Intake, live-weight gain and carcass characteristics of beef cattle given diets based on forage maize silage harvested at different stages of maturity

Advancing maturity of forage maize is associated with increases in the proportion of dry matter (DM) and starch, and decreases in the proportions of structural carbohydrates in the ensiled crop. This experiment investigated the effects of three maize silages of 291 (low), 339 (medium) and 393 (high) g DM per kg fresh weight on the performance of 48 Simmental. Holstein-Friesian cattle. Equal numbers of steers (mean start weight = 503 (s.d. 31.3) kg) and heifers (mean start weight = 378 (s.d. 11.2) kg) were offered individually isonitrogenous diets composed of the three silages plus a protein supplement with minerals once daily until slaughter at the target live weight of 575 and 475 kg for steers and heifers, respectively. Intake was reduced on the low diet (P < 0.01) compared with the other two treatments. Dietary starch intake increased by a total of 1 kg/day between low and medium diets but by only 0.2 kg/day between medium and high diets. Unlike starch intake, total neutral-detergent fibre intake showed no significant difference (P > 0.05) between diets. There were no differences in live-weight gain between treatments but differences (P < 0.05) in food conversion efficiency indicated relative gains of 115, 100 and 102 g gain per kg DM intake for diets low, medium and high, respectively. There were no differences between diets in carcass weights, fat score and overall conformation.

Phoretic mites associated with animal and human decomposition

Phoretic mites are likely the most abundant arthropods found on carcases and corpses. They outnumber their scavenger carriers in both number and diversity. Many phoretic mites travel on scavenger insects and are highly specific; they will arrive on a particular species of host and no other. Because of this, they may be useful as trace indicators of their carriers even when their carriers are absent. Phoretic mites can be valuable markers of time. They are usually found in a specialised transitional transport or dispersal stage, often moulting and transforming to adults shortly after arrival on a carcase or corpse. Many are characterised by faster development and generation cycles than their carriers. Humans are normally unaware, but we too carry mites; they are skin mites that are present in our clothes. More than 212 phoretic mite species associated with carcases have been reported in the literature. Among these, mites belonging to the Mesostigmata form the dominant group, represented by 127 species with 25 phoretic mite species belonging to the family Parasitidae and 48 to the Macrochelidae. Most of these mesostigmatids are associated with particular species of flies or carrion beetles, though some are associated with small mammals arriving during the early stages of decomposition. During dry decay, members of the Astigmata are more frequently found; 52 species are phoretic on scavengers, and the majority of these travel on late-arriving scavengers such as hide beetles, skin beetles and moths. Several species of carrion beetles can visit a corpse simultaneously, and each may carry 1-10 species of phoretic mites. An informative diversity of phoretic mites may be found on a decaying carcass at any given time. The composition of the phoretic mite assemblage on a carcass might provide valuable information about the conditions of and time elapsed since death.

A cost-effective high-throughput digital system for observation and acquisition of animal behavioral data

We have designed and implemented a low-cost digital system using closed-circuit television cameras coupled to a digital acquisition system for the recording of in vivo behavioral data in rodents and for allowing observation and recording of more than 10 animals simultaneously at a reduced cost, as compared with commercially available solutions. This system has been validated using two experimental rodent models: one involving chemically induced seizures and one assessing appetite and feeding. We present observational results showing comparable or improved levels of accuracy and observer consistency between this new system and traditional methods in these experimental models, discuss advantages of the presented system over conventional analog systems and commercially available digital systems, and propose possible extensions to the system and applications to nonrodent studies.

Organic pollutants in animal products

It is necessary to assess the contamination of animal products by pollutants in order to protect human health. This can be achieved by understanding the processes whereby contaminants are introduced into the food chain. Such contamination can arise from the atmospheric deposition on to crops and soil or via contaminated feed. These processes are described and quantified with particular reference to the deposition of organic pollutants onto pasture. The transfer of the contaminants from the fodder and feed to the animal is also described. Finally, these processes are put in context by the illustration of how they are used in regulatory exposure models.

Phosphorus sorption and availability in soils amended with animal manures and sewage sludge

Soils that receive large applications of animal wastes and sewage sludge are vulnerable to releasing environmentally significant concentrations of dissolved P available to subsurface flow owing to the gradual saturation of the soil's P sorption capacity. This study evaluated P sorption (calculated from Langmuir isotherms) and availability of P (as CaCl2-P and resin P) in soils incubated for 20 d with poultry litter, poultry manure, cattle slurry, municipal sewage sludge, or KH2PO4, added on a P-equivalent basis (100 mg P kg(-1)). All the P sources had a marked negative effect on P sorption and a positive effect on P availability in all soils. In the cattle slurry- and KH2PO4- treated soils, the decreases in P sorption maximum (19-66%) and binding energy (25-89%) were consistently larger than the corresponding decreases (7-41% and 11-30%) in poultry litter-, poultry manure-, and sewage sludge-treated soils. The effects of cattle slurry and KH2PO4 on P availability were, in most cases, larger than those of the other P sources. In the poultry litter, poultry manure, and sewage sludge treatments, the increase in soil solution P was inversely related (R-2 = 0.75) to the input of Ca from these relatively high Ca (13.5-42 g kg(-1)) sources. Correlation analyses implied that the magnitude of the changes in P sorption and availability was not related to the water-extractable P content of the P sources. Future research on the sustainable application of organic wastes to agricultural soils needs to consider the non-P- as well as P-containing components of the waste.

Differences in phosphorus retention and release in soils amended with animal manures and sewage sludge

Excessive levels of P in agricultural soils pose a threat to local water quality. This study evaluated (i) time-dependent changes in soil P sorption (expressed as a phosphorus sorption index, PSI) and P availability (as resin P) during incubation (100 d) with poultry litter, cattle slurry, sewage sludge, or KH2PO4, added on a P-equivalent basis (100 mg P kg(-1)), and (ii) the subsequent kinetics of P release, measured by repeated extractions with a mixed cation-anion exchange resin. Soil exchangeable Ca and ammonium oxalate-extractable Fe and Al were also determined at 100 d of incubation. The small decrease in P sorption in the litter and sludge treatments (25%), compared with that in the slurry and KH2PO4 treatments (52%) between 20 and 100 d of incubation was attributed partly to the formation of new adsorption sites for P. Subsequent P release was described by a power equation: Resin P = a(extraction number)(b), where the constants a and b represent resin P obtained with a single extraction and the rate of P release per resin extraction, respectively. On average, the rate of P release decreased in the order: KH2PO4 and slurry > litter > sludge, and was inversely related to exchangeable Ca content of the incubated soils (R-2 = 0.57). The slower rates of P release in the litter and sludge treatments (P < 0.001) are attributed to the large values for exchangeable Ca (1050-2640 and 1070-2710 mg kg(-1), respectively) in these amended soils. Future research concerned with short-term declines in environmentally harmful levels of P in recently amended soils should consider the differential effects of the amendments on soil P dynamics.

Dissolution of phosphorus from animal bone char in 12 soils

Heat-treated animal bone char (ABC) has not previously been evaluated for its potential as a phosphorus (P) fertilizer. ABC, Gafsa phosphate rock (GPR) and triple superphosphate fertilizer (TSP) were incubated in 12 soils. Dissolved-P was assessed by extraction with NaOH and bioavailability with the Olsen extractant. The rate of P dissolution from ABC was described almost equally well by the Elovich and Power equations. After 145 days, the fraction of P dissolved ranged from 0 to 73% and to 56% for ABC and GPR, respectively. The most important soil properties determining P dissolution from ABC were pH and P sorption. P dissolution was not significant at soil pH > 6.1 (ABC) and > 5 (GPR) and the lower the pH, the greater the Dissolved-P. Dissolved-P also correlated positively and significantly with inorganic P sorption, measured by the Freundlich isotherm and the P sorption index of Bache and Williams (1971). Soil pH and P sorption index could be combined in multiple regression equations that use readily measured soil properties to predict the potential for ABC dissolution in a soil. Dissolution of P from GPR correlated with soil pH and exchangeable acidity. In comparison with GPR, ABC was a better source of available P, assessed by Olsen-P. In most soils, ABC increased Olsen-P immediately after application, including soils of relatively high pH in which GPR was ineffective. ABC is a P fertilizer of solubility intermediate between GPR and TSP.

Intake, growth and meat quality of steers given diets based on varying proportions of maize silage and grass silage

Simmental × Holstein-Friesian steers were offered four forage diets. These comprised grass silage (G); proportionately 0·67 grass silage, proportionately 0·33 maize silage (GGM); 0·33 grass silage, 0·67 maize silage ( MMG); maize silage ( M) from 424 (s.d. = 11·5) kg to slaughter at a minimum weight of 560 kg. Forages were mixed and offered ad libitum. Steers were offered 2 kg of a concentrate daily, the concentrate being formulated such that all steers had similar crude protein intakes across dietary treatments. A sample of steers was slaughtered at the beginning of the experimental period to allow the calculation of the rate of gain of the carcass and its components. Carcass dissection of a sample of steers allowed the development of a prediction equation of carcass composition based on thoracic limb dissection of all carcasses. Forage dry matter intake and live-weight gain increased linearly as maize silage replaced grass silage in the forage mixture, resulting in improvements in food conversion ratio (all P = 0·001). Killing-out proportion increased with maize silage inclusion ( P < 0·001) but fat and conformation scores did not differ significantly between diets. However, increasing maize inclusion in the diet resulted in a greater weight ( P = 0·05) and proportion ( P = 0·008) of fat in the carcass, and significant increases in internal fat deposition. The inclusion of maize led to a progressive increase in the daily gains of carcass ( P < 0·001), and significant increases in the daily gains of both fat ( P < 0·001) and lean tissue ( P < 0·001). Fat colour was more yellow in cattle given diets G and GGM than diets MMG and M ( P < 0·001) and colour intensity was lower on diet M than the other three diets ( P < 0·001). There were no significant differences in any aspects of eating quality between diets. Therefore, maize silage has the potential to reduce the time taken for finishing beef animals to achieve slaughter weight with no apparent detrimental effects on subsequent meat quality.