Extension

Research has shown that limit feeding newly received beef cattle a high-energy diet during the growing period can improve feed efficiency without negatively influencing animal health compared with feeding a high-roughage diet for ad libitum intake.^{1, 2} One concern associated with limit-fed diets is the potential need to increase bunk allotments to allow all cattle to eat at one time. The Guide for the Care and Use of Animals in Agricultural Research and Teaching recommends 18 to 22 inches of bunk per head for cattle that weigh 397 to 838 lb and are fed once daily.³ However, a survey of consulting feedlot nutritionists indicated that the minimum bunk allotment for newly received cattle averaged 12 inches of bunk per head but ranged from 6 to 18 inches of bunk per head.⁴ Since feed bunks represent a significant investment for cattle feeders, if bunk allotments must be increased for limit-fed cattle relative to cattle fed ad libitum, the expected improvements in feed efficiency and cost savings associated with limit feeding may not outweigh the cost of additional bunks.

 

An additional concern associated with reducing bunk allotments for limit-fed cattle is that aggressive cattle will consume a majority of the feed provided and less aggressive cattle will not have the opportunity to consume their intended allocation. Overconsumption by aggressive calves and underconsumption by non-aggressive calves could potentially create differences in growth performance within the pen. Previous experiments that evaluated bunk space requirements for limit-fed cattle were in small pens (range: 4 to 14 cattle per pen). Larger pen sizes could result in more aggression at the feed bunk in comparison with pens with fewer cattle. Thus, Kansas State University research evaluated the effects of bunk allotment on growth performance of receiving beef heifers limit fed a diet based on high-energy corn and corn co-products, in pens that contained 18 to 28 heifers.⁵

 

In this study, 332 crossbred heifers (initial body weight [BW] = 659 lb) were blocked by origin, stratified by individual arrival BW, and assigned to pen within block. Pens were randomly assigned to 1 of 4 treatments (4 pens per treatment) that provided 6, 10, 14, or 18 inches of bunk space per heifer. Heifers were limit-fed a high energy diet (formulated to provide 88 and 59 Mcal of NEm and NEg per 100 lb of dry matter [DM], respectively) once daily beginning at 7:00 a.m. at 2.0% of BW (DM basis) for 56 days . Individual BW were measured at the start and end of the feeding period (days 0 and 56). Pen weights BW was measured weekly and used to adjust feed delivered for the following week. Feed bunks were evaluated daily at 3 hours after feeding using a feed bunk scoring system. Bunks were assigned a score of 1 to 6 based on the amount of feed that remained. A score of 1 represented an empty bunk with no feed residue remaining, whereas a score of 6 indicated greater than 30% of feed delivered that day remained.

 

The growth performance data are presented in Table 1. Final BW did not differ among treatments (P = 0.23). Similarly, bunk allotment did not affect average daily gain (ADG), DM intake (DMI), and gain-tofeed ratio (P ≥ 0.17). One concern associated with bunk space requirements for limit-fed cattle is how bunk allotments might affect the variability of weight gain within a pen. These researchers observed a quadratic effect (P = 0.05) of bunk allotment on the standard deviation (SD) of ADG where heifers allotted 14 inches of bunk per head had greater variation in weight gain within the pen compared with pens allotted 6, 10, or 18 in of bunk per head.

 

¹Heifers were allotted 6, 10, 14, or 18 inches of bunk per head and limit fed at 2.0% of BW

daily (DM basis) for 56 days.

²Standard deviation of ADG was calculated for each pen using gains of individual heifers.

 

The effects of bunk space allotment on proportions of cattle eating and bunk scores are shown in Table 2. To determine how bunk allotment influenced the number of heifers that could eat at one time, the proportion of heifers consuming feed at the bunk was determined at feeding and 2 hours after feeding. As expected, the proportion of heifers that could simultaneously access feed increased linearly (P < 0.01) as bunk allotment increased. Overall, 43%, 62%, 79%, and 96% of heifers within each pen could access the feed bunk at feeding for heifers allotted 6, 10, 14, and 18 inches of bunk per head, respectively. These researchers noted that “based on visual observations, aggressive heifers would eat initially in pens where bunk space was restricted; however, these heifers would consume their initial meal and then allow less aggressive heifers access to feed”.

 

¹Heifers were allotted 6, 10, 14, or 18 inches of bunk per head and limit fed at 2.0% of BW

daily (DM basis) for 56 days.

²Proportion of the pen eating out of the feed bunk.

³Determined 3 hours after feeding.

 

The proportion of heifers eating at the bunk 2 hours after feeding also increased linearly (P < 0.01) as bunk allotment increased. At 2 hours after feeding, 29%, 30%, 38%, and 36% of heifers within each pen were at the feed bunk for heifers allotted 6, 10, 14, and 18 inches of bunk per heifer, respectively. Bunk scores measured 3 hours after feeding did not differ (P = 0.71; Table 2) among treatments. Overall, it appeared that all heifers had adequate access to feed which was further supported by the lack of a difference in the variation of ADG within pens.

 

These authors concluded that “bunk allotments as low as 6 to 18 inches per heifer can be used without negatively influencing growth performance of growing beef heifers of about 639 to 794 lb of BW that are limit fed a high-energy diet at 2.0% of BW (DM basis) once daily in pens that contained 18 to 28 head”.

 

¹ Spore, T. J., S. P. Montgomery, E. C. Titgemeyer, G. A. Hanzlicek, C. I. Vahl, T. G. Nagaraja, K. T. Cavalli, W. R. Hollenbeck, R. A. Wahl, and D. A. Blasi. 2019. Effects of a high-energy programmed feeding protocol on nutrient digestibility, health, and performance of newly received growing beef cattle. Appl. Anim. Sci. 35:397–407. Available at: https://doi.org/10.15232/aas.2019-01853.

² Scilacci, M. A., E. C. Titgemeyer, Z. M. Duncan, T. J. Spore, S. P. Montgomery, T. G. O’Quinn, A. J. Tarpoff, W. R. Hollenbeck, and D. A. Blasi. 2024. Effect of traditional roughage-based or limit-fed, high-energy diets on growth performance and digestion in newly received growing cattle and subsequent implications on feedlot growth performance and carcass characteristics. Transl. Anim. Sci. 8. Available at:

https://doi.org/10.1093/tas/txae082.

³ FASS, 2020. Guide for the Care and Use of Animals in Agricultural Research and Teaching 4th ed. FASS, Champaign, IL.

⁴ Samuelson, K. L., M. E. Hubbert, M. L. Galyean, and C. A. Löest. 2016. Nutritional recommendations of feedlot consulting nutritionists: The 2015 New Mexico State and Texas Tech University survey. J. Anim. Sci. 94:2648-2663

⁵ Ellis, W. C., Z. M. Duncan, M. S. Grant, W. R. Hollenbeck, E. C. Titgemeyer, and D. A. Blasi. 2024. Restricting bunk space allotments to 15 or 25 centimeters per head has minimal effects on growth performance in limitfed growing beef heifers. Appl. Anim. Sci. 40:818–823. Available at: https://doi.org/10.15232/aas.2024-02625