The primary goal of a cow-calf operation is to produce one calf per cow per year. However, the journey to achieving this reproductive success is fraught with challenges influenced by a variety of factors, including genetics, nutritional status, and stress, each playing a crucial role in the performance of heifers. Scientific literature highlights that heifers’ reactivity at handling (a proxy for temperament) tend to diminish their feed intake, adversely affecting their nutritional status. Additionally, excitable animals often have higher circulating concentrations of cortisol (a stress hormone). As the cortisol levels rise, so does the concern for the fertility of beef females.
A comprehensive two-year study was conducted by the Olds College Technology Access Centre for Livestock Production (TACLP) at Neilson Beef in Stettler, Alta, investigating reproductive efficiency and alleviating stress in beef heifers. The Neilsons provide custom feeding services to beef producers and are currently in their fourth year of providing a specialized heifer development service for the beef industry. Thus, the main goal of the research was to assess the effects of a cost-effective strategy, referred to as acclimation, which involves a combination of repeated non-aversive handling and positive feed reinforcement before breeding, on heifers' stress and pregnancy rates.
The central focus of this project was addressing the challenge posed by observed excitable reactivity in cattle during routine handling, a factor that often results in injuries to both handlers and animals. In the first year, 200 Angus crossbred heifers, aged 13-14 months were enrolled. Prior to the breeding season, all heifers were ranked by body condition score and were subsequently divided into four equivalent groups. These groups were housed in distinct feedlot pens (50 heifers per pen per treatment) for approximately four weeks, with two groups assigned to each treatment — acclimation or control.
Dr. Gellatly collects saliva samples from heifers using cotton swabs to further salivary cortisol concentration assessment.
The acclimation process combined feed reinforcement and non-aversive successive handling techniques, aiming to reduce stress levels towards handlers and handling facilities. Briefly, prior to breeding and for five alternate days, a familiar handler entered the acclimated treatment pens. The handler adopted a soft-spoken approach while pail-feeding the heifers with a small amount of mixed barley (approximately 100 grams per heifer). This method aimed to create, under animals’ perspective, a positive association of humans. Subsequently, these heifers were guided through the chute on three separate days (adopting low-stress handling techniques and without restraint), receiving identical feed rewards immediately after handling. Conversely, heifers in the control groups were solely fed by a feed truck without any human interaction and were not exposed to handling acclimation procedures before breeding.
During the second year, a new group of 122 Angus crossbred heifers, aged 13-14 months, underwent an identical evaluation to the one conducted in the 2020 study, ensuring consistency in experimental procedures.
During both trial years, a veterinarian performed rectal palpation on all heifers before hormone treatment. Cycling heifers with a corpus luteum were given intramuscular injections of PGF2α (Estrumate®; Merck Animal Health) for estrus synchronization purposes.
In both years, heifers were randomly selected to be either exclusively exposed to bulls (Black Angus & Gelbvieh sires; approximately 1:25 bull-to-cow ratio) or subjected to artificial insemination (AI) before bull exposure (~100 heifers per breeding method). Cattle reactivity to handling was assessed using two different methods, chute score and flight speed, providing insights into excitability while enclosed in the squeeze chute and the exit speed from a hydraulic squeeze chute, respectively. In the initial year, saliva samples were collected to measure salivary cortisol concentration as an indicator of acute stress. Following the breeding season, pregnancy rates were determined using ultrasonography. Behavioral assessments and salivary samples were obtained before breeding (baseline measurement), during estrus synchronization, and on pregnancy check day.
The outcomes on pregnancy rate for both treatment groups were independent of the breeding methods (natural or AI). Acclimated heifers exhibited a numerical rise of 2.23% in pregnancy rates compared to the control group in the initial year. In the second year, utilizing the new set of animals, this increase significantly escalated to 10.84%. Additionally, in the second year, the adoption of handling acclimation procedures elevated the likelihood of heifers becoming pregnant by 7.5 times.
During the baseline assessment (prior to acclimation) in the first year, heifers from both treatment groups exhibited similar salivary cortisol concentrations. However, post-acclimation (on synchronization and pregnancy check days), heifers that underwent acclimation showed significantly lower cortisol concentrations. This suggested a notable reduction in stress levels at handling compared to the control group.
In the second year, handling acclimation successfully decreased reactivity in home-raised heifers at Neilson Cattle Development compared to externally sourced heifers, as evidenced by significantly lower flight speed.
After analyzing outcomes of the two year study, the Neilsons have opted to permanently integrate handling acclimation protocols for all heifers and cows raised at their operation, as well as for their customers' heifers. In the latest breeding season, Neilsons observed no instances of open heifers subjected to either natural breeding or AI after receiving handling acclimation procedures. Additionally, Neilson’s customers, whose heifers experienced handling acclimation at Neilson’s operation within the last three years, also observed an 100% of pregnancy rate. In terms of time commitment, there is a requirement to handle cattle up to 2 weeks prior to breeding or other processing procedures. However, the Neilsons indicated that a group of up to 100 heifers being handled only by him and his wife, Karyn Neilson, incurred 15 minutes of time per session to perform the acclimation procedures. Further, they emphasized that the minimal time invested into acclimating their animals is well worth the results.
“Frequently, beef producers express concerns that handling animals more often will increase stress levels. Nonetheless, our research indicates that consistently and gently managing cattle can actually reduce stress and anxiety during routine procedures”, explains Dr. Gellatly. The owner and operator, Lance Neilson, emphasizes that the improved fertility rate is evident, but he particularly highlights his own observation of the reduced hesitation of acclimated heifers when entering the calving barn. He noticed a more efficient calving process from an operational perspective.
Visit the TACLP webpage and watch for upcoming handling workshops with Dr. Gellatly.
By Dr. Désirée Gellatly, Ph.D.