Effect of conception date and hind nutrition on fetal growth trajectory and gestation length of red deer (Cervus elaphus)

This study tested the hypothesis that the negative association between gestation length and conception date in red deer is mediated by nutrition. Twenty-eight pregnant red deer were randomly allocated to four groups according to a 2 × 2 factorial design, with the factors conception date (14 March, E; 28 April, L) and level of nutrition (ad libitum, H; restricted, R). Animals were housed indoors in individual pens from early winter until calving and offered daily an ad libitum pelleted ration. The daily ration was then restricted from late winter in ER (134 days post-conception) and LR (89 days post-conception) groups, so that these hinds did not experience a seasonal increase in food intake. X-Ray computed tomography scans were taken at Days 120, 150, 180 and 210 of gestation (mid–late gestation) to estimate weight of various conceptus components. Growth rate of the total fetus was significantly higher in LH than in other treatments (P < 0.01) between Days 180 and 210 of gestation. Birthweight was not significantly different (P > 0.05) between treatments or calf sex. Birthweight was associated directly with change in hind liveweight (P = 0.03) and body condition score during the third trimester of pregnancy (P = 0.01), but was not significantly associated with gestation length (P = 0.34). Gestation length was 4.4 days longer in LR than LH hinds (P = 0.03) and was negatively associated with both food intake (P = 0.03) and LW gain (P = 0.02) during the final trimester of gestation. Feeding late-conceiving hinds an ad libitum diet of high-quality food during the third trimester of gestation maximises fetal growth and shortens gestation length.

Genetics of early conception and its relationship to growth traits in red deer (Cervus elaphus)

The genetics of early conception success and live-animal growth were studied in five herds of red deer in New Zealand. Conception date (CD) was used as the criterion of success in seasonally mated hinds, with 2493 mating records available. Liveweights analysed were weaning weight, yearling weight, 15-month weight and mature weight (hinds only). CD and liveweights were analysed using restricted maximum likelihood procedures with an animal model, including all available pedigree records. Under the management conditions applied, CD had a phenotypic standard deviation of 7.9 days, a repeatability across years of 0.29 ± 0.03 and a direct (univariate) heritability of 0.20 ± 0.06. Regression procedures using DNA markers to adjust the data for genetic differences resulting from an animal’s ancestral region of origin (mainly western vs eastern European) had little effect on the parameter estimates above. Direct heritability estimates for the four weight traits were 0.38 ± 0.03, 0.49 ± 0.02, 0.48 ± 0.04 and 0.46 ± 0.04, respectively, while the genetic correlations between CD and these traits (e.g. using 1763 paired records of CD with yearling weight) were –0.24 ± 0.11, –0.24 ± 0.09, –0.16 ± 0.10 and –0.04 ± 0.09, respectively. Selection for earlier CD would be successful and compatible with selection for higher juvenile weights.

Pre-weaning growth of red deer calves is not determined by ability of hinds to produce milk

Three experiments were carried out to determine whether growth of suckling red deer calves is determined by the potential of their mothers to produce milk. In the first experiment red deer hinds (n = 10, calves 6 weeks old) were treated either with bovine somatotrophin (bST, 54 mg s.c. injected every 2 weeks for 8 weeks then 108 mg every 2 weeks for a further 8 weeks) or saline. There was no effect of bST treatment on calf or hind liveweight, calf liveweight gain or body condition score of hinds. The second experiment used red and red-wapiti crossbred deer calves (n = 8–11) suckled by red deer dams that had been treated with bST or had received excipient only for 12 weeks from when the calves were 5 weeks old. Calf liveweight was affected by genotype (wapiti-red crossbreds were heavier than their red counterparts) but there was no effect of bST treatment of the hinds on calf growth in either of the genotypes. Although bST treatment of the suckled hinds elevated their plasma insulin-like growth factor-1 concentration it had no effect on milk yield. A third experiment ruled out the possibility that bST ingested by calves in milk from treated hinds would have had any influence on growth of calves in the other experiments. From these results it is concluded that the inherent demand from suckling calves, rather than the ability of adequately nourished hinds to produce milk, determines growth rate of red deer calves from birth to weaning.

Seasonal luteal cyclicity of pubertal and adult red deer (Cervus elaphus)

Reproductive failure of rising-two-year-old (R(2)) hinds and seasonal misalignment between calving and pastoral feed production are two factors limiting reproductive productivity of farmed red deer hinds in New Zealand. This study aimed to better understand processes around female puberty and breeding seasonality by describing the potential breeding season (i.e., oestrous cyclicity) of three red deer genotypes. A total of 27 hinds born in December 2005, representing Eastern European (Cervus elaphus hippelaphus), Western European (C.e. scoticus) and F1 crossbred (C.e. hippelaphus×scoticus) red deer, were blood sampled thrice-weekly for 7-8 months (February-September/October) across two years spanning the potential breeding seasons as R(2)'s in 2007 (i.e., puberty) and as adults in 2008. Plasma progesterone profiles were used to construct breeding cycle histories for each hind. Four R(2) hinds failed to initiate oestrous cycles (i.e., puberty failure). The remaining R(2) hinds, including all F1 hinds, exhibited between two and seven oestrous cycles. F1 hinds were significantly earlier to initiate, and later to terminate, cyclic activity, resulting in a longer mean pubertal breeding season (139 days) than for Eastern (86 days) and Western hinds (86 days). However, the data for R(2) hinds are confounded by live-weight, with the F1 hinds being significantly heavier than other genotypes. There were significant correlations between live-weight and seasonality parameters in 2007. All hinds were cyclic as adults in 2008, exhibiting between four and nine oestrous cycles, and a mean breeding season duration of between 132 (Western) and 137 (F1) days. For adult hinds there were no significant genotype differences in cyclic onset and cessation timing, and no observable relationships between live-weight and any reproductive parameter. However, the mean dates for the onset of the breeding season for all genotypes in 2008 were 2-3 weeks later than normally expected for adult hinds in New Zealand. The reasons for this are unclear but may relate to chronic stress of frequent animal handling. The study has demonstrated that puberty in red deer hinds is associated with a shorter potential breeding season than for adult hinds, and that perturbation of breeding activity appears to be quite common, leading to incidences of puberty failure and possibly other aberrant cyclic events. Live-weight×genotype interactions may influence puberty but do not appear to be strongly expressed in adults. However, the relatively late onset of oestrous cyclicity in the adult hinds may be an artefact of the study that has masked genetic influences on seasonal breeding patterns.

Effect of melatonin implants on the incidence and timing of puberty in female red deer (Cervus elaphus)

A study was conducted to test the hypotheses that exogenous melatonin treatment of 11-13 month-old red deer hinds: (1) advances the timing of first ovulation, (2) increases the proportion of individuals attaining puberty at ∼16 months of age, and (3) reduces the live-weight threshold for attainment of first pregnancy. A total of 3901 rising-2-year-old (R₂) hinds within two herds (A and B) across two years either received single melatonin implants on two occasions in summer (n=1399) or were untreated controls (n=2502). Hinds were joined with stags from mid January to mid May, and were subjected to real-time rectal ultrasonography in early June to assess pregnancy status (proxy for puberty attainment) and foetal age for conception date assignment. Live-weights were recorded for each hind in January (12 months of age) as a proxy for weight at puberty. Melatonin treatment of hinds was associated with a significant advancement in mean conception dates in both herds in both years (P<0.05), with a cohort difference in mean dates between treated and control hinds ranging from 9 to 17 days. Analysis of the temporal distribution of conception dates for each cohort revealed bi-modal or tri-modal patterns of conception indicative of conceptions to first or subsequent ovulations (oestrous cycles). Across all cohorts, melatonin treatment was associated with higher conception rates to first ovulation (P<0.05) resulting in greater overall synchrony of conceptions. Regression analysis demonstrated a significant negative slope for conception date against live-weight (P<0.001), but there was no evidence that this slope varied with treatment, herd or year (P>0.05); for every 10kg increase in live-weight conception date was advanced by an average of 1.3 days. In Herd A, melatonin treatment was associated with significantly higher pregnancy rates in both years (90.3% vs. 78.0% in Year 1 and 84.4% vs. 57.1% in Year 2; P<0.05). The principle effect of melatonin treatment was to increase the pregnancy rate of hinds of low body-mass. In Year 1, at 60kg live-weight a logit regression model indicated a pregnancy rate of 52% for untreated hinds and 83% for treated hinds. At 105kg the rate for both cohorts was 90%. In Herd B, melatonin treatment was associated with higher conception rates in both years but these differences were not significant following correction for slight differences in mean live-weight (P>0.05). The study has demonstrated that factors influencing puberty attainment in R₂ red deer hinds can vary between populations. In Herd A, in which body mass of hinds immediately prior to their first potential breeding season may have been the principle limiting factor, melatonin treatment appears to have instigated the pubertal process in hinds that would otherwise be of insufficient body mass.

Evaluation of management variables to advance conception and calving date of red deer (Cervus elaphus) in New Zealand venison production systems

The ability to shift the supply of New Zealand chilled venison from farmed yearling red deer stags to obtain premium prices in seasonal European markets necessitates early calving of hinds combined with high growth rates of their calves. Two studies over a three-year period evaluated three management variables that offer potential to advance calving date. Under the conditions of the studies there was no consistent evidence that the management practices of early stag introduction, early weaning and enhanced hind nutrition prior to conception (lactation) and pre-calving (third trimester of pregnancy) advanced conception date and calving date in red deer hinds. However, the nutrition effect was diminished by the difficultly in achieving the dietary contrast necessary for the targeted 5kg differentiation in hind live weight at strategic times of the year. Across all hinds there was a significant pre-mating (mid-March) live weight effect on conception day in the one year in which a 5kg difference between nutritional regimens was achieved, but the driver was live weight and not nutrition. There were significant effects of nutrition on calf growth, with the growth rates of calves weaned in mid-March significantly higher when their dams grazed a high plane of nutrition pre-conception. There were significant and consistent inverse relationships between conception day and calving date that implied variation around gestation length, with early- and late-conceiving hinds exhibiting longer and shorter gestation lengths, respectively. Across all treatments, calving date was predicted to advance by approximately 5 days for every 10-day advance in conception date. However, there was a significant carry-over effect of nutrition pre-conception on calving date, with hinds on a high plane of nutrition pre-conception exhibiting shorter (2-4 days) gestation lengths. There were also indications that hinds may manipulate gestation length in response to live weight gain pre-calving. These findings suggest that fetal growth trajectory may be the principle driver of gestation length and calving date. Although there were no direct effects of hind nutrition pre-mating on conception dates, nutrition remains an important component of the management of hinds and their calves in venison production systems. The outcomes of the 3-year program suggest that there are limited opportunities to manipulate calving date through manipulation of management variables.

Bovine somatotrophin stimulates milk production in red deer hinds

To determine its potential as a tool for studies of growth in suckling red deer calves, bovine somatotrophin (bST) was administered to lactating red deer hinds. The present study used twice-daily machine milking of bST-treated hinds (n = 10, 54 mg bST for 2 weeks then 108 mg for 1 week) and compared the milk yield with that of saline-treated controls (n = 9). Treatment with 54 mg bST tended to increase milk yield by ~16% and the 108-mg dose increased (P = 0.013) milk yield by ~32%. Both doses of bST increased (P < 0.05 and P < 0.001, respectively) plasma insulin-like growth factor-1 concentration but did not affect total solids or fat content of the milk, nor was there any effect on body condition score or liveweight of the hinds. This shows that milk production in red deer hinds is increased by administration of bST, which makes it a suitable experimental technique for investigating the lactational biology of red deer.

Reproductive performance of pubertal red deer (Cervus elaphus) hinds: effects of genetic introgression of wapiti subspecies on pregnancy rates at 18 months of age

Low reproductive productivity of young red deer (Cervus elaphus) hinds on New Zealand deer farms appears to reflect high incidences of puberty failure at 16 months of age. This is despite the general attainment of average liveweights 15-25 kg in excess of the accepted minimum threshold for puberty in subspecies of western European origin (scoticus, elaphus and hippelaphus) that form the basis of the national herd. The present study tests the hypotheses that introgression of the larger North American wapiti subspecies (nelsoni, manitobensis and roosevelti) into breeding herds (1) can be assessed from morphological features of individuals, (2) that there is a relationship between the level of wapiti parentage and non-pregnancy rate at 18 months of age (a proxy for puberty failure) and (3) that minimum liveweight thresholds for puberty increase with increasing levels of wapiti parentage. A total of 4329 18-month-old hinds across four "red" deer farms in southern New Zealand were scanned for pregnancy status. Each hind was assigned a wapiti score (WS) as a subjective assessment of the obviousness of wapiti features. Various body measurements were additionally recorded for each hind. A hair sample was collected for DNA analysis (14 markers) to objectively assign subspecies pedigree (i.e. "Elkmeter") on a subset of 1258 individuals. A total of 506 (11.7%) hinds were not pregnant at 18 months of age with rates varying between 4.1 and 37.3% between farms and years. Mean WS differed significantly between farms and reflected the genetic management policy of each farm. WS was positively correlated to Elkmeter for each farm/year (<0.05) although regression slopes varied significantly. WS was able to be adjusted for these differences to assign a corrected WS (CWS) for all 4329 individuals that estimated the proportion wapiti parentage. Discriminant analysis of morphological variables relative to Elkmeter supported the first hypothesis and showed that shoulder height and body length were good indicators of the degree of wapiti parentage within individuals. This enabled the development of an objective estimate of wapiti parentage (EWP). The actual level of such parentage within herds ranged from <5 to >55%. There was a significant negative association between wapiti parentage and pregnancy, which was strongly influenced by liveweight, supporting the second and third hypotheses. This was manifest as marked displacement of pregnancy probability curves in relation to liveweight between genotype groups, particularly for those groups with >20% wapiti parentage. For example, predicted threshold liveweights required to achieve a 90% pregnancy rate for EWP values that represent 0, 10, 20, 30, 40 and 50% wapiti parentage were 81, 81, 85, 106, 127 and approximately 137 kg, respectively. Within the study herds, the majority of hinds of 0-20% wapiti parentage exceeded the predicted 90% threshold liveweights for their genotype cohort. However, hinds with higher levels of wapiti parentage generally fell below the predicted threshold for their genotype group. The data strongly suggest that under liveweight performance levels measured for red deer, hinds with >20% wapiti parentage are at high risk of puberty failure.

Maternal productivity of Angus cows divergently selected for post-weaning residual feed intake

Data on 185 Angus cows were used to study the effect of divergent selection for residual feed intake on maternal productivity across 3 mating seasons, starting from 2000. The cows were the result of 1 to 2.5 generations of selection (mean of 1.5), and differed in estimated breeding value for residual feed intake by 0.8 kg/day. In general, cows lost subcutaneous fat (measured 2 times a year) during the period when they were nursing calves, and gained fat thereafter. No significant selection line differences in fatness were observed except for those measured at the start of the 2000 (10.8 ± 0.4 v. 9.3 ± 0.4 mm), 2001 (11.3 ± 0.4 v. 9.8 ± 0.4 mm) and 2002 (7.0 ± 0.5 v. 5.7 ± 0.5 mm) mating seasons, where high residual feed intake cows had significantly (P<0.05) higher rib fat depths. No significant selection line differences in weight (measured 4 times a year) were observed. However, the cows either maintained or lost weight during the calf nursing period, and gained weight thereafter, with mean weights ranging from 450 to 658 kg. There were no significant selection line differences in pregnancy (mean 90.4%), calving (mean 88.7%) and weaning (mean of 80.8%) rates, milk yield (mean 7.7 kg/day) and weight of calf weaned per cow exposed to bull (mean 195 kg). The study indicates that after 1.5 generations of divergent selection for residual feed intake there are no significant selection line differences for maternal productivity traits.

Effect of missing data on the estimate of average daily feed intake in beef cattle

The effect of missing feed intake records on the estimate of feed intake in cattle over a 70-day test period was studied. Two datasets, containing several cattle breeds at different ages, were analysed. The first dataset comprised 300-day-old Angus cattle, while the second dataset consisted of 900-day-old Limousin and Jersey crossbred cattle. A first-, second- and third-order polynomial and a non-linear function were fitted to the intake data. The 3 polynomial functions showed minimal differences in their goodness of fit to the data, with the non-linear function explaining the least variation in intake. Both datasets were analysed over a 70-day test period and shortened tests were compared to the full 70-day test. Tests were shortened by randomly deleting intake records or periodically deleting data on a daily or weekly basis. The effect of missing data on feed intake estimates was evaluated using Pearsons correlation and t-tests. The results suggest that a greater proportion of data can be removed randomly and daily, compared with missing data in weekly blocks. However, when data are removed in weekly blocks, removal in the middle of the test period gives a more accurate estimate of feed intake. It appears that in young growing animals, estimation of daily feed intake is more sensitive to missing feed intake records than for older cattle.

Metabolic differences in Angus steers divergently selected for residual feed intake

Residual feed intake measures variation in feed intake independent of liveweight and liveweight gain. First generation steer progeny (n = 33) of parents previously selected for low or high post-weaning residual feed intake were examined to determine metabolic processes contributing to variation in residual feed intake. Blood samples were taken from the steers from weaning through to slaughter. These samples were analysed for key metabolites and hormones. Total urine and total faecal collections were taken from the steers in an animal-house experiment to estimate dry matter digestibility, microbial protein production and protein turnover. At weaning, there were phenotypic correlations between concentrations in plasma of β-hydroxy butyrate (r = 0.55, P<0.001), aspartate aminotransferase (r = 0.34; P<0.001), urea (r = 0.26, P<0.1) and total plasma protein (r = 0.26, P<0.1), and subsequent residual feed intake over the whole experiment (feedlot plus animal-house phases), but no evidence of associations with genetic variation in residual feed intake. At the start of the feedlot residual feed intake test period plasma levels of glucose, creatinine and aspartate aminotransferase were correlated with residual feed intake over the experiment (r = 0.40, –0.45 and 0.43, respectively, P<0.05), providing evidence of phenotypic associations with residual feed intake, and concentrations of urea and triglycerides were correlated with sire estimated breeding values for residual feed intake (b = 1.20 and –0.08, respectively, P<0.05), providing evidence for genetic associations with residual feed intake. At the end of the experiment, concentrations of plasma insulin, cortisol and leptin were correlated with residual feed intake over the experiment (r = 0.43, –0.40 and 0.31, respectively, P<0.05). Plasma concentrations of urea, insulin and cortisol illustrated trends for an association with sire estimated breeding values for RFI (b = –0.35, 0.98 and 12.19, respectively, P<0.1). The ratio of allantoin : creatinine in urine, as a measure of rumen microbial production, tended to be correlated with residual feed intake in the animal house (r�=�0.32, P<0.1) but not with residual feed intake over the entire experiment (r = 0.10, P>0.05). Neither the ratio of 3-methyl histidine : creatinine in urine, as a measure of rate of muscle breakdown, nor the dry matter digestibility measured in the animal house were correlated with residual feed intake in the animal house (r = 0.04, P>0.05), or residual feed intake over the whole experiment (r = –0.22, P>0.05), and neither were associated with genetic variation in residual feed intake.It is hypothesised that high-RFI (low-efficiency) steers have higher tissue energy requirements, are more susceptible to stress and utilise different tissue substrates (partly as a consequence of differences in body composition) to generate energy required in response to exposure to a stressful stimulus.

Feed intake and efficiency in beef cattle: overview of recent Australian research and challenges for the future

In the last 10 years, there have been 3 major research and development projects in Australia on the efficiency of feed utilisation by beef cattle. The primary objective of these projects has been to examine individual animal variation in feed efficiency and its exploitation for genetic improvement in beef cattle. The results of these projects indicate that genetic variation in feed efficiency exists in Australian beef herds, that feed efficiency is moderately heritable and that the potential exists to reduce the cost of beef production through selection for efficient cattle. These results have been further developed for industry application through the generation of BREEDPLAN estimated breeding values for net (or residual) feed intake (a feed efficiency trait) for Angus and Hereford–Polled Hereford breeds. Although economic analyses have indicated substantial benefit from selection for feed efficiency, the high initial cost of identifying animals which are superior for feed efficiency is a barrier to rapid adoption of the technology. Developing cost-effective methods of implementing the feed efficiency technology is thus an on-going research activity. Challenges for the future include: the development and use of more sophisticated statistical analyses procedures (such as random regression) for feed intake and efficiency evaluation; development of accurate methods of assessing individual animal feed intake at pasture; the adoption of a whole-production system approach to feed utilisation; and better integration of the disciplines of genetics and nutrition. The outcomes from research in the efficiency of feed utilisation in beef cattle have wider applications, not only in other livestock species, but also in human energetics, such as the control of obesity.

Economic evaluation of beef cattle breeding schemes incorporating performance testing of young bulls for feed intake

A model beef cattle breeding scheme consisting of a breeding unit and a commercial unit was used to evaluate the impact on genetic gain and profitability of incorporating feed intake measurements as an additional selection criterion in breeding programmes. Costs incurred by the breeding unit were compared with returns generated in the commercial unit, with bulls from the breeding unit being used as sires in the commercial unit. Two different market objectives were considered — a grass-fed product for the Australian domestic market, and a grain-fed product for the Japanese market. Breeding units utilising either artificial insemination or natural service were also considered. A base scenario was modelled incorporating a range of criteria available to Australian cattle breeders. A second scenario incorporated selection of sires for the breeding unit using a 2-stage selection process, with a proportion of bulls selected after weaning for measurement of (residual) feed intake. Measurement of feed intake of bulls improved accuracy of breeding unit sire selection by 14–50% over the equivalent base scenario, and genetic gain in the breeding objective was improved for all scenarios, with gains ranging from 8 to 38% over the base scenario. After accounting for the cost of measuring feed intake ($150–450), additional profit was generated from inclusion of feed intake measurement on a proportion of bulls for all breeding schemes considered. Profit was generally maximised where 10–20% of bulls were selected at weaning for measurement of intake, with improvement in profit ranging from 9 to 33% when optimal numbers of bulls were selected for intake measurement.

Blood cell profiles of steer progeny from parents selected for and against residual feed intake

This study examined whether a single generation of divergent selection for residual feed intake was accompanied by differences in red and white blood cell parameters that could assist in the early identification of animals likely to perform well in a test for residual feed intake. Two cohorts of steer progeny born in 1996 (n = 74) and 1998 (n = 120) of parents selected for low residual feed intake (high efficiency) and high residual feed intake (low efficiency) were used. The steers grazed on pasture before feedlot entry and subsequent feed intake test. Blood samples were collected from the 1998 born cattle at pasture the day before feedlot induction, and for all cattle, at the start, middle and end of their feed intake test. Statistically significant regressions between sire estimated breeding value for residual feed intake and white blood cell count, haemoglobin level, haematocrit and percentage monocytes measured on their progeny over a feed intake test were evidence for a genetic association between these blood parameters and residual feed intake. Of the cell parameters measured in the blood samples collected from cattle at pasture before feedlot entry, only white blood cell count (r = –0.20, P<0.05) and neutrophil count (r = –0.29, P<0.01) were correlated with steer residual feed intake in the feedlot, none (P>0.05) were correlated with sire estimated breeding value for residual feed intake. Cell parameters measured in the blood samples collected from cattle at the start of the feed intake test were not correlated (P>0.05) with steer residual feed intake in the feedlot or with sire estimated breeding value for residual feed intake. It is doubtful that blood parameters in a blood sample taken at pasture before feedlot entry or at the start of a feed intake test can be used to predict residual feed intake of individual steers or sire progeny groups in feed intake tests.

Genetic and phenotypic variance and covariance components for feed intake, feed efficiency, and other postweaning traits in Angus cattle

Records on 1,180 young Angus bulls and heifers involved in performance tests were used to estimate genetic and phenotypic parameters for feed intake, feed efficiency, and other postweaning traits. The mean age was 268 d at the start of the performance test, which comprised 21-d adjustment and 70-d test periods. Traits studied included 200-d weight, 400-d weight, scrotal circumference, ultrasonic measurements of rib and rump fat depths and longissimus muscle area, ADG, metabolic weight, daily feed intake, feed conversion ratio, and residual feed intake. For all traits except the last five, additional data from the Angus Society ofAustralia pedigree and performance database were included, which increased the number of animals to 27,229. Genetic (co)variances were estimated by REML using animal models. Direct heritability estimates for 200-d weight, 400-d weight, rib fat depth, ADG, feed conversion,and residual feed intake were 0.17 +/- 0.03, 0.27 +/- 0.03, 0.35 +/- 0.04, 0.28 +/- 0.04, 0.29 +/- 0.04, and 0.39 +/- 0.03, respectively. Feed conversion ratio was genetically (r(g) = 0.66 ) and phenotypically (r(p) = 0.53) correlated with residual feed intake. Feed conversion ratio was correlated (r(g) = -0.62, r(p) = -0.74) with ADG, whereas residual feed intake was not (rg = -0.04, r(p) = -0.06). Genetically, both residual feed intake and feed conversion ratio were negatively correlated with direct effects of 200-d weight (r(g) = -0.45 and -0.21) and 400-d weight (r(g) = -0.26 and -0.09). The correlations between the remaining traits and the feed efficiency traits were near zero, except between feed intake and feed conversion ratio (r(g) = 0.31, r(p) = 0.23), feed intake and residual feed intake (r(g) = 0.69, r(p) = 0.72), and rib fat depth and residual feed intake (r(g) = 0.17, r(p) = 0.14). These results indicate that genetic improvement in feed efficiency can be achieved through selection and, in general, correlated responses in growth and the other postweaning traits will be minimal.

Body composition and implications for heat production of Angus steer progeny of parents selected for and against residual feed intake

Yearling Angus steer progeny of parents selected for low residual feed intake (RFI; high efficiency) or high RFI (low efficiency) were evaluated for feed intake, growth and differences in body composition. RFI is the difference between actual feed intake and expected feed intake based on an animal’s size and growth over a test period. Individual intakes of a high grain content ration and growth rates were recorded for 140 days and then the steers were slaughtered for measurement of body composition. All internal organs and non-carcass fat depots were removed, weighed and ground for chemical analysis. Carcasses were kept overnight in the chiller and the left half of every carcass physically dissected into retail cuts, and then into total fat, lean and bone. Carcass fat and lean were then combined and ground for chemical analysis. Steers from low RFI parents ate less (P<0.05) than the steers from high RFI parents, for similar rates of growth. Improvement in RFI was accompanied by small changes in body composition towards greater lean and less fat in the progeny of low RFI parents. Correlations of sire estimated breeding values for RFI with end of test whole body chemical protein, chemical fat and a principal component that condensed information on fat and lean body composition at the end of the test, were statistically significant. These confirmed there was a genetic association between body composition and RFI, with fatness being associated with higher RFI (i.e. lower efficiency). However, the correlations were small and suggested that less than 5% of the variation in sire RFI was explained by variation in body composition of their steer progeny. There was no evidence that a difference in the chemical composition of gain over the test explained the greater intake of metabolisable energy (ME) by the high RFI steers. The results suggest that the difference in ME intake following a single generation of divergent selection for RFI was due to metabolic processes rather than to changes in body composition.

Meat quality and the calpain system of feedlot steers following a single generation of divergent selection for residual feed intake

Residual feed intake (RFI) is calculated as the difference between an animal’s actual feed intake and its expected feed intake based on its size and growth over a specified test period. Following a single generation of divergent selection for postweaning RFI, Angus steers and Angus × Hereford, Angus×Poll Hereford and Angus × Shorthorn crossbred steers born in 1996 and 1997 were fed in a feedlot. Cohorts of steers were slaughtered at the same age and had attained similar (P&gt;0.05) final liveweights: 467 kg for steers selected for low RFI (high efficiency; HE, n = 91) and 459 kg for steers selected for high RFI (low efficiency; LE, n = 98). The HE and LE steers had similar (P>0.05) carcass weight (247 and 244 kg), dressing percentage (53.1 and 53.2&percnt;) and eye-muscle area (58.9 and 60.3 cm 2 ). The HE steers had slightly less subcutaneous fat over the rib than the LE steers (9.2 v. 10.1 mm, P&lt;0.05), and there was a trend towards less fat over the rump of HE steers (11.5 v. 12.1 mm, P = 0.10). For meat samples taken from the M. longissimus dorsi (LD) there were no differences (P>0.05) between the HE and LE steers in content of intramuscular fat (5.4 and 5.3% fresh weight), marbling scores, meat colour and fat colour. There were also no differences (P>0.05) between HE and LE steers in shear force and compression values for samples of LD aged for 1 day (4.6 and 4.6 kg shear force, 1.45 and 1.44 kg compression), or for 14 days (3.8 and 3.5 kg, 1.36 and 1.32 kg). Myofibril fragmentation index (MFI) measures the breakdown of these structural elements which occurs as an initial step in the process of protein degradation and meat tenderisation. MFI was lower (i.e. less fragmentation; P<0.05) in LD samples from HE steers than from LE steers, both in samples aged for 1 day (67.7 v. 72.5 units) and in samples aged for 14 days (87.8 v. 91.1 units). The rate of decline in MFI between 1 and 14 days post slaughter was similar in the LD samples from both lines of steers. There were no differences (P>0.05) between HE and LE steers in the activity of m-calpain and &micro;-calpain in LD immediately after slaughter (HE steers: 1.9 and 2.3 units, LE steers: 1.8 and 2.1 units). The level of calpastatin in LD from the HE steers was 13% higher than in the LD from the LE steers (5.2 and 4.6 units respectively, P<0.05). Rate of myofibril fragmentation was positively correlated (P<0.01) with the ratios of both m-calpain and µ-calpain to calpastatin, but not (P>0.10) with levels of either calpain or calpastatin. A single generation of divergent selection for RFI produced differences in calpastatin and myofibril fragmentation that may, with on-going selection for low RFI, negatively affect meat tenderness.

Factors influencing dystocia and prediction of dystocia in Angus heifers selected for yearling growth rate

Data on 914 Angus heifers and their calves that had been selected for yearling growth rate (from birth to 1 year of age) were used to (i) evaluate the effect of dystocia on subsequent cow and calf performance, (ii) identify factors influencing dystocia, and (iii) develop and validate equations for predicting dystocia. Records on heifers born in the high, control, and low growth selection lines from 1975 to 1990 and their calves were used. Calving was classified as normal (no assistance), with a code of 0, or difficult (requiring assistance), with a code of 1. The incidence of dystocia was 4.5%, 9.7%, and 6.2% in the high, control, and low lines, respectively, with the difference between the high and control lines being significant (P < 0.05). Dystocia resulted in a significant reduction in calf survival to weaning (97% for normal v. 85% for difficult calvings). Of all the calving and pre-calving traits studied, the ratio of calf birth weight to heifer weight accounted for the highest variation in dystocia in the control (19.6%), low (15.2%), and high (5.4%) lines. The total variation explained by models generated by stepwise regression and discriminant analyses ranged from 5.4% to 36.8%. Prediction equations developed by discriminant analysis using traits measured prior to calving had high accuracy of predicting normal calvings (72.6%–90.3%), when tested on independent data sets. However, the sensitivity (ability to identify those heifers having difficult birth) of the equations was low (0%–40%). These results imply that the approach to be used to reduce dystocia and minimise its effects is to develop an overall management strategy involving both planning of mate selection at joining and supervision at calving.

Potential for selection to improve efficiency of feed use in beef cattle: a review

Evidence for genetic variation in feed efficiency of beef cattle is reviewed in this paper, and ways in which this variation might be used in selection programs to improve beef cattle in Australia are discussed. Efficiency of beef production systems is determined by feed and other inputs of all classes of animals in the production system as well as outputs in terms of slaughter progeny and cull cows. Different indices have been used to express aspects of efficiency on cattle over certain periods of the production cycle. Use of these indices is discussed, and then evidence for genetic variation in both growing animals and mature animals is reviewed. Genetic variation in feed efficiency exists in both growing and mature cattle, although information is lacking to determine whether variation in total production system efficiency exists. The physiological basis for observed variation in feed efficiency is discussed, with differences in requirements for maintenance, body composition, proportions of visceral organs, level of physical activity, and digestion efficiency identified as possible sources of variation. Selection to improve efficiency might be achieved by measuring feed intake of growing animals and utilising genetic correlations that are likely to exist between efficiency of growing animals and mature animals. Measurement of feed intake might occur in central test stations, or methods may be developed to measure feed intake on-farm. Ways of utilising information generated in genetic evaluations are discussed, and it is concluded that estimated breeding values for feed intake after a phenotypic adjustment for growth performance would be most practical, although not theoretically optimal. Such estimated breeding values would best be used in an economic selection index to account for genetic correlations with other traits, including feed intake of the breeding herd, and the economic value of feed in relation to other traits. Future research should be directed towards understanding the genetic relationships between feed intake and other traits in the breeding objective, and to find ways to reduce the cost of measurement of feed intake, including a search for genetic markers.

Molecular characterisation of a Rhodococcus ohp operon

The ohp operon of Rhodococcus strain V49 consists of five genes, ohpR, ohpA, ohpB, ohpC and ohpD which encode putative regulator and transport proteins and confirmed monooxygenase, hydroxymuconic semialdehyde hydrolase and catechol 2,3-dioxygenase enzymes, respectively. These enzymes catalyse the conversion of 3-(2-hydroxyphenyl)propionic acid to the corresponding linear product via a meta-cleavage pathway. Confirmation that the ohp gene cluster formed an operon was provided by gene disruption during which expression of Bacillus levansucrase was confirmed in Rhodococcus. Following biochemical assays of cell-free extracts from recombinant Escherichia coli expressing ohpB (monooxygenase), ohpC (hydroxymuconic-semialdehyde hydrolase) and ohpD (catechol 2,3-dioxygenase), the ortho-hydroxyphenylpropionic acid catabolic pathway in Rhodococcus strain V49 (ATCC 19070) has been predicted.

Optimum postweaning test for measurement of growth rate, feed intake, and feed efficiency in British breed cattle

The optimum duration of test for measurement of growth rate, feed intake, feed conversion, and residual feed intake was examined using postweaning feed intake and weight data from 760 Angus, Hereford, Polled Hereford, and Shorthorn heifer and Angus bull progeny from 78 sires. Variance components, heritability, phenotypic and genetic correlations, and the efficiency of selection using shortened tests compared with a 199-d test were used as criteria to assess the optimum test length. The results indicated that a 35-d test was sufficient for measurement of feed intake, whereas a 70-d test was required to measure growth rate, feed conversion, and residual feed intake without compromising the accuracy of measurement. When a 70-d test is used to measure growth rate, feed conversion, and residual feed intake there is minimal loss in accuracy when weights are collected every 2 wk instead of weekly, but a further increase in the interval between weights to 5 wk caused a decline in the accuracy of the test. Therefore a 70-d test with cattle weighed every 2 wk seems to be optimal for measuring these traits in British breed cattle.

Selenium concentrations in tissues of sheep given a subcutaneous injection of barium selenate or sodium selenate

Young sheep were allocated to 6 treatment groups, each of 8 ewes and 8 wethers. Treatments given were nil, 0.1, or 0.5 mg selenium (Se)/kg body weight as a subcutaneous injection of sodium selenate (Na2SeO4), and 0.8, 1.4, or 2.9 mg Se/kg body weight as a subcutaneous injection of barium selenate (BaSeO4). At 14, 28, 56, and 112 days after treatment, 2 ewes and 2 wethers from each group were slaughtered and samples of blood, liver, kidney, cardiac and skeletal muscle, lymph nodes, and faeces were collected for Se assay. On days 0, 1, 3, 7, 13, 27, and 55 blood and spot faecal samples were taken for Se assay from the 24 sheep selected for slaughter on day 112. In sheep given Na2Se04 there was a rapid but transient increase in the mean Se concentration in tissues, particularly the liver of sheep given the highest dose of Na2SeO4. In these sheep on days 14,28,56, and 112 the respective mean liver concentrations were 169, 62,25, and 6.9 �mol/kg DM: the mean value on day 14 was 15 times the mean value in untreated sheep. In sheep given BaSeO4 there was a gradual increase in mean Se concentration of tissues during the experiment. Faecal Se concentrations increased in sheep given the Se injections. The marked but transient increase in liver Se concentrations in sheep given Na2SeO4 suggests that this organ provides an important protective mechanism against toxicity by readily accumulating and excreting Se into the gut. Our results indicate that the BaSeO4 doses were unlikely to cause Se toxicity in young sheep or result in Se residues in tissues above those recommended for human consumption. The BaSeO4 should be administered subcutaneously in the neck or other sites of the body not sold for human consumption, since deposits of BaSeO4 remain at the site of injection for at least 112 days and may be dangerous if inadvertently consumed.

The DNA sequence and minimal replicon of the Corynebacterium glutamicum plasmid pSR1: evidence of a common ancestry with plasmids from C. diphtheriae

The complete nucleotide sequence of pSR1, a 3 kb multicopy cryptic plasmid from Corynebacterium glutamicum ATCC 19223 has been determined. pSR1 is unrelated to the 4.4 kb Brevibacterium lactofermentum plasmid pBL1 and shows no DNA sequence conservation with plasmids from Staphylococcus. Transposon insertion and deletion mutants located the minimal replicon to within a 2.1 kb NcoI-BclI restriction fragment. This region contains a single large open reading frame, ORF2, flanked at the 5' end by a series of inverted repeat sequences which may modulate its expression, and at the 3' end by a region which may contain a replication origin. ORF2 (position 1633-2636) with a maximum coding potential of 36 kDa is essential for pSR1 replication and was designated the rep gene. The predicted ORF2 protein product exhibits 47% identity over a length of 343 amino acids with a replication-associated ORF in the C. diphtheriae plasmid pNG2, many of the changes being in the third base position. This observation suggests that pSR1 and pNG2, which are two plasmids from environmentally separated Corynebacterium species, may share a common ancestral rep gene.

A C-terminal deletion in Corynebacterium glutamicum homoserine dehydrogenase abolishes allosteric inhibition by L-threonine

In Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum, homoserine dehydrogenase (HD), the enzyme after the branch point of the threonine/methionine and lysine biosynthetic pathways, is allosterically inhibited by L-threonine. To investigate the regulation of the C. glutamicum HD enzyme by L-threonine, the structural gene, hom, was mutated by UV irradiation of whole cells to obtain a deregulated allele, homdr. L-Threonine inhibits the wild-type (wt) enzyme with a Ki of 0.16 mM. The deregulated enzyme remains 80% active in the presence of 50 mM L-threonine. The homdr gene mutant was isolated and cloned in E. coli. In a C. glutamicum wt host background, but not in E. coli, the cloned homdr gene is genetically unstable. The cloned homdr gene is overexpressed tenfold in C. glutamicum and is active in the presence of over 60 mM L-threonine. Sequence analysis revealed that the homdr mutation is a single nucleotide (G1964) deletion in codon 429 within the hom reading frame. The resulting frame-shift mutation radically alters the structure of the C terminus, resulting in ten amino acid (aa) changes and a deletion of the last 7 aa relative to the wt protein. These observations suggest that the C terminus may be associated with the L-threonine allosteric response. The homdr mutation is unstable and probably deleterious to the cell. This may explain why only one mutation was obtained despite repeated mutagenesis.

Nucleotide sequence and organization of the upstream region of the Corynebacterium glutamicum lysA gene

Maximum expression of the Corynebacterium glutamicum lysA gene is dependent upon the presence of a 2.3 kb region immediately 5' of the lysA reading frame. Subcloning and functional analysis of the upstream region implied that this region contained the lysA promoter. Sequence determination of the upstream region revealed a single open reading frame, orfX, in the same orientation as lysA. The orfX coding sequence exhibited all the sequence characteristics of a gene with the potential for a 550-amino-acid polypeptide product. Expression of lysA is coupled to that of orfX via a common promoter located immediately 5' of orfX. The RNA start site has been determined by S1 nuclease mapping. Both the orfX and the lysA gene are expressed as a single 3.0 kb RNA transcript. These data indicate that orfX and lysA are genes within a two-gene operon. Expression of the lysA gene is not subject to regulation by lysine. The orfX gene product was shown not to be directly linked to the lysine biosynthetic pathway, nor is it the enzyme incorporating DAP into the peptidoglycan precursor.

The molecular structure of the Corynebacterium glutamicum threonine synthase gene

The minimal region encoding the Corynebacterium glutamicum threonine synthase structural gene and its promoter was mapped by deletion analysis and complementation of the C. glutamicum thrC allele to a 1.6 kb region of the recombinant plasmid pFS80. The nucleotide sequence of this and flanking DNA was determined. The transcription and translation start points were identified by S1 mapping analysis and amino-terminal protein sequencing, respectively. The thrC gene encodes a 54481-Dalton polypeptide product. Translation of the thrC mRNA initiates only six nucleotides downstream from transcription. The length of the mRNA transcript is consistent with a single gene transcription unit. The C. glutamicum thrC gene is expressed independently of the other threonine-specific genes hom and thrB.

Characterization of the ColE1 mobilization region and its protein products

A third of the 6.6 kb genome of ColE1 is devoted to mobilization (mob) genes necessary to promote its specific transfer in the presence of conjugative plasmids. The mob region is genetically complex: two mob genes are entirely overlapped by a third. Oligonucleotide-directed mutagenesis was used to insert an amber codon into one of the overlapped genes and make possible a full complementation analysis of mob. Four mob genes essential for mobilization by R64drd11 were thus identified. Fragments of mob were subcloned under control of the Ptac promoter in a suitable vector, overexpressed in minicells and the mobilization proteins visualized. A comprehensive alignment of the mob region of ColE1 with those of its close relatives ColK and ColA demonstrating that the four essential mob genes are conserved is also presented.

Nucleotide sequence and fine structural analysis of the Corynebacterium glutamicum hom-thrB operon

The complete nucleotide sequence of the Corynebacterium glutamicum hom-thrB operon has been determined and the structural genes and promoter region mapped. A polypeptide of Mr 46,136 is encoded by hom and a polypeptide of Mr 32,618 is encoded by thrB. Both predicted protein sequences show amino acid sequence homology to their counterparts in Escherichia coli and Bacillus subtilis. The promoter region has been mapped by S1-nuclease and deletion analysis. Located between -88, RNA start site and -219 (smallest deletion clone with complete activity) are sequence elements similar to those found in E. coli and B. subtilis promoters. Although there are no obvious attenuator-like structures in the 5'-untranslated region, there is a dyad-symmetry element, which may act as an operator.

Blood pressure and urinary sodium in black American adolescents

For 56 black American adolescents ranging in age from 13 to 19 years, 24-hour urinary sodium excretion was compared with blood pressure. The volunteers came from families of middle to low economic levels. Their body weight varied from 70 to 129 percent of ideal body weight. The average systolic pressure of all the subjects was 112.1 mmHg with a standard deviation of 9.5 mmHg; mean diastolic pressure was 69.6 mmHg with a SD of 8 mmHg. The average 24-hour urinary sodium excretion of the total population was 131.5 mEq/24 h with a SD of 59 mEq. For the 29 male subjects, the mean value was 137 mEq/24 h (range, 30 to 309 mEq) and for 27 female subjects, 126.3 mEq/24 h (range, 40 to 197 mEq). The average urinary excretion among these groups was not significantly different (P > .05) and the urinary Na/K ratio of the total group was 4.3 with a SD of 2.0. This ratio among various age and sex subgroups was not significantly different (P > .05). Urinary sodium excretion values were taken as a reflection of dietary salt intake among these volunteers. The data suggest that the black adolescents studied do not consume excess sodium and contradict the belief that blacks eat excess sodium. Further, these baseline data must be considered among the factors responsible for the development of hypertension.

Virus-induced diabetes in autoimmune New Zealand mice

Infection of autoimmune New Zealand mice with the D variant of encephalomyocarditis (EMC) virus results in beta-cell damage and clinical diabetes. The induction of diabetes in parental NZB and NZW strains was independent of sex. However, the susceptibility to virus-induced diabetes in their F1 offspring was sex dependent. This susceptibility was significantly higher in male (NZB X NZW) F1 mice as compared with female F1 mice. Castration of male F1 mice significantly reduced the susceptibility to diabetes. These results suggest that parental NZB and NZW strains have recessive genes at different loci which do not allow sex hormones to influence the susceptibility to diabetes. It is concluded that both the genetic background of the host and sex hormones influence the development of virus-induced diabetes in autoimmune New Zealand mice.

Virilizing lipid cell tumor of the ovary: light and electron microscopic studies

Lipid cell tumor of the ovary is among the rarest tumors belonging to the virilizing group of ovarian neoplasms. A lipid cell tumor of the ovary is described in an 18-year-old woman with secondary amenorrhea, hirsutism, and frank virilization. Current diagnostic features, preoperative and postoperative androgen determinations, and histomorphological and ultrastructural studies are presented. Prompt diagnosis and treatment are emphasized in this potentially malignant and disfiguring androgenic tumor that is readily amenable to surgery.

Insulin binding and degradation by human erythrocytes at physiological temperature

When evaluated at 15 C, insulin binding to human erythrocytes is similar to that of human adipocytes fibroblasts, monocytes and placental membranes. At 37 C, however, both insulin binding and degradation by human erythrocytes have a unique character. At this temperature, by the end of the first 30 minutes, erythrocyte specific insulin binding is 3 to 4% of the total available insulin. This percentage of binding remains until the end of the first hour, then for the next four hours, increases linearly to 24%. Intact erythrocytes had negligible degradation of the free 125I-insulin but 56% of the 125I-insulin associated with the erythrocytes was degraded after five hours of incubation at 37 C. The degradation of the bound insulin was determined to be an intracellular property of erythrocytes. This degradation may be the mass action driving force responsible for the increased association of 125I-insulin observed after one hour of incubation. On the other hand, erythrocyte ghosts reached a steady state with 2% of the 125I-insulin bound after 1.5 hours of incubation at 37 C. More than 94% of the bound and free insulins were intact after 5 hours of incubation. These observations indicate, for the first time, that erythrocyte insulin degrading activity is localized inside the cells, not in their membranes, and that the human erythrocyte with its insulin receptors may be one of the important cell types in the metabolism of insulin.

Erythrocytes: a new cell type for the evaluation of insulin receptor defects in diabetic humans

Human erythrocytes have specific insulin receptors. When studied in an insulin radioreceptor assay, erythrocytes from adult-onset, nonobese diabetic subjects bound at least 42 percent less insulin than the normal subjects at insulin concentrations from 0.1 to 100 nanograms per milliliter. The diabetic subjects had 190 insulin receptor sites per cell as compared with the 380 insulin receptor sites per cell for the normal subjects. The deficit of insulin binding in the diabetic subject was thus associated with a fewer number of insulin binding sites per cell with little or no change in affinity. The erythrocyte is a readily available cell for the evaluation of cellular insulin receptor activity.

Characteristics of human erythrocyte insulin receptors

Highly specific insulin receptors have been identified on human erythrocytes. A modification of the monocyte insulin radioreceptor technique permitted distinct separation of human erythrocytes with their bound insulin from the free insulin. When incubated with 80 pg. per milliliter of 125I-insulin (pH 8.0, 3.5 hours, 15 degrees C.), erythrocytes from 17 normal volunteers specifically bound 10 per cent (+/- 1.450 S.D.) of the total 125I-insulin. Less than 15 per cent of the total 125I-insulin bound was nonspecific. Binding of 125I-insulin to human erythrocytes was dependent on pH and temperature. Less than 5 per cent of the insulin available to the plasma membrane was degraded. Both calcium and magnesium enhanced 125I-insulin binding by 100 per cent but had no synergistic effect when mixed in a 1:1 molar ratio. Scatchard analysis of the binding data resulted in a curvilinear plot with characteristics typical of negative cooperative interactions between receptor sites and with an unoccupied site affinity constant of 0.1 X 10(8) M-1. Human erythrocytes have 2,000 insulin binding sites per erythrocyte with 14 sites per square micrometer of surface area. The readily available human erythrocyte, thus, has both specific insulin binding sites and binding characteristics similar to other human cell types. These studies have provided the basis for further clinical investigation of polypeptide hormone receptors on human erythrocytes.

The syndromes of insulin resistance and acanthosis nigricans. Insulin-receptor disorders in man

In six patients with acanthosis nigricans variable degrees of glucose intolerance, hyperinsulinemia and marked resistance to exogenous insulin were found. Studies of insulin receptors on circulating monocytes suggest that the insulin resistance in these patients was due to a marked decrease in insulin binding to its membrane receptors. When these patients were fasted, there was a fall in plasma insulin but no increase in insulin binding, suggesting that the receptor defect was not secondary to the hyperinsulinemia. The clinical features shared by these cases and several similar ones previously reported may be divided into two unique clinical syndromes: Type A, a syndrome in younger females with signs of virilization or accelerated growth, in whom the receptor defect may be primary, and Type B, a syndrome in older females with signs of an immunologic disease, in whom circulating antibodies to the insulin receptor are found.

Defect in insulin binding to receptors in obese man. Amelioration with calorie restriction

With insulin at 0.1 ng/ml, the binding of (125I)insulin in vitro to circulating lymphocytes from 11 obese patients was less than that observed with cells from 10 thin volunteers. Furthermore, with obese cells, unlabeled insulin was less effective in competing with labeled hormone for binding, both at low and high concentrations of unlabeled insulin. These differences were not accounted for by the high concentrations of insulin in the circulation of the obese patients at the time fthe blood was drawn, or by differences in degradation of hormone, or in the characteristics of the cell population. The decrease in binding appears to be due to a lowering of the receptor concentration, but some loss of affinity has not been excluded. Institution of a calorie restricted diet (nine patients) which ameliorated the hyperinsulinemia, produced an improvement in hormone binding. Since the insulin receptors of lymphocytes in metabolic disorders seem to reflect the state of insulin receptors or target cells such as liver and fat, the lymphocytes or other leukocytes appear to be ideal for studies of impaired cell responsiveness to hormones in man.