E. A. Ott

EFFECT OF TRACE MINERAL PROTEINATES ON GROWTH AND SKELETAL AND HOOF DEVELOPMENT IN YEARLING HORSES

Abstract Fifteen yearlings, nine Thoroughbreds and six Quarter Horses, were used in a feeding trial to determine whether proteinated trace minerals were utilized advantageously over inorganic trace minerals for growth and development when included in the diet at normal supplementation levels. The animals were assigned randomly within breed and gender subgroups to one of two treatments. Group A received a 12% protein (as fed) concentrate containing a trace mineral premix providing inorganic trace minerals at concentrations appropriate to supplement Coastal Bermuda grass (Cynodon dactylon) hay and provide NRC1 or higher trace mineral intakes. Group B was provided the same concentrations of trace minerals but the Cu, Mn, and Zn were provided via a commercial proteinate. The concentrates were fed to appetite individually, twice daily during a 1.5-hour feeding period. The hay was group-fed in drylot paddocks at 1.0 kg/100 kg BW daily. The animals were housed three or four animals per paddock. Weight and body and hoof growth measurements were taken at the start of the experiment and at 28-day intervals for 112 days. Radiographs of the third metacarpal were made for estimating bone mineral and hoof samples were collected at the start and completion of the experiment. The yearlings gained 0.77±0.03 and 0.79±0.03 kg/d for the inorganic and proteinate groups, respectively. None of the body measurements were affected by diet (P > 0.10) except hip height gain which was higher for the animals receiving the proteinated minerals (7.0 vs 4.7 cm, P = 0.023). Hoof growth was greater for yearlings fed the mineral proteinate than for those fed the inorganic minerals (4.98 vs 4.78 cm, P = 0.016), and colts had greater hoof growth than did fillies (5.00 vs 4.72 cm, P = 0.003). Diet and gender did not affect hoof strength (P > 0.10), but Quarter Horses had greater hoof strength than Thoroughbreds (98.2 vs 88.8 kg, P = 0.046). No differences in bone mineral content or bone mineral deposition were detected (P > 0.10).

Supplementation of broodmares with copper, zinc, iron, manganese, cobalt, iodine, and selenium ☆ ☆☆ ★

In experiment 1, 6 pregnant mares received a concentrate that contained a trace mineral premix that provided 14.3 mg Cu, 40 mg Zn, 28 mg Fe, 28 mg Mn, 0.08 mg Co, 0.16 mg I, and 0.16 mg Se/kg concentrate (group A). Seven mares received the same concentrate plus 502 mg Zn and 127 mg Cu once daily (group B). No differences (P > .05) in foal growth data, or Cu, Zn, and Fe concentrations of mare milk, mare serum, or foal serum were observed. In experiment 2, 6 pregnant mares received the same concentrate as group A (group C), and 8 mares received the same concentrate fortified with 4× the trace mineral premix (group D). Group C mares had higher serum Zn concentration at 1 day (P < 0.01) and 56 days (P < 0.04). Group C mares had higher milk Fe concentration at 28 days (P < .01), and group D mares had higher milk Cu concentration at 56 days (P < .01). Group C foals had higher serum Cu concentration at 14 days (P < .03). The results from this study provide no evidence to indicate that supplementing late gestating and lactating mares with higher dietary trace mineral levels than those recommended currently by NRC has any influence on foal growth and development, or on the Cu, Zn, and Fe concentrations of the mare milk, mare serum, or foal serum.

Influence of electro-acupuncture on pain threshold in horses and its mode of action

Summary Electro-acupuncture (EA) treatments varied in their effect on pain threshold in horses. EA stimulation using local acupuncture points or/and high frequency (80–120 Hz) can be more effective to relieve the experimental pain than the use of distal points and/or low frequency (20 Hz). The acupoints close to the painful areas may need to be stimulated with high frequency EA while the acupoints far from the painful areas may be stimulated with low frequency EA. The release of β-endorphin may be one of the pathways in which electro-acupuncture relieves the experimental pain.

Growth and development of yearling horses fed either alfalfa or coastal bermudagrass: Hay and a concentrate formulated for bermudagrass hay

Two experiments were conducted with yearling horses to determine whether the use of a concentrate designed to be fed with Coastal bermudagrass hay would cause growth differences or skeletal abnormalities when fed with western alfalfa hay. In experiment 1, 13 thoroughbred and quarterhorse yearlings, 332.8 ± 8.5 days, of age were assigned at random within breed and gender subgroups to 1 of 2 diets: (1) alfalfa hay plus a 12.7% CP concentrate and (2) coastal bermudagrass hay plus the same concentrate. The horses were housed in drylot paddocks in groups of 3 or 4 animals and group fed the hay at 1 kg/100 kg BW daily. The concentrates were fed individually to appetite for two 1.5-hour feeding periods daily for 112 days. Orts were weighed back daily. The animals were weighed, measured, and blood samples collected at the start of the experiment and at 28-day intervals for 112 days. Radiographs of the third metacarpal were made on day 0, 56, and 112 for estimation of bone mineral content. In experiment 2, 15 thoroughbred and quarterhorse yearlings, 345.6 ± 8.4 days of age, were used to repeat the experiment. The concentrate fed in this experiment contained 12.4% CP. In experiment 1, the hay protein content was less than anticipated, resulting in a protein intake below NRC1 recommendations. In experiment 2, the hay protein was higher and more typical of NRC1 values. In both experiments, feed intake of the 2 diets was not different (P > .10). Weight gain (P = .0136, P = .0330), heart girth gain (P = .0084, P= .0044), and hip height gain (P = .0165, P = .0137) were higher for the alfalfa fed yearlings for experiment 1 and experiment 2, respectively. Withers height gain (P = .0079) and body length gain (P = .0232) were also greater for the alfalfa fed yearlings on experiment 2. Bone mineral content and bone metabolism indicators were not influenced by diet (P > .10).

Influence of dietary fat and time of hay feeding on growth and development of yearling horses

Summary Seventeen Thoroughbred and Quarter Horse yearlings were used in a 2×2 factorial experiment to determine 1) whether adding fat (5% corn oil) to the concentrate would influence feed intake, growth and development and 2) whether time of hay feeding would influence energy metabolism on the basal and added fat diets. Yearlings were assigned at random, within breed and gender subgroups, to one of four diets: B-I, basal concentrate with Coastal Bermuda grass ( Cynodon dactylon ) hay fed immediately after the concentrate; B-D, basal with hay fed 3.5 hr after the concentrate; F-I, basal + fat with the hay fed immediately; and F-D, basal + fat with the hay fed 3.5 hr after the concentrate. The basal concentrate was formulated to meet or exceed NRC (1989) recommendations when fed with the hay. The basal + fat concentrate was formulated at 9.7% higher digestible energy than the basal concentrate and all of the other nutrients were increased proportionately so if the intake was reduced, the yearlings would still meet nutrient needs. The concentrates were fed individually to appetite for two 1.5-hr feeding periods daily in 1.5×3.0 m slip stalls. Hay was group fed in the paddocks at a rate of 1.0 kg/100 kg BW daily divided into two equal feedings. Animals were housed in four 9.1×34.9-m drylot paddocks with three, four, or five animals in each paddock. The mean age at the start of the experiment was 377±8 days. Weight and body measurements for withers height, heart girth, body length, and hip height were taken at the start of the experiment and at 28-day intervals for 84 days. Radiographs for bone mineral estimates were made at the start and completion of the experiment. During the final 28-day period of the feeding trial, three animals from each experimental group were randomly selected for a 24-h period of blood sampling to evaluate the effects of the diets on blood glucose and insulin. Fat addition to the concentrate reduced the daily concentrate DM (P=0.0187) and total feed DM (P=0.0021) intake. When feed intake was expressed as a function of BW, concentrate and total feed intakes were 1.33 and 2.14 kg/100 kg BW daily and were not influenced by diet (P>0.1). Colts consumed more concentrate DM (P=0.0039) and total feed DM (P=0.0022) than fillies. The yearlings gained an average of 0.60 kg/d for the 84 days. Weight gain, body measurements and bone mineral deposition were not influenced by gender or diet. Mean plasma glucose concentrations were higher (P=0.05) in yearlings consuming the basal concentrate with hay fed immediately than when hay feeding was delayed. When fat was fed, the time of hay feeding had no effect on plasma glucose concentrations (P>0.05). Plasma glucose and insulin were lowest just prior to the morning feeding and peaked two to three hours after both morning and afternoon feedings. Fat supplementation reduced plasma insulin (P=0.001). Results suggest that the addition of 5% corn oil to a yearling concentrate may reduce feed intake but will not reduce growth and development of the animal if other nutrients are supplied at concentrations that provide for the animals daily needs. Delaying hay feeding may be advantageous to growing horses as it may allow the concentrate to move down the tract at a slower rate reducing the glucose peaks.