Effect of exposure to long photoperiod during the rearing period on the age at first egg and the subsequent reproductive performance in geese

The objective of this study was to investigate the effects of photoperiods longer than 14 h of light:10 h of dark (14L:10D) during the rearing period on the age at first egg laying (AFE) and the subsequent reproductive performance in geese. Sixty-six White Roman geese (18 male and 48 female) were divided into three groups and subjected to different lighting schemes, i.e. natural lighting (NAT; 23 degrees 51'N, 120 degrees 33'E), 14L and 18L. Birds in 14L and 18L groups were exposed to 14L:10D or 18L:6D, respectively, beginning at 19 weeks of age and followed by a photoperiod of 10L:14D from 40 weeks of age. The natural photoperiod, including both dawn and dusk was between 11.5L:12.5D and 14.5L:9.5D. The results showed that the AFE was postponed (P < 0.05). Average weight of the first three eggs laid and the fertility of these eggs were improved (P < 0.05) for the geese in 14L and 18L groups when compared to those raised under natural lighting conditions. Meanwhile, the duration of laying were shifted from spring to autumn, with the peak laying rate in September and November instead of March. It was concluded that geese exposed to the photoperiod longer than 14L:10D for 21 weeks during the rearing period would suppress their AFE. Thereafter, the onset of laying could be induced by being transferred to the photoperiod of 10L:14D. The manipulation of photoperiodic regimes used in this study might have a potential benefit for geese farmers through improved weight and fertility of eggs.     

Effect of feed restriction or feeding high-fibre diet during the rearing period on body composition, serum parameters and productive performance of rabbit does

This study evaluated the effect of different feeding regimes from 11 weeks of age to first parturition on feed intake, leptin, non-esterified fatty acids (NEFA) and total protein serum levels, as well as productive performance in young rabbit does. In addition, body composition was estimated by bioimpedance analysis. Thirty-six 11-week-old does were randomly distributed in three groups. The AL-C group was fed ad libitum a control diet containing 350 g neutral detergent fibre (aNDFom)/kg, 11.6 MJ digestible energy (DE)/kg and 173 g crude protein (CP)/kg, and the does were inseminated at 16 weeks of age. The R-C group was fed 150 g/d of the same diet until 16 weeks of age, one week before artificial insemination (AI) at 17 weeks of age, and then fed ad libitum. The AL-F group was fed a diet containing 475 g aNDFom/kg, 9.4 MJ DE/kg and 174 g CP/kg ad libitum, and was inseminated at 17 weeks of age. During rearing (11-16 weeks), does in the R-C group had the lowest DE (1.54 MJ/d; P<0.003) and digestible protein (DP, 17.9 g/d; P<0.001) intake, as well as the lowest protein (172 g/kg; P<0.05) and energy (5.9 MJ/kg) body contents, leptin concentration at 16 weeks of age (2.48 ng/ml; P<0.001) and fertility (P<0.02) at first AI. Daily feed intake during pregnancy and lactation, as well as prolificacy and litter weight, were similar among groups. The highest percentage of body fat was observed for all the does when were inseminated for the first time (135 g/kg; P<0.001), consistent with the highest leptin (4.48 ng/ml; P<0.001) and total protein serum levels (6.87 g/dl; P<0.001) at this time. Serum NEFA level around parturition was higher (P<0.05) in groups AL-C and R-C (1.11 and 0.85 mmol/l) than in group AL-F (0.71 mmol/l), suggesting a lower lipid mobilization that tended to improve fertility rate for AL-F does on day 11 post-parturition (P<0.09). In conclusion, feed restriction during the rearing period delays reproductive development in young rabbits. In nulliparous does, ad libitum feeding during rearing with a high-fibre diet allows a similar productive performance to that of feeding with a less fibrous diet. Nevertheless, the use of high fibre diets during rearing does not affect feed intake throughout the first pregnancy and lactation.     

Effect of prebreeding maintenance diet on subsequent reproduction by artificial insemination in alpine and Saanen goats

The objective of this study was to investigate the effect of 2 levels of prebreeding nutrition on reproduction in yearling does artificially inseminated (AI) by the intrauterine laparoscopic method. Forty-two does (Alpine = 22 and Saanen = 20) were randomly penned in groups of 7 and were fed 1 of 2 diets. The diets contained 3.2 Mcal DE/d (MAINT) or 3.5 Meal DE/d (HIGH), which was 10 and 20% higher than the National Research Council recommendations for maintenance requirements. The does were on the 2 feed treatments for 8 wk, after which the MAINT group was switched to the HIGH group diet. A week later, they were fitted with Veramix sponges to synchronize estrus. The sponges were removed from 22, 10 and 10 randomly picked does after 17, 22 and 23 d, respectively. All the does showed estrus within 48 h of removing the sponges. Previously frozen Alpine or Saanen semen (0.5 ml) was deposited into the uterus of does exhibiting standing estrus after anesthetizing them with zylazine and ketamine. Pure breeding was practiced. All the does lost weight prior to breeding. Seventeen does (41%) conceived and kidded by AI while the rest returned to estrus about 23 d later. A significant difference (P < 0.05) in the kidding percentage was observed between the 2 breeds (Alpine = 64% and Saanen = 16%), while the kidding percentage between the 2 diets did not differ (P > 0.05). Of the does that kidded, seven (41%) had singletons, eight (47%) had twins, one had triplets and one had quadruplets. Average litter size (kids/doe kidding) by AI was 1.76. Although the does lost weight prior to breeding, this did not affect their reproduction.     

Density-dependent age at first reproduction in the eastern kingbird

Theory predicts that maximal fitness is obtained by individuals who begin to breed immediately upon reaching sexual maturity. However, delayed breeding occurs regularly in some taxa, and in birds and mammals is most often associated with long lifespan and/or limited access to suitable habitats. Delayed breeding is not expected among relatively short-lived species such as migratory passerine birds, but this assumption remains untested in many species. Here we quantify age at first reproduction in an eastern kingbird Tyrannus tyrannus population breeding in an ecological island, and through both observational and experimental approaches, investigate the potential causes for the high frequency of delayed breeding that occurs in this population. Nearly half of the fledged nestlings that returned to the breeding grounds did not breed in their first potential breeding season. Some non-breeders occupied territories, for at least some period, but most remained as non-territorial 'floaters'. Parentage analysis failed to show any reproductive success for female floaters, and only limited success for male floaters, indicating that floating was not a successful reproductive tactic. On the other hand, a strong negative relationship existed between population size and the proportion of young birds that bred in their first year, and non-territorial birds of both sexes quickly filled territory vacancies created by experimental adult removals. Limited breeding habitat and territorial behavior of older birds thus appear to be the main causes of delayed breeding in kingbirds. The frequency of delayed breeding in most species is unknown but of potential significance because failure to incorporate accurate estimates of age at first reproduction in population models may lead to flawed population projections.     

Effects of accelerated growth during rearing on reproduction and lactation in ewes lambing at 13 to 15 months of age

Three trials were conducted using ewe lambs to determine the effects of accelerated growth during rearing on reproduction and lactation. Data were obtained on 113 ewes. Early weaned ewe lambs were randomly assigned to the following prebreeding treatments: (1) thin (T, moderate gain) and (2) fat (F, accelerated gain). They were bred to lamb at 13 to 15 months of age. After breeding, one half of the ewes on the T and F treatments were switched to the other treatment so that postbreeding treatments were TT, TF, FF and FT. Prebreeding treatment did not affect conception rate (T, 95%; F, 96%), but lambing rates were 43, 28 and 27% higher (P<0.05) for F than T ewes in trials 1, 2 and 3, respectively. Daily milk production was higher in T ewes than F ewes for each trial, but the differences were significant only in trial 3. Estimated daily milk yields over the 60-day period were: T ewes, 1482, 1571, 1614 g; F ewes, 1183, 1373, 1321 g for trials 1, 2 and 3, respectively. Number of alveoli also favored T ewes. Switching ewes to the alternate treatment after breeding did not affect reproduction or milk production. Correlations between weight to height ratio and milk yield were negative in trials 1 and 3 but were positive in trial 2. There was no indication that serum T(4) levels affected milk production or reproduction. The results of this study show that accelerated growth during rearing increased lambing rate but may impair milk production. These effects appeared to be fixed by the time the ewes were bred.     

Factors affecting reproduction in rehabilitant female orangutans: young age at first birth and short inter-birth interval

This study investigated the reproductive parameters of free-ranging rehabilitant female orangutans. We aimed to assess the factors that influence these parameters and provide information that could assist with the management of orangutan reintroduction programs. We analyzed the birth records of free-ranging female rehabilitants at Bukit Lawang, Bukit Tigapuluh, Sepilok, Camp Leakey, Kaja Island, Sungai Wain, and Meratus and compared them with reproductive parameters reported in wild and zoo populations. Females’ ages at first birth were 10.6–14.7 years, significantly earlier than those of wild and zoo orangutans. Computed inter-birth intervals (IBIs) calculated by the Kaplan–Meier method were 65.1–90.1 months; the values for Camp Leakey and Bukit Lawang rehabilitants were significantly shorter than those reported for wild Sumatran orangutans. Infant mortality rates were 18–61%; the values for Bukit Lawang and Sepilok were significantly higher than those reported for wild Sumatran and zoo orangutans. In rehabilitants, young ages at first birth and shorter IBIs may result from the high energy intake enabled by provisioning, although the possibility exists that they reflect underestimations of age on arrival at rehabilitation centers. The observed high infant mortality rate may reflect poor mothering skills due to human rearing and/or increased disease transmission. This study demonstrates that accelerated reproductive rates (younger age at first birth and shorter IBI) are common in provisioned rehabilitant females on both Sumatra and Borneo.     

The effect of level of feeding in early gestation on reproductive success in young rabbit does

An experiment examined the effect of restricted feeding during early gestation on later feed intake and on kindling performance in young rabbit does. Nulliparous rabbit does (n=94) were inseminated at 14.5 weeks of age. During the first 10 days of gestation, does were fed individually either to appetite (AL) or 1.35 times maintenance requirement (R). After 10 days of gestation, all animals were fed to appetite. Does were weighed at insemination and after kindling. Feed intake was recorded during the first 10 days of gestation and weekly, thereafter. The number of does that kindled, number of live and stillborn kits and litter weight was recorded. The experiment ended after kindling. During feed restriction, AL does consumed 70 g/day more on an average than R does (209 and 139+/-4 g for AL and R, respectively; P<0.001). In the first and second week after feed restriction, compensatory feed intake occurred. Restrictive fed does ate more than AL does (+34+/-5 g/day from days 11 to 17 of gestation; P<0.001; +17+/-6g/day from days 18 to 24 of gestation; P<0.05). In the last week of gestation, feed intake of AL and R was comparable (89 and 100+/-5 g, respectively). At kindling, AL does had consumed 8+/-3g/day more feed over the total gestation period than R does (P<0.04). Feeding level during early gestation neither affected the kindling rate (83%), total litter size (7.9+/-0.4) nor the number of does with stillborn kits (10 versus 9 for AL and R, respectively). Regardless of treatment, in the last week of gestation (days 25-32) the number of does with stillbirth was lower and average birth weight was higher (P<0.01) in does eating more than the average daily feed intake compared to does eating below average. Based on the results of this study it was concluded that feed restriction for 10 days in early gestation does not affect kindling performance of young does, but feed intake in the last week of gestation affects kit survival and birth weight.     

Hatching date influences age at first reproduction in the black-headed gull

In long-lived colonial birds, age at recruitment is an important life-history character. Variation in this parameter may reflect differences in several factors, including competitive ability and breeding strategies. Further, these differences may be due to timing of hatching (for instance through differences in competitive ability). We investigated the age of first-time breeders in relation to hatching date in a black-headed gull Larus ridibundus colony situated in central France, from 1979 to 1993. Age at first breeding was estimated for four groups of individuals (total n=550) according to their hatching date, using a recent capture-recapture methodology which allowed us to estimate recruitment rate without the limiting assumptions of methods relying on simple return rates. The age at first breeding was negatively correlated with the hatching date of individuals: individuals hatched earlier in the season started breeding at a younger age than individuals born later. Proportionally more 2-year-old late-hatched individuals were seen breeding on small peripheral colonies than young early-hatched individuals. This difference disappeared after age 3 years. These results strongly suggest that individuals hatched late in the season start to breed on peripheral colonies before recruiting to their natal colony. A difference of few weeks in hatching date has consequences which can last for several years.     

Evolutionarily stable age at first reproduction in a density-dependent model.

We develop a new model of life history evolution to investigate the evolution of age at first reproduction. Density dependence is taken into account. For a given "species", age of maturity, offspring survival, immature survival, adult survival, fecundity, immature age-classes entering in competition with adults and immature competitive ability are traits adjustable by natural selection, and constitute a particular strategy. On the contrary, the type of intraspecific competition (scramble or contest), strength of competition and inherent net reproductive rate Ro(inh) are fixed (specific) characteristics. As a consequence of fixing Ro(inh), the evolution of any trait will affect trade-offs between others. Evolutionarily stable strategies are determined numerically by using the mathematical concept of Lyapunov exponents. Altogether, we consider 960 different hypothetical "species" (i.e. different combinations of fixed traits). Corresponding ESSs are analyzed with respect to their age at first reproduction, adult survival and immature competitive ability components. They appear to be gathered in three groups. One is intuitive and characterized by a reduction of immature competitive ability and a correlation of age of maturity with adult survival; populations reach mainly equilibria. The two other groups respectively include "species" with low age of maturity but high adult survival, and "species" close to semelparity with delayed maturity; immature competitive ability may not be minimized, and populations possibly exhibit complex dynamics. In conclusion, the hypothesis that the evolution of a demographic parameter modifies trade-offs between others turns out to have important consequences. We argue that life history theory cannot ignore the source and mode-of-operation of density dependence and must regard potential short-term instability as essential.     

Sociality, age at first reproduction and senescence: comparative analyses of birds

Evolutionary theories of senescence suggest that aging evolves as a consequence of early reproduction imposing later viability costs, or as a consequence of weak selection against mutations that act late in life. In addition, highly social species that live in sites that are protected from extrinsic mortality due to predation should senesce at a slower rate than solitary species. Therefore, species that start reproducing late in life should senesce at a slower rate than species that start reproducing early. In addition, social species should senesce more slowly than solitary species. Here I investigate the rate of senescence using an extensive data set on longevity records under natural field conditions to test predictions about the evolution of senescence among 271 species of birds. Longevity records increased with sampling effort and body mass, but once these confounding variables were controlled statistically, there was a strongly positive relationship between relative longevity and relative adult survival rate. Relative longevity after controlling statistically for sampling effort, body mass and adult survival rate, increased with age at first reproduction, but not with degree of breeding sociality. These findings suggest that the evolution of senescence is related to timing of first reproduction, but that the evolution of breeding sociality has played a negligible role in the evolution of senescence.     

Variation in age at first reproduction of male Japanese fluvial sculpin induced by the timing of parental reproduction

The relationships between age and size at reproduction and lifetime reproductive output of male Japanese fluvial sculpin Cottus pollux were estimated by a mark-recapture study. Although all males were physiologically capable of breeding at age 2 years, age at first successful reproduction varied amongst individuals. Males with delayed reproduction had lower net reproductive rate than males that bred at age 2 years on average suggesting that age at first reproduction was a conditional strategy. Males that delayed reproduction were significantly smaller at age 1 and 2 years than males that bred at age 2 years. Despite no significant difference in body size of hatched yolk-sac larvae between the early and late phase of the breeding season, by May of the first year of life, progeny from nests in the early phase had hatched earlier and were larger than those from the nests in the late phase. The results suggested an important effect of timing of reproduction of parents on the growth and subsequent age at first reproduction of their progeny.     

Selection on age at first and at last reproduction in the long‐lived Alpine Swift Apus melba

The way an organism spreads its reproduction over time is defined as a life‐history trait, and selection is expected to favour life‐history traits associated with the highest fitness return. We use a long‐term dataset of 277 life histories to investigate the shape and strength of selection acting on the age at first reproduction and at last reproduction in the long‐lived Alpine Swift. Both traits were under strong directional selection, but in opposite directions, with selection favouring birds starting their reproductive career early and being able to reproduce for longer. There was also evidence for stabilising selection acting on both traits, suggesting that individuals should nonetheless refrain from reproducing in their first 2 years of life (i.e. when inexperienced), and that reproducing after 7 years of age had little effect on lifetime fitness, probably due to senescence.     

Effect of growth and development during the rearing period on the subsequent fertility of nulliparous Holstein-Friesian heifers

This study investigated the effect of growth parameters and metabolic indices during the rearing period on the fertility of nulliparous Holstein-Friesian heifers managed on 17 UK dairy farms. Growth parameters (body weight [BW], heart girth, height, and crown-rump length) and metabolic indices (insulin-like growth factor-I [IGF-I], insulin, glucose, and urea) were measured at approximately 30, 180, and 450 d of age. Fertility data collected included age at first breeding (AFB), number of services per conception, pregnancy rate to first artificial insemination (AI), and age at first calving (AFC). Of the heifers initially bred (n = 428), 4% failed to conceive. The mean pregnancy rate to first AI for heifers that conceived and calved without suffering reproductive loss (n = 392) was 67%, and 6% required >2 inseminations. The mean AFB and AFC was 473 ± 5 d (range, 357 to 936 d) and 791 ± 6 d (range, 636 to 1529 d), respectively. Increased BW, girth, and IGF-I concentration (at 30, 180, and 450 d) and increased skeletal growth (at 180 and 450 d) was associated with a reduced AFB and AFC (P < 0.05 to 0.001). Heifers calving at <775 d had a mean BW gain of 0.82 ± 0.01 kg from 30 to 180 d. Increased glucose concentration at 180 d was associated with a reduced AFB (P < 0.01), but no associations were found between insulin and urea concentrations and any of the fertility traits recorded (P > 0.1). Suboptimal growth associated with an increased AFC could be alleviated by improved monitoring of replacement heifers during the rearing period.     

Individual heterogeneity in life-history trade-offs with age at first reproduction in capital breeding elephant seals

Recruitment age plays a key role in life-history evolution. Because individuals allocate limited resources among competing life-history functions, theory predicts trade-offs between current reproduction and future growth, survival and/or reproduction. Reproductive costs tend to vary with recruitment age, but may also be overridden by fixed individual differences leading to persistent demographic heterogeneity and positive covariation among demographic traits at the population level. We tested for evidence of intra- and inter-generational trade-offs and individual heterogeneity relating to age at first reproduction using three decades of detailed individual life-history data of 6,439 capital breeding female southern elephant seals. Contrary to the predictions from trade-off hypotheses, we found that recruitment at an early age was associated with higher population level survival and subsequent breeding probabilities. Nonetheless, a survival cost of first reproduction was evident at the population level, as first-time breeders always had lower survival probabilities than prebreeders and experienced breeders of the same age. However, models accounting for hidden persistent demographic heterogeneity revealed that the trade-off between first reproduction and survival was only expressed in “low quality” individuals, comprising 35% of the population. The short-term somatic costs associated with breeding at an early age had no effect on the ability of females to allocate resources to offspring in the next breeding season. Our results provide strong evidence for individual heterogeneity in the life-history trajectories of female elephant seals. By explicitly modeling hidden persistent demographic heterogeneity we show that individual heterogeneity governs the expression of trade-offs with first reproduction in elephant seals.     

Postmetamorphic growth,survival, and age at first reproduction of the salamander,hynobius nebulosus tokyoensis Tago in relation to a consideration on the optimal timing of first reproduction

The postmetamorphic growth and survival of the salamander Hynobius nebulosus tokyoentisTago were surveyed in the study site located in Habu village of Hinodemachi, a suburb of Tokyo City, during 1975–1981. A laboratory experiment on the growth rate of juveniles was conducted in parallel with the field survey. The result indicated that this salamander grew at the rate of 8,mm in s.v.l. per year during the juvenile stage, but its growth rate decreased markedly as low as 1.8 mm for males and 1.1 mm for females, once it had attained sexual maturity. According to the “capture-recapture” procedure the annual survival rate after metamorphosis was found to be quite high; that is, approximately 0.7. By using the growth rate of juveniles and the difference between the sizes at metamorphosis and sexual maturity, the age at first reproduction was estimated to be 4 year for males and 5 year for females. From the data obtained in this study, the intrinsic rates of increase (r) were calculated for various values of age at first reproduction under different survival schedules, and the relationship between the age at first reproduction and fitness as measured by r was examined. The result indicated that an optimal age maximizing fitness always existed under respective survival schedules, and the observed age at first reproduction of this salamandei was found to coincide well with the predicted optimal age.     

Effects of restricted feeding of prepubertal ewe lambs on reproduction and lactation performances over two breeding seasons

The aim of this study was to determine the effects of restricted feeding before puberty on reproduction, lactation and offspring growth performance in replacement ewe lambs over two breeding seasons. At weaning, 41 Dorset ewe lambs were assigned to one of three diets: an ad libitum control diet with medium-quality forage (MQF; 13.3% crude protein (CP), 1.81 Mcal metabolizable energy per kg, 42.8% ADF; diet A-MQF); a restricted diet with the same forage as A but less feed concentrate (diet R-MQF); or a high-quality forage (HQF) diet (14.8% CP, 2.15 Mcal ME/kg, 34.7% ADF; diet F-HQF). The quantity of concentrate offered to the group R-MQF and F-HQF ewe lambs was adjusted to obtain 70% of the control ewe lambs' growth rate. The diets were offered for 75 days following weaning to cover the allometric phase of mammary gland development. Prepubertal restriction did not affect (P > 0.10) the gestation rate, number of lambs born or the body weight and body condition score of ewes at lambing or at the end of lactation. Ewes from groups R-MQF and F-HQF tended to produce more milk during their first lactation compared to those from group A-MQF (P = 0.07). During the second lactation, groups R-MQF and F-HQF had better standardized milk production than group A-MQF (P < 0.05), and group R-MQF produced more milk than group F-HQF (P < 0.05). Milk fat and protein content were not affected by treatments (P > 0.10) Fat and protein yield were affected by treatments only at the second lactation (P < 0.10 and P < 0.05, respectively). Lamb birth and weaning weights were not affected by prepubertal restriction of feeding in their mother (P > 0.10). However, the average daily gain of second breeding season lambs was higher for the R-MQF group than the F-HQF group (P < 0.05), and a similar trend was observed for total gain (P < 0.10). Restricted feeding before puberty does not impair future reproductive performance; however, it has a positive impact on lactation and on lambs' growth performance.     

Trade-off between age of first reproduction and survival in a female primate

Trade-offs are central to life-history theory but difficult to document. Patterns of phenotypic and genetic correlations in rhesus macaques, Macaca mulatta—a long-lived, slow-reproducing primate—are used to test for a trade-off between female age of first reproduction and adult survival. A strong positive genetic correlation indicates that female macaques suffer reduced adult survival when they mature relatively early and implies primate senescence can be explained, in part, by antagonistic pleiotropy. Contrasts with a similar human study implicate the extension of parental effects to later ages as a potential mechanism for circumventing female life-history trade-offs in human evolution.     

Relationship between peripheral estrogen concentrations at insemination and subsequent fetal loss in cattle

In a survey on pregnancy rate and embryonic losses in dairy cattle on 6 Israeli farms, cows (n = 78) were divided into 3 groups on the basis of ultrasonography at 21 d post insemination; pregnancy diagnosis at 40 to 50 d post insemination and blood progesterone (P4) levels at 21 d. The groups were either pregnant (P4 level > 1.0 ng/ mL); not pregnant (P4 < 0.5 ng/mL), or showed early embryo loss (P4 > 1.0 ng/mL and the presence of an embryonic vesicle on D 21 but later returned to estrus or were found not pregnant on D 40 to 50). On the day of insemination, peripheral estrogen was significantly higher (P < 0.05) in the early embryo loss group (15.3 +/- 1.1 pg/mL, n = 27) than in pregnant (9.4 +/- 0.6 pg/mL, n = 26) or not pregnant (9.6 +/- 0.7 pg/mL, n = 25) group. The cows on 3 farms which were fed 1 to 2 kg/d of vetch (Vicia sativa), an estrogenic legume, had higher estrogen concentrations on the day of insemination than cows (2 farms) fed other legumes (13.7 +/- 0.64, n = 58 vs 10.7 +/- 0.8 pg/mL, n = 42; P < 0.01). On one of the 3 farms, vetch was replaced with alfalfa after the first year. Following the cessation of vetch feeding the estrogen concentrations in the blood decreased from 32 +/- 5 pg/mL to 14 +/- 2 pg/mL (n = 9). These data suggest that high peripheral estrogen on the day of insemination is associated with early embryonic loss. These data also indicate that estrogen concentrations on the day of insemination can be influenced by diet.