Milk protein concentration can be influenced by dietary manipulation, but the efficiency of amino acid transfer into milk and the predictability of the response are both poor. Previous reports from this research group have demonstrated that milk protein concentration can be repeatedly increased in response to vascular infusions of essential amino acids (EAA) in animals fed on a low crude protein (CP) diet (140 g CP/kg DM) in mid-lactation (Metcalf et al., 1996). The present study was designed to compare milk protein content responses to vascular EAA infusion in animals fed a high protein diet (180 g CP/kg DM) at peak lactation.

Previous work by this group (Metcalf et al 1996) has shown that milk protein concentration can be increased by jugular infusion of different mixtures of amino acids (AA). The current experiment was designed in part to investigate which groups of AA had the greatest effect in stimulating milk protein content.

The overall efficiency of nitrogen utilisation by ruminants is variable, but often very low. The efficiency of capture of degraded nitrogen by rumen microbes is an important determinant of the overall efficiency of utilisation of nitrogen by dairy cows (Dewhurst et al, 1996). Existing marker-cannula techniques for assessing rumen microbial efficiency, and their derived models, do not provide a useful description of the situation on individual farms. There is considerable scope for and improvement in the efficiency of utilisation of nitrogen within dairy systems if a simple diagnostic test of rumen function could be applied. It is envisaged that such a test would contribute to more refined use of protein supplements. A considerable amount of work (see review by Stangassinger et al, 1995) has shown that urinary allantoin excretion is a good index of microbial yield which closely correlates with duodenal flow of purine bases (which originate largely from rumen microbes). However, urine samples are not easy to obtain in the practical situation and so this work investigated the possibility of using allantoin in milk (which is easily sampled) as a microbial index by comparing it with urinary allantoin (the existing technique) and milk protein yield (a product of microbial protein).

Widescale on-farm assessment of microbial protein supply by urinary purine derivative (PD) excretion in dairy cows is restricted by the necessity for a total urine collection. Evaluation of urinary creatinine (c) excretion as a marker of urinary output, indicated the use of spot urine sampling to be unreliable (Shingfield et al 1995a). Further investigations have indicated that, based on mean treatment measurements, milk allantoin excretion and concentration are closely correlated with fermentable metabolisable energy (FME) supply, over a narrow range of milk yields (Shingfield et al 1995b). The current experiment evaluates the potential of milk allantoin excretion and concentration as a index of microbial protein supply over a much wider range of milk yields.

In a number of tropical countries, sugarcane is a readily available forage for dairy cattle. However, milk production with unsupplemented sugarcane is generally low, and animal performance can improve when supplements are added to the diet (Preston and Leng, 1980). Leguminous trees and bushes potentially provide a cheap supplementary source of nutrients. A simple mechanistic model of digestion of sugarcane in cattle has been constructed to assist in the search for suitable supplements (Dijkstra et al., 1996). The aim of the present paper is to investigate the optimum supplementation levels of Leucaena leucophala for milk production on sugarcane based diets, using this model.

Trace mineral supplementation of feed rations is commonly achieved by the addition of simple inorganic salts. The bioavailability and hence the performance enhancement achieved by trace mineral supplementation is significantly improved if the metal is added in the form of a peptide complex or chelate. Extracts from the Yucca shidigera plant bind ammonia in-vivo and thus may alter rumen fermentation and in turn milk synthesis. The aim was to determine the effects of a supplement (All-Plex, Alltech Ireland) included at 10g/day, on milk yield, milk composition, somatic cell counts (SCC), reproduction parameters and blood copper, zinc selenium and haemoglobin. The supplement contained proteinated minerals (100mg copper, 300mg zinc, 300mg manganese, 2mg selenium) and a yucca extract (1g Dc-Odorase, Alltech Ireland).

The grazing dairy cow is at risk of sodium (Na) deficiency because of the large output of Na in the milk and low sodium concentration in forages (Chiy and Phillips, 1995). During mastitis plasma containing Na, Cl, immunoglobulins and other blood proteins leaks into the mammary gland and secretion declines, thereby reducing K and lactose concentrations in the milk (Schar and Funk, 1986). The Na content of mastitic milk is usually increased by 150-300%, which helps to limit the growth of bacteria, such as Streptococci, that are sensitive to the Na concentration of their growth medium (Skarvdova, 1989). Such an increase in Na output could easily create a negative Na balance and, as the cow has negligible reserves of this mineral, effective control of the intramammary infection may depend on adequate Na status (Janota-Bassalik et al., 1985).

It is well documented that cows exhibit an increase in physical activity around the time of oestrus (Kiddy, 1977). Pedometers are receiving a great deal of attention to automate and record the cow activity data. Some previous field studies indicate that pedometers are superior to casual observations (Kiddy, 1977 and Redden et al, 1993). However, others show limited success due to a large number of false positive identifications (Moore and Spahr, 1991). The aim of the experiment was to investigate the possibility of using twice daily pedometer readings in determining activity to predict oestrus in dairy cattle under UK management.

Fertility after prostaglandin (PG) may be compromised by the variability in timing of oestrus and ovulation, which are in turn influenced by the ovarian follicular status at the time of injection. Gonadotrophin-releasing hormone (GnRH) treatment in the luteal phase a few days before PG can reprogramme and thus synchronise preovulatory follicle development (Wolfenson et al., 1994). A second GnRH treatment can then be given after PG, to further improve the synchrony of ovulation (Pursley et al., 1995). The present experiment was carried out to test the effect of this combined GnRH - PG - GnRH regime on ovarian function and steroid hormone production in dairy cows.

The in situ technique has been used widely to assess the degradation of feeds in the rumen. However, very little information is available on the degradation of feeds in the digestive tract of equids. This experiment examines the degradation of unmolassed sugar beet pulp (USBP), hay cubes (HC), soya hulls (SH) and a 2:1 mixture of oat hulls:naked oats (OH) in the caecum of ponies.

Four caecally fistulated Welsh cross pony geldings (approx LW 250 kg) were offered ad libitum grass hay (DM: 926, CP: 69; NDF: 649) plus 30 g/h/d of a horse mineral supplement. Two incubation bags (monofilament polyester, 6.5 x 20 cm, 41 um pores, 16 mg/cm2 sample size) containing either USBP or HC were incubated in the caecum for fixed times according to both a forward (0,3,5,16,8,24,48) and reverse (48,24,8,16,5,3,0) incubation sequence.

Previous work as shown that incubation sequence has no effect on the degradation profile of feeds in the rumen of cattle and sheep. However, compared to the rumen the equine caecum is small, digesta passage rate through it is fast and total digesta volumes can vary widely. Consequently, this experiment examines the effect of bag incubation sequence on degradation co-efficients in situ in the equine caecum.

Four caecally fistulated Welsh cross pony geldings (approx LW 250 kg) were offered ad libitum grass hay (DM: 938, CP: 70; NDF: 728) plus 30 g/h/d of a horse mineral supplement. Duplicate incubation bags (monofilament polyester, 6.5 x 20 cm, 41 um pores, 16 mg/cm2 sample size) containing a commercial horse concentrate (DM: 918, CP:151, NDF: 403) were incubated in the caecum for fixed times according to both a forward (0,3,5,16,8,24,48) or reverse (48,24,8,16,5,3,0) incubation sequence.

Alkanes occur naturally in all plants, although forage crops tend to have higher alkane contents than cereals. N-alkanes have odd-numbered carbon chains. They are ideal for use as markers in feed trials, because, they are inert, indigestible and naturally occurring, and can be recovered in animal faeces. Synthetic alkanes (even-numbered carbon chains) are available commercially and can also used as external markers. Dove and Mayes (1991) cite evidence indicating that faecal recovery of alkanes in ruminants increases with increasing carbon-chain length. Thus the alkane “pairs” (e.g. C35 & C36, and C32 & C33) are used in calculating intake and digestibility because they are long chain and adjacent to each other. However, recent work by Cuddeford and Mayes (unpublished) has found that in horses the faecal recovery rates are similar regardless of chain lengths.

The mobile bag technique has been employed to study the small intestinal digestibility of feed components in ruminants and total tract digestibility values in pigs. This study reports some preliminary investigations on the use of mobile bags to estimate both total and partial tract digestibility values in ponies.

Four caecally fistulated Welsh cross pony geldings (approx LW 250 kg) were offered ad libitum grass hay (DM: 918, CP: 73, NDF: 716) plus 30 g/h/d of a horse mineral supplement. Mobile bags were prepared from monofilament polyester mesh with a pore size of 41 um using a commercial heat sealer and were used to estimate the feed constituent digestibility of a commercial horse concentrate (DM: 918, CP: 151, NDF: 403) in both the total tract and post-ileal segments of the ponies digestive tract.

Hay is an usual component of horse diet. Nevertheless, it is suspected to provide some spores causing chronic obstructive pulmonary disease. Grass silage has been suggested as forage in the diet to overcome the problem. It was therefore of interest to assess the nutritive value of grass silage in horses.

Three silages with different dry matter (DM) content were compared. Since horses dislike grass silage with a low DM content, wilted silages only were compared. The first two were first cut grass silages with a low DM content at 427.3 g/kg (LGS) or a medium DM content (661.7 g/kg - MGS). They were compared with a second cut silage from grass grown under very dry conditions (HGS - 787.5 g/kg). The grass was ensiled in square big bales. The 3 silages were offered alone and ad libitum to 4 sport horses in 3 consecutive periods,each silage being offered during one period.

Zinc (Zn) is reported to influence the coat and skin condition of many animals including the dog (Van Dem Broek and Thoday, 1986). Recent studies indicate that in addition to the zinc concentration, the form in which dietary zinc is supplied influences the animal's zinc status (Power, Cashman and Flynn 1994) and coat (Lowe, Wiseman and Cole, 1994). The purpose of this study was to examine the effect of dietary zinc supply on the dimensions, weight, and zinc content of hair as these criteria are considered indicative of coat condition.

The camel is an important source of meat and milk in arid and semi-arid lands but estimates of its productivity show considerable variation. The anatomy of the camel and its nomadic management existence, make it difficult to obtain accurate live weights using standard techniques. Formulae for estimating the live weight of camels in various countries have been published using thoracic girth, abdominal girth, shoulder height, or a combination of all three measurements. The aim of this study was to determine the accuracy of biometrical measurement to estimate the live weight of camels of different ages and breeds in Kenya and to compare the results with those of other researchers.

Estimates of camel lactation yields in the literature vary from less than 1000kg to more than 12000 kg, with mean daily yields from 0.1 to 35kg (Simpkin 1985). Suckling or milking frequency and strength of the milk letdown reflex are just two of many factors that affect milk secretion rate in camels. Most of the 18 million camels in the world are kept in nomadic pastoral herds where estimation of milk yield is particularly difficult and the large variation in reported camel milk yields could be attributed to the methodology used to estimate yields. A literature survey shows most articles are based on infrequent observations on small numbers of animals over a short period of lactation and fail to state the experimental conditions or whether figures represent milk offtake for human consumption or total milk yield.

A method to determine body measurements by computer image analysis of lamb photographs was described by Komlosi (1994). It was suggested that the technique could be used to predict conformation of live sheep, particularly candidate breeding rams. This study was conducted to evaluate the reliability of lamb body measurements derived using this technique.

Thirty lambs (Border Leicester (4), Texel (16), Suffolk (10)) were used. Reliability estimates were obtained from repeated (5 replications) photographs of the same animals and from repeated measurements (4 replications) of individual photographs. Eight lamb body measurements were used in this study namely, body length (BL), height at withers (HW), height at hip (HHP), hind-quarter horizontal distance (HQH), hind-quarter diagonal distance (HQD), hind quarter area (HQA), side area (SA) and rump diagonal (RUD). These measurements are as described by Komlosi (1994).

Blood measurements which can be taken on animals undergoing performance tests may be useful aids to selecting genetically superior animals. Possible useful measurements may be identified by correlated responses to selection, in selection experiments. This study investigates correlated responses in volatile fatty acids (VFAs) and blood metabolites, associated with growth and fat metabolism, in sheep selected for carcass lean content.

Birth weight (BW) and gestation length (GL) have important implications for the survival and early vigour of the lamb, in turn affecting the early growth. In hill sheep BW and early growth have low heritabilities, when considered as a trait of the lamb. They are highly influenced by maternal genetic effects and non genetic effects such as litter size, date of birth and the environment. When studying hill sheep there are also problems obtaining accurate records of birth weights and early growth and it is normally impossible to obtain accurate measures of GL. Exploitation of the genetic variation in the traits BW, GL and early growth could be useful in breeding programmes to reduce early mortality and improve vigour in lambs.