暖季补饲对高寒牧区天然草地放牧泌乳牦牛产乳性能的效应

Effects of warm season supplementary feeding on the milk performance of lactating yaks grazing on natural grassland in an alpine pastoral area

青藏高原高寒草甸草地牧草营养品质虽高,但产量极低,尤其缺乏蛋白饲草且草地呈现不同程度退化,导致泌乳牦牛(Bos grunniens)营养不良,乳产量和品质呈下降趋势。另外,多汁饲料因富含维生素、水分等,通常作为提高奶牛产乳性能的重要饲料种类,但其对泌乳牦牛产乳性能的影响尚不明确。由于青藏高原牧区大多相对干旱,天然草地植物水分含量相对较少,因此预测补给多汁饲料,可能也会提高泌乳期牦牛维生素以及水分的摄取,提高泌乳性能。本研究于2021年暖季(7月-10月)在西藏那曲高寒牧区筛选了体重、年龄、胎次相近的带犊泌乳牦牛24头,随机分4组,在天然草地传统放牧基础上分别设蛋白质饲料[苜蓿(Medicago sativa):1 kg·(d·head)^(-1)]、多汁饲料[萝卜(Raphanus sativus):1 kg·(d·head)^(-1)]、蛋白质加多汁饲料[萝卜和苜蓿各0.5 kg·(d·head)^(-1)]补给和不补给饲料(对照)处理,探讨暖季补给蛋白质和多汁饲料对青藏高原高寒牧区天然草地放牧泌乳期牦牛乳产量和品质(乳脂率、蛋白质率、非脂乳固体率、乳糖率、灰分率、密度、冰点)的影响。结果表明:与对照比较,蛋白质饲料补给显著提高了天然草地放牧泌乳牦牛日产乳量(P<0.05),提高率达22%,延缓了泌乳期牦牛产乳量随时间下降的趋势;多汁饲料补给显著降低了天然草地放牧泌乳牦牛日产乳量,降低率为6%(P<0.05)。与对照比较,单独补给蛋白质饲料或蛋白质加多汁饲料均显著提高了天然草地放牧泌乳牦牛的乳蛋白质率、非脂肪固体率、乳糖率、乳灰分以及乳密度,显著降低了乳冰点,同时补给蛋白质加多汁饲料显著降低了乳脂率。另外,与对照比较,仅补给多汁饲料显著提高了乳脂率、蛋白质率、非脂肪固体率和灰分率,显著降低了乳冰点。但3种补饲处理对泌乳牦牛和犊牛体重均无显著影响(P>0.05)。综上,即使在牧草生长旺盛的暖季,天然草地仍无法满足泌乳牦牛营养需求。且补给蛋白质和多汁饲料均有效提高泌乳牦牛产乳潜能。因此对缓解草畜矛盾,加速当地畜牧业发展以改善当地生活状况具有重要意义。

The alpine meadow grassland of the Qinghai-Tibet Plateau is known for its high nutritional quality,but its yield is extremely low.The lack of protein forage and grasslands show varying degrees of degradation,which have led to malnutrition among lactating yaks,resulting in a decline in both milk yield and quality.While succulent feed has been known to boost milk production in dairy cows due to its vitamin and water content,its effect on lactating yaks is unclear.Given that most pastoral areas in the region are arid with low water content in natural grasses,supplementing succulent feed may increase vitamin and water intake and improve lactation performance.To investigate this hypothesis,24 lactating yaks with similar weight,age,and parity were selected from the Nagqu alpine pastoral area of Tibet during the 2021(July–October)warm season and were randomly divided into four groups.The groups were fed protein[Medicago sativa:1 kg·(d·head)^(-1)],succulent[Raphanus sativus:1 kg·(d·head)^(-1)],protein+succulents[0.5 kg·(d·head)-1 each of alfalfa and radish],and nonsupplemented feed(control group)in addition to their traditional grazing in natural grassland.The study aimed to determine the effects of protein and succulent feed supplementation on the yield and quality of yak milk during lactation while grazing in the alpine pastoral area of the Qinghai-Tibet Plateau.Results showed that compared to the control,protein feed supplementation led to a significant 22%increase in daily milk yield and delayed the decline of milk production during lactation.In contrast,succulent feed supplementation reduced the daily milk yield by 6%.Protein feed alone or combined with succulent feed significantly increased milk protein percentage,non-fat solids percentage,lactose percentage,ash percentage,and density while reducing the milk freezing point.Additionally,only succulent feed significantly improved milk fat percentage,protein percentage,non-fat solids percentage,ash percentage,and reducing freezing point.However,the three supplementary feeding treatments had no significant effect on the body weight of lactating yaks and their calves.In summary,including during the warm season when the pasture is vigorous,natural grassland alone cannot meet the nutritional requirements of lactating yaks in the alpine meadow grassland of the Qinghai-Tibet Plateau.The supplementation of protein and succulent feed can effectively improve the milk production potential of lactating yaks,which is important to alleviate the contradiction between grass and livestock and accelerate local animal husbandry development to enhance living conditions.