Effect of partial replacement of oats with sugar beet pulp and maize oil on nutrient utilisation in horses.

The objective of the present work was to assess the influence of partial replacement of oats with dried unmolassed sugar beet pulp (SBP) and/or maize oil on nutrient utilisation in horses fed a traditional hay and concentrate diet. The total tract digestibility of nutrients, urinary excretion and plasma parameters were studied in a 4 x 4 Latin-square design experiment with purebred Arabian geldings. Horses fed the SBP diets responded with a reduced (P<0.05) apparent digestibility of crude protein and feeding of maize oil resulted in an increased (P<0.05) apparent digestibility of crude fat. The apparent energy digestibility was unaffected by the replacement of oats with SBP, but increased (P<0.05) when maize oil replaced part of the oats. The urinary excretion of nitrogen increased (P<0.05) when maize oil replaced oats and the excretion of energy was higher (P<0.05) on the diets where oats were replaced by maize oil and SBP. There was a significant (P<0.05) effect across treatments of postprandial blood sampling time on plasma glucose and insulin concentrations. Also, plasma concentrations of glucose and insulin tended to be higher on the oats than on the SBP diets. In conclusion, the limited effects on the digestibility of nutrients and energy suggest that it should be possible to partially replace oats with maize oil and/or SBP in diets for horses without any impairing effects on the overall nutrient utilisation. However, the dietary-induced changes in the urinary excretion of energy and on plasma glucose and insulin levels, indicate a possible influence of dietary carbohydrate composition on nutrient utilisation at the organ level, which requires further study.     

Dietary lactulose decreases apparent nitrogen absorption and increases apparent calcium and magnesium absorption in healthy dogs

To study the effect of lactulose on the route of nitrogen excretion, we fed six healthy, adult dogs on diets containing either 0, 1 or 3 g lactulose/MJ metabolizable energy according to a 3 × 3 Latin square design. The results were analysed to identify statistically significant linear trend effects of lactulose. Faecal pH was significantly lowered by lactulose. Faecal ammonium and nitrogen excretion tended to be raised by lactulose feeding whereas urinary urea excretion was significantly reduced. Lactulose feeding significantly lowered apparent nitrogen digestibility. It is concluded that lactulose feeding shifts nitrogen excretion from urine to faeces in dogs which may be beneficial for liver patients. The data are in line with the concept that lactulose stimulates bacterial growth in the colon which in turn enhances faecal nitrogen excretion and lowers the entry of colonic ammonia into the bloodstream, leading to a lesser workload for the liver and less urinary nitrogen excretion. Lactulose consumption was also found to produce a dose-dependent increase in the apparent absorption of calcium and magnesium, but not phosphorus.     

Faecal bacterial profile,nitrogen excretion and mineral absorption in healthy dogs fed supplemental oligofructose

In a cross-over trial, five healthy dogs were fed a dry food without or with 1% (w/w) oligofructose to assess any oligofructose-induced effects on the faecal bacterial profile, nitrogen excretion and mineral absorption. The diets were given for a period of 3 weeks. Oligofructose feeding significantly raised the number of Bifidobacteria, Streptococci and Clostridia in faeces. The numbers of faecal anaerobic and aerobic bacteria were raised after ingestion of oligofructose. The faecal pH was unchanged. There was no effect of oligofructose feeding on the route of nitrogen excretion which was associated with a lack of effect on faecal ammonium and urinary urea excretion. It is suggested that the absence or presence of an effect of oligofructose on urinary and faecal nitrogen excretion depends on the background composition of the diet, in particular the content of non-digestible, fermentable carbohydrates. In the diets used, the content of non-digestible, fermentable carbohydrates was not measured. Both apparent magnesium and calcium absorption were significantly raised by oligofructose feeding, but phosphorus absorption was unaffected. The data presented may contribute to the qualification of the use of oligofructose in dog foods.     

Effect of type of starch and quantity in rations on apparent and true digestibility of nitrogen and nitrogen balance in sheep

In a digestibility trial 5 semisynthetic rations were fed in 3 periods to 10 male sheep to examine the effects on N balance, components of faecal nitrogen and N digestibility. The rations contained constant amounts of nitrogen but different contents of cellulose and two different types of starch (untreated and steamflaked). Content and type of starch did not show any noticeable effect neither on excretion of undigested dietary nitrogen nor on true digestibility. There could not be noticed any effects on the apparent N digestibility by changing contents of cellulose or untreated starch. If the rations contained steamflaked corn starch, the animals excreted more faecal nitrogen and therefore showed a lower apparent N digestibility. Especially the water soluble N fraction of the faecal nitrogen was clearly higher. Compensation took place through a lower N excretion with the urine. The reason for increased faecal N excretion may be higher microbial protein synthesis in the rumen. This was accented by the allantoin excretion with the urine.     

Effects of dietary carbohydrates and buffering capacity on nutrient digestibility and manure characteristics in finishing pigs

A 2 x 3 factorial experiment was conducted with 24 finishing pigs (Yorkshire x [Finnish Landrace x Dutch Landrace]) to determine the effects of dietary buffering capacity (BC) and carbohydrate sources on apparent total tract digestibility (TD), N retention, and manure characteristics. Twelve of these pigs were fitted with steered ileo-cecal value cannulas to measure the apparent ileal digestibility (ID) of N. Experimental variables were two levels of BC (High = 600 mEq/kg and Low = 530 mEq/kg) and three dietary carbohydrates (tapioca [28%], soybean hulls [25%], and sugar beet pulp [25%]). The two levels of BC were achieved by adjusting the amounts of alkalogenic limestone and acidogenic Ca sulfate in the diet. Pigs were fed twice daily at 2.4 x maintenance requirement for metabolizable energy (418 kJ ME/BW(0.75)). Chromic oxide was used as an indigestible marker. Feces and urine were collected over 5 d for nutrient balance and in vitro measurements of pH and ammonia emission over 7 d. No significant interactions between BC and dietary carbohydrates on the ID, TD, N retention, or manure characteristics were observed. Lowering BC with Ca sulfate did not affect digestibility of most nutrients, except for a negative impact on the TD of Ca (P = 0.015) and Mg (P = 0.003). Although all pigs receiving Ca sulfate had more acidic urine (by 0.49 pH units; P = 0.001), ammonia emission from manure was not lowered, irrespective of the carbohydrate source. Carbohydrates affected significantly the ID and TD of most nutrients, whereas N retention remained similar (P > 0.10). Urinary N:fecal N ratios in manure of pigs fed diets with tapioca, soybean hulls, and beet pulp were 2.09, 1.35, and 1.67, respectively. These ratios corresponded with in vitro ammonia emission (169, 125, and 148 mmol/7 d; P = 0.023). In conclusion, these results indicate that the acidification of urine in pigs fed Ca sulfate in the presence of NSP-rich carbohydrates was achieved. However, acidity of manure and ammonia emission were not affected. The addition of NSP from soybean hulls and(or) sugar beet pulp reduced ratios of urinary:fecal N, and thereby ammonia emission.     

Demonstration of uniformity of calcium absorption in adult dogs and cats

A meta‐analysis was conducted to understand quantitative aspects of calcium (Ca) and phosphorus (P) absorption in adult dogs and cats. 34 studies in dogs and 14 studies in cats met the criteria for inclusion in the meta‐analysis. Intake and faecal excretion values of Ca and P were subjected to a modified Lucas test and subsequent regression analyses. According to the current scientific consensus, Ca true digestibility (absorption) should increase at low Ca intake and decrease at high Ca intake. If true, this should result in a nonlinear relationship between the percentage of Ca excreted and dietary Ca intake. The present meta‐analysis showed a highly significant linear relationship (p < 0.0001) between Ca intake and Ca excretion suggesting a lack of systematic quantitative adaptation in true Ca digestibility. This finding suggests either that the time period covered by standard digestion trials is too short to induce adaptation mechanisms or that dogs and cats at maintenance will not efficiently alter quantitative Ca absorption percentage according to the amount ingested. If the latter is true, a dietary Ca supply differing greatly from the recommended dietary intake might impair the health of cats and dogs when fed long term. The data plots for P intake and faecal excretion were less uniform suggesting other factors not just dietary intake influence faecal P excretion. In adult cats, the dietary Ca:P ratio strongly influenced the true digestibility of P, whereas this effect was less marked in adult dogs. Faecal P excretion was significantly correlated to faecal Ca excretion in both species (p < 0.0001), and surprisingly, the level of P intake did not appear to be an important determinant of true digestibility of P.     

Feeding value of dried sugar beet pulp from Egyptian production.

Dried sugar beet pulp was fed to sheep in mixture with molasses (BPM), molasses plus urea (BPMU) or with hay (BPH) in comparison to whole diet of hay (H) in four metabolic trials. There were no significant differences among the four rations although BPMU reflected the highest digestibility of nutrients. The BPH had the highest feeding value (total digestible nutrients "TDN" and metabolizable energy) and caused the highest retention of nitrogen. Blood profile revealed that there were no significant effect of the rations on packed cell volume, haemoglobin, activity of glutamic pyruvic transaminase, Mg and Na. Whereas glucose, total N, Ca, P and K significantly affected. The BPMU and BPH were found to be the best mixtures of the four tested rations in respect to the digestibility, feeding value and blood picture. Thus, dried sugar beet pulp could be offered to animals in a mixture with molasses and urea or with hay according to the availability and price of the other ingredients than beet pulp, i.e. molasses and urea or hay.     

Effects of beet pulp supplementation on growth performance,fecal moisture,serum hormones and litter performance in lactating sows

This study was conducted to evaluate effects of beet pulp supplementation on growth performance, fecal moisture, serum hormones and litter performance in lactating sows. Ninety primiparous sows (Landrace × Yorkshire) were randomly allotted to one of three dietary treatments in a 21‐day trial starting 3 days before parturition. The three dietary treatments were supplemented with 0, 10 and 20% beet pulp, respectively. Backfat loss and fecal moisture content were increased (P < 0.05), where cortisol and norepinephrine levels were decreased (P < 0.05) in sows fed beet pulp supplementation diets compared with control diet, but there was no difference between 10% and 20% beet pulp supplementation treatments. No effect was observed on bodyweight, average daily intake, weaning to estrus interval, epinephrine level in sows and litter weight, litter size, survivability in piglets among dietary treatments. Taken together, beet pulp supplementation has no significant effect of growth performance of lactating sows and piglets with decreased cortisol and norepinephrine levels in lactating sows, but it can increase fecal moisture content which is beneficial for sow feces excretion.     

Effect of fructo‐oligosaccharide on nitrogen utilization in guinea pigs

The present study was conducted to determine the effects of fructo‐oligosaccharide (FOS) on the nitrogen (N) utilization and digestibilities of dietary nutrients through cecotrophy in guinea pigs. Adult male guinea pigs that were housed or not housed in wooden frames to prevent cecotrophy were fed a commercial pellet diet (50 g/day) with 3% and 5% glucose or FOS for 8 days in individual metabolism cages. In the guinea pigs allowed cecotrophy, addition of FOS to the diet had no significant effects on body weight gain or apparent digestibility of N, but showed significantly lower value for the urinary N excretion and acid‐detergent fiber digestibility (P < 0.05 and P < 0.01, respectively) and significantly higher value for N retention and the N retention rate (P < 0.05). In the guinea pigs prevented from cecotrophy, FOS had no effect on N retention, but showed tendencies toward a higher value for fecal N excretion and a lower value for urinary N excretion. These results suggest that FOS stimulates cecal microbial proliferation, thereby improving N utilization in guinea pigs.     

Metabolism of some essential minerals in ponies fed high levels of aluminum

The effect of dietary aluminum on the absorption, retention and pathways of excretion of calcium, phosphorus, magnesium, zinc, iron and copper was studied in balance trials in mature ponies in a three by three latin square experiment. A basal diet consisting of one third each of oats, beet pulp and a commercial pelleted, complete horse ration and containing 336 ppm aluminum was supplemented with AlC1(3) . 6H2O. The middle and high level aluminum diets contained 1370 and 4500 ppm aluminum respectively. There was little difference in effect between the middle level aluminum and basal diets. The ponies were in negative phosphorus balance when fed the high level aluminum diet because phosphorus absorption was suppressed. Calcium absorption was unaffected by aluminum intake but the ponies were in negative calcium balance when fed the high aluminum diet due to the greater urinary excretion of calcium by the ponies. Presumably, calcium was excreted in urine because it was not utilized in the formation of bone crystal due to the lack of phosphate. Plasma calcium was elevated and plasma phosphorus was depressed when ponies were fed the high aluminum diet. Plasma hydroxyproline concentration was increased suggesting that bone turnover was increased due to aluminum effects on phosphorus and calcium metabolism. Magnesium, zinc, iron and copper metabolism were unaffected by aluminum intake.     

Fiber fermentability effects on energy and macronutrient digestibility, fecal traits, postprandial metabolite responses, and colon histology of overweight cats

Considering the different potential benefits of divergent fiber ingredients, the effect of 3 fiber sources on energy and macronutrient digestibility, fermentation product formation, postprandial metabolite responses, and colon histology of overweight cats (Felis catus) fed kibble diets was compared. Twenty-four healthy adult cats were assigned in a complete randomized block design to 2 groups of 12 animals, and 3 animals from each group were fed 1 of 4 of the following kibble diets: control (CO; 11.5% dietary fiber), beet pulp (BP; 26% dietary fiber), wheat bran (WB; 24% dietary fiber), and sugarcane fiber (SF; 28% dietary fiber). Digestibility was measured by the total collection of feces. After 16 d of diet adaptation and an overnight period without food, blood glucose, cholesterol, and triglyceride postprandial responses were evaluated for 16 h after continued exposure to food. On d 20, colon biopsies of the cats were collected under general anesthesia. Fiber addition reduced food energy and nutrient digestibility. Of all the fiber sources, SF had the least dietary fiber digestibility (P < 0.05), causing the largest reduction of dietary energy digestibility (P < 0.05). The greater fermentability of BP resulted in reduced fecal DM and pH, greater fecal production [g/(cat × d); as-is], and greater fecal concentration of acetate, propionate, and lactate (P < 0.05). For most fecal variables, WB was intermediate between BP and SF, and SF was similar to the control diet except for an increased fecal DM and firmer feces production for the SF diet (P < 0.05). Postprandial evaluations indicated reduced mean glucose concentration and area under the glucose curve in cats fed the SF diet (P < 0.05). Colon mucosa thickness, crypt area, lamina propria area, goblet cell area, crypt mean size, and crypt in bifurcation did not vary among the diets. According to the fiber solubility and fermentation rates, fiber sources can induce different physiological responses in cats, reduce energy digestibility, and favor glucose metabolism (SF), or improve gut health (BP).     

Flavomycin effects on performance of beef bulls and nutrient digestibility in wethers

For 28 weeks a feeding experiment was conducted to determine the effects of dietary flavomycin on performance of beef bulls. In the first and second half of the trial, 40 animals (average initial weight 352 kg) had free access to corn silage or beet pulp, respectively, both supplemented with an appropriate concentrate containing 0 or 10 mg/kg of the antibiotic. Daily flavomycin intake was 39 to 46 mg when the animals were on the corn silage diet and 51 to 54 mg when they were fed the beet pulp diet. The animals fed the corn silage-based diet supplemented with flavomycin showed a non-significant improvement of daily gain (1.4%) and feed conversion (2.3%). When the beet pulp-based diet was fed, flavomycin significantly increased daily gain (15.2%, P less than 0.002) and feed conversion efficiency (9.1%, P less than 0.03). For the overall feeding experiment the positive effect of flavomycin feeding was 6.7% on body weight gain (P less than 0.09) and 5.2% on feed conversion (P less than 0.13). Flavomycin did not affect carcass yield of beef bulls. Also the effect of flavomycin on diet digestibility was studied in wethers fed a mixture of beet pulp and concentrate, containing 0 or 10 ppm flavomycin. No significant effect from the antibiotic on digestion of dry matter, crude protein, fibre, fat, ash and N-free extract was observed.     

Influence of sarsaponin on growth, feed and nitrogen utilization in growing male rats fed diets with added urea or protein

Two experiments were conducted with growing male rats to determine the effects of 120 ppm of dietary sarsaponin (S) on nitrogen (N) metabolism when urea or protein are added to the diet. Growth, feed efficiency, N digestibility and balance, urinary N and ammonia-N (NH3-N), and cecal urease and NH3-N were measured. Growth and feed utilization were unaffected by dietary S. Adding urea or protein to the diet increased apparent N digestibility and increased urinary-N excretion. Urea did not affect N balance, whereas growth, feed utilization and N balance were maximized with 22% compared with either 16 or 28% dietary protein. Urinary NH3-N excretion was decreased by S when urea was added to the diet but was not affected when fed with increasing dietary protein. Cecal urease was decreased by S when urea was added or when the protein level was increased in the diet; effects on cecal NH3-N varied between the two experiments. Plasma urea-N was decreased by S. It is concluded that S has minor effects on N metabolism in rats and that NH3-N formation or excretion is only marginally affected by dietary S. If S decreases NH3-N level in confinement facilities, it is concluded that the effect is after the waste material is excreted by the animal, perhaps through reduced urease activity.     

The pathophysiology of ovine fascioliasis: studies on the feed intake and digestibility, body weight and nitrogen balance of sheep given rations of hay or hay plus a pelleted supplement

The effect of Fasciola hepatica on feed intake and digestibility, body weight and nitrogen balance was measured during the course of experimental infections in sheep given a diet of hay or hay with 'concentrate'. A system of paired feeding was used to allow comparisons between infected and control animals. After the sixth week the appetites and body weights of all infected animals declined but both features were more prominent in the group given the diet of hay alone. By week 14 these animals became moribund and were necropsied whereas those given hay with concentrate which had the same fluke burdens, survived until week 20. At necropsy, the loss of weight in both groups was comparable but greater than in their pair-fed uninfected controls, suggesting that inappetence was not solely responsible. Measurements of feed digestibility revealed few differences between infected and control animals on either diet, but nitrogen retention was markedly lower in the infected animals after the eighth week, and sufficient to account for their inferior weight performance. Reduced nitrogen retention was primarily a reflection of a high urinary excretion in the infected animals, faecal excretion remaining unaltered despite the loss of substantial amounts of nitrogen into the gut as a result of the parasites' haematophagic activities.     

Milk production,nutrient digestibility and nitrogen balance in lactating cows fed total mixed ration silages containing steam‐flaked brown rice as substitute for steam‐flaked corn,and wet food by‐products

The objective of this study was to evaluate the effect of substituting brown rice grain for corn grain in total mixed ration (TMR) silage containing food by‐products on the milk production, whole‐tract nutrient digestibility and nitrogen balance in dairy cows. Six multiparous Holstein cows were used in a crossover design with two dietary treatments: a diet containing 30.9% steam‐flaked corn (corn TMR) or 30.9% steam‐flaked brown rice (rice TMR) with wet soybean curd residue and wet soy sauce cake. Dietary treatment did not affect the dry matter intake, milk yield and compositions in dairy cows. The dry matter and starch digestibility were higher, and the neutral detergent fiber digestibility was lower for rice TMR than for corn TMR. The urinary nitrogen (N) excretion as a proportion of the N intake was lower for rice TMR than for corn TMR with no dietary effect on N secretion in milk and fecal N excretion. These results indicated that the replacement of corn with brown rice in TMR silage relatively reduced urinary N loss without adverse effects on feed intake and milk production, when food by‐products such as soybean curd residue were included in the TMR silage as dietary crude protein sources.     

Effect of maize starch concentration in the diet on starch and cell wall digestion in the dairy cow

An in vivo experiment was performed to determine the effect of level of maize starch in the diet on digestion and site of digestion of organic matter, starch and neutral detergent fibre (NDF). In a repeated change‐over design experiment, three cows fitted with a rumen cannula and T‐piece cannulae in duodenum and ileum received a low‐starch (12% of ration dry matter) and a high‐starch (33% of ration dry matter) diet. Starch level was increased by exchanging dried sugar beet pulp by ground maize. After a 2‐week adaptation period, feed intake, rumen fermentation parameters (in vivo and in situ), intestinal flows, faecal excretion of organic matter, starch and NDF were estimated. When the high‐starch diet was fed, dry matter intake was higher (19.0 kg/day vs. 17.8 kg/day), and total tract digestibility of organic matter, starch and NDF was lower when the low‐starch diet was fed. Maize starch concentration had no significant effect on rumen pH and volatile fatty acid concentration nor on the site of digestion of organic matter and starch and rate of passage of ytterbium‐labelled forage. On the high‐starch diet, an extra 1.3 kg of maize starch was supplied at the duodenum in relation to the low‐starch diet, but only an extra 0.3 kg of starch was digested in the small intestine. Digestion of NDF was only apparent in the rumen and was lower on the high‐starch diet than on the low‐starch diet, mainly attributed to the reduction in sugar beet pulp in the high‐starch diet. It was concluded that without the correction for the reduction in NDF digestion in the rumen, the extra supply of glucogenic (glucose and propionic acid) and ketogenic nutrients (acetic and butyric acid) by supplemented starch will be overestimated. The mechanisms responsible for these effects need to be addressed in feed evaluation.     

Utilization of dietary urea nitrogen is stimulated by D‐mannitol feeding in rabbits

The effect of D‐mannitol as an indigestible sugar on apparent digestibility of nutrients, nitrogen (N) utilization and growth performance, have been investigated in growing rabbits fed a urea‐containing diet. In experiment 1, 40‐day‐old male rabbits were fed a commercial diet with urea 10 g/kg with added glucose or D‐mannitol 60 g/kg each. Thereafter, in experiment 2 the rabbits aged 55 days were fed a commercial diet with or without urea 10 g/kg. Feed restriction at 55 g/kg^0.75/day was carried out in both experiments. Addition of D‐mannitol to the urea‐containing diet decreased urinary N excretion, which consequently increased N retention and ratios of retained N to consumed N or apparently absorbed N. Addition of urea alone to the diet increased daily N intake and urinary N excretion but did not affect N retention. Weight gain and feed efficiency were improved by D‐mannitol feeding, whereas feeding with urea alone did not affect these parameters. Utilization of dietary urea was enhanced in growing rabbits fed the urea‐containing diet with D‐mannitol, resulting in improvement of N retention and growth performance.     

Cellulose fermentation capacity of the hindgut and nitrogen turnover in the hindgut of sows as evaluated by oral and intracecal supply of purified cellulose

Adult sows fed a constant amount of a basal diet received purified cellulose either orally at levels of 0 and 475 g/animal.d (Experiment 1) or intracecally at levels of 0, 285, 570 and 855 g/animal.d (Experiment 2). Each experiment consisted of subsequent periods of faeces and urine collection with the animals re-allocated to the treatments each time. With that, a total of 36 observations on each parameter was achieved. The faecal samples were analyzed for the contents of organic matter, cell wall carbohydrates and various nitrogen fractions such as bacterial N and undigested dietary N. Furthermore, N balance, urinary allantoin excretion and plasma urea concentrations were determined. In a preliminary study, the effects of freeze-drying and of shaking of the faecal samples as suspensions with water (in order to release bacteria from fibre) on content and composition of faecal nitrogen had turned out to be reproducible. Cellulose significantly enhanced faecal nitrogen loss whereas N retention was not affected due to the counteraction of urinary N loss. Plasma urea concentration reflected the situation with urinary N. The proportion of undigested dietary N and of water-soluble protein in total faecal N was somewhat increased by cellulose at cost of the bacterial N proportion which accounted for about 72% of total N on average. Urinary allantoin did not respond to the higher bacterial activity in the hindgut in the presence of supplementary cellulose. Cellulose significantly decreased the apparent N digestibility by on average about 3 percentage units per 100 g of supplementary cellulose. True N digestibility was also reduced by cellulose but did not go below 95%. The supplementary cellulose was fermented in the hindgut at similar rates of on average about 60% regardless of the route of administration. The almost 100 g of native cellulose incorporated in the basal diets were lignified by about 20%, and that is why they were fermented at a rate of only about 30%. The rate of fermentation was only slightly decreasing with increasing amounts of supplementary cellulose, and a daily quantity of 564 g (11 g/W0.75) cellulose was fermented on average if the highest level of cellulose was provided. This was within a range exclusively reported for easily-fermentable carbohydrates but was achieved in the case of cellulose only at a consistently higher level of supply. The true efficiency of bacterial protein synthesis was 5.2 g bacterial protein/100 g supplementary cellulose on average. The apparent efficiency was 60% higher averaging 8.4 g bacterial protein/100 g further apparently fermented organic matter.     

A comparative meta‐analysis on the relationship of faecal calcium and phosphorus excretion in mammals

To investigate the relationship between faecal calcium (Ca) and phosphorus (P) excretion in different mammalian species, a meta‐analysis on digestibility data derived from the literature was conducted. Seventy‐three studies on carnivores, omnivores, large and small hindgut fermenters, ruminants and hippos (a total of 21 mammalian species, precondition for inclusion dietary Ca/P ratio 1.5/1 – 3.0/1) were analysed for Ca and P digestibility. Dietary Ca/P ratios were lower than faecal Ca/P ratios in carnivores, omnivores, ruminants and hippos. In hindgut fermenters, dietary Ca/P ratios were higher than faecal Ca/P ratios, indicating higher intestinal Ca absorption in these species. In all species investigated, there was a significant positive relationship between Ca intake and faecal Ca excretion and between P intake and faecal P excretion. In the biologically relevant range, these equations predicted lower faecal Ca losses in hindgut fermenters than ruminants, for faecal P vice versa. In all species, faecal Ca and P excretion correlated significantly. In carnivores, this highly linear correlation was exceptionally strong (R² = .92). Yet, the linearity of the correlation was questionable in omnivores and ruminants. Possibly, the strong linear correlation of faecal Ca and P excretion in carnivores is due to the formation of insoluble Ca/P complexes in their relatively short and simple gastrointestinal tract. Another hypothesis is that in carnivores, Ca homeostasis relies on modifying bone turnover to a higher degree than on changes in intestinal Ca absorption. For the formation of bone matrix, a constant ratio of Ca and P absorption is of advantage.     

Nutrient digestibility in sheep fed diets containing Roundup Ready or conventional fodder beet, sugar beet, and beet pulp

The objective of this digestibility assessment was to determine whether there are significant differences in the digestibility of Roundup Ready (glyphosate-tolerant) and conventional sugar beet, fodder beet, and beet pulp produced from sugar beet varieties when fed to sheep (seven wethers per treatment group). Three experiments were conducted in this assessment. Experiment 1 (35 wethers) compared one glyphosate-tolerant fodder beet variety with four conventional varieties, Exp. 2 (42 wethers) compared one glyphosate-tolerant sugar beet variety with five conventional varieties, and Exp. 3 (42 wethers) compared beet pulp derived from glyphosate-tolerant sugar beet with beet pulp from five European locations. The experimental phase consisted of a 2-wk preliminary period followed by a 1-wk collection period for Exp. 1 and 2, and a 1-wk preliminary period followed by a 1-wk digestibility collection period for Exp. 3. Diets were comprised of grass hay at 30, 30, and 20% of DM for Exp. 1, 2, and 3, respectively, with the balance being beet components. Urea and sodium sulfate were supplemented (8 and 2.9 g, respectively, for Exp. 1 and 2; and 6 g and 2.16 g, respectively, for Exp. 3) to supply sufficient dietary N and S. Each diet was fed to sheep (96 +/- 0.9 kg) in the three experiments to at or near maintenance energy levels. Treatment differences were considered significant at P < 0.05. Apparent digestibilities of DM, OM, CP, NDF, ADF, and DE for glyphosate-tolerant fodder and sugar beets did not differ from those for commercial fodder and sugar beets in Exp. 1 and 2. There were differences (P < 0.05) in DM, OM, CP, NDF, ADF, and DE digestibilities influenced by the different varieties of beet pulp in Exp. 3, but these were not unique to just the Roundup Ready sugar beet variety. Digestibilities and feeding values of Roundup Ready fodder beet, sugar beet, and beet pulp produced from Roundup Ready sugar beet varieties were not influenced by the introduction of the Roundup Ready trait compared with conventional varieties.