High perennial ryegrass seeding rates do not negatively impact pasture sward persistence

Poor persistence of perennial ryegrass swards is a common problem; however, there is a lack of long‐term studies to understand the mechanisms associated with poor persistence. This study describes an experiment to test the hypothesis that high ryegrass seeding rates (>18 kg seed per ha) reduce long‐term population persistence because of smaller plant size and poorer survival during the first year after sowing. Four cultivars, representing four functional types of perennial ryegrass, were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed per ha) with white clover in three regions of New Zealand. Swards were monitored for 5 years. No evidence was found to indicate a lack of persistence of ryegrass‐based swards sown at higher seeding rates. During the first year, swards sown at higher seeding rates had greater herbage accumulation (except at the Waikato site), greater ryegrass tiller density and greater ryegrass content. This initial impact of high seeding rates had largely dissipated by the fourth year, resulting in swards with similar annual herbage accumulation, tiller density and botanical composition. Similarly, there were relatively few differences among cultivars for these variables. Although high seeding rates did not negatively impact sward persistence, geographical location did, with strong evidence of ryegrass population decline at the Waikato site for all treatment combinations, some decline in Northland, and stable populations in Canterbury. It is possible that productive perennial ryegrass pastures can only be sustained for 4–5 years in some situations, even when the best ryegrass technology and management practices are used.     

The efficacy of systemically administered anti-arthritic drugs in an induced equine carpitis model

The efficacy of two systemically administered drugs for the treatment of equine joint injuries was assessed in a randomized blinded trial using the chemically induced equine carpitis model previously used to determine the dose and efficacy of both products. After a 10-day acclimation period, carpitis was induced by intracarpal injection of Complete Freund's Adjuvant (CFA) in twenty mature horses free of clinical and radiographic evidence of synovitis or DJD. Five days after model induction, the horses were stratified based on lameness evaluation and randomly assigned to 2 groups of 10 horses each.Parameters evaluated included lameness score, maximum range of carpal flexion, carpal circumference, stride length, and synovial fluid protein. These parameters were measured prior to model induction, 5 days after model induction (immediately prior to initial treatment) and once weekly for 6 weeks. Radiographs of the carpus were taken prior to model induction and 6 weeks. after treatment began. Treatment began 5 days after model induction. One group of 10 horses received 40 mg sodium hyaluronate by intravenous injection weekly for 3 weeks and the other group of 10 horses received intramuscular injections of 500 mg PSGAG every 4 days for 7 treatments.Both treatment groups showed significant improvement from pretreatment baseline values (based upon percent recovery to normal pre-model induction values) for lameness score, stride length and maximum carpal flexion (p<0.05) at each post treatment evaluation. The PSGAG treated group had significant improvement in synovial fluid protein at post treatment weeks 2 and 3. The improvement (percent recovery) in the PSGAG treated group was significantly (p<0.05) better than that of the intravenous sodium hyaluronate treated group for stride and flexion at post treatment weeks 1 through 6, for lameness score at post treatment weeks 1 through 3 and for carpal circumference at post treatment week 4.Both intravenous sodium hyaluronate and intramuscular PSGAG induced significant improvement in clinical lameness parameters; intramuscular PSGAG yielded consistently better results in this experimental model.     

Lactational performance of Quackenbush Swiss line 5 mice

We evaluated 2 strains of mice for their utility in the investigation of nutritional and molecular regulatory mechanisms of lactation. The lactational performance and milk composition were characterized for an inbred mouse strain, inbred Quackenbush Swiss line 5 (QSi5) selected persistently for fecundity, and a nonselected strain, CBA. The milk yield assessed by changes in BW in response to suckling of sustainable litter sizes for each strain was 3-fold greater (P < 0.001) in QSi5 mice than the CBA strain. The QSi5 mice also produced milk more efficiently (P < 0.001) than CBA mice, despite having the same quantity of mammary tissue per unit of BW. Milk composition did not vary between strains or by stage of lactation, with the exception of lactose concentration, which was greater (P = 0.003) in QSi5 mice. Expression of epsilon-casein was > or = 10-fold greater, and alpha(S1)-casein was > or = 3-fold greater, during mid and late lactation compared with early lactation in both strains, whereas kappa-casein underwent an apparent alteration in posttranslational modifications in both strains from early to mid lactation. Changes in casein composition coincided with an increased susceptibility to proteolytic degradation; hence milk from early lactation may be more readily degraded to facilitate digestion in the neonate. The greater milk synthetic capacity of QSi5 mice over the lactation cycle provides a useful model for studies of nutritional and molecular regulation of lactation.     

Efficacy of Intramuscular Chondroitin Sulfate and Compounded Acetyl-d-Glucosamine in a Positive Controlled Study of Equine Carpitis

Thirty healthy lameness-free horses were subjected to the Complete Freund's Adjuvant (CFA) (Sigma, St Louis, Mo) carpitis model, which was allowed to develop for 5 days. The horses were then stratified by model-induced deficit in lameness score, carpal flexion, stride length, and carpal circumference, and they were randomly assigned to 3 groups of 10 horses. The horses were treated with one of 3 treatments beginning on day 5: Group A (positive control) received PSGAG (Adequan, Luitpold Pharmaceuticals, Inc, Shirley, NY); Group B received a compounded solution of acetyl-d-glucosamine (Red Cross Drug, Blanchard, Okla); and Group C received a solution of chondroitin monosulfate (Chondroprotec, Neogen Corp, Lexington, Ky). All horses received the treatments by intramuscular injection every 4 days for 4 weeks and all doses were 500 mg/5 mL. On days 12, 19, 26, and 33, the primary outcome measures were taken for lameness score, carpal flexion, stride length, and carpal circumference. The study was blinded because the clinician evaluating the outcome measures was unaware of the treatment group assignments. The group means for percent recovery of model-induced deficits in these parameters was subjected to statistical analysis.PSGAG was significantly (P < .05) more effective in the recovery of model-induced deficits in all parameters than were chondroitin and glucosamine injectable solutions, and there was no significant difference between the 2 test drugs. In this test system, these 2 compounds, often sold as “generic” versions of PSGAG, were significantly less effective than PSGAG.     

Effects of microcosm scaling and food resources on growth and survival of larval Culex pipiens

Background  

We used a simple experimental design to test for the effects of microcosm scaling on the growth and survival of the mosquito, Culex pipiens. Microcosm and mesocosm studies are commonly used in ecology, and there is often an assumption that scaling doesn't affect experimental outcomes. The assumption is implicit in the design; choice of mesocosms may be arbitrary or based on convenience or cost. We tested the hypothesis that scale would influence larvae due to depth and surface area effects. Larvae were predicted to perform poorly in microcosms that were both deep and had small openings, due to buildup of waste products, less exchange with the environment, and increased competition. To determine if the choice of scale affected responses to other factors, we independently varied leaf litter quantity, whose effects on mosquitoes are well known.     

Effect of diet on preweaning performance of Sahiwal calves

The objective was to study the growth potential of Sahiwal calves given milk or milk replacer with or without concentrates. For this purpose, forty-eight Sahiwal calves were divided into four groups of 12 animals each with equal sex ratio. In each group, the calves were offered either milk or a milk replacer (MR) at a rate of 10% of their body weight adjusted weekly. In addition to this, calves were fed either a starter ration plus Egyptian clover hay (SR + H) or hay only (H) until the end of trial. The milk or MR was withdrawn gradually from day 56 until animals were weaned completely by day 84. Calves offered milk grew faster than those offered MR (357 ± 9 vs. 162 ± 9 g/day; p < 0.05) and displayed higher weaning weights (51.6 ± 0.8 vs. 35.2 ± 0.8 kg; p < 0.05). The calves offered SR + H grew faster (311 ± 9 vs. 208 ± 9 g/day; p < 0.05) and displayed higher weaning weights (48.7 ± 0.8 vs. 38.1 ± 0.8 kg; p < 0.05) than those fed H alone. Calves offered milk plus SR + H showed the highest growth rate and weaning weights (401 ± 13 g/day and 56.3 ± 1 kg, respectively). The lowest growth rate and weaning weights were observed in calves offered MR and H only (115 ± 13 g/day and 30.3 ± 1 kg, respectively). Calves offered the MR had higher number of scour days than those offered milk (13.5 vs. 3.3). The feeding of whole milk in combination with the starter ration and hay resulted in superior growth rates, higher weaning weights, and healthier calves than the other feeding regimens.     

High perennial ryegrass seeding rates reduce plant size and survival during the first year after sowing: does this have implications for pasture sward persistence?

Failure of perennial ryegrass swards to persist is a key issue on dairy farms in many areas of the world. This study describes an experiment conducted to test the hypothesis that high ryegrass seeding rates (>18 kg seed ha^?1) reduce plant size and physical survival during the first year after sowing, with negative implications for population persistence. Four cultivars representing four functional types of perennial ryegrass were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed ha^?1) with white clover in three dairying regions of New Zealand. Plant establishment rates, size and survival were measured for the first 13 months after sowing. Herbage accumulation, botanical composition and perennial ryegrass tiller density were also monitored. Increasing seeding rate reduced plant survival in the seven weeks after sowing, reflecting likely differences in germination and very early mortality of small seedlings. Thereafter, plant survival was relatively high and consistent across seeding rates at two sites but was consistently greater in the 6 kg ha^?1 treatment compared with the 24 and 30 kg ha^?1 treatments at one site. Higher seeding rates also increased ryegrass tiller density and the contribution of ryegrass towards total herbage biomass but reduced the contribution of white clover. Very few cultivar × seeding rate interactions were detected for any of the measured variables. Many of the seeding rate effects dissipated by the end of the first year after sowing, indicating that high seeding rates did not predispose swards to poor persistence in the longer term, irrespective of ryegrass functional type.     

Effect of parity number on the dry matter intake of dairy cows during the first week after calving

We investigated the effect of parity number on the dry matter intake (DMI) of cows during the first week after calving. Eighty‐three cows were evaluated from 14 days before to 7 days after calving. DMI and milk yield were measured for 7 days after calving, and the calving score was measured. Blood samples were collected throughout the experiment. The average DMI during the first week after calving was reduced in the first‐lactation heifers and high‐parity number cows. A quadratic relationship between the parity number and the DMI was observed. The first‐lactation heifers had lower prepartum serum total protein (TP) concentration and milk yield, higher prepartum serum nonesterified fatty acid (NEFA) concentration and calving score than the multiparous cows. The recovery rate of serum calcium (Ca) after calving was slow in the cows in the parity 6. The DMI was positively affected by the serum Ca concentration after calving, milk yield, and prepartum serum TP concentration and was negatively affected by the calving score and prepartum serum NEFA concentration. We conclude that the DMI immediately after calving tends to be lower in first‐lactation heifers and high‐parity number cows, but factors that reduce the DMI differ according to parity number.