Feed intake and digestion in the maned wolf (Chrysocyon brachyurus): Consequences for dietary management

Captive maned wolves (Chrysocyon brachyurus) often consume diets high in prey and meat items even though they are omnivorous in the wild. These soft, high protein diets may exacerbate conditions of gingivitis and cystinuria in this species. Feed intakes were monitored in wolves provided with prey and meat-based diets (3 periods) and subsequently with extruded dog chows and small amounts of prey (2 periods). Digestibilities of each type of diet were measured with the indigestible marker chromic oxide. Dry matter intakes were similar between diets (374–584 g · 30 kg^?1 · d^?1), even though dietary protein content was reduced from 44% to 29% of dry matter. Digestibility of dry matter was unaltered by these dietary changes (77% of high prey diet vs. 73% of chow diet), but fecal consistency changed to softer stools at lower intakes of prey. Estimated metabolizable energy intakes of wolves (501–674 kJ · kg^?0.75 · d^?1) were similar to the maintenance requirement for domestic dogs (525 kJ · kg^?0.75 · d^?1), suggesting a similar energy requirement for maintenance of the wolves. The metabolizable energy derived from protein in the high prey diets was 37%, whereas that of the chow diets was only 27%. These levels exceed estimates of protein requirements for maintenance (4.3–21.8%) and growth (11.5–20.3%) in domestic dogs and may thus exceed those of the wolves. Dietary management of maned wolves should minimize excess protein intake by limiting prey consumption and acclimating animals to extruded diets for domestic dogs. Further research is required to formulate diets for long-term management of cystinuria in maned wolves. © 1994 Wiley-Liss, Inc.     

Wild canids,domestic dogs and their pathogens in Southeast Brazil: disease threats for canid conservation

Wild canids are under many pressures, including habitat loss, fragmentation and disease. The current lack of information on the status of wildlife health may hamper conservation efforts in Brazil. In this paper, we examined the prevalence of canine pathogens in 21 free-ranging wild canids, comprising 12 Cerdocyon thous (crab-eating fox), 7 Chrysocyon brachyurus (maned wolf), 2 Lycalopex vetulus (hoary fox), and 70 non-vaccinated domestic dogs from the Serra do Cipó National Park area, Southeast Brazil. For wild canids, seroprevalence of antibodies to canine parvovirus, canine adenovirus, canine coronavirus and Toxoplasma gondii was 100 (21/21), 33 (7/21), 5 (1/19) and 68 (13/19) percent, respectively. Antibodies against canine distemper virus, Neospora caninum or Babesia spp. were not found. We tested domestic dogs for antibodies to canine parvovirus, canine distemper virus and Babesia spp., and seroprevalences were 59 (41/70), 66 (46/70), and 42 (40/70) percent, respectively, with significantly higher prevalence in domestic dogs for CDV (P < 0.001) and Babesia spp. (P = 0.002), and in wild canids for CPV (P < 0.001). We report for the first time evidence of exposure to canine coronavirus in wild hoary foxes, and Platynossomun sp. infection in wild maned wolves. Maned wolves are more exposed to helminths than crab-eating foxes, with a higher prevalence of Trichuridae and Ancylostomidae in the area. The most common ectoparasites were Amblyomma cajennense, A. tigrinum, and Pulex irritans. Such data is useful information on infectious diseases of Brazilian wild canids, revealing pathogens as a threat to wild canids in the area. Control measures are discussed.     

Behavioral and physiologic responses to environmental enrichment in the maned wolf (Chrysocyon brachyurus)

The ex situ population of maned wolves is not self‐sustaining due to poor reproduction, caused primarily by parental incompetence. Studies have shown that environmental enrichment can promote natural parental behaviors in zoo animals. The objective of this study was to determine the effects of environmental enrichment on behavioral and physiological responses of maned wolves. During an 8‐week experimental period, daily behavior observations and fecal sample collection were conducted on four adult wolves (2.2) individually housed in environments without enrichment. After 2 weeks, the wolves were chronologically provided with 2‐week intervals of hiding dead mice around the exhibit, no enrichment, and introduction of boomer balls. Responses of the wolves to enrichment were assessed based on activity levels and exploratory rates, as well as the level of corticoid metabolites in fecal samples collected daily throughout the study period. Providing wolves with environmental enrichment significantly increased exploratory behaviors (P<0.05), especially when mice were hidden in the enclosure. Fecal corticoid concentrations were increased during periods of enrichment in males (P<0.05), but not in females. Overall, there were no correlations between behavioral responses to enrichment and fecal corticoid levels. Behavioral results suggest that environmental enrichment elicits positive effects on the behavior of captive maned wolves. There is evidence suggesting that providing animals with ability to forage for food is a more effective enrichment strategy than introducing objects. There is need for a longer term study to determine the impact of environmental enrichment in this species. Zoo Biol 26:331–343, 2007. © 2007 Wiley‐Liss, Inc.     

Influence of feeding raw or extruded feline diets on nutrient digestibility and nitrogen metabolism of African wildcats (Felis lybica)

The African wildcat is one of the closest ancestors to the domestic cat and is believed to have similar nutrient requirements, but research is lacking. The objective of this study was to determine the effects of feeding a high‐protein extruded kibble diet vs. a raw meat diet on nutrient digestibility, nitrogen metabolism, and blood metabolite concentrations in African wildcats. Five wildcats were randomized onto either a high‐protein (>50% crude protein) extruded kibble diet or a raw meat diet. The study was executed as a crossover design, with 21‐d periods, consisting of a 16‐d adaptation phase followed by a 4‐d total fecal and urine collection phase. Cats were housed individually in metabolism cages and fed to maintain body weight (BW). A fresh fecal sample was collected for short‐chain fatty acid (SCFA) and branched‐chain fatty acid (BCFA) analyses. Blood was analyzed for serum chemistry and leptin concentration. Food intake (as is) did not differ (P>0.05) between diets. Food intake and fecal output (g/d DMB) were greater (P<0.05) when cats consumed the kibble diet. Protein digestibility was higher (P<0.05) when cats were fed the raw meat diet vs. the kibble diet. Nitrogen intake was greater (P<0.05) when cats consumed the kibble diet, and more (P<0.05) nitrogen was present in the feces; however, the percentage of nitrogen retained and nitrogen balance did not differ (P>0.05). Fecal scores, ammonia, SCFA, and BCFA concentrations did not differ (P>0.05) between diets. Fecal butyrate molar ratio was higher (P<0.01) when cats consumed the kibble diet. Blood analyses demonstrated few differences between diets, but alanine aminotransferase activity and bicarbonate were higher (P<0.05) when cats consumed the commercial raw meat diet. Owing to lack of differences, these data indicate that African wildcats can readily utilize a high protein extruded kibble diet, and may be able to replace a commercial raw meat diet. Zoo Biol 29:676–686, 2010. © 2010 Wiley‐Liss, Inc.     

Evaluation of nutrient digestibility and fecal characteristics of exotic felids fed horse‐ or beef‐based diets: use of the domestic cat as a model for exotic felids

The objective of this study was to determine the effects of feeding commercially available beef‐ and horse‐based diets on nutrient digestibility and fecal characteristics of large captive exotic felids and domestic cats. Four species of large exotic felids including cheetahs, Malayan tigers, jaguars, and Amur tigers, and domestic cats were utilized in a crossover design. Raw meat diets included a beef‐based diet (57% protein; 28% fat) and a horse‐based diet (51% protein; 30% fat). All cats were acclimated to the diet for 16 days followed by a 4 day collection period, where total feces, including one fresh sample, were collected. All feces were scored on collection. Intake did not differ due to diet, but fecal output was greater when cats consumed the horse‐based diet. Total tract apparent dry matter (DM) digestibility was higher (P<0.05) and organic matter (OM) and crude protein (CP) digestibilities were lower (P<0.05) when cats were fed the beef‐based diet compared with the horse‐based diet. CP digestibility was similar in domestic cats and cheetahs, and greater (P<0.05) than Amur tigers. Fecal scores were lower and fecal DM was greater (P<0.05) when cats consumed the horse‐based diet compared with the beef‐based diet. Domestic cats had lower (P<0.05) fecal ammonia concentrations compared with all other species. Fecal ammonia concentrations were lowest (P<0.05) when cats were fed the horse‐based diet. Fecal total short‐chain fatty acid (SCFA), branched‐chain fatty acid (BCFA), and butyrate concentrations were higher (P<0.05) when cats consumed the beef‐based diet. Our results suggest that the domestic cat serves as an appropriate model for large exotic felid species, but differences among the species exist. Decreased nutrient digestibility by tigers and jaguars should be considered when developing feeding recommendations for these species based on domestic cat data. Zoo Biol 29:432–448, 2010. © 2009 Wiley‐Liss, Inc.     

Comparison of Mexican Wolf and Coyote Diets in Arizona and New Mexico

ABSTRACT Interactions between wolves (Canis lupus) and coyotes (C. latrans) can have significant impacts on their distribution and abundance. We compared diets of recently translocated Mexican wolves (C. l. baileyi) with diets of resident coyotes in Arizona and New Mexico, USA. We systematically collected scats during 2000 and 2001. Coyote diet was composed mostly of mammalian species, followed by vegetation and insects. Elk (Cervus elaphus) was the most common item in coyote scats. Mexican wolf diet had a higher proportion of large mammals and fewer small mammals than coyote diet; however, elk was also the most common food item in Mexican wolf scats. Our results suggest that Mexican wolf diet was more similar to coyote diet than previously reported, but coyotes had more seasonal variation. Considering results in other areas, we expect that Mexican wolves will have a negative impact on coyotes through direct mortality and possibly competition. Reintroduction of Mexican wolves may have great impacts on communities by changing relationships among other predators and their prey.     

Camera-trap studies of maned wolf density in the Cerrado and the Pantanal of Brazil

The maned wolf (Chrysocyon brachyurus) is threatened by large-scale habitat loss, in particular due to conversion to agricultural land. This is the first published study on maned wolf density and the first test of individual identification from camera-trap photographs. We present results from two Brazilian regions: the Cerrado and the Pantanal. Using capture–recapture analysis of camera-trap data, we estimated densities per 100 square kilometers of 3.64 ± 0.77 individuals at the Cerrado site and 1.56 ± 0.77 individuals at the Pantanal site. Parallel radio-telemetry studies at the Pantanal site showed that maned wolves occupied home ranges of 39–58 km² (mean = 50.3 ± 7.67 km²). Our study in the Cerrado took place in a private farm with a mixture of agricultural land and native habitats, representative of the majority of the present-day Cerrado. Whereas many other mammalian species have suffered in the region, our results show that the maned wolf may cope better with this highly fragmented landscape than one might have feared. Finally, the paper briefly compares maned wolf density with density of puma (Puma concolor) in the Pantanal site.     

Serum fatty acid analysis and digestibility study in the Vancouver Island marmot (Marmota vancouverensis) fed a captive diet supplemented with α‐linolenic acid

Mammals that hibernate must rely on endogenous lipid reserves to survive over winter. This study was conducted to compare the difference in serum fatty acid composition, dietary intake, and apparent digestibility in the Vancouver Island marmot (N = 6) fed the Metro Zoo lagomorph diet supplemented with α‐linolenic acid [C(18:3) n‐3 (α‐LA)]. The experiment was designed as a 3 × 3 Latin square with three 17‐day collection periods. The test diets contained 12.16, 14.85, and 17.05% α‐LA as a percentage of fatty acids in the diet supplied through the addition of flaxseed oil (～53% α‐LA). Across treatments, dry matter intake (g/d), dry matter digestibility, apparent fat digestibility, and apparent neutral detergent fiber digestibility did not differ significantly (P > 0.05). There were no significant differences in serum α‐LA concentration between the three levels of α‐LA supplementation. However, this supplementation did elevate serum α‐LA, eicosapentaenoic acid [C20:5 (n‐3)], and docosahexaenoic acid [C22:6 (n‐3)] levels compared with feeding the basal zoo lagomorph diet (P < 0.05). Thus, supplementation of the basal zoo lagomorph diet with α‐LA elevated the serum levels of essential fatty acids in the Vancouver Island marmot. Zoo Biol 20:251–259, 2001. © 2001 Wiley‐Liss, Inc.     

Encounter frequencies between GPS-collared wolves (Canis lupus) and moose (Alces alces) in a Scandinavian wolf territory

Over 6,000 GPS fixes from two wolves (Canis lupus) and 30,000 GPS fixes from five moose (Alces alces) in a wolf territory in southern Scandinavia were used to assess the static and dynamic interactions between predator and prey individuals. Our results showed that wolves were closer to some of the moose when inside their home ranges than expected if they had moved independently of each other, and we also found a higher number of close encounters (<500 m) than expected. This suggests that the wolves were actively seeking the individual moose within their territory. Furthermore, the wolves showed a preference for moving on gravel forest roads, which may be used as convenient travel routes when patrolling the territory and seeking areas where the moose are. However, due to the particularly large size of the wolf territory combined with relatively high moose densities, the wolves generally spent a very small proportion of their time inside the home range of each individual moose, and the frequency of encounters between the wolves and any particular moose was very low. We suggest that the high moose:wolf ratio in this large Scandinavian wolf territory compared to that typically occurring in North America, results in a relatively low encounter frequency and a low predation risk for individual moose, as the predation pressure is spread over a high number of prey individuals.     

Taurine deficiency in maned wolves (Chrysocyon brachyurus) maintained on two diets manufactured for prevention of cystine urolithiasis

This study assesses the long‐term effects of an experimental diet vs. a commercially available manufactured diet, intended to reduce clinical disease related to cystinuria, on the taurine status of captive maned wolves. For 13 weeks, two pairs of maned wolves were maintained on the commercially available maintenance diet, whereas two individually housed wolves were maintained on the experimental diet. All six wolves, at the beginning and at the end of the diet trial, had severely decreased plasma concentrations of taurine (as compared to the normal canine reference range of 60–120 nmol/ml) (National Research Council [2003] National Academies Press) with average taurine concentrations of 16 nmol/ml at the beginning of the study and 3 nmol/ml at the end of the study. There was no statistically significant difference in the taurine concentrations between animals on the maintenance vs. experimental diets. Both diets were supplemented subsequently with taurine at a concentration of 0.3%. All study animals were eventually switched to the taurine‐supplemented version of the commercially manufactured maintenance diet and subsequent samplings were carried out to monitor plasma taurine concentrations. A final sampling, carried out approximately 5 months after the initiation of taurine supplementation, showed an average taurine concentration within the target canine reference range (90.25 nmol/ml). There are numerous physiologic (e.g., possible unique metabolism and requirements for taurine in this species as compared to other canids) and dietary factors (e.g., effects of the types and concentrations of fiber and protein on nutrient availability, taurine metabolism, and enterohepatic circulation of taurine‐conjugated bile salts; impaired taurine synthesis secondary to low cysteine availability) that could be potential contributors to the development of taurine deficiency in the maned wolves in this study. Taurine supplementation should be considered in maned wolves maintained on diets intended for reduction of cystinuria‐related complications. Zoo Biol 0:1–14, 2005. © 2005 Wiley‐Liss, Inc.     

Food habits of three carnivores in a mosaic landscape of São Paulo state,Brazil

São Paulo is the most developed state in Brazil, but despite intense land use changes, some mammal species still inhabit remnant fragments of native vegetation of the state. We used fecal analyses to investigate prey diversity, trophic niche breadth, and trophic niche overlap of pumas, ocelots, and maned wolves in protected and non-protected areas in São Paulo state. During 18 months, we inspected more than 10,000 km of roads and trails and collected 233 fecal samples. Maned wolves showed generalist food habit, ocelots were predominantly carnivores, and pumas were strict carnivores. The European hare, an exotic species which had not yet been reported in the study area, was identified in the feces of a puma. Trophic niche breadth was the lowest for maned wolves (BA?=?0.339) and the highest for pumas (BA?=?0.723). Trophic niche overlap was high between maned wolves and ocelots (O_jk?=?0.765) and between pumas and ocelots (O_jk?=?0.639). Significantly different diets of maned wolves and ocelots were observed between dry and rainy seasons. Our findings indicate that these three species may adapt their diets to the disturbed landscapes. This is the second study characterizing food habits of ocelots in Cerrado areas but the first considering a large number of samples.     

Selected Gelling Agents in Canned Dog Food Affect Nutrient Digestibilities and Fecal Characteristics of Ileal Cannulated Dogs

Little is known about the effects of gelling agents in canned dog food on nutrient digestibilities and fecal characteristics. Dogs were fed canned diets with either no gelling agent (control) or one of three gelling agents, wheat starch, a guar gum/carrageenan mixture (50:50), and a locust bean meal (LBM)/ carrageenan mixture (50:50) incorporated at two levels (0.2 and 0.5% of the diet on a wet weight basis). Six dogs were fed each diet in a 6 ‐ 7 Youden square design. Dogs fed diets containing gelling agents had higher ileal digestibilities of OM (P = 0.05), fat (P < 0.01), GE (P = 0.02), and total amino acids (P = 0.04) and lower (P < 0.01) total tract DM digestibilities when compared to dogs fed the control diet. Fecal output by dogs fed the control diet, expressed on both an as-is (73.4g/d) and DM (45.6g/d) basis, was lower (P < 0.01) than for dogs fed gelling agent-containing diets (mean 102.3g/d as-is and 57.6g/d DM). Dogs fed the control diet also had lower ( P < 0.01) fecal DM percentages and higher (P = 0.02) fecal scores than dogs fed gelling agent-containing diets.     

Assessment of anadromous salmon resources in the diet of the Alexander Archipelago wolf using stable isotope analysis

The Alexander Archipelago wolf (Canis lupus ligoni) is unique to southeast Alaska, occurring on islands south of Frederick Sound and along the mainland between Dixon Entrance and Yakutat Bay. Sitka black-tailed deer (Odocoileus hemionus sitkensis) are an important prey species for wolves across the southern part of the region. Spawning salmon (Onchorynchus sp.) are seasonally available but their presence in wolf diets has not previously been quantified. We examined the range of bone collagen δ¹³C and δ¹⁵N values for wolves throughout southeast (n = 163) and interior (n = 50) Alaska and used a dual-isotope mixing model to determine the relative contribution of salmon-derived marine protein in the diet. Southeast Alaska wolves consumed significantly more salmon (mean ± SE: 18.3 ± 1.2%) than did wolves from interior Alaska (9.1 ± 0.6%, P<0.001). Wolves on the southeast Alaska mainland appeared to have higher marine isotopic signatures than island wolves, although this difference was not significant. Variation among individual wolf diets was higher for southeast than for interior Alaska wolves, and variation was highest in coastal mainland wolf diets (P<0.001). Marine resources may augment the diet of southeast Alaska wolves during seasonal or annual fluctuations in the availability of deer, particularly in those areas on the mainland where densities of terrestrial ungulates are relatively low. Received: 1 July 1998 / Accepted: 23 February 1999     

Food habits of the world's grey wolves

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Effects of Different Dietary Manganese Levels on Growth Performance and N Balance of Growing Mink (Neovision vision)

Two experiments were conducted to study the effects of dietary manganese levels on growth performance, nutrients digestibility, and N balance of minks during growing period. In experiment 1, 75 healthy male minks (60 days old) were selected and randomly divided into five groups with different types of diet. The diet was supplemented with 0 (control), 50, 100, 300, and 600 ppm of manganese as MnSO₄ of dry matter (DM) in basic diet, respectively. From early July to middle September, the results showed that the final body weights of minks were significantly affected by diets (P?<?0.05). Average daily gains (ADG) were significantly higher in the 300-ppm manganese group than those in other groups. The ratio of feed to body weight gain (F/G) was significantly affected by manganese level (P?<?0.05). In experiment 2, 45 male minks (75 days old) with the same body weight were selected from each group of experiment 1 to carry out the nutrient digestion and N-balance tests which lasted for 4 days for the collection of the feces and urine, and the diets and treatment codes were same as in experiment 1. The results showed that no significant differences were found in DM, crude protein (CP), and crude carbohydrate (CC) digestibility among all groups (P?>?0.05), but ether extract (EE) and gross energy (GE) digestibility were all the highest in the 300-ppm group. N intake and fecal N were similar among all groups (P?>?0.05). Urinary N was lower in the 300-ppm group; in contrast, N retention was higher in this group (P?<?0.05). In conclusion of experiment 1 and experiment 2, the diet supplemented with 300 ppm of manganese (as manganese sulfate) could improve the growth performance and increase the EE and GE digestibility of mink during the growing period and moreover reduce the nitrogen emissions to the environment, and the optimal total manganese level in mink’s diet was 409.16 in DM during the growing period.     

Viral gut metagenomics of sympatric wild and domestic canids,and monitoring of viruses: Insights from an endangered wolf population

Animal host–microbe interactions are a relevant concern for wildlife conservation, particularly regarding generalist pathogens, where domestic host species can play a role in the transmission of infectious agents, such as viruses, to wild animals. Knowledge on viral circulation in wild host species is still scarce and can be improved by the recent advent of modern molecular approaches. We aimed to characterize the fecal virome and identify viruses of potential conservation relevance of diarrheic free‐ranging wolves and sympatric domestic dogs from Central Portugal, where a small and threatened wolf population persists in a highly anthropogenically modified landscape. Using viral metagenomics, we screened diarrheic stools collected from wolves (n = 8), feral dogs (n = 4), and pet dogs (n = 6), all collected within wolf range. We detected novel highly divergent viruses as well as known viral pathogens with established effects on population dynamics, including canine distemper virus, a novel bocavirus, and canine minute virus. Furthermore, we performed a 4‐year survey for the six wolf packs comprising this endangered wolf population, screening 93 fecal samples from 36 genetically identified wolves for canine distemper virus and the novel bocavirus, previously identified using our metagenomics approach. Our novel approach using metagenomics for viral screening in noninvasive samples of wolves and dogs has profound implications on the knowledge of both virology and wildlife diseases, establishing a complementary tool to traditional screening methods for the conservation of threatened species.     

First observations of nest attendance behavior by wild maned wolves,Chrysocyon brachyurus

In many species of canids the male's role in reproduction extends to providing extensive or some parental care to his offspring. Maned wolves are a monogamous canid species whose males have been observed providing parental care to their offspring in captivity, but no field observations exist. We observed a wild pair of maned wolves at their nest site in a period soon after the female had given birth for a total period of 65 days. We made five observation sessions with an average of 3–4 days each separated by approximately 2 weeks. Direct visual observations of maned wolves were made each 30 min during the hours of darkness (17:00–07:00) using night-vision binoculars and confirmed by VHF radiotelemetry. During observations we recorded the location of the male and the female in relation to the nest (i.e., in the nest, nearby or long way from the nest). The results showed that the female spent more than 60.44% of her time in or near the nest. The male spent 28.90% of his time in or near the nest. There was a positive significant correlation between the female and the male in terms of the amount of time spent in or near the nest (P<0.01). The maned wolves showed a strong temporal variation in time spent in or near the nest. In conclusion, our data show that wild male maned wolves—probably—provide parental care through provision of food to their female and presumed offspring rather than “babysitting.” Zoo Biol 28:69–74, 2009. © 2008 Wiley-Liss, Inc.     

The effect of replacing rice straw with dry wormwood (Artemisia sp.) on intake,digestibility, nitrogen balance and ruminal fermentation characteristics in sheep

This study examined the effect of substituting dry wormwood (Artemisia sp.) for rice straw in sheep diets on intake and apparent digestibility in vivo, nitrogen (N) balance and ruminal fermentation characteristics. Four Corriedale×Polwarth sheep (51.7 ± 1.3 kg) were individually housed in metabolism cages and fed diets (ad. libitum) with a 70:30 forage to concentrate ratio (DM basis), in which the basal rice straw was substituted with 0 (Control), 30 (LW), 50 (MW) or 100 (HW) g/kg of dry wormwood. The experimental design was a 4×4 latin square design in which 10 days of dietary adaptation was followed by 6 days of total feces and urine collection in each period. Rumen fluid was collected from a stomach tube at −0.5, 0.5, 1, 2, 4, and 8 h after the morning feed on day 6 of each collection period and analyzed for volatile fatty acids (VFA). The intakes of dry matter (DM), organic matter intake (OM), crude protein (CP), ether extract (EE), neutral detergent fibre (NDF) and acid detergent fibre (ADF) were higher (P<0.05) in sheep fed diets containing wormwood, than those fed the Control diet. Compared to the Control diet, CP digestibility was higher (P<0.05) in sheep fed MW and N intake, retained N, EE digestibility, urinary purine derivatives and microbial N yield were higher (P<0.05) in sheep fed diets, containing wormwood. Rumen pH was unaffected by treatment. Rumen NH₃-N and VFA concentrations were similar across treatments except that most values for diets containing wormwood were higher (P<0.05) than those for the control diet within the first 2 h of feeding. The non-glucogenic acid ratio was also similar across Control, LW and MW treatments, but it was generally lower in MW versus the Control treatment. In conclusion, substituting wormwood for rice straw in the sheep diets increased feed intake, rumen fermentation, in vivo digestibility, N retention and microbial N yield, particularly at the medium and high levels of wormwood inclusion.     

Digestibility of diets containing increasing levels of NaOH-treated or untreated wheat straw

Sodium hydroxide-treated or untreated wheat straw was included in a basal alfalfamaize diet at 0, 10, 20 and 40%. As the level of straw increased, the apparent digestibility of dry matter (DM) and organic matter (OM) by sheep, decreased linearly (P < 0.01), with a faster decrease (P < 0.05) for diets containing untreated straw. The digestibility of DM decreased by 0.22 and 0.41% and OM by 0.24 and 0.42% for treated and untreated straw diets, respectively, with each 1% increase of straw in the diets.Addition of treated straw increased (P < 0.05) digestibility of cell wall constituents (CWC), acid detergent fibre (ADF) and hemicellulose (HC). However, when untreated straw was added, the digestibility of HC was reduced, whereas the digestibility of CWC and ADF was dependent on the level of straw added. Increasing levels of NaOH-treated straw in the diets produced linear increases (P < 0.05) in digestibility of CWC, ADF and HC. However, significant (P < 0.05) linear or quadratic responses were not noted in the digestibility of CWC, ADF and HC with increasing levels of untreated straw in the diet. Apparent digestibility of crude protein was not affected by addition of either NaOH-treated or untreated straw to the diet.In general, although changes in nutrient digestibility of the basal component small, large changes in the digestibility of nutrients in the straw component were apparent and accounted for the major differences in digestibility of the diets. The absence of curvilinearity in the regression equations suggested that there were no associative effects.