Feed Apparent Digestibility Research Articles

Fermented total mixed ration enhances nutrient digestibility and modulates the milk components and fecal microbial community in lactating Holstein dairy cows.

Fermented total mixed ration (FTMR) is an effective method of preserving high-moisture byproducts with higher aerobic stability after fermentation. FTMR has the potential to fulfill the daily nutritional requirements of cattle and enhance their production performance. The objective of this research was to examine the influence of FTMR on lactation performance, total tract apparent digestibility, fecal microbiota communities, and fermentation profiles in lactating dairy cows. A total of 12 cows were randomly assigned into two groups: the TMR group and the FTMR group. The TMR group was fed a total mixed ration (TMR) diet, and the FTMR group was fed an FTMR diet. The FTMR did not impact milk yield in dairy cows despite a decrease in dry matter intake, which increased the efficiency of the feed. In contrast to that in the TMR group, the milk fat content in the FTMR group was greater. The FTMR group showed greater digestibility of neutral detergent fiber (NDF), organic matter (OM), dry matter (DM), crude protein (CP), and acid detergent fiber (ADF) in the total digestive tract than did the TMR group. The FTMR increased the concentration of butyrate in the fecal matter and reduced the pH of the feces. The Chao1, ACE, and Shannon indices of the archaeal community in dairy cow feces were significantly higher in cow fed the FTMR compared to those fed the TMR. LefSe analysis revealed higher levels of Oscillospira, Lactobacillus, Prevotella, and Dehalobacterium in the feces of dairy cows fed the FTMR than in those fed the TMR. However, the abundances of Roseburia, rc4-4, Bulleidia and Sharpea exhibited the opposite trend. The abundances of Halobacteria, Halobacteriales, and Halobacteriaceae, which are biomarkers for distinguishing fecal archaea in the TMR from the FTMR, were substantially greater in the feces of dairy cows that consumed the TMR than in those that consumed the FTMR. Therefore, FTMR can improve the milk fat content, total tract apparent feed digestibility efficiency, and diversity of archaea in the feces. Additionally, this work provides a theoretical basis for the feasibility of FTMR feeding for dairy cows.

PSX-B-16 Effects of Bacillus Subtilis Subsp. Subtilis Strain Atcc PTA-125135 Supplementation on Performance and Digestibility in Weaned Pigs

Abstract An experiment was conducted to evaluate the effects of supplemental Bacillus subtilis subsp. subtilis strain ATCC PTA-125135 on growth performance, feed efficiency, and feed digestibility in weaned pigs. Newly weaned pigs (n = 96) were randomly assigned to stacked-deck pens (n = 48) in two assemblies in adjacent rooms. Pens were randomly assigned within assembly to one of three treatments comprising control, S-0.25, or S-0.50. A common starter diet was fed for 10 days and then pigs were fed the assigned treatment for 17 days. The diets consisted of: 1) Control, a corn-soybean meal diet (1.30% total lysine, chromium dioxide as marker); 2) S-0.25 (control diet with addition of 0.25 g per kg supplement in feed; 3) S-0.50 (control diet with addition of 0.50 g per kg supplement in feed), where supplement comprised 8.1 × 108 CFU g-1 of Bacillus subtilis PTA-125135. Body weights and feed disappearance were collected on d 0, d 7 and 14 of supplementation. Feed digestibility was measured by total collection of feces from d 14-17. Data were analyzed by ANOVA with main effects of treatment and room. Contrasts were used to compare means of microbial supplementation with control. Pig performance did not differ from d 0-7. During d 8-14, body-weight gain was not affected, but feed intake was decreased by approximately 6.0 percent (P = 0.147), and G:F was improved by approximately 10.6 percent (P = 0.106). Apparent feed digestibility did not differ among groups (P = 0.507), but total digested dry matter was less for treated groups (P = 0.163), which reflects reduced recorded dry matter intake. The changes observed from week 1 to week 2 indicate a transition was occurring with microbial supplementation resulting in improved utilization. These results indicate that supplementation of B. subtilis PTA-125135 improved feed efficiency. Supplementation duration should be considered for future evaluations.

Comparison of gastrointestinal transit times in stabled Thoroughbred horses fed freshly cut pasture and three conserved forage-based diets

Context The type of forage offered to horses varies in physical form, moisture content and nutrient quality, and these variables could affect the intake, passage rate and digestibility of the forage consumed. Aims To investigate the changes in passage rate of digesta through the gastrointestinal tract in horses fed four different forage-based diets (diet effect). Methods Thoroughbred mares (n = 6) were stabled in loose boxes for 6 weeks. During Weeks 1, 3 and 5 (washout periods), all horses were fed freshly cut pasture, either in restricted quantities (Week 1) or ad libitum (Weeks 3 and 5). Using a 3 × 3 Latin square design during Weeks 2, 4 and 6, each pair of horses was abruptly transitioned to one of three conserved forage-based diets (chopped ensiled forage fed exclusively or with oats, or perennial ryegrass hay with oats) fed ad libitum. At the beginning of each week, indigestible polyethylene markers (n = 200) were administered to the horses via a nasogastric tube, followed immediately by transition to the new diet. Key results There was a significant diet effect on the daily dry-matter intake of feed (P < 0.0001), percentage of time spent eating (P < 0.001), frequency of voiding faeces (P < 0.05) and quantity of faeces voided (P < 0.0001). There was a significant horse effect on the daily dry-matter intake of feed (P < 0.0001) and quantity of faeces voided (P < 0.0001), but no differences in the percentage of time spent eating or the frequency of voiding faeces. There were significant diet and horse effects on the time to recovery of the first marker in the faeces (P < 0.01 and P < 0.01 respectively) and the mean retention time of markers in the gastrointestinal tract (P < 0.05 and P < 0.001 respectively). Mean retention time was negatively correlated with feed intake and quantity of faeces voided (r2 = –0.51 and r2 = –0.64 respectively). Conclusions Longer mean retention time was associated with a greater fibre content in the diet and a restricted feed supply, thus supporting the hypothesis that horses alter mean retention time on the basis of a nutrient absorption optimisation model. Implications Feed composition, but also the quantities offered, may alter measurement of apparent feed digestibility in horses.

Influence of 5′‐inosine monophosphate and 5′‐guanosine monophosphate on growth, feed digestibility and activity of digestive enzymes in turbot Scophthalmus maximus

We evaluated the influence of different proportions of 5′‐inosine monophosphate (IMP) and 5′‐guanosine monophosphate (GMP) on growth, feed digestibility and activity of digestive enzymes of turbot Scophthalmus maximus. Weight gain and daily feed intake were significantly higher in S. maximus fed with IMP or GMP, in comparison with fish fed with neither IMP nor GMP. The growth of 0.05% IMP + 0.05% GMP group was the best, and the intestinal digestive function was improved. The addition of IMP and GMP to fish diets significantly increased the apparent feed digestibility coefficient of dry matter and protein, as well as intestinal protease activity. The highest intestinal protease activity was observed in fish fed with 1 g/kg IMP. However, the lipase activity in hepatopancreas decreased significantly after addition of nucleic acid. According to our results, the optimal level of dietary IMP is 1 g/kg, which is in line with most of the growth performance and feed digestibility.

Influence of dietary protein level on growth performance, digestibility and activity of immunity‐related enzymes of leopard coral grouper, Plectropomus leopardus (Lacépède, 1802)

An 8‐week feeding trial was conducted to assess the interaction between dietary protein levels and fish growth, digestibility and activity of immunity‐related enzymes of Plectropomus leopardus. Five diets with different protein levels (400 g/kg, 450 g/kg, 500 g/kg, 550 g/kg and 600 g/kg protein) were designed. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed higher weight gain rates than fish fed 400 g/kg and 450 g/kg dietary protein. Ingestion rate in fish fed with 500 g/kg dietary protein was significantly higher than those with other diets. P. leopardus fed with 500 g/kg, 550 g/kg and 600 g/kg dietary protein, showed that feed coefficients were significantly lower than those fed with 400 g/kg and 450 g/kg dietary protein. Net protein utilization was significantly lower in fish fed with 400 g/kg diet than those with other diets. Fish fed with 400 g/kg and 450 g/kg dietary protein had an apparent feed digestibility coefficient for dry matter that was significantly lower than that with other diets. Protease activity was highest in fish fed on 500 g/kg dietary protein. Fish fed with 500 g/kg dietary protein, had the highest superoxide dismutase activity. Fish fed with 600 g/kg dietary protein, had the highest alkaline phosphatase activity. Thus, a diet containing 500 g/kg protein is recommended for P. leopardus aquaculture.

Effect of feeding whole cottonseed as a supplement on digestibility and rumen fermentation characteristics of sheep

An experiment was conducted in vivo to investigate the effects on the apparent feed digestibility and rumen fermentation of feeding whole cottonseed (WCS) as a supplement for sheep fed grass hay (GH). Four different diets (T1, T2, T3 and T4) were used as GH alone, GH plus 150, 300 and 500 g WCS d-1 on fresh basis. The main objectives of the in vivo experiment were to examine digestibility and rumen fermentation characteristics (pH, ammonia and VFA concentration) of sheep fed four diets. The results of this experiment indicated that supplementation of WCS at a level of 500 g d-1 (0.37 of the diet) with GH reduced DM, ADF and NDF digestibility. There was no statistically significant effect on total rumen VFA, but the molar proportions of acetate, propionate and butyrate were altered by the addition of highest rate of WCS. These results suggested that WCS might have reduced the number or activity of cellulolytic rumen microorganisms.Bang. J. Anim. Sci. 2017. 46 (4): 239-243

Interaction between milk allowance and fat content of the starter feed on performance of Holstein calves

Sixty-six Holstein male calves [42±6.0kg of body weight (BW) and 12±3.1 d of age] were housed individually and allocated to 1 of 4 treatments following a 2 × 2 factorial complete randomized design to assess the potential interaction between milk replacer (MR) allowance and fat content in the starter feed. Thus, 4 treatments were evaluated: a low-fat (4.1% fat; LF) starter feed offered along with 4L/d of MR (4LF), a high-fat (11.2% fat; HF) starter feed plus 4L/d of MR (4HF), a LF starter feed offered with 6L/d of MR (6LF), and an HF starter feed offered with 6L/d of MR (6HF). Calves were fed either 4 or 6L/d of MR (25% crude protein and 19.2% fat) in 2 offers (0800 and 1630h) and had ad libitum access to either an LF or an HF starter feed (21.4 and 22.3% crude protein). Calves were weaned at wk 6 of study by halving the daily MR allowance for 1 wk. Individual MR and starter feed intakes were recorded daily and BW was determined weekly. A glucose tolerance test was performed on d 30 of study to evaluate the effects of increased energy provision on glucose metabolism. Apparent feed digestibility was measured for the last 5 d of study. Overall, fat content of starter feed had no effect on solid feed intake. However, during wk 8 of study (after weaning), calves in the LF treatment had greater starter feed intake than HF calves. Calves on 6L/d of MR had greater BW than calves fed 4L/d from the second week of study until weaning. After weaning, 6LF calves had lesser BW than 6HF calves. Calves on 6L/d of MR had greater average daily gain than calves fed 4L/d, and 6HF calves tended to have the greatest average daily gain. Glucose clearance rate tended to be lesser for HF than for LF calves. In conclusion, offering 6L/d of MR increased growth performance before weaning and, when offering 6L/d of MR, feeding a high-fat starter feed resulted in the greatest BW after weaning.

Effect of dental correction on voluntary hay intake, apparent digestibility of feed and faecal particle size in horse

In nine adult Warmblood horses with mild to moderate dental findings (no signs of discomfort during chewing), voluntary hay intake before and after dental correction was examined. In a second experiment, digestibility of feed and faecal particle size were determined (3 days of total faecal collection) before and after dental correction. During both digestion trials including a 3-day adaptation period, the amount of hay and concentrate (mixture of oats, barley and maize) was kept constant in each individual horse before and after dental correction. Voluntary hay intake in individual horses ranged from 11 to 22 g DM/kg BW/day and did not differ before and after dental treatment. Apparent digestibility of DM, energy, crude fibre and Nfe increased significantly after dental correction (energy digestibility before dental correction 46.8 ± 7.4%, after dental correction 51.5 ± 8.5%). Apparent digestibility of feed was higher in horses eating more concentrates than in those eating less concentrates. Improvement of digestibility was more marked in horses eating larger amounts of grain. There was no relationship between severity or type of dental alterations and improvement of apparent feed digestibility. Dental correction had no effect on faecal particle size.

Chloroform decreases rumen methanogenesis and methanogen populations without altering rumen function in cattle

Anthropogenic CH4 emissions are widely recognised as a world wide problem due to their global warming potential and because they represent a loss of dietary energy to ruminants. Few recent studies have examined medium or long term effects of methanogen inhibitors on rumen functional parameters and development of resistance to them. The aim of our study was to investigate medium term effects of a potent methanogen inhibitor on methanogen populations using molecular techniques and rumen function. Six rumen fistulated cows were divided into two groups and allocated to control and chloroform treatment and fed at a fixed rate of 8.4kgdry matter (DM)/cow/d. After 7d of acclimatization, treatment cows were dosed daily with 1.5ml of chloroform in 30ml of sunflower oil for 42 d, while control cows only received sunflower oil. Key indicators of rumen function monitored included rumen pH, rumen fill, apparent feed digestibility, apparent rumen digesta retention time, total protozoa numbers, and volatile fatty acid (VFA) and NH3 concentrations. Methane emissions were monitored using the SF6 tracer technique, and methanogens using denaturing gradient gel electrophoresis (DGGE) and four clone libraries. Methanogens and acetogens were monitored in a single cow by most probable number culturing methods. Chloroform, a known inhibitor of methanogenesis, resulted in an immediate and dramatic decrease in CH4 emissions and methanogen numbers, with the effect being most pronounced 1wk after the start of the treatment. Thereafter, CH4 emissions increased slowly, reaching 62% of pre-treatment levels by d 42. The effect on CH4 emissions was reflected by a near complete disappearance of DGGE bands associated with methanogens in treated cows. This response was particularly obvious for Methanobrevibacter species. There were no effects of chloroform on apparent rumen digesta retention time, apparent feed digestibility, pH, NH3 or rumen fill. Total protozoa numbers tended to increase during the study in both groups. Total VFA concentrations did not change with chloroform treatment, but the acetate:propionate ratio during the period of dosing was lower (P<0.01) for treated cows (1.9) in the middle of the study (d 23) than in the control cows (2.7), but did not differ after treatment ceased at d 53. Despite profound effects of chloroform on CH4 emissions and methanogens, chloroform did not appear to alter basic rumen function. Whether a reduction in CH4 loss improves feed conversion efficiency requires further research using substances which have a sustained anti-methanogenic effect.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Effect of DL-malic acid supplementation on feed intake, methane emission, and rumen fermentation in beef cattle

The objective of this study was to determine the effect of dietary concentration of dl-malic acid (MA) on DMI, CH(4) emission, and rumen fermentation in beef cattle. Two Latin square experiments were conducted. In Exp. 1, six beef heifers (19 +/- 1 mo old) were assigned in a duplicated Latin square to 1 of 3 dietary concentrations of MA on a DMI basis (0%, MA-0; 3.75%, MA-3.75; or 7.5%, MA-7.5) over 3 periods. In Exp. 2, four rumen-fistulated steers (48 +/- 1 mo old) were assigned to 1 of 4 dietary concentrations of MA (0%, MA-0; 2.5%, MA-2.5; 5.0%, MA-5.0; or 7.5%, MA-7.5) on a DMI basis, over 4 periods. Both experimental diets consisted of grass silage and pelleted concentrate (containing MA). Silage was fed ad libitum once daily (a.m.), whereas concentrate was fed twice daily (a.m. and p.m.) with the aim of achieving a total DMI of 40:60 silage:concentrate. In both Exp. 1 and 2, experimental periods consisted of 28 d, incorporating a 13-d acclimatization, a 5-d measurement period, and a 10-d washout period. In Exp. 1, enteric CH(4), feed apparent digestibility, and feed intake were measured over the 5-d measurement period. In Exp. 2, rumen fluid was collected on d 16 to 18, immediately before (a.m.) feeding and 2, 4, 6, and 8 h thereafter. Rumen pH was determined and samples were taken for protozoa count, VFA, and ammonia analysis. Enteric CH(4) emissions were estimated by using the sulfur hexafluoride tracer technique and feed apparent digestibility was estimated by using chromic oxide as an external marker for fecal output. In Exp. 1, increasing dietary MA led to a linear decrease in total DMI (P < 0.001) and total daily CH(4) emissions (P < 0.001). Compared with the control diet, the greatest concentration of MA decreased total daily CH(4) emissions by 16%, which corresponded to a 9% reduction per unit of DMI. Similarly, in Exp. 2, inclusion of MA reduced DMI in a linear (P = 0.002) and quadratic (P < 0.001) fashion. Increasing dietary MA led to a linear decrease in molar proportion of acetic (P = 0.004) and butyric acids (P < 0.001) and an increase in propionic acid (P < 0.001). Ruminal pH tended to increase (P = 0.10) with increasing dietary MA. Dietary inclusion of MA led to a linear (P = 0.01) decrease in protozoa numbers. Increasing supplementation with MA decreased CH(4) emissions, but DMI was also decreased, which could have potentially negative effects on animal performance.

The relationship between cheek tooth occlusal morphology, apparent digestibility, and ingesta particle size reduction in horses

To investigate potential relationships between cheek tooth occlusal morphology, apparent feed digestibility, and the reduction in feed particle size that occurs during digestion in horses. Cross-sectional study. 17 horses of various ages and breeds and either sex. Horses were fed 1 of 3 hay-based diets ad libitum for 14 days prior to euthanasia; nutrient analysis was performed on samples of each of the 3 diets. At the time of postmortem examination, the head was disarticulated, photographs were taken of the occlusal surfaces of the maxillary and mandibular cheek tooth arcades, and samples of stomach and small colon or rectum contents were collected for determination of apparent feed digestibility and particle size determination. An overall oral pathology score was assigned, and morphologic features of the occlusal surfaces of the cheek tooth arcades were determined. Results of nutrient analyses did not differ among the 3 hay diets, and there was no significant difference in apparent feed digestibility among diets. Feed particle size differed significantly among the 3 diets, but stomach content and fecal particle sizes did not differ among diet groups. No significant correlations were identified between cheek tooth morphologic variables and feed digestibility, and fecal particle size was not significantly associated with oral pathology score. Results did not provide any evidence of associations between cheek tooth morphologic variables, fecal particle size, and apparent digestibility in horses.

Respuesta productiva de becerros Holstein alimentados con alfalfa de diferente calidad y enzimas fibrolíticas en la etapa pre y pos destete

The effect of fibrolytic enzyme (FE) supplements and alfalfa quality (i.e. fiber content) on calf productive performance, apparent feed digestibility, and rumen development during the pre- and post-weaning period was evaluated. Before weaning, calves were fed daily 4 L of milk (MI) and solid feed (starter concentrate (SC) + alfalfa hay) ad libitum. Thirty-six, Holstein calves (3 to 7 d of age) were distributed in a random block design with six treatments: 1) MI-SC + low-fiber alfalfa, 2) treatment 1 + FE, 3) MISC + medium-fiber alfalfa, 4) treatment 3 + FE, 5) MI-SC + high-fiber alfalfa, and 6) treatment 5 + FE. Experimental period was 105 d and animals were weaned at d 60. The FE supplement improved (P 0.05). Apparent feed digestibility was similar among treatments (P>0.05) for dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF). There were significant differences (P 0.05) among treatments. Inclusion of FE improved daily weight gain and feed efficiency in the preweaning period.

Feed intake, digestion kinetics and rumen volatile fatty acids in Menz rams supplemented with Lablab purpureus or graded levels of Leucaena pallida 14203 and Sesbania sesban 1198

35 Menz rams weighing 19.3 ± 0.87 kg (mean ± S.D.) were used in a randomized block design experiment that was conducted for 35 days at Debre Zeit Research Station of the International Livestock Research Institute, Ethiopia. The objectives of the study were to determine feed intake, apparent digestibility, passage rate and level of rumen volatile fatty acids (VFA) in Menz rams fed tef ( Eragrostis tef) straw. The basal diet was supplemented daily on DM basis with dried foliage of Lablab purpureus, LAB – (230 g) or graded levels of Leucaena pallida 14203, namely, LP1 – (170 g), LP2 – (230 g), LP3 – (290 g), and Sesbania sesban 1198, namely, SS1 – (170 g), SS2 – (230 g), and SS3 – (290 g). The nitrogen (N) content of the supplement feeds was over 28.8 g kg −1 DM, whereas it was only 8.5 g kg −1 DM in the basal feed. High contents of NDF (747.6 g kg −1 DM) and ADF (419.5 g kg −1 DM) were determined in tef straw compared to the supplement feeds. Among the supplement feeds, L. purpureus had relatively high NDF (454 g kg −1 DM) and ADF (346.2 g kg −1 DM) content. L. pallida 14203 contained relatively high levels of the anti-nutritive factors, namely, condensed tannins (82.7 Abs g −1 NDF) and soluble phenolics (27.9 g kg −1 DM). Basal feed DM intake ( P < 0.05) reduced with an increase in the level of L. pallida 14203 supplementation. The apparent digestibility of N, ADF and ADL was lower ( P < 0.001) in L. pallida 14203 than in L. purpureus or S. sesban 1198 supplemented rams. L. pallida 14203 promoted lower ( P < 0.05) fractional outflow rate of particulate matter from the rumen and longer rumen mean retention time than L. purpureus and S. sesban 1198. Higher levels of total VFA ( P < 0.001) were observed in S. sesban 1198 than in L. pallida 14203 supplemented rams. It was concluded that the anti-nutritive factors in L. pallida 14203 have a major impact on fractional outflow rate of particulate matter from the rumen, and the digestibility of nutrients, with particular limitations on N digestibility. Increasing levels of S. sesban 1198 supplementation reduced nutrient digestibility due to increased passage rate, and thus supplementation of animals with the lowest level of the fodder tree appears to be more appropriate. The relatively high fiber content of L. purpureus reduced intake and apparent digestibility of feed on a limited scale.

同一飼料を与えたトカラ種山羊とサフォーク種めん羊の消化率の比較

A comparison of digestion was made between Japanese native Tokara buck kids (Tokara) and Suffolk ram lambs (Suffolk) fed alfalfa hay cube digestion trial, orchardgrass hay digestion trial and mixed feed trial consisting of 4 parts rice straw to 3 parts of wheat bran (rice straw. wheat bran digestion trial) for the purpose of ascertaining the digestible performance of each feed, respectively. In this experiment, the same four Tokara and the same four Suffolk lambs were used, respectively, aged five to seven months. The experimental feeds were adjusted to supply a no refusal, and also the amounts were the same per metabolic body size for each of the digestion trials. The results were as follows : (1) The digestibility coefficients in percentages for all components of the experimental feeds were lower in the Tokara than in the Suffolk except for crude protein and nitrogen free extracts in the alfalfa hay cube digestion trial.(2) Components showing significant differences were crude fiber, acid detergent fiber and neutral detergent fiber in all digestion trials. In addition to this, components demonstrating significant differences were dry matter and gross energy in the alfalfa hay cube digestion trial, dry matter, crude fat and gross energy in the orchardgrass hay trial, and crude fat in the rice straw. wheat bran digestion trial, respectively.(3) The nutritive values per dry matter were lower for total digestible nutrients and digestible energy in the Tokara than in the Suffolk in all of the digestion trials, but the orchardgrass hay digestion trial alone showed significant differences.(4) Digestible crude protein per dry matter was similar for the Tokara and the Suffolk. They were not significant in any digestion trial.(5) Nitrogen balance was similar for the Tokara and the Suffolk in all digestion trials.(6) Relative to the Suffolk, it was concluded that the apparent digestibility of feed for the Tokara was low, especially of fibrous components.

The effect of antibiotics on the apparent digestibility of feed for rainbow trout

The effect of antibiotics on the apparent digestibility of feed for rainbow trout

Effect of amount consumed and diet composition on the apparent digestibility of feed in cattle and sheep

SummaryDigestibility trials were conducted at two stages of lactation with each of 107 Friesian cows using three diets (60:40, 75:25, 90:10 proportions of compound feed to medium quality hay fed long). Each cow received throughout lactation fixed daily allowances of one of these diets at either 2·26 or 2·63 times average maintenance requirements (MM), or was fed ad libitum, average intake equalling 3·07 MM. The digestibilities of the diets were also measured on immature cattle at 0·76 and 1·33 MM and sheep at 0·65 and 1·27 MM.For all classes of stock the digestibility of dry matter increased linearly and that of fibre decreased curvilinearly with increasing proportion of compound in the diet. There was no interaction of effects of diet composition and amount consumed on digestibility of feed. The digestibility of both dietary components declined for the young cattle and sheep with increased intake. The digestibilities for lactating cows were lower than for other stock but did not change with amount consumed or milk yield. Digestibility was slightly higher for first and second calf cows than for adult cows; and was higher for organic matter in mid lactation compared with early lactation for adult cows.These results for dairy cows conflict with the generally accepted interpretation that a linear decline in digestibility occurs from once to five times maintenance intake, embracing all classes of stock.

EFFECTS OF DIET AND SIZE ON GROWTH, FEED DIGESTIBILITY AND DIGESTIVE ENZYME ACTIVITIES OF THE MARINE SHRIMP,Penaeus setiferusLINNAEUS

ABSTRACTRelationships between protein level, size, apparent feed digestibility, digestive enzyme activities and growth ofPenaeus setiferuswere investigated during a 30‐day growth trial. Small (3.7 g), medium (9.5 g), and large (14.7 g) shrimp were fed four isocaloric diets with varying protein levels. Apparent total dry matter digestibilities and apparent protein digestibilities were determined for small and medium shrimp. General and acid protease, trypsin, carboxypeptidase A and B, amylase, chitinase, non‐specific esterase and lipase activities were also assayed for small and medium shrimp.Shrimp survival was unrelated to diet or size. Instantaneous growth rate, total dry matter and protein digestibilities decreased as shrimp size increased. Small shrimp fed the 22% protein diet grew the least but exhibited the highest enzyme activities, especially carbohydrases. Small shrimp fed the 38% protein diet displayed the highest dry matter digestibility. Medium shrimp fed the 30% protein diet exhibited the lowest survival and growth while medium shrimp fed the 22% protein diet exhibited the highest enzyme activities. Higher digestive enzyme activities on the 22% protein diet may be evidence of an adaptation to a diet containing less digestible proteins.

GROWTH. FEED DIGESTIBILITY, AND PROXIMATE BODY COMPOSITION OF JUVENILE Penaeus vannamei AND Penaeus monodon GROWN AT DIFFERENT DISSOLVED OXYGEN LEVELS

ABSTRACTGrowth, feed digestibility (apparent total dry‐matter digestibility), and proximate body composition of juvenile Penaeus vannamei and Penaeus monodon were evaluated at dissolved oxygen (DO) levels of 1, 2, 3, and 4 ppm at a mean temperature of 28°C. The four different W levels were obtained by aerating different rates of nitrogen gas countercurrent to a constant flow of seawater. A standard formulated diet containing the marker material Cr2O3, and a mean 280% exchange of 30 to 32 ppt seawater per day were used. Initial wet weights of shrimp were 60.2 and 55.5 mg for P. vannamei and P. monodon, respectively. Final mean wet weights for shrimp maintained at 1, 2, 3, and 4 ppm DO level after a 16‐day growth trial were 0.24, 0.40, 0.42, 0.46 g, and 0.16, 0.26, 0.29, 0.29 g for P. vannamei and P. monodon, respectively. For both species, a significant reduction in growth and in the instantaneous growth rate (k) was obtained at the lowest Do level. No significant differences were observed for apparent feed digestibility in either shrimp. Laboratory analysis revealed no differences in moisture and lipid content for both species, while protein content was found to differ only in P. monodon grown at different DO levels. A description of the experimental system and a discussion of the significance of the data to the production of shrimp in ponds is presented.

Effects of Feeding Level, Air Speed and Temperature on digestibility and Growth in the Calf

In the first 3 weeks of age the calf is most susceptible to diarrhoea. In a review of the literature, Williams (1977) concluded that the lower critical temperature of 3-day-old calves on restricted levels of feeding was between 9°and 13°C and by approximately one month of age was between 0° and 5°C. these temperatures can be increased by air movement (Blaxter and Wainmann, 1964). Grimble (1982) suggested that calves should not be exposed to air speeds greater than 0.25 m/s. Studies in older cattle and sheep, with a functional rumen, have shown that exposure to cold was associated with a lower apparent digestibility of feed, irrespective of changes in feed intake (Christopherson, 1976). Williams and Innes (1982) fed a milk substitute diet to calves from 24 to 38 days of age and compared housing the calves in air temperatures of 3° and 18°C. There were no significant differences between air temperatures in the apparent digestibilities of dry matter (DM), fat and nitrogen (N) (p&gt;0.05) but there were significant increases in faecal water excretion and significant decreases in water intakes and urine volumes at 3° compared to 18°C (p&lt;0.05). The present experiment was designed to determine the effects, at different feeding levels, of continuous exposure to cold (10°C) compared with warm (25°C) air and to low (&lt;0.2 m/s) compared with high (&gt;3.0 m/s) air speeds on (a) the apparent digestibility of a high fat milk substitute diet, (b) water intakes and faecal water excretions and (c) growth rates, in calves from 2 to 24 days of age.

Effects of intense abdominal irradiation at a high dose (1 100 rd) on gastric secretion and apparent feed digestibility in swine

Effects of intense abdominal irradiation at a high dose (1 100 rd) on gastric secretion and apparent feed digestibility in swine