W. Holmes

The effect of level of feeding on the digestibility of diets for sheep and cattle

1. In the first experiment, the digestibility of diets containing ratios of 1:1 and 1:4 hay to concentrates was determined at five levels of feeding in castrated male sheep. With diet 1.1, increasing the daily dry matter intake from 600 to 1400 g resulted in a linear decline in organic matter digestibility from 74·4 to 68·6%. The same increase in level of feeding led to a curvilinear decline in the organic matter digestibility of diet 1.4 from 83·0 to 75·9%. 2. In a similar way the crude fibre digestibility of the diets declined as food intake increased. Also the increase in level of feeding caused a decrease in the mean retention time of stained hay in the alimentary tract. 3. In a second experiment the digestibility of long dried grass offered ad libitum to eight dry and eight lactating cows was measured and compared with the digestibility of similar dried grass offered at maintenance level and ad libitum to eight castrated male sheep. 4. On a metabolic live-weight basis (kg W 0·73 ), the lactating cows ate 34% more organic matter than the dry cows and the mean voluntary intake of sheep was only 54% of the intake of dry cows. 5. The organic matter digestibility for the dry cows was 1·9 units higher than that of the lactating cows and at ad libitum intake the organic matter digestibility for the sheep was 5·6 and 3·7 units lower than that of the dry and lactating cows respectively. The results are discussed in relation to the validity of extrapolating results obtained with sheep to cattle, and with non·lactating to lactating animals.

Factors affecting voluntary feed intake in pigs. I. The effect of digestible energy content of the diet on the intake of castrated male pigs housed in holding pens and in metabolism crates

1. The voluntary feed intakes of pigs fed on diets having calculated digestible energy contents of 2,970, 3,356, 3,630 and 3,910 kcal/kg. dry matter were measured over four periods from 38 to 105 kg. live-weight. 2. The pigs achieved similar daily digestible energy intakes regardless of the digestible energy content of the diet. 3. When housed in metabolism crates pigs ate less than when housed in holding pens and the difference was greater than would be expected solely from the reduced exercise of the pigs in crates. 4. Daily digestible energy intake was 575 kcal/kg. live-weight 0.675 when the pigs were in holding pens. The daily digestible energy intake of pigs in metabolism crates increased less with live-weight. 5. The use of metabolism crates to obtain digestibility coefficients and values for nitrogen retention to be applied to animals housed under other conditions is discussed in relation to the differences found in apparent digestibility coefficients, feed intake and growth rates between pigs in crates and in holding pens.

The feed intake of grazing cattle. II. The influence of size of animal on feed intake

1. Two experiments each with 3 dry cows, 3 heifers and 3 calves were carried out in 1959 and 1960 under uniform continuous grazing conditions on a ryegrass-white clover sward to measure individual feed intake by the chromic oxide-faecal nitrogen method. 2. Estimates of digestibility were high (70–82% in organic matter) and there was evidence that calves selected a diet of higher digestibility than cows. 3. Mean daily estimates of organic matter intake were for cows (1300 lb. live-weight) 23·5 lb., for heifers (790 lb. live-weight) 20·8 lb. and for calves (450 lb. live-weight) 14·3 lb. Corresponding digestible organic matter intakes were 17·4, 15·3 and 11·0 lb. 4. Relationships between digestible organic matter intake and liveweight were calculated and the merits of the exponents 0·62 and 0·73 of liveweight discussed. 5. The results were compared with accepted cow equivalent standards and, regardless of the exponent chosen, agreed with the system which adopts higher values for young grazing cattle.

Factors affecting voluntary feed intake in pigs. II. The effect of two levels of crude fibre in the diet on the intake and performance of fattening pigs

1. Voluntary feed intake, performance and carcass quality were studied with 20 individually housed pigs given isocaloric diets (2,770 kcal/kg. DM) containing either 8·9 % or 12·9 % crude fibre in the dry matter over the period of growth from 45 to 91 kg. live-weight. 2. There were no significant differences between diets in voluntary feed intake, rate of gain or carcass quality. 3. Apparent digestibility coefficients and rates of passage of the diets were determined in eight castrated male pigs. Rates of passage were not significantly affected by diet or live-weight when determined at 57 and 82 kg. live-weight.

The feed intake of milk cows. 1. Intake of winter rations during pregnancy and lactation and the influence of change to pasture.

1. For 4 weeks before calving in December or January a group of 7 Ayrshire cows each received daily 6 lb. hay and silage to appetite, whilst a second group of 9 received the same roughages and 6–10 lb. concentrates. After calving, cows from both of the pre-calving treatments were placed in each of two post-calving groups of 8 cows. A High treatment received approximately 8 lb./day more concentrates at the same milk yield than the Low treatment. Both groups continued to receive 6 lb. hay/cow/day and silage to appetite. The cows were allowed to graze by day from 21 February and by day and night from 13 April. Hay, at 5 lb./cow/day and reducing rates of concentrates were offered until 8 May. 2. Individual feed intakes were estimated from faecal output and digestibility. Direct measures of the intakes of different treatment groups on indoor feeding agreed fairly closely with the mean individual estimates. 3. The digestible organic matter intake (DOMI) of 1,300 lb. cows in the last stages of pregnancy was increased from 10 up to 14–16 lb./day by giving 8–10 lb./day concentrates. Immediately after calving, the increases in DOMI compared with pre-calving levels were about 2.5 lb./day for cows which received concentrates before calving and 8.5 lb./day for cows which received no concentrates before calving. 4. When all cows had calved and were in full milk production there were no significant differences in DOMI, milk yield or rate of live-weight gain attributable to pre-calving treatment. Mean DOMI on the High and Low post-calving treatments were 23.8 and 19.4 lb./day, mean fat-corrected milk yields 44.5 and 38.8 lb./day and mean rates of live-weight gain 05 and nil lb./day, respectively. 5. DOMI increased by 0.7 and 4.9 lb./day for High and Low post-calving treatments when cows were turned out to night as well as day grazing, and milk yields increased by 1.0 and 2.2 lb./day respectively. 6. Regression equations relating animal production and feed intake, and substitution rates of concentrate usage were calculated. Faecal output and DOMI were closely related to milk yield. When additional concentrates were given the resulting increase in total DOMI was greater when the bulk feed was of low digestibility than when it was of high digestibility.

Selection for carcass length in Large White pigs

A sib selection programme for length of carcass was carried out for five generations within a closed herd of Large White pigs. A generation interval of one year was obtained. Litter production was good throughout the project and the numbers of pigs born and reared in the final generation were 11·2 and 10·3 respectively. Overall response to selection was predicted with reasonable success. The increase in length was associated with an increase in number of vertebrae. Heritability for length of carcass computed from the pooled components of variance was 0·53 ± 0·12. Realized heritability was 0·5 ± 0·1. No control strain was maintained. Correlated traits moved in the expected directions and responses were beneficial for traits such as backfat measurements and chest depth, but unfavourable for belly thickness and ham conformation. Carcass acceptability was not good initially and this deteriorated during the project. The difficulties involved in maintaining selection pressure and herd size are discussed. Abnormalities and lameness were recorded and did not increase systematically over the experiment. It is suggested that the specific relationships between ‘conformation’, carcass value and viability require further investigation with particular reference to length of leg and length of carcass.

The effect of age and live-weight on the feed intake of grazing wether sheep

1. Estimates of the voluntary feed intake of three age groups of wether sheep on ryegrass and white clover pasture from July to October, 1962, were made by total collection of faeces and the use of local faecal nitrogen-digestibility regressions. 2. Average faecal output and intake of digestible organic matter (DOM) increased with age of the sheep. However, relative to body weight (W) or to W 073 , the aged sheep (5 years old), which did not change much in weight over the period, consumed only about two-thirds of the DOM consumed by the younger (sixteen- and four-month-old) growing sheep. 3. For the growing sheep intake was directly related to weight. Intake was calculated to be 24 W (kg.)–28 ±108 g. DOM per day. 4. The results are discussed in relation to the errors in estimation of digestibility. Comparison of the intake estimates with other published data suggests there was a high apparent maintenance requirement. The voluntary feed intakes observed, when expressed as g. dry matter per kg. W 0–73 , were somewhat higher for young sheep but lower for aged sheep than estimates of previous authors.

Milk production and herbage intake of dairy cows kept on a leader and follower grazing system

Three groups each of 14 cows, balanced for stage of lactation and potential milk yield, were kept either on a control treatment C, grazing within a rigid rotational grazing system, or on a leader (L) and follower (F) grazing system operated within a similar system. The stocking rate of treatment C was 5·76 cows/ha, the same as the overall stocking rate of treatments L and F. In Experiment 1, a 10-week continuous-type randomized block experiment was preceded by a 4-week uniformity period; in Experiment 2, a 3 × 3 Latin square design was adopted with periods of 4 weeks. Herbage intake and milk yield were only slightly, and not significantly ( P > 0·05), higher in the leader than control cows, whilst the performance of cows on treatment F fell significantly (P

Studies on Belgian Pietrain pigs 2. A comparison of growth and carcass characteristics of Pietrain used in three breed crosses with Landrace, Large White and Hampshire breeds

1. The growth, feed consumption per unit weight gain, carcass characteristics and some aspects of meat quality were studied in two trials with crosses derived from Landrace (L), Pietrain (P), Hampshire (H) and Large White (LW) breeds. 2. In Trial 1, 96 pigs of both pure Landrace and LW(× (L♀ × P♂)♂ origin were studied up to slaughter weights of 64 and 91 kg live weight. In Trial 2, Landrace, LW♀ × (L♀ × P♂)♂ and LW ♂x (P♀x L♂)♂, (H♀ × P♂ × L♂ and (H♀ × P♂)♀ × LW♂ pigs were compared up to 91 kg live weight using 48 pigs of each type. 3. All crossbred types showed better economy of production than Landrace when assessed by live-weight gain and feed consumption per unit weight gain. Their carcasses contained greater quantities of lean meat and similar quantities of rind, bone and fat than Landrace at comparable weights, but they exhibited a variable tendency to poorer meat quality. LW × (L × P) and LW × (P × L) carcasses at 91 kg live weight were shorter than Landrace; 4% and 14% of pigs in trials 1 and 2 respectively were less than the currently acceptable length of bacon pigs (775 mm). (H × P) × LW and (H×P)×L carcasses at this weight were much shorter; 34% and 38% respectively were less than 775 mm.

A note on the influence of a supplement of barley and dried lucerne on the intake of barley straw by cattle

Six castrated male cattle of 350 kg live weight were used in an incomplete Latin square design to measure intake and digestibility of barley straw offered ad libitum alone and with 5 levels, 1·5 to 7·5 kg/day, of a barley and dried lucerne concentrate. Straw intake declined and total organic-matter intake increased linearly with increasing concentrate level. On average 1 kg additional organic matter as concentrate, increased total organic-matter intake by 0·68 kg. There was no evidence that the crude protein content of the whole diet affected straw consumption.