Breeding Season Length Versus Calving Percentage in Beef Cattle Herds

Abstract The commercial beef cattle industry relies heavily on the use of natural service sires. Either due to the size of breeding herds or to safe-guard against injury during the breeding season, multiple-sire breeding pastures are utilized. Although each bull might be given an equal opportunity to produce offspring, evidence suggest that there is substantial variation in the number of calves sired by each bull in a breeding pasture. DNA-based paternity assignment enables correct assignment of calves to their respective sires in multi-sire pastures and presents an opportunity to investigate the degree to which this trait complex is under genetic control. Field data from a large commercial ranch were used to estimate genetic parameters for calf count (CC; n=623) and yearling scrotal circumference (SC; n=1962) using univariate and bivariate animal models. Average CC and SC were 12.1±11.1 calves and 35.4±2.30 cm, respectively. Average number breeding seasons per bull and bulls per contemporary group were 1.40 and 24.9, respectively. The model for CC included fixed effects of age during the breeding season (in years) and contemporary group (concatenation of breeding pasture and year). Random effects included additive genetic and permanent environmental effects, and a residual. The model for SC included fixed effects of age (in days) and contemporary group (concatenation of month and year of measurement). Random effects included an additive genetic effect and a residual. Univariate model heritability estimates for CC and SC were 0.237±0.156 and 0.456±0.072, respectively. Similarly, the bivariate model resulted in heritability estimates for CC and SC of 0.240±0.155 and 0.461±0.072, respectively. Repeatability estimates for CC from univariate and bivariate models were 0.517±0.054 and 0.518±0.053, respectively. The estimate of genetic correlation between CC and SC was 0.270±0.220. Parameter estimates suggest that both CC and SC would respond favorably to selection and that CC is moderately repeatable.

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Breeding season, length-weight relationship and condition factor of introduced fish, Tilapia zillii Gervais 1948 (Pisces: Cichlidae) in Lake Zwai, Ethiopia

SINET Ethiopian Journal of Science ◽

10.4314/sinet.v26i2.18207 ◽

2005 ◽

Vol 26 (2) ◽

Author(s):

Ababe Getahun ◽

Alemayehu Negassa

Keyword(s):

Breeding Season ◽

Condition Factor ◽

Season Length ◽

Introduced Fish ◽

Weight Relationship ◽

Tilapia Zillii

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How Many Baskets? Clutch Sizes That Maximize Annual Fecundity of Multiple-Brooded Birds

The Auk ◽

10.1093/auk/118.4.973 ◽

2001 ◽

Vol 118 (4) ◽

pp. 973-982 ◽

Cited By ~ 8

Author(s):

George L. Farnsworth ◽

Theodore R. Simons ◽

J. Brawn

Keyword(s):

Clutch Size ◽

Breeding Season ◽

Nest Predation ◽

Reproductive Effort ◽

Nest Survival ◽

Survival Rates ◽

Season Length ◽

Deterministic Models ◽

Cavity Nesting ◽

Theoretical Issues

Abstract We developed deterministic models on the basis of nest survival rates and renesting behavior capable of predicting annual fecundity in birds. The models calculate probabilities of fledging from one to four nests within a discrete breeding season. We used those models to address theoretical issues related to clutch size. In general, birds require at least one day to lay an egg, and many species delay incubation until their entire clutch is laid. Because it takes longer to complete a larger clutch, and fewer such clutches can fit into a limited breeding season, there exists a clutch size for which annual fecundity is maximized. We asked, for a given amount of reproductive effort (i.e. a set number of eggs), does the age-old maxim “don't put all your eggs in one basket” apply? If so, in how many “baskets” should a nesting bird place its eggs? The answer depends on both likelihood of nest predation and length of the breeding season. Those results are consistent with the observed increase in clutch size with latitude (shorter breeding season length) and larger clutch sizes characteristic of cavity-nesting species (with higher nest survival rates). The models also predict that the size of replacement clutches should decrease as the breeding season progresses, and that intraseasonal decline in clutch size should be more pronounced when the breeding season is short.

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Reproduction performance of beef cattle mated naturally following synchronization in the Central Bushveld bioregion of South Africa

South African Journal of Animal Science ◽

10.4314/sajas.v44i5.14 ◽

2015 ◽

Vol 44 (5) ◽

pp. 70-74

Author(s):

SM Grobler ◽

MM Scholtz ◽

JPC Greyling ◽

FWC Neser

Keyword(s):

South Africa ◽

Beef Cattle ◽

Breeding Season ◽

Recovery Period ◽

Beef Cows ◽

First Year ◽

Natural Mating ◽

The Difference ◽

Calving Season ◽

Main Component

The estimated calving percentage of beef cattle is 62% in the commercial sector of South Africa. Fertility is regarded as the main component influencing total herd efficiency in beef cattle. If the long calving seasons can be shortened and the calving percentage increased, more and heavier calves with a more uniform age can be weaned. Cows calving earlier in the season also have an extended “recovery period” and have the opportunity to calve in a better body condition during the next season, compared to cows calving late in the season. Cows that calve early also have a better chance of conceiving in the next breeding season and are generally seen as the more fertile animals. Research has been undertaken to evaluate the effect of oestrous synchronization followed by natural mating on the calving rate and calving distribution of multiparous beef cows. In this trial Bonsmara cows were mated naturally after synchronization over a period of four years (2009 - 2012) in an extensive production system on natural sour-mixed bushveld. The synchronized cows calved earlier during the 2009 calving season and cows in anoestrus started cycling again. The average days-to-calving after the start of the breeding season was 243 days for the synchronized cows and 267 for the non-synchronized cows. The calves born from the synchronized cows were therefore, on average, 24 days older than the calves born from the non-synchronized cows. From 2010 onwards the difference declined and it seems the biggest effect was obtained during the first year of synchronization.Keywords: Beef cattle, Marikana thorn veld, natural mating, oestrous synchronization

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Risk factors for foot and mouth disease outbreaks in grazing beef cattle herds

Preventive Veterinary Medicine ◽

10.1016/j.prevetmed.2015.03.011 ◽

2015 ◽

Vol 120 (2) ◽

pp. 236-240 ◽

Cited By ~ 10

Author(s):

E. Elnekave ◽

L. Zamir ◽

F. Hamd ◽

B. Even Tov ◽

E. Klement

Keyword(s):

Risk Factors ◽

Beef Cattle ◽

Disease Outbreaks ◽

Foot And Mouth Disease ◽

Mouth Disease ◽

Foot And Mouth ◽

Cattle Herds

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Corticosterone, testosterone and life-history strategies of birds

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2010.0673 ◽

2010 ◽

Vol 277 (1697) ◽

pp. 3203-3212 ◽

Cited By ~ 167

Author(s):

Michaela Hau ◽

Robert E. Ricklefs ◽

Martin Wikelski ◽

Kelly A. Lee ◽

Jeffrey D. Brawn

Keyword(s):

Life History ◽

Body Mass ◽

Breeding Season ◽

Life History Traits ◽

Survival Rates ◽

Life History Strategies ◽

Adult Survival ◽

Tropical Species ◽

Published Data ◽

Season Length

Steroid hormones have similar functions across vertebrates, but circulating concentrations can vary dramatically among species. We examined the hypothesis that variation in titres of corticosterone (Cort) and testosterone (T) is related to life-history traits of avian species. We predicted that Cort would reach higher levels under stress in species with higher annual adult survival rates since Cort is thought to promote physiological and behavioural responses that reduce risk to the individual. Conversely, we predicted that peak T during the breeding season would be higher in short-lived species with high mating effort as this hormone is known to promote male fecundity traits. We quantified circulating hormone concentrations and key life-history traits (annual adult survival rate, breeding season length, body mass) in males of free-living bird species during the breeding season at a temperate site (northern USA) and a tropical site (central Panama). We analysed our original data by themselves, and also combined with published data on passerine birds to enhance sample size. In both approaches, variation in baseline Cort (Cort0) among species was inversely related to breeding season length and body mass. Stress-induced corticosterone (MaxCort) also varied inversely with body mass and, as predicted, also varied positively with annual adult survival rates. Furthermore, species from drier and colder environments exhibited lower MaxCort than mesic and tropical species; T was lowest in species from tropical environments. These findings suggest that Cort0, MaxCort and T modulate key vertebrate life-history responses to the environment, with Cort0 supporting energetically demanding processes, MaxCort promoting survival and T being related to mating success.

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