X. Li

Influence of age on the apparent ileal amino acid digestibility of feed ingredients for broiler chickens

1. The apparent ileal digestibility of amino acids in 8 feed ingredients was determined using 14-, 28- and 42-d-old male broiler chickens. The ingredients included three cereals (wheat, sorghum and maize), one cereal by-product (mill run), three oilseed meals (canola, cottonseed and soybean meals) and one animal protein meal (meat and bone meal). 2. Dietary crude protein in the assay diets was supplied solely by the test ingredient. All diets contained 20 g/kg acid-insoluble ash as an indigestible marker, and each diet was offered ad libitum in mash form to 5 replicate pens from 11 to 14 d, 25 to 28 d and 39 to 42 d post-hatching. There were 12, 6 and 6 birds per pen for the 14, 28 and 42 d samplings, respectively. 3. The results suggest that the age of broilers significantly influenced the apparent ileal digestibility of amino acids. The effects, however, varied among amino acids and ingredients. 4. In wheat, the digestibility of most amino acids was higher in 14- than in 28- and 42-d-old broilers. In maize, the digestibility coefficients of amino acids were higher at 28 and 42 d than at 14 d. The digestibility coefficients in maize and wheat at 28 and 42 d were similar. The digestibility of amino acids in sorghum at 42 d was higher than those at 28 d, but similar to those at 14 d except for histidine, lysine, serine and glycine, which were significantly higher at 42 d. Digestibility of amino acids in sorghum was similar between 14 and 28 d except for isoleucine, leucine, phenylalanine, glutamic acid and alanine. The digestibility of amino acids in mill run at 42 d was significantly higher than those at 14 and 28 d. There were no differences in digestibility between 14 and 28 d. 5. In general, the digestibility of amino acids in canola meal, soybean meal and, meat and bone meal was higher at 28 and 42 d compared to those at 14 d, and similar between 28 and 42 d of age. In cottonseed meal, age had no effect on the digestibility coefficient of amino acids, except for lysine and arginine, which increased with age. 6. Analysis of the combined results for the 8 feed ingredients showed that, in general, the digestibility coefficients of amino acids increased with advancing age of broiler chickens.

Pest Responses to Odors From Predators Fed a Diet of Target Species Conspecifics and Heterospecifics

Abstract Research into the use of predator-odor–based repellents as a management tool has gained momentum during the past 30 years. Some studies have suggested that odors from a predator whose diet includes the target species are more effective than odors from a predator that does not consume the species. To evaluate this management tool in the Australian context and to determine the effect, if any, of predator diet on odor repellence, we tested eutherian and metatherian, predator fecal odors on phylogenetically separated pest species that currently occur in Australia. We evaluated fecal odors from tigers (Panthera tigris) and Tasmanian devils (Sarcophilus harrisii) as repellents for goats (Capra hircus) and eastern grey kangaroos (Macropus giganteus). We fed tigers and Tasmanian devils 2 diets: one of goat and one of eastern grey kangaroo. The test fecal odors were more effective than a control odor of carrier material and solvent at deterring goats (P < 0.001) and kangaroos (P  =  0.02) from food. Tiger fecal odor was more effective than Tasmanian devil odor in deterring both goats (P  =  0.001) and kangaroos (P  =  0.03). We observed a decrease in the number of feeding events for goats when they were exposed to the odor from a tiger fed goat compared with all other predator–diet combinations (P < 0.001). We also observed a decrease in feeding events for kangaroos when exposed to the odor from a tiger fed kangaroo compared with all other predator–diet combinations. We observed signs of desensitization to the test odors in goats and habituation to the test odors in kangaroos over the experimental period. A better understanding of the factors involved in desensitization and habituation may increase the effectiveness of fecal odor–based repellents as a humane and nonlethal management tool for managers.

Effects of a commercial dose of L‐tryptophan on plasma tryptophan concentrations and behaviour in horses

REASON FOR PERFORMING STUDY L-tryptophan is a common ingredient in equine calmative products, but its effectiveness has not been demonstrated in horses. HYPOTHESIS To determine whether a commercial dose of L-tryptophan increases plasma tryptophan and alters behaviour in horses fed a roughage or concentrate meal. METHODS L-tryptophan (6.3 g) or placebo (water) was administered per os in a cross-over design, to 12 Thoroughbred horses (503 +/- 12.1 kg bwt), just before a meal of lucerne hay or oats. Plasma tryptophan was measured by gas chromatography. Horse behaviour was observed in an empty enclosure, then in the presence of an unfamiliar person and a novel object. RESULTS Total plasma tryptophan increased 3-fold in both studies, peaking 1.5-2 h after dosing. After the peak, tryptophan remained high for several hours if the horses had been fed hay, but fell sharply if fed oats, consistent with the glycaemic responses to these meals. However, the ratio of tryptophan to 4 large neutral amino acids (phenylalanine, tyrosine, leucine and isoleucine) increased in the tryptophan-treated horses to a similar extent and for a similar duration, with both diets. The presence of a stranger or novel object increased heart rate (P<0.05), but caused no behavioural effects that were altered by tryptophan, regardless of the diet. CONCLUSIONS Plasma tryptophan increases when tryptophan is administered at a dose used in some commercial products, but this is not reflected by marked behavioural changes in the horse. POTENTIAL RELEVANCE Further work is required to refine behavioural tests and identify an effective dose of L-tryptophan in the horse.

Soluble arabinoxylan alters digesta flow and protein digestion of red meat-containing diets in pigs

OBJECTIVES The aim of this study was to investigate how a moderate increase in dietary meat content combined (or not) with soluble fibre would influence protein digestion as well as digesta characteristics and flow. METHODS Four groups of pigs were fed Western-style diets (high-protein/high-fat) containing two types of barbecued red meat, one with and one without a wheat arabinoxylan-rich fraction. After 4 wk, digesta samples were collected from small and large intestinal sites and analyzed for protein, amino acids, dry matter, and acid-insoluble ash. Tissue samples were also collected from each site. RESULTS Arabinoxylan consumption led to somewhat lower apparent protein digestibility within the small and large intestines as well as shorter mean retention times. This suggests that the lowered protein digestibility is due, at least partly, to shorter access time to digestive proteases and absorptive surfaces. Additionally, digesta mass was higher in pigs fed arabinoxylan while dry matter (%) was lower, indicating an increased digesta water-holding capacity due to the presence of a soluble dietary fiber. CONCLUSION Data showed that solubilized wheat arabinoxylan provides potential health benefits through decreased protein digestibility, increased digesta mass, and reduced mean retention time, even for diets with a moderately higher protein content. These factors are associated with efficiency of digestion and satiety, both of which have implications for prevention of obesity and other health disorders.

Phytase supplemented poultry diets affect soluble phosphorus and nitrogen in manure and manure-amended soil.

Understanding P and N dynamics in manure-amended soil is essential for estimating the environmental impact of manure utilization in land applications. A laboratory incubation study was conducted to assess, (i) the effect of feeding a standard Australian commercial diet, and diets modified with phytase supplementation and reduced nonphytase phosphorus (NPP), on the concentrations of P and N (total and soluble) in the manure derived from layer hens (Gallus domesticus L.), and (ii) the change in water-soluble phoshorus (P(WSP)) and mineral N (NH(4)-N and NO(3)-N) when used as a soil amendment, applied at rates equivalent to 200 kg ha(-1) (200N) and 400 kg ha(-1) (400N). Phytase supplementation increased %P(WSP) by 8 to 12% in the manures, regardless of the levels of NPP in the diets, and in the manure-amended soils by 27 to 30% at the 200N application rate, and up to 54% at the 400N rate. Phytase significantly (P < 0.05) reduced total nitrogen (TN) content (by 12-31%) of the manures but generally produced greater nitrate accumulation in the manure-amended soils. Net nitrification, which commenced 4 wk after incubation, was accompanied by a simultaneous decrease in soil pH (by one pH unit) and a concomitant decline in %P(WSP). The decline in %P(WSP) was primarily attributed to P retention by the soil as it became more acidic. This study suggests that phytase addition not only reduces manure total N content, and increases water-soluble P, but its effects on manure total phosphorus (TP) and 2 mol L(-1) KCl extractable mineral N is influenced by the NPP level in the diet.

Responses of IsaBrown laying hens to a pre-layer diet containing additional calcium and to dietary protein and lysine concentrations during lay

IsaBrown pullets were obtained from a commercial breeder at 15 (Expt 1) and 16 (Expt 2) weeks of age and housed in either single-bird or multiple 5-bird cages in a high rise, windowless layer house in which temperatures were maintained below 30˚C by computerised control of fans and evaporative cooling pads. In Expt 1, they were fed either a grower diet or a pre-layer diet consisting of the grower diet containing additional calcium to 18 weeks of age and then maintained during lay to 56 weeks of age on diets containing either 160 or 180 g crude protein (CP)/kg. In Expt 2, they were fed the grower diet to 19 weeks of age and then 1 of 5 diets similar in all ingredients except that the lysine concentration varied between 7.35 and 8.95 g/kg in increments of 0.4 g/kg. The L-lysine HCl supplements were added in lieu of solka floc, an inert cellulose supplement. In Expt 1, mortality was low (2.25%), peak egg production was high (95–98%), and the mean rate of lay at 56 weeks of age was above 88%. The diet fed prior to lay had no significant effect on production during lay. Feed intake and egg production were similar for hens fed both dietary protein levels during lay, and egg weight and egg mass output were greater for hens fed the diet containing 180 g CP/kg. Hens in multiple-bird cages ate significantlyless feed for a significantly smaller daily egg mass output. In Expt 2, increasing the dietary lysine concentration significantly reduced feed intake and significantly increased lysine intake, egg shell breaking strength, and albumen height. Multiple-caged hens had a significantly lower hen-housed egg production as a result of a 7-fold increase in mortality compared with hens in single cages, due mainly to cannibalism. The daily lysine requirement formaximum egg production approximated 940 mg for hens in single cages and 975 mg for hens in multiple-bird cages.

Agronomic characteristics of annual Trifolium legumes and nutritive values as predicted by near-infrared reflectance (NIR) spectroscopy

A range of annual legume genotypes comprising one line of Trifolium subterraneum, four lines of T. michelianum, 11 of T. resupinatum var. resupinatum, and one line of T. resupinatum var. majus were grown in glasshouses under temperature regimes of 10-15 degrees C and 16-21 degrees C. Dry matter (DM) weights of stem, leaf, and flower tissues were measured when plants had six nodes, at first flower appearance, and at senescence. All samples were scanned by near-infrared reflectance spectroscopy (NIRS). One-third of the samples, covering the range of spectral characteristics, were analysed for in vitro digestible organic matter (DOMD), organic matter, crude protein (CP), neutral detergent fibre (NDF), lignin, cellulose, and the hemicellulosic polysaccharide monomers arabinose, xylose, mannose, galactose, and rhamnose. These data were used to develop calibration equations from which the composition of the remaining samples was predicted by NIRS. The higher temperature resulted in plants reaching respective phenological stages earlier, but did not affect either DM yields of total plant, stem, leaf, and petiole tissues or the proportions of each fraction. In vitro DOMD and arabinose and galactose levels decreased, while lignin, cellulose, NDF, xylose, mannose, and rhamnose levels increased with advancing maturity. In vitro DOMD was positively associated with contents of CP, arabinose, galactose, and the arabinose/xylose ratio and was negatively associated with contents of lignin, cellulose, NDF, xylose, mannose, and rhamnose. Lignin contents were highly correlated with levels of both xylose and mannose. Stems were more digestible than leaves in subterranean clover and T. resupinatum var. majus. The study also demonstrated that NIRS can be used routinely as a quick, inexpensive, and reliable laboratory technique to predict feed components of annual Trifolium legumes.

Chemical composition and nutritive value of mature annual legumes for sheep

Abstract This study reports on the chemical composition and nutritive value of three mature annual legumes: subterranean clover (Trifolium subterraneum, cv. ‘Junee’), Persian clover (Trifolium resupinatum, cv. ‘Kyambro’) and a medic (Medicago murex, cv. ‘Zodiac’). Nitrogen digestibility of Persian clover cv. ‘Kyambro’ in the whole tract was significantly lower than that of the other legumes, although it had the highest nitrogen content. This difference was attributable largely to differences in the digestion of non-fibre nitrogen. Differences in hemicellulose digestibility were also noted. Xylose was the least digestible sugar in all three legumes. Mannose and galactose contents were highest in ‘Kyambro’ and digestibility of these sugars was substantially lower than in the other two legumes. Crossover measurements in situ indicated that components of ‘Kyambro’, possibly galacto-mannans, inhibited rumen fermentation of all three legumes. Concentrations of Ca, P, Mg, K, Na, S, Fe, Cu, Mn and Zn in all legumes were adequate for growth in sheep. In terms of dry matter and nitrogen digestibility, the three legumes were ranked in the descending order: subterranean clover cv. ‘Junee’ > medic cv. ‘Zodiac’ > Persian clover cv. ‘Kyambro’.

Calcium and phosphorus metabolism and nutrition of poultry: are current diets formulated in excess?

Calcium (Ca) and phosphorus (P) are important nutrients in poultry diet formulations. In the present review, we discuss recent advances in our understanding of the metabolism of Ca and P in poultry. Recent data are provided in support of the proposition that current poultry diets are formulated in excess for Ca and P. The quantities of Ca and P available for metabolism reflect rates of intestinal absorption, bone accretion and resorption, glomerular filtration, renal tubular reabsorption, and intestinal endogenous losses. Ca and P homeostasis is largely under endocrine control. Parathyroid hormone and the hormonal form of vitamin D-3 are the two hormones credited with this role. However, a novel hormonal axis involving Fibroblast Growth Factor 23 and Klotho has been recently delineated, which, in conjunction with parathyroid hormone and vitamin D-3, tightly regulates Ca and P homeostasis. Recent studies have suggested that current commercial diets for both broilers and layers contain excess Ca and P, the content of which could be reduced without affecting production or bird welfare. The challenge in reducing Ca and P concentrations in poultry diets is the uncertainty about what concentrations of Ca and P can be fed without compromising bird welfare. This is because there are limited data on the available P and Ca concentrations in poultry feedstuffs determined biologically. This is further complicated by the need for agreement on evaluation systems for evaluation of Ca and P bioavailability. We conclude that direct ileal or pre-caecal digestible Ca and P values are preferred.

Randomised clinical trial on the effect of a single oral administration of l-tryptophan, at three dose rates, on reaction speed, plasma concentration and haemolysis in horses.

Tryptophan (TRP) is marketed as a calmative for horses despite reservations about its efficacy. The aim of this study was to measure the effect of oral TRP administration on the reaction speed of horses. Sixty mature horses were used in a two stage randomised, blind, cross-over study, receiving a placebo and an oral dose of TRP (30, 60 or 120 mg/kg body weight), before undergoing a reaction speed test. Blood samples were taken up to 96 h after TRP administration, to identify signs of acute haemolytic anaemia. Plasma TRP concentrations were increased (P <0.001) by the administration of TRP paste. However, TRP had no effect on the reaction speed of horses when startled. There was no evidence of alterations in clinical pathology parameters in 432 blood samples. While the safety of these doses of TRP can be confirmed, there was no evidence to suggest that a single dose of TRP is an effective calmative for horses.