Differences In Reproductive Performance Research Articles

Endogenous gonadal, LH and molt rhythms in tropical stonechats: effect of pair bond on period, amplitude, and pattern of circannual cycles.

To investigate the effects of reproduction and associated stimuli on the circannual cycles of African stonechats Saxicola torquata axillaris birds were held for 29 months in aviaries under a constant equatorial (12.25 h) photoperiod, either singly (10 females and 10 males) or in 10 male/female pairs. The birds of all 3 groups went through circannual cycles in gonadal size, plasma LH and molt, but groups differed with regard to actual reproductive performance. During the second cycle, only one of the singly-held females laid eggs and incubated. In contrast, in the paired females egg-laying and incubation occurred in all but one bird. About 50% of the clutches from paired females contained fertilized eggs confirming the expectation of behavioral differences between the paired and unpaired birds. However, despite differences in reproductive performance there were no differences in either circannual period or duration of reproductive phases. Moreover, there was no correlation between number of broods produced per season and circannual parameters of the paired females. Therefore, the temporal course and, particularly, the period during which reproduction is possible is rigidly determined by an endogenous program that is not influenced by reproductive performance. A rigid program of this kind may be advantageous in the tropics because it prevents prolongation of the breeding season in years with favourable conditions which in turn could jeopardize optimal timing of breeding in the following year and thus reduce lifetime reproductive success.

The effects of nutrition on reproductive performance, lactation and carcass quality of once bred gilts

The once bred gilt system of production has a number of benefits in terms of feed efficiency and welfare, however the system relies on the production of a quality carcass and acceptable reproductive performance. Previous studies have indicated that welfare might be improved if gilts were ad-libitum fed a diet containing 60% Sugar beet pulp (Stewart et al 1993). There was a suggestion however that reproductive physiology may be put at risk using such a diet. The objective of this experiment was to identify differences in reproductive performance using two different energy sources in gestation and to manipulate nutrition during lactation to study the effect on carcass quality.

The effects of nutrition on reproductive performance, lactation and carcass quality of once bred gilts

The once bred gilt system of production has a number of benefits in terms of feed efficiency and welfare, however the system relies on the production of a quality carcass and acceptable reproductive performance. Previous studies have indicated that welfare might be improved if gilts were ad-libitum fed a diet containing 60% Sugar beet pulp (Stewart et al 1993). There was a suggestion however that reproductive physiology may be put at risk using such a diet. The objective of this experiment was to identify differences in reproductive performance using two different energy sources in gestation and to manipulate nutrition during lactation to study the effect on carcass quality.

Effect of Supplemental Fish Meal on the Lactation and Reproductive Performance of Dairy Cows

The influence of high protein diets (21% CP, DM basis), containing varied percentages of RUP, on lactation performance and fertility was evaluated. Sixty-two Holstein cows (65% multiparous) were blocked by age and randomly assigned to a 2 × 2 × 2 factorial design from d 12 to 125 postpartum. Factor 1 was 0 or 3.5% fish meal diet, factor 2 was location (Calan door versus free stall), and factor 3 was parity (first versus second or later). The soybean meal diet consisted of alfalfa hay, corn silage, barley, and soybean meal. The fish meal diet contained 3.5% fish meal (ruminant grade menhaden) that replaced a portion of the soybean meal.Cows fed the fish meal diet (40% RUP) had DMI, BW, and body condition similar to those of cows offered the soybean meal diet (34% RUP). Cows receiving the fish meal supplement tended to have higher milk protein production throughout the trial, higher milk production during the first 6 wk, and significantly lower ruminal ammonia concentrations than cows receiving the soybean meal diet. Differences in reproductive performance were not significant except for a diet by housing location interaction for conception rates from first AI.

Nest Architecture and Reproductive Performance in Tree Swallows (Tachycineta bicolor)

ABSTMACT.-Nests are an important component of parental effort in birds. From 1988 to 1990, I compared the architecture of nests built by subadult and adult female Tree Swallows (Tachycineta bicolor) in boxes in southeastern Michigan in order to determine if there were age-related differences in nest architecture and if these differences were associated with agerelated differences in reproductive performance. Nests built by Tree Swallows were composed of a mat of dry grasses and a nest cup lined with feathers. On average, nest material filled approximately 30% of a nest box. I observed few age-related differences in nest architecture. However, nests built by subadult females were significantly less well feathered than nests built by adult females, but feather score was not correlated with the production of nestlings or fledglings. There were age-related and within-season variations in reproductive performance associated with variations in nest architecture, especially later in the season. Among subadult females that bred later in the season (i.e. after the population median date of clutch initiation), those females that built larger nests (as indicated by total nest volume, depth of material beneath the nest cup, and percentage of nest box filled with material) hatched more eggs per clutch. In 1990, subadult females that bred later in the season and built larger nests (as indicated by depth of material beneath nest cup and percentage of nest box filled with material) produced significantly more hatchlings but significantly fewer fledglings. Among adult females that bred later in the season, those females that built nests that filled a larger percentage of the nest box hatched fewer eggs. Adult females with nests having larger cups produced significantly more fledglings, but those with cups crowded with nestlings (as indicated by a cup index [total egg volume/nest cup volume]) produced significantly fewer fledglings. In 1990, adult females that bred later in the season and built larger nests (as indicated by depth of nest material, total nest volume, percentage of nest box filled with material) and had more-crowded nest cups produced fewer hatchlings and fledged a significantly smaller proportion of hatchlings. These results suggest that nestling hyperthermia in well-insulated nests may affect the reproductive performance of Tree Swallows that breed late in the season. Received 11 January 1993, accepted 1 July 1993.

Phenotypic Evaluation of Fertility Traits and Their Association with Milk Production of Italian Friesian Cattle

The effect of environmental factors on first service conception rate, days from calving to first service, weeks from calving to conception, days from first to second service, and number of services per conception and the relationship of production with reproductive performance were estimated using 1.42million records. The production trait was 305-d mature equivalent milk production. Season and age affected fertility: reproductive performance was lowest for lactations initiated during warm months (May to July) and decreased with parity. The association of production and fertility was antagonistic. High producing cows had 12 d more from calving to first service, .15 lower first service conception rate, .32 more services per conception, and 4.8 wk more from calving to conception than low producing cows in the same herd. The negative effect of production on fertility was reduced by superior herd management associated with high production. The difference in reproductive performance of cows in high and low producing herds represented only about 35% of the difference in the performance of high and low producing cows within herds for all fertility traits. The negative effect of production on fertility for interval between first and second service was totally compensated for by better management.

Effect of Preproduction Lighting Regimes on Reproductive Performance of Broiler Breeders

Four preproduction lighting regimes were assessed to determine their effects on reproductive performance of broiler breeder males and females. These regimes, given in hours light:dark (L:D), were 4:20L:D, 6:18L:D, 8:16L:D (standard), and 10:14L:D. All birds were exposed to a 15:9L:D regime at 20 weeks of age. Rearing birds on the 4:20L:D regime resulted in a delay of sexual maturity of both males and females and also decreased egg production and increased body weight in the females. There were no differences in reproductive performance of males and females reared on the other three lighting regimes.

First Reproductive Success and Individual Productivity in Sandhill Cranes

I determined the age at which sandhill cranes (Grus canadensis) in Florida began successfully reproducing to see if differences in reproductive performance occurred between the behaviorally distinct migratory greater (G.c. tabida), and the non-migratory Florida (G.c. pratensis) subspecies. The earliest and mean age of successful reproduction for both subspecies was 3 and 4.7 years, respectively. The modal age of first successful reproduction was 5 years for Florida sandhill cranes (FSHC) and 4 years for greater sandhill cranes (GSHC). Mean individual productivity for both subspecies was 0.35 young/year

Inbreeding effects among inbred and outbred laboratory colonies of Peromyscus maniculatus

We examined the effects of sibling matings upon reproductive performance among inbred and outbred laboratory colonies of Peromyscus maniculatus. The inbred colony was founded by 12 females collected from one locality in Alberta and bred for 20 generations, with 35–45 pairs each generation. The outbred colony consisted of first-generation mice born of wild-caught females from diverse areas in Alberta. Consistent with theoretical expectations, there were no differences in reproductive performance between sibling and control (outbred) pairs within the inbred colony of mice. In contrast, sibling pairs had significantly fewer young per litter than control pairs within the outbred colony. Reproductive performance measures (proportion breeding, days from pairing to first litter, number of litters, and total number of offspring produced) were also significantly lower among sibling pairs from the outbred colony than among sibling pairs from the inbred colony. Lastly, we predicted that reproductive performance of the control pairs from the outbred colony would be less than that of control pairs from the inbred colony, due to outbreeding depression. Contrary to our predictions, average litter survival rates were greatest among the outbred colony control pairs. We suggest that the benefits of inbreeding or outbreeding extend broadly across the inbreeding–outbreeding continuum in natural populations of northern Peromyscus.

Use of a simulation model to evaluate the influence of reproductive performance and management decisions on net income in beef production

A stochastic dynamic model of reproduction and a deterministic cow-herd economic simulation model were used to evaluate how management decisions and reproductive performance interact to influence net income in a cow-calf operation (1,000 cows) for 1 yr of production. The stochastic model was used to determine herd performance when length of breeding season (45, 70, or 120 d) interacted with three postpartum intervals of anestrus (48, 65, or 90 d) and three conception rates at first service (60, 70, or 80%). Short, moderate, and long postpartum intervals were used to reflect differences in reproductive performance. In addition, replacement heifers were bred beginning either 3 wk ahead of the cow herd or at the same time as the cow herd. Fifty-four simulations were generated. Inputs into the economic model were herd performance, livestock and feed prices, nonfeed costs, and feed requirements for 1 yr of production. Feed requirements were calculated separately for each postpartum interval to reflect three different body condition scores, thin, moderate, and good, to correspond with long, moderate, and short postpartum intervals. Net income was greatest with 70-d breeding seasons when the postpartum interval was short or moderate. When the postpartum interval was long, net income was greatest with 120-d breeding seasons because pregnancy rates, as a result of the long breeding season, were highest and feed costs were lowest for thin cows. Overall, net income was greatest when cows were managed to have postpartum intervals of moderate length. Breeding heifers 3 wk before the cows provided the most economic benefit with long postpartum intervals.

Breeding Performance in the Western Gull: Effects of Parental Age, Timing of Breeding and Year in Relation to Food Availability

(1) We studied age-specific breeding success of western gulls (Larus occidentalis) on south-east Farallon Island, California in relation to annual variation in food abundance, 1983-89. We assessed yearly reproductive performance on the basis of clutch initiation date, clutch size, hatching and fledging success, and the number of chicks raised to independence. We categorized age of parent into three groups: young, middle-aged and old. (2) Mature birds initiated breeding earlier and laid larger clutches; they fledged more chicks than younger birds as a result of hatching a greater proportion of their eggs and fledging a greater proportion of their hatched chicks. The oldest birds generally did not differ from middle-aged in breeding performance. The difference in reproductive performance between young and mature birds was most apparent during years when food availability was reduced. (3) Timing of breeding influenced reproductive performance independently of parental age; reproductive performance decreased throughout the breeding season. Within-season reductions in reproductive performance were most apparent for young breeders and individuals with small clutches or broods. (4) Breeding performance varied significantly among years independently of age of the study animals. Food availability accounted for part of the yearly variation in breeding success. (5) We suggest that clutch/brood size reflects individual quality. Age-specific breeding success in western gulls is best explained by previous breeding experience and individual quality.

The effect of feeding different sources of crude fibre during pregnancy on the reproductive performance of sows

ABSTRACTA long-term experiment was designed to study the effect of feeding different sources of crude fibre during pregnancy on the reproductive performance of sows. The four treatments imposed during pregnancy were: C, a control compound diet; CS, the same control diet with additional chopped straw (0·2 kg/day); CM, the same control diet in which 0·25 kg was replaced daily by 1·5 kg maize silage; and CFR, a compound diet with a higher crude fibre content. In total 567 sows were used. On the treatments C, CM, CS and CFR the number of sows was 147, 142, 147 and 133 respectively. The sows remained on the experiment for five successive parities on a treatment or until the moment of culling. Feeding levels were about 32 MJ digestible energy (DE) per day during the first months of pregnancy and about 40 MJ DE per day in the last month of pregnancy. During lactation the feeding level ranged between 75 and 90 MJ DE per day.In sows giving birth to five litters, the effect of parity was calculated irrespective of the treatments. The optimum litter size was observed in the fourth litter and the percentage of successful services within 10 days post weaning stabilized after the third parity. The live weight of the sows increased gradually up to the fifth parity.Compared with the sows on the control treatment the proportional changes in consumption of the sows on the other treatments were: 0·45 more crude fibre, up to 0·02 more digestible energy and up to 0·06 less digestible protein.There were only slight differences in reproductive performance. The mean number of weaned piglets per sow per year were 19·7, 19·3, 20·1 and 20·2, respectively for the treatments C, CM, CS and CFR. Higher piglet birth weights were observed for sows on the CM treatment and a higher proportion of the culled sows had leg disorders. On the CS treatment a higher number of weaned piglets per litter was observed and this was due to the higher number of piglets born and lower piglet mortality during lactation. The sows on this treatment tended to have more difficulty in becoming pregnant after the third and fourth parities. The sows on the CFR treatment had the highest body weights and had a higher number of litters per year mainly due to lower numbers returning to service and less nonproductive days. The results from this experiment gave no clear evidence that either the inclusion of roughage or a higher crude fibre content in the diet improved reproductive performance.

Effect of premating shearing on reproductive performance in ewe lambs after oestrus synchronization

SUMMARYOne hundred and fifty-four, March-born, lowland ewe lambs, on the Lyons Estate farm, were allocated to a 2×2 factorial experiment. In September 1987, half were shorn and 1 month later the lambs were treated with intravaginal sponges, containing either 60 mg medroxyprogesterone acetate or 40 mg fluorogestone acetate, for 12 days. Following sponge removal, ewes were mated to fertile rams at a ram: ewe ratio of 1:6. There was no significant difference in reproductive performance between the two progestagen treatments (P > 0·05). Premating shearing increased (P < 0·01) conception rate and reduced the percentage of barren ewes (P < 0·01) but there was no effect on litter size. Time of gestation following shearing was increased (P < 0·01) by 1·24 days. Lamb growth rate up to weaning was not affected by the shearing treatment. The results of this trial indicate positive advantages of premating shearing of ewe lambs.

The effect of mate change and new partner's age on reproductive success in the barnacle goose, Branta leucopsis

Mate retention frequencies and correlations between mate change and reproductive performance were estimated in a population of barnacle geese, Branta leucopsis, breeding on the island of Gotland in the Baltic. About 90% of the pairs remained together from one breeding season to the next. Only 2.4% of the pairs divorced, most mate changes being consequences of the death of one partner. Divorces were not forecast by low reproductive success, and seemed to be accidental. In the season before mate change, there was no difference in reproductive performance, measured as clutch size, hatching date, and number of fledged young, between faithful pairs and pairs where one partner was subsequently changed. However, in the first season with a new partner, clutch size and number of fledged young decreased on average. Hence, because mate change led to a reduction in reproductive success, it was concluded that mate retention is advantageous. Our results suggest that this reduction is more likely due to the lower average age or breeding experience of new partners than to the benefits of breeding experience with one particular partner.

Effects of Fat Supplementation and Immature Alfalfa to Concentrate Ratio on Plasma Progesterone, Energy Balance, and Reproductive Traits of Dairy Cattle

Forty-six multiparous Holstein cows were assigned at 5 d postpartum to a completely randomized design employing a 2 × 3 factorial arrangement of treatments. Factors were 0 and 5% added prilled long-chain fatty acids (DM basis) and three forage to concentrate ratios (45:55, 64:36, 84:16). Diets consisted of immature alfalfa silage and a concentrate of shelled corn and soybean meal with or without fat replacing a portion of the corn. Mean plasma concentration of cholesterol was higher for cows fed 5% vs. 0% fat and increased over the first 100 d in milk for all animals regardless of treatment. There were no differences in reproductive performance due to either of the main effects. Mean plasma progesterone was higher due to fat treatment in the mid to late luteal phase of the second postpartum cycle as well as the metestrous to early luteal phase and mid to late luteal phase of the third cycle. Even though progesterone concentrations were higher in cows fed 5% fat during the luteal phase after breeding, the conception rates at this service were not different from those fed 0% fat. The biological significance of increased plasma progesterone concentration was not identified with any postpartum reproductive trait measured in this trial.

Effects of body condition and temporary calf removal on reproductive performance of range cows

The effects of body condition at calving and breeding and temporary calf removal prior to the start of the breeding season on reproductive performance of 323 cows from two breed groups were studied over two breeding seasons. Body condition score at calving was significantly and positively correlated with two body condition indices, which were based on weight-to-height ratio measured at calving and at the start of the breeding season. While the two body condition indices were strongly associated with the age of the cow, the body condition score, based on palpation and visual appraisal, was less affected by the age of the cow. Cows with a body condition score of 3.0 at calving had a shorter calving interval (P<0.02), higher pregnancy rate (P<0.08), and higher number of calves born (P<0.10) than cows which had body condition scores lower than 3.0 at calving. Temporary (48 h) calf removal prior to the start of the breeding season did not have a significant influence on the calving interval, pregnancy rate or the number of calves born nor on the weaning weights of their calves. Differences in reproductive performance between the two breed groups of cows were not significant.

Fecundity, egg size and total egg volume differences in 12 stocks of rainbow trout, Oncorhynchus mykiss Richardson

Abstract. Measurements of egg number, egg size and total egg volume in relation to post-stripped weight, made on the eggs stripped from 12 separately maintained farm stocks of 4-year-old rainbow trout. Oncorhynchus mykiss Richardson, revealed highly significant differences between populations when analysed by regression and covariance statistical techniques. All of the stocks showed increases in fecundity with increasing fish size, with 61% (coefficient of determination or r2) of the variation in fecundity of the 12 stocks explained by the common regression on parental fish size. Comparison of the regressions of the different stocks revealed that the rate of increase of fecundity with increasing fish weight was constant throughout the weight range (i.e. the regressions had similar slopes) although there were highly significant differences in elevation, with some stocks producing almost twice as many eggs as some of the others. By contrast, the relationship of egg size with fish weight was much more variable with three of the stocks showing no significant regression of egg size on fish weight and a further two stocks with data poorly fitted to the regressions. Of the remaining seven stocks only one showed a significant difference in slope of the regression with modest increases in fish weight being associated with large increases in egg size. Only four of the remaining stocks of fish showed significant differences in the elevation of their regressions, i.e. the egg sizes were significantly different after the potentially conflicting influence of fish size was partitioned using covariance techniques. Assessments of total egg volume produced far improved regressions on post-strip weight with 75% (r2) of the variation in the pooled data of the 12 stocks being described by the line of the common regression. In general, there appeared to be a “trade-off” between egg number and size with the most and least fecund fish producing somewhat smaller and larger eggs respectively. All 12 regressions of totai egg volume on fish weight showed a common slope. However, there were significant differences in elevation of the regressions, with some of the stocks of trout producing up to a 55% greater volume of eggs. There appeared to be no relationship between the differences in egg number, size or total egg volume and the type or geograpfiical location of the farms on which the stocks were held. Although it remains to be determined to what extent these differences in reproductive performance are Inheritable, it is recommended that these characteristics should be taken into account by hatcheries in tbe design of long-term broodstock selection programmes for rainbow trout.

Influence of Protein Intake and Feeding Strategy on Reproductive Performance of Dairy Cows1,2

A study was conducted to determine the impact of dietary CP concentration (13 vs. 20%) and feeding strategy (total mixed ration vs. separate feeding of the forage and concentrate) on reproductive performance of 57 early lactation dairy cows. Cows were assigned to one of four treatments in a 2×2 factorial arrangement. Rations composed of 40% forage (50% grass-legume silage:50% corn silage) and 60% concentrate (DM basis) were fed from d 5 to 100 postpartum. Cows fed a total mixed ration had lower ruminal ammonia and plasma urea N concentrations compared with cows fed separately. Feeding strategy groups showed no differences in reproductive performance. Cows fed a 20% CP ration had higher CP intake, higher ruminal ammonia, and higher urea N concentration in plasma and vaginal mucus. There were no differences between low and high CP groups in days to first observed estrus (24 vs. 27), days to first service (55 vs. 59), days open (72 vs 82) or services per conception (1.5 vs. 1.8). Days to first estimated ovulation were longer (22 vs. 17) in the high vs. low CP groups, and there was an interaction between protein intake and lactation number. Cows managed with an intensive program for detection of estrus and for reproductive health did not show differences in reproductive efficiency when fed 13 or 20% CP rations.

Effects of pre-joining shearing, stress, pasture allowance, and haemoglobin type on reproductive performance of Romney and Marshall Romney ewes

Abstract In Experiments 1, 2, and 3, mature Marshall Romney (MR) and control Romney (CR) ewes were shorn 3 – 30 days before joining whereas in Experiment 4, 11/2-year-otd and mature Romney and Border Leicester x Romney ewes were shorn 7 days before joining. In Experiments 1 and 2, MR and CR ewes were single-sire-mated to both MR and CR rams. Haemoglobin (Hb) type of all ewes and rams was determined in these two experiments. In Experiment 3, MR and CR ewes were offered a pasture allowance of either 1.3 or 6.0 kg gr een DM per ewe per day for 32 days before a synchronised oestrus. Comparing experiments, there were no consistent effects of pre-joining shearing on ewes ovulating multiples or ewes lambing multiples. The most consistent response to pre-joining shearing was an increase in ewes lambing. This variable response to pre-joining shearing cannot be explained by differences in strain or age of ewe or interval from shearing to joining, although in Experiment 1 there was an age of ewe (21/2-year-old v. older) by interval from shearing to joining interaction for % ewes lambing and ewes lambing multiples. In Experiments 3 and 4, pasture allowance levels did not influence the reproductive response to pre-joining shearing. Half of the eves in Experiment 3 were ‘stressed’ 7 days before Joining by vigorously moving with dogs for 6 h before and 3 h after shearing. There was an interaction between age of ewe and stress for ewes lambing and ewes lambing multiples. Both traits were depressed m stressed 21/2-year-old ewes but not in older ewes. Differences in reproductive performance between MR and CR ewes were independent of the strain or Hb of the rams to which ewes were mated. MR ewes were 5-7 kg heavier than CR ewes. In Experiment 1, MR ewes had higher percentages of ewes lambing to first service, ewes lambing, ewes ovulating multiples, and ewes lambing multiples than CR ewes. This was almost entirely explained by the higher liveweight of MR ewes. In Experiment 3 there was a pasture allowance by strain of ewe interaction for ewes ovulating multiples and a similar trend for ewes lambing multiples. On a pasture allowance of 1.3 kg green DM per ewe per day MR ewes had more ewes ovulating multiples than CR ewes (28 v. 17%) and similarly for ewes lambing multiples (24 v. 13%). At the higher pasture allowance of 6.0 kg green DM per ewe per day MR ewes had fewer ewes ovulating multiples than CR ewes (16 v. 59%) and fewer ewes lambing multiples (37 v. 49%). Hb type of ewes had no effect on reproductive performance despite Hb BB ewes having a lower liveweight.

Reproductive performance and productive traits of beef bulls selected for different levels of testosterone response to GnRH

In two separate studies, one with four Hereford-Shorthorn and one with three Zebu × British crossbred bulls, the efficacy of using the testosterone response to gonadotrophin-releasing hormone (GnRH; Lutal, Hoechst) to predict differences in reproductive performance was assessed. Young bulls (17 or 29 months of age) selected for low to high (3.1 to 10.3 ng/ml) peak plasma testosterone 2 to 2.5 hours after the intramuscular injection of GnRH (62.5 to 2000 ng/kg LWT) were each later individually joined with groups of 19 to 30 cows in which estrus had been synchronized. In both studies, the rankings of bulls for overall fertility (capable cows pregnant), for libido (estrous cows mounted), and for fertilizing ability (mounted cows pregnant) were in close agreement with rankings for testosterone responses to GnRH. In the Bos indicus bulls rankings for both reproductive performance and testosterone response to GnRH were repeatable when measured at two and four years of age. Other reproductive measurements (semen quality, scrotal circumference, pen-type serving capacity tests) were less reliable predictors of reproductive performance. Measurements of liveweight gains and parasite resistance indicated that bulls superior for these characteristics do not always have satisfactory reproductive performance. These studies suggest that the testosterone response to GnRH could be a useful test to ensure that bulls selected for productive traits have adequate reproductive potential.