Agriculture

Feeding Cull Beef Cows (Nutrition Update, Volume 7)

Questions arise periodically on rations and performance of cull beef cows. Limited information has been available but an article recently published in the Journal of Animal Science (1996, 74:1770) addresses these issues.

Sixty non-pregnant, British bred cows with BCS’s of 3-4 (scale 1-10) and over 5 years of age, were used in the study. Cows were divided into light (386-454 kg) and heavy (454 to 522 kg) weight groups. Cows were fed for 28 or 56 days and received either 1) no implant, 2) trenbolone acetate (TBA), 3) Synovex H (TEB) or 4) both TBA and TEB.

A starter ration (56% concentrate, DM basis) was fed for approximately 7 days. Cows were then switched to the 80% concentrate diet. Ration composition is show in Table 1. Cow performance and carcass data is shown in Table 2.

Table 1. Composition of diets fed to cull beef cows on a dry matter basis.

Ingredient Warm-up Diet High-concentrate Diet
Rolled corn 23.90 56.00
Sorghum silage 72.20 39.30
Soybean meal (44% CP) 3.04 3.67
Limestone .55 .66
Salt .19 .23
Urea .08 .09
Trace mineral premix .03 .03
Rumensin 60 .00025 .00025

  

Table 2. Performance and carcass data of cull cows fed for 28 days and 56 days.

Days on Feed
Trait 0 28 56
ADG (kg) - 2.12 1.99
DMI (kg/day) - 11.8a 13.3b
Feed: gain - 5.57a 6.68b
Dressing % 52.1b 50.6a 54.0c
Hot carcass (kg) 238.2a 262.3b 308.7c
Adj. fat thickness (cm) 0.43a 0.73b 1.1c
LM area (cm2) 66.8a 74.9b 80c
a,b,c, numbers in the same row with different superscripts are statistically different

 
Feeding thin cows a high concentrate diet for 28 days improved quality grade, longissimus muscle (LM) area and sensory traits. Feeding for 56 days improved LM lean and carcass fat color. Full feeding of thin beef cows for 28 or 56 days increased carcass weight, carcass soft tissue and fat.

All implant treatments gained and converted more efficiently than the non-implanted controls and the combination implant treatment was superior to single implants. Implants also improved juiciness and tenderness scores.

Nutrition Update
Volume 7 No. 4, February 1997