This study was carried out on Bauscat (B), New Zealand (N), Californian (C), N × C (NC) and B × NC (BNC) rabbits. Overall reproductive performance for does with premature parturition (pre-term) of the five breeds was determined and compared with that of does delivering at the normal time (full-term). Full-term does showed a reproductive performance superior to that of pre-term does in all five breeds with larger litter size at weaning, more pups weaned per doe and a lower proportion of stillbirths. Pre-term B, N and BNC does had a larger number of pups weaned than pre-term C and NC does (P < 0·01). There was a high incidence of pup mortality in premature litters, and the main causes of this high mortality were respiratory distress syndrome, crushing of the skull and starvation and chilling.

The mean serum oestradiol 17-β concentrations and degrees of cervical mucous ferning in pre-term B does were higher than in full-term does (P < 0·01) but the mean serum progesterone concentrations in pre-term B does were lower than in full-term does during the gestation period (P < 0·01). Treatment with either dexamethasone or progestin reduced pup mortality in pre-term does and the birth-to-remating interval was shorter in pre-term does treated with dexamethasone (P < 0·01) but longer when treated with progestin (P < 0·01).

The fibrous residue remaining after juice extraction from the sugar cane stalk is commonly referred to as bagasse. It consists mainly of the ligno-cellulosic polymer matrix and small amounts of ash and water soluble solids which are mostly sucrose. In sugar industry mills, most of the bagasse is used as fuel, and although figures vary within each factory, energy efficient units can have 2 tonnes of surplus bagasse (dry basis) per 100 tonnes of fresh cane processed (Rolz et al). The bagasse can be supplemented with urea and legume protein in cattle diets. Research in Mauritius (Wong et al. 1974) showed that high pressure steam treatment (200°C) for 2-5 minutes raised rumen “in situ” digestibility from 30 to 60%. Subsequent work (Naidoo et al.1977) emphasised the critical role of supplements providing bypass nutrients (protein and glucose precursors) , in addition to urea-N and minerals for rumen microbes. In Colombia this technology is now being applied commercially for cattle fattening, using the foliage from the legume tree, Gliricidia sepium as the main source of bypass protein.

Malt distillers grains (MDG) and brewers grains (BG) are the fibrous residues remaining after the extraction of sugars from malted barley during the process of malt whisky and beer production, respectively. MDG and BG are popular supplements in beef finishing diets with up to 15kg/head/day being fed on Scottish farms (Lilwall, Smith and Wood, 1983). However, in some areas, close to distilleries and breweries, and particularly during the summer months, MDG and BG can be bought cheaply and ensiled, and could be fed to appetite as the sole or major part of the diet. This investigation explores this possibility.

Some unusual limitations of MDG and BG as a complete diet are that they are virtually devoid of soluble minerals such as Na and K and are low in some trace elements and vitamins. They also contain high levels of unsaturated fats which depress fibre digestion and voluntary dry matter intake (Miller et al., 1970). This effect can be partly overcome by supplementation with calcium carbonate (El Hag et al., 1972) probably by the formation of insoluble calcium soaps of fatty acids in the rumen. Based on these considerations a mineral/vitamin mix was designed specifically to supplement these materials.

A large variety of processes - physical, chemical and/or biotechnological - is currently applied to cereals (Table 1).

Among physical treatments, grinding is the most comnon ; it does not modify the chemical characteristics of the grains but improves the accessibility of the enzymes of the gut to their substrates by disrupting endosperm and aleuron cell walls. Thus, milling exposes the interior parts of the grain to the digestive enzymes. Some physical processing of barley grain, such as rolling, is necessary to give optimum digestion of the nutrients by cattle (ORSKOV, 1976). This treatment, applied to barley, appears to be beneficial for young species (KREFT and BOYLES, 1989). Pigs eat whole or very coarsely milled grain reluctantly (MAXWELL et al., 1970) and utilize whole barley poorly (LAWRENCE, 1970). For this reason, barley grain is commonly milled before feeding. Grinding of maize using a roller mill does not modify average daily gain, feed intake, feed conversion and fattening time of pigs. However, sensory evaluation tests, meat from control pigs fed untreated maize is preferred to meat from pigs given rolled maize (ITOH et al., 1986). However, finely ground barley causes a strong increase in the frequency of oesophagogastric lesions whereas diets countaining coarsely ground barley or crushed oats caused few lesions. Balance trials on lamb indicate that whole maize have more digestible, metabolizable and net energy than ground maize (BONSEMBIANTEE et al., 1988).

Active immunisation against androstenedione (Fecundin, Coopers Animal Health) increases ovulation and lambing rates. A study undertaken during the 1984-85 breeding season in randomly cycling ewes mated during October and November showed an increase in lambing rate of 24 lambs/100 ewes mated amongst ewes treated with Fecundin (Vipond, Keeling and Hunter, 1986). Fecundin increased the Incidence of triplet and quad births, suggesting that the greater benefit from the product would be derived in a situation where management could ensure the survival of additional lambs. The early lambing flock is such a case. Ovulation rates tend to be lower than later on in the breeding season, so fewer triplets might be expected amongst treated ewes. Management tends to be of a high standard, and the value of the early finished lamb is high.

Male beef calves in northern Australia are generally castrated under 6 months of age as an aid to management of animal behaviour and for the purpose of producing sufficiently fat carcasses at slaughter. It is also common for beef producers to administer hormone growth promotants, such as oestradiol, to increase the growth rates of steers at pasture. This experiment tested the hypothesis that delaying castration by 9 months would produce an increase in growth rate for the period while the cattle are retained as bulls without compromising management of animal behaviour. Bulls of three genotypes were castrated at 7 months or 16 months of age and half were treated with oestradiol after castration. Body weight (BW) and serum insulin-like growth factor-1 concentrations (IGF-1) were measured and behaviour was observed before and after the 16 month castration. At both 7 and 16 months of age, surgical castration of bulls caused no animal welfare problems. BW gain was affected by genotype with Bos taurus types having a lower BW gain than Bos indicus and F1-cross cattle. IGF-1 was similarly affected by genotype. Oestradiol treatment increased growth of the steers (early castrates) during the 9 months between castration times compared with non-implanted steers and bulls. Oestradiol implanted steers had similar BW gain from the late castration to slaughter, regardless of age at castration, which was greater than non-implanted early castrates which, in turn, was greater than the late castrates. Similar differences were observed for IGF-1 concentrations. Behaviour was not affected by genotype, oestradiol treatment or age of castration but this may have been an artefact of the design where all treatment groups were grazed together. Although delayed castration resulted in no behavioural or management problems, it did not produce a commercially useful increase in growth rate.

The fatty add profile of pig fat has profound effects upon both the eating and keeping quality of pig meat. Fatty adds within carcass fat may arise from two discrete sources, being de novo synthesis and direct deposition from fatty acids present In the diet. The relative contribution of these two routes, together with the fatty acid profile of dietary fat, will Influence the chemical composition of carcass fat. It is well established that diets containing high levels of unsaturated fatty acids will result in softer and oilier carcass fat and It Is often considered inappropriate to feed such diets during the finishing phase of pig growth. However the speed with which carcass fat reflects a change in dietary fat has not been quantified. The objective of the current trial was to measure the rate of change in fatty acid profile of carcass fat of finishing pigs following major changes in dietary fat.

There is increasing interest in the development of systems in which crossbred ewes are lambed later in the spring so that the ewes’ nutritional needs are matched more closely with grass growth (Stone, 1988). Lambs may then be sold as stores in the autumn or finished indoors on silage-based diets through the winter (Povey and Webster, 1987). However, ovulation rate tends to be declining at the time of mating in such a system. These experiments were designed to investigate the benefits of using Fecundin, either alone or in conjunction with pregnant mares’ serum gonadotrophin (PMSG) in synchronized ewes lambing in April/May.

Two groups of 30 Mule (Bluefaced Leicester x Swaledale) ewes matched for age, weight and condition score were allocated to the experiment. Treated ewes were given 2 x 2 ml intramuscular (i.m.) injections of Fecundin®(Coopers Animal Health) four weeks apart while control ewes received no Fecundin treatment. Unfortunately a ram escaped into the flock prior to the planned mating date. All ewes were therefore injected i.m. with 1.5 ml Lutalyse®(Upjohn) 12-16 days after suspected mating. However, it would appear that the dose used was insufficient to cause abortion and only those ewes marked subsequently by a raddled vasectomized ram remained in the experiment. All these ewes (n = 17 per group) were treated with progestagen-impregnated intravaginal sponges (Veramix® Upjohn) left in situ for 12 days. Rams were introduced on 18th December 1986, two days after sponge withdrawal and four weeks after the second injection of Fecundin. The ewes were shorn and housed prior to ram introduction and given a diet of hay ad libitum with up to 1 kg concentrates by the time of lambing in May 1987.

1. Two groups of ewes were given a dietary supplement containing 40 g of either ‘protected’ tallow (PT) with only 3% linoleic acid or ‘protected’ safflower oil (PP) with 57% linoleic acid for 28 days prepartum and 30 days post-partum.

2. Although the birth weights of the lambs were unaffected by dietary treatment, the lambs in the PT group gained weight approximately 20% faster than those in the PP group.

3. The gross compositions of the milks of both groups of ewes were similar but the milk fat obtained from the PP group contained about twice as much linoleic acid as was found in the PT group.

4. Dietary treatments did not affect the haematocrits, red blood cell (RBC) or white blood cell numbers of the lambs. However, the haematocrits were higher at birth than at 10 days later and the RBCs were found to be less fragile at birth than at 10 days later.

5. The ratio of trienoic/tetraenoic fatty acid in the plasma lipids of the lambs was positively correlated with live-weight gain. Male lambs grew faster than females and twins faster than triplets and the trienoic/tetraenoic ratio was higher in males than females and higher in twins than in triplets.

6. These results showed that although it was possible to increase the linoleic acid content of the milk of ewes and of the blood lipids of their lambs by feeding protected safflower oil, no increase in lamb growth was obtained.

There is now a considerable volume of evidence to indicate that, with high quality, grass silage-based diets, good animal performance can be achieved by offering supplements of high crude protein content at much lower levels than would be required with conventional supplements. Given the current constraint on milk output at farm level, there is considerable interest in lower cost milk production systems and high protein supplements would appear to have a role to play in this context. However, there is little information available which enables prediction of milk yield responses to increasing levels of supplements of differing protein content. The objective of this study was to determine response curves to supplements of differing protein content, given in addition to grass silage, thereby facilitating a least-cost diet type approach to achieving a given level of milk output.

Concentrates containing either 100, 220, 340 or 460 g crude protein (CP)/kg fresh weight were offered to 72 autumn-calving dairy cows from day 14 of lactation, with each concentrate offered at four levels of feeding.

Cattle not fed a supplement on dry season grazing lose weight. The magnitude of this loss and the extent of recovery during the subsequent wet season were measured in Mashona steers.

Mashona steers aged 8 and 20 months at the outset (groups A and B respectively) were used. Within each group (n = 50) steers were fed cottonseed meal (CSM, 250g per 100kg live-weight) or not fed CSM during the dry season.

The firmness of backfat in pigs is an important aspect of meat quality which is influenced by the chemical composition of the fat tissue. This is affected by the amount (thickness) of fat and by diet. Thin backfat Is relatively soft but nutritional manipulation can potentially overcome this problem.

This work compared fat thickness in pigs on a commercial farm fed a concentrate diet (CD) or a skimmed milk - balancer diet (SM). The low level of oil in SM was likely to be a key factor in increasing firmness.

Circumstantial evidence exists that supplementing short daylengths in cattle increases productivity by reducing activity rates (Phillips and Schofield, 1989), and stress (Leining et al, 1980). However, little is known about the preferred daylength or light intensity for cattle. Before the latter can be determined the ability of cattle to distinguish intensity differences must be determined. Two experiments are reported here: the first describes the ability of cattle to distinguish light intensity differences and the second describes their preference for supplementary light and the effect that it has on their behaviour.

In three successive experiments 32, 30 and 32 autumn-calving, single-suckled cows were subjected to individual planned weight reductions over winter on silage-based diets with various levels of concentrate supplement. At a similar level of weight loss, milk yield and calf gain were increased when protein supplements of low rumen degradability were given. On average, the inclusion of 0·75 kg fish meal in the diet improved calf gain by 0·13 kg/day. Results are discussed in terms of the effect of protein supplement on the efficiency of use of body reserves.

Urea treated Whole Crop Wheat (WCW) provides a stable, alkaline high DM forage, which is a potential replacement for, or complement to grass silage. Harvesting at about 600 g DM/kg facilitates both optimum crop DM production and energy concentration within the crop. Urea treatment (40 kg/t DM) at harvest prevents fermentation during storage, and may increase the crop digestibility. The nitrogen status of the forage as ammonia is also increased. The aim of these experiments was to investigate the feeding value of WCW for dairy cattle, when offered as the sole basal feed.

A spring wheat crop (var. Axona) was cut at about 600 .g DM/kg (hard dough stage), chopped using a conventional forage harvester and stored in an outdoor clamp silo. Urea was added at 40 kg/t DM during harvesting. After rolling, the clamp was sheeted with polythene for 125 days until feed out.

Energy is a major currency and resource in ecological systems. It is essential that the energy flows in such systems are understood for effective control of the production of livestock. With growing, lactating or pregnant cattle the farmer is faced with the problem of feeding to give optimum results. He needs to be able to predict the effects of feed quality, quantity and its distribution in time. Central to this problem is the prediction of how energy is used by the cow, for the competing processes of growth, lactation and pregnancy. The purpose of this paper is to introduce a deterministic model, NOSCOW, of the bioenergetic system for lactating, and pregnant, cattle. The model uses the recommendations of ARC (1980) as a base but includes the key ideas of potentials for lactation and growth. Twelve input factors are required by the model. The output is a time series with a weekly time step.

Pollution problems caused by silage are mainly odour and effluent production.

Odour can be virtually eliminated by ensuring a satisfactory silage fermentation, i.e. a low pH and a low ammonia concentration in the total nitrogen. This can be achieved by following the basic rules of good silage making, including the correct use of an effective acid additive.

Effluent is the major problem, particularly when it enters drains and water courses. This is because a typical effluent will have a pH of approximately 4.0 and a high 5-day biological oxygen demand (BOD5) up to 90 000 mg O2, per 1. This compares with BOD5, values of 5000 and 500 mg O2 per 1 in cow slurry and untreated domestic sewage respectively. Thus silage effluent in water courses removes the dissolved oxygen and will kill fish and other aquatic fauna. Effluent from a silo containing 300 t of low dry matter (DM) silage is equivalent in BOD5 to the daily sewage from a town of 80 000 people.

In some pig herds it is common for 20% or more of pigs born alive to die before weaning, indeed the national average across all herds is approximately 12% (Meat and Livestock Commission, 1983). A large number of these deaths are caused by Esherichia coli, of which up to half are caused by the K88 serotype (Walters and Sellwood, 1982). Several reports (eg. Gibbons, Sellwood, Burrows and Hunter, 1977) have shown that resistance to K88 E. coli is inherited as a simple Mendelian recessive. Of potential practical significance is the evidence that suggests that the sole use of resistant boars within a herd would prevent any K88 scour since the only susceptible progeny produced would be born to susceptible dams which would provide passive maternal protection to their piglets. However, the obvious advantage in using resistant boars in a herd would be nullified if performance of the offspring was significantly lower in important economic traits. Two trials on different farms were set up to investigate this possibility.