Dietary Starch Level Research Articles

Effect of dietary carbohydrate level on growth performance of juvenile spotted Babylon ( Babylonia areolata Link 1807)

A growth trial was conducted to determine the effects of dietary carbohydrate level on growth performance, feed utilization and metabolism of juvenile spotted babylon. Six isonitrogenous and isoenergetic experimental diets (48% crude protein and 15 MJ kg − 1 diet) using wheat starch as the carbohydrate source, were formulated to contain six carbohydrate levels. Triplicate groups of 45 animals (initial average weight, 168.39 ± 0.69 mg) were stocked in 120-l tanks and fed to apparent satiation twice daily for 10 weeks. Growth performance and feed utilization were significantly affected by dietary carbohydrate level. Maximum weight gain and specific growth rate occurred at 20% dietary starch inclusion, survival and soft body to shell ratios were not significantly different among diets. There were significant differences in protein, lipid, moisture and glycogen content in soft body. Glycogen content in soft body was positively correlated with dietary starch level. The activities of glucose-6-phosphate dehydrogenase and fructose-1,6-bisphosphatase were significantly affected by dietary starch level, with both peaking in the 20% treatment; however, there were no significant differences in 6-phosphofructokinase activity in any treatment. Quadratic regression analysis of weight gain against dietary starch level indicated that the optimal dietary carbohydrate level for maximum weight gain of juvenile spotted babylon is 27.1% of dry diet.

Effect of high dietary starch levels on the growth performance, blood chemistry and body composition of gibel carp (Carassius auratusvar. gibelio)

An 8-week growth trial was carried out in a semi-recirculation system to investigate the effect of high dietary starch levels on the growth performance, blood chemistry, starch utilization and body composition of gibel carp (Carassius auratus var. gibelio). Five isonitrogenous and isocarloric experimental diets were formulated to contain different starch levels (24%, 28%, 32%, 36% and 40% respectively). Triplicate groups of fish (24 fish per tank with an average body weight, of 8.5 g) were assigned to each diet. The results showed that dietary carbohydrate levels significantly affected the growth performance, hepatopancreatic lipid content, pyruvate kinase (PK) activity and whole-body lipid content. Growth performance, body crude lipid and plasma glucose concentrations showed a decreasing trend with an increase in dietary starch from 24% to 40%. Pyruvate kinase activities and hepatopancreatic lipid content showed an increasing trend with the dietary starch increasing from 24% to 32%, and then a decreasing trend with the dietary starch increasing from 32% to 40%. No significant difference in the hepatopancreatic hexokinase (HK) activity, plasma triglyceride contents, body crude protein, ash and calcium (Ca) and phosphorus (P) contents was observed between different treatments. In conclusion, higher dietary starch levels (32–40%) significantly (P<0.05) decreased the growth of gibel carp in the present study.

Effect of dietary starch on rumen and small intestine morphology and digesta pH in goats

The objective of this study was to determine the effects of dietary starch level on rumen and small intestine morphology and digesta pH in goats. Eighteen 9 months old Guanzhong wether goats (body weight 28.5 ± 1.6 kg) were randomly assigned to three treatments of dietary starch levels, (1) low starch (LS, 28%), (2) medium starch (MS, 35%) and (3) high starch (HS, 46%). After a 35-day experiment, MS diet significantly stimulated the development of rumen by increasing the papillae height and surface in both ventral and dorsal ruminal sac. MS diet also significantly enhanced villus height of jejunum. In contrast, HS diet significantly decreased the ruminal pH. Compared with its effect on rumen morphology, the starch level in diet did not significantly affect small intestine development. This study indicated that starch level in diet plays an important role in rumen development.

Effect of water temperature and dietary starch on growth and metabolic utilization of diets in gilthead sea bream ( Sparus aurata) juveniles

We evaluated the effect of dietary starch level on growth performance, feed utilization, whole-body composition and activity of selected key enzymes of intermediary metabolism in gilthead sea bream juveniles reared at 18 and 25 °C. A diet was formulated to contain 48% crude protein, 12% lipids and 30% gelatinized maize starch (diet 30GS). Two other diets were formulated to include the same level of ingredients as diet 30GS except for the gelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). No adjustment to diet composition was otherwise made. Each diet was fed to triplicate groups of gilthead sea bream (30 g initial mass) for 8 weeks, on a pair-feeding scheme. The higher temperature improved growth performance but the opposite was true for feed efficiency and protein efficiency ratio. Independently of temperature, growth performance, feed efficiency and protein efficiency ratio were lower in fish fed diet 30GS. No effect of temperature or dietary starch level on whole-body composition was noticed. Hepatosomatic index and liver glycogen were higher at 18 °C and, within each temperature, in fish fed diet 30GS. Glycemia was not affected by temperature, but was lower in fish fed diet 10GS. Data on enzyme activities showed that increasing water temperature enhances liver glucokinase (GK) and pyruvate kinase (PK) activities, suggesting that gilthead sea bream is more apt to use dietary starch at higher temperatures. No effect of temperature was noticed on hexokinase (HK), fructose-1,6-bisphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6PD) and glutamate dehydrogenase (GDH) activities. Dietary starch enhanced PK and FBPase activities while depressed GDH activity, suggesting a lack of significant regulation of hepatic glucose utilization and production in this species. HK, GK and G6PD activities were unaffected by dietary composition. Irrespectively of water temperature, gelatinized starch may be included up to 20% in diets for gilthead sea bream juveniles; at higher dietary levels, growth and efficiency of feed utilization are depressed.

Effect of dietary starch source (normal versus waxy) and protein levels on the performance of white sea bream Diplodus sargus (Linnaeus) juveniles

An experiment was performed to evaluate the growth performance and feed utilization of white sea bream juveniles (initial weight, 14 g) fed diets of cornstarch of diierent origins (normal and waxy). Four experimental diets were formulated to be isolipidic and to contain normal and waxy starch (26% or 42%) at two protein (36% and 48%) levels. The growth trial lasted 15 weeks and, at the end of the trial, there were no diierences in the growth rate among groups. At the highest dietary starch level ^ but not at the lowest level ^ the feed e⁄ciency ratio and PER were signi¢cantly lower in ¢sh fed the waxy starch diet. Protein e⁄ciency ratio and N retention (% N intake) were not aiected by starch source but were signi¢cantly higher in the diets with a lower protein content. No diierences in energy retention (% energy intake) were observed among groups. Except for the protein content, which was signi¢cantly higher in ¢sh fed diets with a high protein level, no other diierences were observed among groups in whole-body composition. Hepatosomatic Index (HSI) was signi¢cantly higher in ¢sh fed highstarch diets, but there were no diierences in visceral indices among groups. The apparent digestibility coe⁄cients of protein and energy were not aiected by the dietary starch level, but were signi¢cantly lower in diets including waxy starch. Glutamate dehydrogenase activity was higher in ¢sh fed highprotein diets, but it was not aiected by dietary starch source. Alanine aminotransferase and aspartate aminotransferase activities were not diierent among groups. Glucose 6-phosphate dehydrogenase, malic enzyme and fatty acid synthetase activities were not aiected by the dietary starch level, but were signi¢cantly lower in ¢sh fed waxy starch. The results of this study indicate that diets for white sea bream juveniles may include up to 42% starch without negative eiects on ¢sh performance. Moreover, normal starch appears to be more e⁄ciently used as an energy source than waxy starch.

Effects of dietary starch and energy levels on maximum feed intake, growth and metabolism of Nile tilapia, Oreochromis niloticus

The aim of this study was to gain insight into how Nile tilapia ( Oreochromis niloticus) regulate feed and energy intake in response to diets low and high in starch and cellulose. It was hypothesized that high-starch diets would reduce feed intake due to the effect of high blood glucose level, and that stomach volume may limit feed intake of fish fed diets low in energy. Four experimental diets, low starch–no cellulose inclusion, high starch–no cellulose inclusion, low starch–with cellulose inclusion, and high starch–with cellulose inclusion, were formulated. The high-starch diets and diets with cellulose inclusion were 17.5% more energy-diluted than the low-starch diets and diets without cellulose inclusion, respectively. Male tilapia were fed to apparent satiation for six weeks. Feed and digestible energy intake of fish fed diets with cellulose inclusion increased and decreased by 8.3% and 5.5%, respectively, compared to fish fed diets without cellulose inclusion. This suggests the role of stomach volume in restricting feed consumption. Fish fed high-starch diets achieved only 0.5% more feed intake and 13.9% less digestible energy intake than fish fed low-starch diets. The lower increase in feed intake and higher decrease in digestible energy intake of fish fed high-starch diets than of fish fed diets with cellulose inclusion suggests that high blood glucose suppresses feed intake in Nile tilapia. An alternative explanation for the differences in feed and digestible energy intake of fish fed different diets was based on the fact that heat production was not influenced by starch nor cellulose-inclusion levels. Thus, under satiation feeding, oxygen uptake capacity may determine feed and digestible energy intake in fish rather than blood glucose or stomach volume.

Temperature and dietary carbohydrate level effects on performance and metabolic utilisation of diets in European sea bass (Dicentrarchus labrax) juveniles

This study aimed to evaluate the effect of temperature and dietary starch level on growth performance, nutrient utilisation, whole-body composition and activity of selected hepatic intermediary metabolism enzymes in European sea bass juveniles. An experimental diet was formulated to contain 46% crude protein, 12% crude lipids and 30% pregelatinized starch (diet 30GS); two other diets were formulated to include the same levels of all ingredients as diet 30GS except for the pregelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). Diets were assigned to triplicate groups of 25 fish (initial weight: 15 g) at two water temperatures (18 and 25 °C) for 10 weeks. Group receiving diet 30GS was fed to apparent satiation and groups fed diets 20GS and 10GS were pair-fed according to group fed diet 30GS, so that each group ate the same amount of all nutrients except for carbohydrates. At the end of the trial, growth rate, feed efficiency and protein efficiency ratio were higher at 25 than at 18 °C. Dietary starch level did not affect growth or N utilisation. Feed efficiency was inversely related to dietary starch level. Whole-body lipids and energy content were higher at 25 °C and increased with dietary starch levels. Whole-body protein and ash content were also higher at 25 °C but were not affected by dietary starch level. Liver glycogen, HSI and VI increased with dietary starch level. ADC of starch was higher at 25 °C and within each temperature decreased with increasing dietary starch levels. ADC of protein was neither affected by temperature nor dietary starch levels. Data on enzyme activities showed that hexokinase (HK) but not glucokinase (GK) was affected by temperature. Dietary starch level affected the activities of glucokinase and glucose-6-phosphate dehydrogenase (G6PD) but not of the others enzymes tested (HK, PK, FBPase and GDH).

Growth performance and metabolic utilization of diets with native and waxy maize starch by gilthead sea bream (Sparus aurata) juveniles

The effect of dietary starch source and level on growth performance, feed utilization, apparent digestibility coefficients and liver enzyme activities involved in intermediary metabolism of gilthead sea bream juveniles was studied. Five isonitrogenous (47% crude protein) and isolipidic (15% crude lipids) diets were formulated to contain 10% native (diet NS10) or waxy (diet WS10) maize starch; 20% native (diet NS20) or waxy (diet WS20) maize starch or no starch (control). Diets were adjusted with α-cellulose. Another diet was formulated without carbohydrates, and contained 70% crude protein and 15% crude lipids (diet HP). Each diet was fed to triplicate groups of 30 fish (initial weight: 20 g) for 12 weeks. The HP group was fed to near satiation and the other 5 groups were fed on a pair-feeding scheme according to the group that ingested less feed (control diet group). The reduction of dietary protein level from 70% to 47% by the incorporation of 20% starch did not significantly affect gilthead sea bream growth performance or feed efficiency. Compared to the control diet, neither the level nor the nature of starch had any measurable effect on growth performance and feed efficiency. Digestibility of starch was unaffected by source or dietary inclusion level. Diet had no effect on plasma glucose levels, but liver glycogen was higher in diet groups NS20, WS20 and HP. Dietary carbohydrates increased GK and G6PD enzyme activities and decreased ALAT and GDH enzyme activities while had only a minor effect on FBPase activity. The nature of dietary starch tested (native or waxy) had little influence on performance criteria.

Effects of raw corn starch levels on growth, feed utilization, plasma chemical indices and enzyme activities in juvenile yellowfin seabream Sparus latus Houttuyn

A 10-week growth trial was conducted to evaluate the effect of raw corn starch levels on the growth, feed utilization, plasma chemical indices and metabolic enzyme activities of juvenile yellowfin seabream Sparus latus. Four semi-purified experimental diets with different raw corn starch levels (5%, 10%, 20% and 26%) and a high-protein control diet were prepared before the experiment and hand-fed to triplicate groups of juvenile yellowfin seabream Sparus latus. Weight gain and specific growth rate for fish fed the diet containing 26% raw corn starch were significantly lower than those for fish fed 10% or 20% corn starch diets or the high-protein control diet. Fish fed 10% or 20% corn starch diets had a slightly better growth performance than those fed the 5% corn starch diet. Feed efficiency ratio and protein efficiency ratio (PER) for 20% raw corn starch fed fish were the highest among all groups, although no statistically significant differences were found among the experimental groups. The high-protein control group had a significantly lower PER value than other groups. Protein productive values for fish fed the 5% raw corn starch diet and the high-protein control diet were significantly lower than those of fish fed the 20% raw corn starch diet, but not significantly different from the values of any other group. The values of intraperitoneal fat ratio, viscerosomatic index and condition factor, as well as body and muscle compositions, were unaffected by corn starch levels. The hepatosomatic index and liver glycogen level for fish fed 5%, 10%, 20% raw corn starch and the high-protein control diets were equal but significantly lower compared with that of fish fed the 26% raw corn starch diet. Plasma values of the fish were not affected by various dietary treatments, except that a significantly higher plasma glucose concentration was measured in the high-protein control group compared with the values in the other groups. There were variations in the activities of hepatic hexokinase and pyruvate kinase of the yellowfin seabream after they had been fed different dietary raw corn starch levels for 10 weeks. The overall results showed that a 20% inclusion level of raw corn starch in the diet was better utilized by juvenile yellowfin seabream than 5%, 10% or 26% levels and had a protein-sparing effect.

Digestible fibre to ADF ratio and starch level in diets for growing rabbits

To evaluate the effect of digestible fibre (DF, hemicelluloses+pectins)/ADF ratio (1.0 and 1.3) and starch level (12, 15, and 18%) on health status, digestive physiology, growth performance, and carcass traits, 246 rabbits weaned at 27 d were fed until slaughter (76 d) with six diets formulated according to a bifactorial arrangement (2 DF/ADF ratios by 3 starch levels). Increasing DF/ADF improved DM digestibility (P<0.01), but did not affect growth performance, caecal content characteristics and slaughter traits. Increasing starch level improved digestibility efficiency and conversion index (P<0.001), decreased ileal mucosa villi height (P=0.04), without affecting growth performance, caecal fermentation and slaughter results. The increase of DF/ADF ratio tended to reduce mortality (25.0 vs 17.6%; P=0.11), whereas the raise of starch greatly increased mortality (from 6.9 to 43.1%; P<0.001) and sanitary risk (from 13.9 to 63.9%; P<0.001).

Effect of gelatinization degree and inclusion level of dietary starch on the characteristics of digesta and faeces in Nile tilapia ( Oreochromis niloticus (L.))

Higher faeces removal efficiency can help and reduce the negative impact of faecal waste on water quality and on the environment. Physicochemical properties of feed ingredients/nutrients may change the faeces characteristics and the ratio of removed to non-removed solids. The aim of this study was to assess what physicochemical properties of the diet (viscosity, fermentation and dry matter) influence faeces characteristics and faeces removal using Oreochromis niloticus (L.) as the test animal. Four experimental diets were formulated by the addition of two types of starch differing in gelatinization degree (gelatinized and native) and two levels (high and low) of starch to a basal diet according to a 2 × 2 factorial design. The diets were assigned to 16 tanks with 40 fish each, with four replicates for each diet. Replacement of native starch by gelatinized starch improved faeces removal rate, growth and digestibility ( P < 0.01), but reduced fermentation ( P < 0.05) at the end of the intestine. Addition of gelatinized starch did not change viscosity and dry matter of the digesta at the end of the intestine. A high level of starch in the diet also increased digestibility, growth and faeces removal percentage ( P < 0.05). Fermentation and dry matter content at the end of the intestine were not influenced by a high starch diet, but viscosity was higher at the high level of starch inclusion. Volatile fatty acid levels in the stomach of Nile tilapia were high in the treatments with gelatinized starch. In conclusion, intestinal fermentation induced by native starch had a negative impact on faeces removal efficiency. A higher inclusion level of starch resulted in a higher viscosity of the digesta, leading to higher faeces removal efficiency.

Body composition, dietary carbohydrates and fatty acids determine post-fertilisation development of bovine oocytes in vitro

This study assessed the interactive effects of carbohydrate type (fibre vs starch) and fatty acid (FA) supplementation (0% vs 6% calcium soaps of palm oil FA) on the post-fertilisation development of oocytes recovered from low and moderate body condition score (BCS) heifers. A secondary objective was to compare the FA composition of plasma to that of granulosa cells (GCs) and cumulus-oocyte complexes (COCs) from these animals, and to relate these findings to the developmental potential of oocytes. Plasma, GCs and COCs were recovered from 32 heifers on day 5 of a synchronised oestrous cycle for FA analyses. Oocytes were also recovered on days 10 and 15 of the same cycle after short-term ovarian stimulation (FSH + GnRH), and matured, fertilised and cultured to the blastocyst stage in vitro. High levels of dietary starch increased (P < 0.01) plasma insulin but, together with dietary FA, reduced (P < 0.05) blastocyst yields in low, but not in moderate, BCS heifers. Diet-induced alterations to the FA content of plasma were less apparent in GCs and COCs. In summary, although dietary lipids increased the FA content of COCs, the selective uptake of saturated FAs at the expense of mainly polyunsaturated FAs within the follicular compartment ensured that the FA composition of COCs was largely unaffected by diet. However, the concentration of saturated FAs within COCs was inherently high, and so further increases in FA content may have impaired post-fertilisation development. The data establish a robust nutritional framework for more detailed studies into the mechanistic effects of dietary composition on the post-fertilisation developmental potential of oocytes.

Effects of dietary carbohydrate level on growth and body composition of juvenile tilapia, Oreochromis niloticusxO. aureus

A growth trial was conducted to feed juvenile tilapia (initial weight, 9.1±0.1 g), Oreochromis niloticus×O. aureus, isonitrogenous diets for 8 weeks. Six diets were formulated containing 29% crude protein from casein and gelatin, 10% crude fat from soybean oil and refined soybean lecithin and varying levels of corn starch ranging from 6% to 46% at increments of 8%, with corresponding energy to protein (E/P) ratios of 35.6, 37.9, 40.2, 42.5, 44.8 and 47.1 kJ g−1. Weight gain (WG), specific growth rate, feed efficiency ratio and protein efficiency ratio were significantly higher in fish fed diets with starch ≥22% (or E/P ratio ≥40.2 kJ g−1) than in fish fed diets with 6% or 14% starch (or E/P ratio of 35.6 or 37.9 kJ g−1). No further improvement was measured when dietary starch content increased beyond 22%. Body protein retention showed the same general pattern as WG, and was highest in fish fed the 22% starch diet. Body composition was significantly affected by dietary starch level. Fish fed diets with starch ≥30% had significantly higher lipid content than fish fed diets with 6% or 14% starch. Ash content was negatively correlated with starch inclusion level, but moisture and protein contents did not show discernible trends among treatments. Results indicate that hybrid tilapia can utilize 46% dietary starch without growth retardation, while 22% starch in feed for juvenile tilapia containing 29% protein and 10% lipid, or an E/P ratio of 37.9 kJ g−1 is optimal.

Growth, feed utilization and body composition in two size groups of Atlantic halibut ( Hippoglossus hippoglossus) fed diets differing in protein and carbohydrate content

Two size groups (60 and 800 g) of Atlantic halibut were fed four different experimental diets varying in content of protein (41–56% of dry matter) in substitution to starch (22–6%). The response to dietary treatments differed between the two sizes of fish. In 60 g halibut growth, feed efficiency and percentage energy retention were 20%, 25% and 23% greater, respectively, in the groups fed the highest protein level compared with those fed the lowest level ( P < 0.05). In contrast, no effect of diet was seen on these variables in the 800 g fish. Further, the 60 g fish fed the diets with highest protein content became leaner than those fed the lowest protein levels, whereas no response was seen in whole body composition of 800 g fish. In the 60 g halibut, liver glycogen content increased with dietary starch level and ended more than three times higher in fish fed the diet with the highest starch level than in those fed the lowest. Liver lipid, protein and ash levels showed marked and significant trends in the opposite direction. In conclusion, 800 g halibut seem to have a lower optimal dietary protein level and to be less sensitive to dietary carbohydrates than 60 g halibut.

Digestibilidade e desempenho de coelhos oriundos de quatro padrões de alimentação até a desmama alimentados com dietas contendo diferentes níveis de amido após a desmama

Foram conduzidos dois experimentos com o objetivo de avaliar o efeito de dietas contendo níveis de 15% (normal) e 24% (alto) de amido sobre digestibilidade e desempenho de coelhos em crescimento oriundos de quatro padrões de alimentação até a desmama. Para o ensaio de digestibilidade, 96 coelhos da raça Nova Zelândia Branco, de 35 a 49 dias de idade, foram distribuídos em esquema fatorial 2x2x2 (ninhadas submetidas à baixa e alta disponibilidade de leite versus dois níveis de amido na dieta até a desmama versus dois níveis de amido na dieta após a desmama), com oito tratamentos e 12 repetições. Animais de ninhadas maiores apresentaram melhor aproveitamento digestivo da FDN. O maior nível de amido na dieta fornecida antes da desmama proporcionou melhor utilização digestiva da energia bruta após a desmama, e aquele fornecido após a desmama, melhor aproveitamento da matéria seca e da proteína. No ensaio de crescimento, 288 coelhos da raça Nova Zelândia Branco, de 35 a 70 dias de idade, foram distribuídos no mesmo esquema fatorial (2x2x2), com oito tratamentos, 18 repetições e dois animais por unidade experimental. Coelhos de ninhadas mantidas com oito láparos apresentaram menor peso vivo aos 50 dias de idade, contudo, aos 70 dias de idade, não houve diferença no peso vivo entre os animais de ninhadas contendo quatro ou oito láparos. Tanto aos 50 como aos 70 dias de idade, os animais de ninhadas contendo oito láparos apresentaram melhor conversão alimentar e menor consumo diário de ração, independentemente do nível de amido nas dietas. Animais alimentados com dietas contendo nível mais alto de amido antes da desmama apresentaram maior peso vivo, tanto aos 50 como aos 70 dias de idade.

Effects of sun-curing, formic acid-treatment or microbial inoculation of timothy on urea metabolism in lactating dairy cows

1. Urea-N recycling in lactating dairy cows fed diets with 2 different levels of dietary crude protein and starch with or without monensin E.B. Recktenwald, D.A. Ross, S.W. Fessenden, C.J. Wall, M.E. Van Amburgh Journal of Dairy Science CrossRef

Desempenho de coelhos até a desmama de acordo com o tamanho da ninhada e o nível de amido nas dietas

Foi conduzido um experimento com o objetivo de estudar as influências do padrão alimentar de coelhos durante a fase de lactação, em função do nível de amido nas dietas e da disponibilidade de leite modulada pelo tamanho da ninhada, sobre o desempenho de láparos até a desmama (35 dias). Cem ninhadas foram mantidas com oito láparos ao nascer até o 16º dia de vida. A partir do 16º dia de idade até a desmama, 60 ninhadas foram reduzidas para quatro láparos, enquanto as demais foram mantidas com oito, recebendo dietas contendo nível alto (24%) ou normal (15%) de amido. As ninhadas com quatro láparos apresentaram maior ganho de peso diário, independentemente dos intervalos analisados, sendo desmamados com maior peso em relação aos mantidos em ninhadas mais numerosas. Este efeito também foi observado naqueles que receberam dietas com alto teor de amido somente a partir do 24º dia de lactação. Os láparos mantidos em ninhadas mais numerosas apresentaram maior consumo diário de ração até 26º dia de idade. À medida que os láparos mantidos em ninhadas menores apresentaram superioridade no crescimento e a disponibilidade de leite pela coelha foi diminuída pela proximidade do final da lactação, o consumo de ração na fase final de lactação passou a ser maior para os láparos mantidos em ninhadas menores. Por outro lado, a dieta mais rica em amido proporcionou maior consumo diário, independentemente do intervalo analisado. O consumo individual de leite foi maior para láparos mantidos em ninhadas menores, não havendo diferença em relação aos níveis de amido nas dietas disponibilizadas aos animais.

Inter-relationship of microbial activity, digestion and gut health in the rabbit: effect of substituting fibre by starch in diets having a high proportion of rapidly fermentable polysaccharides.

Caecal microbial activity, digestion and gut health were analysed in the young rabbit, in response to fibre substitution by starch, in diets with high proportions of rapidly fermentable polysaccharides (pectins+hemicelluloses:acid-detergent fibre (ADF) ratio of 1.7). A range of five diets corresponding to a 60 % linear reduction of the ADF level (230 to 92 g ADF/kg) without changes in the fibre quality, and to a corresponding linear increase in dietary starch, was given ad libitum to young rabbits from 18 d until 70 d of age. A one half reduction of the ADF level resulted in a sharp increase in energy digestibility (+25 units), associated with a lower feed intake (-35 %) and to an increase of the mean retention time (+6 h) in the whole digestive tract. Despite large variations in the fibre intake (20 to 59 g ADF/d), the fibre digestive efficiency remained similar among the five diets. Starch ileal concentrations were low after 4 weeks of age (<5 %), and variations with age were significant when the dietary starch level was over 19 %. A 65 % lower biomass production was measured when the ADF level progressed from 230 to 165 g/kg, and no precise relationship was found with fermentative activity. Reducing the fibre intake led to a linear decrease of caecal volatile fatty acids concentrations, and to higher pH and NH3 levels. An increased occurrence of mortality by diarrhoea was registered with the lowest fibre intake. It can be concluded that a sufficient supply of fibre, with high proportions in rapidly fermentable polysaccharides, stimulates the maturation of microbial activity and reduces the occurrence of diarrhoea.

Effects of dietary energy and starch concentrations for newly received feedlot calves: II. Acute-phase protein response1,2

Two hundred forty five market-stressed bull and steer calves (205 +/- 14 kg) were received in January and September 2001 to determine the response of acute-phase proteins to dietary energy and starch concentrations and to determine whether acute-phase proteins could be used as a diagnostic or prognostic tool for calves affected by bovine respiratory disease. On arrival, calves were randomly assigned to one of two dietary energy levels (0.85 or 1.07 Mcal of NEg/kg of DM) and one of two dietary starch levels (34 or 48% of dietary ME from starch; n = 5 pens/treatment). All calves were weighed, and plasma and serum samples were collected from a subset of animals (n = 6 calves/pen; 30 calves/treatment) on d 0, 7, 14, 28, and 42 of the receiving period. This subset of calves (n = 120) was used for all subsequent analyses. Concentrations of fibrinogen (Fb), haptoglobin (Hp), and serum amyloid-A (SaA) were determined. In addition, samples were collected from the subset of calves when they received medical treatment and 7 d following treatment to measure serum concentrations of Hp and SaA. Serum concentrations of Fb, Hp, and SaA did not differ among dietary treatments, but decreased (P < 0.03) as day of the receiving period increased. Fibrinogen (P < 0.001) and the ratio of Fb:total blood protein were greater (P < 0.003) in calves treated multiple times than in calves never treated or treated once for bovine respiratory disease. In addition, on d 0 and 7, Hp concentration increased (antimicrobial treatment x day interaction, P < 0.03) as the number of antimicrobial treatments increased, and was greater on d 14 and 28 in calves treated multiple times than in calves never treated or treated once. Haptoglobin concentration was greater (P < 0.05) in calves on medical treatment days compared with recovery days (7 d after medical treatment). Although diet seemed to have little effect on acute-phase protein response, these results suggest that haptoglobin may be useful as a diagnostic tool to make management decisions regarding treatment protocols for calves with bovine respiratory disease.

Effects of dietary energy and starch concentrations for newly received feedlot calves: I. Growth performance and health.

Crossbred calves (n = 572; initial BW = 186 +/- 27 kg) purchased from northern Texas, Arkansas, and southeast Oklahoma auction markets were delivered to the Willard Sparks Beef Research Center, Stillwater, OK, and used to study the effects of dietary energy and starch concentrations on performance and health of newly received feedlot calves during a 42-d receiving period. On arrival, calves were assigned randomly to one of two dietary energy levels (0.85 or 1.07 Mcal NEg/kg DM) and one of two dietary starch levels (34 or 48% of ME from starch) in a 2 x 2 factorial arrangement of treatments. Cattle were weighed and serum samples were collected on d 0, 7, 14, 28, and 42. Individual animal records of morbidity were kept for all cases of respiratory and other disease. Nasal swabs were collected from each morbid animal and cultured for upper-respiratory pathogens. There were no energy x starch level interactions for performance or health response variables. Daily gain (1.14 kg/d) and gain efficiency (ADG:DMI = 0.179) were not affected by increasing dietary energy or starch concentrations. Calves fed low-energy diets consumed (P < 0.05) more DM. No difference (P = 0.54) was detected in morbidity for calves fed high-energy (62.4% calves treated) compared with low-energy (65.8% calves treated) diets; however, calves fed the high-starch diets had numerically (P = 0.11) greater morbidity than calves fed low-starch diets (68.8 vs. 59.4% calves treated, respectively). There were no energy or starch effects on Mannheimia haemolytica or Pasteurella multocida antibody titers; however, day effects (P < 0.02) occurred. On d 7, 14, and 28, calves had antibody titers for P. multocida that were greater (P < 0.05) than titers on d 0. In addition, calves had greater antibody titers to M. haemolytica on d 7 and 14 than on d 0. Nasal swabs revealed that calves fed the high-energy diets tended (P = 0.06) to have a lower percentage of morbid calves with P. multocida during the first antimicrobial treatment and a lower percentage of Haemophilus somnus isolates during the first (P = 0.01) and second (P = 0.06) antimicrobial treatments than calves fed the low-energy diets. Although animal performance was not influenced, the present data suggest that feeding the high-energy diet decreased the percentage of P. multocida and H. somnus pathogens in calves that received one or more antimicrobial treatments.