Calf Weaning Weight Research Articles

57 Relationship between Proportion ofBos indicus Genetics of Dams and Calf Performance from a 31-Year Multibreed Herd Dataset

Abstract This is a 31-year retrospective cohort study aiming to evaluate the relationship between the proportion of B. indicus genetics of crossbred dams and the weaning weight of their calves. Our hypothesis was that crossbred dams with intermediate degree of B. indicus genetics wean heavier calves than those with low-to-high degree of B. indicus genetics at the subtropical condition. The cow-calf pairs (n = 4,901) were in six evenly distributed breed groups according to the proportion of Brahman: G0–19%, G21–34%, 38%, G41–59%; G63–78% and G81–100%. Dams reared contemporaneously were undergone to controlled breeding seasons where the six breed groups of dams and sires were reciprocally mated. Non-adjusted and 205d-adjusted weaning weight of calves were considered as dependent variables and analyzed using MIXED procedure of SAS 9.4. The following independent variables were included in the model as fixed effects: parity category order (primiparous, secundiparous and pluriparous), calving period (0-30d, 31-60d, 61-90d and 91-120d), gender of calf (male or female) and breed group. Year was included as a random effect. All possible interactions were tested and only those with P < 0.20 remained in the final model. Most of all, for the non-adjusted weaning weight, the breed group effect (P < 0.001) varied according to the calving period. Dams calving after 30d of calving season weaned the lightest calves. However, the magnitude of such losses was variable within breed groups. Calves from G0-19% and G81-100% of dams were the most and least impacted by calving period, respectively. The difference on weaning weight between calves born at 0-30d and 91-120d was 60kg for G0-19% of dams and 30kg for G81-100% of dams. For every other breed group, this difference ranged from 45kg to 55kg. In spite of such interaction effect, calves from G0-19% and G81-100% of dams were lighter (230.4 and 225.0 kg, respectively; SEM: 3.4) than any other breed group (238.3 to 242.5 kg). For the 205d-adjusted weaning weight, there was a breed group effect (P < 0.001), regardless of calving period. Lighter calves were still weaned from G0-19% and G81-100% of dams (214.9 and 206.5 kg, respectively, SEM: 2.8) compared with any other breed group (223.4 to 227.6 kg). Thus, crossbred dams with intermediate degree of B. indicus genetics weaned the heaviest calves, probably as result of outbreeding enhancement provided by the adaptability of B. indicus to the tropics and productivity of B. taurus.

Supplementing Ca salts of soybean oil via low-moisture molasses-based blocks to improve reproductive performance and overall productivity of beef cows

This experiment evaluated reproductive and productive responses of beef cows receiving self-fed low-moisture blocks (LMB) enriched or not with Ca salts of soybean oil (CSSO) throughout the breeding season. Non-pregnant, suckled multiparous Angus-influenced cows were assigned to a fixed-time artificial insemination (AI) protocol (day −10 to 0) followed by natural service (day 15–70). Cows were managed in 12 groups (46 ± 4 cows/group) maintained in individual pastures, and groups received LMB enriched with 25 % (as-fed basis) of CSSO or ground corn (CON) from day − 10 to 100. Both treatments were designed to yield a daily LMB intake of 0.454 kg/cow (as-fed basis). Cows receiving CSSO had greater (P < 0.01) mean concentrations of ω-6 fatty acids in plasma samples collected on days 0 and 55. Cows receiving CSSO had greater (P = 0.05) pregnancy rate to fixed-time AI (67.2 vs. 59.3 %), whereas final pregnancy rate did not differ (P = 0.92) between treatments. Pregnancy loss was less (P = 0.03) in CSSO cows (4.50 vs. 9.04 %), which also calved earlier during the calving season (treatment × week; P = 0.04). Weaning rate tended to be greater (P = 0.09) in CSSO (84.8 vs. 79.4 %), although calf weaning age and weight did not differ (P ≥ 0.72) between treatments. Kilos of calf weaned/cow exposed was greater (P = 0.04) in CSSO cows (234 vs. 215 kg). Therefore, supplementing CSSO to beef cows via LMB during the breeding season improved their reproductive and overall productivity during a cow-calf cycle.

Evaluation of Nguni cattle performance from communal property associations and private ownership types across three ecological zones of Mpumalanga province, South Africa

Nguni cattle in South Africa are diminishing at the expense of exotic breeds and crossbreeds. Therefore, the Industrial Development Corporation and Mpumalanga Province Department of Agriculture adopted the Nguni cattle conservation project. Herds of 30 heifers and a bull were allocated to 34 communal property associations (CPAs) and 40 private farms. This study aimed to evaluate growth and reproductive performance across three ecological zones and two ownership patterns. Nine CPAs and nine private farms were sampled. Age at first calving, conception, calving, and weaning rates were determined from production records, while calf birth and weaning weights were digitally measured. Data was analyzed using two-way analysis of variance (ANOVA) with Tukey’s honestly significant difference (HSD) used for mean separation. Significant differences were observed across ecological zones for age at first calving, weaning rate, and birth and weaning weights (p &lt; 0.05). Concerning age at first calving, the Midveld ecological zone performed best (24 months) for both ownership types compared to the Highveld (28.09 months private, 26.00 CPA) and Lowveld (28.35 months for both ownership types). Highveld performed higher on birth weight (25.35 kg) and weaning rate for private (93%) and CPA (80%). Lower birth weights were observed in both ownership types in Midveld (22.17 kg). The Lowveld zone had a higher birth weight (26.80 kg) in CPA. Higher weaning weights were observed in private ownership of Highveld (190.16 kg) and the lowest (160.39 kg) in the Midveld zone. CPAs in Highveld had higher weaning weights (187.55kg) than in Midveld (167.50 kg). The results suggest that Nguni cattle respond differently in the various ecological zones of Mpumalanga Province.

Potentiality of Growth Traits for Selection to Improve Productivity in Nilotic Cattle

Selection for traits of economic importance is crucial for improving productivity and reproductivity in livestock, including cattle. We investigated the prospects of using growth traits; viz: live-body weight (BW), absolute growth rate (AGR), relative growth rate (RGR), absolute maturing rate (AMR), and Kleiber ratio (KR) as bases for selection in Nilotic cattle, by examining the phenotypic correlations among these traits, using 125 male and 136 female calves reared under traditional husbandry system. In the experimental procedure, the heart girth (HG) and body length (BL) of each calf was measured at birth, and at the age of 2, 4, 6, 8, 10, 12, 14, and 16 months; then the BW at each age was derived, and used for estimating AGR, RGR, AMR, KR, and dry matter intake for maintenance (DMIm). AGR, RGR, AMR, or KR was calculated from 0~8 months (AGRα, RGRα, AMRα, KRα), 8~12 months (AGRβ, RGRβ, AMRβ, KRβ), and 12~16 months (AGRγ, RGRγ, AMRγ, KRγ). Phenotypic correlations were determined using the Pearson's correlation method. The results revealed that, BW, AGR, RGR, AMR, KR, and DMIm were inter-correlated. In particular, calf weaning weight (CWW at 8 months), and post-weaning AGRβ, RGRβ, AMRβ, and KRβ (all at 8~12 months` interval) were positively correlated among themselves and with post-weaning BW, but negatively correlated with birth weight and DMIm, and thus, considered the most appropriate selection indices in Nilotic cattle, since these would decrease calf birth weight, thereby reducing dystocia incidences, and increase post-weaning growth, with less DMIm. These results provide the first evidence for possible selection using growth traits to improve productive efficiency in Nilotic cattle.

Environmental stress during the last trimester of gestation in pregnant cows and its effect on offspring growth performance and response to glucose and adrenocorticotropic hormone.

Winter and spring precipitation are predicted to increase in the Midwest region of the United States, causing muddy conditions. In a previous experiment, Angus cows (8 per treatment) were paired based on initial body weight (BW) and one cow from each pair was randomly allocated to either the mud or control treatment. Though cows consumed the same amount of dry matter, cows in the mud treatment weighed 37.4 kg less than cows in the control treatment by day 269 of gestation. The objective of this experiment was to evaluate developmental programming effects of steers born to cows in the mud treatment (MUD; n = 7) or the control treatment (CON; n = 6). Steers were weighed at birth and then weekly from approximately 56 d of age until weaning and were subjected to a glucose tolerance test (GTT) and adrenocorticotropic hormone (ACTH) challenge after weaning. Steers were then placed in the feedlot for an 84-d growing phase and were weighed weekly and 12th rib back fat (BF) and ribeye area (REA) were imaged every 28 d using ultrasonography. Data were analyzed as a randomized complete block design with repeated measurements when appropriate (SAS 9.4). Although there was a 37.4 kg decrease in BW of cows by the end of gestation, there was no evidence of a pen treatment effect on calf birth weight (P = 0.60) or weaning weight (P = 0.99). Additionally, there was no evidence of a pen treatment × day effect for steer BW from birth to weaning (P = 0.67) or growing phase BW (P = 0.60). There was evidence of a treatment × day of growing phase effect (P = 0.02) for BF, such that CON steers had greater BF on day 28 of the growing phase; however, there was no evidence of a treatment × day effect for REA (P = 0.20). Furthermore, there was no evidence of a pen treatment effect for the growing phase average daily gain (P = 0.74), dry matter intake (P = 0.65), gain:feed (P = 0.48), plasma glucose concentration (P = 0.67) or plasma insulin concentration (P = 0.61) in response to the GTT, or plasma cortisol concentration in response to the ACTH challenge (P = 0.51). These results indicate that while mud increased net energy requirements for cows in the MUD treatment, there were no subsequent effects observed for steer BW, gain:feed, or response to glucose and ACTH during the growing phase.

Effects of prenatal and postnatal melatonin supplementation on overall performance, male reproductive performance, and testicular hemodynamics in beef cattle.

Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of prenatal and postnatal melatonin supplementation on overall calf performance and dam milking traits in relation to calves, molecular factors involved in growth and metabolism of calves, along with testicular physiology and fertility traits in subsequent bulls. At day 190, 220 and 250 of gestation, dams (n = 60) were administered either 2 subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves were blocked based on prenatal treatment and sex. Calves received either melatonin implants (posMEL) or none (posCON) on day 0, 30, and 60 of age. At day 60 of lactation, a subset of dams (n= 32) were selected based on age, weight and calf sex for milk collection and analysis. At weaning, (day 210 postnatally) calf weight, morphometric data, liver samples, and loin samples were collected. At 12 months of age, bull (n = 30) scrotal circumference, scrotal temperature, and testicular artery measurements were recorded. Milk yield and fat percent from dams tended to decrease in the preMEL group (P < 0.07) compared with preCON group. Prenatal melatonin administration did not affect (P = 0.95) calf birth weight and similarly calf weaning weight was unaffected (P < 0.10) by prenatal or postnatal melatonin supplementation. Blood analysis demonstrated that plasma concentrations of melatonin were not different (P = 0.12) in dams; however, an increase (P < 0.001) in plasma concentrations of melatonin was observed in posMEL versus posCON calves. A tendency (P < 0.10) for decreased MYF5 and MYOD1 expression in loin muscle was observed in the posMEL calves. Prenatal and postnatal melatonin administration did not affect subsequent bull scrotal measurements or testicular hemodynamics (P ≥ 0.14). Administering supplemental melatonin via implants during the prenatal and postnatal phase did not alter performance characteristics in offspring. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature might have attributed to a lack of differences in melatonin levels during the prenatal phase. In the postnatal period, the level of developmental plasticity appears to be too low for melatonin properties to be effective.

Effect of creep feeding with rice bran and temporary weaning on cow-calf performance.

This study was conducted to investigate if calvessupplemented with rice bran in a creep feeding (CF)system associated with temporary weaning (TW) affects the performance of the cow-calf pair grazing natural grasslands during summer. Two experiments were performedusing 275 cow-calf pairs of British breeds and their crosses of different parities (primiparous [n = 188]in Experiment 1 and multiparous [n = 87] in Experiment 2). In both experiments, the factors evaluated were: (1) supplementation of calves with rice bran using CF: yes (+CF) or no (-CF); (2) TW for 14 days using nose plates: yes (+TW) or no (-TW). Four experimental groups were formed in both experiments: -CF - TW, -CF + TW,+CF - TWand +CF + TW. TW decreased the average daily weight gain and live weight of calves independently of the age of their mothers. The use of CF decreased both of these parameters in calves born to primiparous cows, and there was no response in the case of calves born to multiparous cows. A greater proportion of primiparous cows that received +CF conceived in the first 21 days of mating (+CF - TW = 63.5% and +CF + TW = 50%) than the other groups. The final pregnancy rate was similar among groups in both experiments. In conclusion, TW decreased the average daily weight gain and weaning weight of calves. Supplementation of calves born to primiparous cows with rice bran decreased their daily weight gain during the period of TW and their weaning weight, but their dams were conceived earlier.

Evaluation of a rumen modifier to limit pellet intake in beef brood cows

Winter supplementation of gestating beef cows is often necessary to ensure energy and protein requirements remain satisfied. However, it is difficult to prevent over- or under-consumption by individual animals fed in a group. The objective of this study was to evaluate the intake limiting effects of 3 levels of tea saponin (TS) on pelleted feed consumption when compared with a TS-free control treatment. Commercial beef cows in late gestation (n = 24) were allocated to 1 of 4 treatments delivered via a pelleted feed supplement: 0% (A), 0.16% (B), 0.32% (C), or 0.64% (D) TS on a dry matter basis. Cows were assigned so that initial mean body weights and body condition scores were similar among treatment groups. Supplement was delivered once daily via Calan gates at a rate of 2.5% of BW for 42 days. Refusals were collected daily to calculate intake. Treatment differences were observed for pellet DMI, cow BW, and cow BCS (P &amp;lt; 0.0001). Cow hay intake, calf birth weight, and calf weaning weight were unaffected by treatment (P &amp;gt; 0.05). Dry matter intake of pellets as a percent of BW (DMIBW) was significantly different for all treatments (P &amp;lt; 0.0001) with intake declining as TS content increased. Considerable variability in DMIBW of all treatments was observed from day 0 to 15 but intakes plateaued between 1.75 and 2.5% DMIBW for the remainder of the trial with Treatment D intake remaining noticeably lower than the other treatments. Treatment D was found to be successful at limiting pellet intake to an average DMIBW of 1.51%. This study concluded that short-term pellet intake can be limited by inclusion of TS, highlighting it as a potential intake limiter product for beef cattle producers.

PSIII-5 Late-Breaking: Genetic Evaluation of Energy Efficiency in Bos taurus Cows Classified by Residual Feed Intake

Abstract Genetic selection for efficiency traits is essential to improve the profitability and sustainability of livestock operations. Inefficient metabolism and energy production in animal physiology leads to excess feed consumption, resulting in higher feed costs. The objective of this study was to investigate hepatic gene expression in mature Angus-influenced cows that were classified as low or high RFI as heifers and had either a low or high ratio of calf weaning weight to mature body weight at weaning. Eleven cows were selected from the Northern Agricultural Research Center (NARC) research herd. Cows were ranked as efficient (n = 5) or inefficient (n = 6) based on their low or high residual feed intake (RFI) measured as a growing heifer and then by the ratio of calf weaning weight by mature body weight. Animals were partitioned from the bottom quartile with low RFI as a heifer and weaned with a higher proportion of the calf were classified as efficient, and animals from the top quartile with a high RFI as a heifer and a lower ratio of the calf to body weight were classified as inefficient. Liver samples were collected by needle biopsy approximately one week after weaning and snap frozen. The liver gene expression profile was measured using RNAseq. Two cows' data were not reported, one from each group, as RNA quality prevented sequencing (Efficient n = 4 and Inefficient n = 5). Over 5 million reads were mapped for each sample and were aligned to BTau 4.6.1 reference sequence using HISAT2. Differentially expressed genes were determined using the DEseq2 R package using a model based on the negative binomial distribution, and p-values were adjusted using the Benjamini-Hochberg approach. A corrected P-value of less than 0.05 defined a differentially expressed gene. Gene lists were used for gene ontology and KEGG pathway enrichment using clusterProfiler software. One novel gene was significantly differentially expressed with higher expression in the efficient group. However, no annotation currently exists for this gene. Additionally, the KEGG pathway biosynthesis of unsaturated fatty acids was significantly enriched (P &amp;lt; 0.05) with the following differentially expressed genes SCD, FADS1/2, ELOVL6, and HACD2, all being down-regulated in inefficient cows. The enrichment of this pathway is most functionally relevant, as it indicates that local liver changes could directly affect the efficient metabolism and biosynthesis of fatty acids. With encouraging, but limited results, this study provides the groundwork for future study of the heritable mechanisms contributing to the generation of more energy-efficient cows.

PSXII-7 Evaluation of Winter Hair Coat Shedding on cow and Calf Performance in Crossbred Angus Cattle in Arkansas

Abstract The objective of this study was to assess the effect of winter hair coat shedding for crossbred Angus dams (n = 544) on calf birth weights, calf weaning weights (WW), calf adjusted 205-day weaning weights (d205wt), artificial insemination (AI) pregnancy rates, overall pregnancy rates, cow pre-breeding body weights (PBW), cow pre-breeding body condition scores (PBCS) over a two-year collection period. Hair shedding data were collected on fall-calving crossbred cows from March to July using a visual hair shedding score of 1 to 5 was assigned to each cow, with 1 exhibiting 100% shedding of winter coat to 5 exhibiting 0% shedding of winter coat. Month of first shedding (MFS) was determined once a female reached a hair shedding score of ≤ 3 for any given month. Artificial insemination pregnancy and overall pregnancy was determined by rectal ultrasound. Data were analyzed using the MIXED procedure of SAS for calf performance, cow BW, and cow BCS, and the GLIMMIX procedure of SAS for AI pregnancy and overall pregnancy analyses. Statistical significance was declared at P ≤ 0.05 and tendencies declared at 0.05 &amp;lt; P ≤ 0.1. There was no effect of MFS on calf birth weights (P = 0.79), WW (P = 0.12), d205wt (P = 0.28), AI pregnancy (P = 0.76), overall pregnancy (P = 0.80), PBW (P = 0.11), and BCS (P = 0.69). The findings reported in this study indicate that MFS had no effect on cowherd performance during this two-year study in Arkansas; however, there is a need for continuing research to be performed to evaluate the effects of winter hair coat shedding in other environments.

153 Phenotypic Selection of Efficient Beef Cows and Differences in Digestive Physiology

Abstract This study evaluated beef cows identified as having high or low efficiency when managed in extensive systems and whether they differ in terms of digestive physiology. Nine high (HE) and low efficiency (LE) cows were selected from a group of 86 Angus cows using 2 years of selection data. Yearly ranks were assessed based on three weighted criteria: cow rump fat at calving; calving interval; and calf weaning weight. The 18 cows were then ruminally cannulated and used to evaluate their response to high (HQ; 41.0±0.78% NDF), medium-high (MHQ; 56.9±1.17% NDF), moderate (MQ; 62.5±3.40% NDF), and low-quality forage (LQ; 64.3±1.40% NDF) diets using four consecutive 26-d periods where diet quality progressively decreased by period for all cows. There was no phenotype′diet interactions. Start and end BW were 48 and 45 kg less (P&amp;lt; 0.01) and rump fat was thicker for HE than LE cows (P=0.02). Although total DMI did not differ (13.0 kg/d; P=0.93), DMI (%BW) was greater for HE (2.12%) than LE (1.97%, P&amp;lt; 0.01). Ruminal pH, short-chain fatty acid concentration, and the molar proportion of acetate, butyrate, and propionate did not differ. Ruminal digesta weight was 4 kg greater (P=0.04) and the pool sizes of DM (P=0.01), NDF (P=0.03) and undigested NDF (P&amp;lt; 0.01) were greater for LE than HE. Ruminal NDF passage rate was greater for HE than LE cows (3.11 vs. 2.89%/h, P=0.05), but there were no differences for the rate of NDF digestion. Ruminal contraction amplitude (P=0.01) and peak area (P&amp;lt; 0.01) were higher for LE than HE cows. Apparent total tract nutrient digestibility did not differ (P≥0.23). Cows identified as being efficient under an extensive management system have greater DMI as a proportion of BW, less ruminal digesta weight, and greater NDF passage rate but did not differ for total tract digestibility.

79 Effects of Nutrient Restriction During Late Gestation of the First Parity on cow and Calf Performance During the Second Lactation

Abstract Fall-calving Herford-SimAngus heifers were individually fed either 100% (control; CON, n = 10) or 70% (nutrient restricted; NR, n = 12) of NASEM metabolizable energy and metabolizable protein requirements from d 160 of gestation to calving. Postpartum cows were individually fed 100% of energy and protein requirements until d 149 of lactation, then fed tall fescue hay or pasture as a single group through parity 2. Second parity cow performance and calf size were measured at birth, d 30, and d 60 post-calving. Single-quarter colostrum yield was collected pre-suckling. At d 30 and 60 of lactation, 4-hour milk yield was collected. Data were analyzed with the fixed effect of first parity nutritional plane, and calving or breeding date, calf sex, and calf sire (calf measures) were covariates. Milk yield included day and day x treatment (repeated measures). We previously reported that in parity 1, NR reduced (P ≤ 0.04) colostrum and milk yield, calf weaning weight, and dam weaning BCS. From calving to d 60 of parity 2, CON cows had greater (P ≤ 0.008) BCS and greater (P = 0.003) backfat on d 30. Additionally, CON cows had greater (P ≤ 0.002) BW compared with NR at d 30 and 60 of lactation. Calf size was not affected (P ≥ 0.17) by first parity nutritional plane except that cannon length at birth and d 60 tended (P ≤ 0.08) to be longer in CON calves. Colostrum and milk volume and weight were not affected (P ≥ 0.37) by first parity nutritional plane. Milk yield was greater (P ≤ 0.001) at d 30 than d 60. These data indicate that cow BW and energy reserves remained less in parity 2 when heifers experienced late gestational nutrient restriction, but calf size, colostrum yield, and milk yield were unaffected in the second parity.

84 Awardee Talk: Managing Reproduction: A key to Profitability

Abstract In agriculture, the ability to reproduce dictates gross revenue and reproductive success is the culmination of implementation of multiple management practices that optimize the probability the animal will reproduce. About four decades ago, Extension Specialists recognized the need to develop a holistic approach to beef cattle management. Integrated Resource Management (IRM) is a concept developed by the Cooperative Extension Service and the National Cattlemen’s Beef Association and the concept represents a systems approach designed to enhance the competitiveness, efficiency, and profitability of the beef business. My Extension program has focused on enhancing reproductive efficiency, revenue, and profits using IRM concepts and a hands-on approach. Nearly 2,000 farm visits and multiple Extension programs to thousands of producers have demonstrated methods to improve productivity and profitability. Perhaps the most impactful program was the UK IRM Farm Program. This program combined standard educational meetings discussing health, nutrition, genetics, and reproduction with extensive farm visits. Baseline data was obtained from each cooperator and farm goals were ascertained. From these, production plans were developed and implemented with the help of local Extension Agents. At the conclusion of the program, 147 producers from 84 counties with 6,943 cows committed to this program. Data collection and management was central to this project. We obtained gross data from all cooperators and accurate impact data from a subset of these producers. Integrated, organized management decreased the length of the calving season, increased calving percent, weaning percent, weaning weight and pounds of calf per cow exposed. Revenue was increased by 34% on average with a range of 25-200%. During this project, we recognized the need for a new data collection and management application and developed X10D (pronounced “extend”). An IRM approach making data driven decisions is a key to increasing revenue and enhancing profitability in beef cow-calf operations.

PSVIII-B-4 Differences in Bull Prolificacy and Offspring Body Performance in Western Canadian Multi-Sire Commercial Herds

Abstract Beef cattle producers employing multi-sire natural mating systems expect superior breeding and production performance from the bulls. The bulls that sire more healthy calves are more economical considering that the annual maintenance cost for each bull could exceed $2000. Industry benchmarks on bull prolificacy and the production performance of their offspring will enable producers to make better selection and culling decisions. This 3-yr study evaluated 2,130 calves from 62 bulls and 1, 869 cows to assess bull prolificacy and calf production performance in multi-sire breeding pastures – VS (VS1, VS2), OS, CF, KF, DIF, and DEF across Alberta Canada. Calves were matched to bulls using DNA paternity analysis. Prolificacy was assessed among bulls engaged in breeding activities year-over-year. Percentage calves assigned to each sire from sire-progeny matches were assessed within sites over consecutive years (VS1: 11.5 - 46.34%, VS2: 4 - 75%, OS: 2 - 17%, CF: 6 - 33%, KF: 5 - 38%, DIF: 3 - 26%, DEF: 16 - 62%). The differences in body and growth performance of calves were analyzed with linear mixed models. The average birth weight of calves varied by sires (p &amp;lt; 0.05) in VS1 (39.92kg – 42.74kg; P &amp;lt; 0.05), OS (34.09kg–39.49kg), CF (35.72-40.27kg) but not in VS2 (36.35 – 38.02kg; P &amp;gt; 0.05). Similarly, the average calf weaning weights among sires did not differ in VS1 (309.44 – 316.77kg; P = 0.33) but were different (P &amp;lt; 0.05) in OS (219.25 - 236.36kg), CF (216 -243 kg) and KF (178 - 232kg). Differences were also observed in calves' average daily body gain among sires in VS1 (0.93 – 1.14 kg d-1; P &amp;lt; 0.0001). Verifying the sires of calves in multi-sire herds will enable beef producers to make effective management and economic decisions. Measuring the production performance of calves from different bulls is important for the beef industry's profitability and sustainability.

Social organization and fitness response in grazing beef cows – Understanding through interactions and activity measuring

According to behavioural ecology theory, sociality evolves when the benefits of close association with conspecifics exceed the costs. Still, even when sociality evolves, the balance between costs and benefits differentiates amongst individuals in a group where each individual is selected to maximize its own fitness. In this study we aim to find correlations between fitness and social interactions and activity, and to test whether one of the prevailing social behaviour models, dominance hierarchy and self-organization, can describe social behaviour in a large group of grazing cows. Direct observations and drone video recordings were carried out in a herd of 130 ± 12 cows during two consecutive summers in a typical Mediterranean pasture in northern Israel. Observations' frequency was two to three weekly, lasting 4 ± 2 h each, during resting, grazing and feeding times. Agonistic interactions, allogrooming and grouping were recorded. Locomotion activity was monitored continuously by electronic pedometers. We calculated dominance probability, using the "Percolation and conductance" network approach whereby multiple indirect dominance pathways in the network are used to fill in missing data in the win/loss matrix. Dominance probability calculated was ambiguous (inconsistent dominance direction) with resulting average dominance index of 0.56 ± 0.029. Proxies for fitness were calving-to-conception interval and calf weaning weight. Calves were not considered as part of the group. Multiple regression analyses showed a positive effect of grouping and negative effect of oscillating grazing activity pattern on fitness response (p = 0.012; p = 0.01 for calving to conception interval and weaning weight respectively). Oscillating activity pattern was expressed in high Coefficient of Variance value of stepping activity. We suggest that in a large group of free grazing beef cows, social organization does not result from dominance hierarchy, and is better described by self-organizing systems hypothesis. Herd schedule and activity patterns were repetitive, but individuals' schedule within it was not. Individuals' morning grazing activity patterns were repetitive, but other daily hours' activity was not and individuals' nearest neighbours were changing continuously between daily activity sessions.

Energy restriction and housing of pregnant beef heifers in mud decreases body weight and conceptus free live weight.

Average temperatures in the Midwest, USA are predicted to increase 2–9°C by the end of the century; resulting in muddy pastures for spring calving beef heifers as they enter late gestation. The objective of this study was to evaluate the effects of muddy conditions on heifer body weight (BW), body condition score (BCS), conceptus free live weight (CFLW), and fetal growth when heifers were energy restricted during late gestation. Eighteen Angus heifers (n = 9/treatment) were paired based on initial BW. One heifer from each BW pair was randomly allocated to either the mud (MUD) or control (CON) treatment on day 196 of gestation. Pens in the CON treatment were bedded with wood chips, while pens in the MUD treatment were filled with mud (average depth of 19.5 ± 7.9 cm). Heifers were housed individually and fed the same diet that consisted of a limit-fed total mixed ration from day 196 to 266 of gestation that was formulated to meet 66% of the net energy for maintenance, growth, and gestation requirements. Requirements and the amount of the diet offered were adjusted weekly, and heifers were weighed and sampled for blood metabolites weekly. Data were analyzed as a randomized complete block design with repeated measurements. There was a treatment × day of gestation interaction, such that heifers had similar BW, BCS, and CFLW on day 196 of gestation. By day 266 of gestation; however, heifers in the MUD treatment weighed 43.5 kg less (P < 0.01) and were 1.8 BCS units less (P < 0.01) than heifers in the CON treatment. This is further supported by the treatment × day effects we observed for back fat (BF) and rump fat (RF) thickness, such that the MUD heifers had less BF (P = 0.02) and RF (P < 0.01) by day 266 of gestation. There was a marginally significant difference for gestation length (P = 0.06), such that heifers in the MUD treatment calved approximately 3.1 days before the heifers in the CON treatment. Though heifers in the MUD treatment decreased their BW and CFLW during the treatment period, we did not observe a difference in calf birth weight (P = 0.34), calf plasma IgG concentration (P = 0.37), or calf weaning weight (P = 0.63). Despite heifers in the MUD treatment having greater BW, CFLW, and BCS losses compared with the heifers in the CON treatment, the heifers in the MUD treatment seemed to prioritize fetal growth, as they mobilized their body tissues to meet the energetic demands of pregnancy.

Influence of Heifer Post-Weaning Voluntary Feed Intake Classification on Lifetime Productivity in Black Angus Beef Females.

Simple SummaryReplacement beef heifers represent the future of a herd for many cow-calf producers. Producers must invest significant resources into the development of these females as well as consider their maintenance and production costs as mature cows. As a result, selection focuses on replacement heifers that are more efficient in limited nutrition forage base systems. Producers can improve lifetime productivity by ensuring their replacements are of an ideal age and size to be bred as a 2-yr old. Selection criteria may include reproductive ability and breeding history, milk production, and weaning/yearling weights. The ability to select replacement females that are more efficient without negatively affecting overall productivity will help to decreased inputs and alleviate the need for additional expenses such as supplemental feed resources. This study evaluated heifer post-weaning voluntary feed intake (g/kg BW) classification on performance and reproductive measures, as well as impacts on lifetime productivity of 519 commercial Angus beef females. Heifer post-weaning voluntary feed intake (g/kg BW) was calculated over 80 test days following weaning using GrowSafe units. Heifers were categorized based on voluntary feed intake (g/kg BW) as either low (<−0.50 SD from the mean), average (±0.50 SD from the mean), or high (>0.50 SD from the mean) within year. Cow body weight (BW) and body condition score (BCS) at breeding displayed an age effect (p < 0.001), with 2- and 3-year-old cows having lighter BW and lower BCS than 4-yr-old and older cows. Cow BW at weaning showed significance for age and intake (p < 0.001) with younger cows being lighter than older cows, while low intake classified females had greater BW at weaning compared to average and high intake females. Additionally, calf 205-d weights and calf weaning weights (p < 0.01) were significant for age with calves born from older cows weighing more than younger cows. Weaning weight ratio displayed a linear increase with increasing intake classification (p < 0.01). Heifer yearling BW was significant for intake (p < 0.01) with low and average intake heifer classifications having greater heifer yearling BW than cows that had high intake classification as a heifer. Age and intake classification did not impact (p ≥ 0.22) pregnancy status or AI conception. In summary, heifer post-weaning feed intake classification had only minor impacts compared to age effects on lifetime productivity of Angus beef females.

Can early weaning calves of first-calf heifers improve long-term herd and financial performance in a vertically integrated beef production system? A study application using system dynamics

The objectives were to (a) evaluate whether marginal reproductive gains from early weaning (EW) calves of first-calf replacement heifers extend throughout the animal’s productive life and (b) compare via cost–benefit analysis EW with conventional weaning (CW) practices on a vertically integrated ranch in Florida, USA. A system dynamics model was developed to evaluate CW versus EW of calves from replacement heifers that calve in the first 21 or 42 d of the calving season. A combination of sensitivity analyses and deterministic management tests (EW vs. CW and 21- vs. 42-d calving seasons) were simulated and compared across a range of 18 production and financial metrics, including net present value, over the useful life of one generation of replacement heifers. We hypothesized that EW calves from replacement heifers would improve reproductive performance, resulting in greater total calves produced and, therefore, improved cow-calf and whole-system profitability. The 42-d calving criteria for EW created significant production and financial gains and outperformed the 21-d calving criteria. Counterintuitively, these gains did not arise in the cow-calf or feedyard segments (which saw financial declines) but in the stocker segment due to more efficient livestock gains facilitated by lower weaning weights of incoming calves. Sensitivity analyses corroborated these trade-offs. Feedyard sale price (i.e., value received for finished cattle) was the most influential factor influencing whole-system profitability. Trade-offs and incentives between enterprises may provide misleading feedback and mask changes that improve the system as a whole (e.g., EW reduced calf weaning weights and reinforced the reproductive performance pressure on management; gains at the stocker segment may mask EW benefits at the cow-calf level, making the cow-calf enterprise more reliant on short-term adjustments, a behavior known as “shifting the burden”).

Effect of temporary weaning and creep feeding on calf growth and the reproductive efficiency of their Hereford dams.

ObjectiveThe objective was to test if creep feeding (CF) improves the average daily gain (ADG) and weaning weight of calves submitted to temporary weaning (TW) and if the combination of CF and TW improves conception and pregnancy rates of cows.MethodsPrimiparous (n = 74) and primiparous and multiparous (n = 104) cows grazing native grasslands were used in experiment 1 and 2; respectively. The experimental design was in plots divided into complete random blocks with two replications. The CF was the big plot and TW the small plot, thus four experimental groups were formed: i) −CF−TW (n = 21 and 27); ii) −CF+TW (n = 16 and 24); iii) +CF−TW (n = 20 and 26); iv) +CF+TW (n = 17 and 27) with cow-calf pairs for experiments 1 and 2; respectively. Nose plate application for TW had a duration of 14 and 15 days for experiment 1 and 2: respectively. In experiment 1, calves were fed at 1% of live weight for 112 days using a commercial supplement with 18.4% crude protein. In experiment 2, the supplementation lasted 98 days, and was carried out with corn dried distillers grains with soluble (DDGS) at 40% of the potential intake on a daily basis.ResultsThe TW reduced ADG during the TW period and the following 14 days, but the negative effect of TW was maintained until the final weaning only in experiment 2. The CF increased ADG during TW period in both experiments. The TW promoted an earlier conception of the dams (12 days in −CF treatment and 19 days in +CF treatment, p<0.01) and CF increased pregnancy rate in experiment 1, being the effects not consistent between experiments.ConclusionThe CF consistently promoted an increase in ADG during the period of TW and increased final weaning weight of calves, therefore it is economically viable.

Evaluation of Strategies to Improve the Environmental and Economic Sustainability of Cow-Calf Production Systems.

Simple SummaryBeef cattle have a significant contribution to greenhouse gas emissions globally, but they have a unique ability to digest plant material that is inedible for humans, thus producing human food from grasslands and rangelands. Additionally, many people around the world depend upon cattle ranching of grasslands and rangelands for their livelihoods. Identifying the strategies likely to have the largest impact on greenhouse gas emissions while improving or maintaining economic returns is necessary to guide future research. The goal of the current study was to evaluate four potential strategies for improving the environmental and economic sustainability of cow–calf production. The four strategies included (1) decreasing the feed required for maintenance, thus increasing the feed available for growth, (2) decreasing the time for cows to rebreed after calving, (3) increasing the digestibility of pasture grass, and (4) increasing the yield of pasture grass. A computer simulation model of a cow herd in Kansas, U.S.A., was modified to create variation in the four strategies. Decreasing the feed required for maintenance improved both environmental and economic sustainability, and increasing the yield of pasture grass improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow–calf production systems.Grazing cow–calf production systems account for 60 to 70% of the greenhouse gas emissions of U.S. beef production. The objective of this analysis was to evaluate the importance of management strategies (cow maintenance energy requirements, reproductive efficiency, forage nutritive value, and forage yield) on the sustainability of cow–calf production systems using a sensitivity analysis in a production systems model. The Beef Cattle Systems Model was used to simulate a cow–calf production system in the Kansas Flint Hills using Angus genetics over a 24 year time period. The model was modified to create variation among cow herds in the base net energy for the maintenance requirement (NEm_Req), postpartum interval (PPI), grazed forage digestibility (Forage_TDN), and forage yield per hectare (Forage_Yield). The model was run for 1000 iterations/herds of a 100-cow herd. A stepwise regression analysis in conjunction with standardized regression analysis was used to identify important predictors of an indicator of greenhouse gas (GHG) emission intensity, dry matter intake per kilogram weaned, and two indicators of economic sustainability, winter feed use and returns over variable costs, using R statistical software. The most important predictor of DMI per kilogram weaned was calf weaning weight followed by NEm_Req, whereas returns over variable costs were primarily influenced by kilograms weaned per cow exposed and total purchased feed (supplement + winter feed), which were strongly influenced by NEm_Req and Forage_Yield, respectively. In conclusion, decreasing the net energy required for maintenance improved both economic and environmental sustainability, and increasing forage yield and length of the grazing season improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow–calf production systems.