Nutritional strategies for minimizing phosphorus pollution from the livestock industry

Abstract Livestock manure traditionally has been considered and used as a valuable resource by farmers to improve crop production. Livestock manure is rich in nutrients (nitrogen (N) and phosphorus (P)) and thus has been land applied to enrich soils. But land application of manure nutrients in excess of crop requirements can lead to saturated soil and loss of nutrients to surface water via runoff. Environmental concerns with P from animal agriculture are significant because livestock manure has always been land applied to meet crops' N requirement, resulting in P application in excess of crops' P requirement. The problem is aggravated with the intensification of livestock production, and now animal agriculture has been identified as a primary source of water quality impairment in many regions. But intensification and continuous advancement of livestock production is required to meet the increasing demand of food supply to feed a growing global population. Therefore, management strategies are needed that will improve livestock production while supporting the environmental and social pillars of sustainability. Nutritional strategies are economically and environ mentally efficient tools to reduce P excretion by livestock. This chapter discusses nutritional strategies including precision feeding, phase feeding and approaches to improve feed P availability.</p

Effect of abomasal inorganic phosphorus infusion on phosphorus absorption in large intestine, milk production, and phosphorus excretion of dairy cattle

The objective of the study was to evaluate the effect of inorganic phosphorus (Pi) infusion on P absorption in large intestine, milk production and phosphorus excretion. Four ruminally- and ileally-cannulated crossbred cows were used in a 4×4 Latin Square with 21 d periods. Cows were fed a total mixed ration containing 0.21% P, providing 50% of the cows’ P requirement. Cobalt-EDTA (Co-EDTA) was used as marker to measure large intestine digesta flow. On d 13 to 21 of each period, each cow was infused daily with 0, 20.1, 40.2, or 60.3 g Pi into the abomasum and total collection was conducted on d 18 to 21. Ileal samples were collected every 9 h on d 18 to d 21. Feed, digesta, and fecal samples were analyzed for total P and Pi using the molybdovanadate yellow method and blue method, respectively. All data were analyzed using PROC GLIMMIX in SAS 9.3 using contrasts to evaluate linear, quadratic and cubic effects of Pi infusion dose. Dry matter (DM) intake, apparent DM digestibility, milk yield and milk total P were unaffected by Pi infusion. Ileal flow and fecal excretion of total P and Pi increased linearly with increasing infused Pi. In the large intestine, net absorption of TP and Pi were increased linearly with increasing infused Pi. The magnitude of absorption from the large intestine was greater than reflected in current models and raising questions that could be evaluated with longer infusion periods or dietary alteration

Excretion of Antibiotic Resistance Genes by Dairy Calves Fed Milk Replacers with Varying Doses of Antibiotics

Elevated levels of antibiotic resistance genes (ARGs) in soil and water have been linked to livestock farms and in some cases feed antibiotics may select for antibiotic resistant gut microbiota. The purpose of this study was to examine the establishment of ARGs in the feces of calves receiving milk replacer containing no antibiotics versus subtherapeutic or therapeutic doses of tetracycline and neomycin. The effect of antibiotics on calf health was also of interest. Twenty-eight male and female dairy calves were assigned to one of the three antibiotic treatment groups at birth and fecal samples were collected at weeks 6, 7 (prior to weaning), and 12 (5 weeks after weaning). ARGs corresponding to the tetracycline (tetC, tetG, tetO, tetW, and tetX), macrolide (ermB, ermF), and sulfonamide (sul1, sul2) classes of antibiotics along with the class I integron gene, intI1, were monitored by quantitative polymerase chain reaction as potential indicators of direct selection, co-selection, or horizontal gene transfer of ARGs. Surprisingly, there was no significant effect of antibiotic treatment on the absolute abundance (gene copies per gram wet manure) of any of the ARGs except ermF, which was lower in the antibiotic-treated calf manure, presumably because a significant portion of host bacterial cells carrying ermF were not resistant to tetracycline or neomycin. However, relative abundance (gene copies normalized to 16S rRNA genes) of tetO was higher in calves fed the highest dose of antibiotic than in the other treatments. All genes, except tetC and intI1, were detectable in feces from 6 weeks onward, and tetW and tetG significantly increased (P < 0.10), even in control calves. Overall, the results provide new insight into the colonization of calf gut flora with ARGs in the early weeks. Although feed antibiotics exerted little effect on the ARGs monitored in this study, the fact that they also provided no health benefit suggests that the greater than conventional nutritional intake applied in this study overrides previously reported health benefits of antibiotics. The results suggest potential benefit of broader management strategies, and that cost and risk may be avoided by minimizing incorporation of antibiotics in milk replacer

Enskog Theory for Polydisperse Granular Mixtures. I. Navier-Stokes order Transport

A hydrodynamic description for an $s$-component mixture of inelastic, smooth hard disks (two dimensions) or spheres (three dimensions) is derived based on the revised Enskog theory for the single-particle velocity distribution functions. In this first portion of the two-part series, the macroscopic balance equations for mass, momentum, and energy are derived. Constitutive equations are calculated from exact expressions for the fluxes by a Chapman-Enskog expansion carried out to first order in spatial gradients, thereby resulting in a Navier-Stokes order theory. Within this context of small gradients, the theory is applicable to a wide range of restitution coefficients and densities. The resulting integral-differential equations for the zeroth- and first-order approximations of the distribution functions are given in exact form. An approximate solution to these equations is required for practical purposes in order to cast the constitutive quantities as algebraic functions of the macroscopic variables; this task is described in the companion paper.Comment: 36 pages, to be published in Phys. Rev.

The Effect of Field Applications of Insecticides on Honey Bees

Reports of tests of new insecticides have tended to minimize the practical dangers to beekeeping when these toxicants are applied to crops in bloom. The idea is current that these insecticides are harmless to bees if applied during hours when bees are not on the field. An examination of one alfalfa-seed area, where bee losses from commercial applications were reported, prompted a more critical examination to determine the effect of field applications of these insecticides on bees. This paper is a report of field experiments near Logan. Utah, with early-morning applications of DDT, chlordane, parathion, and toxaphene to alfalfa in flower

Exposure to dairy manure leads to greater antibiotic resistance and increased mass-specific respiration in soil microbial communities

Intensifying livestock production to meet the demands of a growing global population coincides with increases in both the administration of veterinary antibiotics and manure inputs to soils. These trends have the potential to increase antibiotic resistance in soil microbial communities. The effect of maintaining increased antibiotic resistance on soil microbial communities and the ecosystem processes they regulate is unknown. We compare soil microbial communities from paired reference and dairy manure-exposed sites across the US. Given that manure exposure has been shown to elicit increased antibiotic resistance in soil microbial communities, we expect that manure-exposed sites will exhibit 1) compositionally different soil microbial communities, with shifts toward taxa known to exhibit resistance; 2) greater abundance of antibiotic resistance genes; and 3) corresponding maintenance of antibiotic resistance would lead to decreased microbial efficiency. We found that bacterial and fungal communities differed between reference and manure-exposed sites. Additionally, β-lactam resistance gene ampC was 5.2-fold greater under manure exposure, potentially due to the use of cephalosporin antibiotics in dairy herds. Finally, ampC abundance was positively correlated with indicators of microbial stress, and microbial mass-specific respiration, which increased 2.1-fold under manure exposure. These findings demonstrate that the maintenance of antibiotic resistance associated with manure inputs alters soil microbial communities and ecosystem function