Ration composition in Wisconsin dairy herds: factors affecting fertility

Abstract Text: The aim of this study was to determine whether composition of total mixed ration (TMR) diets influence reproductive efficiency of dairy farms in Wisconsin. Dairy producers and nutrition consultants from all herds agreed to provide a single snapshot of their complete TMR-ration information used in the post-fresh and high-milk production pens. The nutritional information included all ingredients and nutrient composition of all mixes used, as well as a herd backup that contained accurate production, health and reproductive records with archive files with previous 12 months. The final database included data from 49 free-stall Holstein-dairy herds in WI (DC305^® n=44 and PCDart^® n=5). Size of herds enrolled in the data collection varied from 143 to 2,717 lactating cows (average 719.6±77.2), were milked 2 (n=6) or 3 (n=43) times per day, with average production per cow of 39.0±1.3 Kg/day, and average DMI of 25.1±0.5 Kg/day. Records from PCDart herds were absorbed into DC305 and calculations of reproductive parameters such as conception rate at 1^st AI (CR1AI), overall conception rate (CR), and interval from calving to conception (ICC) were performed with the same standardized command in DC305 to summarize performance records from the previous 12 months. Statistical analyses were performed with the proc MEANS, proc CORR, and proc MIXED of SAS (version 9.3). There was a great variation in diet composition, with CP varying from 16.0 to 18.7%, RDP from 9.1 to 12.3%, NDF from 24.9 to 35.1%, NFC from 31.7 to 46.6%, Starch 20.1 to 30.8%, and Fat from 3.1 to 6.7%. Milk production level was not associated with CR1AI, CR, or ICC (P>0.10). However, greater DMI tended to be associated with lower CR1AI (r=-0.25, P=0.10) and lower CR (r=-0.25, P=0.11). Diet CP and RDP did not seem to affect CR1AI, CR, or ICC (P>0.10). Similarly, Fat content did not influenced fertility parameters (P>0.10). Interestingly, percentage of NDF was positively associated with CR1AI (r=0.36, P=0.01). In addition, greater energy content in the diet measured as NFC, NFC-intake, or Starch were all detrimental to CR1AI (NFC: r=-0.54, P<0.01; NFCi: r=-0.42, P<0.01; Starch: r=-0.37, P=0.03), and CR (NFC: r=-0.51, P<0.01; NFCi: r=-0.44, P<0.01;Starch: r=-0.21, P=0.20). In conclusion, although diets should be balanced to meet milk production requirements, maximizing digestible fiber and lowering highly fermentable energy contents should improve fertility of high producing cows.

Keywords:

Dairy cows

Diet composition

Fertility