Under conventional husbandry conditions, Matabele goats kid all year round and, as they receive no supplementary feed, they are frequently exposed to periods of feed scarcity. The aim of this experiment was to determine maternal and foetal responses to different feeding levels during pregnancy.

The work was carried out at the Thuli Breeding Station, in Matebeleland, south western Zimbabwe. Forty-two Matebele goats carrying single kids were individually penned and randomly allocated to each of three treatments as they reached week 14 of gestation. The treatments were; Low (L)=0.25 MJ ME / kg0.75, Medium (M)=1.5xL and High (H)=2.5xL. Whole maize grain, lucerne hay and veld hay (see Table 1) were offered at levels calculated to provide 0.2, 0.24 and 0.56 of the total ME. Drinking water and an iodized mineral lick were available to all goats ad libitum. Feed intake was measured daily. Does were weighed and body condition scored (on a scale of 1-10) weekly and within 8 hours of parturition. Kids were weighed at or soon after birth.

Under conventional husbandry conditions, kid mortality of Matabele goats is highest in the dry season when feed is scarce. The aim of this experiment was to determine maternal and kid responses to feeding levels during lactation.

The work was carried out at the Thuli Breeding Station, in Matebeleland, south western Zimbabwe. Forty-two Matebele goats that were fed differentially (H, M and L levels) pre-partum, were fed at either HL (1 ME MJ/W0.75) or LL (0.60 ME MJ/W0.75) as from the second week of lactation until week 15. All the does had single kids. The allocation to lactation treatments was balanced for pre-partum feeding levels. Maize grain, lucerne hay and veld hay were offered at 0.2, 0.24 and 0.56 of the total ME per treatment. Drinking water and an iodized mineral lick were available to all goats ad libitum. Feed intake was measured daily. The does and kids were weighed weekly; does were also body condition scored (on a scale of 1-10) at each weighing. The does were hand-milked weekly after separation of the kids for 4 hours (0900-1300). The milk was weighed and a sub-sample preserved for subsequent chemical analysis.

There is considerable interest in the production of Cashmere fibre by goats in the UK. Cashmere is a fine fibre produced by goats of many genotypes and crossbreeding programmes involving animals imported from overseas countries and indigenous goats have recently been established.

Further information is required on the production and physiological characteristics of goats produced in these programmes. The objective of the present study was to determine milk production, vitamin and immunological status of goats as affected by prepartum housing date and buck genotype.

The response in yields of milk constituents to increases in the amounts of standard dairy concentrate (SC, 200 g crude protein (CP) per kg DM) given to cows consuming grass silage ad libitum were reported recently (Aston et al 1991; Baker et al 1991). A change of level however adjusts the supply of both energy and CP. Previous work also showed .linear responses in silage intake and milk and milk protein yields when CP was increased in a fixed ration of concentrate of constant energy value. In this trial energy and CP levels were varied Independently. The objective was to separate the effects of energy on the performance of lactating cows from those of CP.

Carbohydrates in dairy concentrate originate from cereals containing high starch and a variety of by-products with high levels of fibre. Selection is based on unit cost and chemical analysis. Comparisons between starchy and fibrous sources were made at a single level of crude protein (CP) by Thomas et al (1986) and Sutton et al (1987). Voluntary intake of forage increased and yields of fat and protein were similar when fibre replaced starch. The objective of this trial was to extend the range of comparisons by establishing the effects of three types of carbohydrate at four levels of crude protein given with grass silage ad libitum to lactating dairy cows.

The importance of measuring partition between body and milk in dairy cows and identifying the factors underlying it has long been recognised. However accurate measurements of partition In the body are few because of the difficulty and expense of the techniques.

The purpose of the present experiment was to measure the effects in autumn-calving Holstein-Friesian cows given grass silage ad libitum of amount of concentrate and stage of lactation on body composition by direct (Gibb et al 1992a, b) and Indirect (Kings et al 1992) techniques, adipose tissue metabolism (Walsh et al 1992) and milk production. In a related trial, energy balance was measured in other cows by Indirect calorimetry (Cammell et al 1992).

This report covers silage Intake, milk production and live-weight change. Communications on the associated studies are given in the Proceedings of this Meeting.

In order to understand the complex changes associated with lactation in the dairy cow it is necessary to assess the contribution of the non-carcass components. It has been shown with sheep (Cowan, Robinson, Greenhalgh and McHattie, 1979) that a number of tissues may be mobilised during lactation with a redistribution of tissues particularly towards the gut and udder, and that diet may have a significant effect. Butler-Hogg, Wood and Bines (1985), using Friesian dairy cows showed changes in the weights of guts, internal fat depots (omental, mesenteric and perinephric) and liver with stage of lactation although the number of stages examined was somewhat limited. The present experiment investigates changes in non-carcass component weights at 9 points over the first 29 weeks of lactation and with 3 levels of concentrate supplementation.

One of the major limitations in nutritional studies of lactation in dairy cows is the unknown contribution of body tissues to the energy status of the animal. Both fat and protein are thought to be mobilised in early lactation (Bauman and Elliot, 1983) when nutrient intake is insufficient to meet the demands for energy and amino acids. The present experiment investigates the effects of diet on changes in weights of chemically determined fat and crude protein (CP) in the carcass and non-carcass fractions over the first 29 weeks of lactation.

Body composition was measured by serial slaughter of autumn-calving dairy cows offered grass silage (206 g CP and 18.56 MJ GE per kg DM) ad libitum and 3(L), 6(M) or 9(H) kg DM/day of concentrate (206 g CP/kg DM)(Sutton, Aston, Beever and Fisher, 1992). Cows with post-calving live weights between 500 and 700 kg and previous lactation yields between 5000 and 7000 litres were used, and were blocked for parity and expected calving date before allocation across treatments and slaughter times. Six cows were slaughtered at 2 to 4 days post partum (week 0), and two from each treatment (one 2nd, and one 3rd or 4th parity) at 2, 5, 8, 11,14,19, 24 or 29 weeks post partum. After slaughter the right half carcass and all other non-carcass components were frozen and minced before chemical analysis for fat, CP, ash and water. All weights were adjusted by covariance for live weight post partum and parity. Energy content was calculated assuming values of 39.19 and 23.23 MJ/kg for fat and CP respectively.

Measurements of the velocity of ultrasound (VOS) through live animals have been shown to provide good estimates of the proportions of dissected fat and muscle in carcasses of beef cattle (Fursey, Miles, Page and Fisher, 1991). The use of this technique to measure more accurately the changes in body composition and energy content of the dairy cow over lactation would greatly assist in the interpretation of nutritional studies. Estimation of body reserves from live weight (LW) can be inaccurate due to changes in gut fill, tissue water contents and reproductive tissues, and condition scoring is highly subjective. The present study investigates the relationships of LW and VOS measurements at 3 sites with dissected fat and muscle in the half carcass and chemically determined fat and crude protein (CP) in the whole carcass and empty body.

In early lactation dairy cows use stored body fat to provide an additional source of energy to support milk production and these reserves are replaced when energy requirements for milk synthesis are reduced. The extent to which body fat is mobilized depends on the nutritional state of the animal and its genetic potential. These changes are accompanied by substantial alterations in the intermediary metabolism of adipose tissue. The aim of this work was to investigate the timing and magnitude of changes in synthetic and lipolytic pathways in adipose tissue from dairy cows during a lactation cycle and at three levels of energy intake.

Fifty four cows were fed grass silage ad libitum and a concentrate ration at 3(L), 6(M) or 9(H) kg DM/day (Sutton et al 1992). An initial group of six cows was slaughtered at 2 to 4 days post partum (week 0) followed by two cows from each treatment at weeks 2, 5, 8, 11, 14, 19, 24 and 29.

Previous experiments have demonstrated the effects of diet composition, energy substrate and stage of lactation on the energy balance of lactating Friesian cows (Beever et al 1989). The purpose of the present experiment was to extend these studies by measuring energy balance and respiratory exchange in parallel with direct measurements of changes in body composition by slaughter. (See accompanying summaries).

Nine cows were selected on the basis of age, parity, live weight and previous lactational performance to be similar to those in an associated feeding trial (Sutton et al 1992). They were allocated to 3 (L), 6 (M) and 9 (H) kg DM/day of concentrates (206g CP and 12 MJ ME per kg DM) with grass silage ad libitum (206g CP and 10.4 MJ ME per kg DM). Measurements of energy exchange were made at five stages of lactation, weeks 5, 10. 16, 22 and 28. Gaseous exchange was measured during each stage of lactation for 4 days using open-circuit respiration calorimetry followed by a 6 day collection of faeces and urine.

Adding appropriate fats to diets for dairy cows has the potential to improve the acceptability of dairy products to the health-conscious consumer by increasing the proportion of monounsaturated fatty acids in milk fat. However, concentrations of protein in milk are often concurrently depressed. In these respects responses to fat resemble those seen in animals in negative energy balance, where the contribution of fatty acids mobilized from adipose tissue to milk fat synthesis leads to similar changes in milk fat composition, and milk protein concentrations are relatively low.

These similarities give rise to two questions: (i) do the metabolic adaptations during negative energy balance influence the utilization of dietary fat for milk fat synthesis, and (ii) is the mechanism whereby milk protein is depressed the same in both cases? As a preliminary investigation of this, an experiment was conducted to compare the effects of dietary fat supplementation on performance of lactating cows either mobilizing or depositing body tissue.

The average freezing point of milk from dairy cows is -543m°H. A lower freezing point depression (FPD) is equated with extraneous water having been added to the milk. The validity of the test relies on the basic assumption that the natural variation in the freezing point of milk is small. Milk with a FPD of -530m°H is legally acceptable in the UK. However, average milk ex-farm has a FPD of -545m°H, encouraging those seeking higher milk quality to suggest a more stringent legal minimum. This experiment investigated the effects of feeding on FPD.

Nine local (indigenous) Zebu cows of average body weight 156 kg. were used to examine the performance in their first lactation given either fishmeal or wheat bran diets.

Fishmeal diet (A) consisted of 11.5 kg urea treated straw, 4 kg green grass and 0.25 kg of fishmeal. This diet contained an estimated 63 MJME, 518 g of rumen degradable protein (RDP) and 146 g of undegraded dietary protein (UDP). The wheat bran diet (B) consisted of 11.6 kg urea treated straw, 4 kg green grass and 0.5 kg wheat bran. This diet contained an estimated 66 MJME, 523 g of RDP and 91 g of UDP. Total dry matter intake of the two diets, A and B were 7.5 and 7.83 kg/d respectively. Therefore the two diets differed mainly in UDP levels. The composition and nutritive value of the ingredients of the two diets are given in Table 1 and 2.

Molasses has been fed to dairy cows for about a century. Extensive studies have shown that its energy value is worth from 75 to 100% that of maize when up to 10% of molasses is fed in a complete diet and high molasses inclusion in the diet can be detrimental to the responses of the animals. Nevertheless, the maximum inclusion rate of molasses in a diet that cows can tolerate has still been unclear. Few publications are available to describle the responses of cows to very high molasses feeding. This is a question, however, that both farmers and advisers are concious of. The present experiment was designed to evaluate the effects on milk yield and composition, feed intake, liveweight gain and health of lactating cows fed on very high levels of molasses, in comparision with those fed a relatively low level.

Fifteen British Friesian late lactation cows (168 ± 6 days calved) all in second lactation or more were randomly allocated to a 3 x 3 changeover experiment with 21 day periods. The cattle were fed individually through Broadbent Calan Gates ad libitum on a complete diet of silage plus a liquid supplement including molaferm 20 (a mixture of 80% cane molasses with 20% condensed molasses solubles supplied by United Molasses Ltd.), soyabean meal and fish meal.

Once-daily milking reduces fixed costs, may be used strategically as a quota-management tool and could become the production system of choice in a programme of extensification. However, milk secretion is reduced during once-daily milking, through the action of an autocrine feedback inhibitor. This natural milk protein is active in milk stored within the secretory tissue, but not in cisternal milk (since it is then remote from its site of action). Consequently, large-cisterned cows should tolerate infrequent milking better than those with small cisterns, by virtue of storing a greater proportion of their milk in a site where the inhibitor is inactive. The aim of this experiment was to test this hypothesis.

A group of 9 multiparous and 2 primiparous Friesian-Holstein cows from the Hannah herd calving in March and April 1991 were selected for study. All had been free of clinical mastitis during the current lactation. Throughout the experiment the group were managed routinely at grass as part of the main herd, and were fed a flat rate of 2.4 kg/d of an 18% protein concentrate feed. Normal milking was twice daily at 15:9 h intervals, and yield was recorded at each milking.

Rumen fermentation patterns are influenced by the quantity of starch in the diet and by the extent of digestion of the starch in the rumen. The extent of digestion of starch in the rumen can be influenced both by the source of starch (e.g. maize starch less digested than wheat starch) and by the method of processing the grain (starch from ground grain more digestible in the rumen than starch from NaOH treated grain). The objectives of this experiment were to compare the performance of dairy cows (a) fed different sources of starch (wheat and maize) and (b) fed wheat either ground or treated with NaOH, compared to a low starch control diet.

Colostrum and milk contain a number of important components such as immunoglobulins, fat soluble vitamins and essential fatty acids which have a marked influence on the health and welfare of the neonatal calf. The requirement of the neonatal calf for vitamin E is partly dependent on the dietary intake of polyunsaturated fatty acids (PUFA). Harris and Embree (1963) recommended that the ratio of vitamin E to linoleic acid (mg/g) should be between 1.5 to 2.5. Vitamin E is required to provide protection against peroxidative damage to the unsaturated fatty acids of plasma and membrane lipids and has been shown to play an important role in the development and maintenance of the immune system (Machlin and Bendich, 1987; Bendich, 1989). A study was conducted to examine the ratio of vit E to C18:2 in colostrum and milk and to investigate the effects of different dietary ratios of vit E to C18:2 erythrocyte membrane lipid composition.

Twelve Hereford x Friesian cows were used in this experiment. Seventeen calves born to these cows, five sets of twins and seven singles, were randomly allocated to four treatment groups as follows. Group A -untreated controls; groups B and C - supplemented with different levels of vitamin E; group D -supplemented with vitamin E and C18:2.

Intensive feeding systems for dairy cows based on a high proportion of concentrates in the diet are becoming popular in many countries where forage resources are scarce. The objective of this experiment was to examine the effects on high yielding cows of feeding diets containing either 700 g/kg dry matter (DM) concentrate or 500 g/kg DM concentrate when grass silage was the forage component.

Although many cows receive both commercial dairy compound feeds and straights, there is little scientific documentation of the effects of these dietary combinations on silage Intake and dairy cow performance. The objectives of the trial were to investigate the effect on cow performance or varying the level or compound and type and level of supplementary feed.