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Bunk space requirements for limit-fed growing beef cattle not as large as thought

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Bunk allotments of 10, 15, 20, or 25 inches per calf had minimal impact on growth performance and final bodyweights.

By Zach Duncan, doctoral student and Dale Blasi, stocker, forages, nutrition and management specialist

Previous research conducted at the KSU Beef Stocker Unit with limit fed high-energy corn and corn co-products has established that feed efficiency is improved with a reduction in manure production in growing calves. One aspect of limit-feeding growing calves is the concern of insuring that sufficient bunk space is available to allow all calves the opportunity to gain access to feed when offered. 

Of course, the costs of bunks and the associated concrete aprons is an expensive consideration, especially if a producer cannot carry the same number of calves in a pen as when providing feed in a full-fed, ad-libitum environment. The current recommendation for growing beef cattle fed ad libitum (i.e., 500-700 lbs) is 18 inches of bunk per head. Cattle fed ad libitum have access to feed throughout the day; whereas limit-fed cattle generally consume feed offered within six hours after feed delivery. Under limit-fed conditions, inadequate bunk space could result in overconsumption by aggressive calves which could potentially cause digestive disorders. In addition, less aggressive calves could potentially have limited access to feed which could result in reduced performance.

To ascertain the bunk space requirements for limit-fed growing cattle, a 58-day feeding study was conducted with 385 crossbred steers (initial body weight 473 ± 56 lb) purchased in Texas and transported to the Kansas State Beef Stocker Unit. Calves were randomly assigned to 1 of 4 treatments which resulted in 7 pens per treatment for a total of 28 pens. Pens were equal in size (30 ´ 50 feet) and contained fenceline feed bunks and 12-foot concrete aprons. Bunk length was adjusted to allow 10, 15, 20, or 25 inches of bunk space per calf.

Individual bodyweights were measured on d 0, d 29, and d 58. In addition, pen weights were collected weekly (d 0, 14, 21, 28, 35, 42, 49, and 56) and were used to calculate feed delivered for the following week. Steers were fed once daily at 7:00 a.m. using a Roto-Mix feed wagon. The experimental diet was composed (DM basis) of 13% prairie hay, 39.5% Dry-rolled corn, 40% Sweet Bran and 7.5% supplement and was offered at 1.8% of bodyweight daily (dry matter basis) from February 2 to March 13, 2021. Thereafter, the daily feed allotment was increased to 2.0% of bodyweight.

Following the 58-day feeding period, final body weights did not differ (P = 0.15) between treatments (Table 1). Average daily gains increased linearly (P = 0.03) with increased bunk space for the first 29-days; however, no trends were observed thereafter. In addition, no differences in dry matter intake (P = 0.34), gain-to-feed ratio (P = 0.39), or feed-to-gain ratio (P = 0.96) were observed between bunk space treatments. When evaluating subsequent growth performance during the grazing season, body weights did not differ (P = 0.25) between bunk space treatments at the beginning or the completion of the grazing period; however, total bodyweight gains and average daily gains increased linearly (P ≤ 0.01) with decreased bunk space. It appeared that reduced bunk allotment had minimal impact on growth performance during the receiving period but were associated with improved bodyweight gains throughout the grazing season. Conversely, overall total body weight gains and average daily gains were not different (P = 0.29) between treatments at the completion of the study.

We interpreted our data to suggest that bunk allotments of 10, 15, 20, or 25 inches per calf had minimal impact on growth performance during a 58-day receiving period and did not affect final body weights at the completion of a 90-day grazing season.

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