Although the effect of nutrition on enteric methane (CH4) emissions from confined dairy cattle has been extensively examined, less information is available on factors influencing CH4 emissions from grazing dairy cattle. In the present experiment, 40 Holstein-Friesian dairy cows (12 primiparous and 28 multiparous) were used to examine the effect of concentrate feed level (2.0, 4.0, 6.0, and 8.0 kg/cow per day; fresh basis) on enteric CH4 emissions from cows grazing perennial ryegrass-based swards (10 cows per treatment). Methane emissions were measured on 4 occasions during the grazing period (one 4-d measurement period and three 5-d measurement periods) using the sulfur hexafluoride technique. Milk yield, liveweight, and milk composition for each cow was recorded daily during each CH4 measurement period, whereas daily herbage dry matter intake (DMI) was estimated for each cow from performance data, using the back-calculation approach. Total DMI, milk yield, and energy-corrected milk (ECM) yield increased with increasing concentrate feed level. Within each of the 4 measurement periods, daily CH4 production (g/d) was unaffected by concentrate level, whereas CH4/DMI decreased with increasing concentrate feed level in period 4, and CH4/ECM yield decreased with increasing concentrate feed level in periods 2 and 4. When emissions data were combined across all 4 measurement periods, concentrate feed level (2.0, 4.0, 6.0, and 8.0 kg/d; fresh basis) had no effect on daily CH4 emissions (287, 273, 272, and 277 g/d, respectively), whereas CH4/DMI (20.0, 19.3, 17.7, and 18.1g/kg, respectively) and CH4-E/gross energy intake (0.059, 0.057, 0.053, and 0.054, respectively) decreased with increasing concentrate feed levels. A range of prediction equations for CH4 emissions were developed using liveweight, DMI, ECM yield, and energy intake, with the strongest relationship found between ECM yield and CH4/ECM yield (coefficient of determination = 0.50). These results demonstrate that offering concentrates to grazing dairy cows increased milk production per cow and decreased CH4 emissions per unit of milk produced.

It has been suggested that United Kingdom recommendations for feeding the neonatal calf (,500 g milk replacer (MR)/day; ,200-230 g CP/kg milk powder) are inadequate to sustain optimal growth rates in early life. The current study was undertaken with 153 high genetic merit, male and female Holstein-Friesian calves (PIN 2000 5 £48) born between September and March, with heifers reared and bred to calve at 24 months of age. Calves were allocated to one of four pre-weaning dietary treatments arranged in a 2 MR feeding level (5 v. 10 l/day) 3 2 MR protein content (210 v. 270 g CP/kg dry matter (DM)) factorial design. MR was reconstituted at a rate of 120 g/l of water, throughout, and was offered via computerised automated milk feeders. Calves were introduced to pre-weaning diets at 5 days of age and weaned at day 56. During the first 56 days of life, calves offered 10 l MR/day had significantly higher liveweight gains ( P , 0.001) than calves fed 5 l MR/day. No significant differences in liveweight gain were found between calves fed 210 g CP/kg DM MR and those fed 270 g CP/kg DM MR from birth to day 56. Differences in live weight and body size due to feeding level disappeared by day 90. Neither MR feeding level nor MR CP content affected age at first service or age at successful service, and with no milk production effects, the results indicate no post-weaning benefits of increased nutrition during the milk-feeding period in dairy heifers.

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) 3 BF, North Country Cheviot (CH) 3 BF, Lleyn (LL) 3 BF and Texel (T) 3 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 3 BF, CH 3 BF, LL 3 BF and T 3 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 3 BF and SW 3 BF ( P , 0.05), whereas the number of lambs weaned per ewe lambed was greater for LL 3 BF and T 3 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 3 BF and T 3 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 3 BF, LL 3 BF and T 3 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 3 BF, CH 3 BF, LL 3 BF and T 3 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 (W 0.75 )) was higher ( P , 0.001) for LL 3 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.Keywords: crossbreeding, hill flocks, prolificacy, lamb output ImplicationsThe results of this study showed that adopting a flock replacement policy based on crossbreeding Blackface (BF) ewes with Lleyn, Swaledale, Texel (T) or Cheviot (CH) sires can increase productivity of hill flocks compared with pure BF replacements. This is achieved mainly through the increased litter size of the crossbred ewes. While improvements in lamb performance were noted for CH and T-sired ewes, their heavier body weight limits the potential to increase biological efficiency and lamb output per hectare. Assessment of the longevity and lifetime output of these more prolific breed types under hill conditions is, however, essen...

The study investigated the effects of lamb genotype produced from hill flocks on feed efficiency, carcass characteristics and meat quality in animals finished on either a high forage:concentrate ratio diet (HFC) or a low forage:concentrate ratio diet (LFC). Purebred Scottish Blackface (BXB) lambs were compared with Blue-Faced Leicester×Scottish Blackface (BLXB) and Texel×Scottish Blackface (TXB) lambs. Purebred Cheviot (CXC), Suffolk×Cheviot (SXC) and Texel×Cheviot (TXC) lambs were also investigated. Lambs on the LFC diet were offered grass silage and concentrates mixed in the proportion of 0·80 silage and 0·20 concentrates on a dry matter basis. The LFC diet consisted of 0·20 grass silage and 0·80 concentrates on a dry matter basis. Representative lambs were slaughtered at the start of the experiment and on reaching 38 and 46 kg live weight. Averaged over the two slaughter weights, within the Blackface cross lambs, BXB had a lower liveweight gain (P < 0·01) than either BLXB or TXB (138, 207 and 203 (S.E. 11·1) g/day, respectively). Within the Cheviot cross lambs, CXC had a lower liveweight gain (P < 0·05) than SXC (188 v. 220 (S.E. 11·1) g/day), while SXC and TXC (204 g/day) had similar liveweight gains. Lambs on the LFC diet had a higher dressing proportion (P < 0·001) compared with lambs finished on the HFC diet (0·466 v. 0·434 (S.E. 0·0018) kg carcass per kg live weight). Averaged over the two slaughter weights BXB lambs had a lower (P < 0·05) dressing proportion than the other genotypes. Carcass conformation classification (assessed on a five-point scale) was higher (P < 0·001) in lambs finished on the LFC diet (3·0 v. 2·4 (S.E. 0·04)). Conformation classification was higher in lambs produced from Cheviot compared with Blackface ewes (P < 0·05). Within the Blackface cross lambs, BXB and BLXB lambs had a lower conformation classification (P < 0·001) than TXB lambs (2·4, 2·4 and 2·9 (S.E. 0·08) respectively). Within the Cheviot ewes, TXC lambs had a higher (P < 0·001) classification than either CXC or SXC (3·1, 2·7 and 2·7 (S.E. 0·08) respectively). Lambs finished on the LFC diet had a higher fat classification score compared with lambs on the HFC diet (P < 0·001) (3·4 v. 2·8 (S.E. 0·04)). Fat classification was similar across all genotypes. Lambs finished on the LFC diet had a lower ash content in the carcass than lambs finished on a HFC diet (P < 0·01) (44 v. 47 (S.E. 0·8) g/kg). Lamb genotype and dietary forage:concentrate ratio had no significant effect on cooking loss, sarcomere length, Warner–Bratzler shear force and L* values. Ultimate pH (pHU) was not influenced by dietary forage:concentrate ratio, but was significantly (P < 0·01) higher in BXB lambs compared with BLXB, TXB, CXC and TXC lambs. Lambs offered the LFC diet during the finishing period had significantly higher values for a* (P < 0·05), b* (P < 0·001), C* (P < 0·001) and H0 (P < 0·05) than lambs offered a HFC diet. Of these parameters only b* was significantly affected by lamb genotype, with BXB lambs having a lower value (P < 0·05) than the other genotypes.

The objective of this study was to determine the effect of lamb genotype and plane of nutrition on post-weaning lamb growth, and carcass characteristics in hill sheep systems. The lamb genotypes compared were as follows: purebred Scottish Blackface, Swaledale 3 Scottish Blackface, Cheviot 3 Scottish Blackface, Lleyn 3 Scottish Blackface and Texel 3 Scottish Blackface lambs. During the finishing period, lambs were allocated to a (i) low plane of nutrition (LP), based on a fixed allowance of dried grass pellets representing a grass-based system; (ii) high plane of nutrition (HP-cereal), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate offered ad libitum; (iii) high plane of nutrition (HP-cereal/oil), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate containing oilseed rape offered ad libitum. There were significant genotype 3 diet interactions for dry matter (DM) intake ( P , 0.001), live weight gain ( P , 0.05) and carcass gain ( P , 0.05). On the LP diet, carcass gains were higher for Texel cross compared to Blackface and Swaledale cross lambs ( P , 0.05). On both HP diets, carcass gains were lower in Blackface and Swaledale crosses compared with the Cheviot, Lleyn and Texel cross lambs ( P , 0.01). Feed conversion efficiency, expressed in terms of carcass gain per unit of DM, was highest for Texel cross and Cheviot cross, lowest in Swaledale cross and Blackface and intermediate for Lleyn cross lambs ( P , 0.001). Conformation classification was lowest for Swaledale cross ( P , 0.05) and highest for Texel cross lambs ( P , 0.001), whilst those of Blackface, Cheviot and Lleyn cross lambs were similar. Carcasses from Blackface and Lleyn cross lambs had higher fat classifications than Texel and Cheviot cross lambs ( P , 0.01). Feed conversion efficiency was lowest with the LP diet compared with the HP diets, resulting in a 5-week longer finishing period and lower carcass weights, fat scores, dressing proportions and subcutaneous fat depth measurements. These results indicate that crossbreeding can have a major effect on lamb performance in the hill sheep sector. Feeding a HP increased lamb growth rates, particularly for high growthpotential genotypes, improved feed efficiency, shortened the finishing period but increased carcass fatness. Including oilseed rape in concentrate-based diets did not affect performance.