Heat stress in confined growing cattle
Are limit feeding and providing shade effective mitigation strategies?
By Dale A. Blasi, A. J. Tarpoff and Jason M. Warner
Heat stress causes significant financial loss to the cattle industry each year through its’ negative impacts on animal welfare and performance. Shade is one heat mitigation strategy that has received considerable attention in finishing cattle, yet little prior research has been done focused on cattle during the growing phase.
Limit feeding a high-energy diet has been demonstrated to improve feed efficiency in growing calves compared with feeding a high-roughage diet fed for ad libitum intake and may also aid in mitigating heat load.
If shade and limit feeding each have independent benefits, what is the impact on performance, water consumption and animal comfort when the two management practices are combined and implemented with growing cattle? This was evaluated recently by researchers at the Kansas State University Beef Stocker Unit near Manhattan, Kansas (DeBord et al., 2023; Effects of Limit Feeding and Shade Allocation on Growing Calf Performance, Water Usage, and Animal Comfort (newprairiepress.org) )[1].
During May and June 2021 and 2022 black hided heifers (n = 852) weighing approximately 550 lbs. were assigned to pens containing nine to 12 heifers per pen, and pens were assigned to one of four treatments for a total of 40 pens and 10 replications per treatment per year.
The treatments included two factors: 1) shade (77 ± 6.3 ft2 of shade per animal) or no shade and 2) either a high-energy diet formulated to provide 60 Mcal of net energy for gain (NEg) per 100 lbs. of dry matter fed at 2.2% of body weight daily (60) or a high-roughage diet formulated to provide 45 Mcal of NEg per 100 lbs. of dry matter fed for ad libitum intake (45), thus a total of four different treatments.
Ingredient composition of experimental diets is presented in Table 1. A third diet that was formulated to contain 53 Mcal of NEg per 100 lbs. of DM was not part of the formal treatment structure but was fed to all treatments from day 90 to 97 during the gut-fill equilibration period.
Effects of diet Average daily gains from day 0 to 97 were greater (P < 0.01) for limit-fed heifers compared with heifers fed for ad libitum intake (Table 3). By design, dry matter intake was greater for calves fed for ad libitum intake through day 90. Dry matter intake did not differ (P = 0.69) between treatments during gut-fill equilibration period (day 90 to 97), which was expected because all cattle were limit fed during this time.
A diet effect was observed through day 97 for gain-to-feed where calves fed for ad libitum intake had worse feed efficiency compared with limit-fed calves. This better efficiency is associated with a lower dry matter intake of limit-fed calves compared with calves fed for ad libitum intake while average daily gains were greater for limit-fed calves compared with calves fed for ad libitum intake.
Heifers fed for ad libitum intake spent more time ruminating than limit-fed heifers (P < 0.01; Table 3), which was associated with greater dry matter intake and greater dietary forage concentration. Likewise, limit-fed heifers were more active (P < 0.01) compared with heifers fed for ad libitum intake.
Dietary treatments did not affect mean panting scores. Limit-fed calves used 9% less (P < 0.01) water when compared with calves fed for ad libitum intake. Differences in water usage between diets may be attributed to differences in dry matter intake.
Effects of shade Heifers provided shade had heavier (P < 0.01) day 90 and day 97 body weights compared to heifers without access to shade. Average daily gains from day 0 to 97 were greater (P < 0.01) for shaded heifers compared with non-shaded heifers.
Calves fed for ad libitum intake in shaded pens had greater (P < 0.01) dry matter intake compared with calves in non-shaded pens fed for ad libitum intake, whereas limit-fed calves in non-shaded pens and shaded pens did not differ in dry matter intake. Gain-to-feed was better (P < 0.01) for calves in shaded pens compared with calves in non-shaded pens.
Limit-fed heifers in shaded pens spent less time ruminating (P < 0.01) compared with limit-fed heifers in non-shaded pens; however, rumination time of calves fed for ad libitum intake was not affected by provision of shade. Heifers in shaded pens tended to be more active (P = 0.10) compared with heifers in non-shaded pens.
Calves in non-shaded pens had greater (P < 0.01; Figure 1) mean panting scores than calves in shaded pens. We attribute this difference to an increase in animal comfort due to reduced solar radiation exposure to calves in shaded pens, which led to a lower heat load during the summer.
Water usage was 11% less (P < 0.01; Table 3) for shaded calves compared with non-shaded calves. This can be attributed to a decrease in heat load of calves in shaded pens compared with calves in non-shaded pens.
These data demonstrate limit feeding a high-energy diet to growing cattle during the receiving period can improve feed efficiency and reduce water usage when compared to a higher forage diet fed for ad libitum intake, regardless if shade is provided or not.
Furthermore, these results suggest providing shade during the summer can improve cattle comfort and reduce water usage, ultimately improving gain to feed in pen-fed growing cattle.
References[1] DeBord, Z. L., Z. M. Duncan, M. G. Pflughoeft, K. J. Suhr, W. C. Ellis, W. R. Hollenbeck, S. P. Montgomery, T. J. Spore, E. C. Titgemeyer, D. A. Blasi, and A. J. Tarpoff. 2023. Effects of limit feeding and shade allocation on growing calf performance, water usage, and animal comfort. Kansas State University Cattlemen’s Day 2023. Kansas Agricultural Experiment Station Research Reports. Vol. 9: pg 1-3.
Blasi is an Extension beef specialist, Tarpoff is an Extension veterinarian and Warner is an Extension cow-calf specialist, all with the Department of Animal Sciences and Industry, Kansas State University.
