Winter as a nutritional bottleneck for North American porcupines (Erethizon dorsatum)

North American porcupines are distributed across a wide variety of habitats where they consume many different species of plants. Winter is a nutritional bottleneck for northern populations, because porcupines remain active when environmental demands are high and food quality is low. We used captive porcupines to examine physiological responses to low-quality diets at high energy demands during winter at ambient temperatures as low as −39°C. We did not observe an endogenous pattern of body mass gain or loss when porcupines were fed a low nitrogen diet (1.1% dry matter) ad libitum through winter. Dry matter intake declined from 43.6 to 14.6 g kg^−0.75 d⁻¹ even though ambient temperatures declined from −3 to −30°C, which indicates a seasonal decrease in metabolic rate. Porcupines consuming white spruce needles maintained digestive efficiency for energy (61%) and neutral detergent fiber (NDF) (50%). However, low requirements for energy (398 kJ kg^−0.75 d⁻¹) and nitrogen (209 mg kg^−0.75 d⁻¹) minimized the loss of body mass when intakes were low and plant toxins increased urinary losses of energy and nitrogen. Porcupines were also able to tolerate low intakes of sodium, even when dietary potassium loads were high. Porcupines use a flexible strategy to survive winter: low requirements are combined with a high tolerance for dietary imbalances that minimize the use of body stores when demands exceed supply. However, body stores are rapidly restored when conditions allow. Porcupines posses many physiological abilities similar to specialist herbivores, but retain the ability of a generalist to survive extreme conditions by using a variety of foods.     

Effects of Acomastylis rossii tannins on a mammalian herbivore,the North American pika,Ochotona princeps

 I investigated the effects of tannin consumption, using plant tannins naturally occurring in the diet, on a herbivorous mammal, the North American pika, Ochotona princeps. The objectives were to determine if a high-tannin diet influenced protein and dry matter apparent digestibility, fiber digestibility and production of detoxification by-products. Additionally, I examined the possibility that pikas produce salivary tannin-binding proteins, a potential mechanism for avoiding detrimental effects of tannins. My results demonstrate that although pikas constitutively produce salivary tannin-binding proteins, animals consuming a high-tannin diet of Acomastylis rossii exhibited lower dry matter, protein and fiber digestion and excreted higher concentrations of detoxification by-products. Thus, A. rossii tannins are potential toxins as well as digestibility reducers. I propose a hypothesis coupling detoxification to reduced fiber digestion that is applicable to pikas as well as other mammalian herbivores consuming phenolic-rich diets. Received: 31 July 1995 / Accepted: 9 July 1996     

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     

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.     

The influence of natural diet composition, food intake level, and body size on ingesta passage in primates

An important component of digestive physiology involves ingesta mean retention time (MRT), which describes the time available for digestion. At least three different variables have been proposed to influence MRT in herbivorous mammals: body mass, diet type, and food intake (dry matter intake, DMI). To investigate which of these parameters influences MRT in primates, we collated data for 19 species from trials where both MRT and DMI were measured in captivity, and acquired data on the composition of the natural diet from the literature. We ran comparative tests using both raw species values and phylogenetically independent contrasts. MRT was not significantly associated with body mass, but there was a significant correlation between MRT and relative DMI (rDMI, g/kg(0.75)/d). MRT was also significantly correlated with diet type indices. Thus, both rDMI and diet type were better predictors of MRT than body mass. The rDMI-MRT relationship suggests that primate digestive differentiation occurs along a continuum between an "efficiency" (low intake, long MRT, high fiber digestibility) and an "intake" (high intake, short MRT, low fiber digestibility) strategy. Whereas simple-stomached (hindgut fermenting) species can be found along the whole continuum, foregut fermenters appear limited to the "efficiency" approach.     

Protein requirements of subadult nilgai antelope

1. The maintenance crude protein (CP) requirements of subadult nilgai antelope (Boselaphus tragocamelus) were determined by nitrogen balance. Four isocaloric pelleted diets, ranging from 8.4 to 23.8% CP, were fed. 2. Subadults maintained a positive nitrogen balance on all diets. Linear regression showed that 95.8% of diet CP was truly digested and estimated metabolic fecal nitrogen (NFN) excretion at 0.388 gN/W0.75/day. 3. Estimates for endogenous urinary nitrogen excretion and maintenance nitrogen requirement, derived through linear regression, were erroneous. Consequently, the former was calculated based on metabolic size (0.126 gN/W0.75/day) and added to MFN to obtain an 0.514 gN/W0.75/day estimate of required nitrogen for maintenance. This value is between the levels recommended for maintenance of yearling deer and cattle. 4. Given the same level of dry matter intake (68.6 g/W0.75/day) and true CP digestibility, study animals would be able to meet N equilibrium on a 4.89% CP (dry matter basis) diet. 5. Based on data from other sources, natural diets containing 6.98% CP would need to be consumed by free-ranging subadults to maintain body weight.     

Limits to food intake and fiber utilization in the prairie vole,Microtus ochrogaster: effects of food quality and energy need

We fed prairie voles (Microtus ochrogaster) rat chow diluted with variable amounts of -cellulose to determine 1) how much fiber the voles could tolerate in their diet; 2) changes in food intake and digestibility of dry matter and of fiber; 3) the extent to which voles utilized fiber as an energy source; and 4) whether any of these variables differed between groups of animals maintained at 5 or 22°C. Fiber content of the diets ranged from 20 to 84%. Animals held at 5°C maintained body mass through a diet containing 69% fiber, while animals held at 22°C maintained body mass through the 84% fiber diet. Dry matter intake increased with fiber level from 9.3 to 15.0 g·day^-1 for animals at 5°C and from 5.6 to 14.0 g·day^-1 for animals at 22°C; intake on the highest fiber diet eaten by either group was not different. Dry matter digestibility decreased significantly as the fiber in the diets increased, but was not affected by temperature treatments. Digestible dry matter intake for each group remained constant regardless of diet quality, but on each diet digestible dry matter intake for animals at 5°C was significantly higher than that of the animals held at 22°C. Digestibility of the fiber portion of the experimental diets remained constant as food quality decreased, so the percent of daily energy need met by fiber utilization increased with higher food intake. On the lowest quality diet each group tolerated, fiber digestion provided approximately 42 and 68% of the energy needs of voles at 5 and 22°C, respectively.Abbreviations BM body mass - BMR basal metabolic rate - DE digestible energy - DM dry matter - DMD dry matter digestibility - DDMI digestible dry matter intake - MR metabolic rate - NDF neutral detergent fiber (=cell walls) - NDS neutral detergent solubles (=cell solubles) - SEM standard error of mean - T _a ambient temperature     

Comparative effects of feeding citrus pulp and grape pomace on nutrient digestibility and utilization in steers

Feedlot beef production in tropics and subtropics is being limited by shortage of feed ingredients due to prolonged droughts resulting in high prices of cereal grains and reduced profitability. To alleviate feed shortages and increase profitability for the feedlot industry, it is important to explore underutilized non-conventional resources such as fruit by-products. The current study compared the nutrient intake, digestibility and utilization effects of feeding either 150 g/kg of dried citrus pulp (DCP) or grape pomace (DGP) as alternative dietary fibre sources to 7 months-old Angus steers (281 ± 15.7 kg) under feedlot conditions. Twenty-four steers were assigned to three dietary treatments (8 steers/treatment) in a completely randomised design. Each steer was treated as an experimental unit. Steers were adapted to diets for 21 d followed by 7 d of sample collection during which nutrient intake, digestibility, rumen fermentation parameters, nitrogen retention and microbial N supply were determined. All the data were analysed using the GLIMMIX procedures. Overall, steers fed DGP had the greatest dry matter intake (DM), organic matter (OM) crude protein (CP), ash free neutral detergent fibre (aNDFom), ether extract (EE) and starch intake followed by DCP and control (CON) diets (P ≤ .05). Apparent digestibilities of DM, OM and aNDFom were higher (P ≤ .05) for DCP diet compared to DGP and CON diets. Feeding DCP and DGP diets increased ruminal concentrations of total volatile fatty acids, acetate and isovalerate, and acetate to propionate ratio, and reduced propionate concentrations compared to the CON diet (P ≤ .05). The steers fed the CON diet had the greatest urinary excretions of allantoin, uric acid and total purine derivatives followed by those fed the DCP and DGP diets (P ≤ .05). Nitrogen intake, faecal nitrogen (N), N retention and N efficiency utilization were in the order of DGP > DCP > CON diets (P ≤ .05). Overall, feeding DGP as alternative fibre source to wheat bran improved nutrient intake, retention and efficiency of N utilization but reduced apparent nutrient digestibility compared to DCP. Current finding suggests that DGP may be a better fibre substitute for wheat bran in beef diets than DCP.     

Effects of lowering crude protein supply alone or in a combination with essential oils on productivity,rumen function and nutrient utilization in dairy cows

Lowering dietary protein concentration is known to decrease urinary nitrogen (N) losses and increase milk N efficiency in dairy cows, but it may negatively affect animal productivity. Plant-derived essential oils (EO) may alleviate these negative effects by improving the efficiency of rumen fermentation in cows fed reduced feed protein diets. The experiment was conducted to investigate the effects of lowering crude protein (CP) supply alone or in a combination with an EO product on feed intake, milk production and composition, rumen fermentation, total tract digestibility and N utilization in dairy cows. Twenty-one Holstein cows were used in a replicated 3 × 3 Latin square design experiment. Each period consisted of 14 days for adaptation and 14 days for data collection and sampling. Cows were randomly assigned to one of three experimental diets: a 165 g/kg CP diet (control), a 155 g/kg CP diet (LCP) and LCP supplemented with 35 g/day per cow EO (LCPEO). The dry matter (DM) intake was decreased by LCP and LCPEO compared with the control; there was no effect of EO on DM intake. Milk yield and composition and feed efficiency were similar among treatments. Ruminal pH, lactate, ammonia and volatile fatty acids concentrations were not affected by treatment, except increased valerate concentration by LCPEO compared with LCP. The supplementation of EO tended to decrease protozoal counts. The LCP and LCPEO increased total tract digestibility of DM and organic matter and decreased CP digestibility compared with the control. Supplementation with EO did not affect total tract digestibility of dietary nutrients compared with the control or LCP. The LCP and LCPEO decreased urinary and fecal N excretions and increased milk N efficiency; nitrogen losses were not affected by EO. In this study, lowering dietary CP by 10 g/kg decreased urinary and fecal N excretion without affecting productivity. The supplementation of EO to LCP had only minor effects on rumen fermentation and did not affect productivity, digestibility and N excretion in lactating dairy cows.     

Effect of tree leaves with or without urea as a feed supplement on nutrient digestion and nitrogen balance in sheep

Two nitrogen balance experiments in a 4 × 4 Latin square design were conducted to compare leaves of Grewia oppositifolia and Ziziphus mauritiana containing condensed tannins (CT) 0.08 g and 34.7 g per kg DM, respectively as supplement on feed intake, nutrients digestibility and nitrogen (N) retention in adult wethers and to examine the benefits of adding urea to Z. mauritiana leaves containing higher level of CT on N utilization in the animals. In experiment 1, the basal diet of oat hay was fed to sheep either un-supplemented or supplemented with 320 g dried leaves of Z. mauritiana or 320 g dried leaves of G. oppositifolia or 160 g dried leaves each of Z. mauritiana and G. oppositifolia. In vivo dry matter (DM) digestibility was not different among the four diets while N digestibility remained significantly lower (P<0.05) in Z. mauritiana supplemented diets. Daily intake of oat hay reduced (P<0.05) and that of total diet DM increased (P<0.001) with feeding of the leave supplements. Mean N retention on control diet was 4.39 g/d and increased to 7.51 g/d with inclusion of G. oppositifolia leaves but did not change with the other two supplements. In experiment 2, a basal diet of sorghum hay was fed ad libitum without any supplement (control diet) and the other three diets were supplemented with 320 g dried leaves of Z. mauritiana with no urea, 5 g urea/d or 10 g urea/d. Daily intake (g/d) of sorghum hay or total DM intake did not respond to inclusion of urea in the diets. Supplementation of Z. mauritiana with or without urea did not affect digestibility of DM, organic matter and acid detergent fiber. Nitrogen retention increased (P<0.05) from 0.57 g/d on control diet to 3.72 g/d with supplementation of Z. mauritiana leaves. Addition of urea 5 g/d did not further increase the N retention (4.78 g/d) but was significantly increased to 7.16 g/d in response to 10 g urea/d in the diet. It was concluded that response to urea feeding in the presence of tannin rich Z. mauritiana leaves was dose-dependant and that feeding 10 g urea/d increased the capacity of sheep to consume more feed and retain more N in the body.     

The intake and digestion of a range of temperate forages by sheep and fibre-producing goats

The voluntary intake, digestibility and mean retention time of six temperate forages differing in their chemical composition by 12 adult castrated male Scottish blackface sheep, aged 15 months, and fibre-producing castrated male goats, aged 27 months, and of similar live weight, 40 kg, were described. The creation of a range of chemical compositions was effected through the use of barley straw, and a low- and high-digestibility hay, and the use of ammonia treatment of these forages. A wide range of voluntary intakes (42–78 g DM/kg W^0.75/day), digestibility of dry matter (0.46–0.60) and mean retention times of undigested residues (36–72 h) was achieved through feeding the six forages. Across all the forages fibre-producing goats had higher voluntary intakes, expressed on a metabolic live weight basis, and lower digestibility values than sheep, whereas the mean retention time of the undigested residues was similar for the two species. Within forages goats selected a diet of potentially higher nutritive value, as predicted from chemical composition, with a smaller particle size than sheep. It was concluded that the differences in intake and digestion of temperate forages between sheep and fibre-producing goats are broadly similar to those observed in other experiments between sheep and goats ingesting tropical forages.     

Effects of defaunation on digestion of fresh Digitaria decumbens grass and growth of lambs

The effects of defaunation on growth and digestion were measured in sheep fed fresh Digitaria decumbens grass cut at four stages of regrowth 14, 28, 42, and 56 days, and with different protein to energy (P/E) ratios. Two completely randomized designs trials (growth and digestion) were conducted using faunated animals, defaunated rams and protozoa free lambs. The digestion trial: eight faunated and eight defaunated rams fitted with ruminal and duodenal cannulas were fed 4 diets (diets D1 to D4) to measure digestion parameters. The dietary P/E ratios were 120 (D1), 130 (D2), 130 (D3), and 140 (D4) g PDIN/UFL (Protein Digested in the small Intestine supplied by microbial protein from rumen-degraded protein/Feed Unit for Lactation) and the grass stages of regrowth were 56, 42, 28, and 14 days, respectively. Increasing the dietary P/E ratios increased dry matter intake (DMI) and the total tract digestibility of organic matter (OM), NDF and CP. Defaunation decreased DMI, except for rams fed D4 diet. Defaunation also decreased total tract digestibility of OM except for rams fed D1 diet and that of NDF except for rams fed D1 and D4 diets. Increasing the dietary P/E ratios also increased nitrogen intake and ammonia (NH3) concentration in the rumen, whereas defaunation decreased them. The dietary P/E ratio increased non-NH3 nitrogen and microbial nitrogen duodenal flows and microbial efficiency. Defaunation did not affect duodenal flows of neither non-NH3 nitrogen and microbial nitrogen or microbial efficiency. The growth trial: 20 faunated and 20 protozoa free lambs were fed four diets (diets D5 to D8) to measure their average daily gain (ADG). The dietary P/E ratios were 60 (D5), 70 (D6), 80 (D7) and 100 (D8) g PDIN/UFL and the stages of regrowth were 56, 42, 28, and 14 days, respectively. DMI of lambs increased with P/E ratio. Protozoa free lambs had greater DMI than faunated ones when fed D7 diet (80.8 v. 74.9 g/kg LW0.75, respectively). The ADG of the lambs increased with P/E ratio. Fed on the same D5 diet, protozoa free lambs had greater ADG than faunated lambs (29.8 v. 11.6 g/day, respectively). In conclusion, animal response to defaunation was modulated by the P/E ratio of the D. decumbens grass diets. Defaunation increased ADG of lambs fed forage with the lowest P/E ratio, while digestion and nitrogen duodenal flows of rams fed the lowest P/E ratio were not affected.     

Supplementation with non-fibrous carbohydrates reduced fiber digestibility and did not improve microbial protein synthesis in sheep fed fresh forage of two nutritive values

To determine whether non-fibrous carbohydrate (NFC) supplementation improves fiber digestibility and microbial protein synthesis, 18 Corriedale ewes with a fixed intake level (40 g dry matter (DM)/kg BW0.75) were assigned to three (n = 6) diets: F = 100% fresh temperate forage, FG = 70% forage + 30% barley grain and FGM = 70% forage + 15% barley grain + 15% molasses-based product (MBP, Kalori 3000). Two experimental periods were carried out, with late (P1) and early (P2) vegetative stage forage. For P2, ewes were fitted with ruminal catheters. Forage was distributed at 0900 h, 1300 h, 1800 h and 2300 h, and supplement added at 0900 h and 1800 h meals. Digestibility of the different components of the diets, retained N and rumen microbial protein synthesis were determined. At the end of P2, ruminal pH and N-NH3 concentration were determined hourly for 24 h. Supplementation increased digestibility of DM (P < 0.001) and organic matter (OM; P < 0.001) and reduced NDF digestibility (P = 0.043) in both periods, with greater values in P2 (P = 0.008) for the three diets. Daily mean ruminal pH differed (P < 0.05) among treatments: 6.33 (F), 6.15 (FG) and 6.51 (FGM). The high pH in FGM was attributed to Ca(OH)2 in MBP. Therefore, the decreased fiber digestibility in supplemented diets could not be attributed to pH changes. The mean ruminal concentration of N-NH3 was 18.0 mg/dl, without differences among treatments or sampling hours. Microbial protein synthesis was greater in P2 (8.0 g/day) than in P1 (6.1 g/day; P = 0.006), but treatments did not enhance this parameter. The efficiency of protein synthesis tended to be lower in supplemented groups (16.4, 13.9 and 13.4 in P1, and 20.8, 16.7 and 16.2 g N/kg digestible OM ingested in P2, for F, FG and FGM, respectively; P = 0.07) without differences between supplements. The same tendency was observed for retained N: 2.55, 1.38 and 1.98 in P1, and 2.28, 1.23 and 1.10 g/day in P2, for F, FG and FGM, respectively; P = 0.05). The efficiency of microbial protein synthesis was greater in P2 (P = 0.007). In conclusion, addition of feeds containing NFCs to fresh temperate forage reduced the digestibility of cell walls and did not improve microbial protein synthesis or its efficiency. An increase in these parameters was associated to the early phenological stage of the forage.     

The intake and digestion of maize silage-based diets by dairy cows and sheep

Six lactating cows, 6 dry cows and 6 wether sheep were fed ad libitum on diets of maize silage, maize silage plus lucerne, or maize silage plus lucerne plus wheat. Faeces and urine collections allowed for the determination of digestibility of dry matter, organic matter and nitrogen, and balances of nitrogen and water.

Voluntary feed intakes were highest and digestibility values were lowest in lactating cows. The addition of lucerne reduced organic matter digestibility in dry cows, but not in lactating cows or sheep. The addition of wheat decreased intake in dry cows and sheep, but not in lactating cows. Production of milk, protein, solids-not-fat and total solids increased with dietary quality, but there was a depression in milk fat content as a result of wheat supplementation.

The ranking of the 3 diets on the basis of feed intake differed with each class of livestock, but lactating cows and sheep gave the same ranking on the basis of organic matter digestibility.     

Effect of bean (Vicia faba) extrusion on nitrogen and starch intestinal flux in lactating cows]

Four mature lactating Holstein cows fitted with permanent ruminal, duodenal and ileal cannulae were used to study the effect of extrusion at 195 degrees C of beans (Vicia faba cv Castel) on organic matter (OM), nitrogen (N) and starch degradation in the rumen and their flow to and absorption from the small intestine. The test protein sources, raw beans (RB) and extruded beans (EB), provided about 45% of the dietary protein. The diets were composed of 23.1% beans, 56.2% corn silage, 10.1% corn grain and 10.7% Italian rye-grass hay on a DM basis; the diets were isocaloric (4.5 Mcal/kg of DM) and isonitrogenous (14% of DM). Cr-EDTA, YbCl3 and purines were used as liquid, particulate and bacterial markers respectively. Extruding the beans did not influence intraruminal pH (6.6), ammonia-N (99 mg/l) and volatile fatty acids (97 mM/l) concentrations. Apparent digestibility in total tract of energy, OM, N and starch were not affected with inclusion of EB instead of RB, the corresponding mean values were: 66, 68, 64 and 95% of intake. Apparent ruminal digestion of OM, starch and N in the forestomach were 39, 58 and 52% for diets containing RB and 38, 72 and 45% for EB diets; efficiency of bacterial protein synthesis (gN/kg organic matter truly digested in the stomach) was higher for EN diets compared with RN diets (25 vs 22). Eating diets including EB increased non-ammonia-N, bacterial-N and dietary-N flows (g/d) to the duodenum compared with diets containing RB: 409 vs 366, 216 vs 194 and 193 vs 172 respectively; while starch flow was reduced (1.5 vs 2.2 kg/d) and OM flow was unchanged (9.8 kg/d). Apparent digestion from the small intestine (g/d) of nonammonia-N, bacterial-N and dietary-N were higher for EB diets: 268 vs 229, 181 vs 160 and 87 vs 69 respectively; meanwhile, starch digestion decreased (975 vs 1,612). The PDIA, PDIN and PDIE contents (g/kg of DM) of the RB were 33, 175 and 127 respectively; the corresponding values after extrusion were: 58, 147 and 178.     

A comparative study of the effect of two-stage olive cake added to alfalfa on digestion and nitrogen losses in sheep and goats

This work was conducted to evaluate the effect of tannins, contained in a by-product derived from olive oil extraction (two-stage olive cake), on nutrient digestibility, nitrogen (N) losses and liver and kidney functions in goats and wethers. Six Segureña wethers and six Granadina goats were fed three experimental diets: alfalfa hay (AH); alfalfa hay and a concentrate (formulated with two-stage olive cake, barley and a mineral-vitamin mixture) without (AHCO) or with polyethylene glycol (PEG) addition (AHCOP). The inclusion of two-stage olive cake increased condensed tannins content of the diet and led to a decrease ( P < 0.001) in dry matter, organic matter, neutral-detergent fibre, acid-detergent fibre and crude protein (CP) digestibility. PEG supply increased ( P < 0.001) CP digestibility and N losses in urine and faeces only in wethers. Concentrations of creatinine and alkaline phosphatase activity, measured in the serum of animals, were not modified either by olive cake inclusion or by PEG supply. Results from this work indicate a higher sensitivity of sheep to diets containing condensed tannins, compared with goats, and reveal no toxic effect of tannins from two-stage olive cake at the concentration used in the experimental diets.     

Intake and digestibility in sheep fed on alkali-treated straw and concentrates,as complete diets or separate feeds

Twelve mature wethers were used in an experiment of change-over design to determine the effect of complete diet feeding on intake and digestibility of diets based on alkalitreated straw and a concentrate containing rolled barley and extracted soya bean meal. Two diets were used: D₁ with a 50:50, and D₂ with a 75:25 ratio of straw:concentrates on a dry matter basis. The straw and concentrates of each diet were given either separately (S) or as a complete diet (C). Complete diets gave a slightly, but not significantly higher intake (C, 86.5) and S, 82.5 g dry matter /kg W^0.75 per day). The separate method gave a significantly higher digestibility coefficient for dry matter (C, 62.2 and S, 65.5; P < 0.05) and for crude fibre (C, 57.2 and S, 62.5; P < 0.01). Water intake increased by 42.7 ml g^?1 Na derived from NaOH. There were no significant interactions between the method of feeding and the type of diet in intake and digestibility of the diets or in the intake of water.     

Responses of pocket gophers (Thomomys bottae) to changes in diet quality

Summary We examined digestibility of dry matter, nutrients, and fiber, and food intake, metabolic fecal losses, weight change, and gut size of pocket gophers (Thomomys bottae) in relation to diet quality in the laboratory. Pocket gophers were maintained for 15–20 days on one of seven diets which contained from 18% to 56% neutral detergent fiber (NDF). NDF content of the diet was an excellent predictor of diet quality. Digestibility of dry matter, NDF, and nitrogen all decreased with increasing NDF content of the diet. In general, pocket gophers compensated for low diet quality by increasing dry matter intake, but those given high quality forage before the lowest quality diet reduced their intake. Thus, the response of pocket gophers to low quality diets may depend on their body condition. Because increased food intake resulted in increased total metabolic fecal losses and metabolic fecal nitrogen losses, decreasing food intake on low-quality diets may be advantageous. A further response of pocket gophers to decreased food quality was an increase in size of cecum and large intestine, suggesting that fermentation of cell walls became increasingly important as diet quality decreased.     

UV-B effects on the nutritional chemistry of plants and the responses of a mammalian herbivore

Stratospheric ozone depletion has caused ground-level ultraviolet-B (UV-B) radiation to rise in temperate latitudes of both hemispheres. Because the effects of enhanced UV-B radiation on the nutrition of food consumed by mammalian herbivores are unknown, we measured nutritional and chemical constituents of 18 forages and related changes to in vitro dry matter digestibility. We also measured intake and in vivo digestibility of Pacific willow (Salix lasiandra) and alfalfa (Medicago sativa L.) by blue duikers (Cephalophus monticola). Forages were irradiated for 3 months with ambient (1×) or supplemental (1.6×) UV-B radiation representing a 15% ozone depletion for Pullman, Washington, USA. Enhanced UV-B radiation had minimal and inconsistent effects on the nutritional content, in vitro dry matter digestibility, and protein-binding capacity of forages. However, flavonoid compounds increased in seven of the 13 forbs and woody dicots that were evaluated. Flavonoids were found to decrease only in yarrow (Achillea millefolium). When offered simultaneously, blue duikers preferred 1× and 1.6× UV-B irradiated plants of alfalfa equally, but ate 26% less willow grown under 1.6× UV-B radiation. However, when fed to duikers in separate feeding experiments, total dry matter intake and in vivo digestibility of dry matter, fiber, protein, and apparent energy did not differ between alfalfa and willow grown under 1× and 1.6× UV-B radiation. We conclude that expected increases in UV-B radiation from ozone depletion would have minimal effects on intake and digestion of ruminant herbivores.     

Supplementing high-quality fresh forage to growing lambs fed a total mixed ration diet led to higher intake without altering nutrient utilization

The effect of supplementing high-quality fresh forage, mainly based on alfalfa, to growing lambs fed with decreasing levels of total mixed ration (TMR) was studied on intake, digestion and ruminal environment. In total, 24 catheterized lambs (25.2±3.67 kg) housed in individual metabolism cages were assigned to one of four treatment diets: ‘TMR100’: TMR offered ad libitum; ‘TMR75’ and ‘TMR50’: TMR at a level of 0.75 and 0.50 of potential intake, respectively, complemented with fresh forage without restriction; ‘TMR0’: only fresh forage ad libitum. The feeding behavior, nutrient intake and digestibility, kinetics of passage and rumen environment were evaluated. As the level of TMR in the diet decreased, lambs increased the forage intake and spent more time eating and ruminating, less time resting and demonstrated a higher rate of intake. Those changes resulted in a higher nutrient intake of dry matter, organic matter, nitrogen, NDF and ADF, but a slightly lower organic matter digestibility, while no differences were detected in the output rate of particles. As a consequence, with the decrease of TMR and increase of forage intake, the ingested energy increased. Higher ruminal pH and NH₃–N concentrations were observed for lower levels of TMR in the diet. The total volatile fatty acids, acetate and propionate concentrations presented a quadratic response. Total volatile fatty acids and acetate concentrations were higher and propionate concentration was lower in lambs consuming mixed diets (TMR50 and TMR75). We concluded that the inclusion of high-quality fresh forage in a combined diet with TMR in lambs had positive effects on nutrient intake without negative consequences on digestion and rumen environment.