This study investigated the potential for applying an automatic milking system (AMS) to the management of high-yielding cows offered a total mixed ration (TMR). The null hypothesis was that it is desirable to maintain even in AMS, the TMR feeding management practice recommended for high-yielding cows and therefore it can be attained by ‘reducing the concentrate allocation in the robot without reducing the number of milkings’. Two feeding regimes were used: the ‘candy concept’, with only 1·2 kg of food concentrate – the minimum to attract the cow – provided at each visit to the milking robot; and the provision of a maximum of 7 kg of food concentrate per day. Approximately 100 cows were subjected to one or other of these two treatments. Although the cows in the first treatment consumed approximately 3·5 kg of concentrate per day and those in the second treatment approximately 5 kg per day, no significant differences were observed in the numbers of voluntary milkings.

In pigs the quantification of breakdown and synthesis by powers of body protein led to the estimation of turn-over related protein retention efficiency by the equation kP = {1 + [1 − (P/α) (2/9)Q]−1/6}−1, with α the limit value of whole body protein (P) maturity, so that 0 ≤(P/α)≤1. The factor 2/9 is derived from diffusion attributes indicated by cell and nucleus geometries α and Q represents a scaled transformation of intake, 0 ≤ Q ≤ 1, such that a value of Q = 1 may represent ad libitum intake and Q = 0 the intake at the maintenance requirement. Published observations on finishing steers provide estimates of whole body protein synthesis and breakdown at pre-determined levels of intake in confirmation of the theoretical (2/9)Q power associated with (P/α) in kP. Further confirmation of the (2/9)Q power in cattle follows from satisfactory agreement between an estimate of conventional multiple regression retention efficiency and the turn-over related retention efficiency calculated at the given level of intake, for the mid point of the body mass interval covered by the regression estimate. In addition, a simulation experiment on cattle from the literature gives power estimates of protein breakdown and synthesis in general agreement with those accepted for pigs. Examples on both fine and coarse diets are employed to suggest a general rule for prediction on diets causing submaximal efficiency due to suboptimal intakes.

In sheep, evidence derived from estimates of conventional multiple regression efficiencies suggests that the rule (a-b) = (2/9) Q for the calculation of kP should be reserved for the description of compensatory growth. Protein retention efficiency for ordinary growth should be described by an adaptation of the rule derived for suboptimal intakes.

A deletion approach was undertaken to identify which amino acids (AA) most limited the growth of mixed ruminal microorganisms on xylan. Ruminal fluid was withdrawn from sheep receiving a mixed grass hay/concentrate diet and incubated for 24 h with oat spelts xylan in the presence or absence of a mixture of 20 AA or the same mixture with a single AA deleted. Gas and volatile fatty acid production were increased by the AA mixture in comparison with incubations in which ammonia was the only added nitrogen (N) source, and the deletion of each of the aromatic AA, tyrosine, phenylalanine and tryptophan, as well as leucine and methionine, led to decreases (P < 0·05) in fermentation rate. The addition of aromatic AA as a mixture to ammonia-only fermentations increased (P < 0·05) the fermentation rate but failed to replicate the benefits of the complete mixture of AA. Although the addition of all 20 AA increased (P < 0·05) the microbial yield by up to 0·56, no single AA deletion had a significant (P > 0·05) influence on microbial yield, and the aromatic AA mixture also did not increase the microbial yield on xylan over the yield with ammonia as sole N source. It was concluded that aromatic AA may be first-limiting for xylan fermentation, but they cannot replace the benefits of a complete mixture of 20 AA in stimulating xylan fermentation by ruminal micro-organisms.

Duodenally and ruminally fistulated steers were offered grass silage and one of three concentrates at a ratio of 60: 40 (forage: concentrate on a dry-matter basis) : F0, F1 or F4 at 14 g/kg live weight. The concentrates were designed to be iso-lipid and to provide the same amount of sunflower oil but increasing amounts of fish oil : 0, 1 and 4 g per 100 g, respectively. Ruminal characteristics were measured along with fatty acid intakes and duodenal flows to determine the effect of fish oil on : ruminal pH, ammonia-N concentration, volatile fatty acid (VFA) concentration and polyunsaturated fatty acid (PUFA) metabolism. Fish oil had no significant effect on ruminal pH, ammonia-N concentration or the molar proportions of the major VFA, although total VFA concentration was significantly reduced at the highest level of fish oil inclusion. Fish oil significantly increased the flow of long chain PUFA, total conjugated linoleic acid and vaccenic acid to the duodenum and decreased the flow of stearic acid. Biohydrogenation, as determined by the net loss of fatty acid between the mouth and duodenum, of oleic and linolenic acid was not affected by fish oil inclusion and averaged 0·64 and 0·92, respectively. There was a small increase in the biohydrogenation of linoleic acid with increasing fish oil from 0·89 to 0·92 (P < 0·01) on F0 and F4, respectively. Biohydrogenation of the long chain PUFA C20 : 5(n-3) and C22 : 6(n-3) increased from 0·49 and 0·74 to 0·79 and 0·86 (P < 0·01), respectively when fish oil in the concentrate increased from 1 to 4 g per 100 g. The net effect of fish oil on lipid metabolism appears to inhibit the transition of vaccenic acid to stearic acid in the rumen resulting in a build up of this intermediate in the biohydrogenation pathway of C18 PUFA.

This study was carried out to determine ruminal dry matter (DM) and crude protein (CP) degradation characteristics of untreated, 2-, 4- and 6-min microwave-treated soya-bean meal (SBM) by using nylon bags and sodium dodecyl sulphatepolyacrylamide gel electrophoresis (SDS-PAGE) techniques. Nylon bags of untreated or treated SBM were suspended into the rumen of three Holstein steers from 0 to 48 h, and data were fitted to non-linear degradation characteristics to calculate effective rumen degradation (ERD). There were significant differences (P < 0·05) for DM and CP degradation parameters between untreated and microwave-treated SBM. Microwave treatments decreased the water-soluble fraction and increased the potentially degradable fraction of CP. The degradation rate of the latter fraction decreased with these treatments. As a consequence, microwave treatments decreased (P < 0·05) ERD of CP. From densitometric scanning, SBM proteins were seen to be composed of two major components; β-conglycinin and glycinin, accounting for proportionately 0·30 and 0·40 of buffer-soluble SBM proteins, respectively. Electrophoretic analysis of untreated, 2-, 4- and 6-min microwave-treated SBM protein residues revealed that two of the subunits of β-conglycinin (α -and α) were degraded completely after 2, 4, 24 and 48 h, respectively, whereas the α subunit of this protein was more resistant to degradation. In untreated SBM, the two subunits of glycinin (acidic and basic polypeptides) were degraded in the middle of the incubation period, but in microwave-treated SBM were not degraded until 48 h of incubation. In vitro digestibility of ruminally undegraded CP of untreated and treated SBM increased (P < 0·05) with increases in rumen incubation time from 8 to 24 h. In conclusion, SBM proteins appeared to be effectively protected from ruminal degradation by a 4-min microwave treatment. SDS-PAGE results indicated that ruminally undegraded protein from untreated SBM was mainly composed of the basic subunit of glycinin, whereas that from microwave-treated SBM was composed of β-conglycinin and both basic and acidic subunits of glycinin.

To determine the effect of age at castration on physiological and immunological stress indices, 60 Holstein-Friesian bull calves were sourced so that they were in one of five age groups for Burdizzo castration on day 0 (16 July 2002; no. = 10 per treatment) : 1·5, 2·5, 3·5, 4·5, and 5·5 months of age (mean body weight ± s.e. = 63 ± 2·5, 89 ± 3·7, 104 ± 3·7, 142 ± 3·6, 169 ± 8·1 kg, respectively), or were sham castrated at 5·5 months of age (171 ± 2·9 kg body weight) to serve as intact controls specific to this age group. Blood samples were collected at 15- to 30-min intervals from 2 h before until 8 h after treatment, with further samples collected at 10 and 12 h on day 0, and on days 1, 2 and 3, and weekly from days 7 to 35 after treatment. Following castration, peak plasma cortisol responses were significantly greater in 5·5-month-old castrates than intact calves, and all calves castrated at a younger age had reduced peak responses, with the greatest reduction in 1·5-month-old castrates. Overall, the integrated cortisol responses for the first 3 h after castration were three-fold greater in 5·5-month-old castrates than intact calves. While the integrated cortisol responses were reduced by proportionately 0·46 and 0·35 in 1·5- and 4·5-month-old castrates, the lower responses observed in 2·5- and 3·5- month-old castrates were not significantly different from the 5·5-month-old castrates. The integrated cortisol responses for the next 9 h after castration were not different among treatment groups. On day 3 after castration, peak plasma haptoglobin and fibrinogen concentrations were significantly greater in 5·5-month-old castrates than intact calves, but the concentrations were markedly reduced in calves castrated at 1·5 and 2·5 months than when castrated at 5·5 months of age. On day 1, phytohaemagglutinin-induced in vitro interferon-γ production was suppressed in 5·5-month-old castrates compared with intact calves. Scrotal circumferences increased in all castrates on day 1 and 7 and were greater in 5·5- month-old castrates than intact calves, but the swelling was reduced in the 1·5- compared with 5·5-month-old castrates. The temperature differences between the core body and scrotal skin were greater on day 2 and 3 in the 1·5-month-old than all other castrates. There was no effect of castration on the overall 42-day growth rates of calves. In conclusion, the physiological stress and inflammation caused by Burdizzo castration, indicated by increased plasma cortisol, acute-phase proteins, scrotal swelling, and depressed temperature differences between the core body and scrotal skin were reduced by castrating calves at 1·5 months rather than at 5·5 months of age.