Inaccurate prediction of silage intake is a major source of error in ration calculation. Improvement in accuracy depends on the introduction of new routine methods to characterise better the silage fermentation. Electrometric titration has the potential to fill this role as it measures the main fermentation end-products in silage, residual sugar and gives absolute data on buffering characteristics (Offer et al., 1993).

Results are presented for years 1 and 2 of a 3 year study of the use of electrometric titration of silage juice to improve the prediction of silage true DM (TDM) intake (SDMI). Fifty seven silages have been made using a variety of grass and grass-clover mixtures and a wide range of cutting dates (between 25 May and 29 September) and ensilage methods. The following additives were used : none, formic acid (2.5 l/tonne), formic acid (>5 l/tonne), Lactobacillus inoculant, molasses (16 l/tonne), molasses + inoculant. A range of wilting times (0 to 48 hr) was used and in some cases grass was left uncovered in a heap (up to 72 hr) before ensiling.

It is generally acknowledged that lactating dairy cows offered grass silage consume less dry matter (DM) and produce less milk with a lower protein concentration than cows offered fresh pasture. However, there is little evidence to indicate whether these effects are due to the influence of ensiling per se or to differences in herbage composition. The aims of the current experiment were to evaluate the effects of ensiling per se and silage fermentation pattern on forage intake and dairy cow performance.

A perennial ryegrass sward (Lolium perenne cvs Barlenna and Talbot) was divided into 4 areas (A, B, C and D) comprising one area of 6.7 ha (area A) and three areas of 0.7 ha (areas B, C and D). Each area received a total of 361 kg N, 74 kg P2O5 and 144 kg K2O/ha over the season. From 1 June 1993, herbage was harvested once daily from areas B, C and D using a double chop forage harvester and offered to dairy cows housed indoors during weeks 1, 2 and 3 respectively (Treatment G).

The voluntary intake of grass silage (VFI) is influenced by the presence of silage fermentation products. Ammonia-N concentration has been used in prediction equations for silage VFI as an indicator of the negative effects of fermentation products upon VFI but accounts for only a small proportion of the variance. The objective of this experiment was to improve understanding of the factors in silage that limit VFI by relating the time-course of the silage fermentation to the development of intake characteristics.

Second cut perennial ryegrass was precision chop harvested without wilting. The grass was ensiled untreated (C) or treated (I) with 106Lactobacillus plantarum / g grass (Ecosyl, Zeneca Bio-Products) in 200 l containers (10 / treatment). Two containers / treatment were frozen immediately (0) or after 0.2, 1, 2 or 42 days fermentation to give 10 treatments. Juice was extracted using a cider press from silage immediately on thawing, bulked and then re frozen until required for feeding. For feeding, juice was thawed and maintained at 4° until fed.

The dry matter (DM) intake of ruminants offered grass silage is normally less than that of animals offered fresh grass or hay produced from the same sward. End products of fermentation including acids and nitrogenous constituents have been implicated in this depression (Gill, Rook and Thiago, 1988). The aims of the present study were to examine the possible role of amines and juice expressed from silage in silage intake control and to determine if their effect, if any, was due to either oropharyngeal factors or post ingestive mechanisms.

Buffer feeding is a widely used strategy to improve DM intakes from dairy cows at grass. A very wide range of products have been used as buffer feeds resulting in a wide range of responses. Less well understood are which factors are important in explaining these responses. In this experiment the buffer feed characteristic “dry matter content” and the animal factor “stage of lactation” were used as variables in order to gain a better understanding of responses to buffer feeding.

Forty Friesian cows, of which 20 were spring calving and 20 autumn calving were used in a continuous design experiment lasting 5 weeks from 3 May until 7 June 1993. The animals were allocated to four treatments on basis of milk yield, liveweight and stage of lactation. The treatments were grazing only (C), grazing and a buffer feed at 30% DM (B30), 50% DM (B50) and 80% DM (B80) and for each treatment half the cows were spring calving (S) or autumn calving (A). The grazing consisted of a 8 ha field of predominantly perennial ryegrass which was split into 4 equal paddocks which were grazed on a daily rotational basis.

In view of the major changes taking place concerning the buying and selling of milk and milk products this is an appropriate time to consider ways and means to manipulate milk components. The replacement of the Milk Marketing Boards by voluntary co-operatives and the potential changes in the pricing of milk together with changes in consumer demand raises questions over breeding objectives in relation to the emphasis on milk, fat and protein.

The total cow population in the United Kingdom (UK) in 1992 was 4.38 million of which 2.68 million were dairy cows. Prior to 1984 when quotas were introduced cow numbers remained relatively static over a period of 25 years. Since 1984 cow numbers have decreased steadily from 3.3 million to 2.68 million. The major dairy breeds together with their average yields and composition are shown in Table 1.

The aim of this review is to assess to what extent the biological processes of milk protein synthesis and secretion might be manipulated to the benefit of the milk producer, processor and consumer. There is considerable impetus for such an analysis. A completely new ‘agroceutical’ industry is in prospect, utilising novel biotechnology to produce high-value, non-mammary proteins in the milk of transgenic dairy animals (Carver et al., 1993). Nearer to home, the milk processing industry and the consumer may wish to see more modest modification of endogenous milk proteins, making use of naturally occurring genetic variants or, again, using biotechnological approaches (Dalgleish, 1992). Exciting as such possibilites are, I intend to set them to one side and concentrate on the issue that most immediately concerns the dairy farmer: how can he increase his milk protein concentration and, thereby, his profitability. Retrospective analysis reveals some small scope for improvement; between 1985 and 1990, compositional quality data (the basis for milk payment) revealed an increase in protein content from 32.6 to 32.8 g/1, an improvement of 0.6%. Over the same period, milk fat increased by 3.1% and recorded milk yields by 6.4% (all data from UK Dairy Facts and Figures, Federation of United Kingdom Milk Marketing Boards), suggesting that protein content is least amenable to manipulation. Gross production figures of this sort can be misleading, but more controlled experimentation supports the contention. By reducing the forage to concentrate ratio, Rook et al. (1992) increased total protein yield by an impressive 200 g/d. However, only one-quarter of this effect was due to improved protein content, the remainder coming from increased milk yield. Endocrine manipulation of milk production gives a similarly discouraging picture. Growth hormone treatment undoubtedly increases protein yield, but it does so by increasing the volume of milk produced with no detectable effect on protein content (Bauman, 1992). Milk production is also responsive to milking frequency but, once again, the effect is on yield of milk rather than on the protein content of that milk (Hillerton et al., 1990). So, where is the silver lining? Does biotechnology have the answer; can the presence, in mammary cells, of extra copies of correctly expressed milk protein or foreign protein genes markedly increase protein content? In Edinburgh, transgenic sheep are producing milk containing as much as 30 g/1 of human alpha- 1-antitrypsin (Carver et al.. 1993), representing some 50% or the total protein content (Wright et al., 1991). There is good anecdotal reason for believing that total protein content is elevated (one sheep reached 70 g/1), but the definitive statistical analysis is, so far, lacking. We have examined mammary function in transgenic mice expressing the sheep beta-lactoglobulin gene and compared them with non-transgenic controls (Wilde et al.,1992). Expression was good: beta-lactoglobulin accounted for 30% of all the protein present. But, at 95 and 106 mg/ml. respectively, transgenic mouse milk contained no more total protein than that of control mice. The encouraging feature of this work was that mammary tissue from transgenic mice cultured in vitro synthesised 41 % more total protein than did tissue from control mice, a significant difference (P ˂ 0.05).It would appear that the tissue itself had the intrinsic capability for increased protein synthesis, but a block or some sort was imposed in vivo. The next step is to discover the nature of that block, and to do so we must understand the complex series of events leading ultimately to protein secretion into the alveolar lumen.

Several important reasons have contributed to the current interest in manipulating the composition of cows milk, particularly the ratio of milk protein to fat. Current market forces are still influenced with the introduction of production quotas on milk volume which occurred in the mid 80's. This led to a payment scheme based on the sale of milk solids, whilst the more recent introduction of a quota on milk fat sales has provided a major disincentive to overproduce milk fat and specifically milk with a high fat content. Most recently, the pricing structure of milk was changed, with the reward for lactose being removed and replaced by an increased price differential between protein and fat. Thus to the dairy farmer, other than those producing Channel Island milk, increasing the protein content of milk appears the only option with which to increase the ex-farm gate value of the product. At the same time, consumer choice continues to have a major impact on the demand for milk and milk products and the increasing sales of semi-skimmed milk is one consequence of the Nation's concern regarding over-consumption of fats, especially those of animal origin.

An experiment was started in 1984 at Edinburgh and Wye to study responses to divergent selection for lean growth rate (LGA), lean food conversion ratio (LFC) and daily food intake (DFI). This paper measured the selection pressure applied, the responses in the selection criteria and estimated the genetic and phenotypic relationships between the selection criteria with ad-libitum feeding of Large White pigs after four generations of selection.

Selection objectives and criteria. The LGA (LFC) selection objective was to obtain equal correlated responses in growth rate (food conversion ratio) and carcass lean content, measured in phenotypic s.d. The LGA, LFC and DFI selection criteria had phenotypic s.d. of 27, 29 and 250 units and results are presented in s.d. units.

To study responses to divergent selection for lean growth rate (LGA), lean food conversion ratio (LFC) and daily food intake (DFI), an experiment was started in 1984 at Edinburgh and Wye. This paper measured the selection pressure applied, the responses in the selection criteria and estimated the genetic and phenotypic relationships between the selection criteria with ad-libitum feeding of Landrace pigs after four generations of selection.

The LGA (LFC) selection objective was to obtain equal correlated responses in growth rate (food conversion ratio) and carcass lean content, measured in phenotypic s.d. The LGA, LFC and DFI selection criteria had phenotypic s.d. of 32, 29 and 270 units and results are presented in s.d. units.

Boars and gilts were purchased from eight British nucleus herds and boars from national artificial insemination centres in 1982. Homozygous or heterozygous halothane positive pigs were not included in the experiment. The base population consisted of 20 sires and 89 dams. Within each of the three selection groups, there were high and low selection lines with a control line, each consisting of 10 boars and 20 gilts, with a generation interval of one year. There were two control lines, one for LGA and one for LFC and DFI, as selection groups were arrowed continuously. The total number of pigs tested per line and average inbreeding coefficient at generation 4, within selection group are given below.

This study determined the responses in performance test traits after four generations of divergent selection for lean growth rate (LGA), lean food conversion ratio (LFC) and daily food intake (DFI) in Large White and Landrace pigs.

Within each of the three selection groups, there were high and low selection lines with a control line, each consisting of 10 sires and 20 dams, with an average of 3 boars and 3 gilts tested per litter. A total of 3537 Large White and 2642 Landrace pigs were performance tested in Edinburgh and Wye, respectively. The performance test was over a fixed weight range of 30±3 kg to 85±5 kg. All pigs were individually penned, with ad-libitum feeding of a high energy (13.8 MJ DE/kg DM) and high protein (210 g/kg DM crude protein) pelleted ration.

Correlated responses in performance test traits to selection on LGA, LFC and DFI were estimated from the mean within-generation selection line breeding values for each trait, determined with the additive genetic and common environmental (co)variances for performance test traits, which were estimated using multivariate derivative-free residual maximum likelihood analyses.

Divergent selection lines for lean growth on a restricted feeding regime, in Large White and Landrace pigs, were established to complement the lean growth selection lines on ad-libitum feeding. This study estimated the direct and correlated responses after four generations of selection and the corresponding genetic and phenotypic parameters.

The selection objective for lean growth on restricted or scale (LGS) feeding was to obtain equal correlated responses in growth rate and carcass lean content, measured in phenotypic s.d. The selection criterion included measurements of growth rate and ultrasonic backfat depth.

Large White (LW) and Landrace (LR) boars and gilts were purchased from eight British nucleus herds and boars from national artificial insemination centres in 1982. Homozygous or heterozygous halothane positive pigs were not included in the experiment. The base populations consisted of 31 LW and 19 LR sires and 57 LW and 67 LR dams. Within each population, there were high and low selection lines with a control line, each consisting of 10 boars and 20 gilts, with a generation interval of 13.5 and 12 months for LW and LR pigs. Animals were performance tested in individual pens from 30±3 kg for a period of 84 days and fed a high energy (13.8 MJ DE/kg DM) and high protein (210 g/kg DM crude protein) pelleted ration. Daily food intake was equal to 0.75 g/g of the daily food intake for ad-libitum fed pigs and the total food intake was 134 kg for LW pigs and 150 kg for LR pigs. On average, 3 boars and 3 gilts were tested per litter. The total number of pigs tested per line and average inbreeding coefficients at generation four, by population are given below.

This paper examined a genotype with feeding regime interaction by performance testing pigs, selected for lean growth on ad-libitum or restricted feeding, on both the normal and the alternative feeding regime.

Large White (LW) and Landrace (LR) pigs from divergent selection lines were for four generations for lean growth either on an ad-libitum (LGA) or a restricted (LGS) feeding regime. In each selection group, there were high, low and control lines, which consisted of 10 sires and 20 dams. On average, 3 boars and 3 gilts were tested per litter, with one boar and one gilt per litter tested on the alternative feeding regime. On ad-libitum feeding, there were 181 LGA and 94 LGS LW pigs and 162 LGA and 67 LGS LR pigs. On restricted feeding, 92 LGA and 212 LGS LW and 53 LGA and 135 LGS LR pigs were tested.

Performance test. The performance test was over a fixed weight range of 30±3 kg to 85±5 kg for ad-libitum fed pigs and for a fixed time of 84 days for restricted fed pigs. Restricted feeding was equal to 0.75 g/g of daily food intake of ad-libitum fed pigs. All pigs were individually penned and fed a high energy (13.8 MJ DE/kg DM) and high protein (210 g/kg DM crude protein) pelleted ration.

This study determined the correlated responses in reproductive performance after five generations of divergent selection for components of efficient lean growth rate in Large White pigs.

Data were collected from five generations of pigs divergently selected for daily food intake (DFI), lean food conversion (LFC), lean growth rate on ad-libitum feeding (LGA) and lean growth rate on restricted or scale feeding (LGS). In each selection group, there were high, low and control lines, each consisting of 10 boars and 20 gilts. Animals were mated at around 9.5 months of age. Pregnant gilts were fed 2.5 kg daily and farrowed sows up to 3.5 kg twice daily of a 160 g/kg DM crude protein and 132 MJ/kg DM digestible energy ration. Animals were farrowed at 414 (s.d. 19.7) days of age, on average. No cross fostering was practised. Piglets were offered creep feed containing 235 g/kg DM crude protein and 160 MJ/kg DM digestible energy from 14 days and were weaned at an average of 35 (s.d. 3) days. Litter traits were measured on 1220 selected Large White gilts, with 13030 piglet birth weights and 9951 weaning weights.

This study determined the correlated responses in carcass composition after four generations of divergent selection for components of efficient lean growth rate in Large White (LW) and Landrace (LR) pigs.

An important aspect of animal improvement is the correct identification of those individuals with superior genetic merit. Testing to accurately assess merit, however, can be a costly component of improvement. In the Group Nucleus there is a substantial number of potential offspring to be tested even within a system where the farrowing and testing is practised continuously throughout the year. In order, therefore, to reduce costs it could be beneficial to accurately predict genetic worth prior to test on either mean parental breeding value or a trait expressed early before test.

A Group Nucleus population was modelled by stochastic simulation with selection at two stages The model for the trait(s) selected comprised animal, common environment, herd-year-season and error components. A multivariate animal model BLUP routine was used for the evaluation.

Available technology allows pig breeding companies to automate feed intake recording during performance test. This provides data on ‘average daily feed intake’ as recorded with more traditional manual systems. It also results in feed intake curves, i.e. the relationship between ‘days on test’ and ‘daily feed intake’. This information can be used in different ways. The feed intake curve may be described using sophisticated linear or non-linear models; these may describe the feed intake curve accurately, but model parameters cannot be used easily in genetic/economic evaluation in the context of a breeding programme. A simple method to describe feed intake curves is used in this paper, allowing for easy interpretation of the results. The objective is to study the impact of existing selection procedures on the feed intake curve and the utilisation of variation in its shape in pig breeding.

Performance test data of 1331 boars of a Large White based line, collected from November 1990 to March 1993 were analysed. Boars are tested over a 12 week period, starting at approximately 30 kg. Feed intake data are recorded with the Hunday FIRE system.

A group breeding scheme was set up in 1976 by 10 Welsh Mountain breeders. The objective of the scheme was to improve lamb growth rate, mature size, mothering ability and litter size by selection in a nucleus flock. The original design of the scheme involved two control flocks. The Genetic Control flock was set up from the original base population and was used to monitor environmental changes in the nucleus flock. A Commercial Control flock comprised of a random selection of ewes mated to rams, which were purchased annually and represented the average animal available in the breed. An analysis of genetic progress in lamb growth in the first 9 years of the scheme was reported by Guy et al (1986). This paper presents genetic parameters and genetic trends for three traits recorded between 1977 and 1992.

Multiple ovulation and embryo transfer (MOET) is being used by the Scottish Agricultural College, Aberdeen to accelerate genetic change in the Simmental breed. The selection goal of the project is improving the efficiency of lean meat production. The factors in this goal are saleable meat (predicted from liveweight, fat depth and muscling score), food intake and calving difficulty (predicted from gestation length and birth weight). Success of the project depends on the generation of sufficient grade 1 embryos from selected donor heifers in a 12 week period following a performance test. Performance testing to assess beef characteristics can produce precociously fat heifers which may be detrimental to embryo production. The onset of puberty in heifers is also highly variable and influenced by many factors including body weight and nutrition. The objective of this study was to examine the relationship of superovulatory response to performance on test and age at the onset of puberty.

The drive for improved carcass quality has encouraged greater use of continental cross suckler dams (MLC,1993), producing three-quarterbred continental progeny. Little information is available on the performance of these types of suckler cow under hill conditions in the UK, but significant genotype by environment interractions have been measured elsewhere (Morris et al, 1993). As a finished animal, the Piemontese cross has shown significant advantages in killing-out proportion and yield of saleable meat (Davies et al, 1992), and some improvements in eating quality (Fisher et al, 1992).

The objective of this experiment was to assess the output and reproductive performance of Piemontese cross Holstein/Friesian (PxH/F) and Simmental cross Holstein/Friesian (SxH/F) heifers in an autumn calving suckler herd.