Metabolic and hormonal profiles and productive performance in primiparous and multiparous cows grazing different forage allowance in late gestation

The aim of this study was to evaluate two levels of forage allowance (FA) during the prepartum period on metabolic, hormonal, productive, and reproductive variables in primiparous (P) and multiparous (M) beef cows. Six weeks before calving, 40 P and 42 M cows were assigned to two FA (native pastures) treatments until calving (day 0): High (15 kg DM/100 BW; H) and Low (5 kg DM/100 BW; L). After calving all cows were managed together. High FA cows presented greater intake than L cows, while M tended to have greater intake than P cows. Increased herbage allowance in late gestation in beef cows successfully improved forage intake and energy balance reflected in body condition score and metabolic and endocrine markers. Also, high forage allowance increased milk yield (5.4 vs 4.6 kg/d, P < 0.05) and calves daily gain rate during the first two months of age (0.88 vs 0.82 kg/d, P < 0.05) in H respect to L cows. Pregnancy rate was greater in H vs L cows (40 vs 28 %, P < 0,05). The endocrine metabolic response to higher forage allowance depended on parity, as primiparous cows showed a greater imbalance around calving. Moreover, most primiparous cows were not pregnant at the end of the breeding season, consistent with their prolonged anestrous. Multiparous cows had better productive and reproductive performance than primiparous cows, showing that growing cows have a pronounced negative energy balance reflected in most of the evaluated parameters.

A conceptual model of cow-calf systems functioning on native grasslands in a subtropical region

Cow-calf systems utilise grazing of native grasslands for beef cattle propagation and constitute the principal livestock activity in the Pampas and Campos areas. Cow-calf system sustainability is questioned because of their low production levels and negative environmental impact. Ecological intensification has been proposed as a way out that constitutes an alternative to dominant discourses based on increasing external-input use. There is, however, a considerable gap between the availability of scientific knowledge to promote the ecological intensification of cow-calf systems and farmers' practices. This gap between scientific knowledge availability and farmers' practices can be made explicit, and its consequences for systems performance can be explored through a conceptual model. Conceptual models are tools to build a systems view of the interactions among the production system's state variables, farm management, and resulting system performance. In this paper, we develop a conceptual model of cow-calf systems on native grasslands of the Pampas and Campos regions to support the diagnosis and redesign of farm systems towards ecological intensification. We apply the conceptual model to analyse cow-calf systems in Uruguay, drawing on a survey among 250 Uruguayan livestock farmers. Using the model, we show that in Uruguay, the level of implementation of strategic, tactical, and decision-supporting techniques is low. Consequently, most farms have poor control of the grazing intensity and timing of main events in the production cycle. This results in ample room to improve the productive and environmental performance of most cow-calf farms in Uruguay. We distinguished three broad types of cow-calf systems based on the degree of implementation of techniques, the evolution of state variables throughout the year, and productive indicators. These types imply different departure points and strategies for a sustainability transition process. The conceptual model designed in this paper may support the cow-calf systems sustainability transition in the context of co-innovation processes by aiding the interactive diagnosis and redesign of farm systems.

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.

Beef cows housed in mud during late gestation have greater net energy requirements compared with cows housed on wood chip bedding

Mud increases net energy requirements for cattle because mud and precipitation compromise the ability of the hair coat to insulate and maintain core body temperature of the cow. The increase in energy required for a gestating cow to compensate for a muddy environment is unknown. The objective of this study was to evaluate effects of muddy conditions on cow body weight (BW) and fetal growth during late gestation. Sixteen multiparous Angus cows (n = 8/treatment) were paired based on initial BW and one cow from each pair was randomly allocated to either the mud (MUD) or control (CON) treatment on day 213 of gestation. Pens in the CON group were bedded with wood chips, while pens in the MUD group were designed to create a muddy lot (average depth of 23.6 ± 5.8 cm). Cows were housed outdoors individually and fed the same diet that consisted of a limit-fed total mixed ration. Each pair was fed to meet energy and protein requirements for maintenance and gestation. From day 213 to 269 of gestation, cows were weighed and sampled for blood metabolites weekly. Data were analyzed as a randomized complete block design with repeated measurements (SAS 9.4). Though cows consumed the same amount of dry matter, cows in the MUD treatment weighed 37.4 kg less than cows in the CON treatment (P < 0.01) by day 269 of gestation. Cows in the MUD treatment decreased approximately half a body condition score (BCS), while cows in the CON treatment gained approximately 1 BCS during the treatment period (P < 0.01). There was no evidence of a treatment × day of gestation effect for 12th rib back fat (P = 0.85), rump fat (P = 0.48), total plasma protein concentrations (P = 0.85), or plasma 3-methylhistidine (P = 0.84); however, there was a marginally significant treatment × day of gestation effect for plasma non-esterified fatty acid concentration (P = 0.09). Despite differences in cow BW at the end of the treatment period, calf birth weight (P = 0.66) and calf total plasma protein (P = 0.27) were not different; however, the divergence in cow BW remained marginally significant at parturition (P = 0.06). These results indicate that mud increased net energy requirements for cows in the MUD treatment, as calf birth weight was not different but maternal BW was decreased compared with cows in the CON treatment.

Native Grasslands at the Core: A New Paradigm of Intensification for the Campos of Southern South America to Increase Economic and Environmental Sustainability

Extensive livestock production in southern South America occupies ~0.5 M km2 in central-eastern Argentina, Uruguay and southern Brazil. These systems have been sustained for more than 300 years by year-long grazing of the highly biodiverse native Campos ecosystems that provides many valuable additional ecosystem services. However, their low productivity (~70 kg liveweight/ha per year), at least relative to values recorded in experiments and by best farmers, has been driving continued land use conversion towards agriculture and forestry. Therefore, there is a pressing need for usable, cost effective technological options based on scientific knowledge that increase profitability while supporting the conservation of native grasslands. In the early 2000s, existing knowledge was synthesized in a path of six sequential steps of increasing intensification. Even though higher productivity underlined that path, it was recognized that trade-offs would occur, with increases in productivity being concomitant to reductions in diversity, resilience to droughts, and a higher exposure to financial risks. Here, we put forward a proposal to shift the current paradigm away from a linear sequence and toward a flexible dashboard of intensification options to be implemented in defined modules within a farm whose aims are (i) to maintain native grasslands as the main feed source, and (ii) ameliorate its two major productive drawbacks: marked seasonality and relatively rapid loss of low nutritive value-hence the title “native grasslands at the core.” At its center, the proposal highlights a key role for optimal grazing management of native grasslands to increase productivity and resilience while maintaining low system wide costs and financial risk, but acknowledges that achieving the required spatio-temporal control of grazing intensity requires using (a portfolio of) complementary, synergistic intensification options. We sum up experimental evidence and case studies supporting the hypothesis that integrating intensification options increases both profitability and environmental sustainability of livestock production in Campos ecosystems.

Metabolic hormones, grazing behaviour, offspring physical distance and productive response of beef cow grazing at two herbage allowances

Herbage allowance (HA) management during gestation-lactation cycle of cows grazing native grasslands improves pregnancy rates and calves' weaning weight records. Those improvements were associated with greater herbage mass, and better body condition score (BCS) and metabolic status of the cows, which could affect grazing and maternal behaviour, particularly when temporary suckling restriction (TSR) and flushing (FL) is applied. The objective of this study was to evaluate the effect of HA during the gestation-lactation period on cows' and calves' liveweight (LW), BCS, milk yield, insulin, IGF-1 and leptin concentrations, as well as the proportion of diurnal grazing activities (grazing, ruminating, walking and idling), and maternal behaviour from -10 to 70 days relative to TSR (day 0 = initiation of TSR at 86 ± 10 days relative to calving). Thirty-three primiparous Hereford cows were allocated to HA treatments during gestation and lactation, which annually averaged 2.5 (low = LHA) and 4 kg DM/kg LW (high = HHA). The LW and BCS of cows did not differ during -10 to 50 days but were greater in HHA than LHA at the end of the study (P < 0.05). Concentrations of IGF-1 were greater in HHA compared to LHA, while insulin and leptin did not differ. Grazing was lower in HHA than LHA, and the opposite occurred with ruminating and idling (P < 0.05). Cow-calf physical distance was greater in LHA cows compared to HHA (P < 0.05) and increased greatly in the former group after FL, while this increase was lower and later in HHA cows. Milk yield was greater in HHA (P < 0.05), and calves' weight did not differ between treatments from day -10 to 35, but was greater in HHA compared to LHA from 45 days until the end of the study. Thus, the HHA in a low herbage height and mass condition resulted in greater IGF-1 concentrations and milk yield, and induced changes in grazing and maternal behaviour that were associated with increased cows' LW, BCS and calves' weight at the end of the study.

Effect of herbage allowance on productive and reproductive responses of primiparous beef cows grazing on Campos grassland

The effects of two levels of herbage allowance (HA, kg DM/kg liveweight (LW)) on forage mass and chemical composition, cow body condition score, cow LW, stocking rate, productive and reproductive responses were evaluated during two consecutive years. Eighty primiparous spring-calving beef cows were allocated to a completely randomised block design of two HA that had an annual average of 2.5 (low) and 4.0 kg DM/kg LW (high) from –150 to 195 days postpartum. The grazing system was continuous, and the put-and-take method was employed to adjust HA. At 86 ± 12 days postpartum, all cows were submitted to calf suckling restrictions with nose plates (12 days) and dietary flushing (2 kg/cow.day of whole-rice bran for 22 days), 6 days before bull introduction. Forage mass was affected by HA (P = 0.004) and year (P = 0.014); the high HA had a greater forage mass than the low HA (1474 vs 1212 ± 86 kg DM/ha; P < 0.05), and Year 2 had a greater forage mass than Year 1 (1545 vs 1134 ± 78 kg DM/ha; P < 0.05). Stocking rate was affected by HA and season (P = 0.0004) interaction. The stocking rate during autumn and spring was greater in low than high HA, and no differences were identified in winter and summer. The body condition score was improved in high HA during autumn and resulted in a greater winter (mid-gestation) body condition score than the low HA without differences during spring-summer (postpartum). Cow LW was lower during autumn, winter and early postpartum (16 days postpartum) in low HA in Year 1 than high HA of Year 1 and high and low HA cows in Year 2. Furthermore, the probability of total pregnancies (0.88 vs 0.59 ± 0.07; P = 0.01) and the calf weight adjusted to 205 days (194 vs 175 ± 16 kg; P < 0.05) were greater in high HA. Calf weight adjusted to 205 days (Year 1: 192 vs Year 2: 177 ± 16 kg; P < 0.05) and survival curves of postpartum anoestrus (P = 0.01) were affected by year but did not affect the probability of conception, early or total pregnancies. In conclusion, the reproductive and productive responses of primiparous beef cows grazing Campos grasslands were improved in high HA and could contribute to alleviating adverse climatic conditions effects.

Changes in body composition during the winter gestation period in mature beef cows grazing different herbage allowances of native grasslands

The aim of this study was to evaluate the effect of controlling the grazing intensity of native pastures, through the herbage allowances (HA) on body composition (water, protein, and fat) of beef cows of different cow genotype (CG; purebred: Angus and Hereford; PU, and crossbred: reciprocal F1; CR). Mature beef cows (n = 32) were used in a complete randomised block design with a factorial arrangement of HA (2.5 vs 4 kg DM/day; LO vs HI) and CG (PU vs CR). The experiment was conducted during 3 years and at the end of the third year at 150, 210, and 240 ± 10 days of gestation and 190 ± 10 days postpartum body composition was estimated using the urea dilution technique. At 192 ± 10 days postpartum cows were slaughtered and all tissues and organs were weighed and samples were collected for chemical composition analyses. During the winter gestation period, body condition score was greater (P < 0.05) in HI than LO cows and in CR than PU cows. Relative body water (g/kg of empty bodyweight) was greater (P ≤ 0.02) in HI than LO cows and in CR than PU cows, whereas relative body protein did not differ between HI and LO, but tended (P = 0.10) to be greater in CR than PU cows. In contrast, relative body fat tended (P = 0.10) to be greater and gross energy content was greater (P < 0.01) in HI than LO cows, whereas they did not differ between CR and PU cows. Relative body water increased (P < 0.01) from 150 to 210 days of gestation for all cows whereas relative body fat decreased (P < 0.05) and body protein increased (P < 0.05) from 150 to 210 days of gestation in PU but not in CR cows. These results suggest that HI maintained greater body condition score and retained gross energy content when compared with LO cows, and CG affected not only body composition (greater body fat and protein in CR than PU cows) but also composition of mobilised/retained weight during the winter gestation period with a greater protein tissue mobilisation in CR than PU cows.

Influence of a short-term prepartum supplementation on beef cows and calves’ performance in pastoral conditions

Multiparous Aberdeen Angus × Hereford crossbred cows were used to evaluate the effect of supplementation during the last month of gestation on milk production and composition and cow and calf performance. Cows were assigned randomly to supplement (SUP; n = 18) or Control (CON; n = 17) treatments. Supplemented cows were offered (1 kg/100 kg bodyweight) a mix of sorghum grain and protein concentrated (67 : 33 as-fed basis; 16% crude protein, 11% acid detergent fibre) from (mean ± s.e.m.) 33 ± 1.4 days prepartum until calving. Before, during, and after the supplementation period, cows grazed together a native pasture paddock with average forage mass available of 1345 kg/ha of dry matter (10.4% crude protein, 45.2% acid detergent fibre). Cows were blood sampled weekly from –42 to 112 days postpartum (DPP) for serum progesterone and non-esterified fatty acids (NEFA) concentrations. Maximum follicle diameter was measured by ovarian ultrasound examination at 60 DPP. The breeding period lasted 60 days and started at 60 ± 1.4 DPP. There was an interaction between treatment and time on BCS (P < 0.0005). Before calving there were no differences in BCS between cows in SUP and in CON, but at calving SUP cows tended (P = 0.10) to present greater BCS and from calving to 84 DPP BCS was greater (P < 0.05) in SUP with respect to CON cows. There was an interaction between treatment and time on plasma NEFA concentrations (P < 0.0005). During the last month of gestation NEFA concentrations were reduced in SUP cows but there were no differences between treatments during the postpartum period. Milk production decreased linearly from 30 to 150 DPP but there was no effect of treatment on it. Calf bodyweight at birth and at weaning did not differ between treatments (37.5 ± 2.4 and 175.6 ± 2.4 kg, respectively). The probability of cows presenting follicles with diameter ≥10 mm was greater (P < 0.05) in SUP than CON cows. The length of the postpartum period did not differ between treatments. The probability of cows cycling during the first 90 DPP and pregnancy rate tended (P = 0.08) to be greater in SUP than in CON cows. Supplementation in winter and for only 30 days in the last month of gestation of beef cows under grazing conditions, increased cows’ BCS without increasing BW of calves, and tended to improve reproductive performance.

Beef cattle welfare in the USA: identification of priorities for future research

This review identifies priorities for beef cattle welfare research in the USA. Based on our professional expertise and synthesis of existing literature, we identify two themes in intensive aspects of beef production: areas where policy-based actions are needed and those where additional research is required. For some topics, considerable research informs best practice, yet gaps remain between scientific knowledge and implementation. For example, many of the risk factors and management strategies to prevent respiratory disease are understood, but only used by a relatively small portion of the industry. This is an animal health issue that will require leadership and discussion to gain widespread adoption of practices that benefit cattle welfare. There is evidence of success when such actions are taken, as illustrated by the recent improvements in handling at US slaughter facilities. Our highest priorities for additional empirical evidence are: the effect of technologies used to either promote growth or manage cattle in feedlots, identification of management risk factors for disease in feedlots, and management decisions about transport (rest stops, feed/water deprivation, climatic conditions, stocking density). Additional research is needed to inform science-based recommendations about environmental features such as dry lying areas (mounds), shade, water and feed, as well as trailer design.

Liver functional genomics in beef cows on grazing systems: novel genes and pathways revealed

The adaptation of the liver to periods of negative energy balance is largely unknown in beef cattle on grazing systems. We evaluated liver transcriptome throughout gestation and early lactation of purebred and crossbred beef cows [Angus, Hereford, and their F1 crossbreeds (CR)], grazing high or low herbage allowances (HA) of native grasslands (4 and 2.5 kg dry matter/kg body wt annual mean; n = 16) using an Agilent 4 × 44k bovine array. A total of 4,661 transcripts were affected by days [272 ≥ 2.5-fold difference, false discovery rate (FDR) ≤ 0.10] and 47 pathways were altered during winter gestation (-165 to -15 days relative to calving), when cows experienced decreased body condition score, decreased insulin, and increased nonesterified fatty acid concentrations. Gluconeogenesis and fatty acid oxidation pathways were upregulated, while cell growth, DNA replication, and transcription pathways were downregulated (FDR ≤ 0.25). We observed only small changes in the liver transcriptome during early lactation (+15 to +60 days). A total of 225 genes were differentially expressed (47 ≥ 2-fold difference, FDR ≤ 0.10) between HA. The majority of those were related to glucose and pyruvate metabolism and were upregulated in high HA, reflecting their better metabolic status. Two genes were upregulated in CR cows, but 148 transcripts (74 ≥ 2-fold change difference, FDR ≤ 0.10) were affected by the HA and cow genotype interaction. The transcriptional changes observed indicated a complex and previously unrecognized, hepatic adaptive program of grazing beef cows in different nutritional environments. Novel target candidate genes, metabolic pathways, and regulatory mechanisms were reported.