Feeding dried distillers grains with solubles to lactating beef cows: impact of excess protein and fat on cow performance,milk production and pre-weaning progeny growth

Multiparous Angus×Simmental cows (n=54, 5.22±2.51 years) with male progeny were fed one of two diets supplemented with either dried distillers grains with solubles (DDGS) or soybean meal (CON), from calving until day 129 postpartum (PP) to determine effects of excess protein and fat on cow performance, milk composition and calf growth. Diets were formulated to be isocaloric and consisted of rye hay and DDGS (19.4% CP; 8.76% fat), or corn silage, rye hay and soybean meal (11.7% CP; 2.06% fat). Cow–calf pairs were allotted by cow and calf age, BW and breed. Cow BW and body condition score (BCS; P⩾0.13) were similar throughout the experiment. A weigh-suckle-weigh was performed on day 64 and day 110±10 PP to determine milk production. Milk was collected on day 68 and day 116±10 PP for analysis of milk components. Milk production was unaffected (P⩾0.75) by dietary treatments. Milk urea nitrogen was increased at both time points in DDGS compared with CON cows (P<0.01). Protein was decreased (P=0.01) and fat was increased (P=0.01) in milk from DDGS compared with CON cows on day 68 PP. Compared to CON, DDGS decreased medium chain FA (P<0.01) and increased long chain FA (P<0.01) at both time points. Saturated FA content of milk was decreased (P<0.01) at both time-points in DDGS compared with CON cows, which resulted in an increase (P<0.01) in monounsaturated and polyunsaturated FA, including cis-9, trans-11 conjugated linoleic acid. Daily gain of the DDGS calves was increased (P=0.01) compared with CON calves, resulting in heavier BW on day 129 (P=0.01). Heavier BW of DDGS calves was maintained through weaning (P=0.01). Timed-artificial insemination (TAI) rates were greater for cows fed DDGS compared with cows fed CON (P<0.02), but dietary treatment had no effect on overall pregnancy rates (P=0.64). In summary, feeding DDGS to lactating beef cows did not change cow BW or BCS, but did improve TAI rates and altered milk composition compared with CON. As a result, male progeny from cows fed DDGS during lactation had greater average daily gain and were heavier at day 129 and at weaning compared with male progeny from cows fed a control diet.     

Effects of feeding frequency of an elevated plane of milk replacer and calf age on behavior,and glucose and insulin kinetics in male Holstein calves

Optimizing feeding regimens in early life to maximize lifelong growth and production are essential in the dairy industry. This study investigated the effects of milk replacer (MR) feeding frequency and calf age on behavior, and glucose and insulin kinetics of pre- and post-weaned calves fed an elevated plane of MR. Ten male Holstein calves (42.2±1.8 kg BW) were blocked by BW and randomly assigned to two treatments offering 8 l MR/day (150 g/l) in two (2×; meal size 4 l) or four (4×; meal size 2 l) feedings via an automated calf feeder. Milk replacer was gradually stepped down by 1 l/day during week 8, with calves being weaned by week 9. Water and pelleted calf starter were offered ad libitum. Individual intake of MR and starter were recorded daily, and BW was recorded weekly. The number of visits to the MR feeder (rewarded and unrewarded), and behaviors such as lying, cross-sucking, non-nutritive sucking and occupancy time in the feeder were recorded for individual calves from weeks 4 to 10. Jugular catheters were placed on weeks 4, 7 and 10 to facilitate postprandial blood sampling and glucose tolerance tests. Statistical analysis was conducted using the PROC GLIMMIX procedure (SAS) for behavioral observations, and the MIXED procedure (SAS) with repeated measures for BW, intake, plasma glucose and plasma insulin data. Final BW, starter and MR intake did not differ between treatments. There were no differences in observed calf behaviors; with the exception that 2× calves visited the MR feeder more often (P<0.01; total: unrewarded and rewarded). Baseline concentrations (mmol/l) and the maximum change in glucose (delta, mmol/l) were greater and lower (P=0.02) in 4×compared to 2×calves, respectively. Postprandial insulin AUC₂₄₀ tended (P=0.09) to be greater in 2×calves, compared to 4×calves at week 7. Similarly, T_max (min), AUC₂₄₀ and delta values (µU/ml) were greater (P⩽0.05) in 2×calves, compared to 4×calves. No treatment ×age interactions were observed for glucose or insulin during the glucose tolerance tests. Therefore, we conclude that feeding an elevated plane of MR (8 l/day) at a lower frequency (2× v. 4×) increased feeder visits, but not other hunger-related behaviors, and while postprandial glucose and insulin parameters varied, insulin sensitivity remained stable in Holstein dairy calves up to 10 weeks of age in calves consuming similar levels of calf starter.     

Feeding behaviour and activity as early indicators of disease in pre-weaned dairy calves

Across the industry, there is large variation in health status of dairy calves and as a result, disease incidence and antibiotic use is high. This has significant implications for animal welfare, productivity and profitability of dairy and dairy-beef production systems. Technology-based early detection systems could alleviate these issues; however, methods of early detection of disease in dairy calves have not been widely explored. This study aimed to determine whether changes in activity and feeding behaviour can be used as early warning indicators of respiratory disease in calves. In total, 100 pre-weaned male Holstein calves (age: ~ 8−42 days) were used. Calves were group-housed and provided with starter diet, straw bedding and ad libitum water. Calves were fed milk replacer ad libitum through an automatic calf feeder, and each calf was fitted with a leg-mounted activity monitor. Daily activity and feeding behaviour variables were calculated for each calf. Each calf was assessed daily using a modified version of the Wisconsin Scoring System to assess respiratory disease status. Calves were classed as ‘Diseased’, ‘Intermediate’ or ‘Healthy’ based on their cumulative health score. The peak day of the most extreme illness event was identified for each calf. Data from Diseased and Healthy calves were paired for analysis based on age and BW. Data were compared for the day of peak illness, and for the 3 days previous and post. Compared to healthy calves, diseased calves lay for longer and tended to have longer lying bouts (daily lying: 17.6 ± 0.3 vs 16.7 ± 0.2 h, P < 0.01; bout length: 74.8 ± 10.6 vs 56.0 ± 3.7 min, P = 0.09 for diseased and healthy calves, respectively). Diseased calves fed for a shorter time and had fewer feeder visits (with intake) each day compared to healthy calves (feeding time (min): 19.3 ± 1.4 vs 22.8 ± 1.5; P < 0.05; visits: 2.1 ± 0.2 vs 3.2 ± 0.4; P < 0.05). Importantly, differences between diseased and healthy calves were evident in both activity and feeding behaviour on the days prior to the peak day of disease. Lying bout length was greater in diseased calves for the 2 days prior to the peak day (P < 0.05), lying time was longer on day − 1 (P < 0.05) and feeder visits with milk intake were less frequent on day − 3 (P < 0.05). Thus, measurement of feeding and activity using precision technology within early detection systems could facilitate early intervention and optimized treatment.     

Post-weaning feed efficiency decreased in progeny of higher milk yielding beef cows

Current trends in the beef industry focus on selecting production traits with the purpose of maximizing calf weaning weight; however, such traits may ultimately decrease overall post-weaning productivity. Therefore, the objective of this study was to evaluate the effects of actual milk yield in mature beef cows on their offspring’s dry matter intake (DMI), BW, average daily gain, feed conversion ratio (FCR) and residual feed intake (RFI) during a ~75-day backgrounding feeding trial. A period of 24-h milk production was measured with a modified weigh-suckle-weigh technique using a milking machine. After milking, cows were retrospectively classified as one of three milk yield groups: Lower (6.57±1.21 kg), Moderate (9.02±0.60 kg) or Higher (11.97±1.46 kg). Calves from Moderate and Higher milk yielding dams had greater (P<0.01) BW from day 0 until day 75 at the end of the backgrounding feeding phase; however, day 75 BW were not different (P=0.36) between Lower and Moderate calves. Body weight gain was greater (P=0.05) for Lower and Moderate calves from the day 0 BW to day 35 BW compared with Higher calves. Overall DMI was lower (P=0.03) in offspring from Lower and Moderate cows compared with their Higher milking counterparts. With the decreased DMI, FCR was lower (P=0.03) from day 0 to day 35 in calves from Lower and Moderate milk yielding dams. In addition, overall FCR was lower (P=0.02) in calves from Lower and Moderate milk yielding dams compared with calves from Higher milk yielding dams. However, calving of Lower milk yielding dams had an increased (P=0.04) efficiency from a negative RFI value compared with calves from Moderate and Higher milking dams. Results from this study suggest that increased milk production in beef cows decreases feed efficiency during a 75-day post-weaning, backgrounding period of progeny.     

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.     

Short communication: administering an appeasing substance to Bos indicus-influenced beef cattle at weaning and feedlot entry

The bovine appeasing substance (BAS) is expected to have calming effects in cattle experiencing stressful situations. Therefore, this study investigated the impacts of BAS administration during two of the most stressful events within beef production systems: weaning and feedlot entry. In experiment 1, 186 Bos indicus-influenced calves (73 heifers, 113 bulls) were weaned at 211 ± 1 days of age (day 0). At weaning, calves were ranked by sex and BW, and assigned to receive BAS (Nutricorp, Araras, SP, Brazil; n = 94) or water (CON; n = 92). Treatments (5 ml) were topically applied to the nuchal skin area of each animal. Calf BW was recorded and samples of blood and tail-switch hair were collected on days 0, 15 and 45. Calves that received BAS had greater (P < 0.01) BW gain from day 0 to 15 compared with CON. Overall BW gain (days 0 to 45) and BW on days 15 and 45 were also greater (P ≤ 0.03) in BAS v. CON. Plasma haptoglobin concentration was less (P < 0.01) in BAS v. CON on day 15, whereas cortisol concentrations in plasma and tail-switch hair did not differ between treatments (P ≥ 0.13). In experiment 2, 140 B. indicus-influenced bulls (∼27 months of age) from 2 different pasture-based systems (70 bulls/origin) were transported to a commercial feedlot (≤ 200-km transport; day -1). On day 0, bulls were ranked by source and BW, and assigned to receive BAS (n = 70) or CON (n = 70) and the same sampling procedures as in experiment 1. Bulls receiving BAS had greater (P = 0.04) BW gain from day 0 to 15, but less (P < 0.01) BW gain from day 15 to 45 compared to CON. No other treatment effects were detected (P > 0.14). Therefore, BAS administration to beef calves alleviated the haptoglobin response associated with weaning, and improved calf growth during the subsequent 45 days. Administration of BAS to beef bulls at feedlot entry improved BW gain during the initial 15 days, but these benefits were not sustained throughout the 45-day experiment.     

Effect of pre-weaning feeding regimens on post-weaning growth performance of Sahiwal calves

The objective of the study was to assess the post-weaning growth response of Sahiwal calves reared on four different pre-weaning dietary regimens. The four diets were: (a) whole cow's milk, starter ration (SR; CP = 20%, total digestible nutrients (TDN) = 72%) and Berseem hay (H; Egyptian clover; CP = 21%, TDN = 63%); (b) whole cow's milk + H; (c) milk replacer (MR; reconstituted to supplier specification; Sprayfo®) + SR + H; and (d) MR + H. The protein and fat percentages of reconstituted MR were 2.22 and 1.84, respectively. Milk or MR were fed at the rate of 10% of the calves’ body weight (BW) until 56 days of age, and then withdrawn gradually until weaned completely by 84 days of age. The average initial BW of calves in groups A, B, C and D were 56.3 ± 1.0, 47.5 ± 1.0, 40.4 ± 1.0 and 30.3 ± 1.0 kg, respectively. Initially, there were 12 calves in each group with six of each sex; however, one male calf died from each of groups B and C and were not replaced. During the post-weaning period, 13 to 24 weeks, the calves were fed a single total mixed ration ad libitum based on maize, canola meal, wheat straw and molasses containing 16% CP and 70% TDN. Daily feed intake and weekly BW gains were recorded. The data were analyzed by MIXED model analysis procedures using the statistical program SAS. The intake of calves as percent of their BW, feed conversion ratio and cost per kg of BW gain were not different (P > 0.05) across treatments. The daily gain at 24 weeks of age for the pre-weaning treatments A, B, C and D were 746 ± 33, 660 ± 33, 654 ± 33 and 527 ± 33 g/day and the final liveweights of calves were 119 ± 4.2, 102 ± 4.2, 95 ± 4.2 and 75 ± 4.2 kg, respectively. Gains were influenced significantly (P < 0.05) by pre-weaning treatments. The calves fed MR and H only during the pre-weaning period were unable to catch up post weaning with calves on other dietary treatments. The calves fed whole milk from birth at the rate of 10% of liveweight together with concentrates had higher weaning weight and superior growth rate post weaning as well. Thus, pre-weaning feeding was important for higher weaning weights and superior growth rates post weaning.     

Performance of Holstein calves receiving equal quantities of milk at fixed or variable amounts per day during milk-feeding period

Two experiments were conducted to determine the effects of feeding equal quantities of milk during the pre-weaning period through different milk-feeding regimes on calf growth, starter intake and selected blood metabolites. In experiment 1, 44 female Holstein calves (3 days of age and 39.2±4.3 kg of BW) were distributed randomly to one of two milk-feeding programs (1 calf per pen; 22 pens per treatment group): (1) consistent (CONS; 6 l/day of milk from days 3 to 60 and 3 l/day from days 61 to 65 of age) or (2) step-up/step-down (SUSD; 5 l/day of milk from days 3 to 15, 8 l/day from days 16 to 40, 6 l/day from days 41 to 50, 3 l/day from days 51 to 60 and then 2 l/day from days 61 to 65 of age). No difference between treatments was observed in starter consumption, feed efficiency, hip width and heart girth. However, pre-weaning average daily gain (ADG) tended to be greater in CONS than in SUSD calves (0.78 v. 0.70 kg/day; P=0.07). Blood β-hydroxybutyrate at day 45 (pre-weaning) was lower in SUSD than in CONS calves (0.14 v. 0.21±0.013 mmol/l). In experiment 2, 26 male Holstein calves (3 days of age and 39.4±4.1 kg of BW) were assigned at random to one of two milk-feeding protocols (1 calf per pen; 13 pens per treatment group): (1) consistent (CONS; (7 l/day of milk from days 3 to 40 and 2 l/day from days 41 to 45 of age) or (2) step-down (STD; 8 l/day of milk from days 3 to 30, 4 l/day from days 31 to 40 and 2 l/day from days 41 to 45 of age). The milk-feeding program had no effect on the performance measurements, with the exception that ADG (days 15 to 30), starter intake (days 30 to 45) and heart girth (day 45) were greater in STD than in CONS calves. In conclusion, it appears that if the total amount of milk intake is held constant over the course of milk-feeding period, the method of milk feeding would have negligible effects on calf performance.     

Divergence for residual feed intake of Holstein-Friesian cattle during growth did not affect production and reproduction during lactation

Residual feed intake (RFI) is the difference between actual and predicted dry matter intake (DMI) of individual animals. Recent studies with Holstein-Friesian calves have identified an ~20% difference in RFI during growth (calf RFI) and these groups remained divergent in RFI during lactation. The objective of the experiment described here was to determine if cows selected for divergent RFI as calves differed in milk production, reproduction or in the profiles of BW and body condition score (BCS) change during lactation, when grazing pasture. The cows used in the experiment (n=126) had an RFI of −0.88 and +0.75 kg DM intake/day for growth as calves (efficient and inefficient calf RFI groups, respectively) and were intensively grazed at four stocking rates (SR) of 2.2, 2.6, 3.1 and 3.6 cows/ha on self-contained farmlets, over 3 years. Each SR treatment had equal number of cows identified as low and high calf RFI, with 24, 28, 34 and 40/11 ha farmlet. The cows divergent for calf RFI were randomly allocated to each SR. Although SR affected production, calf RFI group (low or high) did not affect milk production, reproduction, BW, BCS or changes in these parameters throughout lactation. The most efficient animals (low calf RFI) lost similar BW and BCS as the least efficient (high calf RFI) immediately post-calving, and regained similar BW and BCS before their next calving. These results indicate that selection for RFI as calves to increase efficiency of feed utilisation did not negatively affect farm productivity variables (milk production, BCS, BW and reproduction) as adults when managed under an intensive pastoral grazing system.     

Effect of milk replacer and concentrate intake on growth rate,feeding behaviour and systemic metabolite concentrations of pre-weaned bull calves of two dairy breeds

Early-life nutrition affects calf development and thus subsequent performance. The aim of this study was to examine the effect plane of nutrition on growth, feeding behaviour and systemic metabolite concentrations of artificially reared dairy bull calves. Holstein-Friesian (F; n=42) and Jersey (J; n=25) bull calves with a mean±SD age (14±4.7 v. 27±7.2 days) and BW (47±5.5 v. 33±4.7 kg) were offered a high, medium or low plane of nutrition for 8 weeks using an electronic feeding system which recorded a range of feed-related events. Calves were weighed weekly and plasma samples were collected via jugular venipuncture on weeks 1, 4 and 7 relative to the start of the trial period. The calves offered a high plane of nutrition had the greatest growth rate. However, the increased consumption of milk replacer led to a reduction in feed efficiency. Holstein-Friesian calves offered a low plane of nutrition had the greatest number of daily unrewarded visits to the feeder (P<0.001). β-hydroxybutyrate (BHB) concentrations were greater in F calves on a low plane of nutrition (P<0.001). Although there was no effect of plane of nutrition, BHB concentrations in F calves increased before weaning, concomitant with an increase in concentrate consumption. Urea concentrations were unaffected by plane of nutrition within either breed. Jersey calves on a low plane of nutrition tended to have lower triglycerides than those on a high plane (P=0.08), but greater than those on a medium plane (P=0.08). Holstein-Friesian calves offered a high plane of nutrition tended to have greater triglyceride concentrations than those on a medium plane (P=0.08). Triglycerides increased from the start to the end of the feeding period (P<0.05), across both breeds. A medium plane of nutrition resulted in a growth, feeding behaviour and metabolic response comparable with a high plane of nutrition in pre-weaned bull calves of both F and J breeds.     

Individual Intake of Free-Choice Mineral Mix by Grazing Beef Cows May Be Less Than Typical Formulation Assumptions and Form of Selenium in Mineral Mix Affects Blood Se Concentrations of Cows and Their Suckling Calves

The objectives of this study were to determine (1) the individual ad libitum intake of mineral mix by beef cows managed under a year-long, fall-calving, forage-based production regimen and (2) if Se form in the mineral mix affected the blood Se concentrations of cows and suckling calves. Twenty-four late-gestation (6 to 8 months) Angus-cross cows (2.7?±?0.8 years; body weight [BW]?=?585?±?58 kg) were blocked by BW and randomly assigned (n?=?8) to a mineral supplement treatment (TRT) containing 35 ppm Se as either inorganic (ISe; sodium selenite), organic (OSe; Sel-Plex®), or a 1:1 combination of ISe/OSe (MIX). Cows commonly grazed a 10.1-ha predominately tall fescue pasture and had individual ad libitum access to TRT using in-pasture Calan gates. Cows calved from August to November and calves had common ad libitum access to creep feed and a mineral supplement that lacked Se. Cow jugular blood was taken at 28-day intervals (13 periods) and calf blood was taken with cows from birth through weaning. Individual cow mineral mix (mean?=?54.0?±?7.0 g/day, range?=?97.3 to 27.9?±?7.4 g/day) and Se (mean?=?1.82?±?0.25 mg/day, range?=?3.31 to 0.95?±?0.25 mg/day) intakes were affected by period (P?<?0.0001), but not by cow Se TRT (P?>?0.30). Cow blood Se (0.109 to 0.229?±?0.01 μg/mL) was affected (P?<?0.002) by period, Se form, and their interaction, with ISe?< MIX for periods 8 and 11, ISe?<?OSe for all periods except period 1, and MIX?<?OSe for periods 2 to 4, 7, 8, 10, and 12. Calf blood Se (in micrograms Se per milliliter) was correlated with cow blood Se and affected (P?<?0.0001) by cow Se TRT, with ISe (0.07 to 0.11)?<?MIX (0.10 to 0.15)?=?OSe (0.16 to 0.19). These data reveal that (1) mean supplemental ad libitum cow mineral intake was 36 % less than the typical formulation intake expectations (85 g/day) and, correspondingly, mean supplemental Se intake was 33 % less than that allowed by the FDA and (2) cow Se TRT differentially affected both cow and calf blood Se concentrations, resulting in adequate concentrations for all cows but inadequate concentrations for ISe calves.     

Effects of isobutyrate supplementation in pre- and post-weaned dairy calves diet on growth performance,rumen development,blood metabolites and hormone secretion

Isobutyrate supplements could improve rumen development by increasing ruminal fermentation products, especially butyrate, and then promote the growth performance of calves. The objective of this study was to evaluate the effects of isobutyrate supplementation on growth performance, rumen development, blood metabolites and hormone secretion in pre- and post-weaned dairy calves. In total, 56 Chinese Holstein male calves with 30 days of age and 72.9±1.43 kg of BW, blocked by days of age and BW, were assigned to four groups in a randomized block design. The treatments were as follows: control, low-isobutyrate, moderate-isobutyrate and high-isobutyrate with 0, 0.03, 0.06 and 0.09 g isobutyrate/kg BW per calf per day, respectively. Supplemental isobutyrate was hand-mixed into milk of pre-weaned calves and the concentrate portion of post-weaned calves. The study consisted of 10 days of an adaptation period and a 50-day sampling period. Calves were weaned at 60 days of age. Seven calves were chosen from each treatment at random and slaughtered at 45 and 90 days of age. BW, dry matter (DM) intake and stomach weight were measured, samples of ruminal tissues and blood were determined. For pre- and post-weaned calves, DM intake and average daily gain increased linearly (P<0.05), but feed conversion ratio decreased linearly (P<0.05) with increasing isobutyrate supplementation. Total stomach weight and the ratio of rumen weight to total stomach weight tended to increase (P=0.073) for pre-weaned calves and increased linearly (P=0.021) for post-weaned calves, whereas the ratio of abomasum weight to total stomach weight was not affected for pre-weaned calves and decreased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. Both length and width of rumen papillae tended to increase linearly for pre-weaned calves, but increased linearly (P<0.05) for post-weaned calves with increasing isobutyrate supplementation. The relative expression of messenger RNA for growth hormone (GH) receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly (P<0.05) for pre- and post-weaned calves with increasing isobutyrate supplementation. Blood concentrations of glucose, acetoacetate, β-hydroxybutyrate, GH and IGF-1 increased linearly (P<0.05) for pre- and post-weaned calves, whereas blood concentration of insulin decreased linearly with increasing isobutyrate supplementation. The present results indicated that isobutyrate promoted growth of calves by improving rumen development and its ketogenesis in a dose-dependent manner.     

Importance of dam BW change and calf birth weight in double-muscled Belgian Blue cattle and its relationship with parity and calving interval

Factors affecting calving interval (CI) in double-muscled Belgian Blue (DMBB) beef cows were investigated with regard to the BW yield (BWY) of the cow–calf pair, using 834 CI records from 386 females with parities 1 to 6. The effect of parity and CI on BWY was also studied. Cow–calf pair BWY was defined as calf birth weight plus dam BWY per CI. CI (mean±s.e.: 404±1.9 days) was affected by parity, calving season, suckling and calf birth weight/dam weight. Primiparous cows had a shorter CI than cows with three or more calvings (P<0.05), with an intermediate CI for second-calf cows. Spring calvings resulted in a shorter CI than summer and autumn calvings, with intermediate values for winter calvings. Suckling dams had longer CIs than non-suckling dams. There were interactions (P<0.05) between calving season and suckling, and between calving season and mating system. Shortest CIs were observed for spring calvings in case of non-suckling and for summer calvings in case of suckling. Longest CIs were observed for autumn calvings in case of natural service (NS) and for winter calvings in case of artificial insemination (AI). Calf birth weight/dam weight of 6% to 10% resulted in shorter CI than a ratio of <6% (P<0.05). Body condition and mating system (NS v. AI) did not affect CI. Daily cow–calf pair BWY was affected by parity (P<0.001) and CI (P=0.013), with a tendency for an interaction (P=0.094). Daily cow–calf pair BWY did not differ for CIs of <12 to 16 months in primiparous cows and was lowest for a CI of 13 to 15 months in second-calf cows, whereas the effect of CI was more variable in older cows. Dam contribution to cow–calf pair BWY was larger than calf birth weight in first- and second-calf cows, and increased with increasing CI. Dam contribution to cow–calf pair BWY was smaller than calf birth weight in older cows, varying from 0.2 to 1.0 depending on CI. A short CI is advised for DMBB cows because of a larger BWY and more efficient nutrient utilisation.     

Carcass characteristics and meat quality of Nellore bulls submitted to different nutritional strategies during cow–calf and stocker phase

There have been few studies realized that evaluate the effects of adoptingdifferent nutritional systems in more than one phase of cattle production oncarcass and meat characteristics. This study was realized to evaluate carcassand meat characteristics from bulls submitted to different nutritional systemsduring two production phases. The experiment was conducted atFigueira’s farm during two production phases: I (cow–calf)– 80 calves (99.6±2.72 days of age and109.7±2.99 kg of BW) with their mothers were randomly assigned intotwo supplemental diets: cow–calf mineral supplement(n=40) or cow–calf creep-feeding(n=40); II (stocker) – the same 80calves (201.2±2.11 days of age and 190.2±3.37 kg of BW)were redistributed into two production systems: stocker pasture(n=40) or stocker feedlot (SF;n=40). After, all 80 animals were kept on a pasturesystem (III) for 290 days, and then finished in a feedlot system (IV) for more33 days. Then, they were slaughtered at an average 764.2±3.06 days ofage and at 499.2±3.33 kg of final BW. After slaughter, the averagedaily gain was calculated, and the carcass and meat characteristics weremeasured. The statistical model design used was completely randomized in a2×2 factorial arrangement (two treatment groups oncow–calf phase and two treatment groups on stocker phase). The singleeffects between the groups in each phase and the interactions between bothphases (cow–calf v. stocker) were analyzed. Theresults were compared by Fisher’s test, using the R statisticalsoftware. A cow–calf by stocker phases interaction occurred forcarcass conformation and fiber diameter. For single effects, the greatestinfluences observed were in the stocker phase. The feedlot group was slaughtered17 days earlier, with greater final BW (3.8%), hot carcass weight(5.7%), average daily gain (6.9%), dressing percentage(1.8%), carcass length (1.8%), carcass width(1.5%), longissimus muscle area (4.8%)and muscle depth (2.3%) than pasture group. The SF group also hadinfluence on fat color; showing higher L* and lowerb* values. These results reveal that bullsreared in feedlot at the stocker phase have higher muscle development and thatthe stocker phase has the greatest potential to influence carcasscharacteristics and meat quality.     

Performance and nursing behaviour of beef cows with different types of calf management

The aim of this experiment was to evaluate the effect of calf management during lactation on dam performance and nursing behaviour. Thirty-six multiparous beef cows (aged 7.5 ± 0.52 years) of Parda de Montaña breed (mean live-weight (LW) at calving 566 ± 9.3 kg) with a moderate body condition (mean 2.6 ± 0.02 on a 1 to 5 scale), were assigned to three nursing frequencies from the day after parturition: Once-daily restricted nursing during a 30 min period at 0800 h (RESTR1), twice-daily restricted nursing during two 30 min periods at 0800 and 1530 h (RESTR2) and ad libitum nursing (ADLIB). Cows were fed throughout the experiment 80 MJ/day of metabolizable energy. Cow–calf behaviour recordings were performed on days 30 and 66 of lactation in each treatment. Blood samples were collected fortnightly to analyse non-esterified fatty acids (NEFA) by an enzymatic colorimetric method, and twice weekly to determine progesterone concentrations by radioimmunoassay. Cow LW losses (P < 0.05), fat-corrected milk yield (P < 0.05) and calf average daily gain (P < 0.01) during lactation were higher in ADLIB. Nursing frequency affected the mean serum concentrations of NEFA, being lower in RESTR1 (0.18 mmol/l; P < 0.05) than in RESTR2 and ADLIB cows (0.29 and 0.25 mmol/l, respectively). The highest occurrence of nursing bouts was observed in ADLIB, leading to greater nursing duration per day (not statistically compared) in this treatment (58.8 ± 5.84 min) than in their restricted nursing counterparts (22.2 ± 1.42 and 34.3 ± 1.16 min, in RESTR1 and RESTR2, respectively). The nursing system did not affect the proportion of cows cycling within 3 months post partum (58%, 46% and 55% in RESTR1, RESTR2 and ADLIB, respectively; P > 0.05). The majority of cows in all treatments showed a short oestrus cycle after first ovulation (75%, 100% and 83%; P > 0.05). In conclusion, the post-partum luteal function in cows managed under continuous access to calves was similar to restricted nursing frequencies, despite the greater suckling intensity of the formers. Restricting calf presence does not enhance the resumption of ovarian activity when suckler cows are managed in moderate nutritional conditions.     

Performance of ad libitum fed dairy calves weaned using fixed and individual methods

The increasing availability of automated milk dispensers on dairy farms facilitates ad libitum milk supply but weaning calves from high milk allowances is challenging. This study evaluated effects of gradual weaning methods on starter intake, growth, selected blood parameters and weaning distress in ad libitum fed dairy calves during weaning and early post-weaning periods. Thirty-six male Holstein (n = 30) or crossbred (n = 6) calves were individually housed from days 2 to 14 of age and had ad libitum access to milk replacer (MR) from teat buckets. From days 15 to 84 of age, calves were grouped and had ad libitum access to MR, starter, straw and water from automated feeders. At day 35, calves were blocked (age and breed), and randomly assigned to a weaning method: (1) linear fixed (LIN), MR supply was stepped down to 6 l/day on day 36, and linearly reduced between days 36 to 63 from 6 to 2 l/day. (2) Step-down (STEP), MR supply was stepped down to 6 l/day from days 36 to 48, 4 l/day from days 49 to 56 and 2 l/day from days 57 to 63. (3) Dynamic (DYN), at day 36, MR supply was reduced for each individual calf to 75% of the average voluntary consumption between day 29 and 35, then maintained for 9 days, reduced to 50% for 10 days, and to 25% for 9 days. The DYN calves received more MR during weaning than LIN calves, whereas STEP calves had intermediate MR intake. Starter intake was not affected by weaning method. The DYN calves (1.33±0.08 kg/day) grew faster and were heavier than STEP calves (1.10±0.08 kg/day) during post-weaning period, whereas no difference was observed between LIN calves (1.23±0.08 kg/day) and others. At days 70 and 84, concentrations of β-hydroxybutyric acid were higher in LIN calves compared to STEP and DYN calves. Hair cortisol concentrations were not affected by weaning method. During the gradual weaning process CP intake seemed to recovered earlier than metabolizable energy (ME) intake in all treatments, suggesting that ME rather than CP could be the first limiting factor for growth during weaning. These results highlight the post-weaning benefits of DYN and LIN weaning methods when compared with more abrupt step-down strategies.     

Effects of temperament on growth,plasma cortisol concentrations and puberty attainment in Nelore beef heifers

Excitable temperament disrupts physiological events required for reproductive development in cattle, but no research has investigated the impacts of temperament on growth and puberty attainment in Bos indicus females. Hence, this experiment evaluated the effects of temperament on growth, plasma cortisol concentrations and puberty attainment in B. indicus heifers. A total of 170 Nelore heifers, weaned 4 months before the beginning of this experiment (days 0 to 91), were managed in two groups of 82 and 88 heifers each (mean ± SE; initial BW=238±2 kg, initial age=369±1 days across groups). Heifer temperament was evaluated via exit velocity on day 0. Individual exit score was calculated within each group by dividing exit velocity into quintiles and assigning heifers with a score from 1 to 5 (1=slowest; 5=fastest heifer). Heifers were classified according to exit score as adequate (ADQ, n=96; exit score⩽3) or excitable temperament (EXC, n=74; exit score>3). Heifer BW, body condition score (BCS) and blood samples were obtained on days 0, 31, 60 and 91. Heifer exit velocity and score were recorded again on days 31, 60 and 91. Ovarian transrectal ultrasonography was performed on days 0 and 10, 31 and 41, 60 and 70, 81 and 91 for puberty evaluation. Heifer was declared pubertal at the first 10-day interval in which a corpus luteum was detected. Exit velocity and exit score obtained on day 0 were correlated (r⩾0.64, P<0.01) with evaluations on days 31, 60 and 91. During the experiment, ADQ had greater (P<0.01) mean BCS and BW gain, and less (P<0.01) mean plasma cortisol concentration compared with EXC heifers. Temperament × time interactions were detected (P<0.01) for exit velocity and exit score, which were always greater (P<0.01) in EXC v. ADQ heifers. A temperament × time interaction was also detected (P=0.03) for puberty attainment, which was delayed in EXC v. ADQ heifers. At the end of the experiment, a greater (P<0.01) proportion of ADQ were pubertal compared with EXC heifers. In summary, B. indicus heifers classified as EXC had reduced growth, increased plasma cortisol concentrations and hindered puberty attainment compared to ADQ heifers. Moreover, exit velocity may serve as temperament selection criteria to optimize development of B. indicus replacement heifers.     

Evaluation of nutrition models to estimate performance of young dairy calves: a meta-analytical study under tropical conditions

Mathematical models are important tools to estimate nutritional requirements and animal growth. Very few calf models generated from other countries with different feeding programs, environment and production systems have been evaluated. The objective of this paper is to evaluate two calf models: (i) the National Research Council (NRC) in 2001 and (ii) the updates published by Van Amburgh and Drackley in 2005 and inputted into Agricultural Modeling and Training Systems (AMTS, version 3.5.8). Data from 16 previous studies involving 51 diets for dairy calves under tropical conditions (n=485 calves, initial BW 37.5±4.35 kg and weaning weight of 62.0±10.16 kg) were used. The calves were fed with whole milk, milk replacer or fermented colostrum, plus starter (20.9±1.78% of CP). The accuracy of the average daily gain (ADG) prediction was evaluated by mean bias, mean square prediction error (MSPE), concordance correlation coefficient, bias correction factor (Cb), and regression between the observed and predicted values. The ADG observed from birth to weaning was 0.452±0.121 kg/day. Calves fed with whole milk had greater ADG compared with calves fed milk replacer (0.477 v. 0.379 kg/day) during the milk-feeding period. When all data were pooled (n=51 diets), predictions had a mean bias of −0.019 and 0.068 kg/day for energy-allowable gain using NRC and AMTS models, respectively. The regression equation between observed and predicted values obtained from energy of diets showed an intercept different from zero (P<0.0001) and slope that differed from unity (P<0.0001). In a second evaluation, when calves were fed only milk replacer, the energy-allowable gain from AMTS showed the lowest mean bias (0.008 kg/day) and 82.1% of the MSPE value originated from random errors. The lowest MSPE, the higher Cb value and no significant slope bias (P>0.05) indicate that the AMTS growth model resulted in accurate predictions for calves fed with milk replacer. However, within these latter two approaches, the goodness of fit (R²) was low, representing low precision. The weight gain estimated by the energy available from the diet was overestimated by 19 g/day when calculated by the NRC and underestimated by 68 g/day when calculated by AMTS. The reasons for this discrepancy need to be understood, for only then new models could be developed and parameterized to estimate animal performance in tropical conditions more accurately and precisely.     

Increased body condition score through increased lean muscle,but not fat deposition,is associated with reduced reproductive response to oestrus induction in beef cows

Energy reserve, estimated as body condition score (BCS), is the major determinant of the re-initiation of ovarian activity in postpartum cows. Leptin, IGF-I and insulin are positively related to BCS and are putative mediators between BCS and reproductive function. However, when BCS and body composition dissociates, concentrations of these metabolic hormones are altered. We hypothesized that increasing lean muscle tissue, but not fat tissue, would diminish the reproductive response to oestrus induction treatments. Thirty lactating beef cows with BCS of 3.10±1.21 and 75.94±12 days postpartum were divided in two groups. Control cows (n=15) were supplemented with 10.20 kg of concentrate daily for 60 days. Treated cows (n=15) were supplemented equally, and received a β-adrenergic receptor agonist (β-AA; 0.15 mg/kg BW) to achieve accretion of lean tissue mass and not fat tissue mass. Twelve days after ending concentrate supplementation/β-AA treatment, cows received a progestin implant to induce oestrus. Cows displaying oestrus were inseminated during the following 60 days, and maintained with a fertile bull for a further 21 days. Cows in both groups gained weight during the supplementation period (Daily weight gain: Control=0.75 kg v. β-AA=0.89 kg). Cows treated with β-AA had a larger increase in BCS (i.e. change in BCS: control=1 point (score 4.13) v. β-AA=2 points (score 5.06; P<0.05), as a result of muscle accretion (i.e. change in muscle depth: control 0.21 cm v. β-AA 0.97 cm; P<0.05) but not adipose tissue (i.e. change in back fat depth; control 0.13 cm v. β-AA −0.06 cm; P<0.05). The changes in body composition in β-AA cows were associated with a reduction in serum concentrations of IGF-I (25.4%) and leptin (27.9%), without observed changes in insulin. Ovulation and pregnancy to 1st service (P>0.05) did not differ between groups. However, the number of cows displaying oestrus (control 13/15 v. β-AA 8/15; P<0.05) and the percentage cycling (control 6/8 v. β-AA 3/10; P=0.07) after progestin treatment and the pregnancy percentage at the end of the breeding period (control 13/15 v. β-AA 8/15; P<0.05) were lower in β-AA than control cows. In summary, the increase BCS through muscle tissue accretion, but not through fat tissue accretion, resulted in a lower response to oestrus induction, lower percentage of cycling animals and lower pregnancy percentage after progestin treatment; which was associated with a decrease in serum concentrations of leptin and IGF-I.