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Hill, Christopher T.

Animal Science

2006

MS

As farms continue to expand, it has become increasingly important to find an optimal stocking rate that balances between overhead costs per cow and maximal individual cow health and performance. The main objective of this study was to determine the effects of increased stocking rate on short-term cow behavior in order to better identify what stocking rates negatively affect the behavior and performance of lactating dairy cows. High-producing Holstein cattle (n=136) were divided into four pens of 34 cows [11 primiparous (PP), 23 multiparous (MP)]. Each pen was assigned randomly to a stocking rate (100, 1 13, 13 1, or 142%) in a 4 x 4 Latin square design with 7-d periods. The stocking rate was adjusted by altering access equally to headlocks and freestalls. The activity of cows within a pen was recorded continuously with digital video cameras for 48 h at the end of each period. Observations were subsequently recorded at 10-min intervals. The mean percentage of cows feeding over a 24-h period was approximately 20.5%, with no difference between treatments (P > 0.99). There was a decrease from 50.8 to 47.4% in the percentage of cows lying as stocking rate increased (P < 0.01). The percentage of cows standing idle in an alley also increased from 7.8 to 12.7% as stocking rate increased (P < 0.001). This response appears to have occurred partly at the expense of cows standing in a stall, which decreased from 10.8 to 9.2% (P = 0.02). Milk fat percentage decreased from 3.84% to 3.67% as stocking rate increased. A second objective of this study was to determine how parity (PP, MP) and lameness influenced the response of dairy cattle to stocking rate. Six focal animals per pen (2 sound, PP; 2 sound, MP; and 2 lame, MP) were used to evaluate behavioral responses. Sound cows scored <3 and lame cows scored 3 or 4 on a 5-point gait-scoring scale. Behaviors were recorded from direct, visual observations every 10 min using the same timeline described previously. Overall, lying time tended to decrease from 12.3 to 11.4 h/d as stocking rate increased (P = 0.14). Although time feeding was unaffected by stocking rate, with all treatments averaging close to 4.9 h/d, meals per day did increase as stocking rate increased (P = 0.01). Time ruminating tended to decrease from 8.5 to 8.2 h/d (P = 0.19). Ruminating while standing in an alley increased 33 min (P = 0.03), partly at the expense of ruminating whle lying (P = 0.12). Lame cows decreased rumination time (P = 0.09) and had reduced milk yield (P = 0.05) relative to sound cows as stocking rate increased. The advantage in milk yield of MP over PP cows tended to increase from 2.8 to 9.1 kgld as stocking rate increased (P = 0.21). Although overhead and fixed costs may be reduced by housing cattle at higher stocking rates, overall farm profits may decrease because of behavioral and productive changes resulting from very high stocking rates.