Effect of Methionine Hydroxy Analog Supplementation on Dairy Cattle Hoof Growth and Composition

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Abstract
Lactating Holstein cows [50] were assigned randomly to 1 of 2 treatments, control and control plus .apprx. 30 g methionine hydroxy analog, and confined on concrete for 11 mo. The control diet consisted of sorghum silage and concentrate fed as a blended ration. S contents of dry matter were 0.12% and 0.16% for control and methionine hydroxy analog rations. Hoof growth and hardness were measured on front and rear right abaxial claws in the dorsal and lateral regions. Hoof growth rates were measured for 4 periods: summer-fall, fall-winter, winter-spring and spring-summer, seach 70-90 days. Hooves of cows fed methionine hydroxy analog grew faster than those of control cows during spring-summer in all regions. Variations of growth rates of hooves were seasonal and tended to follow variations in daily photoperiod. Wear rates were not affected significantly by treatment. Hooves of cows fed methionine hydroxy analog were softer in the top dorsal region at the end of winter-spring and in the dorsal toe region at the end of spring-summer. All other locations were not affected significantly by treatment. The toe region was harder than the top of the hoof. Cows fed methionine hydroxy analog had less cysteine and proline in hoof than control cows and greater percentages of methionine lysine, tyrosine and glutamic acid. A decrease of disulfide bonding occurred in the hoof tissue of cows fed methionine hydroxy analog. Cows fed methionine hydroxy analog produced more actual milk, milk fat and 4% fat-corrected milk during 180 days than did control cows.
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