weigh information about the past and the present and to choose among alternative patterns of behaviour. In the producer-scrounger game, foragers use producer to locate food patches and scrounger to exploit the food discoveries of others. In the ideal free distribution game, foragers that experience feeding interference from companions distribute themselves among heterogeneous food patches. In simulations of each population game, the use of different learning rules induced large variation in foraging behaviour, thus providing a tool to assess the relevance of each learning rule in experimental systems. Rare mutants using alternative learning rules often successfully invaded populations of foragers using other rules indicating that some learning rules are not stable when pitted against each other. Learning rules often closely approximated optimal behaviour in each population game suggesting that stimulus-response learning of contingencies created by foraging companions could be sufficient to perform at near-optimal level in two population games.

Animals↗
PubMed2004

Worker honey bee pheromone regulation of foraging ontogeny.

The evolution of sociality has configured communication chemicals, called primer pheromones, which play key roles in regulating the organization of social life. Primer pheromones exert relatively slow effects that fundamentally alter developmental, physiological, and neural systems. Here, I demonstrate how substances extracted from the surface of foraging and young pre-foraging worker bees regulated age at onset of foraging, a developmental process. Hexane-extractable compounds washed from foraging workers increased foraging age compared with controls, whereas extracts of young pre-foraging workers decreased foraging age. This represents the first known direct demonstration of primer pheromone activity derived from adult worker bees.

Aging↗
PubMed2006

Floral odor learning within the hive affects honeybees' foraging decisions.

Honeybees learn odor cues quickly and efficiently when visiting rewarding flowers. Memorization of these cues facilitates the localization and recognition of food sources during foraging flights. Bees can also use information gained inside the hive during social interactions with successful foragers. An important information cue that can be learned during these interactions is food odor. However, little is known about how floral odors learned in the hive affect later decisions of foragers in the field. We studied the effect of food scent on foraging preferences when this learning is acquired directly inside the hive. By using in-hive feeders that were removed 24 h before the test, we showed that foragers use the odor information acquired during a 3-day stimulation period with a scented solution during a food-choice situation outside the nest. This bias in food preference is maintained even 24 h after the replacement of all the hive combs. Thus, without being previously collected outside by foragers, food odors learned within the hive can be used during short-range foraging flights. Moreover, correct landings at a dual-choice device after replacing the storing combs suggests that long-term memories formed within the colony can be retrieved while bees search for food in the field.

Animals↗
PubMed2003

Trophallaxis in forager honeybees (Apis mellifera): resource uncertainty enhances begging contacts?

Trophallaxis among adult worker honeybees is the transfer of liquid food by mouth from one individual to another. Within the colony, nectar foragers perform offering contacts (as food-donors) to transfer the contents of their crops to recipient nest-mates and, in addition, they also perform begging contacts (as food-receivers). The biological relevance of these last interactions remains unknown. Previous evidence suggests that begging may be involved in the exchange of information on food resources that occurs naturally between employed foragers and nest-mates. This work was aimed to reveal possible connections between the information obtained while foraging and the begging behavior displayed inside the nest. Experiments were intended to (1) analyze whether chemosensory information obtained while foraging, i.e., odors and sucrose concentrations, affects begging behavior, and (2) determine whether resource uncertainty enhances begging contacts. Results showed that: (1) most begging contacts lasted less than 1 s, a duration which only allows receiving food samples from nest-mates; (2) the diversity of odors and sucrose concentrations at the feeding place enhances the occurrence of begging contacts; and (3) an increased resource uncertainty enhances the forager begging behavior. In addition, results suggest that foragers may direct their begging contacts frequently to other employed nectar foragers.

Animal Communication↗
PubMed2003

Crop scents affect the occurrence of trophallaxis among forager honeybees.

Previous evidence indicates that the recognition of the nectar delivered by forager honeybees within the colony may have been a primitive method of communication on food resources. Thus, the association between scent and reward that nectar foragers establish while they collect on a given flower species should be retrieved during trophallaxis, i.e., the transfer of liquid food by mouth, and, accordingly, foraging experience could affect the occurrence of these interactions inside the nest. We used experimental arenas to analyze how crop scents carried by donor bees affect trophallaxis among foragers, i.e., donors and receivers, which differ in their foraging experience. Results showed that whenever the foragers had collected unscented sugar solution from a feeder the presence of scents in the solution carried by donors did not affect the occurrence of trophallaxis nor its dynamics. In contrast, whenever the foragers had previous olfactory information, new scents present in the crop of the donors negatively affected the occurrence, but not the dynamics of trophallaxis. Thus, the association learned at the food source seems to be retrieved during trophallaxis, and it is possible that known scents present in the mouthparts of nest-mates may operate as a triggering stimulus to elicit trophallactic behavior within the hive.

Animal Communication↗
PubMed2004

Zebra mussels affect benthic predator foraging success and habitat choice on soft sediments.

The introduction of zebra mussels ( Dreissena spp.) to North America has resulted in dramatic changes to the complexity of benthic habitats. Changes in habitat complexity may have profound effects on predator-prey interactions in aquatic communities. Increased habitat complexity may affect prey and predator dynamics by reducing encounter rates and foraging success. Zebra mussels form thick contiguous colonies on both hard and soft substrates. While the colonization of substrata by zebra mussels has generally resulted in an increase in both the abundance and diversity of benthic invertebrate communities, it is not well known how these changes affect the foraging efficiencies of predators that prey on benthic invertebrates. We examined the effect of zebra mussels on the foraging success of four benthic predators with diverse prey-detection modalities that commonly forage in soft substrates: slimy sculpin ( Cottus cognatus), brown bullhead ( Ameirus nebulosus), log perch ( Percina caprodes), and crayfish ( Orconectes propinquus). We conducted laboratory experiments to assess the impact of zebra mussels on the foraging success of predators using a variety of prey species. We also examined habitat use by each predator over different time periods. Zebra mussel colonization of soft sediments significantly reduced the foraging efficiencies of all predators. However, the effect was dependent upon prey type. All four predators spent more time in zebra mussel habitat than in either gravel or bare sand. The overall effect of zebra mussels on benthic-feeding fishes is likely to involve a trade-off between the advantages of increased density of some prey types balanced against the reduction in foraging success resulting from potential refugia offered in the complex habitat created by zebra mussels.

Analysis of Variance↗