Breeding Interval Research Articles

Reconstruction of paternal genotypes over multiple breeding seasons reveals male green turtles do not breed annually

For species of conservation concern, knowledge of key life-history and demographic components, such as the number and sex ratio of breeding adults, is essential for accurate assessments of population viability. Species with temperature-dependent sex determination can produce heavily biased primary sex ratios, and there is concern that adult sex ratios may be similarly skewed or will become so as a result of climate warming. Prediction and mitigation of such impacts are difficult when life-history information is lacking. In marine turtles, owing to the difficultly in observing males at sea, the breeding interval of males is unknown. It has been suggested that male breeding periodicity may be shorter than that of females, which could help to compensate for generally female-biased sex ratios. Here we outline how the use of molecular-based paternity analysis has allowed us, for the first time, to assess the breeding interval of male marine turtles across multiple breeding seasons. In our study rookery of green turtles (Chelonia mydas), 97% of males were assigned offspring in only one breeding season within the 3-year study period, strongly suggesting that male breeding intervals are frequently longer than 1year at this site. Our results also reveal a sex ratio of breeding adults of at least 1.3 males to each female. This study illustrates the utility of molecular-based parentage inference using reconstruction of parental genotypes as a method for monitoring the number and sex ratio of breeders in species where direct observations or capture are difficult.

Sea turtle population estimates incorporating uncertainty: a new approach applied to western North Atlantic loggerheads Caretta caretta

Loggerhead sea turtles Caretta caretta have been listed as threatened under the US Endangered Species Act since 1978, and a change in their listing status to endangered was recently under consideration. Estimates of adult population size are needed to evaluate population status, but include a number of uncertainties. A point estimate of loggerhead population size based on a nest count fails to convey the range of our uncertainty in the estimated number of indi- viduals in a population. We developed distributions of adult female loggerhead subpopulation sizes for 5 subpopulations of the western North Atlantic, and for the western North Atlantic popu- lation as a whole. Distributions were derived by re-sampling from available nest counts (2001�2010) and data on breeding interval, survival and clutch frequency, each affecting the extrapolation of nest numbers to adult females. Our best estimate for the western North Atlantic adult female loggerhead population was 38 334 (SD = 2287) adult females. Confidence limits on estimates for the individual subpopulations ranged from a high of 45 058 adult females for Penin- sular Florida to a low of 258 adult females in the Dry Tortugas. To reduce uncertainty in population estimates, research needs to focus on quantifying breeding interval and clutch frequency, espe- cially in the less-studied subpopulations.

Loss of Magel2, a Candidate Gene for Features of Prader-Willi Syndrome, Impairs Reproductive Function in Mice

Background MAGEL2 is one of several genes typically inactivated in the developmental obesity disorder Prader-Willi syndrome (PWS). The physiological consequences of loss of MAGEL2, but without the concurrent loss of other PWS genes, are not well understood. Gene-targeted mutation of Magel2 in mice disrupts circadian rhythm and metabolism causing reduced total activity, reduced weight gain before weaning, and increased adiposity after weaning.Principal FindingsWe now show that loss of Magel2 in mice causes reduced fertility in both males and females through extended breeding intervals and early reproductive decline and termination. Female Magel2-null mice display extended and irregular estrous cycles, while males show decreased testosterone levels, and reduced olfactory preference for female odors.ConclusionsOur results suggest that loss of MAGEL2 contributes to the reproductive deficits seen in people with PWS, and further highlights the role of normal circadian rhythm in the maintenance of fertility.

Reproductive Performance of Beef Cows Fed Whole Soybeans Before the Breeding Interval

Effects of feeding soybeans before breeding were determined using primiparous (PC) and multiparous (MC) Angus (PC = 17; MC = 36) and Polled Hereford (PC = 12, MC = 11) cows randomly assigned to control (no supplementation) or cracked whole soybean (2.12kg DM/cow daily) treatments from February 11 to April 11. The breeding interval began April 14, using AI (d 1 to 44) and natural service (d 45 to 71). Calf ADG during the prebreeding period and during the interval from d 1 to weaning at d 210 was unaffected by treatment (P > 0.10). Calf breed affected (P < 0.01) calf prebreeding ADG, 210-d ADG, and 205-d weaning BW, which, respectively, were 1.18, 0.92, and 230.6kg for Angus, and 1.01, 0.83, and 211.8kg for Polled Hereford. Pregnancy rates were unaffected (P > 0.10) by treatment, cow breed, or parity. On d 60, serum triglyceride was greater for cows fed soybeans than for control cows (P < 0.01; 31.2 vs. 27.0 mg/dL), and serum cholesterol was affected by a treatment × parity interaction (P < 0.05), with respective values for control PC and MC and soybean treatment PC and MC of 134.6, 176.2, 195.8, and 201.5 mg/dL. Serum leptin levels on d 60 for these respective treatments were 5.4, 9.0, 8.4, and 8.6 ng/mL, with the lowest (P < 0.05) concentration in control PC cows. Feeding soybeans to PC cows resulted in increased serum leptin (P < 0.05), and PC cows fed soybeans had similar serum triglyceride, cholesterol, and leptin levels compared with MC for these variables.

Effects of 12 hour calf withdrawal on conception rate and calf performance of Bos indicus cattle under extensive conditions

Fifty-two multiparous Brahman type cows with reproductive tract scoring (RTS) >/=4 at 45 days post-partum were randomly assigned to two groups of 26 cows each separated into an ad libitum suckling group (C) and treatment group (T). Calves in the T group were separated for 12 h during the night from 45 days post-partum to the onset of the breeding season. Body condition score (BCS) and body weight (BW) were recorded 45 days post-partum, at the start of the breeding season, and at pregnancy diagnosis. Calves were weighed at calving and weaning. Weaning weights were corrected to 205 days. BW and BCS at the onset of the breeding season were similar (p > 0.05) between the experimental groups. Calving to breeding intervals were 93 +/- 18 d and 99 +/- 22 d for T and C groups, respectively. Calving to conception intervals differed significantly between the groups (111 +/- 10 d for T and 133 +/- 19 d for C) and a similar result was obtained for the breeding to conception intervals (18 +/- 15 d for T and 31 +/- 19 d for C). Conception rates were 80% for the T group and 59% for the C group, which correlated better with BW than BCS at the onset of the breeding season. Weaning weights differed (p < 0.05) between C and T groups. From 45 days post-partum to the onset of the breeding season, cows in the T group experienced a positive energy balance (3%) while those in the C group had a negative energy balance (-0.1%). It was concluded that 12 h calf separation at night increases the conception rates and improves the calf weaning weights of Bos indicus beef cattle under extensive production systems in sub-tropical conditions.

Uncertain breeding: a short history of reproduction in monotremes.

Although much is known about the biology of monotremes, many important aspects of their reproduction remain unclear. Studies over the last century have provided valuable information on various aspects of monotreme reproduction including the structure and function of their reproductive system, breeding behaviour, sex determination and seasonality. All three living genera of monotremes have been successfully maintained in captivity, often for long periods, yet breeding has been rare and unpredictable. When breeding has occurred, however, significant gains in knowledge have ensued; for example a more accurate estimate of the gestation period of the platypus and the incubation period for the Tachyglossus egg. One of the great challenges for zoos has been to understand why breeding of monotremes is difficult to achieve. Analysis of breeding successes of platypuses and short-beaked echidnas provides some insights. The evidence suggests that although annual breeding seasons are regionally predictable, individual adult females breed unpredictably, with some showing breeding intervals of many years. The reason for this variation in individual breeding intervals may be resource-dependant, influenced by social factors or may even be genetically induced. Better knowledge of factors that influence breeding intervals may improve the success of monotreme captive breeding programmes. More certainty in captive breeding is also an important issue for enterprises wishing to trade in Australian wildlife since current legislation limits export of Australian fauna for display to at least second-generation captive-bred individuals. Given their unique evolutionary position, knowledge of reproduction in monotremes needs to be gained in advance of any future population declines so that appropriate strategies can be developed to ensure their survival.

Reproductive Performance of Holstein Cows Receiving Somatotropin

Some dairy producers resist using bovine somatotropin (bST) beginning at 9 wk postpartum because of the concern that fertility is compromised. We conducted a trial with a total of 205 Holstein cows, 100 multiparous and 105 primiparous, to evaluate reproductive performance in two high producing herds in Arizona and southern California. Rolling herd averages for both herds for milk production exceeded 10,700 kg/yr. Data were collected for cows calving December 1996 through August 1997. The voluntary waiting period was 60 d postcalving, with cows randomly assigned to receive bST or no treatment (controls). In the 180-d interval after calving, 65.4% (68/104) of the control cows were diagnosed pregnant. With bST-treated cows, 48.5% (49/101) were pregnant in that same interval. A chi-square value from a linear model indicated that pregnancy outcome differed significantly between treatment groups. With a similar method of analysis, first-service conception rate was not significantly different between treatment groups. An extended voluntary wait and breeding interval is recommended for cows receiving bST, similar to suggestions from other published reports.

Molt, Maturation of Plumage and Ageing in the Wandering Albatross

We compare the pattern and rate of molt and plumage maturation in Wan- dering Albatrosses (Diomedea exulans chionoptera) using prebreeding and breeding birds from South Georgia (S. Atlantic Ocean) and Crozet Islands (S. Indian Ocean). Imma- tures from both sites have a molt cycle which basically alternates molt of outer primaries in one year and inner primaries in the next year. This is similar to, but in its details more complex and flexible than, the molt of the smaller, sympatric Black-browed and Gray- headed Albatrosses (D. melanophris and D. chrysostoma). It differs from the wrap-around molt characteristic of Laysan and Black-footed Albatrosses (0. immmutahilis and D. ni- gripes). Juvenile Wandering Albatrosses have most new primaries when 5-year-olds but even at this age some birds have retained primary 1 since they fledged. Males, but not females, from South Georgia replace more primaries than do Crozet birds. Adults breed- ing for the first time molt fewer primaries than birds breeding 7-l 1 months after a failed breeding attempt; these adults molt on average 6 primaries, similar to successful or failed Black-browed Albatrosses. Successful Wandering Albatrosses, in the 12 months before breeding again, only molt 7-8 primaries on average, in contrast to the 11 primaries molted by biennial Gray-headed Albatrosses in their 16 month breeding interval. The duration of the interval between successive breeding attempts is probably the main constraint on the amount of primary molt that can be accomplished. Failed, but not successful, Wan- dering Albatrosses breeding at Crozet molt more primaries than similar birds at South Georgia. At both sites, the plumage of birds of both sexes gets whiter until about 20 years old. However, South Georgia males are already whiter than Crozet birds at 5 years old (presumably reflecting the faster molt rate of South Georgia birds) and they maintain this difference for the next decade. In contrast, females from both sites mature at similar molt rates until age 10 years (median age of first breeding) when South Georgia birds become and stay whiter than Crozet birds. Plumage maturation rate is much slower in birds from Macquarie Island, but these may not belong to the same subspecies. Conven- tional (Gibson) plumage scores do not provide a reliable means of estimating age of Wan- dering Albatrosses, except in very general (53-5 year) categories. The pattern and ex- tent of molt, however, can age most immature birds of D. e. chionoptera to within one year; we provide a key for doing this.

Field reproductive potential of tropical high mountain Hyla labialis females: direct and indirect evidence from mark-recapture data

AbstractData from 203 recaptured Hyla labialis females, representing 37.9% of all females captured, individually marked and released during a five-year field study in a tropical highland valley in the eastern chain of the Colombian Andes were used to examine directly (recording a sequence of spawning events) and indirectly (finding a large change in body condition index between successive encounters) the reproductive activity of individual females in relation to the reproductive pattern of the entire population, which had two long breeding seasons per year. Equivalent results were obtained from both sources of evidence for estimating the length of individual breeding intervals. No female was encountered breeding twice in the same season. Only a small percentage of the adult females was found at the breeding ponds in successive seasons. The majority of the females apparently spawned once per year or at even longer intervals. The length of individual breeding intervals was unrelated to body size, body mass and body condition index of the females. The variable lengths of breeding intervals of individual females seem to be a combined consequence of physiological recovery capacity after an oviposition and several environmental factors.

Reproductive Success of Northern Spotted Owl Activity Centers in the Northwestern Washington Cascades

Reproductive Success of Northern Spotted Owl Activity Centers in the Northwestern Washington Cascades

The adaptive significance of a lunar or semi-lunar reproductive cycle in marine animals

Many marine invertebrates and fishes have a lunar or semi-lunar reproductive cycle. There are several possible explanations for the advantages of reproductive rhythmicity. Such rhythmicity may (1) increase the rate of mating; (2) increase the rate of fertilization; (3) help to retain free-living larvae in nursery sites; (4) help to spread free-living larvae over some adult habitats; (5) decrease predator pressure on free-living larvae; or (6) increase reproductive success by the direct influence of lunar cyclic environmental effects such as moonlight. In this study, the adaptive significance of reproductive rhythmicity in increasing the reproductive rate, is examined by analyzing the model which has three major controlling parameters, i.e. population density, sex ratio, and the duration of breeding interval. The objective function, that is adaptiveness, of per capita oviposition number per unit time is calculated under the non-cyclic or the cyclic reproductions. It appears, from the analysis of the model, that the cyclic type is accompanied by a higher rate of oviposition that the non-cyclic one under conditions of high sex ratio (female > male) and/or of low population size. In particular, under conditions of low population size, the cyclic reproduction decreases the lower limit of population growth and, thereby, reduces the probability of extinction of the population.

Measuring Efficiency and Accuracy of Detection of Estrus

The ability of management to detect estrus efficiently and accurately in cows and heifers profoundly influences reproductive performance and profitability of dairy herds. Routine estimates of efficiency and accuracy are important to monitor reproduction in a herd and to evaluate management in problem breeding herds. Detection efficiency is usually expressed as the percentage of possible estruses that were observed over a given time period. Eight methods are presented that approximate efficiency using estrus and insemination dates. Efficiency can be estimated from herd summary information using the equation recommended by the Dairy Reproduction Core Parameter Committee or using equations that calculate the breeding interval. Milk progesterone concentrations measured by on-farm tests can be used to approximate efficiency. Seven of the nine Dairy Record Processing Centers calculate an efficiency estimate. Accuracy of detection of estrus is the percentage of estruses observed that are true estruses. Inaccurate detection of estrus results in breeding of cows not in estrus, thus lowering conception rate. Detection accuracy should be evaluated for herds experiencing low conception rates. Comparison of interestrual intervals, results of uterine and ovarian palpation, and progesterone concentrations of cows perceived to be in estrus can be used to estimate the accuracy of detection of estrus.

Dynamics of a small, hunted brown bear Ursus arctos population in Southwestern Alberta, Canada

We studied population dynamics of brown bears Ursus arctos in the Kananaskis Park and Bow Crow Forest of southwestern Alberta, Canada to evaluate effects of hunting. Twenty-four bears were captured and 20 were radio-monitored from 1980 to 1984. Estimated density was 1.6 bears/100 km 2, for a population size of 38 bears. Mean annual sex and age composition was 30% adult males, 22% adult females, 22% subadult males, 11% subadult females, and 15% cubs. Mean litter size of new cubs was 1.40 and mean birth or breeding interval was 3.00 years. The reproductive rate was estimated at 0.46 cubs/adult female/year. Adjusted annual survival rates were 0.70 for adult males, 0.93 for adult females, 0.89 for subadult males, 0.89 to 0.93 for subadult females, and 0.78 for cubs. Combined, these rates yield population growth rates of r s = −0.01 to r s = + 0.01. Increased hunting mortality of older adult males coincided with an influx of younger immigrant males, which apparently contributed to low reproductive rate and population decline.

Effect of initial breeding weight and management system using a high-producing sow genotype on resulting reproductive performance over three parities.

A study was conducted with sows of a high-producing genotype to evaluate their reproductive performance using three breeding weights over a three-parity period in two management systems. A total of 114 F1 gilts (Landrace x Yorkshire) were used in a split-plot, randomized, complete block experiment conducted as a 3 x 2 factorial arrangement of treatments in two replicates. Three gilt breeding weights of 120, 135, and 150 kg were achieved by feeding 1.8, 2.3, or 3.2 kg/d of a .73% lysine corn-soybean meal (C-SBM) diet, respectively, from 5 to 8 mo of age. Two locations, each with different management systems, were considered the main plot and consisted of 1) outside, concrete-floored gestation lots and indoor farrowing pens or 2) indoor gestation pens and farrowing crates. All sows were fed 1.8 (Parity 1) or 2.1 (Parity 2 and 3) kg/d of a .73% lysine C-SBM diet during the breeding and gestation periods, whereas a .82% lysine C-SBM diet with 5% added fat was available ad libitum during lactation. All sows lost weight during the first lactation; larger weight losses occurred as breeding weight increased (P < .01). During the second and third lactations the 135- and 150-kg sow breeding groups had less lactation weight change, whereas the 120-kg group lost more weight, resulting in a breeding weight x parity interaction (P < .01). The 120-kg breeding weight group consumed less feed (P < .05) for the three lactation periods than did the heavier weight groups. Initial breeding weight had no effect on number of pigs born (total, live) or pig and litter weights at birth. Pig mortality increased with increasing breeding weight (P < .01) and parity (P < .05), a response that was exacerbated when sows farrowed in pens vs crates. Postweaning breeding intervals and sow removal from the experiment were not significantly affected by initial breeding weight, but a numerically higher percentage of sows in the 120-kg group were anestrous or failed to conceive than the percentage of such sows in the heavier weight groups. These data suggest that an initial breeding weight of approximately 135 kg at 8 mo of age may be best when sows farrow in crates, whereas when sows farrow in pens a lower breeding weight may be more desirable.

An Implicit Cost of Nest Re-use in the Rufous Turtle Dove Streptopelia orientalis

1) The Rufous Turtle Dove Streptopelia orientalis was studied in Kyoto, Japan and found to often re-use old nests for breeding. The hypothesis that the same breeding outcome (success or failure due to different causes) tended to occur at the same nest was examined with reference to the interval between two successive breedings.2) Seasonal tendencies in breeding outcomes were not significantly different between new and old-reused nests. Other failures were most frequent in July to October, both at new and old-re-used nests.3) Other failures occurred more frequently at the nests in which the preceding outcomes were also other failures within a certain breeding interval, but there was no such relationship for successful breedings. The tendency was diminished when all breedings were combined with no consideration of breeding interval.4) The results obtained here suggested that nest predators tended to revisit previously preyed-upon nests within a certain interval. It is suggested that, as the risk of nest predation in using old nests could not be assessed by the present status of the nests, re-use of old nests involves an implicit cost of nest predation.

Response of Dairy Cows to High Doses of a Sustained-Release Bovine Somatotropin Administered During Two Lactations. 2. Health and Reproduction

Eighty-two lactating Holstein cows in their first, second, or third lactation received either one, three, or five concurrent i.m. injections of a unit dose (.6g) of zinc methionyl bST (sometribove) or five doses of the vehicle. Injections were given at 14-d intervals from 60±3 d postpartum until the end of lactation or necropsy. Thirty-eight animals were continued on treatment for a 2nd yr Sometribove did not affect the incidence of ketosis, milk fever, tetany, or pneumonia. Digestive disorders, primarily cows going off feed, were increased by bST during yr 1 only. The incidence of lameness was increased by bST in some time frames because of an increase in the 3.0-g bST group. Lameness was not associated with treatment-specific histopathologic changes or with abnormalities in cartilage or bone. Reproductive health generally was unaffected by treatment, but delayed conception and increased incidence of abortion were noted, Incidence of cystic ovaries was unaffected by bST. Pregnancy rates were decreased during the 100-d breeding interval of yr 1 but not during the 215-d interval of yr 2. The incidence of clinical mastitis was increased by bST, primarily at the 3.0-g dose. During the 2-yr study, 0, 3, 3, and 2 cows died or became moribund on 0, .6, 1.8, and 3.0g of bST, respectively. Health issues identified for further evaluation included lameness and clinical mastitis for the 3.0-g group and early removal from the herd and decreased reproductive performance for all bST groups. Bovine somatotropin caused no treatment-specific toxic effects in dairy cows even at 3.0g every 14 d.

Simulated effects of reproductive performance on life-cycle efficiency of lamb and wool production at three lambing intervals

A deterministic computer model of a purebreeding sheep production system was used to simulate effects on life-cycle efficiency from genetic changes in lambing rate (LB), fertility (FERT), precocity of fertility (PREC), and estrus season length (ES) under annual (Y), 4-mo (A), and 73-d (S) breeding intervals. Ewes and lambs of a 1,000-ewe flock were fed to requirement through five yr, beginning with ewe lambs at the optimal breeding season and accumulating feed input (TDN) and market lamb equivalent weight of output (EBW), including cull ewes and wool. For annual lambing, improvement in cost (TDN/EBW equivalence) per 10% increase in genetic potential was -9.8, -8.2, -1.3, and -.8% for LB, FERT, PREC, and ES, respectively. For the A and S lambing intervals, corresponding gains in TDN efficiency were -19 for FERT and -9% for LB when ES was 72 d, but only -6 and -5% when ES was 192 d. Increasing PREC by 10% improved cost -3% under accelerated systems when ES was 72 d, but less than -1% when ES was 192 d. Cost reduction from 10% longer ES under A and S breeding intervals was greater when other reproductive performance was low (-11 and -17%) rather than high (-2 and -3%). Reduction in costs for A and S vs Y lambing intervals was greatest with long ES and was greater with low (-43 and -53%) than with high reproductive performance (-20 and -24%). When ES was 72 d, A and S intervals would reduce costs for high (-9 and -11%) but increase costs for low reproductive traits. Corresponding increases in CP/TDN required in diet would reduce gains in TDN/EBW only slightly. These results should aid in development of optimum selection criteria for stocks used for pure or rotation crossbreeding or as maternal parents of terminal crosses.

Selection for an optimal monovoltine life cycle in an unpredictable environment. Studies on the beetleCatops nigricans Spence (Col., Catopidae).

Catops nigricans reproduces in the autumn. Pre-imaginal development is temperature-dependent and takes place during the winter, followed by aestivation in the early adult stage. This summer diapause is obligatory and temperature independent. It synchronizes the monovoltine life cycle with the annual cycle. In three populations collected near Kiel (54°22' N, 10°6' E), Köln (50°54' N, 7°6' E), and Paris (49°25' N, 2°20' E), pre-imaginal development slowed and the duration of summer diapause decreased with increasing latitude. Synchronization of the critical breeding interval with the appropriate environmental conditions was achieved through temperature- and photoperiod-dependent sensitivity of ovipositing adults, through different thermal thresholds in eggs, larvae, and pupae, and through sensitivity to photoperiod in third-instars larvae.C. nigricans copes with the unpredictability of climatic conditions in different ways. The local populations have evolved a mean diapause length which probably adjusts the life cycle in most years to the optimal date for reproduction. The mean diapause length was 77 days for Kiel, 98 days for Köln and 138 days for Paris at 10°C, short-day (=SD).C. nigricans also spreads the risk by varying diapause length. Amongthe progeny of single females the range of diapause duration covered about 70% of the total range of the whole population. The oviposition rate of females confined to subterranean life was the same as females confined to subterranean life was the same as in those living under the influence of a varying photoperiod.C. nigricans should therefore be able to live both in the litter layer of forests and also in the nests and galleries of small mammals.

Mating and its effect on acoustic signalling behaviour in a primitive orthopteran, Cyphoderris strepitans (Haglidae): the cost of feeding females

Males of the primitive orthopteran, Cyphoderris strepitans, provide their mates with two types of nuptial food gift during mating: 1) females feed while coupled on the fleshy metathoracic wings of the male and the resultant flow of haemolymph and 2) the spermatophore transferred by the male includes a gelatinous spermatophylax which the female eats after mating. During the peak breeding interval, virgin males secure significantly more matings than their numbers relative to non-virgin males would predict. We tested the hypothesis that non-virgin males, having lost a substantial portion of available energy through previous investment in females, call significantly less than virgin males. Reduced calling should result in the attraction of fewer females and/or a greater risk of intrusion from competing males and consequently, a lowered mating success. Calling activity of male C. strepitans of varying mating status was monitored with a sound activated relay apparatus for two consecutive nights following their capture. Males were of three experimental groups, virgin, freshly wounded males (mated on the same night of capture), and old-wound males (mated at least one night prior to capture). Our cata showed a significant short-term reduction in signalling activity as a consequence of mating. Whereas there was no difference in the time spent calling by virgins on the first and second nights following capture, freshly wounded and oldwound males called significantly less on the first night than on the second. Furthermore, the proportion of males calling on both nights was significantly greater for the virgin and old-wound groups than for freshly wounded males. When the duration over which males called on the first night was compared with that of the second, virgin males showed no difference whereas old-wound males called for significantly shorter intervals on the first night. These results indicate that the cost of a large nutrient investment in females lowers the energy level in males below the threshold required for a prolonged signalling period. After a refractory interval during which males feed and replenish their energy reserves, calling levels equivalent to those which occur prior to mating are regained. Active female choice may also contribute to the reduced mating success of non-virgins, but this possibility remains untested.

Attitudes, management practices, and herd performance — a study of ontario dairy farm managers. I. Descriptive aspects

The purpose of this study was to investigate farm managers' socio-psychological characteristics concomitantly with farm performance and management policies applied on a random sample of southwestern Ontario dairy farms. This paper presents a description of these dairy farms with respect to the managers' socio-psychological characteristics, management practices, and selected farm performance indicators. A questionnaire was used to gather data necessary to describe the socio-psychological characteristics and management policies of the study farms, and herd performance variables were derived from an ongoing observational study which utilized the same sample of farms. Descriptive statistics are presented for 8 socio-demographic variables, 14 psychological variables, 11 management practices variables, and 8 farm performance variables including the level of various reproductive problems and milk production. Respondents had low scores in the application of 3 management practices; heat detection, calving to first breeding interval for cows, and record keeping. The results of analysis on the different groups of variables were in agreement with findings of other studies; hence, indicating that the sample of dairymen and dairy farms was not atypical.