No abstract

This experiment evaluated different strategies for allocating first-cut grass silages to dry dairy cows that had low body-condition score (BCS) at drying off. A total of 48 moderately yielding Holstein-Friesian cows were used, receiving one of three dietary treatments in the dry period and a single lactation diet based on a flat-rate of concentrates and grass silage ad libitum. Throughout the dry period, one group received a low-digestibility silage (harvested 15 June 1998; LL; metabolisable energy (ME) 5 10.3 MJ/kg dry matter (DM)) and a second group received a high-digestibility silage (harvested 9 May 1998, HH; ME 5 11.7 MJ/kg DM). A third strategy (LH) offered the low-digestibility silage in the early dry period and the high-digestibility silage in the final 3 weeks before calving. The silages had very different crude protein concentrations (144 and 201 g/kg DM) and intakes were widely divergent (10.1 v. 13.5 kg DM/day) across the dry period. No concentrates were fed during the dry period. Silage quality had a very large effect on liveweight change, with treatment means of 0.32 and 1.75 kg/day for LL and HH, respectively. BCS changes followed a similar pattern, though no cows became over-conditioned and blood metabolites were within normal ranges. Increased silage digestibility in the late dry period led to a substantial increase in milk fat concentration and a smaller increase in milk protein concentration, the latter confined to the first full week of lactation. Depression of milk fat appears related to low blood glucose when dry cows in low body condition are fed at a low level. The LH strategy avoided the tendency for lower milk yields and fat concentration that resulted from feeding the low-digestibility silage until calving. This strategy also avoided the higher calf weights that resulted from feeding the high-digestibility silage in the early dry period.

This study used individual weekly results for 160 non-lactating Holstein-Friesian dairy cows in the last 5 weeks of gestation to develop regression equations based on forage NDF content and individual body condition score (BCS) for predicting dry matter (DM) intake. Results were used from treatments in which cows received the same forage and no concentrates throughout the dry period. Ten different conserved forages, either grass silages or mixtures of grass silage and barley straw, were fed in six different experiments and forage NDF ranged from 452 to 689 g/kg DM. On average cows gained 390 g live weight per day, which is less than conceptus growth at this stage -suggesting some mobilisation of maternal tissues to support conceptus growth. BCS remained unchanged at 2.5 over the dry period. DM intake declined from 10.79 kg/day 5 weeks before calving to 9.32 kg/day in the week before calving, with half of this decline occurring in the final week before calving. Intake as a percentage of live weight was moderately predicted ( R 2 5 0.61 for the entire period) from measures of diet composition (NDF) and cow state (BCS). There were highly significant negative effects of forage NDF and increased BCS on DM intake. The effect of BCS on DM intake was greatly reduced in the week before calving, possibly as a result of a change in metabolic priorities from gaining to losing body reserves.

Concerns regarding levels of fat consumption and particularly saturated fatty acids (FA) (Department of Health, 1994), has resulted in closer scrutiny of the FA composition of ruminant products. The FAs deposited in beef tissues are relatively saturated, leading to a low polyunsaturated:saturated FA ratio (P:S) in the meat (approximately 0.1, the ideal being about 0.4), whilst the n-6:n-3 ratio is beneficially low at approximately 2. Feeding strategies for raising the P:S ratio whilst keeping n-6:n-3 ratio low are required. This experiment has investigated the impact of feeding different sources of long chain polyunsaturated FA (PUFA) on animal performance and the FA composition of muscle.

Perennial ryegrass varieties bred to express high water-soluble carbohydrate (WSC) concentrations have been shown to improve liveweight gain in pre-weaned lambs of grazing ewes (Lee et al., 2001) compared to conventional ryegrass. Studies have shown that the largest differential in WSC between ryegrass varieties bred for high WSC concentrations and control ryegrasses occurs 5-6 weeks after the plant is allowed to re-grow following cutting or grazing (Miller et al., 2001). Therefore, the benefits, in terms of lamb performance, of using these grasses with high WSC concentrations may be best achieved when they are rotationally rather than continuously grazed. The aim of this experiment was to compare lambs rotationally or continuously grazing either a ryegrass variety bred for high WSC concentrations or a control ryegrass.

Earlier work showed that red clover silage has considerable potential for milk production (e.g. Thomas et al., 1985), though low digestibility and difficulties ensiling clovers were seen as problems that needed to be addressed. Advances in legume breeding and conservation technology as well as a renewed emphasis on extensive organic production systems within Agenda 2000 meant that it was timely to reconsider the potential of legume silages for milk production.

Summary. Summarising the results of the experiments described in the present paper, it is evident that bunt has a distinct influence on vegetative organs of the plant in addition to the well‐known effect on the grain. Both species which cause bunt, Tilletia tritici and T. laevis, were included in one experiment only, from which it appears that the influence of the latter species, while tending hi the same direction, was distinctly weaker in its effect than T. tritici. This conclusion is in harmony with the results of other workers (4,10, 11). The following conclusions refer to T. tritici, with which speck the work was mainly carried out: Soil germination and establishment. The actual percentage of germination has not been found. to differ appreciably in bunt‐free and bunt‐contaminated samples, but in one experiment a considerable difference was manifest in the final establishment, the bunt‐free samples showing an increase of 25–37 per cent, when compared with those which were contaminated with spores before sowing (Table I). The greatest difference (37 per cent.) was shown by the variety Browick, which gave the lowest establishment figure and had presumably suffered most intensely from the unfavourable climatic conditions. Early growth. The first visible symptoms of a retarding influence on growth are not always manifest at the same stage of development in the wheat plant. Under one set of conditions (p. 92) the effect was clearly shown by plants in the seedling stage, since those derived from bunt‐contaminated seed differed from the control by 14–17 per cent. in height, and 16–20 per cent. in the dry weight of 100 shoots. In another experiment (p. 97) where a considerable reduction in height was evident at maturity the plants showed no appreciable effect during the first ten weeks of growth. Tillering. In the matter of tillering the influence of the fungus was in the opposite direction to that recorded for growth in height, bunted plants at the period of maximum tiller development producing in one experiment 16 per cent. more tillers than healthy plants grown under precisely the same conditions. At maturity in both cases the number of heads was considerably less than the total number of tillers produced, but bunted plants still showed an increase over those that were healthy (Experiments III and IV).A similar difference was noted in the case of plants grown in rows in the field1. Length of straw at maturity. A reduction in the length of straw appears to be one of the most constant results of the influence of the fungus on vegetative growth. It will no doubt be shown that the degree of reduction varies with the variety, the season and possibly with the origin of the spores used for contamination. In the experiments here described a reduction in height amounting to 16–19 per cent. in the case of Hen Gymro and 13 per cent, in the case of April Bearded was recorded. It was shown moreover that the reduction was considerably greater in the case of tillers carrying heads in which every grain was bunted than in th...

Body fat and protein reserves at calving can affect milk production and composition (Garnsworthy, 1988; Moorbyet al., 1996). Milk producers frequently feed their dry cows with a low quality diet to prevent them from becoming too fat before calving. However, the cow must nourish the foetus and develop mammary secretory tissues, which can be a problem if she is offered a low protein diet. This experiment was designed to test the interaction between energy and protein supplies during the dry period on changes in live weight (LW), condition score (CS) and muscleLongissimus dorsidepth (LD). Subsequent milk production and composition data are reported in a separate summary (Jaurenaet al., 2001).