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Does concentrate allocation pattern affect the milk production of autumn calving cows at high and low feeding levels?
The objective of this experiment was to examine the effects of concentrate allocation pattern at two concentrate feeding levels, on feed intake, milk yield and milk composition of autumn calving cows offered a base forage mix of grass silage and maize silage. The study used a randomised block design with a 2×2 factorial arrangement of treatments and was carried out over an 11 week period in 2011 and 2012. The treatment factors were flat (F) or variable (V) concentrate allocation pattern, at high (7.0 kg DM/cow per day (Hi)) or low (4.0 kg DM/cow per day (Lo)) concentrate feeding level. Cows (n=108) were blocked in groups of four based on calving date, parity and the milk yield, body weight and BCS of weeks three and four of lactation. Within each treatment cows were sub-grouped as high, medium and low milk yield based on pre-experimental milk data. The HiV cows received 8.7, 7.0 or 5.3 kg DM of concentrate/cow per day in the high, medium and low subgroups respectively. The LoV cows received 5.3, 4.0 or 2.7 kg DM of concentrate/cow per day in the high, medium and low subgroups respectively. Flat rate treatments received 7.0 kg DM (HiF) or 4.0 kg DM (LoF) of concentrate/cow per day. Concentrate was allocated in the base diet; 2 kg and 2.4 kg DM for Hi and Lo, respectively, and the remaining amount was allocated in the parlor. All cows remained on a fixed level of concentrate for the duration of the experiment. Data were analyzed using a mixed model procedure in SAS v9.3 which included a repeated measure for week of experiment. Cows on the Hi treatment had 2.9 kg higher total DM intake (P<0.001), and 0.5 kg reduction in base feed DM intake (P<0.05), compared to animals on the Lo treatment, which had a total DM intake of 15.8 kg DM and a base feed intake of 14.2 kg DM. Each additional 1 kg concentrate DM intake above the Lo treatment, resulted in a 0.43 kg increase in milk yield (P<0.001) which was 25.1 kg and 23.8 kg on Hi and Lo, respectively. There was no allocation pattern by feeding level interactions for milk yield, milk composition or dry matter intake. Allocating concentrate at a variable rate had no effect on milk yield or DM intake, when compared to allocating concentrate at a flat rate.
Keywords: Feed-to-yield: Flat-rate: Holstein Friesian