Journal Articles

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Start date: 2020Subject: search.filters.subject.survival

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    Reasons for admission and post-release survival of UK rehabilitated herring gulls (Larus argentatus) from 1999 to 2024
    (Cambridge University Press, 2025-10-22) Thompson R; Chilvers BL; Stenning MJ
    Globally, millions of animals transition through wildlife rehabilitation facilities annually. Data recorded at these facilities can be used to quantitatively assess factors which result in the animals’ admittance, treatment, release, and survival, and how impacts such as high pathogen avian influenza (HPAI) has altered these parameters. Twenty-five years of records of herring gull (Larus argentatus) admittances into RSPCA Mallydams Wood Wildlife Rehabilitation Centre, Hastings, UK (between 1999 and 2024) were reviewed to determine admission factors and their impacts on the number of days in care and the likelihood of release. Additionally, for the years 1999 to 2010, data were collected on days of post-release survival and distances from the centre travelled from ringed and released birds. During that 25-year period, 17,334 herring gulls were admitted into the Mallydams Centre with 9,013 released, and 2,796 ringed and released between 1999 and 2010. Release rates varied significantly with the category of problem identified at admission. Wild nesting herring gulls, even without the impact of HPAI, have been declining throughout the UK, and the additional anthropogenic pressures on urban gull populations have resulted in a documented national decline in the species. Rehabilitating and returning birds to the wild has shown to be important both for their animal welfare and population, as well as helping identify the impact of HPAI on local urban populations of all relevant species. Results from this research can be utilised to adapt training and resources at rehabilitation centres and determine euthanasia protocols to optimise animal welfare along with release and survival success.
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    Bone marrow fat content analysis confirms starvation as a cause of death for Australasian bitterns (Botaurus poiciloptilus) in New Zealand
    (Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-03-20) Williams EM; Jarman T; Battley PF; Briskie J
    Wildlife managers conserving threatened species rely on information about causes of population declines. Finding carcasses to record cause of death, sickness or injury in a timely manner is challenging. We used fat content in bone marrow from deceased Australasian bitterns (Botaurus poiciloptilus) to determine whether birds had starved by comparing results among 34 bitterns where the cause of death was assigned via independent autopsies. Fat content was near zero in the eight specimens that died of starvation. Many other specimens had depleted fat content, 17 of which were recorded as dying from impact trauma. This evaluation provided confidence to interpret our database of 126 Australasian bittern mortality records evaluated via autopsy or observation. The most common causes of death were impact trauma (56.3%; mainly vehicles and powerlines) and starvation (17.5%) with a further 5.8% having characteristics of both starvation and impact trauma raising the issue of whether starvation contributed to the deaths of individuals where impact trauma was the primary cause of death or vice versa. Although this dataset is biased by specimens more easily observed by the public, the occurrence of starved/near starved bitterns is of conservation concern and indicates wetland food supplies are likely under stress.
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    Fertility and survival of Swedish Red and White × Holstein crossbred cows and purebred Holstein cows
    (y Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association, 2023-04) Pipino DF; Piccardi M; Lopez-Villalobos N; Hickson RE; Vázquez MI
    Swedish Red and White × Holstein (S×H) cows were compared with pure Holstein (HOL) cows for fertility and survival traits in 2 commercial dairy farms in central-southern Córdoba province, Argentina, over 6 years (2008-2013). The following traits were evaluated: first service conception rate (FSCR), overall conception rate (CR), number of services per conception (SC), days open (DO), mortality rate, culling rate, survival to subsequent calvings, and length of productive life (LPL). The data set consisted of 506 lactations from 240 S×H crossbred cows and 1,331 lactations from 576 HOL cows. The FSCR and CR were analyzed using logistic regression, DO and LPL were analyzed using a Cox's proportional hazards regression model, and differences of proportions were calculated for mortality rate, culling rate, and survival to subsequent calvings. The S×H cows were superior to HOL cows in overall lactations for all the fertility traits (+10.5% FSCR, +7.7% CR, -0.5 SC, and 35 fewer DO). During the first lactation, S×H cows were superior to HOL cows for all fertility traits (+12.8% FSCR, +8.0% CR, -0.4 SC, and 34 fewer DO). In the second lactation, S×H cows exhibited lower SC (-0.5) and 21 fewer DO than HOL cows. In the third or greater lactations, S×H cows showed higher FSCR (+11.0%) and CR (+12.2%), lower SC (-0.8), and 44 fewer DO than pure HOL cows. In addition, S×H cows had a lower mortality rate (-4.7%) and a lower culling rate (-13.7%) than HOL cows. Due to the higher fertility and lower mortality and culling rates, the S×H cows had higher survival to the second (+9.2%), third (+16.9%), and fourth (+18.7%) calvings than HOL cows. Because of these results, S×H cows had longer LPL (+10.3 mo) than HOL cows. These results indicate that S×H cows had higher fertility and survival than HOL cows on commercial dairy farms in Argentina.
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    Factors Associated with Ewe Death and Casting in an Extensively Farmed Sheep Flock in New Zealand
    (MDPI (Basel, Switzerland), 2021-12) Capdevila-Ospina K; Corner-Thomas RA; Flay KJ; Kenyon PR; Ridler AL; Garcia Ispierto I
    Ewe deaths affect the productivity and profitability in sheep farming systems and have potential animal welfare and market perception implications. Internationally, there is scant data on the timing and causes of ewe deaths in extensive grazing systems. There is no published literature on the incidence and risk factors associated with casting (ewe in late gestation accidentally immobilised, often in dorsal recumbency). This study, undertaken using a cohort of 1789 ewes on a New Zealand farm, reports on the timing and risk factors associated with production parameters for ewe deaths through an almost two-year period, along with causes of death during both peripartum periods. Ewe deaths occurred throughout both years but were most frequent during the peripartum (pre-lambing to mid-lactation) period. Casting was the most commonly identified cause of death in both years, responsible for approximately a quarter to a third of potential annual mortality. Few risk factors for death or casting were identified. In conclusion, the peripartum period is a high-risk time period for ewe deaths (and, by extension, will also contribute to lamb perinatal mortality). In extensively grazed flocks where casting events occur, it is recommended that all ewes are monitored daily during the peripartum period.
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    Factors Associated with Mortality of Lambs Born to Ewe Hoggets
    (MDPI (Basel, Switzerland), 2022-02) Ridler AL; Flay KJ; Kenyon PR; Blair HT; Corner-Thomas RA; Pettigrew EJ
    The reproductive performance of ewe hoggets is poorer than that of mature-age ewes due to production of fewer lambs with poorer survival. Scant data are available on the risk factors for, and causes of, the mortality for lambs born to ewe hoggets, the impact of ewe deaths on lamb loss, and the causes of death for lambs born to ewe hoggets vs. mature-age ewes lambing in the same circumstances. In this study, 297 lambs born to 1142 ewe hoggets were necropsied along with 273 lambs born to 1050 mature-age ewes. Low lamb birthweight, multiple litter size, and increasing ewe hogget average daily gain from breeding to late pregnancy were risk factors for lamb mortality. The most common cause of mortality for lambs born to ewe hoggets was stillbirth and the risk factors for stillbirth were similar to those for lamb mortality generally. Approximately 11% of ewe hoggets’ lamb deaths were due to the death of the dam. Causes of mortality differed between lambs born to ewe hoggets vs. those born to mature-age ewes. Management practices to increase ewe hogget lambs’ birthweights (particularly those from multiple litters) and supervision of ewe hoggets at lambing time are recommended.
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    Growth, milk production, reproductive performance, and stayability of dairy heifers born from 2-year-old or mixed-age dams
    (Elsevier Inc and Fass Inc on behalf of the American Dairy Science Association, 2021-11) Handcock RC; Lopez-Villalobos N; Back PJ; Hickson RE; McNaughton LR
    Keeping replacement heifers that were the progeny of primiparous cows mated by artificial insemination enhances rates of genetic gain. Previous research has shown that heifers that were the progeny of primiparous cows were lighter at birth and grew at a slower rate to first calving compared with heifers born to multiparous dams. Furthermore, heifers that were heavier before first calving produced more milk than did lighter heifers. This study aimed to determine whether there were body weight, milk production, or reproductive disadvantages for heifers born from primiparous compared with multiparous dams. Data comprised body weight records from 189,936 New Zealand dairy heifers. Dams were allocated to 4 groups according to their age: 2 yr old (n = 13,717), 3 yr old (n = 39,258), 4 to 8 yr old (n = 120,859), and 9 yr or older (n = 16,102). Heifers that were the progeny of 2-year-old dams were lighter from 3 to 21 mo of age than heifers that were the progeny of 3-yr-old and 4- to 8-yr-old dams. The progeny of 2- and 3-yr-old dams produced similar milk solids yields (± standard error of the mean) during their first lactation (304.9 ± 1.6 and 304.1 ± 1.5 kg, respectively), but more than that of 4- to 8-yr-old dams (302.4 ± 1.5). Furthermore, the progeny of 2-yr-old dams had similar stayabilities to first, second, and third calving to that of the progeny of 4- to 8-yr-old and ≥9-yr-old dams. Reproductive performance, as measured by calving and recalving rates was similar in first-calving heifers of all age-of-dam classes. Additionally, second and third calving rates were similar for the progeny of 2- and 3-yr-old dams. Interestingly, the progeny of dams ≥9 yr old had the lowest milk solids production in first (297.8 ± 1.6 kg), second (341.6 ± 1.8 kg), and third lactations (393.2 ± 2.4 kg). Based on the results of this study, keeping replacements from dams aged 9 yr and over could not be recommended. Furthermore, heifers born to 2-yr-old dams were lighter but produced more milk than heifers from older dams, in addition to having superior genetic merit.