Inclusion of calcium propionate in late gestation protein supplements increases subsequent offspring marbling scores in range beef cows

A 3-yr study evaluated the effect of late gestation supplementation strategy on cow-calf performance, subsequent steer feedlot performance, and carcass characteristics. Mature March-calving crossbred cows (n = 357) were stratified by body weight (BW) and body condition score (BCS) and assigned to one of 4 treatments: 1) no supplementation (<b>NoSupp</b>), 2) 0.91 kg/d of a 30% CP distillers-based supplement (DBS) (<b>Supp</b>), 3) 0.91 kg/d of a 30% CP DBS with 160 mg/cow/d of monensin (<b>RUM</b>; Rumensin 90, Elanco Animal Health), and 4) 0.91 kg/d of a 30% CP DBS with 40 g/cow/d propionate salt (<b>CaProp</b>, NutroCal 100, Kemin Industries). Cows were individually supplemented daily using a Super SmartFeed (C-Lock Inc., Rapid City, SD) from November to February. After weaning, steers (n = 181) were transported to the West Central Research and Extension Center and placed in a GrowSafe feeding system for finishing. Steers were slaughtered at a commercial facility (Tyson Fresh Meats, Lexington, NE) after fed to a common endpoint each year. Cow BW was not different (<i>P</i> = 0.87) at the initiation of the study in November. However, NoSupp cows were lighter (<i>P</i> < 0.01) at pre-calving and pre-breeding compared to supplemented cows. In contrast, NoSupp cows lost less (<i>P</i> < 0.01) BW from pre-calving to pre-breeding than supplemented cows and gained more (<i>P</i> = 0.01) BW from pre-breeding to weaning. Treatment tended to influence overall pregnancy rates (<i>P</i> = 0.09). Supp and CaProp dams had increased pregnancy rates over NoSupp and RUM (<i>P</i> ≤ 0.05). Offspring from NoSupp dams had lighter (<i>P</i> < 0.01) BW at birth, pre-breeding, and weaning than their counterparts from supplemented dams. In addition, steer feedlot entry, final BW, and hot carcass weight were greater (<i>P</i> < 0.01) when dams were supplemented compared to NoSupp. Steer feedlot average daily gain and gain:feed ratio was not influenced (<i>P</i> ≥ 0.31) by dam supplementation strategies; however, dry matter intake tended (<i>P</i> = 0.09) to be influenced by treatment. Percentage of carcasses grading Choice or greater was not influenced (<i>P</i> = 0.66) treatment; however, steers from dams fed CaProp had increased (<i>P</i> = 0.04) marbling scores. Protein supplementation during late gestation is an effective strategy to increase cow BW, maintain cow BCS, and increase progeny BW. Providing dams with propionate salts during late gestation positively improved marbling score of the subsequent steer carcass characteristics.