The objective of the present study was to evaluate the effects of betaine supplementation on rumen fermentation, lactation performance and plasma characteristics in dairy cows. Twenty multiparous Holstein dairy cows (597±11·8 kg body weight (BW), 88±4·5 days in milk (DIM) and average daily milk production of 26·3±0·5 kg/cow) were used in a replicated 4×4 Latin square experiment. The treatments were: control (without betaine), low-betaine (LB), medium-betaine (MB) and high-betaine (HB) with 0, 50, 100 and 150 g supplemental anhydrous betaine/cow/day, respectively. Betaine was hand-mixed into the top one-third of the daily ration at feeding. Experimental periods were 30 days with 15 days of adaptation and 15 days of sampling. Dry matter (DM) intake was not affected with increasing the betaine supplementation. There were linear increases in milk yield and fat-corrected milk yield (corrected to 40 g fat/kg) and a linear and quadratic increase in milk fat concentration with increasing the betaine supplementation, whereas the proportion and yield of milk protein and lactose, and feed efficiency, were not affected. Ruminal pH and ammonia N linearly decreased, whereas total volatile fatty acid (VFA) concentration linearly and quadratically increased with increasing the betaine supplementation. The ratio of acetate to propionate (A:P) linearly increased from 3·06 to 3·53 as betaine supplementation increased. Digestibility of DM linearly increased, whereas digestibilities of organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF) in the total tract were quadratically increased with increasing the betaine supplementation. Plasma concentrations of non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHBA) were lower for betaine supplementation than for control, and were linearly decreased by betaine supplementation. The results indicate that supplementation of mid-lactation dairy cow diets with betaine increased milk yield through increased feed digestion. Betaine supplementation may benefit lactation performance when methionine supply is limiting.

This group, which represents the reformed Operational Research (OR) Society's Agriculture and Related Industries group (http://www.orsoc.org.uk), promotes the use of OR (or the application of the scientific method) in solving management and governance problems within this sector. The theme of this meeting was to look at models concerned with making better decisions for the management or governance of the agricultural and natural resource industries. This first one day meeting was at Reading University, Berkshire, UK on the 2 April when the following papers were read.

Relationships between sward height and short-term ingestive behaviour of cattle were examined for two tropical stoloniferous grasses with contrasting growth forms: centipede grass (Eremochloa ophiuroides (Munro) Hack.; (CG); strongly prostrate) and bahia grass (Paspalum notatum Flügge; (BG); more erect). Turves (500×500 mm) were extracted from field monoculture swards of each grass after the varying duration of re-growth, and presented to animals for a short period (10 bites) to measure bite dimensions (area, depth and volume), bite mass, time per bite and intake rate. In the same re-growth period, CG was always shorter and denser than BG. Bite dimensions, the bite mass and the intake rate of animals increased at a declining rate as the sward height increased for both grasses, showing a tendency for a steeper initial increase, an earlier plateau and a lower maximum in CG than in BG. Due to the difference in the shape of the intake rate response, animals on BG were estimated to require a longer grazing time than those on CG to attain the same daily herbage intake, when the sward is shorter than about 200 mm. The sward height below which the daily intake of animals may be restricted was lower for CG (61–70 mm) than for BG (71–92 mm). The results indicate an advantage of strongly prostrated, highly dense grasses (e.g. CG) over more erect, less dense grasses (e.g. BG) when grazed at a relatively low height (<200 mm). In relation to increasing bite mass, the time per bite pooled over CG and BG was constant until the bite mass reached a critical value (0·55 g dry matter (DM)) and thereafter increased linearly with the bite mass, confirming that cattle are able to perform compound jaw movements that gather herbage into the mouth (manipulative jaw movement) and chew herbage already in the mouth (chewing jaw movement) within one cycle of opening and closing of the jaws.