Effects on milk production and health of dairy cows by feeding different ratios of concentrate/forage and additional fat before calving

Abstract

The effects on milk yield and health of feeding dairy cows at calving with diets containing different ratios of concentrate/forage (5/95, 30/70, 40/60 or 60/40 on a dry matter basis) at a similar nutritional level was studied in two experiments with a total of 105 multiparous cows. In experiment 2, two groups were fed additional vegetable fat to provide 3 or 6% crude fat in the total diet throughout the experiment. The feed intakes were increased and the ratios of concentrate/forage were changed gradually from 4 weeks before calving to achieve these ratios 3 days before calving. In early lactation the ratios were changed gradually to 35/65, 50/50 or 65/35 by 3 weeks after calving. These diets were fed for 14 weeks after calving. The average daily intake of metabolizable energy was about 160 MJ before calving and between 245 and 260 MJ in early lactation. There was a marked decline in feed intake from about 2 days before calving. The different treatments had no significant effects on the milk yield or composition in the first 4 weeks of lactation, and there were no differences in bodyweight loss, body condition score or fertility between the groups of cows. A diet with a concentrate/forage ratio of 65/35 resulted in higher milk yields and lower milk fat concentrations in lactation weeks 5 to 14 compared with a ratio of 35/65, but the cows suffered significantly more cases of bloat and diarrhoea. The extra dietary fat increased the feed intake between 2 weeks before and 4 weeks after calving, and was associated with a greater loss of bodyweight during lactation weeks 2 to 5. There were wide variations in serum insulin concentrations before calving in the cows fed high ratios of concentrate/forage. There were no significant differences between the groups in the concentrations of serum non‐esterified fatty acids, or plasma glucose, acetoacetate and ß‐hydroxybutyrate.