John P Kent

University College Dublin | UCD · Research

Testosterone (T) concentrations in many species are sensitive to seasonal changes and to changes in social conditions. However, the effect of the natural or endogenous T increase in the juvenile on their social behaviour is not well understood. In this study, T and behaviour were measured from the pro-social juvenile to the adult stage in semi-fera...

The birth sex ratio of a commercial flock of Suffolk sheep, Ovis aries, were studied over six consecutive lambing seasons. In all, data from 1820 lambs were recorded and analysed. The overall birth sex ratio was 49.56% male lambs. Significantly more males (56.23%) were born to ewes with single lambs than to ewes with like-sex twins (47.73%). Signif...

The birth sex ratio of a commercial flock of Suffolk cross sheep, Ovis aries, was studied over nine consecutive lambing seasons. In all data from 2704 lambs were recorded and analysed. The overall (1985–1993) birth sex ratio was 49.96% male lambs. Ewes with single lambs produced significantly more males (53.04%) than ewes with triplets (45.54% male...

In general, avian species produce clutches of more than one egg. Differential investment in egg weight and hormone levels is possible and their effects on development and behaviour can be measured. Here we investigated changes in three hormones (testosterone, T; androstenedione, A4 and progesterone, P4) in the outer layer of yolks of infertile dome...

The relationship between the cow and calf develops over time after birth. The behavioural mechanisms underlying its development are important and comparisons with other species may increase our understanding. In nature the cow will separate herself from the herd to give birth and then the cow–calf relationship will develop with the ability to recog...

The present investigation was aimed at predicting a still (i.e., dead) vs. live embryo within a hatching goose egg by measuring the eggshell cooling rate. For this, we daily measured the temperature (T) values on the shell surface of goose eggs after they were removed from the incubator and during further natural cooling. T was recorded every 0.5 h...

In waterfowl farms used for producing meat and eggs, a problem of discerning double-yolked (DY) and single-yolked (SY) eggs is rather actual. While in some parts of the world DY eggs are popular as a food product, DY eggs are undesired for hatcheries due to their lower fertility and poorer hatchability. After examining the morphological parameters...

We proposed here a non-destructive technology for pre-sorting eggs into subclasses characterized by a specifical acceptable shelf life and quality requirements. Egg characteristics were identified suiting a predictive model for controlling storage periods. Accordingly, the relationships of egg parameters were assessed, with weight loss (ΔW) during...

A bird's egg has a variety of distinct physical characteristics that assure its functionality as a naturally engineered ‘packaging’ for the growing embryo. It also contains essential nutrients for human food. Egg density (D) is one such crucial physical parameter frequently involved in studies pertaining to its interrelationship with the quality of...

The present study was aimed to seek algorithms for prior identification of goose eggs unsuitable for incubation that, otherwise, turn into to hatching waste. These included infertile eggs and those in which the embryo did not survive by the hatch time. The algorithm development was based on egg parameter measurements taken before and during incubat...

Enhancing goose production for human consumption requires evaluating the quality of goose eggs based on their physical characteristics. Grounded on the theoretical and experimental studies, we developed two calculation formulae that enabled the computation of Egg Quality Index (EQI) as an alternative to the widely used Haugh unit (HU) score in asse...

Density of egg interior (Di) can be considered as universal index of the quality characteristics of the whole egg. Here, we implemented a theoretical and experimental approach to developing a method for non-invasive estimation of Di. The derived equation showed its dependence on the egg density (D) and the content of the shell in the egg, the latte...

Double-yolked (DY) eggs have been mostly described in domestic precocial species, and are rarely found in nature. It is estimated that 1–3% of domestic hen and duck eggs are DY. They occur when two yolks are encapsulated in a single shell and therefore differ from single yolked (SY) eggs in their external and internal characteristics. In previous d...

Spurs are a testosterone-dependent secondary sexual characteristic of male chickens ( Gallus gallus domesticus ) and are used as ‘weapons’ in intra-sexual fighting. While predominantly a male feature, they are also found in a small number of females. Here we show that faecal testosterone metabolites of adult hens (i.e. females) with large spurs are...

Spurs are a testosterone-dependent secondary sexual characteristic of male chickens ( Gallus gallus domesticus ) and are used as ‘weapons’ in intra-sexual fighting. While predominantly a male feature, they are also found in a small number of females. Here we show that faecal testosterone metabolites of adult hens (i.e. females) with large spurs are...

Clarity in the terminology used in animal welfare regulation and science is important. The use of the terms ‘cervical dislocation’ and ‘stunning’ in regulations regarding on-farm poultry slaughter and the role of the scientific evidence in developing these regulations are examined. It is concluded that the use of limited scientific evidence can unw...

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Background and objective: While avian egg shape is species specific there is evidence for intraspecific variation and this variation may be especially great in domestic ducks where selection for egg production was not as intense as in the domestic fowl. Egg shape (visually assessed) and shape index (calculated from egg dimensions) were compared in...

Multiple-yolked avian eggs, and especially triple-yolked (TY) eggs, are rare. Over two years, 48,224 duck eggs (Anas platyrhynchos domesticus) were individually candled and seven (0.0145%) TY eggs were identified in a commercial breeding and incubation environment. When compared with double-yolked eggs (Salamon and Kent, 2016) their mean weight, le...

Egg turning is a vital part of the incubation process in many bird species. However, the quality and quantity of turning can differ between species. Commercial incubators with domestic fowl automatically move the eggs that are set pointed end down, 45° either side from the vertical every hour. However, goose eggs are not set pointed end down vertic...

Herein we examined the effects of yolk size and ovulation order on the fertilisation of yolks within double-yolked (DY) duck eggs. Single-yolked (SY) duck eggs had high fertility (89.98%), whereas in DY duck eggs fertility was low (51.9% yolks). The yolks closer to the airspace (Yolk 1) in DY eggs had higher fertility (68.82% vs 34.98% for Yolk 2;...

Double-yolked (DY) eggs have provided new insights into the process that determine (a) ovulation, (b) egg composition (c) fertility (d) incubation and the value of the comparative approach in biology. Small DY eggs are produced at the onset of laying by young birds, while larger DY eggs occur at the end of lay. At the onset of lay one cannot disti...

Double-yolked (DY) and single-yolked (SY) duck eggs (n = 1318 for both) were candled and weighed on Days (d) 2, 8, 12, 15, 19, 22 and 25 of incubation and yolk/embryo position was recorded on d2, d8 and at post-mortem. From d8 only eggs with live fertile yolk(s) remained in the incubator. On d2, 99.39% of yolks in DY eggs were in the adjacent posit...

Chicks (Gallus gallus domesticus) learn to peck soon after hatching and then peck in rapid bursts or bouts with intervals of non-pecking activity. The food sources may be static such as seeds and chick crumb, or mobile such as a mealworm. Here, changes with age in pecking toward chick crumb and a mealworm were measured. Chicks were reared in pairs...

While the avian egg is formed in the oviduct, it acquires its shell membranes and shape in the isthmus and the calcified shell in the shell gland/uterus. However, in domestic species not all eggs are laid pointed end first, which led to the suggestion that egg rotation can occur in the oviduct prior to laying producing the blunt end first. However,...

Maternal investment in egg weight was examined over the laying season in nine flocks of domestic geese of various ages. Eggs laid at night were collected on two consecutive days each week over the 19 week study period. Rate of lay increased rapidly until week 4, when it reached a plateau that was maintained for ten weeks and then decreased rapidly...

Egg weight increased with age (one to four years) in domestic geese and was followed by a senescent decline. However a more striking finding in adult geese was a within season decline in egg weight over the first eight weeks of lay, until baseline weight levels were achieved and were then maintained until the end of the laying season. The egg weigh...

The weight and contents (yolk, albumen, shell) of double yolked (DY) and single yolked (SY) eggs of domestic ducks were measured and compared. The yolks in DY eggs did not differ in weight (p=0.144), although each yolk in DY eggs was significantly lighter than the yolk of a SY egg (p<0.001). DY albumen weight was below that expected of a SY egg of...

The weight, dimensions (length, width) and contents (yolk, albumen, shell) of double yolked (DY) and single yolked (SY) duck eggs were measured and compared. Yolk position was recorded in DY eggs and the yolk closer to the airspace was termed Yolk 1. DY eggs were 21.5 % heavier, 11.7 % longer and 4 % wider (all p<0.001). On average, DY eggs had mor...

The external dimensions, weight and contents (yolk, albumen, shell) of Double Yolked (DY) and Single Yolked (SY) eggs of the duck (Anas platyrhynchos domesticus) were measured and compared. The yolks in DY eggs did not differ in weight (p = 0.144), although each double yolk was significantly lighter than the yolk of a SY egg (p<0.001). DY albumen w...

Birth sex ratios are studied by those concerned with their ultimate causation (evolution), and the proximal mechanisms by which they manifest themselves. Behavioural scientists are uniquely qualified to study these phenomena both at the observational and theoretical levels. The birth sex ratios of a flock of sheep were studied over 10 consecutive l...

Double yolked eggs occur rarely in nature. The external appearance of double yolked eggs differ from single yolked eggs tending to be larger, longer and heavier (Curtis, 1914; see Romanoff and Romanoff, 1949). Johnston and Gous (2007) notes that double yolked eggs are common at the onset of laying in laying hens (see Christmas and Harms, 1982) and...

Twin embryos occur rarely in birds eggs, but little is known about the causes or consequences of this phenomenon. There are a few reported cases in passerines and in waterfowl. Here embryo development in double yolked eggs from Aylesbury ducks are studied. These eggs are larger and egg content proportions differ to normal sized control eggs. Demogr...

This study examines the socioeconomic and familial background of Irish Catholic priests born between 1867 and 1911. Previous research has hypothesized that lack of marriage opportunities may influence adoption of celibacy as part of a religious institution. The present study traced data from Irish seminary registries for 46 Catholic priests born in...

Animal welfare assessment at group level is a scientific discipline that is rapidly developing. The interest in welfare assessment systems is based on an ethical concern for the welfare of farm animals. The scientific community plays an important role in delivering an appropriate repeatable, valid and feasible framework for these assessments. Consi...

Egg production of eight flocks of domestic geese, housed separately, though sharing a common grazing area, show a synchronized laying pattern. Housed egg production of each flock was recorded over 83 consecutive days of the laying season. Using time-series statistical procedures it was found that the geese were laying in a peak-trough/saw-tooth pat...

The proportion of people who never married and the age at first marriage increased in rural Ireland after the famine (1845–1847). In 1851, 11% of the population were never married at 45–54 years and this percentage increased steadily over time to 34% for men and 25% for women in 1936. The period from 1851 to 1911 was marked by economic progress, an...

The ground-roosting behaviour of a semi-feral population of domestic hens with broods of chicks was measured in The Gambia, West Africa. Although neither day length nor time of sunset changed significantly over the duration of the study (January–March 1995), mean daily light intensity showed a significant increase. This resulted in an increasingly...

The predominant frequency, rate of clucking and intensity of the maternal cluck vocalization of the broody hen (Gallus gallus) are described. The frequency, rate of clucking, and level of intensity of the cluck vocalizations were altered independently of each other. Three-day-old chicks were given a simultaneous choice test between the normal and a...

The broody hen behaves in an aggressive way towards other hens. Pairs of either two broody hens, or two non-broody hens, or one broody and one non-broody hen, were observed in a small enclosure. Pecking of pen mates was found in pairs of broody hens while no pecking was found in pairs of non-broody hens. In pairs of one broody and one non-broody he...

The maternal cluck vocalizations of the bantam hen were examined using a sonagraph. 3 consecutive clucks from each of 6 hens were examined. Eight physical parameters from each vocalization were measured directly from the spectrograms, namely duration of the cluck, maximum frequency at the beginning of the cluck, maximum absolute frequency of the cl...

In a series of 6 experimental studies, the means by which a chick recognises its mother, and the reversibility of filial attachments were examined using bantam hens and their chicks. In a simultaneous discrimination test it was determined that the chick could discriminate between own and alien hens by means of the hens' cluck vocalizations, on the...