The effects of matua bromegrass hay on gestating and lactating mares and their foals

Date

2001-08

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Publisher

Texas Tech University

Abstract

Matua bromegrass (Bromus willdenowii Kunth) has been shown to be an acceptable forage for yearling and mature gelding horses; however, its value for mares during gestation and lactation is unknown. Hence, two experiments were conducted to evaluate the effects of Matua as a forage source for mares in early and late gestation, and for lactating mares and their foals. In Experiment 1, the effects of Matua on intake, reproduction, milk crude protein content, and foal growth were compared with alfalfa {Medicago sativa L). Eight 2-yr-old and four aged (7- to 12-yr-old) gravid Quarter Horse mares (BW = 553 kg ± 36), scheduled to foal between March and May were used. There were variable days on trial prepartum (mean 59 d ± 8.07); however, all mares and foals were on trial 70 d postpartum. Mares were blocked by age, expected date of foaling, and BW, and were assigned randomly to either Matua or alfalfa treatments (six mares per treatment). Crude protein (DM basis) averaged 11.45 and 15.38% for Matua and alfalfa, respectively. No adverse effects were observed in either broodmares or foals as a result of feeding Matua hay. Forage DM intake, by prepartum mares averaged 6.8 and 7.0 kg/d (SE = 0.40) for Matua and alfalfa, respectively, whereas postpartum intake was 7.9 and 8.3 kg/d, (SE = 0.70) respectively, for the two hays. Mean gestational length of mares fed Matua (342.4 d ± 3.05) did not differ (P = 0.67) from those fed alfalfa (340.7 d ± 3.05). Live foal births were 100% for each treatment. Mean foal birth weights (42.4 kg vs 46.6 kg SE= 4.20) did not differ (P = 0.50) between the Matua and alfalfa treatments. Likewise, average daily gain by foals (1.41 kg vs 1.23 kg SE= 0.06) did not differ (P = 0.36) between treatments. Mean day of first postpartum ovulation did not differ (P = 0.33) between mares fed the two hays. There was no difference (P = 0.18) in cycles per conception for mares fed Matua versus alfalfa, and pregnancy rate at d 70 was 100% for both groups. Differences in percentage of protein in milk between treatments varied by day of sampling. On d 1, milk from mares fed alfalfa was lower in protein (P < 0.03) than milk from mares fed Matua, but throughout the remainder of the trial, milk protein did not differ (P = 0.58) between the two hay treatments. Milk protein percent decreased (P = 0.0001) over time.

In Experiment 2, voluntary intake and rate of passage of Matua, alfalfa and, timothy {Phleum pratense L.) hays were determined in 2-yr-old pregnant mares. Forages were fed as 100% of the diet. Voluntary intake of alfalfa was higher (P < 0.05) than Matua expressed as kg/d (13.7 vs 11.5), percentage of body weight (3.0 versus 2.6) and as g/kg of BW °" (138 versus 118). Timothy was lower (P < 0.05) in intake than either alfalfa or Matua. This may be because the timothy used in this study was of very poor quality. The rate of passage of the three forages was measured by passage of chromium-mordanted fiber. Lambda 2 values and mean retention time did not differ between Matua and alfalfa; however, the means of Matua and alfalfa were different than for timothy (P < 0.01) . Our results indicate that Matua is an acceptable hay for mares during early and late gestation and for mares early lactation and for their young foals..

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