S. H. Cox

Metabolizable protein supply while grazing dormant winter forage during heifer development alters pregnancy and subsequent in-herd retention rate

Two studies were conducted to evaluate the effects of postweaning management of British crossbred heifers on growth and reproduction. In Exp. 1, 239 spring-born, crossbred heifers were stratified by weaning BW (234 ± 1 kg) and allotted randomly to 1 of 2 treatments. Treatments were fed at a rate equivalent to 1.14 kg/d while grazing dormant forage (6.5% CP and 80% NDF, DM basis) and were 1) 36% CP containing 36% RUP (36RUP) or 2) 36% CP containing 50% RUP (50RUP). Supplementation was initiated in February (1995 and 1996) or November (1997 and 1998) and terminated at the onset of breeding season (mid May). Heifers were weighed monthly up to breeding and again at time of palpation. After timed AI, heifers were exposed to breeding bulls for 42 ± 8 d. In Exp. 2, 191 spring-born, crossbred heifers were stratified by weaning BW to treatments. Heifer development treatments were 1) pasture developed and fed 0.9 kg/day of a 36% CP supplement containing 36% RUP (36RUP), 2) pasture developed and fed 0.9 kg/day of a 36% CP supplement containing 50% RUP (50RUP), and 3) corn silage-based growing diet in a drylot (DRYLOT). Heifers receiving 36RUP and 50RUP treatments were developed on dormant forage. Treatments started in February and ended at the onset of a 45-d breeding season in May. Heifer BW and hip height were taken monthly from initiation of supplementation until breeding and at pregnancy diagnosis. In Exp. 1, BW was not different (P ≥ 0.27) for among treatments at all measurement times. However, 50RUP heifers had greater (P = 0.02; 80 and 67%) pregnancy rates than 36RUP heifers. In Exp. 2, DRYLOT heifers had greater (P < 0.01) BW at breeding than 36RUP or 50RUP developed heifers. However, BW at pregnancy diagnosis was not different (P = 0.24) for between treatments. Pregnancy rates tended to be greater (P = 0.10) for 50RUP heifers than 36RUP and DRYLOT. Net return per heifer was US

Does β-hydroxybutyrate concentration influence conception date in young postpartum range beef cows?

99.71 and

Protein and glucogenic precursor supplementation: A nutritional strategy to increase reproductive and economic output

87.18 greater for 50RUP and 36RUP heifers, respectively, compared with DRYLOT heifers due to differences in pregnancy and development costs. Retention rate after breeding yr 3 and 4 was greatest (P ≤ 0.01) for 50RUP heifers. Thus, increasing the supply of MP by increasing the proportion of RUP in supplements fed to heifers on dormant forage before breeding increased pregnancy rates, cow herd retention, and net return compared with heifers fed in drylot.

Effect of late gestation bodyweight change and condition score on progeny feedlot performance

Cows in negative energy balance after calving often have reduced reproductive performance, which is mediated by metabolic signals. The objective of these studies was to determine the association of serum metabolites, days to first postpartum ovulation, milk production, cow BW change, BCS, and calf performance with conception date in spring-calving 2- and 3-yr-old beef cows grazing native range. In Exp. 1, cows were classified by conception date in a 60-d breeding season as early (EARLY; conceived in first 15 d of breeding) or late conception (LATE; conceived during the last 45 d of breeding). Beginning on d 35 postpartum, blood samples were collected twice per week for serum metabolite analysis and progesterone analysis to estimate days to resumption of estrous cycles. As a chute-side measure of nutrient status and glucose sufficiency, whole-blood β-hydroxybutyrate (BHB) concentrations were measured 14 ± 2 d before breeding. In Exp. 2, cows were classified by subsequent calving date resulting from a 55 ± 2 d breeding season as conceiving either early (EARLY; conceived in first 15 d of breeding) or late (LATE; conceived during the remaining breeding season). Blood samples were collected in 2 periods, 30 ± 4 d before calving and 14 ± 3 d before the initiation of breeding, to determine circulating concentrations of IGF-I and BHB. In Exp. 1, BHB and serum glucose concentrations were less (P ≤ 0.04) in EARLY cows than LATE cows. Serum insulin concentrations were greater (P = 0.03) in EARLY cows relative to LATE cows. Milk production and composition did not differ (P ≥ 0.24) by conception date groups. In Exp. 2, cow age × sample period × conception date interaction (P < 0.01) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows (in greater nutritional plane compared with Exp. 1) regardless of their conception date classification and sampling period. However, precalving serum BHB concentrations were greater (P < 0.01) for LATE than EARLY in 3-yr-old cows with no difference (P = 0.86) at prebreeding. Serum IGF-1 concentrations were greater (P < 0.01) for EARLY cows relative to LATE cows at precalving and prebreeding. This study indicates that blood BHB concentrations during times of metabolic dysfunctions may provide a more sensitive indicator of energy status than body condition, predicting rebreeding competence in young beef cows as measured by interval from calving to conception.

Winter protein management during late gestation alters range cow and steer progeny performance.

Reproductive performance in young beef cows is often compromised due to a mismatch of physiological demands and suboptimal environmental conditions. Studies conducted at the Corona Range and Livestock Research Center from 2000 to 2007 evaluated 3 postpartum supplement strategies that varied in the amount of glucogenic potential (GP) supplied. Reproductive variables, milk production, and serum metabolites were used to assess supplement effectiveness and economics associated with 2- and 3-yr-old beef cows (n = 379) grazing native range. Supplements were individually fed twice/week at 1,135 g/d (2003 to 2004) or 908 g/d (all other years) and provided 1) 327 g of CP, 109 to 118 g of RUP (CON); 2) 327 to 341 g of CP, 142 to 157 g of RUP (RUP); or 3) 327 g of CP, 151 to 173 g of RUP + 40 to 100 g of propionate salt (PS; RUP+PS). Ultimately, total GP for CON, RUP, and RUP+PS was 44 to 47, 57 to 70, and 93 to 141 g, respectively. Blood samples were collected once/week (2000) or twice/week (2001 to 2007) for progesterone analysis to estimate days to resumption of estrus. Cows were exposed to bulls for 60 d or less, and pregnancy was confirmed by rectal palpation at weaning. Days to resumption of estrus after calving decreased linearly (P = 0.02), resulting in an increased pregnancy rate (P = 0.03) with increasing GP. Milk production exhibited a quadratic (P = 0.04) response to increasing GP, with cows fed RUP producing the most amount of milk. However, a linear decrease (P = 0.07) in days from BW nadir to estrus was found with increasing GP. Total kilograms of calf weaned per cow exposed for the supplemental year and subsequent year was increased linearly (P = 0.07) with increased GP. The improvement in pregnancy rate by supplementing RUP+PS resulted in an increase in total revenue of 18% compared with CON-fed cows and 9.5% compared with RUP-fed cows in the subsequent year after supplementation. These data suggest feeding young cows additional GP in the form of PS allows for partitioning of nutrients away from milk production and toward reproduction, allowing for increased profitability by increasing pregnancy rates and decreasing days to resumption of estrus.

Temperament Affects Rangeland Use Patterns and Reproductive Performance of Beef Cows

Inadequate nutrient intake during late gestation can cause cow bodyweight (BW) loss and influence cow reproductive performance and subsequent productivity of steer progeny. Therefore, a 7-year study with a 3 × 3 arrangement of treatments was conducted at Corona Range and Livestock Research Centre, Corona, New Mexico to evaluate the effects of cow BW change and body condition score (BCS) during late gestation on subsequent cow pregnancy rates, progeny steer feedlot performance, and health. Cows were retrospectively classified to 1 of 3 BW change groups: (1) cows that lost BW during late gestation (LOSS; mean –26 ± 2 kg); (2) cows that maintained BW during late gestation (MAIN; mean –1 ± 1 kg); or (3) cows that gained BW during late gestation (GAIN; mean 25 ± 2 kg). Cows were also classified to 1 of 3 BCS groups: BCS of 4 (mean BCS = 4.0 ± 0.02; range 4.0–4.5), 5 (mean BCS = 5.0 ± 0.02; range 5.0–5.5), or 6 (mean BCS = 6.0 ± 0.02; range 6.0–6.5). After weaning each year, steers were preconditioned for 45 days and were received and treated as custom-fed commercial cattle at a feedlot in mid-November. Calf weaning BW, initial feedlot BW, final BW, and hot carcass weight were unaffected (P ≥ 0.22) by dam’s prepartum BW change or BCS. However, steers from GAIN and MAIN tended (P = 0.06) to have increased ADG in the feedlot. Twelfth-rib fat thickness, longissimus muscle area, and days on feed were not influenced (P ≥ 0.18) by late gestation BW change or BCS. Calves from BCS 6 cows tended (P = 0.10) to have greater yield grades at harvest in the feedlot. Percentage of steers grading Choice or greater was increased (P < 0.01) in steers from LOSS cows and cows in BCS 4 during late gestation compared with other groups. These data suggest that modest nutrient restriction during late gestation can have a minimal effect on growth and performance of steer progeny from birth through the finishing phase.

Effects of growth-promoting implants administered during the suckling phase on growth, conception rates, and longevity in replacement beef heifers grazing native range

A 4-yr study was conducted at Corona Range and Livestock Research Center, Corona, NM, to establish if a protein-dense self-fed supplement could substitute for a traditional hand-fed (range cube) supplement that is less protein dense and minimize or maintain cow BW and BCS during late gestation and the subsequent steer progeny feedlot performance, health, and economic viability. Late gestation cows received one of 3 supplementation strategies: 1) 36% CP cottonseed meal base supplement (CSM; positive control) fed 3 times per week, 2) self-fed supplement (SMP) comprising 50% animal protein sources (blood meal and feather meal) and 50% trace mineral package, or 3) brief and intermittent supplementation of CSM based on periods of acute environmental stress (VAR; negative control) by ranch management. Initiation of supplementation varied across years due to changing forage conditions and climatically imposed grazing constraints but always ended approximately 2 wks before calving each year. Across all 4 yr, supplement consumption averaged 0.65, 0.21, and 0.04 kg·head(-1)·d(-1) for CSM, SMP, and VAR, respectively. After weaning, steers were preconditioned for 45 d and were received and treated as custom fed commercial cattle at a feedlot in mid November each year. Cow BW and BCS were not influenced (P ≥ 0.13) by prepartum supplementation; however, the strategy did have an effect on BW and BCS change with cows managed in the VAR group. Cows managed in the VAR group lost the greatest (P < 0.05) amount of BW and BCS whereas no differences were measured between CSM and SMP groups. Prepartum supplementation strategies did not influence (P = 0.98) pregnancy rates. Calf weaning, initial feedlot and final BW, and HCW were unaffected (P ≥ 0.80) by prepartum supplementation of the dam. Steers from dams fed CSM and VAR had a greater percentage treated for sickness than SMP steers (P = 0.03), which resulted in a tendency (P = 0.07) for medicine costs to be greater in steers from CSM and VAR cows. The use of a self-fed package supplement was equally effective as use of a traditional hand-fed, oilseed-based supplement in maintaining BW and BCS during late gestation. In addition, these results imply that although nutrition treatment of cows during the prenatal period had no effect on calf growth performance, calves from cows fed SMP had improved feedlot health.

Supplementation strategy during late gestation alters steer progeny health in the feedlot without affecting cow performance

On the Ground The American beef industry is paying more attention to cattle temperament, but studies examining relationships between temperaments and grazing behavior or animal performance on rangelands are limited. We studied range beef cow temperaments using the behavioral syndromes framework. Cows classified into behavioral type groups on the basis of a suite of correlated behaviors showed contrasting rangeland use patterns and different reproductive efficiency. These differences resulted in temperament-related culling rates over time. We argue that the behavioral syndromes conceptual framework could be a valuable tool to advance current understanding about how cattle temperaments are related to grazing patterns and animal performance on rangeland.

1666 WS Effects of rumen protected arginine supplementation to cows during early or late gestation on progeny glucose tolerance.

© The Author(s) 2018. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com. Transl. Anim. Sci. 2018.2:S180–S184 doi: 10.1093/tas/txy048