|Mertens, David -|
Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2013
Publication Date: July 8, 2013
Citation: Boyd, J.A., Mertens, D.R. 2013. Abrupt changes in forage dry matter of one to three days affect intake and milk yield in lactating dairy cows. Joint Meeting of the ADSA, AMSA, ASAS and PSA. Journal of Animal Science 91(E-Suppl. 2):398. Technical Abstract: Our objective was to determine the effects of one-, two-, and three-day changes in forage dry matter (DM) on lactating cow performance and yield regardless of stage of lactation or parity. Data was compiled from two independent studies to predict overall cow performance. Study A (fall 2009) early lactation animals averaging 65 days in milk (DIM) and 43.3 kg/milk and Study B (fall 2012) late lactation animals averaging 192 DIM and 40.7 kg/milk for a total of 88 Holstein cows (44 primiparous and 44 multiparous) averaging 128.6 DIM and 42.0 kg/d milk. Within each parity, cows were assigned to 1 of 11 blocks based on production and days in lactation, and one cow of each parity-block was randomly assigned to one of two groups for each study. Study design was replicated 2x2 Latin Squares for each set 1-, 2-, or 3-day treatments. Each period consisted of a 3-day pre-treatment, 1- to 3-day treatment, and a 3-day post-treatment phase. Diets were control (Ctrl) with no water added and treatment (Trt) with water added to decrease forage DM by 6 %-units, to mimic rainfall events on a bunker silo and feeding an imprecise ration based on as-fed ratios of ingredients. Ctrl rations were adjusted daily to maintain DM ratios of ingredients during the study. Milk yield was recorded daily, and samples were taken twice daily. Forages, total mixed ration, and refusals were sampled daily and concentrates sampled twice weekly. Chemical composition (dry matter, crude protein, neutral detergent fiber) of samples were determined by near infrared spectroscopy. Data were analyzed using Proc MIXED of SAS with cow within parity-block as a random variable. On day one, dry matter intake (DMI) was reduced 2.3 (P< 0.0001), 1.5 (P< 0.0001), and 0.91 kg (P< 0.0001), for the 1-, 2-, and 3-day treatments, respectively, but DMI recovered during the following 1- to 3-days, even during Trt phases. Although daily milk decreased slightly on day one of each Trt, the decrease was largest on day two: -1.06 (P= 0.003), -1.48 (P= 0.0003) and -0.79 kg (P= 0.03), for the 1-, 2-, and 3-day treatments, respectively. No parity effect was observed, but late lactation cows were not as susceptible to diet DM change as early lactation animals. We concluded that abrupt changes in forage DM cause economically significant reductions in daily milk yield, but the duration of the change does not worsen the losses if adequate ration amounts are provided.