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Cow herd profitability can be greatly influenced by reproductive success, average age of herd, and genetic potential within the environment. Productivity is influenced by cow age with calf weaning weight, increasing from 2 to 5 yr of age in dams. With that in mind, increasing average age of the cowherd has the potential to increase cow/calf profitability. Culling cows before 5 yr of age negatively impacts production efficiency due to decreased calf weaning weight in younger cows and subsequently, increase replacement rate and costs. Therefore, reproduction in young cattle is important to overall economic efficiency within the cow herd and a driving factor in longevity. Due to decreased reproduction and offspring performance, young females have previously been considered an economic liability. The effect of increased average cow age within the herd along with increased pregnancy rate of young cows has shown to increase production efficiency by decreasing replacement rates and adding greater production potential with increased calf weaning weights. In young beef cows, partitioning nutrients away from lactational demands allows for nutrients to be utilized for cow growth and reproduction. An increase in selection for milk production has resulted in beef cows undergoing greater nutritional stress during early lactation, which ultimately reduces cowherd reproduction and efficiency. Although a big emphasis is placed on output traits, economic value of reproduction is 5 times greater than growth or maternal output traits in beef cattle. In addition, the value of the added milk production may not fully be captured, due to extensive environments with limited nutrients. Even in environments with greater feed resources, selection for milk production may led to a decrease in reproduction, production efficiency, and cowherd retention rate.

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Optimizing beef production system efficiency requires an understanding of genetic potential suitable for a given production environment. Therefore, the objectives of this retrospective analysis were to determine the influence of cow body weight (BW) adjusted to a common body condition score (BCS) of 5 at weaning influenced cow-calf performance and post-weaning steer and heifer progeny performance. Data were collected at the Gudmundsen Sandhills Laboratory, Whitman, NE, on crossbred, mature cows (n = 1,715) from 2005 to 2017. Cow BCS at calving, pre-breeding, and weaning were positively associated (P < 0.01) with greater cow BW. Increasing cow BW was positively associated (P < 0.01) with the percent of cows that conceived during a 45-d breeding season. For every additional 100-kg increase in cow BW, calf BW increased (P < 0.01) at birth (2.70 kg) and adjusted 205-d weaning BW (14.76 kg). Calf pre-weaning average daily gain (ADG) increased (P < 0.01) 0.06 kg/d for every additional 100-kg increase in cow BW. Heifer progeny BW increased (P < 0.01) post-weaning with every addition 100-kg increase in dam BW. Dam BW did not influence (P ≥ 0.11) heifer puberty status prior to breeding, overall pregnancy rates, or the percent of heifers calving in the first 21-d of the calving season. Steer initial feedlot BW (7.20 kg¬), reimplant BW (10.47 kg), and final BW (10.29 kg) increased (P □ 0.01) for every additional 100-kg increase in dam BW. However, steer feedlot ADG was not influenced (P > 0.67) by dam BW. Hot carcass weights of steers were increased (6.48 kg; P = 0.01) with every additional 100-kg increase in cow BW. In a hypothetical model using the regression coefficients from this study, total output (calf weaning and cull cow BW) would be 6,352 kg greater utilizing a 454 kg cowherd compared with a 554 kg cowherd. Overall, larger sized-cows within this herd and production system of the current study had increased reproductive performance and offspring BW; however, total production output and economic returns would be potentially greater when utilizing smaller-sized cows.

Optimizing reproductive efficiency is crucial in sustaining a successful cattle operation. However, optimizing reproductive performance in young range beef cows is often not captured due to an inability to meet the increased physiological demands. The objective of this study was to determine the impact of feed additives on reproductive performance, cow body weight (BW), body condition score (BCS), and calf growth in young, range beef cows. Data were collected from 2- and 3-year-old range cows (n = 189) from the March-calving herd at the University of Nebraska Gudmundsen Sandhills Laboratory (GSL) located near Whitman, NE over a three-year period (2019-2021). Cows were individually supplemented 908 g/d with one of two 30% crude protein supplement treatments with the addition of either: 1) 160 mg·cow-1·d-1 of rumensin (MON; Elanco Animal Health) or 2) 40 g·cow-1·d-1 of propionate salt (CAP; NutroCal 100; Kemin Animal Nutrition and Health). Supplementation was initiated approximately 7 d after calving and continued for an average of 70 d. Cow BW and BCS were collected weekly from calving to the start of breeding and then again at weaning. On approximately d 60 postpartum, milk production was measured by a modified weigh-suckle-weight technique. Cows were exposed to fertile bulls for a 45-d breeding season starting in June of each year. Cow BW (P ≥ 0.19) and BCS (P ≥ 0.11) were not affected by postpartum supplementation during the study. However, cows receiving CAP did lose more BW (P = 0.04; -7 vs -2 kg for CAP and MON; respectively) from calving to breeding than their counterpart. Calf BW at birth, weaning, or 205-d weight were not impacted (P ≥ 0.68) by the postpartum supplementation strategy. Twenty-four-hour milk production and milk components (fat, solids-non-fat, urea nitrogen) were not influenced (P > 0.21) by postpartum supplementation strategy. However, cows receiving CAP supplement had an increase (P = 0.04; 5.40 vs 5.31% for CAP and MON; respectively) in milk lactose percentage and tended (P = 0.06; 2.56 vs 2.68% for CAP and MON; respectively) to have lower milk protein percentage than their counterpart. Cows receiving CAP supplementation had an increase (P = 0.04; 89 vs 80% for CAP and MON; respectively) in overall pregnancy rate. This study implies that young postpartum cows fed additional glucogenic precursors in the form of propionate salts may increase reproductive efficiency without impacting a change in body weight or body condition score.