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The effects on the performance of dairy cows offered kale, swedes, and perennial ryegrass in situ and perennial ryegrass silage fed indoors to dairy cows pre-partum during winter in Ireland was examined. Eighty-eight spring-calving dairy cows were randomly assigned to one of four offered treatments; (i) 8 kg of dry matter (DM) of kale leaf and stem + 4 kg DM of perennial ryegrass silage (treatment K), (ii) 8 kg DM of the root and leaf of swedes + 4 kg DM of perennial ryegrass silage (treatment S), (iii) 12 kg DM of perennial ryegrass herbage (treatment G) offered in situ and (iv) perennial ryegrass silage offered ad libitum indoors (treatment ID). Cows on treatments K, S and ID had a greater ( P < 0·001) increase in body condition score (0·20, 0·14 and 0·50 units respectively) pre-partum than cows on treatment G which lost 0·22 units. Pre-partum treatment had no effect on variables of milk production in the following lactation. In the first 100 d of lactation, cows on treatment G pre-partum had a lower milk fat concentration (35·6 g kg−1) compared with cows on treatments S and ID (38·3 and 39·3 g kg−1 respectively). There was no effect of treatment on the intervals between parturition and first insemination (mean 74·6 d) and conception (mean 96·1 d). The results suggest that offering kale and swedes to dairy cows pre-partum resulted in a similar lactation performance to dairy cows grazing a perennial ryegrass sward or offered perennial ryegrass silage indoors. [ABSTRACT FROM AUTHOR]

Despite low net grass growth rates in Ireland between mid-November and February, tissue continuously turns over as new leaves are produced and older leaves senesce. The effects of closing swards from grazing on three dates in autumn (1 September, 20 September and 10 October) on tissue turnover in a perennial ryegrass sward during the winter were examined at two sites in the north-east and south of Ireland. Leaf extension and senescence rates were greater in the south than in the north-east, and were greatest on the earliest closing date at both sites. Leaf appearance and extension rates at both sites were closely correlated with accumulated daily air temperature above 6°C and mean soil temperature. Site-specific factors also influenced tissue flux, possibly including grazing intensity at closing and density of tillers of perennial ryegrass. Swards in the autumn with high herbage masses [>2000 kg dry matter (DM) ha−1 approximately] and high leaf area index (LAI; about 2·5 and above) had the greatest leaf senescence rates and the greatest declines in herbage mass during the winter. Leaf senescence rates per tiller in high LAI swards were correlated positively with amount of leaf per tiller and also the proportion of green leaf in the second youngest expanding leaf lost to senescence. As potentially a complex of interactive factors influences tissue flux in winter, it is proposed that the data from this study be used in conjunction with other data to construct a dynamic model to predict more reliably optimum closing date in autumn for herbage utilization in winter. [ABSTRACT FROM AUTHOR]

Perennial ryegrass ( Lolium perenne L.) is by far the most widely sown grass species in Ireland. Genotype × environment (G × E) interactions are a frequent occurrence in herbage yield evaluations. The objectives were to determine (i) the nature and relative magnitudes of the pertinent G × E interaction variance components for dry matter yield of perennial ryegrass sward plots in Ireland and (ii) the optimal allocation of replicates, locations and years in a testing programme. Sixteen perennial ryegrass cultivars were sown at six locations throughout Ireland between 2000 and 2004. Plots from each sowing were harvested for 2 consecutive years under a simulated mixed grazing and conservation management programme. The largest component of the G × E variance was generally genotype × location × year emphasizing the need for evaluation of genotypes across locations and years to adequately characterize genotypes for differences in yield. Relative differences among genotypes from year to year and location to location were due mainly to changes in genotype rankings. Weather was estimated to have a greater effect on annual variation in herbage yield than age of stand. The optimum allocation of resources for a testing programme was estimated at four replicates per location, and either two locations and 3 sowing years or three locations and 2 sowing years with 2 harvest years for each sowing year. The most appropriate option depends on the relative importance of time vs. financial resources. [ABSTRACT FROM AUTHOR]

Forage dry matter yield (DMY) is a high-priority trait in breeding perennial ryegrass (Lolium perenne L.). However, determining dry matter concentration is highly labor intensive. For a similar level of resources, indirect selection based on fresh matter yield (FMY) would allow a greater number of replicates, genotypes, or both to be evaluated. Our objective was to estimate the efficiency of indirect selection for DMY based on FMY of pure perennial ryegrass sward plots. Over a 14-yr period, replicated trials, containing perennial ryegrass genotypes of similar ploidy and maturity category, were sown in Ire- land and assessed for DMY and FMY at each harvest over two consecutive years. Forage was generally surface dry when harvested. The estimated efficiency of indirect selection based on two replicates and comparable selection intensity was high (≥0.80). Simulation models indicated that resources would be used more efficiently by evaluating more genotypes than by increasing the number of replicates. For example, doubling the number of plots to increase the number of replicates from two to four indicated an increase in the efficiency of indirect selection from a mean 0.88 to 0.94. However, doubling the number of plots and including more genotypes, facilitating greater selection intensity, indicated an increase in the efficiency of indirect selection from a mean 0.88 to 1.04. This study indicates that FMY can be used successfully as an indirect selection method of increasing DMY in perennial ryegrass swards. [ABSTRACT FROM AUTHOR]