Evidence Of Compensatory Growth Research Articles

Growth, condition, and swimming performance of juvenile Pacific herring with winter feeding rations

Juvenile fish winter mortality, whether through starvation, predation, or disease, depends in part on feeding history. Assessing mortality risk thus requires metrics that can distinguish well-fed from poorly fed individuals. To investigate the effects of winter feeding and spring re-feeding after winter fasting on young-of-the-year Pacific herring (Clupea pallasii), captive herring were maintained on different feeding rations for 20 weeks under ambient winter and spring conditions and evaluated for differences in size, gut mass, RNA/DNA ratio, body composition, and swimming performance. Lipid and moisture levels were inversely related indicators of feeding history, differing most between full-ration and fasted herring. Fasted herring that were re-fed in spring had evidence of compensatory growth without impacting swimming performance. Minimal growth and reduced gut mass observed even among fully fed herring suggest limits to winter feeding benefits. Metabolically processing stored fat rather than foraging and incurring greater predation risk may thus be an advantageous strategy regardless of winter food availability. Mortalities due to starvation and possibly disease were highest among small herring across rations, supporting the importance of size-dependent winter mortality.

Compensatory growth offsets poor condition in native trout populations

Abstract Compensatory growth—when individuals in poor condition grow rapidly to catch up to conspecifics—may be a mechanism that allows individuals to tolerate stressful environmental conditions, both abiotic and biotic. This phenomenon has been documented fairly widely in laboratory and field experiments, but evidence for compensatory growth in the wild is scarce. Cutthroat trout (Oncorhynchus clarkii subsp.) are cold‐water specialists that inhabit montane streams in western North America where seasonal conditions can be harsh and growth rates vary greatly among seasons. Understanding if individuals compensate for periods of reduced growth and body condition will improve understanding of the requirements of fish throughout their life‐cycle and across freshwater habitats. We quantified compensatory growth of juvenile cutthroat trout using extensive mark–recapture data from 11 stream populations (1,125 individuals) and two subspecies inhabiting a wide range of ecological settings in the northern Rocky Mountains, U.S.A. Our objectives were to determine how growth was linked across seasons and whether individuals behaviourally compensated for depressed body condition via emigration. Fish in relatively poor condition consistently demonstrated compensatory growth in mass during subsequent seasons. In contrast, fish in relatively better condition responded with positive growth in length during the summer signalling these fish may be better suited to headwater environments; no compensatory growth in length was found during the winter. Furthermore, there was no evidence that individual condition mediated migration tendencies of fish to seek more favourable habitat. Across a wide range of environmental conditions, we found consistent empirical support for compensatory growth in mass in the wild. A critical next step is to quantify how changing abiotic and biotic conditions influence the ability of stream fishes to compensate for locally or seasonally challenging conditions, thereby affecting long‐term resiliency, viability, and adaptation in the face of changing environmental conditions.

Larval carry‐over effects from ocean acidification persist in the natural environment

An extensive body of work suggests that altered marine carbonate chemistry can negatively influence marine invertebrates, but few studies have examined how effects are moderated and persist in the natural environment. A particularly important question is whether impacts initiated in early life might be exacerbated or attenuated over time in the presence or absence of other stressors in the field. We reared Olympia oyster (Ostrea lurida) larvae in laboratory cultures under control and elevated seawater pCO2 concentrations, quantified settlement success and size at metamorphosis, then outplanted juveniles to Tomales Bay, California, in the mid intertidal zone where emersion and temperature stress were higher, and in the low intertidal zone where conditions were more benign. We tracked survival and growth of outplanted juveniles for 4months, halfway to reproductive age. Survival to metamorphosis in the laboratory was strongly affected by larval exposure to elevated pCO2 conditions. Survival of juvenile outplants was reduced dramatically at mid shore compared to low shore levels regardless of the pCO2 level that oysters experienced as larvae. However, juveniles that were exposed to elevated pCO2 as larvae grew less than control individuals, representing a larval carry-over effect. Although juveniles grew less at mid shore than low shore levels, there was no evidence of an interaction between the larval carry-over effect and shore level, suggesting little modulation of acidification impacts by emersion or temperature stress. Importantly, the carry-over effects of larval exposure to ocean acidification remained unabated 4months later with no evidence of compensatory growth, even under benign conditions. This latter result points to the potential for extended consequences of brief exposures to altered seawater chemistry with potential consequences for population dynamics.

Effect of quantitative feed restriction on broiler performance

The objective of the current study was to determine the effect of quantitative feed restriction on the performance of broilers. A total of 270 unsexed broilers were randomly allocated to three treatments: with no feed restriction (T1), one week (T2) and two (T3) weeks of feed restriction from 22 days of age and then fed ad libitum until the age of 42 days. Treatments were replicated three times with 30 birds per replicate. Birds were fed with starter, grower and finisher diets. The feed consumed and body weights were recorded every week from the third to the sixth week. The average daily gain (ADG), average daily feed intake (ADFI) and the feed conversion ratio (FCR) were computed for each week. At Week 6, body weights of T3 birds were similar (P>0.05) to those of T1 and T2 birds. There were also no treatment effects on the ADG at Week 6. In addition, no treatment effects (P>0.05) were observed on ADFI at each stage of growth. Since ADFI and FCR were similar among the three groups, it was concluded that feed restriction by limiting the time to eat was not successful. There was also no evidence of compensatory growth in the restricted groups.

Performance of Advanced Juvenile Cobia, Rachycentron canadum, Reared Under Different Thermal Regimes: Evidence for Compensatory Growth and a Method for Cold Banking

ABSTRACT Two trials were undertaken to examine the growth response of juvenile cobia, Rachycentron canadum, at varying temperatures. The initial trial was conducted to determine the effect of various temperatures (18, 23, and 29°C) on weight gain and feed efficiency. The second trial investigated the effect of elevating water temperature in which fish maintained at 18°C and 23°C to a temperature close to their optimum (29°C). The latter study was undertaken in order to determine the effect of thermal shifts upon subsequent growth response of the species. Such information will assist commercial producers in developing various culture guidelines. As anticipated, differences (P < 0.01) in weight gain were recorded among all treatments, although remarkably, feed efficiency did not differ for cobia held at 23°C and 29°C. Following thermal shift, cobia subjected to the largest temperature change (18–29°C) illustrated an immediate growth response, but specific growth rates (SGR) did not exceed that of cobia held at 29°C for the duration of the trial. Nevertheless, when SGR were examined using fish of similar size (i.e., derived from different time points during the study) evidence for growth compensation was obtained. This study illustrates that cobia can be held at reduced temperatures, without detrimental impact on future performance, as a means of maintaining animals at smaller size for production and experimental purposes: “Cold banking.”

Response of olfactory axons to loss of synaptic targets in the adult mouse

Glomerular convergence has been proposed to rely on interactions between like olfactory axons, however topographic targeting is influenced by guidance molecules encountered in the olfactory bulb. Disruption of these cues during development misdirects sensory axons, however little is known about the role of bulb-derived signals in later life, as new axons arise during turnover of the olfactory sensory neuron (OSN) population. To evaluate the contribution of bulb neurons in maintaining topographic projections in adults, we ablated them with N-methyl- d-aspartate (NMDA) in P2-IRES-tauLacZ mice and examined how sensory axons responded to loss of their postsynaptic partners. NMDA lesion eliminated bulb neurons without damage to sensory axons or olfactory ensheathing glia. P2 axons contained within glomeruli at the time of lesion maintained convergence at these locations; there was no evidence of compensatory growth into the remnant tissue. Delayed apoptosis of OSNs in the target-deprived epithelium led to declines in P2 neuron number as well as the gradual atrophy, and in some cases complete loss, of P2 glomeruli in lesioned bulbs by 3 weeks. Increased cell proliferation in the epithelium partially restored the OSN population, and by 8 weeks, new P2 axons distributed within diverse locations in the bulb remnant and within the anterior olfactory nucleus. Prior studies have suggested that initial development of olfactory topography does not rely on synapse formation with target neurons, however the present data demonstrate that continued maintenance of the sensory map requires the presence of sufficient numbers and/or types of available bulbar synaptic targets.

Growth and Digestive Function of Turkeys Surviving the Poult Enteritis And Mortality Syndrome

Stunted growth of poults afflicted by enteritis mortality syndrome (PEMS) may be associated with depressed digestive capabilities. We conducted two experiments to test this hypothesis. Survivors of PEMS were obtained from a research flock that had been purposefully infected at 5 d of age with PEMS inoculum that included turkey corona virus. The PEMS survivors were assigned to Experiments 1 and 2, beginning at 40 and 35 d of age, respectively. Three groups (large, L; medium, M; and small, S) and two groups (L and S) of 20 poults each were selected to represent different degrees of stunting in Experiments 1 and 2, respectively. When the body weights of each group in both experiments were plotted using initial body weight as the starting point, all of the weights fell on the normal growth curve except Group S in Experiment 1. Therefore, there was no evidence of compensatory growth over the period studied. In Experiment 1, apparent fat absorption (AFA) was significantly higher (P < 0.05) for control (85.9%) than for M (78.5%) and S (78.3%) groups, and AME, for the control group was significantly higher than all the PEMS-survivor groups. In Experiment 2, Group L had a higher AFA and AMEn than Group S. AFA and AMEn improved in both groups over time. The digestive capabilities of PEMS survivors were depressed proportionally to the degree of stunting. Impaired fat digestibility and dietary energy utilization in PEMS-afflicted birds are likely contributors to stunted growth and reduced recovery rates.

Effects of different concentrations of monensin and monensin withdrawal upon the control of coccidiosis in the turkey

The efficacy of different concentrations of monensin in turkeys exposed to field isolates of Eimeria and the effect of the withdrawal of monensin from their diet were investigated. Results of a battery study indicated that 66 ppm monensin was effective against three species of Eimeria in the turkey. In floor pens in which poults were exposed to infection, use of 59.5, 79.4, and 99.2 ppm monensin resulted in reduced mortality and improved feed conversion at 3 wk of age compared with birds that had received no medication. Poults given 59.5 ppm monensin weighed more and had a better feed conversion at 3 wk than poults given 79.4 or 99.2 ppm monensin, but at 10 wk no differences in the body weight or feed conversion of poults given different concentrations of drug were apparent. At 14 wk (and from 10 to 14 wk), poults that had been given 99.2 ppm monensin had a lower feed intake and weighed less than birds that had been given 59.5 ppm of the drug but there were no significant differences in feed conversion. There was no significant difference in the weight gain or feed conversion of poults from 10 to 14 wk of age whether monensin was present in the feed or had been withdrawn. No evidence of compensatory growth was found in the present study.

Evaluation of the feeding duration of a phase 1 nursery diet to three-week-old pigs of two weaning weights. NCR-42 Committee on Swine Nutrition.

A regional study involving a total of 618 nursery pigs with 468 continuing through the grower-finisher period evaluated the feeding duration of a Phase 1 starter diet (1, 2, or 3 wk) to 23-d old weanling pigs of two weaning weights (5.5 or 7.5 kg). The study was a 3 x 2 factorial arrangement of treatments in a randomized complete block design conducted in 19 replicates during the nursery period, with 14 replicates continuing through the grower-finisher period. Upon completion of feeding the Phase 1 diet for the experimental period, pigs were fed a Phase 2 diet (total of 5 wk for both Phases), whereupon a corn-soybean meal mixture formulated to .80% lysine was fed during the grower (to 56 kg BW) and a .65% lysine diet to a final body weight of 105 kg. Station effects were significant (P < .05) but station x treatment responses were not (P > .15). Pigs with heavier weaning weights gained faster (P < .01) and consumed more feed (P < .01) during each week of the nursery period. Nursery pig gains (P < .06) and gain: feed ratios improved (P < .01) when the Phase 1 diet had been fed for either 2 or 3 wk for both pig weight groups. There was no interaction response during the nursery period between weaning weight or duration of feeding the Phase 1 diet on daily gains or feed intake measurements; however, pigs in the heavier weight group were more efficient (P < .05) in feed utilization when fed the Phase 1 diet for 2 or 3 wk. During the grower-finisher period, gains were higher (P < .01) with the heavier pig group. When the Phase 1 diet had been fed for either 2 or 3 wk to the pigs of either weight group, gains (P < .01) and feed efficiency (P < .05) were improved. There was no evidence of compensatory growth for the lower weight pig group during the subsequent grower or finisher periods. Pigs with heavier weaning weights reached 105 kg BW approximately 8 d sooner (P < .01) and consumed less total feed (P < .05) from weaning to 105 kg than those in the lower weight group. Feeding the Phase 1 diet for 2 wk to pigs of either weight group reduced the time from weaning to 105 kg BW, but weaning heavier pigs seemed to have a greater effect on postweaning performance than the feeding duration of a Phase 1 diet.

The effect of plane of winter nutrition and sward height on the performance of steers grazing grass/white clover swards

AbstractAn experiment was carried out over 2 years to examine the interactions between two planes of winter nutrition and summer gracing at 5.5 and 7.5 cm compressed sward height on the performance of Limousin X Friesian steers grazing grass/white clover swards. Diets were offered in winter to give liveweight gains of either 0.5 (low) or 0.8 (high) kg d−1. The experiment was repealed over 2 years. Liveweights gains (low 0.50 vs. high 0.84 kg d−1 s.e.d. ±0.044) were achieved in winter 1 and (low 0.55 vs. high 0.91 kg d−1, s.e.d. ±0.041) in winter 2. These differences resulted in animals from the high treatment being 44 and 60 kg head−1 heavier at turn‐out than the low‐treatment animals in years I and 2, respectively. There was evidence of compensatory growth with animals from the low treatment subsequently tending to grow faster than those from the high treatment, with liveweight gains during the period from turn‐out to 84 d of 1.27 vs. 1.18 s.e.d. ±0.65 kg d−1; P= 0–213 and 1.11 vs. 0.95 s.e.d. ±0.062 kg d−1; P=0.015 in summers I and 2 respectively. In general, animals grazing the short sward tended to grow more slowly than those on the tail swards (1.18 vs. 1.27 s.e.d. ±0.065 kg d−1; P= 0.166 and 0.93 vs. 113 s.e.d. ±0.062 kg d−1, P = 0.002) for years 1 and 2 respectively. Growth rates in year 1 were significantly higher than those in year 2. However, increased summer growth rates did not compensate for the differences in live weight established during the winter, and more animals reached slaughter weight in a shorter time from the high than the low treatment. Mean stocking rate on treatments 5.5 and 7.5 over the 2 years were 5.2 and 4.3 animals ha−1: differences were significant in year 2 (P &lt;0.01). The 5.5 cm sward treatment also gave a greater liveweight gain ha−1 than the 7.5‐cm sward treatment in both years with a mean for the two years of 670 vs. 572 kg ha−1 but differences were not significant.

Long-term subclinical infection with Trichostrongylus colubriformis: effects on food intake, diet selection and performance of growing lambs

Growing lambs (mean liveweight 22.4 kg) were used to test for the effects of long-term subclinical infection with Trichostrongylus colubriformis (2500 larvae per day) on the voluntary food intake (VFI), diet selection and performance of sheep given a choice between two foods of different protein content (low versus high). Sheep were either uninfected controls or parasitised for 27 weeks (Group 27P). Additional sheep were infected for either 9 or 18 weeks (before and after the development of complete resistance to parasites, as assessed by faecal egg counts) and then treated with anthelmintic to remove the parasites (Groups 9P and 18P). Group 18P remained uninfected after anthelmintic treatment whereas Group 9P was infected again for the last 9 weeks after a 9 week worm-free period. The VFI declined or remained static from Week 5 up to Week 11/12 of continuous infection, for the 27P and 18P groups. For 9P sheep, VFI recovered within a few days after the anthelmintic administration and was unaffected during re-infection over the last 9 weeks of the experiment. Diet selection changed in such a pattern that the proportion of the high protein food (prop H) in the selected diet started to increase from Week 6 of the infection. The prop H selected remained higher over the interval 10–18 weeks of the continuous infection for 27P and 18P groups than the uninfected controls. There were no significant differences in diet selection among any of the groups beyond Week 18 of the experiment. The infection caused a growth check from Week 7 to approximately Week 12/14 of dosing; there was no evidence of compensatory growth following the development of resistance or recovery. The results are consistent with the view that sheep given a choice between two appropriate foods will modify their diet selection in order to moderate the adverse effects of subclinical nematode infection. The performance and diet selection of all sheep beyond Week 18 of infection suggest that no obvious nutritional penalties are incurred with the continuation of the infection once the animals have become resistant to parasites.

Management of Helicoverpa armigera (Lepidoptera: Noctuidae) on chickpea in southern India: thresholds and the economics of host plant resistance and insecticide application

A study of the influence of the density of larval Helicoverpa armigera (instars 4–6) on the seed yield of chickpea plants growing in large cages indicated that one larva per plant was a critical density as far as economic injury levels are concerned. The results indicated that larval feeding activity during the first 2 weeks of flowering had no effect on yield. There was also no evidence of compensatory growth following insect attack during the flowering stage. These data were adopted to set action thresholds in a large (0.8 ha) field experiment that was designed to investigate the economics of insecticide application in the context of an on-farm chickpea enterprise. The field was managed with bullock-drawn implements and hand labour. Insecticides were applied to three varieties — Annigeri (an insect-susceptible landrace), ICCC 37 (a recently released variety) and ICC 506 (an insect-resistant landrace) — weekly, not at all (controls) and when the larval density exceeded 0.5 or 2.0 per plant. Economic parameters were assembled from village and local market records. Helicoverpa had a marked effect on the yield of the two pest-susceptible varieties, both of which would have made a loss in the context of a chickpea enterprise unless protected by insecticides. Helicoverpa-resistant ICC 506 did not achieve as high a yield as the other two varieties when treated with insecticides but did ‘make a profit’ when no insecticide was applied. The relationship between yield and insect days was virtually identical for Annigeri and ICCC 37. The latter needed five insecticide applications to maximize yield and the former four. The relationships between insect day summations (integrals of population curves) for eggs, and small and large larvae, suggested that eggs were undersampled and were not suitable as an indicator for insecticide applications. The density of small larvae, although probably undersampled, was a suitable indication of the damage likely to be caused by the large larvae they would develop into. A set of insect day summations indicates when insecticides in the current price range (Rs300, 400 or 850 ha −1) need to be applied. The thresholds were verified in neighbouring fields. Three insecticide applications during the following season resulted in a greater than threefold increase in yield (from 0.65 to 2.2 t ha −1).

Compensatory growth of porcine right lungs after chronic rejection of transplanted left lungs

Neonatal lung hypoplasia is frequently a fatal condition often associated with congenital diaphragmatic hernia. Unilateral lung transplantation rarely has been performed for this indication, although it is a potential solution. It is not known whether the transplant needs to function permanently or to act as a bridge until the native lung develops. It is also not known whether the native lung will grow in the face of an immunosuppressed state and chronic rejection of the transplanted lung. We therefore developed a porcine model of left lung rejection to study this. Infant swine underwent left lung transplantation. Chronic rejection occurred in all, resulting in nonfunction of the transplanted lung. The right lungs of these animals were compared with the right lungs of size-matched and age-matched control animals not given immunosuppressive treatment and not undergoing transplantation. There were no differences in terms of the functional residual capacity, airway compliance, and airway resistance among the groups. There was a significant increase in the pulmonary vascular resistance in the animals with transplanted lungs. There was also a significant increase in the lung weight in these animals. Unilateral pneumonectomies were done in 4 infant pigs to serve as controls. Three of the 4 did not survive the operation because of acute pulmonary failure. In conclusion, the study group exhibited evidence of compensatory growth that was not seen in the control animals, as shown by the increase in lung weight. This suggests that contralateral lung growth occurs in a growing animal, despite the effects of immunosuppression therapy and chronic rejection of the transplanted lung.

Trypanosoma vivax in Colombia: epidemiology and production losses.

The present paper reports information obtained between 1982 and 1989 in the tropical lowlands of the Atlantic coast of Colombia. The studies confirmed that Trypanosoma vivax was widely but unevenly distributed within the study area and that incidence ranged from sporadic transmission to localised epidemics in which virtually all susceptible animals become infected within a period of 3 months. Quantitative epidemiological methods substantiated impressions of previous workers that T. vivax infections were associated with low-lying swampy areas and tabanid activity. Overt clinical trypanosomosis was rare in herds in which T. vivax was endemic. However, in these herds primary T. vivax infections were shown to cause subclinical alterations in calves. The infection consistently caused a temporary depression of packed cell volume (PCV) as well as a reduction in growth rate. There was no evidence of compensatory growth at a later stage.

Influence of maternal size on survival and growth of striped bass Morone saxatilis Walbaum eggs and larvae

Previous studies have shown that Chesapeake Bay striped bass Morone saxatilis Walbaum egg weights are directly related to weight of the female parent. We hypothesized that maternal size also may influence larval growth and survival. Striped bass eggs, obtained from hatchery-spawned females weighing <4 and >15 kg, were hatched and the larvae reared in the laboratory to compare growth and survival to 25 days posthatch (dph). Small females tended to produce smaller larvae, which at 5 dph averaged 193 μg dry weight and 5.5 mm standard length (SL) compared to 237 μg and 5.7 mm for larvae from large females. At 25 dph, there was no evidence of compensatory growth and the relative size differences were maintained. Mean weights and lengths of 25 dph larvae from small and large females were 2.99 mg, 11.5 mm and 3.66 mg, 12.3 mm, respectively. Mean weight-specific growth rate was 0.15 · day −1 and did not differ significantly between progeny from small and large females. However, growth-in-length rates did differ. Larvae from large females grew at 0.34 mm · day −1 while larvae from small females grew only 0.31 mm· day −1. The mean survival rate to 25 dph ranged from 72 to 87% and was not related to female size.

Recovery of net primary production in subalpine meadows of Mount St. Helens following the 1980 eruption

The deposition of 5–10 cm of tephra from the 1980 eruption of Mount St. Helens had no more effect than subsequent yearly weather fluctuations on the net primary production of subalpine meadows. The net primary production of areas subject to cold mudflows slowly increased as surviving plants resprouted through the eroded surface and has remained below that of tephra deposition areas. The net primary production of tephra deposition areas fluctuated dramatically (coefficient of variation = 40%) in the seven summers following the eruption. An inverse relationship between net primary production and nutrient concentration of individual species contributed to stability in aboveground nutrient pools from year to year. The dominant community members responded similarly to differences among years in summer precipitation, with little evidence of compensatory growth that would help stabilize community production. Tephra greatly inhibited seedling establishment. Species density (number of species per square metre) and diversity (H′) declined in a community having species that rely on sexual reproduction for persistence and also in experimental tephra addition plots in a more species-rich community. These results indicate that although the short-term effect of tephra deposition on net primary production was minor, the long-term consequence will be of community simplification, which will contribute to fluctuation in net primary production in response to yearly weather patterns.

Effects of Age of Dam on Weight Traits in the Simmental Population

Records on birth weight, weaning weight and postweaning gain from weaning to yearling from 839,292 Simmental calves were used to study age-of-dam effects. Estimates of age-of-dam effects were obtained simultaneously with bull effects using a multiple trait evaluation procedure. Large age-of-dam effects were found for birth weight and for weaning weight for young dams relative to mature (5- to 8-yr-old) cows. Age-of-dam effects for birth weight and weaning weight were smaller in base (non-Simmental) dams than in Simmental dams. Also, age-of-dam effects for birth weight and weaning weight were smaller for female calves than for male caives. Different age-of-dam correction factors should be used for males and females within base and Simmental dams. Age-of-dam effects for postweaning gain were less important than those for birth weight and weaning weight. There was evidence of compensatory growth, especially in calves reared by Simmental dams.

A study of the relationship between plane of nutrition during lactation and certain production characteristics in autumn-calving suckler cows

ABSTRACTHereford ♂ × British Friesian ♀ cows that had calved in September/October and were suckling mainly Charolais ♂ × calves were offered individually one of three planes of nutrition based on their estimated maintenance requirement during their first 150 days of lactation.The mean daily intakes of metabolizable energy were 95·8, 71·5 and 52·1 MJ for the high, medium and low planes of nutrition respectively. Data were collected from 122 lactations. The mean 150-day cumulative milk yields of the cows were 1 355, 1 258 and 1 187 kg for the high, medium and low planes of nutrition respectively (P &lt; 0·001). A i-kg increase in calf birth weight was associated with an increase in 150-day cumulative milk yield of 14·7 ± 2·17 kg (P &lt; 0·001). Losses in live weight and condition score were significantly greater for cows given the low plane of nutrition during lactation (P &lt; 0001).Although there was a significant (P &lt; 0·01) positive correlation between the growth rate of the calves and their dams' nutritional level during the winter there was evidence of compensatory growth at grass, since by the time of weaning in August, the plane of nutrition of the dam during the winter had no significant effect on the weight of the calves.The experiment demonstrates that energy-deficient beef cows will attempt to maintain milk production at the expense of body reserves and that when supplementary solid food is made available to the suckled calves, their weaning weights are unaffected by the plane of nutrition of the dam during the winter.

Anticoccidial Efficacy of Salinomycin (AHR-3096C) and Compatability with Roxarsone in Floor-Pen Experiments with Broilers

Five experiments were conducted to test the anticoccidial efficacy of salinomycin (AHR-3096C, A. H. Robins) at 66 ppm and its compatibility with roxarsone (50 ppm) under floor-pen conditions. Monensin (100, 121 ppm), lasalocid (75, 125 ppm), and shuttle programs of salino-mycin-monensin (66/100 ppm) or monensin-salinomycin (100/66 ppm) were included for comparison. Coccidiosis exposure was provided by using the infected seeder bird technique.Salinomycin reduced the lesion scores significantly and improved the body weight and feed conversion in all the trials as compared to unmedicated groups. All three ionophores effectively reduced the lesion scores. Birds treated with salinomycin-monensin shuttle programs had lesion scores, body weight, and feed conversion that were not significantly different from the salinoniycin treated birds, suggesting tha t this shuttle program could be used satisfactorily for control of coccidiosis. Lesion scores, body weight, and feed conversion data of the 4th and 5th trials suggested that the anticoccidial activity of salinomycin and roxarsone are additive. There was evidence of compensatory growth after withdrawal of salinomycin and monensin but not with lasalocid.

Lack of compensatory mammary growth following hemimastectomy in the guinea pig

1. 1. The right mammary fat pad was removed from virgin guinea pigs. Animals were mated and killed on day 5 or day 12 of lactation. 2. 2. Litter size was not significantly affected by hemimastectomy. 3. 3. At neither stage of lactation was there any increase in the single gland weight or total DNA content of hemimastectomized animals compared with the intact controls (at day 5 mammary weight was significantly lower than in the controls), 4. 4. There were no significant differences in mammary weight or DNA content between intact control animals killed at day 5 and day 12 of lactation. 5. 5. It is concluded that mammary growth is complete by day 5 of lactation. 6. 6. There was no evidence of compensatory growth (hypertrophy or hyperplasia) following hemimastectomy in this species.