Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2024
Publication Date: 7/8/2024
Citation: Continanza, G., Cibils, A.F., Petersen, M.K., Muscha, J.M., Roberts, A.J., Steele, C., Soto-Navarro, S., Steiner, R.L., Cao, H., Gong, Q. 2024. Effect of post-weaning development method on spring grazing patterns of rangeland beef heifers. Livestock Science. 286. Article 105523. https://doi.org/10.1016/j.livsci.2024.105523.
DOI: https://doi.org/10.1016/j.livsci.2024.105523

Interpretive Summary: Heifers developed using different post-weaning protocols showed differences in movement and activity patterns during early spring. Such differences tended to decrease over time presumably due to social facilitation. Differences in pasture use patterns, however, tended to persist. Developing heifers on rangeland providing a self-fed high protein supplement during winter tended to encourage energy-conserving foraging skills that persisted for the duration of the experiment. Heifers with stronger social connections did not belong to a specific treatment group, which might indicate that personalities or temperament may have a high impact on how social facilitation occurs when heifers developed using different protocols graze together during spring. The degree to which heifers’ requirements were met with non-range forage feeds, whether supplements or bunk silage (PFS>GFC>SFP) appeared to exert a stronger influence on a heifer’s grazing patterns than the winter foraging environment itself (dry lot vs. rangeland). Additional information about indicators of metabolic memory (i.e., body condition and initial weight) would significantly improve understanding about the mechanisms underlying the grazing behavior patterns observed in this study.

Technical Abstract: We determined the influence of post-weaning development method on rangeland grazing patterns of beef heifers during early and late spring. We compared behavior of heifers wintered on rangeland (group-fed cake, GFC or self-fed protein, SFP supplements during winter) or in a pen where they were pen fed silage (PFS). In April and May of each year (n=3), heifers (n=95) were fitted with Lotek 3300LR GPS collars and monitored 18 days each month. PFS heifers 37 traveled farther than SFP and GFC counterparts on the first few days in April (P<0.05). PFS heifers covered larger areas of the pasture compared to GFC and SFP (P<0.05) counterparts during May. All heifers followed trajectories of similar sinuosity (P>0.05). On most days, PFS heifers allocated more time to resting (April) and traveling (April and May) than heifers in SFP treatment (P<0.05). SFP heifers spent significantly more time grazing than PFS and GFC counterparts during April (P<0.01). However, differences in foraging patterns decreased through time. All heifers spent more time grazing (P<0.01) on cloudy days with higher humidity during April and less time grazing on windy and rainy days in May (P<0.05). Pixel Normalized Difference Vegetation Index (NDVI) appeared to influence pasture use patterns regardless of treatment. Traveling and resting time, as well as pixel residence time were the three variables that best discriminated heifers into treatment groups (P<0.01). Collared heifers tended to associate with heifers of their own/other treatment group (prevailing PFS-GFC or GFC-SFP heifers). The social role of a collared heifer in the herd did not appear to be associated with development treatment. Post-weaning development protocols modified movement, activity, and habitat use of heifers during early spring. Initial animal state and/or metabolic memory may have been responsible for the differences observed. Such differences, however, were possibly attenuated by social facilitation.