Behaviour of twin- and triplet-born lambs and their dam 3 to 18 hours after birth is not a useful predictor of lamb survival to weaning.

OBJECTIVE: An experiment was designed to determine if behaviour traits expressed by twinand triplet-bearing lambs and their dams at 3 to 18 hours of age (after the immediate ewelamb bonding had occurred) were associated with lamb survival to weaning. METHODS: The behaviour of twin and triplet lambs and their dams was assessed in the paddock at 3 to 18 hours after birth. Observations were made of the number of high- and low-pitched bleats, time to stand, make contact with dam, suck from dam and follow dam were recorded for each lamb. The maternal behaviour score of each dam was assessed. A random sub-sample of lambs were assessed during a maternal-recognition test at 12 or 24 hours of age. Traits included time spent standing, sitting, walking, time taken to reach the ewes and time spent with the ewes as well as the number of high- and low-pitched bleats emitted by the lamb. RESULTS: In the paddock, for each additional second required for twin-born lambs to follow their dam, lambs were 1.004 (95% confidence interval [CI] 1.000 to 1.008) times more likely to survive to weaning (p<0.05). The opposite relationship, however, was seen in triplet lambs. For each additional second required for triplet-born lambs to follow their dam, lambs were 0.996 (95% CI 0.993 to 0.999) times as likely to survive to weaning (p<0.05). During the maternal recognition test, twin-born lambs were 0.989 (95% CI 0.979 to 1.000) times as likely to survive to weaning for every additional second they took to reach the contact zone (p<0.05). Similarly, triplet-born lambs were 0.994 (95% CI 0.989 to 0.999) as likely to survive for every additional second they took to reach their dam (p<0.05). CONCLUSION: All ewe behaviours and the majority of lamb paddock and test behaviours were not associated with the survival of twin- or triplet-born lambs and, therefore, are of little use as indicators of lamb survival to weaning.

A comparison of liveweight gain of lambs weaned early onto a herb-clover mixed sward and weaned conventionally onto a ryegrass-clover pasture and herb-clover mixed sward.

OBJECTIVE: The aim of the present study was to identify the impact of early weaning of lambs at approximately seven weeks of age onto a herb-clover mix on the liveweight gain of lambs and their dams. METHODS: In 2015, twin-born lambs that weighed a minimum of 16 kg (n = 134) were randomly allocated to one of three treatments: i) Early-weaned (58 days after the midpoint of lambing) onto an unrestricted allowance (>1,200 kg dry matter/ha) of herb-clover mix (HerbEW); ii) Lambs+dams unweaned onto an unrestricted allowance of herb-clover mix until conventional weaning (95 days after the midpoint of lambing) (HerbCW); iii) Lambs+ dams unweaned onto an unrestricted allowance of grass-clover pasture until conventional weaning (GrassCW). In 2016, twin-born lambs that weighed a minimum of 16 kg (n = 170) were randomly allocated to one of four treatments: i), ii), iii) (similar to 2015) and iv) Lambs+ dams unweaned onto a restricted allowance (<1,200 kg dry matter/ha) of grass-clover pasture until conventional weaning (93 days after the midpoint of lambing) (Restricted-GrassCW). RESULTS: In 2015, liveweight gain from L58 to L95 of HerbCW and GrassCW lambs did not differ (p>0.05), but were greater than HerbEW lambs. In 2016, HerbCW lambs had greater (p<0.05) liveweight gains from L51 to L93 than GrassCW followed by HerbEW and Restricted-GrassCW lambs. In 2015, liveweight gain from L58 to L95 of HerbEW ewes were greater than both GrassCW and HerbCW ewes while in 2016, liveweight gain of from L51 to L93 GrassCW and HerbCW ewes did not differ (p>0.05) but were greater (p<0.05) than those of HerbEW and Restricted-GrassCW ewes. CONCLUSION: These results indicate that when grass-clover pasture supply can be maintained at unrestricted intake level, there may be no benefit of weaning lambs early. However, at restricted pasture conditions lambs can achieve greater liveweight gains when weaned early onto a herb-clover mix.

The potential interaction between ewe body condition score and nutrition during very late pregnancy and lactation on the performance of twin-bearing ewes and their lambs.

OBJECTIVE: The present study aimed to determine the impact of ewe body condition score (BCS) (over a range of 2.0 to 3.0) and nutritional treatments (consisting of differing herbage masses) during very late pregnancy and lactation and their potential interaction on the performance of twin-bearing ewes and their lambs to weaning. METHODS: On day 142 of pregnancy, twin-bearing ewes with a BCS of 2.0, 2.5, or 3.0 were allocated to a "Moderate' or 'Unrestricted' nutritional treatment until day 95 of lactation (weaning). The nutritional treatments aimed to achieve average herbage masses of 1,200 to 1,300 kg dry matter (DM)/ha (Moderate) and 1,500 to 1,800 kg DM/ha (Unrestricted). RESULTS: There were no three-way interactions between ewe BCS group, nutritional treatment and time for any ewe or lamb parameter. The nutritional treatments had no effect (p>0.05) on lamb birth or weaning weight. Lambs born to Moderate ewes had greater survival and total litter weight at weaning (p<0.05). Regardless of BCS group, Unrestricted treatment ewes had greater body condition and back-fat depth at weaning than Moderate treatment ewes (p<0.05). Ewes of BCS 2.0 group reared lighter lambs to weaning (p<0.05) and tended to have a lower total litter weight (p = 0.06) than BCS 3.0 group ewes. CONCLUSION: This study suggests farmers should aim to have all ewes with a BCS of 2.5 or 3 in late pregnancy for optimal lamb weaning performance. Furthermore, there is no benefit to lamb production of offering ewes pasture masses >1,200 kg DM/ha during very late pregnancy and lactation.

Association of polymorphisms in growth hormone and leptin candidate genes with live weight traits of Brahman cattle.

Polymorphisms in candidate genes can produce significant and favorable changes in the phenotype, and therefore are useful for the identification of the best combination of favorable variants for marker-assisted selection. In the present study, an assessment to evaluate the effect of 11 single nucleotide polymorphisms (SNPs) in candidate genes on live weight traits of registered Brahman cattle was performed. Data from purebred bulls were used in this assessment. The dataset included birth (BW), weaning (WW), and yearling (YW) weights. A panel of 11 SNP markers, selected by their formerly reported or apparent direct and indirect association with live weight traits, was included in an assessment previously confirming their minimum allele frequency (<0.05). Live weights were adjusted BW (aBW), WW (aWW), and YW (aYW) using a generalized linear model, which included the fixed effects of herd and season of birth and the random effect of the sire and year of birth. An SNP in a growth hormone gene (GH4.1) was significantly related to aWW (P = 0.035) with an estimate substitution effect of 3.97 kg (P = 0.0210). In addition, a leptin SNP (LEPg.978) was significantly associated with aYW (P = 0.003) with an estimate substitution effect of 9.57 kg (P = 0.0007). The results suggest that markers GH4.1 and LEPg.978 can be considered as candidate loci for assisted genetic improvement programs in Mexican Brahman cattle.

Genetic trends for live weight traits reflect breeding strategies in registered Charolais Farms in Mexico.

Genetic trends are commonly used to verify genetic improvement; however, there are few reports on beef cattle in Mexico. Data from 1998 to 2013 from four Charolais bull breeding farms were examined to verify the genetic responses to different breeding management and selection criteria. Analysis included the comparison of regression lines of breeding values for birth (BW), weaning (WW) and yearling weights (YW), and maternal weaning weight (MWW) on the year of birth of the animals. Results revealed differential genetic progress for BW and YW and indicated that the overall analysis may have diluted the perception of genetic progress from the farmer's point of view. The use of breeding values as a tool for selection is effective to achieve genetic progress, even in negatively correlated traits, such as birth weight and yearling weight.

Ad libitum Pasture Feeding in Late Pregnancy Does Not Improve the Performance of Twin-bearing Ewes and Their Lambs.

The present study evaluated the effect of controlled ryegrass-white clover herbage availability from day 128 until day 142 of pregnancy in comparison to unrestricted availability, on the performance of twin-bearing ewes of varying body condition score (BCS; 2.0, 2.5, or 3.0) and their lambs. It was hypothesised that under conditions of controlled herbage availability, the performance of lambs born to ewes with a greater BCS would be greater than those born to ewes with a lower BCS. During the period that the nutritional regimens were imposed, the pre- and post-grazing herbage masses of the Control regimen (1,070±69 and 801±30 kg dry matter [DM]/ha) were lower than the ad libitum regimen (1,784±69 and 1,333±33 kg DM/ha; p<0.05). The average herbage masses during lactation were 1,410±31 kg DM/ha. Nutritional regimen had no effect on ewe live weight, BCS and back fat depth or on lamb live weight, indices of colostrum uptake, maximal heat production, total litter weight weaned or survival to weaning (p>0.05). The difference in ewe BCSs and back fats observed among body condition groups was maintained throughout pregnancy (p<0.05). At weaning, ewes from the BCS2.0 group had lower BCS and live weight (2.4±0.2, 74.3±2.6 kg) than both the BCS2.5 (2.6±0.2, 78.6±2.4 kg) and BCS3.0 ewes (2.7±0.2, 79.0±2.6 kg; p<0.05), which did not differ (p>0.05). Ewe BCS group had no effect on lamb live weight at birth or weaning or on maximal heat production (p>0.05). Serum gamma glutamyl transferase concentrations of lambs born to BCS3.0 ewes were higher within 36 hours of birth than lambs born to BCS2.0 ewes and BCS2.5 ewes (51.8±1.9 vs 46.5±1.9 and 45.6±1.9 IU/mL, respectively [p<0.05]). There was, however, no effect of ewe body condition on lamb plasma glucose concentration (p>0.05). Lamb survival was the only lamb parameter that showed an interaction between ewe nutritional regimen and ewe BCS whereby survival of lambs born to BCS2.5 and BCS3.0 ewes differed but only within the Control nutritional regimen ewes (p<0.05). These results indicate farmers can provide twin-bearing ewes with pre- and post-grazing ryegrass-white clover herbage covers of approximately 1,100 and 800 kg DM/ha in late pregnancy, provided that herbage covers are 1400 in lactation, without affecting lamb performance to weaning. The present results also indicate that under these grazing conditions, there is little difference in ewe performance within the BCS range of 2.0 to 3.0 and therefore they do not need to be managed separately.

The effect of heparinized catheter lock solutions on systemic anticoagulation in hemodialysis patients.

BACKGROUND: Hemodialysis catheter thrombosis is associated with loss of catheter patency, catheter-related bacteremia and sepsis. To limit these risks, many renal units use heparin as a catheter-locking solution. In this study we investigate the effect of different concentrations of heparin catheter lock solution on systemic anticoagulation in an investigator-blinded randomized study of patients with non-tunneled (temporary) central venous catheters. METHODS: 28 consecutive patients requiring insertion of a temporary non-tunneled dual lumen central venous hemodialysis catheter were randomly allocated to receive either heparin 5,000 IU/ml or heparin 1,000 IU/ml as catheter lock solutions. The primary outcome measure was the difference in activated partial thromboplastin time (APTT) at 10 minutes following catheter locking with heparin 5,000 IU/ml and heparin 1,000 IU/ml. Secondary outcomes included intradialytic blood flow rates, catheter removal due to insufficient hemodialysis blood flow to maintain hemodialysis and catheter-related bacteremia. RESULTS: 13 patients were randomized to the heparin 1,000 IU/ml group with 15 patients randomized to the heparin 5,000 IU/ml group. There was a statistically significant increase in APTT at 10 minutes between groups with median +22.2% (range 0 - 210) rise in APTT in the heparin 1,000 IU/ml group compared with +373.7% (range 133 - 800) in the heparin 5,000 IU/ml group (p < 0.001). There was no statistically significant difference between groups with the secondary outcomes of intradialytic blood flow, catheter failure rates and catheter-related bacteremia rates. CONCLUSIONS: Heparin 1,000 IU/ml catheter lock solution confers a significantly lower risk of systemic heparinization than heparin 5,000 IU/ml without any overtly detrimental effect on intradialytic blood flow, catheter failure rates and catheter-related bacteremia rates.

An overview on production, consumer perspectives and quality assurance schemes of beef in Mexico.

Mexico has a large beef production industry that has grown significantly in the last decade. The export market has increased, however, domestic beef consumption has declined. A knowledge of the factors affecting consumer perceptions and acceptance of beef might highlight critical points that could improve the whole industry, and lead to an increase of export and domestic consumption. The present paper is aimed to provide an overview on the dynamics of Mexican beef production systems, the current perceptions of the Mexican consumer for beef, and the current available beef quality assurance schemes, based on published and official information.

The effects of birth rank (single or twin) and dam age on the lifetime productive performance of female dual purpose sheep (Ovis aries) offspring in New Zealand.

Greater rates of genetic gain can be achieved by selecting animals born to younger parents. However, little is known about the lifetime performance of dual purpose ewes (Ovis aries) that are born to primiparous ewe lambs (8 to 9 months old at breeding). This experiment investigated the effect of being born from either a ewe lamb or mixed age dam as either a single or twin on the lifetime performance of ewe progeny. Lifetime performance was measured in terms of the life time live weights of the ewes, the weight and number of lambs born and weaned, the efficiency of production (kilograms of lamb weaned / predicted pasture intake (kgDM) of the ewes), and ewe survival. The study followed the lifetime production of 17 single and 41 twin female lambs born to mature ewes (M1 and M2, respectively), and 28 single and 29 twin lambs born to ewe lambs (L1 and L2, respectively). Over their lifetime L2 ewes were lighter (P<0.05) but had similar body condition scores to the other three ewe groups. There was no difference in average progeny weaning weight or total progeny litter weaning weights between groups. The M1 ewes had the greatest longevity (P<0.05) of the four groups. Even though L2 ewes were lighter than the other three groups, this was insufficient to increase their lifetime efficiency of production (kg lamb weaned/predicted pasture consumption), relative to the other groups. These results suggest farmers could select replacements born to ewe lambs without sacrificing animal production.

Genetic variances and covariances of live weight traits in Charolais cattle by multi-trait analysis.

Live weight traits are economically important for beef cattle production systems. Genetic analysis of live weight traits frequently presents a problem due to animal records, in that matter, not all the animals have complete records as many young animals leave the herd because of sale, transfer to another herd, or culling reasons. Therefore, the use of multi-trait genetic analysis might be of assistance to help overcome any possible loss of information for those animals with incomplete records. In this study, genetic variances and covariances were obtained to estimate genetic parameters for birth (BW), weaning (WW), and yearling (YW) live weights in a registered Charolais beef cattle population using a multivariate model, where a considerable reduction of data from birth weight to year weight was observed. Direct and maternal heritabilities for BW, WW, and YW were 0.50, 0.30, and 0.28, and 0.31, 0.25, and 0.14, respectively. Direct and maternal genetic correlations were negative in all live weight traits. Genetic correlations among direct BW with direct WW and YW were low, while genetic correlations among maternal traits were medium or high (r>0.39). Comparison between univariate and multi-trait models with substantial reduction of information revealed important differences, implying that multi-trait analysis is better for the structure of data allowing a better fitting of genetic effects by covariance among evaluated traits. Results support multi-trait analysis implementation for genetic evaluations for live weight traits of Charolais cattle.

Induced seasonal reproductive performance in two breeds of sheep.

The objective of the present experiment was to determine whether failure to become pregnant through out-of-season reproductive management regimes is attributable to a failure to stimulate normal corpora lutea (CL) production. Romney ewes and East Friesian Composite (EF) ewes were mated in summer, autumn, winter, and early and late spring after administration of intravaginal progesterone inserts (plus eCG in spring and summer) in a factorial (two breedsxfive mating periods) experimental design. Oestrus rate was determined from mating data, and the numbers of CL were determined by laparoscopy 9 days after ram introduction. Conception rate, pregnancy rate and litter size were determined by transabdominal ultrasonography 62 days after ram introduction. Proportions of ewes displaying oestrus did not differ significantly (75-100%) between seasons or breeds, except for the Romney ewes in summer (67%; P<0.05). Numbers of CL on Day 9 for EF ewes was lowest in autumn (1.5) and winter (1.5), and highest in late spring (2.1; P<0.05). In contrast, Romney ewes had the lowest CL count in summer (1.3), and the highest in autumn (1.8) and winter (1.6; P<0.05). Only in summer was there a difference between breeds (EF 1.8; Romney 1.3; P<0.01). The proportion of ewes that failed to conceive despite having one or more CL present was highest in late spring (EF 41%, Romney 43%), and lowest in autumn (EF 9%, Romney 4%) and winter (EF 14%, Romney 4%; P<0.05). Conception and pregnancy rates followed similar patterns with values for autumn (EF 91%, 91%; Romney 96%, 96%) and June (EF 86%, 82%; Romney 91%, 83%) being significantly (P<0.05) higher than in early (EF 50%, 40%; Romney 54%, 50%) and late spring (EF 44%, 36%; Romney 42%, 36%). Pregnancy rate in summer was higher for EF ewes (60%) than for Romney ewes (39%) but conception rates were not statistically different (EF 68%; Romney 60%). Numbers of foetuses identified at scanning was highest in autumn (1.5) and lowest in late spring (0.5 P<0.001): Litter size in pregnant EF ewes was highest in early spring and lowest in winter (1.8 versus 1.2; P<0.01), but for pregnant Romney ewes was highest in winter and lowest in early spring (1.9 versus 1.3; P<0.001). It was concluded that seasonal differences in the ability of ewes to conceive are not the consequence of failure to display oestrus or to ovulate, but probably are a result of failure of fertilisation or the establishment of pregnancy.

Changes in metabolite, energy metabolism related enzyme activities and peripheral blood mononuclear cell (PBMC) populations in beef heifers with two differing liveweight change profiles in New Zealand.

Metabolite and immunoreactive insulin (IRI) concentrations, energy metabolism related enzymes activities and peripheral blood mononuclear cell (PBMC) populations were measured in blood of pregnant Angus heifers with differing liveweight change profiles (gaining or losing), in New Zealand to investigate the meanings of those parameters in the restricted feeding beef heifers. Beef heifers losing liveweight (-412 g/day) showed significantly lower concentrations of plasma IRI, and higher concentrations of plasma free fatty acid (FFA) than heifers gaining liveweight (483 g/day). The cytosolic and mitochondrial malate dehydrogenase (MDH) activities and MDH/lactate dehydrogenase (M/L) ratio in leukocytes of the liveweight losing heifers were significantly higher than those the liveweight gaining heifers. Percentages of cluster of differentiation (CD) 3 positive cells and natural killer (NK) cells in PBMC decreased significantly in the liveweight losing heifers compared to those in the liveweight gaining heifers. Plasma IRI and FFA concentrations, leukocyte cytosolic and mitochondrial MDH activities and CD3 positive and NK cell populations may be useful markers to evaluate metabolic conditions and immunity in the restricted feeding beef heifers.

Vascular access in haemodialysis patients: a modifiable risk factor for bacteraemia and death.

BACKGROUND: Bacteraemia and the development of sepsis syndrome is second only to cardiovascular disease as the leading cause of death in patients on renal replacement therapy. AIM: To determine the contributions of laboratory and clinical variables to the risk of bacteraemia and death in haemodialysis patients. DESIGN: Retrospective analysis. METHODS: We analysed all patients receiving haemodialysis in our renal unit at the beginning of January 2004 (n=263), recording clinical and laboratory variables for each patient at study entry. Bacteraemia and mortality were recorded for the subsequent 18-month period. Multivariate analysis using a Cox proportional hazards model was used to test for independent associations between variables and outcomes. RESULTS: During the study period, 45 patients (17.1%) developed bacteraemia and 65 (24.7%) died. Under multivariate analysis, use of dialysis catheters at study entry was a major factor in the development of bacteraemia and death with hazard ratios (HR) of 5.4 (p<0.001) and 2.8 (p=0.012), respectively, for tunnelled central venous catheters vs. arteriovenous fistulas (AVFs) and 3.1 (p=0.01) and 3.4 (p=0.001), respectively, for non-tunnelled central venous catheters vs. AVFs. Elevated CRP at study entry was independently associated with bacteraemia (HR 1.5 per unit log-CRP, p=0.006). Low serum albumin (HR 0.92, p=0.005) was independently associated with death. DISCUSSION: Use of synthetic vascular access catheters and heightened inflammatory state both have strong independent associations with subsequent bacteraemia and death. Bacteraemia surveillance strategies should be developed, with consideration of vascular access type and baseline inflammatory state as key components.

Endothelial dysfunction in renal transplant recipients.

Endothelial dysfunction and damage are systemic processes that are recognised to play a central role in the pathogenesis of hypertension and atherosclerotic cardiovascular disease. Renal failure is associated with impaired endothelium dependent vasodilatation that is partly a consequence of increased circulating levels of asymmetric dimethyl arginine. Endothelial dysfunction persists, although it is improved, after renal transplantation. Statins appear to improve endothelial dysfunction, as does withdrawal of calcineurin inhibitors, although there is no evidence that these strategies improve patient or graft survival. The situation in transplant recipients is complicated by the fact that endothelial dysfunction (within the graft vasculature) may be a separate process contributing to chronic allograft nephropathy and to circulating levels of endothelial cells and their components, thus limiting the utility of circulating markers of endothelial damage in this population.

Moxonidine: a review.

Moxonidine is an imidazoline compound which acts on I1 imidazoline 'receptors' in the central nervous system to reduce blood pressure. This novel mechanism of action is claimed to lead to fewer adverse effects than the older centrally-acting agents such as clonidine. In this review we examine the drug's pharmacology, clinical pharmacokinetics, efficacy as an antihypertensive agent including comparative studies with pre-existing drugs, and adverse effect profile. With a growing number of effective antihypertensive agents already available to the clinician, it is not yet clear whether moxonidine represents a significant advance in hypertension management.

The vascular endothelium in chronic renal failure.

Chronic renal failure (CRF) is associated with a 20-fold increased risk of cardiovascular death, two principal mechanisms being: sudden, arrhythmic death associated with left ventricular hypertrophy, and ischaemic heart disease, associated with accelerated atherosclerosis. In recent years, the vascular endothelium has been recognised as a large and complex endocrine organ, with many important physiological functions including the control of vascular tone. Endothelial dysfunction, commonly characterised by reduced production of the vasodilator nitric oxide (NO), is thought to be a key initial event in the development of atherosclerosis and is present in patients with hypertension and hyperlipidaemia. While these cardiovascular risk factors are also prevalent in CRF, other factors more specific to uraemia such as accumulation of homocysteine and asymmetric dimethylarginine (endogenous inhibitor of NO synthase) may impair endothelial function. Modulation of endothelial function in CRF may offer a novel strategy to reduce cardiovascular disease.

Cardiac and vascular abnormalities in renal transplant patients: differential effects of cyclosporin and azathioprine.

Renal transplant patients die prematurely of cardiovascular disease and LV hypertrophy is now recognised as an important adverse prognostic indicator. This study investigated the factors implicated in the development of echocardiographic abnormalities (including LV hypertrophy) and the possible differential effects of treatment with cyclosporin and azathioprine. A cross-sectional study was undertaken in 46 patients randomly assigned to immunosuppressant treatment with either cyclosporin or azathioprine at 1 year post-transplantation: patients were studied not less than 5 years after assignment to cyclosporin (CyA) - or azathioprine (Aza)-based treatment regimens. Although clinic blood pressure control was not different in the two treatment groups, 24 hour ambulatory BP (ABP), particularly night-time BP, was significantly higher in the CyA group. There was a trend for both left ventricular hypertrophy (61 vs. 43%) and carotid wall thickening (43 vs. 26%) to be more common in the CyA group though this failed to achieve statistical significance. Left ventricular mass was determined by ABP, rather than clinic BP, and was also associated with increased QT dispersion. Multivariate analysis identified that 24 hour ambulatory systolic blood pressure (ASBP) and time on renal replacement therapy (RRT) were the major determinants of LV mass. Thus, despite the absence of differences in clinic BP measurements, CyA treatment was associated with higher rates of cardiovascular functional and structural abnormalities. This small scale study has identified cardiovascular functional and structural abnormalities in renal transplant patients, particularly in those receiving CyA-based immunosuppressive therapy. However, rather than reflecting a direct effect of CyA they are related to increased 24 ABP (but not clinic BP). These data suggest that ABP should be used to monitor and target antihypertensive therapy in this high risk patient group. Moreover, the future use of non-calcineurin inhibitor immunosuppressant therapy may have benefits on blood pressure control and LV mass.

Variation of transducer frequency output and receiver band-pass characteristics for improved detection and image characterization of solid breast masses.

A new approach has been used for ultrasound detection of small benign and malignant breast masses, namely, control of scattering in such a manner that a small mass can be easily recognized because of the effect of the scattering on the contrast between the mass and the surrounding normal tissue. Maintenance of good resolution as scattering is varied is an essential aspect of this approach. Image contrast is dependent on a number of instrumentation parameters but, in a fundamental sense, it is related to differences in the amount of scattering between a solid breast mass and the surrounding normal tissue. In the subject studies, modification of image contrast is accomplished by varying either the center frequency output of the transducer or the band-pass of the receiver. These approaches take advantage of differences in the frequency dependence of scattering coefficients of solid breast masses and normal tissue. A unique technique for varying center frequency without switching transducers was developed, namely, use of a wide bandwidth, co-polymer PVDF transducer, in combination with certain instrumentation conditions which allow the center frequency output of a single ultrasound transducer to vary over a relatively wide frequency range. Using this technique, an automatic B-mode ultrasound imaging breast instrument which allows emission of 3.5, 4.5, 6.5 and 11 MHz ultrasound frequencies from the same co-polymer transducer was used to examine patients with solid breast masses. Both a wide band-pass receiver, similar to that commonly used in clinical ultrasound systems and a tunable receiver (which allows variation of the band-pass from wide to narrow) was used with this automated system. Using the standard receiver system, it was found that there are advantages to having a range of transducer frequencies immediately available for breast examination. These include: (1) improved detection of masses located in highly attenuating regions of breast (by decreasing frequency); (2) availability of diagnostically relevant information at some one frequency which may not be apparent at other frequencies. Using the multiple frequency system and the standard receiver, it was found that the most appropriate examination frequencies for detection and diagnosis of fibroadenomas are higher frequencies (8 to 11 MHz). This is particularly true in the case of fibroadenomas in fatty breasts.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of growth potential and growth path on tenderness of beef longissimus muscle from bulls and steers.

The influence of growth potential or growth path on the tenderness of the longissimus muscle was investigated using 117 Angus and Angus-cross bulls and steers raised on pasture over two successive years. Growth rate for a period of 100 d from a weight of about 200 kg was used to identify the faster-growing two-thirds of cattle within the gender groups, half of which were grown fast to a slaughter weight of 530 kg at 16 to 18 mo of age (the Fast group), whereas the other half were restricted in growth (the Restricted group) so they attained a similar final weight as the slower-growing third (the Slow group) at about 26 mo of age. The Restricted group was included to determine whether the tougher meat expected from the Slow group relative to the Fast group (based on previous results) was due to the greater age of the Slow group or to their slower early growth rate. Beef from the Fast group was tenderer than that from both the Slow and Restricted groups based on sensory panels (P < 0.05) and objective measures (P < 0.05), indicating that the early growth-rate potential was less important than the differences in age or the patterns of growth for the Slow and Restricted groups. Improved tenderness for the Fast group was associated with more intramuscular fat (P < 0.05) and higher myofibrillar fragmentation indexes (P < 0.05). Patterns of tenderness differences between treatment groups were similar for bulls and steers, but beef from bulls was tougher (P < 0.001) than that from steers. The more tender beef from steers was associated with a slightly lower ultimate pH (P < 0.001), higher myofibrillar fragmentation indexes (P < 0.001), and more intramuscular fat (P < 0.001). Ultimate pH affected beef tenderness (P < 0.01), but adjustments to a constant pH did not decrease differences between treatment and gender groups. The higher growth rates (P < 0.01) and leaner carcasses (P < 0.01) of bulls compared with steers were consistent with other studies. Increases in age of 8 to 10 mo may be associated with less tender beef for cattle finished on pasture, and beef from bulls is likely to be less tender than that from steers.

Intensive sheep and beef production from pasture--a New Zealand perspective of concerns, opportunities and challenges.

This paper details current production trends for sheep and beef cattle production in New Zealand and gives some insight into the opportunities for improvement based on New Zealand research at Massey University. Further it outlines some of the challenges the industries face in the near future. The New Zealand climate favours pasture growth and this is the key to sheep and beef cattle production with over 95% of the diet being grazed pasture or crop. Exports are the focus of the industry with 95% of sheep meat and wool, and 80% of beef exported. There have been considerable gains in production over the last 20 years but there still remains a huge opportunity for further intensification through breeding sheep at an earlier age, increasing the weight of lambs weaned per ewe per year and improving beef production systems. These improvements need to occur within a framework of minimal environmental footprint and produce products that are in demand in the high end international markets.