Milk production, dry matter intake and body condition score evaluated in cross-bred commercial cows supplemented with OmniGen-AF™ during and following heat stress

Abstract Text: Dairy cows in the US are affected by heat stress for a significant part of the year, resulting in reduced dry matter intakes (DMI), milk yields (MY) and profits. In 2012, a 15 week study (July 9–October 16) was conducted in Texas to evaluate MY, DMI and body condition score (BCS) in multiparous cross-bred (H x J) cows fed OmniGen-AF (OG) and subjected to heat stress. Two-hundred sixty-six early to mid-lactation cows were enrolled based on parity, days in milk (DIM) and current MY and assigned to either the basal diet without OG (Controls, n=123h) or basal diet plus OG (n=143h). OG was fed at 56 g/h/d. The average parity and DIM for Controls and OG cows were 3.25; 134 d and 3.25; 130 d, respectively. Diets were fed as a TMR and orts collected daily to calculate DMI. Cows were housed in free-stalls with heat abatement and milked 3 times/d. BCS was assessed at weeks 4, 10 and 15. Daily temperature (°C) was measured and weekly highs and lows calculated. Individual milk weights were retrieved from Westfalia Surge Dairy Plan System. Only cows with weeks 1 and 15 milk weights and at least 12 total weekly weights were used. Data were analyzed using PROC GLM (SAS) and significance tested to P<0.05. High and low average weekly temperatures (°C) for weeks 1-7 and 8-15 were; 35.9; 21.8 and 25.9; 12.8, respectively. DMI did not differ between Controls or OG cows during weeks 1-7 (26kg/d) or weeks 8-15 (29.7kg/d). No differences in BCS were detected between Controls or OG cows at week 4 (3.01), 10 (2.94) or 15 (2.75). Weeks 1-7 MY’s were not different between Controls (36.3kg/d) and OG cows (37.1kg/d), however differed (P<0.004) in weeks 8-15 (33.2kg/d; 35.5kg/d, respectively). OG cows MY averaged 1.3kg/d more (P<0.048) than Controls from weeks 1-15. MY’s of Controls (n=43h) and OG (n=51h) cows that were 120 DIM or less at the start were not different in weeks 1-7 (40.4kg/d; 42kg/d), however differed in weeks 8-15 (36.5kg/d; 39.4kg/d, P<0.005). Controls (n=80h) and OG (n=79h) cows 121 DIM or greater at the start were not different in MY, until week 15 (28.8kg/d; 31.2kg/d, P<0.032). All cows showed the typical MY and DMI response to heat stress, however cows fed OmniGen-AF were observed to recover sooner as measured by milk production.  

Keywords: Heat stress, Lactation, OmniGen-AF