Embedded microcomputer-based force plate system validation when evaluating lameness severity differentiation under an induced synovitis model in lactating dairy cattle.

Bovine lameness has relatively large negative economic and welfare implications on the U.S. dairy industry. Due to the ramifications, early lameness detection will aid in assisting dairy producers to mitigate downstream effects through early treatment. The objective of this study was to determine the minimum standing time required among 2-, 3-, 4-, 5-, and 10 min time intervals to obtain an accurate weight distribution estimate for each leg when attempting to detect lameness. An embedded microcomputer-based force plate system was developed to measure vertical forces from individual cow limb weight distribution to detect bovine lameness when utilizing an induced synovitis lameness model. The force plate has four quadrants, with each load cell quadrant measuring the force placed on it from a single limb. The force plate recorded weight (kg) every second from each load cell quadrant, after which, a 60 s moving average for weight distribution was calculated. A sequential study design was employed to evaluate non-lame and induced lameness to ensure time requirements were consistent. Prior to induction, the force plate system was used to measure weight distribution every second for 15 min. After lameness induction, additional 15 min increments were recorded every 24 h for seven days. Lameness was induced by injecting the left hind distal interphalangeal joint in three cows with amphotericin B, 12 h prior to the start of the study. Data were analyzed using a linear mixed effect that included the fixed effects of day relative to lameness induction, time period, foot and injected foot. Cow within replicate was included as a random effect. Cumulative minutes were assessed up to 15 min by comparing the least square rolling 60 s cumulative means expressed as a percentage of each animal's BW percentage placed on each leg for 2-, 3-, 4-, 5-, and 10 min intervals. Results indicate that the minimum time needed for accurate lameness detection in cows was 2 min.

Genetic correlation and genome-wide association study (GWAS) of the length of productive life, days open, and 305-days milk yield in crossbred Holstein dairy cattle.

In this study, we estimated the genetic parameters and identified the putative quantitative trait loci (QTL) associated with the length of productive life (LPL), days open (DO), and 305-day milk yield for the first lactation (FM305) of crossbred Holstein dairy cattle. Data comprising 4,739 records collected between 1986 and 2004 were used to estimate the variance-covariance components using the multiple-trait animal linear mixed models based on the average information restricted maximum likelihood (AI-REML) algorithm. Thirty-six animals were genotyped using the Illumina BovineSNP50 Bead Chip [>50,000 single nucleotide polymorphisms (SNPs)] to identify the putative QTL in a genome-wide association study. The heritability of the production trait FM305 was 0.25 and that of the functional traits, LPL and DO, was low (0.10 and 0.06, respectively). The genetic correlation estimates demonstrated favorable negative correlations between LPL and DO (-0.02). However, we observed a favorable positive correlation between FM305 and LPL (0.43) and an unfavorable positive correlation between FM305 and DO (0.1). The GWAS results indicated that 23 QTLs on bovine chromosomes 1, 4, 5, 8, 15, 26, and X were associated with the traits of interest, and the putative QTL regions were identified within seven genes (SYT1, DOCK11, KLHL13, IL13RA1, PRKG1, GNA14, and LRRC4C). In conclusion, the heritability estimates of the LPL and DO were low. Therefore, the approach of multiple-trait selection indexes should be applied, and the QTL identified here should be considered for use in marker-assisted selection in the future.