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.     

Physiological and behavioural responses of cows from two beef breeds submitted to different suckling strategies

This experiment was designed to study the effects of avoiding calf contact and genotype on the metabolic, behavioural and reproductive traits of beef cows during lactation. Fifty-two multiparous cows, 25 Parda de Montaña (PA) and 27 Pirenaica (PI), fed at maintenance were assigned from the day after calving to twice-daily nursing (2× 30-min sessions at 0800 and 1600 h) either with fence contact with their calves (partial contact, PC) or without visual, tactile and olfactory contact (non-contact, NC) between suckling periods. Blood samples were collected to analyse metabolites (triglycerides, cholesterol, non-esterified fatty acids (NEFA), β-hydroxybutyrate and urea) and progesterone at different intervals. Cow–calf behaviour was monitored on weeks 4, 9 and 15 of lactation. Cow activity at oestrus was recorded through collars. Cows from both treatments and breeds showed similar live-weight gains during the first three months post-partum (P > 0.10). Milk yield and calf gains were not affected by treatment (P > 0.10) but they were greater in PA than in PI (P < 0.05). Plasma triglycerides and urea in the cows were not affected either by calf contact, breed or week post-partum (P > 0.10). Plasma cholesterol increased from week 6 post-partum onwards in PA cows (P < 0.05) while this rise was delayed to week 7 of lactation in PI breed (P < 0.05). Plasma NEFA was greater in blood from PC–PA cows than in the rest of groups (P < 0.05), and these metabolites were greater on week 1 and lower on week 11 than in rest of samplings (P < 0.05). Plasma β-hydroxybutyrate was not affected by either calf contact or breed (P > 0.10), but it was greatest on weeks 1–3 than in the rest of lactation (P < 0.05). Cows with PC calves took less time to first contact after they entered the barn than their NC counterparts (P < 0.05). Dams from both contact treatments nursed their offspring and remained in close proximity for similar time within suckling periods (P > 0.10). PA cows devoted more time than PI ones to lick their young (P < 0.001). There were no differences throughout lactation in any of the studied maternal behaviours (P > 0.10). Calf contact and breed did not affect the interval to first post-partum ovulation or oestrus in these cows (P > 0.10). Under twice-daily nursing conditions, the limitation of visual, tactile and olfactory contact with calves did not trigger different maternal or reproductive traits in these breeds but only a slightly higher mobilisation of body fat substrates in Parda de Montaña compared to Pirenaica.     

Effect of roughage level in a total mixed ration on feed intake, ruminal fermentation patterns and chewing activity of early-weaned calves with ad libitum access to grass hay

In this study, two total mixed rations (TMR, based on dry ingredients) consisting (per kg dry matter (DM)) of 300 or 400 g finely chopped hay mixture of grass and alfalfa (H30 versus H40) were compared concerning their effects on dry matter intake (DMI), ruminal fermentation patterns and chewing activity of early-weaned (8 weeks milk-fed) calves. Ten ruminally cannulated male German Holstein calves were randomly assigned to two dietary treatments (n = 5) and observed from an age of 8–15 weeks. One group received the H30 (11.3 MJ metabolizable energy (ME)/kg DM) and the other the H40 (10.7 MJ ME/kg DM) TMR. All calves received grass hay (9.0 MJ ME/kg DM) separately. Water, TMR and hay were offered ad libitum twice daily (08:00 and 16:00 h). Rumen fluid was collected via cannula at an age of 9, 11, 13 and 15 weeks, twice weekly just prior to as well as 1, 3, 5 and 7 h after morning feeding. Chewing activity was recorded by a special head collar. As the calves aged DMI increased rapidly congruent with the recommended range for weaned calves. Because of the differing energy supply, calves receiving the H30 TMR were heavier than calves receiving the H40 TMR (139 kg versus 123 kg, P=0.007). During the trial ruminal pH of all calves were within the target range (6.2 ± 0.5), indicating physiological ruminal fermentation patterns. Daily mean ruminal pH was uninfluenced by treatment, however at an age of 13 and 15 weeks H30 showed a higher short chain fatty acid (SCFA) level than H40 (P=0.098; P=0.036). At an age of 15 weeks H30 showed a critical decrease in ruminal pH (3 h after feeding: 5.7) corresponding to a higher ruminal SCFA concentration (148.2 mmol/L, P=0.007). Chewing activity was well developed at an early age due to an increasing DMI after weaning. At an age of 15 weeks chewing activity (per day: 613–743 min total chewing; 358–418 min rumination) was similar to that of adult cows. In summary, feeding a dry TMR consisting per kg DM of 300–400 g hay to early-weaned calves can be recommended for a successful calf rearing up to an age of 15 weeks.     

Extended transition milk feeding for 3 weeks improves growth performance and reduces the susceptibility to diarrhea in newborn female Holstein calves

Dairy calves may benefit from extending the duration of feeding transition milk (TM; the subsequent two to six milkings after parturition) to enhance performance and health during early life. The objective of this study was to assess the effect of replacing pasteurized waste milk (non-saleable milk containing antibiotic and/or drug residues) with pasteurized TM for 3 weeks on the growth performance and health of dairy calves. A total of 84 healthy newborn female Holstein calves were blocked by birth order and assigned randomly to 4 treatment groups with partial replacement of pasteurized waste milk by TM (second milkings after parturition) at 0 (0 l/day TM + 6 l/day milk), 0.5 (0.5 l/day TM + 5.5 l/day milk), 1 (1 l/day TM + 5 l/day milk), or 2 l (2 l/day TM + 4 l/day milk) for a 21-day period. From day 22 onward, all calves were fed individually with 6 l/day pasteurized waste milk. Calves were weaned on day 60 and monitored until day 90 of the study. Liquid feed DM intake (DMI) was increased with increasing levels of TM (P = 0.001). Starter feed DMI and total DMI (liquid feed DMI + starter feed DMI) were not affected by the treatment effect. Calves were fed 2 l/day TM gained more BW compared with those in the control group during the postweaning and overall periods. The average daily gain tended (P = 0.06) to be higher in calves fed 2 l/day TM compared with calves fed 0 (+ 65 g/day), 0.5 (+ 53 g/day), or 1 (+ 76 g/day) l/day TM during the preweaning period. Daily weight gain was also higher in calves fed 2 l/day TM compared with calves in the control group during the postweaning (+ 137 g/day; P = 0.04) and overall (+ 89 g/day; P < 0.01) periods, respectively. Calves fed 2 l/day TM had a higher feed efficiency compared with calves in the control group during all studied periods. The calves fed TM2 had a lower chance of having diarrhea compared with other treatment groups. Duration but not the frequency of diarrhea was lower in calves fed TM2 vs TM0 (2.5 vs 4.2 days; P = 0.03). In general, partial replacement of waste milk with TM (2 l/day) may be recommended to feed dairy calves at an early stage of life to support a higher growth rate and health benefits.     

Effect of suckling restriction with nose plates and premature weaning on postpartum anestrous interval in primiparous cows under range conditions

Suckling and nutrition are generally recognized as two major factors controlling the duration of the postpartum anovulatory period. In the present study, the effect of premature weaning and suckling restriction with nose plates (NPs) on cow and calf performance was evaluated. The study was conducted over 2 years; primiparous Hereford cows, weighing (mean ± S.E.M.) 344 ± 3.5 kg and with 4.1 ± 0.05 units of body condition score (BCS) (scale 1–8 [Vizcarra, J.A., Ibañez, W., Orcasberro, R., 1986. Repetibilidad y reproductibilidad de dos escalas para estimar la condición corporal de vacas Hereford. Investigaciones Agronómicas 7 (1), 45–47]) at calving, remained with their calves until 72.5 ± 1.2 days postpartum (day 0). They were then assigned to one of three treatments: (i) calves with free access to their dams and ad libitum suckling (S, n = 29); (ii) calves fitted with NPs for 14 days, but remained with their dams (NP, n = 29), and (iii) calves that were weaned from their dams (W, n = 28). All cows were anestrus at the time treatments commenced (day 0). All cows were blood sampled twice weekly from 1 week before the beginning of the experiment until the end of the mating period (day 74) for progesterone analysis. The mating period began on day 14. Cows in W treatment had ovulations earlier (P < 0.05) than those in NP and S groups. Cows in the NP group had longer (P < 0.05) intervals between the first progesterone increase and normal luteal phase than cows in the other two treatments groups (23.3 ± 3.2 vs. 6.5 ± 3.2 and 5.2 ± 3.3 days for NP, S and W cows, respectively). Fifty per cent of the cows with NP had a short cycle (7 days) but there was a group of cows that had longer (P < 0.05) intervals (66 days) between first progesterone increase and normal estrous activity. In the NP group, 8 of 29 cows had a short luteal phase and then a normal one; for 9 of these 29 cows progesterone concentrations remained low for 6 weeks from the beginning of the treatment; and for 12 of these 29 cows progesterone concentrations initially increased after treatment initiation, but these animals became anestrus thereafter. Short-term suckling restriction with NPs led to a variable response in primiparous cows of moderate body condition under range conditions.     

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.     

Impact of volume,immunoglobulin G concentration,and feeding method of colostrum product on neonatal nursing behavior and transfer of passive immunity in beef calves

One-third of beef calves fail to achieve adequate transfer of passive immunity (TPI) through timely ingestion of colostrum, which substantially increases their risk of preweaning morbidity and mortality. Two randomized clinical trials were designed to assess the impact of volume, immunoglobulin G (IgG) concentration, and feeding method of colostrum product on neonatal nursing behavior and TPI. In Trial 1, 47 calves were randomly assigned to receive one of three colostrum interventions by oro-esophageal tube feeder (OET): 1 L with 100 g/L IgG, 1.4 L with 70 g/L IgG, or 2 L with 100 g/L IgG. In Trial 2, 29 calves were randomly assigned to be fed 1 L of colostrum product with 100 g/L IgG by either nipple bottle (NB) or OET. Colostrum intervention (i.e. feeding of colostrum product) occurred within 60 minutes of birth. Cow-calf pairs were monitored by video surveillance in individual stalls for 24 h. Dam colostrum was collected at 10 minutes and calf serum was collected at 24–36 h after birth to assess IgG concentration. Differences among colostrum intervention groups on latency to stand and nurse were analyzed using Kaplan-Meier survival curves and Cox proportional hazard models. The impact of colostrum intervention group on TPI was assessed using multivariable linear regression modeling. In Trial 1, calves fed 1.4 L with 70 g/L IgG by OET nursed from their dams statistically significantly earlier compared to calves fed 1 L with 100 g/L IgG (P = 0.003) and calves fed 2 L with 100 g/L IgG (P = 0.008). Six of the 15 calves in the NB group in Trial 2 refused to consume part of the colostrum feeding offered by bottle and required follow-up tube feeding of the remaining volume. These calves were analyzed as a separate group (NB + OET). Calves fed 1 L by NB stood and nursed statistically significantly earlier than calves fed by OET (P = 0.005) or a combination of NB + OET (P = 0.003). Calf serum IgG concentrations were not statistically significantly different among colostrum intervention groups (P > 0.1). Overall, the colostrum interventions assessed in this study led to only one calf with failed TPI. While statistically significant differences in serum IgG concentrations were not detected in this study, subsequent nursing behavior did vary and was improved by feeding a moderate volume (1.4 L with 70 g/L IgG) of colostrum when using an OET, and by using the NB when feeding a smaller volume (1 L with 100 g/L IgG).     

The formation of preferential relationships at early age in cattle

Calves can develop long-lasting social relationships with peers. We examined the strength of the relationships between calves according to the time they had been together. Twenty-four female dairy calves were assigned to six groups of four animals (Type-1 partners) at 0.5 month of age. At 3.5 months of age, they were mixed with other calves (Type-2 partners) to form groups of 14. Type-3 partners were calves added to the experimental groups after 5.25 months. The calves stayed together until 1.5 years of age. Social preferences between the three partner types were examined in a Y-maze, and the position and activity of animals in the barn and pasture were followed in three periods. Behavioural synchrony, distance between animals, proximity and nearest neighbour were analysed. The calves more frequently butted Type-3 than Type-1 partners in the Y-maze (P < 0.05). They spent more time in proximity to Type-1 partners, and these were more often the nearest neighbours than other partners (P < 0.001). Synchrony and distance between animals were greater at pasture than in the barn (P < 0.01). Calves seem to form preferential relationships before 3.5 months of age. Keeping cattle together from an early age seems beneficial for them.     

Effects of different forms of Acacia saligna leaves inclusion on feed intake, digestibility and body weight gain in lambs fed grass hay basal diet

The study was undertaken to determine the effects of different forms of Acacia saligna leaves inclusion on feed intake, digestibility and body weight gain in lambs fed grass hay basal diet. Twenty local ‘Farta’ yearling male lambs weighing 17.4 ± 0.10 kg (mean ± SD) were randomly allocated to four dietary treatments consisting of daily feeding of lambs in T1 with 700 g grass hay (dry matter basis), and daily free choice feeding of lambs in T2, T3, and T4 with 700 g grass hay + 700 g fresh, wilted, and dried A. saligna leaves, respectively. Inclusion of different forms of A. saligna leaves improved (P<0.01) the daily intake of total DM by 8–9% and that of OM and CP by 7 and 38%, respectively compared to the control. The daily intake of NDFom was lower (P<0.01) by 1–2.3%, whereas that of the ADFom intake declined (P<0.01) by 1.3–3.4% for lambs on wilted and dried forms of A. saligna leaves. Inclusion of A. saligna leaves replaced the intake of the grass hay by 26–27% of the total diet and reduced (P<0.05) apparent digestibility coefficient of the total DM by 9, 7, and 4%, OM by 7, 6 and 4%, and CP by 12, 12, and 9%, but improved (P<0.05) apparent digestibility coefficient of NDFom by 3–4% compared to the control diet. Dried A. saligna leaves improved (P<0.05) apparent digestibility of DM, OM and CP compared to fresh A. saligna leaves. Lambs fed on hay alone lost (P<0.05) body weight, while the lambs supplemented with A. saligna leaves gained (P<0.05) weight. The results of this study revealed that A. saligna leaves could be best included in the grass hay based feeding in dried form at the rate of 265 g/kg DM for improved nutrient utilization and growth performance of yearling lambs.     

The effect of calf jacket usage on performance,behaviour and physiological responses of group-housed dairy calves

Poor performance and ill-health of calves in the pre-wean period can affect future productivity. Increasing numbers of producers are opting to use calf jackets as a means of mitigating the potential negative effects of low ambient temperatures, wind speed and precipitation on growth and health. This study aimed to use a range of noninvasive monitoring technologies to investigate the effects of using calf jackets in the first 3 weeks of life on calf performance and behavioural and physiological parameters. Ninety Holstein-Friesian calves were allocated to one of the two treatments: (i) Jacketed until 21 days of age and (J; n = 44) ii. Nonjacketed (NJ; n = 46). Calves were group housed and fed milk replacer (MR) and concentrate solid feed via automatic feeders. Calves were weaned at day 56, and the experiment was completed at day 63. Health assessments were conducted on a daily basis throughout the experiment using predefined faecal and respiratory scoring protocols. A range of novel, noninvasive monitoring technologies were used to examine the activity, heart rate and thermal profiles of calves on an individual basis throughout the experimental period. There were no differences in calf live weight (LWT), average daily gain (ADG) or feed conversion efficiency (FCE) in J and NJ calves between days 5 to 20. However, NJ calves consumed more MR and had more unrewarded visits to the milk feeder than J calves during this period. Although calf LWT was comparable across treatments in the week following jacket removal (days 21 to 28), both ADG and FCE tended to be greater in NJ calves. There were no treatment differences in calf LWT at the end of the study (d63). When measured over a period of 24 h and at a mean ambient temperature of 7.7°C, skin surface temperature was 6.37°C higher in J calves. Core body temperature was higher in J calves between days 5 to 20; however, there were no differences in IR eye or IR rectal temperature. No differences in lying behaviour occurred, with calves spending 18 and 17 h/day lying between days 5 to 20 and days 21 to 28, respectively. Under the climatic and management conditions described, no significant benefits to calf performance were found as a result of the provision of calf jackets to group-housed calves in the first 3 weeks of life. The higher frequency of unrewarded visits to the milk feeder in NJ calves during the first 3 weeks of life could be suggestive of a lack of satiety in these calves.     

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.     

Combined effect of probiotics and specific immunoglobulin Y directed against Escherichia coli on growth performance,diarrhea incidence,and immune system in calves

Enterotoxigenic Escherichia coli (ETEC) K99 is one of the major pathogens associated with calf diarrhea. The induction of passive immunity in animals by immunoglobulin Y and using probiotics are inexpensive alternatives to antibiotics for the prevention and treatment of a number of bacterial infections, including diarrhea. Hence, the aim of this research was to evaluate the impact of dietary probiotics and ETEC K99-specific egg yolk antibody supplements, alone and in combination with each other, on health and growth parameters, diarrhea incidence and immune stimulation in newborn Holstein calves. One hundred and twenty neonatal calves were allocated randomly into 4 dietary groups (n = 30 per group) received colostrum/milk without any additives (control group), or supplemented with egg yolk powder contained E. coli K99-specific antibody (Ab group; 1 g/day), a commercial probiotic, Hypro-calves (Pro group; 3 g/day), and their combination (Ab + Pro group), from day (d) 1 to d28 of age. Analyses of the growth parameters, feed efficiency, fecal score, and microbiota and immune function were carried out on d0, 14, 21, and 28 of the experiment. Calves in Ab or Ab + Pro group had higher (P < 0.05) average daily gain compared to control and Pro groups during 0–14d. Feed efficiency of calves in Ab and Ab + Pro groups was significantly higher than that in control group during the period of 0–14d; however, no significant differences were observed in 0–28d period. Diarrhea prevalence and fecal score in Ab + Pro group were lower than control group (P < 0.05). Calves in Ab + Pro group had the lowest number of fecal E. coli in comparison to other groups on d28 (P < 0.05). Feeding Ab + Pro supplement increased (P < 0.05) concentrations of blood IgA and serum CD4 compared to the control group. Likewise, calves in Pro group had higher CD4 levels as compared to the control calves (P < 0.05). Serum concentration of interferon-gamma in control group was lower than other groups (P < 0.05). Overall, these data suggest that feeding a combination of probiotic and specific antibody against ETEC to neonate Holstein calves enhances feed efficiency, boosts immunity, and reduces diarrhea prevalence.     

Strategies to improve fertility in Bos indicus postpubertal heifers and nonlactating cows submitted to fixed-time artificial insemination

Two experiments were designed to evaluate strategies to increase fertility of Bos indicus postpubertal heifers and nonlactating cows submitted to a fixed-time artificial insemination (TAI) protocol consisting of an intravaginal device containing 1.9 g of progesterone (CIDR) insertion + estradiol benzoate on Day 0, CIDR withdrawal + estradiol cypionate on Day 9, and TAI on Day 11. In Experiment 1, heifers (n = 1153) received a new or an 18-d previously used CIDR and, on Day 9, prostaglandin F_2α (PGF_2α) + 0, 200, or 300 IU equine chorionic gonadotropin (eCG). Heifers treated with a new CIDR had greater (least squares means ± SEM) serum concentration of progesterone on Day 9 (3.06 ± 0.09 ng/mL vs. 2.53 ± 0.09 ng/mL; P < 0.05) and a smaller follicle at TAI (11.61 ± 0.11 mm vs. 12.05 ± 0.12 mm; P < 0.05). Heifers with smaller follicles at TAI had lesser serum progesterone concentrations on Day 18 and reduced rates of ovulation, conception, and pregnancy (P < 0.05). Treatment with eCG improved (P < 0.05) follicle diameter at TAI (11.50 ± 0.10 mm, 11.90 ± 0.11 mm, and 12.00 ± 0.10 mm for 0, 100, and 200 IU, respectively), serum progesterone concentration on Day 18 (2.77 ± 0.11 ng/mL, 3.81 ± 0.11 ng/mL, and 4.87 ± 0.11 ng/mL), and rates of ovulation (83.8%, 88.5%, and 94.3%) and pregnancy (41.3%, 47.0%, and 46.7%). In Experiment 2, nonlactating Nelore cows (n = 702) received PGF_2α treatment on Days 7 or 9 and, on Day 9, 0 or 300 IU eCG. Cows receiving PGF_2α on Day 7 had lesser serum progesterone concentrations on Day 9 (3.05 ± 0.21 ng/mL vs. 4.58 ± 0.21 ng/mL; P < 0.05), a larger follicle at TAI (11.54 ± 0.21 mm vs. 10.84 ± 0.21 mm; P < 0.05), and improved (P < 0.05) rates of ovulation (85.4% vs. 77.0%), conception (60.9% vs. 47.2%), and pregnancy (52.0% vs. 36.4%). Treatment with eCG improved (P < 0.05) serum progesterone concentration on Day 18 (3.24 ± 0.14 ng/mL vs. 4.55 ± 0.14 ng/mL) and the rates of ovulation (72.4% vs. 90.0%) and pregnancy (37.5% vs. 50.8%). In conclusion, giving PGF_2α earlier in the protocol in nonlactating cows and eCG treatment in postpubertal heifers and nonlactating cows improved fertility in response to a TAI (progesterone + estradiol) protocol.     

Influence of exogenous enzymes on nutrient digestibility, extent of ruminal fermentation as well as milk production and composition in dairy cows

This experiment studied effects of a mixture of exogenous enzymes (ZADO^®) from anaerobic bacteria on ruminal fermentation, feed intake, digestibility, as well as milk production and composition in cows fed total mixed rations (TMRs; 0.7 corn silage and 0.3 of a concentrate mixture). Twenty lactating multiparous Brown Swiss cows (500 ± 12.4 kg live weight) were randomly assigned into two experimental groups of 10 immediately after calving and fed a TMR with or without (CTRL) addition of 40 g/cow/d of enzymes for 12 weeks. Addition of enzymes increased (P<0.05) rumen microbial N synthesis. Intake of dry matter (DM) and organic matter (OM) was positively influenced (P<0.05) by supplementation, and digestibility of all nutrients was higher (P<0.05) in the total tract of supplemented cows, although the magnitude of the improvement varied among nutrients, with the highest improvement in aNDFom and ADFom (418–584 and 401–532 g/kg respectively; P<0.05) than the other nutrients. Supplementation of enzymes also increased (P<0.05) rumen ammonia N and total short chain fatty acid (SCFA) concentrations, and individual SCFA proportions were also altered with an increase in acetate (61.0–64.8 mol/100 mol; P=0.05) before feeding, and acetate and propionate increased 3 h post-feeding (60.0–64.0 and 18.3–20.8 mol/100 mol respectively; P<0.05). Milk and milk protein production was higher (12.8–15.7 and 0.45–0.57 kg/d respectively; P<0.05) for cows fed the ZADO^® supplemented diet. This exogenous enzyme product, supplemented daily to the TMR of cows in early lactation, increased milk production due to positive effects on nutrient intake and digestibility, extent of ruminal fermentation and microbial protein synthesis.     

The economic effects of an estrus synchronization protocol using prostaglandin in beef heifers

We estimated the effect of estrus synchronization on reproduction, production and economic outcomes in 272 beef heifers randomly allocated to a synchronized Test group or an unsynchronized Control group. The Test group received AI upon estrus detection for 6 days followed by PGF2 treatment of heifers that had not shown estrus by day 6 (PGF/6). In both groups AI was continued for 50 days, followed by a 42-day bull breeding period. Heifers were followed through their second breeding season and until they had weaned their first calves. Synchronization resulted in a reduction in median days to first insemination (8 vs. 11 in the Test and Control groups, respectively, P < 0.01) and median days to calving of calves born to AI (14 vs. 20, P = 0.04). There was no significant difference in pregnancy rate to the AI period (60.0% vs. 51.8%, P = 0.18), final pregnancy rate (82.2% vs. 83.2%, P = 0.87) or pregnancy rate to the subsequent breeding season (96.0% vs. 95.0%, P = 1.00). Although mean calf weaning mass was not significantly different (207.0 kg vs. 201.4 kg, P = 0.32), the total mass of calves weaned in this study was 14,843 kg vs. 13,060 kg and the benefit: cost ratio for synchronization was 2.8. It was therefore concluded that a PGF/6 protocol may affect the total mass of calves weaned by changing days to calving, weaning rate, the ratio of male: female calves born and/or the birth mass of calves.     

The effect of early human contact and the separation method from the dam on responses of beef calves to humans

The objectives of this experiment were to evaluate the effect of early human contact and of the separation method from the dam on the future relationships of calves with humans, and to investigate the relationship between dam responses and calf responses. Thirty-three Salers calves aged 2–4 days old and reared outdoors were split into 3-week treatments balanced according to sex and birth dates. Group 1 (long separation from the dam and human contact: LS + H; n = 11) underwent 8 h of separation from the dam per day and 5 min of individual stroking; group 2 (short separation from the dam and human contact: SS + H; n = 11) underwent 1 h of separation and the same amount of human contact as LS + H calves. Group 3 (short separation from the dam and no human contact: SS − H; n = 11) was a control group undergoing the same duration of separation as SS + H but without stroking. At 3, 15 and 45 weeks of age, the calves were tested in a standard arena test (AT) where they were successively left alone (2 min), left with a stationary human (5 min), and left with a human approaching and touching them (2 min). At 15 and 45 weeks, the calves were also tested with the standard docility test (DT: test of restraint). The dams were also tested with DT 2 months before calving. Data analysis via Mann–Whitney tests and Spearman's correlations showed no significant effect of the duration calves were separated from their dams. Just after treatment at 3-week of age, calves given stroking (LS + H and SS + H) were more motionless and more willing to accept human contact (AT: touching) than control calves (SS − H, P < 0.01). At 45 weeks of age, calves given stroking spent also significantly more time (P < 0.05) motionless with the approaching human compared to non-stroked calves (SS − H), suggesting a persistent effect. However, this effect was not reproduced on the other behavioural criteria recorded (e.g., duration of human contact or docility score). In the different tests and at the different ages, the docility scores of the dams were significantly correlated (up to 0.7, P < 0.01) with behaviour towards humans shown by stroked calves but not non-stroked calves (SS − H). Our results suggest that additional human contact at early age, but not duration of the separation from the dam, could be beneficial for the human–animal relationship, but only for calves born to docile dams.     

Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Effects of inclusion of neutral detergent soluble fibre sources in diets varying in forage particle size on feed intake, digestive processes, and performance of mid-lactation Holstein cows

The aim of this study was to evaluate effects of partial replacement of neutral detergent soluble fibre (NDSF) for starch in diets varying in particle size (PS) of alfalfa hay on chewing activities, ruminal fermentation, nutrient digestibility and performance in mid-lactation dairy cows. Eight multiparous Holstein cows (146 ± 6.0 d in milk; 36.7 ± 2.57 kg milk/d) were used in a replicated 4 × 4 Latin square design with four 21 d periods with the last 7 d for data collection. The experiment was a 2 × 2 factorial arrangement with 2 levels of NDSF (low = 85 g/kg or high = 130 g/kg diet dry matter) each combined with 2 PS (short = 20 mm or long = 40 mm) of alfalfa hay. Results show that forage PS alone, or in combination with NDSF inclusion, had no effect on dry matter (DM) intake. Although total chewing, eating and ruminating times were not affected by treatments, eating time per kg of neutral detergent fibre (NDF) ingested was higher in long versus short alfalfa hay-based diets (P<0.05). Feeding long forage PS increased sorting of the diet against particles >19 mm, and in favor of those <8 mm (P<0.05). Feeding diets high in NDSF lowered DM intake (P<0.05), but increased apparent digestibility of all nutrients including NDF (P<0.05) independent of forage PS. Ruminal pH and concentrations of total volatile fatty acids were unaffected by dietary treatments, however the proportion of butyrate was higher in ruminal fluid of cows fed high NDSF diets (P<0.05). Changes in milk composition included lower milk crude protein content in high NDSF diets and higher lactose content for short hay-based diets (P<0.05). That milk yield and milk energy output were similar in low versus high NDSF diets suggests that high NDSF-fed cows had higher energy efficiency due to lower DM intake. Results suggest that, independent of forage PS, NDSF sources can be successfully included to partly replace starchy grains in diets exceeding minimum fibre recommendations.     

The effects of feeding high or low milk levels in early life on growth performance,fecal microbial count and metabolic and inflammatory status of Holstein female calves

Gut microbial colonization and immune response may be affected by milk feeding method. The objective of this study was to determine the effects of feeding high or low volumes of milk on fecal bacterial count, inflammatory response, blood metabolites and growth performance of Holstein female calves. Colostrum-fed calves (n = 48) were randomly assigned to either high milk (HM; n = 24) or low milk (LM; n = 24) feeding groups. Low milk-fed calves were fed pasteurized whole milk at 10% of BW until weaning. In HM group, milk was offered to calves at 20% of BW for the first 3 weeks of life. Then, milk allowance was decreased gradually to reach 10% of BW on day 26 and remained constant until weaning on day 51. Calves were allowed free access to water and starter throughout the experiment. Body weight was measured weekly, and blood samples were taken on days 14, 28 and 57. Fecal samples were collected on days 7, 14 and 21 of age for the measurement of selected microbial species. By design, HM calves consumed more nutrients from milk during the first 3 weeks and they were heavier than LM calves on days 21, 56 and 98. High milk-fed calves had greater serum glucose and triglyceride levels on day 14 with no significant difference between groups on days 28 and 57. Blood urea nitrogen was higher in LM calves on day 14, but it was lower in HM calves on day 28. Calves in LM group had significantly greater blood tumor necrosis factor-α (TNF-α) than HM calves throughout the experiment. Serum amyloid A (SAA) concentration was higher in LM calves on day 14. However, HM calves showed higher levels of SAA at the time of weaning. Feeding high volumes of milk resulted in lower serum cortisol levels on days 14 and 28 but not at the time of weaning in HM calves compared to LM counterparts. Lactobacillus count was higher in feces sample of HM calves. Conversely, the numbers of Escherichia coli was greater in the feces of LM calves. Calves in HM group showed fewer days with fever and tended to have fewer days treated compared to LM group. In conclusion, feeding higher amounts of milk during the first 3 weeks of life improved gut microbiota, inflammation and health status and growth performance of Holstein dairy calves.     

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.