Effects of forage NDF content and body condition score on forage intake by Holstein-Friesian dairy cows in the 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 (R2 = 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.

Effects of silage digestibility on intake and body reserves of dry cows and performance in the first part of the next lactation.

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) = 10.3 MJ/kg dry matter (DM)) and a second group received a high-digestibility silage (harvested 9 May 1998, HH; ME = 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.

Comparison of red clover and ryegrass silage for dry cows and influence on subsequent lactation performance.

The objective of this study was to investigate the use of red clover (RC) silage as a forage for dry dairy cows, primarily relative to its impact on tissue mobilization and repletion during the transition period and performance during the first 10 wk of lactation. Forty multiparous lactating Holstein-Friesian dairy cows were divided into 2 paired groups at 70 d before predicted calving dates; a subset (n = 8) of the cows were used for N and P balance measurements twice during the study. From the start of the experiment until 4 wk before predicted calving date all cows were offered ad libitum access to a ryegrass (RG) silage with no concentrate. At 4 wk before predicted calving date, one group of cows remained on the same diet, and the other group was changed to a diet of ad libitum access to RC silage. There was no difference in feed intakes, but CP intake was higher in cows fed RC silage, whereas ME intake was higher in cows fed RG silage. Cows fed RG silage gained more weight over the last 4 wk of the dry period (DP) than those fed RC silage, but there was no treatment effect on BCS. During the DP fecal N excretion was higher for cows fed RC silage, and there were no treatment differences in urine N excretion or overall N balance. At birth, calves from cows fed the RC silage were heavier. After calving, all cows were offered the same diet of ad libitum access to the same RG silage and a standard lactation concentrate. During the first 10 wk of lactation there was no difference in feed intake between the 2 previous treatment groups, and feed intake reached a maximum at approximately 4 wk of lactation. Cows on the RG treatment during the DP gained more longissimus dorsi muscle depth during the DP and retained it during early lactation. Mobilization of this muscle occurred before calving, indicating repartitioning of amino acids to other body tissues. There were no carryover effects of DP treatment on apparent partitioning of N from diet to milk, urine, or feces at wk 3 of lactation. Feeding RC silage during the DP had almost no impact on subsequent performance of dairy cows in early lactation, probably because the 2 silages were nutritionally very similar.

Reducing concentrate supplementation in dairy cow diets while maintaining milk production with pea-wheat intercrops.

In the first of 2 experiments, 40 dairy cows were used to evaluate the milk production potential and concentrate-sparing effect of feeding dairy cows a basal diet of pea-wheat intercrop silages instead of perennial rye-grass silage (GS). Dairy cows were offered GS or 2 intercrop silages prepared from wheat and either Magnus peas (MW, a tall-straw variety) or Setchey peas (SW, a short-straw variety) ad libitum. The respective intercrops were supplemented with 4 kg/d of a dairy concentrate (CP = 240 g/kg dry matter; MW4 and SW4), and the GS were supplemented with 4 (GS4) or 8 (GS8) kg/d of the same concentrate. The second experiment measured the forage DM intake, digestibility, rumen function, and microbial protein synthesis from the forages by offering them alone to 3, nonlactating cows (3 x 3 Latin square design with 21-d periods). Forage dry matter intake was greater in cows fed the intercrop silages than those fed GS. Milk production was greater in cows fed SW4 than those fed GS4 or MW4, but similar to cows fed GS8. Dietary treatment did not affect milk fat, protein, or lactose concentrations. The intercrops had greater N retention, and were more digestible than the GS, and these factors probably contributed to the greater forage DM intakes and greater milk production from the intercrop silages compared with the GS. Rumen volatile fatty acid concentrations were similar across forages, but urinary purine derivative excretion was greater in the cows fed the intercrop silages than the GS, suggesting that rumen microbial protein synthesis was enhanced by feeding the intercrops. In conclusion, similar milk yield and milk composition can be obtained by feeding SW and 4 kg of concentrates as that obtained with GS and 8 kg of concentrates. Feeding intercrop silages instead of GS with the same amount of concentrates increased forage intakes, N retention, and microbial protein synthesis.

Comparison of grass and legume silages for milk production. 1. Production responses with different levels of concentrate.

Silages prepared from pure stands of ryegrass, alfalfa, white clover, and red clover over two successive year were offered to lactating dairy cows in two feeding experiments. Proportional mixtures of all cuts prepared in a yr were used to ensure that the forage treatments were representative of the crop. Additional treatments involved mixtures of grass silage with either white clover silage or red clover silage (50/50, on a DM basis). Silages were prepared in round bales, using a biological inoculant additive, and wilting for up to 48 h. Although the legumes were less suited to silage-making than grass, because of their higher buffering capacity and lower water-soluble carbohydrate content, all silages were well-fermented. A standard concentrate was offered at a flat-rate (8 kg/d in yr 1, and 4 or 8 kg/d in yr 2). All of the legume silages led to higher DM intake and milk yields than for the grass silage, with little effect on milk composition. Intake and production responses to legumes were similar at the two levels of concentrate feeding and with forage mixtures they were intermediate to those for the separate forages. An additional benefit of the clover silages, particularly red clover silage, was the increase in levels of polyunsaturated fatty acids, particularly alpha-linolenic acid, in milk. Legume silages also led to a lower palmitic acid percentage in milk. The efficiency of conversion of feed N into milk N declined with increasing levels of legume silage. White clover silage led to a higher N-use efficiency when the effect of N intake level is taken into account.

Muscle afferent and central command contributions to the cardiovascular response to isometric exercise of postural muscle in patients with mild chronic heart failure.

The roles of muscle afferent activity and central drive in controlling the compromised cardiovascular system of patients with mild chronic heart failure (CHF) during isometric exercise were examined. Blood pressure and heart rate responses were recorded in eight stable CHF patients (ejection fraction 20-40%; age 62+/-11 years) and in nine healthy age-matched controls during voluntary and electrically evoked isometric plantar flexion and subsequent post-exercise circulatory occlusion (PECO). During voluntary contraction, control subjects had a greater mean increase in systolic blood pressure than patients (42.4+/-19.2 and 23.0+/-10.9 mmHg respectively; P<0.01), but this was not the case during PECO. During electrically evoked contraction, but not during PECO, the CHF group had smaller (P<0.05) mean increases in both systolic and diastolic blood pressure than controls (13.0+/-5.3 compared with 25.4+/-14.0 mmHg and 7.6+/-3.0 compared with 12.9+/-7.2 mmHg respectively). Intra-group comparison between responses to voluntary and electrically evoked contractions revealed greater (P<0.05) mean increases in systolic and diastolic blood pressure during the voluntary contraction in both the patients and the control subjects. These data suggest that muscle afferent drive to the pressor response from the triceps surae is low in this age group, both in control subjects and in CHF patients. Additionally, the patients may have a relatively desensitized muscle mechanoreceptor reflex.

Is there a relationship between muscle fatigue resistance and cardiovascular responses to isometric exercise in mild chronic heart failure?

BACKGROUND: Exercise intolerance in chronic heart failure (CHF) may be due to altered fatigue resistance and muscle afferent input to the cardiovascular system from dysfunctional skeletal muscle. AIM: To determine whether calf muscle fatigue resistance was associated with the magnitude of a muscle afferent driven cardiovascular response to isometric exercise. METHODS AND RESULTS: Cardiovascular responses were recorded in eight stable CHF patients (ejection fraction 20-40%) and nine healthy, age-matched controls during voluntary and electrically evoked isometric plantar flexion and post-exercise circulatory occlusion. The force developed by the plantar flexors during a 2-min submaximal electrically evoked fatigue test was measured. There was no relationship between ischaemic muscle fatigue and cardiovascular changes during and after voluntary contraction in either group nor evoked contraction in the CHF group. In the control group, the change in diastolic blood pressure (DBP) at the end of evoked contraction was related to the severity of fatigue at 90 s and 120 s (FI=0.01DeltaDBP+0.3, r=0.81, P<0.05 and FI=0.02DeltaDBP+0.8, r=0.84, P<0.01, respectively). CONCLUSION: Muscle fatigue resistance did not relate to the magnitude of the cardiovascular stress generated by isometric exercise of the same muscle in these patients.

Rumen acid production from dairy feeds. 1. Effects on feed intake and milk production of dairy cows offered grass or corn silages.

Earlier studies developed a new approach to feed evaluation, measuring the net acid load that develops during rumen fermentation. Two concentrates were formulated to be isoenergetic and isonitrogenous, with extremes of rumen acid load. A third treatment comprised a 50:50 mixture of these concentrates. These concentrates were evaluated along with ryegrass silage and corn silage. The feeds were evaluated in a continuous culture system adapted to deliver and record the quantities of acid or alkali needed to maintain a constant pH (6.2 to 6.3). This study confirmed the anticipated ranking of concentrates for rumen acid load, as well as the highly acidogenic nature of corn silage. The concentrates were formulated to balance corn silage and were offered to early-lactation Holstein-Friesian cows at 50% of dry matter intake, with either ryegrass silage or corn silage. Feed intake was lower for animals offered corn silage-based diets (17.4 vs. 22.2 kg of dry matter/d). Increasing concentrate acid load led to a large decline in dry matter intake for corn silage, although not for grass silage. Feed intake effects were reflected in significant effects on yield of milk (31.0, 29.9, and 26.9 kg/d for low-, medium-, and high-acid load concentrates, respectively) and milk solids. Milk protein concentration was unaffected by concentrate type with corn silage diets but tended to be higher when high acid load concentrates were fed with grass silage. This may reflect the effect of the high starch concentrate rectifying a shortage of glucogenic precursors or microbial protein with the grass silage-based diet.

Effects of altering energy and protein supply to dairy cows during the dry period. 1. Intake, body condition, and milk production.

We used 48 Holstein-Friesian cows to investigate the effects of altering energy and protein supply to dry cows. Cows were fed one of three diets for 6 wk prior to parturition: (a) a 60:40 (DM basis) mixture of grass silage with barley straw ad libitum; (b) grass silage ad libitum; or (c) 0.5 kg/d of prairie meal with grass silage ad libitum. The standard lactation diet was a flat-rate allocation of concentrates and grass silage ad libitum. We evaluated dry-period diets using four dry fistulated cows; rumen pH remained high (mean = 6.6) and ammonia concentrations followed N intake. The inclusion of straw reduced apparent ruminal digestion of OM, N, and NDF as well as microbial protein yield, though microbial yield per unit of OM apparently digested in the rumen remained unchanged. Voluntary intake of forage was reduced by the inclusion of straw, while the inclusion of prairie meal had little effect. The decline in intake as calving approached was lower with the silage and straw mix diet. There were large differences in the BW change over the final 5 wk of the dry period, although the opposite effect was seen in early lactation, and differences in BW and body condition score were small by lactation wk 22. Despite the substantial differences in nutrient supply and effects on body reserves, there was little effect of dry-period diet on subsequent performance. Lower forage intakes and yields of protein and lactose were confined to the first month of lactation for cows previously offered straw.

Training-induced adaptations in the central command and peripheral reflex components of the pressor response to isometric exercise of the human triceps surae.

1. The effect of calf raise training of the dominant limb on the pressor response to isometric exercise of the triceps surae was examined in the trained dominant limb and the contralateral untrained limb. Blood pressure and heart rate responses to electrically evoked and voluntary exercise at 30 % maximum voluntary contraction (MVC), followed by post-exercise circulatory occlusion (PECO), were compared before and after a 6 week training period. 2. In the trained limb the diastolic blood pressure rise seen during electrically evoked exercise was reduced by 27 % after training. However, the response during PECO was not significantly affected. 3. During voluntary exercise of the trained limb, diastolic blood pressure rise was reduced by 28 %, and heart rate rise was significantly attenuated after training. During PECO no significant effects of training were observed. 4. Voluntary exercise of the untrained limb resulted in a 24 % reduction in diastolic blood pressure rise after the training period, and a significant attenuation of the heart rate increase during exercise. Responses to electrically evoked exercise and PECO of the untrained limb remained unaltered after training. 5. Attenuation of blood pressure and heart rate responses, in the contralateral untrained limb, during voluntary but not electrically evoked exercise, indicates a training-induced alteration in central command.

Axillary brachial plexus block for perioperative analgesia in 250 children.

A cannula technique for axillary brachial plexus block in combination with general anaesthesia has been in use since 1994 for children undergoing surgical correction of congenital hand anomalies. During a 4-year period data were collected on 250 procedures in 185 patients of median age 3 years detailing the block technique and the intraoperative and postoperative analgesic requirements. Fifteen patients (6%) required supplemental intravenous opioid intraoperatively and this is taken as a marker of failure of the block. Ninety-five patients (38%) required postoperative codeine phosphate with a mean time to receiving codeine phosphate of 9 h. Postoperative pain was controlled in this series with oral analgesia in all but six patients who received parenteral codeine. It is proposed that a cannula technique is an effective and safe method of producing axillary brachial plexus block in children.