Sixteen cross-bred male lambs were assigned to either a group- or a single-rearing treatment up to 150 days of age. After this time the single-housed rams were penned together and all rams were tested weekly for their abilities to successfully mate with ewes for a further 10 weeks. There were no marked differences in the development of sexual behaviour between the two treatments.

1. Four experiments have been carried out to determine the effect of treatment of spring-sown barley straw (var. Deba Abed) with sodium hydroxide (NaOH) solution and subsequent neutralization with hydrochloric acid (HCl) on its digestibility and intake by sheep.

2. In Experiment 1, chopped straw was mixed with 4·5 or 9·0 g NaOH in 200 or 800 ml water/100 g, straw, and after 24 hr neutralized with HCl and left for a further 24 hr before being offered to castrated male sheep (wethers) in a maintenance diet containing 35% concentrates. Organic-matter digestibility of straw significantly increased, by 8 and 11 percentage units respectively, after treatment with 200 ml solution containing 4·5 and 9·0 g NaOH. Volume of solution did not affect digestibility.

3. In Experiment 2, straw treated as in Experiment 1 was given ad libitum. The highest intake was for straw treated with 200 ml solution containing 4·5 g NaOH/100 g straw, treatment with 9·0 g NaOH giving a significantly lower intake but higher than that of untreated straw.

4. In Experiment 3, the in vitro digestibility of milled straw, treated as in Experiments 1 and 4, increased with increasing volumes of solution up to 120 ml/100 g straw, but the response to successive increments of NaOH declined progressively.

5. In Experiment 4 chopped straw was mixed with 4·5, 6·75 or 9·0 g NaOH in 30, 60 or 120 ml water/100 g straw and offered as in Experiment 1. Treatments significantly increased straw digestibility, by 8 to 16 percentage units. Increasing the volume of water from 30 to 60 ml significantly improved digestibility, by 5 percentage units at the two lower levels of NaOH. The response to an increase in the level of NaOH was less, and inconsistent. In vitro and in vivo digestibilities were significantly correlated, but it is concluded that the in vitro technique used overestimates the digestibility of treated straw.

The effect of three moisture concentrations (10, 50 and 75%) and of four fermentation conditions (none, 24 hr aerobic, and 24 and 48 hr anaerobic) on the nutritive value of two complete fattening diets containing 25 and 45% poor roughage, was examined in three digestion and nitrogen balance trials, each of Latin square design, in cattle.

Fermentation increased the lactic acid and volatile fatty acid concentrations of the feed, decreased its pH and the crude fibre content, and caused losses of dry matter.

There were non-significant differences in voluntary intake between the dry and soaked diets. The apparent digestibility of dry and organic matter, crude protein, nitrogen-free extract and crude fibre was non-significantly improved by added moisture. There were no consistent differences in nitrogen retention.

The average metabolizable energy values (ME) observed for both diets were 6% higher than those calculated. There were no significant differences in the apparent digestibility of gross energy or in ME value between treatments of different moisture content.

The fluctuations in pH of rumen liquor during the day differed markedly when the animals received different levels of roughage. These differences were greater when the feed was allowed to ferment. Soaking of feed resulted in a significant increase in the concentration of propionic acid in the rumen liquor, and a non-significant decrease in that of acetic acid. Consequently the C2/C3 ratio was significantly lower on the moist feed treatments.

There were no consistent differences in concentration of ammonia in the rumen liquor, or of urea in the blood.

In a trial involving 231 pigs grown from 20 to 90 kg live weight, three methods of adjusting the feed allowance were compared, namely according to live weight and a scale with weekly adjustments, or according to age with fixed increments of feed, adjusted either weekly or every 3 weeks. Irrespective of the frequency of feed adjustment, rationing by age gave as satisfactory results in performance and carcass quality as rationing by live weight, and reduced labour requirements by eliminating the need for regular weighing of the pigs throughout the growing period.

Two levels of feeding were offered at each of two air temperatures, 25° or 33°C, to pigs while they grew from 20 to 70 kg live weight; two pigs were subjected to each of the four treatments. Significant increases occurred in the urinary excretion of Ca and K by the two pigs fed on the higher level and exposed to 33°C. However these effects could not be related in an obvious way to the lameness which developed in the latter pigs.

One hundred and twenty-four young rabbits of the Giant of Spain breed (mature weight, 4 to 4·5 kg) were slaughtered in groups at birth, 10, 20, 30, 40, 50 and 60 days of age.

Energy retention over the six 10-day periods was 10·7, 26·5, 39·0, 48·9, 72·6 and 57·3 kcal/day, energy content per unit of weight increase was 5·18, 5·52, 5·52, 5·47, 5·80 and 5·89 kcal/g, and deposition of protein (N×6×25) was 1×45, 3×09, 4×28, 5×56, 7×31 and 5×44 g/day. The regression of the energy content of the empty body (kcal) on empty-body weight (g) was:

Y = 1×734 X – 88·536

with a coefficient of regression of 0·97.

ANIMAL PRODUCTION, Volume 20, part 3, p. 426