Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
Animal and Dairy Sciences
Non Technical Summary
Tail-docking is a routine husbandry practice performed in lambs to reduce fecal soiling and flystrike, but causes prolonged and painful inflammation. Stress to the immune system in early development can play an important role in shaping social behavior later in life. Alterations in social behavior, in turn, can have significant animal welfare and economic impacts. Maternal care may protect against the long-term effects of early life stress; however, lambs may be reared artificially when dam milk is not available in sufficient quantity. This project aims to investigate how early life management practices, such as tail-docking and artificial rearing in lambs, shape social behavior later in life.We will accomplish this goal by evaluating: (1) how tail-docking affects an individual's social affiliations during the post-weaning period, sexual behavior at 7 months of age, and maternal behavior at 1 year of age; and (2) whether these effects are amplified by separation from the dam at birth. Lambs will be assigned to 1 of 3 treatments: (1) reared with the dam and not tail-docked; (2) reared with the dam and tail-docked; (3) artificially reared and tail-docked. We predict that animals subjected to early life stress will maintain fewer social affiliations, have impaired sexual performance, and show reduced maternal behaviors towards their offspring. We further predict that this effect will be most pronounced in individuals that were tail-docked and reared artificially. This work will generate novel and much-needed information about the long-term effects of routine neonatal husbandry practices that will be disseminated to scientists, producers, and the public through publications, presentations, and outreach events.
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
0%
Developmental
0%
Goals / Objectives
The proposed research will explore how early life stress influences the social environment across the lifespan in sheep and whether these effects are buffered by maternal care. We hypothesize that tail-docking will result in a lasting reduction in prosocial behaviors and that this effect will be amplified in artificially reared lambs compared to those raised by the dam. To test this hypothesis, we propose 3 objectives that will evaluate the effect of early life stress on:Social network position during the post-weaning period. We predict that lambs subjected to early life stress will maintain fewer social affiliations, resulting in less central positions than their control pen-mates. We further predict that this effect will be most pronounced in the lambs that were tail-docked and reared artificially.Sexual behavior at puberty. We predict that early life stress will impair sexual performance, resulting in fewer complete sequences of courtship behavior and mounting attempts by rams, and decreased acceptance of mounting by ewes. We also predict that rams will direct less courtship behavior towards ewes subjected to early life stressors compared to control ewes.Maternal behavior in adulthood. We predict that ewes exposed to early life stress will engage in more non-maternal behaviors (eating, drinking, exploring, self-grooming) than maternal behaviors (grooming and nursing offspring) and that these maternal differences will predict lamb vitality, behavior, and growth.
Project Methods
We will use the triplets of 54 multiparous Polypay ewes (n=162 lambs) born and raised at the University of Wisconsin Arlington Research Station Sheep Unit. Triplets will be assigned to 3 cohorts based on birth date, with each cohort born 5 weeks apart. Within each triplet, lambs will be assigned to 1 of 3 treatments, balanced by sex and birth weight, within 24 hours of birth (n=18/treatment/cohort):No stressor: Lambs will be reared with the dam and not tail-docked. Ewes and their lambs will remain in an indoor lambing pen for 3 days after parturition. After this time, ewes and lambs will be moved to a group pen with outdoor access.Single stressor: Lambs will have their tails docked with rubber rings 36 hours after birth. Tails will be docked equivalent to the length of the vulva (Woodruff et al., 2020). Lambs will be reared with the dam as described above.Multiple stressors: Lambs will have their tails docked as described above. Immediately following birth, the lamb will be removed from the dam and raised in a peer group in a pen with outdoor access. Lambs will be fed sheep milk ad libitum from rubber teats to control for nutritional effects.During the pre-weaning period, all artificially-reared cohort lambs (MS) will be housed together (n=18). Dam-reared lambs (NS and SS) will be housed in two pens, such that all lambs in a cohort will be exposed to 17 other lambs during the pre-weaning period. All lambs will be weaned at 2 months of age.Objective 1 (Social network position): At weaning, all lambs from a single cohort will be weighed and mixed in one pen. On the day of mixing, lambs will be fitted with collars that contain a tracking device and a tri-axial accelerometer that collect data on the animal's location and activity, respectively (TrackLab, Noldus Information Technology, Netherlands). These low-power sensors use cutting-edge Ultra-Wideband technology to track animals with up to 15 cm accuracy and can transmit data at intervals of <1 s. The collars will remain on the lambs for 30 days. We will use the data to generate one association network, based on the entire study period, and 30 daily networks.We will use a Multiple Regression Quadratic Assignment Procedure to test whether early life stress predicts the structure of an individual's weighted proximity networks, while controlling for sex, weaning weight, and relatedness (Pinter-Wollman et al., 2014). We will also use generalized linear mixed models to investigate treatment effects on strength centrality and betweenness centrality. Each model will contain treatment, day, and their interaction as fixed effects. Individual identity, nested within triplet, will be fitted as random effects.Objective 2 (Sexual behavior): Assuming a 50:50 sex ratio, we will have 27 ewe lambs in each cohort. At 7 months of age, ewe lambs will be housed in pens of 3, with each treatment represented, for a total of 9 pens. Ewes will be treated with progesterone to induce an artificial estrus cycle. After estrus induction, we will randomly select 9 rams from each cohort (3/treatment) to introduce to each pen. Unselected rams will be slaughtered at the UW Meat Science & Animal Biologics Discovery Building and brain and tail tissue will be harvested for use in a different trial evaluating long-term anatomical changes following artificial rearing and tail-docking, pending other support.Rams will remain with the ewes for 3 days. During this period, each pen will be continuously recorded with a camcorder mounted on a tripod. Ewes will be marked with a paint stripe to facilitate individual recognition. Observers will be blind to treatments (with the exception of tail-docking) and will achieve good reliability (Cohen's Kappa > 0.90) before scoring behaviors using BORIS (Behavioral Observation Research Interactive Software). The number of incidences of anogenital sniffing, lateral approaches, flehmen, and accepted and rejected mount attempts, as well as total duration of courtship behaviors, will be recorded.We will test the effect of early life stress on individual counts of courtship behaviors using a generalized linear model. A general linear model will be used to assess treatment effects on the total duration of courtship behavior. Ram treatment, the treatment of the recipient ewe, and their interaction will be included as fixed effects.Objective 3 (Maternal behavior): Sixty days after ram removal, all ewe lambs will be tested for pregnancy by real-time ultrasound. Assuming a conservative 80% fertility rate (Gaskins et al., 2005) and no treatment effect on fertility, we estimate having 21 pregnant ewe lambs in each cohort (n=7/treatment). Behavior in the lambing pens will be monitored using continuous video recordings during the first 3 days after parturition. We will quantify the following ewe behaviors directed towards her offspring, as defined in Dwyer et al. (2001): grooming, withdrawing, nosing, butting, and preventing suckling attempts. The overt length of labor, calculated from appearance of fluids until birth of the last lamb, will also be recorded. We will evaluate lamb vitality at birth by observing the amount of time that has passed before a sternal recumbency or standing position has been achieved and suckling begins.Three days after parturition, ewes and lambs will be fitted with harnesses and collars, respectively, and moved to a group pen. We will use the combined location and accelerometer data recorded by the sensors to automatically monitor feeding, drinking, exploring, grooming, and nursing behaviors for 30 days. During this period, lambs will be weighed weekly on a digital scale to track growth.A linear model will be used to determine treatment effects on ewe behavior, length of labor, and lamb vitality immediately following parturition. Linear mixed models will be used to determine treatment x day effects on maternal and offspring behaviors, as well as lamb growth, during the 30-day study period. The paternal treatment will be included as a control variable in all models.Evaluation plan: We will evaluate whether our outcomes have been achieved through thoroughmonitoring and documentation of results. A robust data management plan will be employed, along withregularly scheduledchecks for data quality and relevance to project objectives. To maximize impact, we will publish and present in venuesthat best reach our intended audience.The PI and PhD student will meet regularly to critically review whether the project is maximizing its potential impact and develop approaches for corrective action, if needed.