Two experiments were conducted to investigate the basis for higher voluntary intakes and increased alpha-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of isobutyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of alpha-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of alpha-linolenic acid passing through the rumen. This explains the increased recovery of alpha-linolenic acid from feed into milk with diets based on red clover silage.

A new skin condition of broilers which results in the downgrading of up to 15-30% of broiler carcases/week is described. Unsightly brown-black coloured erosions and ulcers occur on the breast, hock and foot skin. Histopathological examination of these revealed acute inflammation with necrosis of the epidermis and in more severe cases, the upper dermis. A study of the condition has shown a strong association between the appearance of lesions and poor litter conditions and that birds as young as 9 days may be affected. It is suggested that the condition is a contact dermatitis. A study of the development of lesions in one flock is also described.

Moorby, J. M., Evans, R. T., Scollan, N. D., MacRae, J. C., Theodorou, M. K. (2006).. Increased concentration of water-soluble carbohydrate in perennial ryegrass (Lolium perenne L.). Evaluation in dairy cows in early lactation. Grass and Forage Science, 61 (1), 52-59. Sponsorship: LINK Sustainable Livestock Production; Department for Environment, Food and Rural Affairs; Milk Development Council; Meat and Livestock Commission; Germinal Holdings LtdTwelve multiparous Holstein?Friesian dairy cows in early lactation were used to investigate the potential of using perennial ryegrass (Lolium perenne) with a high concentration of water-soluble carbohydrates (WSC) to increase the efficiency of milk production. Ad libitum access to one of two varieties of zero-grazed herbage was given continuously for 3 weeks: treatment High Sugar (HS), an experimental perennial ryegrass variety (Ba11353) bred to contain a high concentration of WSC, harvested in the afternoon; or Control, a standard variety of perennial ryegrass (cv. AberElan), harvested in the morning. All dairy cows also received 4 kg d?1 of a standard dairy concentrate. Dairy cows given the HS diet treatment consumed 2?8 kg dry matter (DM) d?1 more than Control dairy cows (P <0?01), and the DM digestibility of the diet on the HS treatment was significantly greater than that of the diet on the Control treatment (0?75 vs. 0?72; s.e.d. 0?010; P <0?05). Excretion of urinary purine derivatives (PD) tended (P <0?1) to be higher from dairy cows on the HS treatment, implying increased microbial protein flow to the duodenum, although there was no significant difference in the apparent efficiency of rumen fermentation of either dietary nitrogen (N) or DM expressed as a ratio to urinary PD. Milk yields and milk composition were not significantly affected by dietary treatment, although true protein yields of milk were higher (P <0?05) from dairy cows given the HS treatment. The proportion of dietary N excreted in urine was significantly lower from HS cows, although the values were low for both treatments (0?20 g g?1 vs. 0?27 g g?1; s.e.d. 0?020; P <0?05). It is concluded that increased DM intakes by dairy cows given the HS treatment led to increased milk protein outputs. With a proportional decrease in urinary N excretion, the use of perennial ryegrass with a high WSC concentration, in the context of the harvesting regime used in this study, may help to reduce N pollution from dairy systems into which it is incorporated.Peer reviewe

Four mature Holstein-Friesian dairy cows were used in a 4 x 4 Latin square change-over design experiment made up of four 4-wk periods to investigate the relationship between microbial protein flow to the duodenum and excretion of purine derivatives (PD) in the urine. Four dietary treatments based on ad libitum access to ryegrass silage were offered, with a standard dairy concentrate included at different forage:concentrate (F:C) ratios, calculated on a dry matter basis: 80:20, 65:35, 50:50, and 35:65. Feed intakes increased as the proportion of concentrate in the diet increased, despite a concurrent decrease in silage intake. Increased feed intake led to increased nutrient flow to the duodenum. Milk yields increased as the diet F:C ratio decreased, with cows offered the 35:65 diet yielding nearly 8 kg/d more milk than cows offered the 80:20 diet; the concentrations of milk fat decreased and milk protein increased with a decreasing F:C ratio. Purine derivative excretion in the urine increased with an increasing proportion of concentrate in the diet, and there was a strong linear relationship between total PD excretion (allantoin and uric acid) and microbial N flow to the duodenum: microbial N (g/d) = 19.9 + 0.689 x total PD (mmol/d); R = 0.887. This strengthens the case for using PD excretion as a noninvasive marker of microbial protein flow from the rumen in dairy cows.

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