Long-term effects of pre-weaning individual or pair housing of dairy heifer calves on subsequent growth and feed efficiency

Authors: RIESGRAF, KAYLEE - University Of Wisconsin; WEIGEL, KENT - University Of Wisconsin; Akins, Matthew; VAN OS, JENNIFER - University Of Wisconsin

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2024
Publication Date: 2/24/2024
Citation: Riesgraf, K., Weigel, K., Akins, M.S., Van Os, J. 2024. Long-term effects of pre-weaning individual or pair housing of dairy heifer calves on subsequent growth and feed efficiency. Animals. https://doi.org/10.3390/ani14050716.
DOI: https://doi.org/10.3390/ani14050716

Interpretive Summary: Preweaning pair housing has many immediate cognitive, growth, and feed intake benefits; however, little is known about the duration of these advantages over individually housed heifers. Isolation stress preweaning may have lasting adverse effects on heifer growth and feed efficiency, potentially inflating heifer rearing costs and decreasing farm profitability. To investigate possible long-term effects of preweaning housing, we measured growth, feed efficiency, and methane emissions of 18-month-old heifers that had previously been paired or housed individually preweaning. Overall, pair-housed heifers maintained a body weight advantage over individually housed heifers with no adverse impacts on feed efficiency or methane emissions.

Technical Abstract: As the dairy industry strives to improve the sustainability and efficiency of heifer rearing, it is important to understand the potential long-term impacts of early life events, such as social isolation stress, on the efficiency and performance of growing heifers. Cognitive, growth, and feed intake benefits of pair housing dairy calves preweaning and immediately postweaning have been demonstrated previously. In the current study, our objective was to evaluate the long-term impacts of preweaning social isolation vs. social contact on subsequent growth, feed efficiency, and enteric methane emissions of Holstein heifers. As pre-weaned calves, 41 heifers were housed individually (n = 15 heifers) or in pairs (n = 13 pairs; 26 heifers). At 18 months of age, these heifers were blocked by body weight and randomly assigned to 1 of 3 pens within block (6 to 8 heifers per pen; 6 pens total), with original pairs maintained. Body weights (BW) were obtained on three consecutive days at the start and end of the trial. Hip height (HH), hip width, (HW), and chest girth (CG) were measured once at the start and end of the study. Each pen was allowed three days of access to a GreenFeed (GF) greenhouse gas emissions monitor. For the entire 9-week study, heifers were fed a common diet containing 62.3% male-sterile corn silage, 36.0% haylage, 0.7% urea, and 1.0% mineral (DM basis). To calculate daily intake, TMR weights and refusals were recorded for individual heifers using Calan gates. Feed samples were collected daily, composited by week, and dried to calculate DMI. Refusal and fecal samples were collected on three consecutive days at three timepoints, composited by animal, dried, and analyzed to calculate NDF, OM, and DM digestibility. Feed efficiency was calculated as feed conversion efficiency (FCE; DMI/average daily gain (ADG) and residual feed intake (RFI; predicted DMI - observed DMI). Paired and individually housed heifers did not differ in DMI, ADG, FCE, or RFI. Although no differences were found in initial or final HH, HW, or CG, heifers that had been pair-housed maintained greater BW than individually housed heifers during the trial. Methane production, intensity, and yield were similar between paired and individually housed heifers. Preweaning paired or individual housing treatments did not impact number of visits or latency to approach the GF, and approximately 50% of heifers in each treatment visited the GF within 8 hours of exposure. Digestibility of OM, DM, and NDF were also similar between housing treatments. In conclusion, preweaning pair housing is a socially sustainable rearing option with long-term body weight benefits and no adverse effects on feed efficiency or methane emissions at 18 to 20 months of age.