Calving traits, milk production, body condition, fertility, and survival of Holstein-Friesian and Norwegian Red dairy cattle on commercial dairy farms over 5 lactations.

The objective of this study was to compare calving traits, BCS, milk production, fertility, and survival of Holstein-Friesian (HF) and Norwegian Red (NR) dairy cattle in moderate-concentrate input systems. The experiment was conducted on 19 commercial Northern Ireland dairy farms, and involved 221 HF cows and 221 NR cows. Cows completed 5 lactations during the experiment, unless they died or were culled or sold. Norwegian Red cows had a lower calving difficulty score than HF cows when calving for the first and second time, but not for the third and fourth time. At first calving, the incidence of stillbirths for NR cows was 4%, compared with 13% for HF cows, whereas no difference existed between breeds in the proportion of calves born alive when calving for the second time. When calving for the first time, NR cows had a poorer milking temperament than HF cows, whereas milking temperament was unaffected by breed following the second calving. Holstein-Friesian cows had a higher full-lactation milk yield than NR cows, whereas NR cows produced milk with a higher milk fat and protein content. Full-lactation fat + protein yield was unaffected by genotype. Norwegian Red cows had a lower somatic cell score than HF cows during all lactations. Although NR cattle had a higher BCS than the HF cows during lactations 1 and 2, no evidence existed that the 2 genotypes either lost or gained body condition at different rates. Conception rates to first artificial insemination were higher with the NR cows during lactations 1 to 4 (57.8 vs. 40.9%, respectively), with 28.5% of HF cows and 11.8% of NR cows culled as infertile before lactation 6. A greater percentage of NR cows calved for a sixth time compared with HF cows (27.2 vs. 16.3%, respectively). In general, NR cows outperformed HF cows in traits that have been historically included in the NR breeding program.

The effect of calf nutrition on the performance of dairy herd replacements.

Sixty-five Holstein-Friesian calves were randomly allocated to one of eight nutritional treatments at 4 days of age. In this factorial design study, the treatments comprised of four levels of milk replacer (MR) mixed in 6 l of water (500, 750, 1000 and 1250 g/day) × two crude protein (CP) concentrations (230 and 270 g CP/kg dry matter (DM)). MR was fed via automatic teat feeders and concentrates were offered via automated dispensers during the pre-wean period. MR and calf starter concentrate intake were recorded until weaning with live weight and body measurements recorded throughout the rearing period until heifers entered the dairy herd at a targeted 24 months of age. There was no effect of MR protein concentration on concentrate or MR intake, and no effect on body size or live weight at any stage of development. During the pre-weaning period, for every 100 g increase in MR allowance, concentrate consumption was reduced by 39 g/day. While, for every 100 g increase in the amount of MR offered, live weight at days 28 and 270 increased by 0.76 and 2.61 kg, respectively (P < 0.05). Increasing MR feed levels increased (P < 0.05) heart girth and body condition score at recordings during the first year of life, but these effects disappeared thereafter. Increasing MR feeding level tended to reduce both age at first observed oestrus and age at first service but no significant effect on age at first calving was observed. Neither MR feeding level nor MR CP content affected post-calving live weight or subsequent milk production. Balance measurements conducted using 44 male calves during the pre-weaning period showed that increasing milk allowance increased energy and nitrogen (N) intake, diet DM digestibility, true N digestibility and the biological value of the dietary protein. Increasing the MR protein content had no significant effect on the apparent digestibility of N or DM.

Food intake, milk production, and tissue changes of Holstein-Friesian and Jersey × Holstein-Friesian dairy cows within a medium-input grazing system and a high-input total confinement system.

Although interest in crossbreeding within dairy systems has increased, the role of Jersey crossbred cows within high concentrate input systems has received little attention. This experiment was designed to examine the performance of Holstein-Friesian (HF) and Jersey × Holstein-Friesian (J × HF) cows within a high concentrate input total confinement system (CON) and a medium concentrate input grazing system (GRZ). Eighty spring-calving dairy cows were used in a 2 (cow genotype) × 2 (milk production system) factorial design experiment. The experiment commenced when cows calved and encompassed a full lactation. With GRZ, cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio] until turnout, grazed grass plus 1.0 kg of concentrate/day during a 199-d grazing period, and grass silage and concentrates (75:25 DM ratio) following rehousing and until drying-off. With CON, cows were confined throughout the lactation and offered diets containing grass silage and concentrates (DM ratio; 40:60, 50:50, 40:40, and 75:25 during d 1 to 100, 101 to 200, 201 to 250, and 251 until drying-off, respectively). Full-lactation concentrate DM intakes were 791 and 2,905 kg/cow for systems GRZ and CON, respectively. Although HF cows had a higher lactation milk yield than J × HF cows, the latter produced milk with a higher fat and protein content, so that solids-corrected milk yield (SCM) was unaffected by genotype. Somatic cell score was higher with the J × HF cows. Throughout lactation, HF cows were on average 37 kg heavier than J × HF cows, whereas the J × HF cows had a higher body condition score. Within each system, food intake did not differ between genotypes, whereas full-lactation yields of milk, fat plus protein, and SCM were higher with CON than with GRZ. A significant genotype × environment interaction was observed for milk yield, and a trend was found for an interaction with SCM. Crossbred cows on CON gained more body condition than HF cows, and overall pregnancy rate was unaffected by either genotype or management system. In summary, milk and SCM yields were higher with CON than with GRZ, whereas genotype had no effect on SCM. However, HF cows exhibited a greater milk yield response and a trend toward a greater SCM yield response with increasing concentrate levels compared with the crossbred cows.

An evaluation of the effect of altering nutrition and nutritional strategies in early lactation on reproductive performance and estrous behavior of high-yielding Holstein-Friesian dairy cows.

Reproductive performance in the high-yielding dairy cow has severely decreased in the last 40 yr. The aim of this study was to compare the effectiveness of 4 nutritional strategies in improving the reproductive performance of high-yielding dairy cows. It was hypothesized that offering cows a high-starch ration in early lactation would enhance the onset of luteal activity, and that decreasing the severity of negative energy balance in the early postcalving period would improve reproductive parameters. Nutritional regimens aimed at improving fertility were applied to 96 Holstein-Friesian dairy animals. Upon calving, animals were allocated in a balanced manner to one of 4 dietary treatments. Primiparous animals were balanced according to live weight, body condition score and calving date. Multiparous animals were balanced according to parity, previous lactation milk yield, liveweight, body condition score and calving date. Treatment 1 was based on an industry best practice diet (control) to contain 170 g of crude protein/kg of dry matter. Treatment 2 was an individual cow feeding strategy, whereby the energy balance (EB) of individual animals was managed so as to achieve a predetermined target daily EB profile (±10 MJ/d). Treatment 3 was a high-starch/high-fat combination treatment, whereby an insulinogenic (high-starch) diet was offered in early lactation to encourage cyclicity and followed by a lipogenic (low-starch, high-fat) diet to promote embryo development. Treatment 4 was a low-protein diet, containing 140 g of crude protein/kg of dry matter, supplemented with protected methionine at an inclusion level of 40 g per animal per day. The nutritional strategies implemented in this study had no statistically significant effects on cow fertility measures, which included the onset of luteal activity, conception rate, in-calf rate, and the incidence of atypical cycles. The individual cow feeding strategy improved EB in early lactation but had no benefit on conception rate to first insemination. However, conception rate to second insemination, 100-d pregnancy rate (from the commencement of breeding), and overall pregnancy rate tended to be higher in this group. The high-starch/high-fat treatment tended to decrease the proportion of delayed ovulations and increase the proportion of animals cycling by d 50 postcalving. Animals that failed to conceive to first insemination had a significantly longer luteal phase in the first cycle postpartum and a longer inter-ovulatory interval in the second cycle postpartum. With regards to estrous behavior, results indicate that as the size of the sexually active group increased, the intensity of estrus and the expression of mounting or attempting to mount another cow also increased. Furthermore, cows that became pregnant displayed more intense estrous behavior than cows that failed to become pregnant.

Effect of precalving and postcalving dietary energy level on performance and blood metabolite concentrations of dairy cows throughout lactation.

The effects of the level of energy intake (high E and low E) offered before and after calving on body condition score at calving, production performance, and energy status in the first 250 d of lactation were evaluated in a 2 × 2 factorial design experiment involving 80 Holstein-Friesian dairy animals (40 primiparous and 40 multiparous). From d 80 until d 21 precalving, primiparous animals were offered either high or low pasture allowances. Thereafter, these animals were housed and had ad libitum access to a high energy density diet (high E) or restricted access [6 kg of dry matter (DM) per d] to a low energy density diet (low E), respectively, until calving. From d 100 until d 42 precalving, multiparous animals were offered either ad libitum or restricted (10 kg of DM/d) access to a late lactation diet, and thereafter, had ad libitum access to a high E diet or restricted access (7 kg of DM complete diet/d) to a low E diet, respectively, until calving. The forage to concentrate (F:C) ratios (DM basis) of these high E and low E diets [d 42 (d 21 in primiparous animals) until calving] were 64:36 and 83:17, respectively. Cows offered high E and low E precalving diets were allocated to either a high E or low E postcalving diet [F:C ratio (DM basis) of 30:70 and 70:30, respectively] and remained on these diets until d 250 of lactation. Multiparous animals offered a high E diet precalving had a significantly higher body condition score at calving than those offered the low E diet precalving. This effect was not evident in primiparous animals. Precalving diet had no significant effect on plasma nonesterified fatty acid concentrations during the last 3 wk precalving in primi- or multiparous animals. Primiparous animals offered a high E diet precalving had significantly higher postcalving plasma concentrations of nonesterified fatty acid, suggesting greater mobilization of body reserves. Primi- and multiparous animals offered a high E diet postcalving had a significantly higher dry matter intake, milk yield, and energy status postcalving compared with animals offered a low E diet postcalving. Milk yields of primiparous animals offered high E and low E diets postcalving were 29.7 and 24.8 kg/d, respectively, and milk yield of multiparous animals offered high E and low E diets postcalving were 33.5 and 28.2 kg/d, respectively. It is concluded that altering body condition score during the dry period is difficult but that specific dietary regimens applied precalving can have a significant influence on postcalving production and energy-related parameters.

Effects of dam breed and dietary source of n-3 polyunsaturated fatty acids on the growth and carcass characteristics of lambs sourced from hill sheep flocks.

The objectives of this study were to investigate the effect of dietary lipid source on the growth and carcass characteristics of lambs sourced from a range of crossbred hill ewes. Over a 2-year period, 466 lambs representing the progeny of Scottish Blackface (BF × BF), Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes were sourced from six commercial hill flocks and finished on one of four diets: grass pellets (GP), cereal-based concentrate (CC), CC enriched with oilseed rape (CR) and CC enriched with fish oil (CF). Dry matter intake (DMI) was highest (P < 0.001) in lambs offered GP; however, carcass weight gain (CWG) and feed conversion efficiency were higher (P < 0.001) in lambs fed concentrate-based diets. For lambs offered concentrate-based diets, DMI and live weight gain were lower (P < 0.001) for CF than CC or CR. Lambs with T × BF dams achieved a higher (P < 0.05) daily CWG and CWG/kg DMI than BF × BF, SW × BF or LL × BF dams. When lambs were slaughtered at fat score 3, CH × BF, LL × BF and T × BF dams increased carcass weight by 0.8 to 1.4 kg (P < 0.001) and conformation score (CS) by 0.2 to 0.4 units (P < 0.001) compared with BF × BF or SW × BF dams. However, breed effects on carcass conformation were reduced by 50% when lambs were slaughtered at a constant carcass weight. Diets CC and CR increased carcass weight by 0.8 to 1.6 kg (P < 0.001) and CS by 0.1 to 0.3 units (P < 0.001) compared with GP and CF. Both, dam breed and dietary effects on carcass conformation were associated with an increase (P < 0.001) in shoulder width of the lambs. Lambs fed CF and slaughtered at a constant carcass weight had more subcutaneous fat over the Longissumus dorsi (P < 0.05), Iliocostalis thoracis (P < 0.001) and Obliquus internus abdominis (P < 0.001) compared with those fed CC. However, these effects were removed when lambs were slaughtered at a constant fat score. At both endpoints, lambs from T × BF dams contained less (P < 0.05) perinephric and retroperitoneal fat than SW × BF or LL × BF dams fed GP or CC, respectively. The results from this study show that using crossbred ewes sired by CH, LL or T sires will increase carcass weight and improve carcass conformation of lambs sourced from hill flocks. Inclusion of oilseed rape in lamb finishing diets had only minor effects on performance compared with a standard CC but feeding fish oil or GP impacted negatively on lamb growth and carcass quality.

Effects of supplementation with fish oil and barium selenate on performance, carcass characteristics and muscle fatty acid composition of late season lamb finished on grass-based or concentrate-based diets.

The objectives of this study were to investigate the effects of fish oil supplementation on performance and muscle fatty acid composition of hill lambs finished on grass-based or concentrate-based diets, and to examine the interaction with selenium (Se) status. In September 2006, 180 entire male lambs of mixed breeds were sourced from six hill farms after weaning and finished on five dietary treatments: grazed grass (GG), grass +0.4 kg/day cereal-based concentrate (GC), grass +0.4 kg/day cereal-based concentrate enriched with fish oil (GF), ad libitum cereal-based concentrate (HC) and ad libitum fish oil-enriched concentrate (HF). Within each treatment, half of the lambs were also supplemented with barium selenate by subcutaneous injection. At the start of the trial, the proportion of lambs with a marginal (<0.76 µmol/l) or deficient (<0.38 µmol/l) plasma Se status was 0.84 and 0.39, respectively. Compared with control lambs, GG lambs treated with Se had higher (P < 0.01) plasma Se levels, whereas erythrocyte glutathione peroxidase activity was higher (P < 0.01) for Se-supplemented lambs fed diets GG and GF. However, Se supplementation had no effects on any aspect of animal performance. Fish oil increased (P < 0.05) levels of 22:5n-3 and 22:6n-3 in the Longissimus dorsi of HF lambs but otherwise had no effect on the health attributes of lamb meat. There were no significant effects of fish oil on dry matter intake, animal performance or lamb carcass characteristics. Daily carcass weight gain (CWG; P < 0.001), carcass weight (P < 0.01) and conformation score (P < 0.01) increased with increasing concentrate inputs. Lambs fed concentrate-based diets achieved a higher mean CWG (P < 0.001), dressing proportion (P < 0.001) and carcass weight (P < 0.011), and were slaughtered up to 8.3 days earlier (P < 0.05) and at 1.2 kg lower (P < 0.05) live weight than pasture-fed lambs. However, carcasses from grass-fed lambs contained lower levels of perinephric and retroperitoneal fat (P < 0.05), and had less fat over the Iliocostalis thoracis (P < 0.001) and Obliquus internus abdominis (P < 0.05). Meat from grass-fed lambs also had lower levels of 18:2n-6 and total n-6 fatty acids compared with those finished indoors. The results of this study demonstrate that fish oil supplementation has some benefits for the health attributes of meat from lambs fed concentrate-based diets but not grass-based diets. Supplementing Se-deficient lambs with barium selenate will improve Se status of lambs fed zero-concentrate diets, but has no additional benefit when lambs are already consuming their daily Se requirement from concentrates or when fish oil-enriched diets are fed.

Comparison of the longevity and lifetime performance of Scottish Blackface ewes and their crosses within hill sheep flocks.

A study was undertaken to compare the longevity and lifetime lamb output of purebred Scottish Blackface (BF) ewes with a range of crossbred genotypes from Scottish BF dams. For up to five successive breeding seasons, 1143 Scottish BF, Swaledale × BF (SW × BF), North Country Cheviot × BF (CH × BF), Lleyn × BF (LL × BF) and Texel × BF (T × BF) ewes were mated to a range of sire breeds on six hill farms across Northern Ireland. Dentition and lamb output were recorded annually until completion of the study or until the ewe was removed due to death or culling. Timing of mortality and the main reason for culling were also recorded. When survival analysis was undertaken, SW × BF and CH × BF ewes had better longevity (P < 0.05) than BF ewes due to their lower culling rate (P < 0.01) and lower mortality rate (P = 0.06), respectively. The relative proportion of LL × BF and T × BF culled due to infertility was lower (P < 0.05) than SW × BF and CH × BF, while a higher (P < 0.05) proportion of LL × BF and T × BF ewes were culled for prolapses compared with the other breed crosses. SW × BF ewes had consistently higher bite scores (P < 0.001) compared with BF, LL × BF and T × BF, indicating a greater prevalence and degree of overshoot. In ewes aged 5.5 years old, SW × BF also had a higher incidence of tooth loss (P < 0.01) compared with the other breeds. However, the proportion of SW × BF culled due to poor teeth condition was lower (P < 0.05) than BF. Across all breeds, the chances of surviving to their next mating were influenced by ewe breed (P < 0.05), age at mating (P < 0.001), body condition score at weaning (P < 0.001), number of missing teeth (P < 0.001) and average daily live weight gain per litter (P < 0.05). The cumulative number and weight of lambs weaned per ewe over five successive matings was higher (P < 0.05) for crossbred compared with pure BF ewes; however there were no differences in lifetime output between the different crossbred ewes studied. This study demonstrates that the higher lamb output of crossbred hill ewes does not compromise their longevity compared with pure Blackface, resulting in greater total lifetime production. When the crossbred ewes are sired by a second hill breed, longevity may be improved.

Effects of breed and age on the performance of crossbred hill ewes sourced from Scottish Blackface dams.

The aim of this study was to evaluate the effects of age and breed on the reproductive performance and lamb output of crossbred hill ewes relative to purebred Scottish Blackface (BF). BF ewes were compared alongside Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes on six commercial hill farms across Northern Ireland, on which all the ewes were born and reared. Ewes were mated to a range of sire breeds, balanced across breeds, for up to five successive breeding seasons. Mature live weight of adult BF, SW × BF, CH × BF, LL × BF and T × BF ewes was 52.8, 54.9, 60.3, 55.6 and 58.6 kg (P < 0.001), respectively. Compared with the pure BF, the number of lambs born per ewe lambed was higher with LL × BF and SW × BF (P < 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL × BF and T × BF (P < 0.01). Total litter weight at birth of all the crossbred ewes was heavier (P < 0.01) than the pure BF, except in primiparous 2-year-old ewes. Lambs born to CH × BF and T × BF dams were 0.24 to 0.35 kg heavier at birth (P < 0.01) than the other ewe breeds, whereas lambs born to CH × BF, LL × BF and T × BF dams were, on average, 1.7, 1.3 and 1.5 kg, respectively, heavier (P < 0.01) at weaning than those from BF dams due to their higher (P < 0.05) average daily gain. Compared with the pure BF, total weaned lamb output per ewe lambed was 3.7, 4.8, 6.7 and 5.4 kg heavier (P < 0.05) for SW × BF, CH × BF, LL × BF and T × BF, respectively. However, as a result of the heavier live weight of the crossbred ewes, production efficiency (lamb output per kilogram live weight (W) and lamb output per kilogram metabolic live weight (W0.75)) was higher (P < 0.001) for LL × BF ewes only. For all ewe breeds, litter size at birth per ewe lambed, total lamb birth weight per ewe lambed and litter size at weaning increased (P < 0.001) with age up to 5 years, but decreased in 6-year-old ewes. Average lamb weaning weight and total weaned lamb output per ewe lambed increased (P < 0.001) with age up to 4 years . Production efficiency of the 6-year-old ewes was lower (P < 0.01) than the younger ewes. This study shows that adopting a flock replacement policy based on crossing BF ewes with LL, SW, T and CH sires can lead to significant improvements in the productivity of hill flocks.

Effectiveness of different footbath solutions in the treatment of digital dermatitis in dairy cows.

Three experiments were conducted to test the effectiveness of different footbath solutions and regimens in the treatment of digital dermatitis (DD) in dairy cows. During the study, groups of cows walked through allocated footbath solutions after milking on 4 consecutive occasions. All cows were scored weekly for DD lesion stage on the hind feet during milking. A "transition grade" was assigned on the basis of whether the DD lesions improved (1) or deteriorated or did not improve (0) from week to week. This grade per cow was averaged for all cows in the group. In experiment 1, 118 cows were allocated to 1 of 3 footbath treatments for 5 wk: (1) 5% CuSO(4) each week, (2) 2% ClO(-) each week, or (3) no footbath (control). The mean transition grade, and proportion of cows without DD lesions at the end of the trial were significantly higher for treatment 1 above (0.36, 0.13, and 0.11, respectively; standard error of the difference, SED = 0.057). In experiment 2, 117 cows were allocated to 1 of 4 footbath treatment regimens for 8 wk: (1) 5% CuSO(4) each week, (2) 2% CuSO(4) each week, (3) 5% CuSO(4) each fortnight, or (4) 2% CuSO(4) each fortnight. For welfare reasons, cows allocated to the weekly and fortnightly footbath regimens had an average prevalence of >60% and ≤25% active DD at the start of the trial, respectively. Significantly more cows had no DD lesions (0.53 vs. 0.36, respectively; SED = 0.049), and the mean transition grade of DD lesions was higher in the 5% compared with the 2% weekly CuSO(4) treatment (0.52 vs. 0.38, respectively; SED = 0.066). Similarly, significantly more cows had no DD lesions in the 5% compared with the 2% fortnightly CuSO(4) treatments (0.64 vs. 0.47, respectively; SED = 0.049). In experiment 3, 95 cows were allocated to 1 of 3 footbath treatments: (1) each week alternating 5% CuSO(4) with 10% salt water, (2) each week alternating 5% CuSO(4) with water, or (3) 5% CuSO(4) each fortnight (control). After 10 wk, more cows had no DD in the salt water treatment than in the control treatment (0.35 vs. 0.26, respectively; SED = 0.038), but levels of active lesions were higher for this treatment than in the other 2 treatments (0.17, 0.00, and 0.13, respectively; SED = 0.029). Treatment did not affect mean transition grade of DD lesions. In conclusion, CuSO(4) was the only footbath solution that was consistently effective for treatment of DD. In cases when DD prevalence was high, a footbath each week using 5% CuSO(4) was the most effective treatment.

Mitigation of enteric methane emissions through improving efficiency of energy utilization and productivity in lactating dairy cows.

The data set used in the present study was obtained from 20 energy metabolism studies involving 579 lactating dairy cows (511 Holstein-Friesian, 36 Norwegian Red, and 32 Jersey-Holstein crossbreds) varying in genetic merit, lactation number, stage of lactation, and live weight. These cows were offered diets based on grass silage (n=550) or fresh grass (n=29), and their energy intake and outputs, including methane energy (CH(4)-E), were measured in indirect open-circuit respiration calorimeter chambers. The objective was to use these data to evaluate relationships between CH(4)-E output and a range of factors in animal production and energetic efficiency in lactating dairy cows under normal feeding regimens. The CH(4)-E as a proportion of milk energy output (E(l)), E(l) adjusted to zero energy balance (E(l(0))), or intakes of gross energy (GE), digestible energy (DE), or metabolizable energy (ME) was significantly related to a wide range of variables associated with milk production (E(l) and E(l(0))) and energy parameters (energy intake, metabolizability, partitioning, and utilization efficiencies). Three sets of linear relationships were developed with experimental effects removed. The CH(4)-E/GE intake (r(2)=0.50-0.62) and CH(4)-E/E(l) (r(2)=0.41-0.68) were reduced with increasing feeding level, E(l)/metabolic body weight (MBW; kg(0.75)), E(l(0))/MBW, GE intake/MBW, DE intake/MBW, and ME intake/MBW. Increasing dietary ME/DE decreased CH(4)-E/E(l) (r(2)=0.46) and CH(4)-E/GE intake (r(2)=0.72). Dietary ME concentration and ME/GE were also negatively related to CH(4)-E/GE intake (r(2)=0.47). However, increasing heat production/ME intake increased CH(4)-E as a proportion of E(l) (r(2)=0.41), E(l(0)) (r(2)=0.67) and energy intake (GE, DE, and ME; r(2)=0.62 and 0.70). These proportional CH(4)-E variables were reduced with increasing ratios of E(l)/ME intake and E(l(0))/ME intake and efficiency of ME use for lactation (r(2)=0.49-0.70). Fitting CH(4)-E/E(l) or CH(4)-E/E(l(0)) against these energetic efficiencies in quadratic rather than linear relationships significantly increased r(2) values (0.49-0.67 vs. 0.59-0.87). In conclusion, CH(4)-E as a proportion of energy intake (GE, DE, and ME) and milk production (E(l) and E(l(0))) can be reduced by increasing milk yield and energetic efficiency of milk production or by reducing energy expenditure for maintenance. The selection of dairy cows with high energy utilization efficiencies and milk productivity offers an effective approach to reducing enteric CH(4) emission rates.

Effect of offering dairy cows diets differing in phosphorus concentration over four successive lactations: 1. Food intake, milk production, tissue changes and blood metabolites.

The loss of phosphates from dairy farms contributes to the eutrophication of waterways. Whilst reducing the phosphorus (P) content of dairy cow diets has the potential to help reduce phosphate losses, diets containing inadequate dietary P may have a negative effect on cow health and performance. To address this issue, 100 winter-calving Holstein-Friesian dairy cows were offered diets containing either 'high' or 'low' levels of dietary P. The experiment was conducted over a 4-year period, with 80 primiparous cows commencing the study in year 1, while a further 20 primiparous cows commenced the study in year 2. Rations offered during the winter comprised grass silage, maize silage (70 : 30 dry matter (DM) basis, approximately) and concentrates (10.0 to 12.0 kg/cow per day). During the summer periods in years 1 and 2, half of the cows grazed both day and night, while the remaining cows grazed by day, and were housed by night and offered grass silage. During years 3 and 4, all cows grazed both day and night during the summer period. Concentrate feed levels during the summer periods were 3.0 to 4.0 kg/cow per day. Different dietary P levels were achieved by offering concentrates containing either high or low P levels during the winter period (approximately 7.0 or 4.4 g P/kg DM respectively), and during the summer period (approximately 6.8 or 3.6 g P/kg DM, respectively). Total ration P levels averaged 4.9 and 3.6 g P/kg DM for the 'high' and 'low' P winter diets respectively, and 4.2 and 3.6 g P/kg DM for the 'high' and 'low' P summer diets respectively. A total of 95, 70, 50 and 22 cows completed each of lactations 1 to 4 respectively. Dietary P level had no significant effect on food intake, milk output or milk composition (P > 0.05). Plasma P concentrations were significantly lower with cows offered the 'low' P diet in each of lactations 1 to 4 (P < 0.05). In each of lactations 3 and 4, cows offered the 'low' P diet tended to have lower condition scores and live weights than those offered the 'high' P diet. The results of this experiment highlight that the P content of dairy cow diets can be substantially reduced with no detrimental effect on dairy cow performance.

Effect of offering dairy cows diets differing in phosphorus concentration over four successive lactations: 2. Health, fertility, bone phosphorus reserves and nutrient utilisation.

This experiment examined the long-term effects of offering diets containing low levels of dietary phosphorus (P) on dairy cow health, fertility and bone composition, and the effect of dietary P level on nutrient utilisation. One hundred winter-calving Holstein-Friesian dairy cows were offered diets containing either 'high' or 'low' levels of dietary P over a 4-year period. Rations offered during the winter included grass silage, maize silage (70 : 30 dry matter (DM) basis, approximately) and concentrates (10.0 to 12.0 kg/cow per day). During the summer periods in years 1 and 2, half of the cows grazed both day and night, while the remaining cows grazed by day, and were housed by night and offered grass silage. During years 3 and 4, all cows grazed both day and night during the summer period. Concentrate feed levels during the summer periods were 3.0 to 4.0 kg/cow per day. Different dietary P levels were achieved by offering concentrates containing either high or low P levels during the winter period (approximately 7.0 or 4.4 g P/kg DM, respectively) and during the summer period (approximately 6.8 or 3.6 g P/kg DM, respectively). Total ration P levels averaged 4.9 and 3.6 g P/kg DM for the high and low P winter diets, respectively, and 4.2 and 3.6 g P/kg DM for the high and low P summer diets, respectively. A total of 95, 70, 50 and 22 cows completed each of lactations from 1 to 4, respectively. Neither the incidence of lameness or mastitis, or milk somatic cell count, were affected by dietary P level (P > 0.05), while none of the fertility parameters recorded in any of lactations from 1 to 4 was affected by the dietary P level (P > 0.05). Dietary P level had no effect on the specific gravity, ash or calcium content of rib cortical bone cores (n = 78 cows), while the P content of cortical bone (g/kg fresh, g/kg DM and mg/ml fresh bone) was lower with cows offered low P diets (P < 0.05). Dietary P level had no significant effect on the digestibility of either the DM, nitrogen, energy or acid detergent fibre fraction of the diet (P > 0.05), while faecal P excretions were reduced by a mean of 27 g/cow per day with cows offered the low P diets during the winter period. The results of this study indicate that dietary P levels can be reduced to proportionately 0.8 (approximately) of current UK feeding standards (Agricultural and Food Research Council, 1991), with no detrimental effect on dairy cow health or fertility, while having only minor effects on bone composition.

Effect of dietary protein content on the fertility of dairy cows during early and mid lactation.

Ninety autumn-calving Holstein dairy cows (45 primiparous and 45 multiparous; mean parity, 3.1) were allocated to 1 of 3 treatments; 173, 144, or 114 g of crude protein (CP)/kg of dry matter (DM) from calving until d 150 of lactation. On d 151 of lactation, half the animals receiving 114 g of CP/kg of DM went onto 144 g of CP/kg of DM, half of the animals receiving 144 g of CP/kg of DM went onto 173 g of CP/kg of DM, and half of the animals receiving 173 g of CP/kg of DM went onto 144 g of CP/kg of DM, with the remaining animals staying on their original treatments. This resulted in 6 treatments in mid to late lactation: 114/114; 144/144; 173/173; 114/144; 144/173; and 173/144 g of CP/kg of DM. Overall, 95.3% of cows intended for breeding conceived during a 6-mo breeding period. The average pregnancy rates to first service and first plus second service were 30.9% [standard error of the difference (SED), 0.05] and 56.7% (SED, 0.05) respectively. The average 100 d in-calf rate from the start of the breeding period was 70.5%, and at least one abnormal progesterone profile was observed in 62% of animals. An increase in dietary protein content decreased the requirement for treatment of metritis. There was no effect of dietary protein content on any of the reproductive or progesterone measures; for example, days to conception, calving interval, 100 d in-calf rate (from commencement of breeding), days to onset of luteal activity, average luteal phase, average interovulatory interval, or average interluteal interval. An increase in dietary protein content decreased the average daily energy balance. A more positive energy balance was associated with an increased requirement for the treatment of metritis in the current study. Cumulative energy balance was positively associated with conception. There was no effect of the concentration of plasma urea on any of the reproductive variables; however, the concentration of serum leptin was favorably associated with the time to progesterone increase above 3 ng/mL, which has been deemed essential for embryo survival. Additionally, the average peak concentration of progesterone and the duration of the average luteal phase were favorably associated with the interval from calving to conception. The latter relationships emphasize the importance of progesterone in achieving and maintaining pregnancy.

Effects of breed and production system on lameness parameters in dairy cattle.

The aim of the present study was to assess the effects of Holstein-Friesian (HF) and Norwegian (N) dairy cattle genotypes on lameness parameters in dairy cattle within different production systems over the first 2 lactations. Following calving, HF (n = 39) and N (n = 45) heifers were allocated to 1 of 3 systems of production (high level of concentrate, low level of concentrate, and grass-based). High- and low-concentrate animals were continuously housed indoors on a rotational system so that they spent similar amounts of time on slatted and solid concrete floors. Animals on the grass treatment grazed from spring to autumn in both years of the study, so that most animals on this treatment grazed from around peak to late lactation. Claw health was recorded in both hind claws of each animal at 4 observation periods during each lactation as follows: 1) -8 to 70 d postcalving, 2) 71 to 150 d postcalving, 3) 151 to 225 d postcalving, and 4) 226 to 364 d postcalving. Sole lesions, heel erosion, axial wall deviation, sole length of the right lateral hind claw (claw length), right heel width, and right lateral hind heel height were recorded as well as the presence of digital dermatitis. The N cows had lower (better) white line and total lesion scores than HF cows. Cows on the high- and low-concentrate treatments had better sole and total lesion scores than cows on the grass treatment. The HF cows had better locomotion scores than N cows. Breed and production system differences were observed with respect to claw conformation, including claw length, heel width, and heel height. Digital dermatitis was associated with worse sole lesion scores and interacted with production system to influence white line lesion scores and maximum heel erosion scores. This study shows that genetic, environmental, and infectious factors are associated with hoof pathologies in dairy cows.

Effect of supplementation with barium selenate on the fertility, prolificacy and lambing performance of hill sheep.

Six weeks before mating, the ewes on six hill farms were randomly assigned to receive either a subcutaneous injection of a long-acting supplement containing 50 mg/ml selenium as barium selenate, or no injected selenium. Before the treatment, the mean activity of glutathione peroxidase (GSHPx) in the ewes on the six farms ranged from 166 to 592 U/g haemoglobin (Hb) and their plasma selenium concentrations ranged from 0.60 to 1.61 micromol/l. Treated ewes had higher plasma selenium concentrations and higher GSHPx activities than control ewes during the study. Conception rates were higher in the treated ewes than in the control ewes. At six weeks, the lambs born to the treated ewes had higher plasma selenium and GSHPx levels than the controls. The treated ewes reared 9 per cent more lambs than the control ewes. The treated ewes had lower abortion rates, and higher liveweights and body condition scores than the controls. There were weak but positive associations between the plasma selenium and GSHPx levels of the ewes and their reproductive performance.

Effect of dietary protein content on animal production and blood metabolites of dairy cows during lactation.

Ninety autumn-calving Holstein dairy cows [45 primiparous and 45 multiparous (mean parity, 3.1)] were allocated to 1 of 3 dietary crude protein (CP) concentrations: 173, 144, or 114 g of CP/kg of DM, from calving until d 150 of lactation. On d 151, half of the animals in each treatment were allocated an alternative dietary protein concentration. Half of the animals receiving 114 g of CP/kg of DM went onto 144 g of CP/kg of DM; half of the animals receiving 144 g of CP/kg of DM went onto 173 g of CP/kg of DM; and half of the animals receiving 173 g of CP/kg of DM went onto 144 g of CP/kg of DM, with the remaining animals staying on their original treatment. This resulted in 6 treatments in the mid to late lactation period: 114/114, 144/144, 173/173, 114/144, 144/173, and 173/144 g of CP/kg of DM. An increase in dietary CP concentration significantly increased milk, fat, and protein yield in early lactation (d 1 to 150). Dry matter intake was also increased with increased dietary protein concentration; however, this was not significant between 144 and 173 g of CP/kg of DM. Increased dietary CP significantly increased plasma urea, albumin, and total protein concentrations but had no significant effect on NEFA, leptin, or IGF-1 concentrations. Decreasing the dietary CP concentration in mid-late lactation (d 151 to 305) from 173 to 144 g/kg of DM had no significant effect on milk yield, dry matter intake, or milk fat and protein yield, compared with animals that remained on 173 g of CP/kg of DM throughout lactation. Increasing dietary CP concentration from 144 to 173 g/kg of DM significantly increased dry matter intake compared with animals that remained on the 144 g of CP/kg of DM throughout lactation. There were no significant dietary treatment effects on live weight or body condition score change throughout the experiment. Results of this study indicate that high protein diets (up to 173 g of CP/kg of DM) improved feed intake and animal performance in early lactation (up to d 150), but thereafter, protein concentration can be reduced to 144 g of CP/kg of DM with no detrimental effects on animal performance.

Effect of dietary protein content on estrous behavior of dairy cows during early and mid lactation.

One of the main contributing factors to the decline in fertility in contemporary dairy farming is the inability to detect cows in estrus. In the current study, 90 Holstein dairy cows [45 primiparous and 45 multiparous (mean parity of 3.1)] were allocated to 1 of 3 treatments at calving; 173, 144, or 114 g of crude protein/kg of dry matter. Estrous behavior was recorded for one 30-min period every 12 h from calving until all animals reached 140 d postpartum. Behavioral activities were recorded according to a scoring system developed by Van Eerdenburg et al. (1996), with 9 key estrous behavioral activities each allocated a given number of points. If the total score allocated was greater than or equal to 50 points during a single or consecutive observational periods, then the animal was deemed to be in estrus. A total of 238 estrous cycles scored 50 points or above on the Van Eerdenburg et al. (1996) scale in this experiment, with 51.7% of these cycles being characterized as standing immobile on mounting. There were no direct effects of dietary protein content on estrous behavior; however, 3 significant stage of lactation x protein treatment interactions occurred for the behavioral activities (mucous discharge, chin resting, and mounting the head side of another cow), but no consistent trends were apparent from the predicted means. There was a significant influence of parity on the frequency of mounting the head side of another cow and total number of behavior activities displayed per estrous cycle. In both cases multiparous animals displayed fewer behavioral activities than primiparous animals. An increase in the size of the sexually active group (animals in estrus at the same time, up to 5) significantly increased the expression of mounting or attempting to mount another cow, the number of cycles in which standing immobile on being mounted was observed, the total estrous score and the proportion of cyclic animals that were diagnosed as being in estrus. The most frequent behavioral activity displayed was chin resting (89.5% of cycles), and the most reliable behavior was standing immobile on mounting (when expressed 96.4% of cows were in estrus). The most dependable (function of reliability and frequency displayed) sign of estrus was mounting or attempting to mount another cow. This behavior was expressed in 83% of cycles, and when expressed, 89% of animals were in estrus.

The effects of grain treatment, grain feed level and grass silage feed value on the performance of and meat quality from, finishing beef cattle.

A completely randomised design study involving 132 continental crossbred beef steers was undertaken to evaluate the effects of method of grain treatment and feed level, and grass silage feed value on animal performance, carcass characteristics and meat quality of beef cattle. Winter wheat was harvested and the grain was stored either ensiled crimped and treated with 4.5 l/t of a proprietary acid-based additive (crimped), ensiled whole and treated with 20 kg feed-grade urea per t (urea) or stored conventionally in an open bin treated with 3 l propionic acid per t. Two grass silages, of contrasting feed value (L and H) were ensiled. For the conventional, crimped and urea treatments, grain dry matter (DM) concentrations were 802, 658 and 640 g/kg, respectively. For the L- and H-feed value silages, DM concentrations were 192 and 240 g/kg and D values were 671 and 730 g/kg DM, respectively. The silages were offered as the sole forage supplemented with either conventional, crimped or urea-treated grain-based concentrate at either 3.5 or 6.0 kg DM per steer per day. The grain supplement consisted of 850 and 150 g/kg DM of grain and citrus pulp, respectively. For the conventional, urea and crimped treatments, DM intakes were 8.85, 9.43 and 9.04 kg/day (standard error (s.e.) = 0.129); estimated carcass gains were 0.60, 0.55 and 0.61 kg/day (s.e. = 0.020), respectively. For the low- and high- feed value grass silages, estimated carcass gains were 0.56 and 0.61 kg/day (s.e. = 0.014), respectively. For the low and high grain feed levels, estimated carcass gains were 0.56 and 0.61 kg/day, respectively. Grain treatment, grain feed level or silage feed value did not alter (P > 0.05) meat quality, lean colour or fat colour. There were significant silage feed value × grain feed level interactions (P < 0.05) for final live weight (LW) and daily live-weight gain (DLWG). Increasing grain feed level increased final LW and DLWG when offered with the low-feed value silage, however, grain feed level had no effect on final LW or DLWG when offered with the high-feed value silage. It is concluded that urea treatment of grain increased silage intake and feed conversion ratio (kg DM intake per kg carcass) and tended to decrease carcass gain. Crimping provides a biologically equally effective method to store grain as conventional methods. Improving grass silage feed value had a greater impact on animal performance than increasing grain feed level by 2.4 kg DM per day.

Effects of replacing grass silage with either maize or whole-crop wheat silages on the performance and meat quality of beef cattle offered two levels of concentrates.

A randomised design involving 66 continental cross beef steers (initial live weight 523 kg) was undertaken to evaluate the effects of the inclusion of maize or whole-crop wheat silages in grass silage-based diets on animal performance, carcass composition, and meat quality of beef cattle. Grass silage was offered either as the sole forage or in addition to either maize or whole-crop wheat silages at a ratio of 40:60, on a dry matter (DM) basis, alternative forage: grass silage. For the grass, maize, and whole-crop wheat silages, DM concentrations were 192, 276, and 319 g/kg, ammonia-nitrogen concentrations were 110, 90, and 150 g/kg nitrogen, starch concentrations were not determined, 225, and 209 g/kg DM and in vivo DM digestibilities were 0.69, 0.69, and 0.58; respectively. The forages were offered ad libitum following mixing in a paddle type complete diet mixer wagon once per day, supplemented with either 3 or 5 kg concentrates per steer per day, in two equal feeds, for 92 days. For the grass, grass plus maize and grass plus whole-crop wheat silage-based diets food intakes were 8.38, 9.08, and 9.14 kg DM per day, estimated carcass gains were 514, 602, and 496 g/day and carcass weights were 326, 334, and 325 kg; respectively. Altering the silage component of the diet did not influence carcass composition or meat eating quality. Increasing concentrate feed level tended ( P = 0.09) to increase estimated carcass fat concentration and increased sarcomere length ( P < 0.05), and lean a* ( P < 0.01), b* ( P < 0.05), and chroma ( P < 0.01). There were no significant silage type by concentrate feed level interactions for food intake, steer performance, carcass characteristics or meat eating quality. It is concluded that replacing grass silage with maize silage increased carcass gain, and weight due to higher intakes, and improved utilisation of metabolisable energy. Whilst replacing grass silage with whole-crop wheat silage increased live-weight gain, the reduced dressing proportion resulted in no beneficial effect on carcass gain, probably due to increased food intakes of lower digestible forage increasing gut fill. Meat quality or carcass composition were not altered by the inclusion of maize or whole-crop silages in grass silage based diets.