Correcting the calculation of extent of degradation to account for particulate matter loss at zero time when applying the polyester bag method

The established calculation of ruminal extent of degradation using the polyester bag method overestimates extent. The wash fraction, at least in part, is subject to losses from the rumen due to passage. Four formulae are proposed to minimize this risk of overestimation. Four options are considered: 1) passage losses for particulate matter escaping from the bag at zero time are according to the particulate fractional passage rate, 2) the liquid rate, and 3) the average of the two, and additionally 4) there is no instantly degradable fraction. The established and proposed formulae were examined using polyester bag data for six forages: grass silage, fresh ryegrass, fresh white clover, alfalfa hay, mixed grasses hay, and hay from a permanent mountain meadow. The established formula gave appreciably higher estimates of extent of degradation in all cases. Overestimation was at least 6.9, 4.9, 2.9, 2.1, 2.4, and 4.5%, respectively, for the six forages.     

Effects of condensed tannins on established populations and on incoming larvae of Trichostrongylus colubriformis and Teladorsagia circumcincta in goats

The use of tanniferous plants or tannins represents one alternative approach to the control of gastrointestinal parasites in ruminants but most data have been obtained in sheep. The current study was therefore performed in goats with two objectives: firstly, to investigate the effects of condensed tannins (CT) on adult populations of Trichostrongylus colubriformis and Teladorsagia circumcincta; secondly, to examine their effects on the establishment of infective larvae of these two species. In experiment 1, two groups of kids were infected with 6 000 L3 of T. colubriformis and 6 000 L3 of T. circumcincta. After 7 weeks, quebracho extracts were administered per os for 8 days to one group. A comparable group which did not receive tannins was included as the control. The kids were slaughtered on week 11. Parasitological and pathophysiological parameters were measured weekly. Worm counts were assessed and mast cells, globule leukocytes and eosinophils were counted in the abomasal and intestinal mucosae. Tannin administration was associated with a decrease in egg excretion, and a decrease in female fecundity, but with no changes in worm numbers. These changes were associated with an increased number of intestinal mast cells. In experiment 2, 24 goats were used according to a 2 x 2 factorial design, depending on infection and tannin administration. Two groups were either infected with 6 000 L3 of T. colubriformis or T. circumcincta. Within each group, the goats were either drenched or undrenched with tannin extracts. Pathophysiological parameters were measured weekly. Twelve days after the cessation of tannin administration, the goats were slaughtered. Worm counts and female worm fecundity were determined. Tannin consumption was associated with a significant reduction (P < 0.01) of Trichostrongylus populations and a close to significant reduction for Teladorsagia. No effect on fecundity was observed. Our results (1) confirm the consequences of condensed tannins on nematodes in goats as in sheep and (2) indicate divergent effects depending on the parasitic stage exposed to the condensed tannins.     

The effect of energy supplementation on nitrogen utilization in lactating dairy cows fed grass silage diets

An experiment was conducted to examine the effect that various isoenergetic diets, containing different quantities of soluble carbohydrate and fiber and different types of starch, have on nitrogen (N) balances. Six lactating dairy cows in early to midlactation consuming grass silage diets with not less than 600 g/kg total DMI as forage were used in the experiment. Four concentrates were prepared that had higher amounts of either fiber, soluble sugars, corn (low degradable starch source), or barley (high degradable starch source). Overall N utilization by the cows was poor, rarely exceeding 0.30 g milk N/g of dietary N intake. Fecal N outputs accounted for more than half of total N excreted in all treatments except for diets supplemented with high degradable starch, in which urinary N excretion was significantly higher compared with the other treatments. Milk yield was unaffected by concentrate type, averaging 19.9 kg/d, but milk protein content decreased from 32.9 for starch-based diets to 30.9 and 30.0 g/kg for the soluble sugar- and fiber-based diets, respectively. The efficiency of N utilization improved in the low degradable starch treatment, which had lower N excretion (65%) and higher protein concentration in milk. Furthermore, feeding cows corn-based concentrates reduced urinary N excretion by almost 30% compared with barley-based concentrates; therefore, feeding corn-based diets is recommended for the reduction of nitrogen pollution in lactating dairy cows.     

A kinetic model of phosphorus metabolism in growing goats

The effect of increasing phosphorus (P) intake on P utilization was investigated in balance experiments using 12 Saanen goats, 4 to 5 mo of age and weighing 20 to 30 kg. The goats were given similar diets with various concentrations of P, and 32P was injected to trace the movement of P in the body. A P metabolism model with four pools was developed to compute P exchanges in the system. The results showed that P absorption, bone resorption, and excretion of urinary P and endogenous and fecal P all play a part in the homeostatic control of P. Endogenous fecal output was positively correlated to P intake (P < .01). Bone resorption of P was not influenced by intake of P, and P recycling from tissues to the blood pool was lesser for low P intake. Endogenous P loss occurred even in animals fed an inadequate P diet, resulting in a negative P balance. The extrapolated minimum endogenous loss in feces was .067 g of P/d. The minimum P intake for maintenance in Saanen goats was calculated to be .61 g of P/d or .055 g of P/(kg(.75) x d) at 25 kg BW. Model outputs indicate greater P flow from the blood pool to the gut and vice versa as P intake increased. Intake of P did not significantly affect P flow from bone and soft tissue to blood. The kinetic model and regressions could be used to estimate P requirement and the fate of P in goats and could also be extrapolated to both sheep and cattle.     

Rescue of dystrophic muscle through U7 snRNA-mediated exon skipping

Most mutations in the dystrophin gene create a frameshift or a stop in the mRNA and are associated with severe Duchenne muscular dystrophy. Exon skipping that naturally occurs at low frequency sometimes eliminates the mutation and leads to the production of a rescued protein. We have achieved persistent exon skipping that removes the mutated exon on the dystrophin messenger mRNA of the mdx mouse, by a single administration of an AAV vector expressing antisense sequences linked to a modified U7 small nuclear RNA. We report the sustained production of functional dystrophin at physiological levels in entire groups of muscles and the correction of the muscular dystrophy.     

Understory plant diversity and biomass in hybrid poplar riparian buffer strips in pastures

Understory plant biomass, species richness and canopy openness were measured in six-year old hybrid poplar riparian buffer strips, in the understory of two unrelated clones (MxB-915311 and DxN-3570), planted along headwater streams at three pasture sites of southern Quebec. Canopy openness was an important factor affecting understory biomass in hybrid poplar buffers, with lower understory biomass observed on sites and under the clone with lower canopy openness. Although tree size was an important factor affecting canopy openness, relationships between total stem volume and canopy openness, for each clone, also support the hypothesis of a clonal effect on canopy openness. Understory biomass and canopy openness as low as 3.6 g m⁻² and 7.6% in 1 m² microplots were measured under clone MxB-915311 at the most productive site. This reduction of understory plant growth could compromise important buffer functions for water quality protection (runoff control, sediment trapping and surface soil stabilisation), particularly were concentrated runoff flow paths enter the buffer. On the other hand, tree buffers that maintain relatively low canopy openness could be interesting to promote native and wetland plant diversity. Significant positive relationships between canopy openness and introduced species richness (R ² = 0.46, p < 0.001) and cover (R ² = 0.51, p < 0.001) were obtained, while no significant relationship was observed between canopy openness and native (wetland) species richness and cover. These results suggest that planting riparian buffer strips of fast-growing trees can rapidly lead to the exclusion of shade-intolerant introduced species, typical colonisers of disturbed habitats such as riparian areas of pastures, while having no significant effect on native (wetland) diversity. Forest canopy created by the poplars was probably an important physical barrier controlling introduced plant richness and abundance in agricultural riparian corridors. A strong linear relationship (R ² = 0.73) between mean total species richness and mean introduced species richness was also observed, supporting the hypothesis that the richest communities are the most invaded by introduced species, possibly because of higher canopy openness, as seen at the least productive site (low poplar growth). Finally, results of this study highlight the need for a better understanding of relationships between tree growth, canopy openness, understory biomass and plant diversity in narrow strips of planted trees. This would be useful in designing multifunctional riparian buffer systems in agricultural landscapes.     

Modeling the efficiency of phosphorus utilization in growing pigs

Microbial phytase has been used to reduce P excretion from swine to mitigate environmental pollution. The objective of the study was to quantify the effect of feeding a low-P phytase-supplemented diet on growth and P utilization in growing pigs using mathematical models. A total of 20 weaned piglets (BW = 6.5 kg) housed in metabolism cages were randomly assigned to a standard diet (STD) or P-amended diet containing reduced P content and supplemented with phytase (AMN) with 10 pigs/diet. Body weight and feed consumption were recorded weekly so complete growth and cumulative P intake (cPI) curves could be modeled. A function with fixed point of inflexion (Gompertz) and a variable point of inflexion (generalized Michaelis-Menten) were considered in determining bioequivalence by analyzing BW vs. age relationships, whereas the monomolecular function was used to describe BW vs. cPI. All functions were incorporated into a nonlinear mixed effects model, and a first-order autoregressive correlation structure was implemented to take into account repeated measures. There was no difference between the 2 groups in final BW when the Gompertz equation was fitted (176 vs. 178 kg with SE of 7 kg for the STD and AMN, respectively) or the rate parameter (0.0140 vs. 0.0139 with SE of 0.0004 for the STD and AMN, respectively). The generalized Michaelis-Menten equation also showed a similar trend. When BW was expressed as a function of cPI the derivative with respect to cPI represented P efficiency, so it was possible to analyze the expected difference of the 2 diets in using P for BW gain and express it as a continuous function of cPI. The analysis showed through the entire growth period the difference in P efficiency was different from zero. On average, 56 g of supplemented inorganic P was consumed by a pig fed the AMN to reach market weight. In contrast, 309 g of supplemented inorganic P was consumed by the group fed the STD to reach similar BW. It would depend on other factors, but feeding pigs the AMN can result in economic benefit. Pigs fed the AMN excreted 19% less P compared with those fed the STD. In conclusion, nonlinear mixed model analysis (with repeated measures) was suitable for growth and efficiency analysis and showed that pigs fed the AMN consumed less than 20% of the inorganic P and performed as well as those fed the traditional inorganic P supplemented diet. The implications for mitigating P pollution, especially in areas where P loading is already problematic, are substantial.     

The prevalence of intestinal parasites in dogs and cats in Calgary, Alberta

The prevalence of endoparasites was evaluated in 619 dogs and 153 cats in the Calgary, Alberta region. Both homed and shelter-sourced pets were evaluated, and prevalence was assessed in various age groups. The overall endoparasite prevalence was 16.5% in canine samples and 7.2% in feline samples. The most common intestinal parasites in dogs were Giardia (8.1%) and ascarids (4.2%). The most common feline endoparasite was ascarids (6.5%). This study will help veterinarians to better plan diagnostic and preventative strategies with regard to companion animal intestinal parasites.