Animal production is commonly reported to increase when different animal species are grazed together on the same pasture (Nolan and Connolly 1977). In such experiments there is often a difficulty with interpretation of results due to a failure to establish equal grazing pressures between species mixtures, and confounded production differences may result. The theory behind the design of mixed experiments continues to pose problems (Connolly and Nolan 1976, Connolly 1984).

The experiment reported here was designed to investigate whether, when different animal species are grazed at the same pressure, there are differences in animal intake and/or diet composition when they are grazed singly or in mixtures.

Nineteen, 18-month-old steers, 40 yearling wether goats and 40 10-month-old wether sheep were grazed in New Zealand on a mature summer ryegrass/white clover pasture (4550 kgDM/ha) in 5 treatments: cattle alone (CA), sheep alone (SA), goats alone (GA), and cattle with sheep (CS, SC) and cattle with goats (CG, GC).

Hill farms vary greatly in size, soil and climate and each has its particular problems. The task of the scientist is to investigate each facet of production from the hill and to provide information which will improve the overall understanding of the potentials and limitations to output. From that understanding, the solutions to the problems of the individual farms may be derived.

Progeny of younger dams grow more slowly than those of older dams. When the environmental effects of dam age are not allowed for in selection for growth rate, selection differentials and genetic responses to selection are reduced.

In a model herd, with cows aged 2 to 8 years, it was found that neglecting the dam age effects reduced genetic gains by about 15% when selection is for weaning weight, and by 11 to 7 % when selection is at an age of 12 to 20 months. Much of the reduction occurs because of the selection of higher proportions from genetically inferior groups.

If genetic differences among dam age groups are small the reduction is only 7% at weaning and less at older ages. The effect of ignoring calf age was also estimated. It was found that if calves born within a period of 33 days were compared and calf age was neglected, the response to selection for weaning weight would be reduced by about 6%.

Inaccurate prediction of silage intake is often the greatest source of error in ration formulation but improvements have been hindered by an inadequate description of the silage fermentation in advisory practice. Until recently, only pH and ammonia N have been routinely measured as indicators of silage fermentation characteristics. A new method, based on research in Finland (Moisio and Heikonen, 1989) has been developed and is now in use by SAC. This involves automated titration of juice squeezed from the silage to pH 2 (with HC1) followed by stepwise titration (with NaOH) to pH 12. Concentrations of juice constituents are predicted from the buffering capacities measured over segments of the titration curve (pH 2 to pH 12). Calibrations have been obtained empirically by the addition of known increments of standards to a range of silage juices. Proportions of variance (R2) of measurements made by reference methods accounted for by predictions from titrations for a validation set of 93 silages were 0.90, 0.78, 0.92, 0.82 and 0.82 for lactic acid, acetic+butyric acids (VFA), soluble N, sugar and ammonia N respectively.

Ruminant production systems can have a negative effect on the environment within three main areas 1) loss of nutrients to aquatic environment, 2) loss of nutrient to the aerial environment and 3) contribution to the global increase in temperature (green house effect).

In Denmark area 1) is considered as a very serious problem in particular NO3-leaching from the agricultural land. Within area 2) the loss of NH3 from ruminant production is considered as a major problem. Concerning the green house effect (area 3)) the loss of N20, C02 and CH4 are considered as a problem in connection to ruminant production.

Previous work has shown that treating moist grain with ‘Farmline’, a formalin acetic acid mixture, affords some protection of protein and perhaps starch from rumen degradation. A comparison with and without ‘Farmline’ treatment investigated the protection afforded to dried barley.

One hundred and eight high genetic merit Holstein-Friesian heifers were used to determine the effects of rearing regime on the development of the mammary gland and claw abnormalities. Heifers were allocated to one of four rearing regimes at 7 weeks of age and slaughtered at 18 (s.d.0.7) months of age; mating commenced at 14 months of age. Treatment 1 heifers were reared to calve at 540 kg and treatments 2, 3 and 4 heifers reared to calve at 620 kg. Treatment 1 and 2 heifers were offered grass silage-based diets during the winter and grass-based diets during the summer; treatment 2 heifers received additional concentrates. Treatment 3 heifers were offered a straw/concentrate diet during the winter and a grass-based diet during the summer. Treatment 4 heifers received the same winter diets as treatment 3 but were housed and offered a straw/concentrate diet in summer. Increasing plane of nutrition increased the weight of dissected udder fat (P < 0.01), but had no effect on the weight or chemical composition of dissected udder parenchyma. Offering straw- compared with silage-based diets reduced fat deposition in the udder (P < 0.01) and increased the proportion of parenchyma in the udder (P < 0.01). Keeping heifers housed during the first summer and offering straw-based diets relative to those turned out to grass had no effect on weight of fat although there was a tendency towards a reduction in the proportion of parenchyma in the udder (P < 0.06). Heifers reared on a low plane of nutrition had lower values for heel height (P < 0.001), lateral claw length (P < 0.001) and heel erosion scores (P < 0.01). A higher plane of nutrition also increased live weight/sole area although this was only significantly higher for treatment 3 (P < 0.05) compared with treatment 1 heifers. Housing heifers in the first summer increased the incidence of feet lesions in the white line area and solear area relative to turning heifers out to grass in the first summer (P < 0.05).

Studies with sheep suggest that accurate estimates of herbage intake can be obtained by using the herbage alkane tritriacontane (C33) and dosed dotriacontane (C32) as markers, since the faecal recoveries of both alkanes have been shown to be very similar. To validate the technique for herbage intake estimation in grazing cattle there is a need to compare in cattle, the faecal recoveries of both herbage and dosed n-alkanes. It has been observed in sheep that the faecal recoveries of n-alkanes increase as their chain lengths increase, suggesting that the recovery of hexatriacontane (C36), an alkane absent from herbage but available commercially at low cost, should be complete. C36 may therefore have potential as a dosed marker for estimation of faecal output. Thus it may .30 be possible to obtain estimates of both herbage intake and diet digestibility in the same individual grazing animal using n-alkanes as markers. The purpose of the experiment described here was to determine the faecal recoveries in cattle of odd-chain n-alkanes from fresh herbage and of C32 and C36 dosed n-alkanes.

The aims of the experiment were to determine the intake, digestibility and particle passage kinetics of urea treated (40 g urea / Kg DM) whole crop wheat (UW), grass silage (GS) and a 0.5:0.5 UW : GS mixture (UG) on a DM basis.

The chemical composition of GS and UW were respectively, TDM (gTDM/Kg) 227, 648; NDF (g/Kg DM) 528,426; ADF (g/Kg DM) 346, 285; Ash (g/Kg DM) 74, 62; Starch (g/Kg DM) 3, 236; Nitrogen (g/Kg DM) 24.2, 30.2; Ammonia N (g/Kg TN) 91, 382; pH 3.9, 8.5; NCD (g/Kg DM) 681, 642 respectively.The UG was mixed daily, in an attempt to reduce selection of individual components by the animals.

The experimental design was based on two 3 x 3 latin squares with three animals per square and three periods of three weeks duration. Six Holstein Friesian x Brown Swiss pregnant heifers (mean liveweight 400 Kg) were used to assess (during the last 7 days of each period) the voluntary intake, digestibility and particle passage kinetics of the three forages.

The technology to measure individual feed consumption of pigs in groups using electronic feeders is a recent development. As well as providing information on total feed consumption and consequently feed efficiency it is also possible to examine feeding behaviour under normal social conditions (ad libitum feeding in groups). Changes in feeding behaviour over a performance test are of particular interest to determine if growing pigs increase consumption by larger meals, more frequent feeding or a combination of both.

Selection for high lean growth rate may lead to changes in both feeding behaviour and duration of feeding which could have undesirable side effects in a genetic selection programme. Increased feeding activity may lead to aggression and lost efficiency of feed conversion due to greater activity.

On hill farms where breeding cattle are kept there are advantages in retaining until the following spring at least a proportion of the surplus calves. The ability to winter them presents wider scope in choice of markets, while the sale of calves in spring, in addition to the dung produced, can provide a greater profit margin if wintering costs are minimised. Grass used efficiently in autumn offers an opportunity to reduce the requirement of the relatively expensive hay, silage, other crops and purchased feed. The value of extended grazing throughout autumn and winter months has been demonstrated by Smith (1953-4) for Blackface ewe hoggs, and for store stock and in-calf heifers by Hughes (1954) and Corbett (1954). In the case of calves, however, the period when late grass can be utilised depends on the continuance of moderate temperatures and availability of shelter from wind and rain, and therefore in most seasons will be relatively short. With these considerations in mind it was decided to compare the performance of two groups of weaned calves, one of which was housed and fed in courts immediately after weaning, while the other remained on grass for several weeks prior to court feeding.

Precise, unbiased estimates of genetic parameters, such as heritability and genetic covariance, are necessary to optimise breeding programs and to predict rates of change for various selection schemes. A classical method of estimation is to use high and low selection experiments. We consider two generation selection experiments when observations in the parental generation are only taken on one sex, resulting in half-sib family information. We consider cases of two standardised traits, with zero mean and unit variance, and assume that the traits are normally distributed. The genetic and phenotypic variance-covariance matrices for the traits are denoted by G and P respectively. The genetic variances and covariances of the standardised traits are then heritabilities and co-heritabilities.

The construction of other designs is examined, assuming the phenotypic correlation of rp between traits is known. For simplicity, comparisons of designs are developed by considering the variance of the genetic variances when the traits are uncorrelated both phenotypically and genetically.

Feeding pregnant ewes on silage-based rations during housing is widely practised. However, silage making is a capital intensive procedure and the cost is likely to increase due to pollution legislation. Feeding ewes on a cereal-based ration may be a cost effective alternative. This is especially relevant due to the ban on straw burning and the possibility of CAP reform forcing cereal prices down. This experiment compares the effect of silage- and wheat-based rations during the winter housing period on ewe and lamb performance.

Approximately 260 mule (Bluefaced Leicester x Swaledale) ewes were selected from the breeding flock at the time of winter housing in January 1989, 1990 and 1991. They had previously been at grass and had run with Suffolk rams between mid-October and mid-December.

A technique for evaluating beef carcasses in terms of their retail value, has been applied to 132 half-carcasses from seven groups of cattle (Jersey, Hereford, Polled Hereford, Lincoln Red, Devon, South Devon and Charolais × Jersey) to test the general applicability of the method, in particular the regression equations for predicting retail value. Significant differences in retail value were found between the groups of animals, South Devon and Charolais × Jersey having a high retail value per kg side weight, and Jerseys a low one. There was a very high correlation between retail value per kg side weight and the proportion of muscle in the side. Relationships between retail value and proportion of fat in the side were also investigated. It is not possible to decide, from these data, whether the differences found in retail value are a true breed effect, or whether they are due solely to differences in composition.

Previous experiments have shown important differences in milk production when mixed starch sources were replaced by mixed high quality by-products in high concentrate diets with hay as the forage (Sutton et al. 1987). The purpose of the present experiment was to compare rolled barley with sugar beet feed (SBF) in both molassed and unmolassed forms when given alone with grass silage in a high-concentrate diet. Additionally the effect of altering protein concentration of the concentrates was examined.

Effects of dietary protein concentration on the amino acid composition of sow's milk was studied using 10 crossbred first-litter sows. At parturition, diets containing similar concentrations of digestible energy but with either 63 or 238 g crude protein per kg and 4.4 and 15.1 g lysine per kg respectively, were given through lactation (five sows per treatment). The ratios of other amino acids to lysine were in excess of those currently recommended for lactating sows. Dietary protein level significantly affected milk yield, gave higher milk protein output (P > 0.05) but was without significant effect on the proportions of amino acids in the milk.

Four groups of 20 Simmental cross heifers were actively immunized against human serum albumin (control, (C), androstenedione (A), a 30 amino acid synthetic fragment of porcine inhibin alpha (I) or A and I in combination (AI). At the time of the third and final antigen injection and again 2 weeks later, all animals were injected with synthetic prostaglandin F2α (PG) to synchronize oestrus. Concentrations of LH, FSH, insulin-like growth factor-1 (IGF-1) and inhibin (C and A heifers only) in serum samples collected twice daily during 3 days before the second PG injection and at 15-min intervals from 24 to 32 h after PG injection were determined. Two weeks later, all heifers were administered PG and ovariectomized 24 h later. Ovarian follicles were dissected from the stroma, measured and cultured in medium 199 for 2h at 37°C. Numbers of small (3·0 to 7·9 mm diameter) and large (>8·0 mm diameter) follicles were not significantly altered by any of the immunization treatments. Intrafollicular concentrations and secretion rates of oestradiol, testosterone, progesterone and inhibin, determined in vitro, were not affected by immunization. Intrafollicular IGF-1 concentrations were not affected; this hormone was not detectable in the culture medium. Intrafollicular concentrations of oestrogen and testosterone and secretion rates of all three steroids were greater (P < 0·05) in animals which had regressing corpora lutea at the time of ovariectomy. Of the animals that had dominant follicles, one of 17, one of 13, four of 19 and six of 15 in the C, A, I and AI groups, respectively, had two or more. Only the difference between AI and C cows in the incidence of dominant follicles was statistically significant (P < 0·05). Mean circulating concentrations of LH, and inhibin (C and A groups only) and mean LH pulse frequency and pulse amplitude were unaffected by treatment but FSH concentrations were higher in A (P < 0·001) and lower in AI and I heifers (P < 0·001) compared with C animals while IGF-1 concentrations were lower in A heifers (P < 0·001) and higher in AI heifers (P < 0·05) compared with C heifers. It is concluded that immunization against inhibin, either alone or in combination with immunization against androstenedione increased the incidence of multiple dominant follicles in heifers but did not increase their ovulation rate.

Many trials at Reading have shown store lambs to be reluctant to eat straw when first housed after grazing. This is especially so if penned individually, as is often the case in feeding trials. Such isolation may induce stress, including depressed intake (Crampton, 1959; Kidwell, Bohman and Hunter, 1954). Farm animals are generally stimulated to eat more when in a group than when isolated (Curtis, 1983), yet most intake studies, particularly with sheep and cattle, are conducted with individually-penned animals. Concern for the welfare of animals being used for trials calls for systems of housing that minimise stress.

The present experiment tested the hypothesis that straw intake, by store lambs first-housed after grazing, would increase if lambs were penned in pairs rather than individually, or confined in pens allowing pen to pen vision rather than prohibiting pen to pen vision.

Calculating optimal truncation values for independent culling selection procedures has been difficult. Previously published charts took much of the tedium out of the calculations but the charts are difficult to read with accuracy and are not available for all possible parameter values. Therefore a computer program was written to calculate optimal truncation values for two-trait independent culling, with the option of restricting the genetic change of one or both traits. The program is described and an example of its use is given.

The aim of this study was to analyze the economic viability of producing dairy goat kids fed liquid diets in alternative of goat milk and slaughtered at two different ages. Forty-eight male newborn Saanen and Alpine kids were selected and allocated to four groups using a completely randomized factorial design: goat milk (GM), cow milk (CM), commercial milk replacer (CMR) and fermented cow colostrum (FC). Each group was then divided into two groups: slaughter at 60 and 90 days of age. The animals received Tifton hay and concentrate ad libitum. The values of total costs of liquid and solid feed plus labor, income and average gross margin were calculated. The data were then analyzed using the Monte Carlo techniques with the @Risk 5.5 software, with 1000 iterations of the variables being studied through the model. The kids fed GM and CMR generated negative profitability values when slaughtered at 60 days (US$ −16.4 and US$ −2.17, respectively) and also at 90 days (US$ −30.8 and US$ −0.18, respectively). The risk analysis showed that there is a 98% probability that profitability would be negative when GM is used. In this regard, CM and FC presented low risk when the kids were slaughtered at 60 days (8.5% and 21.2%, respectively) and an even lower risk when animals were slaughtered at 90 days (5.2% and 3.8%, respectively). The kids fed CM and slaughtered at 90 days presented the highest average gross income (US$ 67.88) and also average gross margin (US$ 18.43/animal). For the 60-day rearing regime to be economically viable, the CMR cost should not exceed 11.47% of the animal-selling price. This implies that the replacer cannot cost more than US$ 0.39 and 0.43/kg for the 60- and 90-day feeding regimes, respectively. The sensitivity analysis showed that the variables with the greatest impact on the final model’s results were animal selling price, liquid diet cost, final weight at slaughter and labor. In conclusion, the production of male dairy goat kids can be economically viable when the kids diet consists mainly of either cow milk or fermented colostrum, especially when kids are slaughtered at 90 days of age.