Comparison of degradability of starch in concentrates by enzymes and rumen fluid

Digestibilidade do amido e comportamento ingestivo de novilhos confinados sob efeito de doses de complexo enzimático em dietas de alta densidade energética

RESUMO O objetivo do presente trabalho foi avaliar a conversão alimentar, a digestibilidade do amido, o comportamento ingestivo e o escore de sobras da dieta e de fezes de novilhos confinados, suplementados com doses do complexo enzimático (0; 2,5; 5,0 e 7,5g animal-1 dia-1) e alimentados com dieta constituída por 85% de grão de milho e 15% de núcleo proteico, vitamínico e mineral, na base seca, isenta de forragem. O delineamento experimental foi o de blocos ao acaso contendo quatro tratamentos e quatro repetições. Trinta e dois novilhos inteiros, ½ sangue Angus Nelore, com idade média de 12 meses e peso vivo médio inicial de 422kg, foram confinados por um período de 77 dias. Cada grama de inclusão de complexo enzimático melhorou a conversão alimentar em 0,1652%, reduziu a matéria seca das fezes em 0,4648% e o tempo de ingestão de água em 0,0068 horas dia-1. A máxima digestibilidade do amido foi alcançada na dose de 5,08g animal-1 dia-1. A inclusão progressiva do complexo enzimático à dieta de alta densidade energética promoveu melhoria na conversão alimentar, redução na matéria seca das fezes e diminuição do tempo de ingestão de água. A dose de 5g animal-1 dia-1 do complexo enzimático aumentou a digestibilidade do amido.

Methods to study degradation of ruminant feeds

Ruman degradation is crucial in the supply of dietary nutrients to meet the nutrient demands of the anaerobic microbes and body tissues of ruminant animals. Therefore, it is essential to study the dynamics of rumen degradation of various feeds before their potential use to formulate nutritious diets for ruminant animals. Amongst many methods that have been used in the past, thein saccomethod has been the most effective method to study rumen degradation. However, this method is undesirable due to its implications for animal welfare and costs. While manyin vitromethods have been tested as possible alternatives to thein saccomethod to study rumen degradation of feeds, they were unable to remove the need to use fistulated animals to obtain rumen fluid. Although solubility, enzyme- and faeces-basedin vitromethods do not require rumen fluid, they still need data from either thein saccomethod or the rumen fluid-basedin vitromethods for comparison and validation. Therefore, there is a need to developin vitromethods that do not require the need to surgically modify ruminants to obtain rumen fluid to study rumen degradation. We review the potentials and problems associated with the existing methods to study rumen degradation and their implications for the animal industry in different situations.

Effects of source of starch on net portal flux of glucose, lactate, volatile fatty acids and amino acids in the pig

The ileal digestibilities of maize starch and native pea starch do not differ. However maize starch is digested faster than pea starch and the ileal amino acid digestibility of a diet containing pea starch is lower. In the present study, the net portal fluxes of glucose, lactate, volatile fatty acids (VFA) and amino acids were measured for diets including 650 g maize starch or pea starch/kg. The diets were fed at a level 870 kJ digestible energy/kg0.75 twice daily (06.00 and 18.00 hours) to four female pigs in a crossover design. Portal vein blood flow did not differ between maize and pea starches (1620 and 1484 ml/min respectively; SED 100; P = 0.23). For maize starch portal glucose flux was significantly higher during the first 6 h after feeding, was not different 8 h after feeding and was significantly lower thereafter. Net portal glucose flux was higher for maize starch than for pea starch (1759 and 1265 mmol/12 h respectively; SED 182; P = 0.054). Net portal lactate flux was not significantly different between maize and pea starches (36.5 and 67.2 mmol/12 h respectively; SED 24.1; P = 0.27) and net portal VFA flux was lower for maize starch than for pea starch (169 and 218 mmol/12 h respectively; SED 18; P = 0.054). Net portal fluxes of valine, isoleucine, phenylalanine, tryptophan, arginine, serine, cystine, tyrosine, lysine, histidine and the sum of essential amino acids tended to be or were higher (P < 0.1 or P < 0.05) and net portal flux of aspartic acid tended to be lower for pea starch (P < 0.1). It can be concluded that, although ileal digestibility of both starches is equal, the rate of appearance of glucose in the portal vein was higher for maize starch, influencing the net portal flux of amino acids.

Native corn starch versus either cellulose or glucose in the diet and the effects on apparent magnesium absorption in goats

The objective of this study was to determine whether dietary glucose or starch would reduce the inhibitory effect of high K intake on Mg absorption in ruminants. In a 6 x 6 Latin square design, six goats were fed diets with or without added KHCO3 containing either cellulose, glucose, or native corn starch. The K concentrations of the diets were 7.8 or 34.0 g or K/kg of dry matter, and carbohydrates were incorporated so that their concentrations were identical on a glucose equivalent basis (331 g of glucose/kg of dry matter). The intake of extra K significantly reduced apparent Mg absorption from 29.8 to 22.1% on average. Glucose, instead of cellulose, in the diet did not affect Mg absorption. Replacement of dietary cellulose by corn starch enhanced the mean efficiency of Mg absorption from 21.8 to 30.9%. Starch versus glucose increased Mg absorption by 5.8 percentage units. No statistically significant interaction was observed between the type of carbohydrate and the amount of K in the diet with regard to Mg absorption. This study showed that the inhibitory effect of dietary KHCO3 on Mg absorption in goats was fully counteracted by the replacement of cellulose with starch in the diet. Possible changes in the pH of ruminal fluid might have mediated the dietary effects on Mg absorption.