Astessiano Ana Laura, Meikle Ana, Fajardo Maite, Gil Jorge, Mattiauda Diego Antonio, Chilibroste Pablo, Carriquiry Mariana
Department of Animal Production and Pastures, School of Agronomy, Universidad de la República (UdelaR), Av. E. Garzón 780, C.P. 12900, Montevideo, Uruguay.
Laboratory of Nuclear Techniques, School of Veterinary Medicine, Universidad de la República (UdelaR), C/Lasplaces 1550, C.P. 11600, Montevideo, Uruguay.
Acta Vet Scand. 2015 Oct 16;57:70. doi: 10.1186/s13028-015-0163-6.
In dairy mixed production systems, maximizing pasture intake and total mixed ration (TMR) supplementation are management tools used to increase dry matter and energy intake in early lactation. The objective was to evaluate metabolic and endocrine profiles and hepatic gene expression of Holstein cows fed either TMR ad libitum (without grazing) or diets combining TMR (50 % ad libitum DM intake) and pasture with different grazing strategies (6 h in one grazing session or 9 h in two grazing sessions) in early lactation. Pluriparous cows were grouped by calving date, blocked within group by body weight and body condition score (BCS) and randomly assigned to one of three feeding strategies from calving (day 0) to 60 days postpartum: control cows fed TMR ad libitum (G0; confined cows fed 100 % TMR without access to pasture), pasture grazing with 6 h of access in one session supplemented with 50 % TMR (G1), and 9 h of access in two sessions supplemented with 50 % TMR (G2).
Net energy (NE), but not metabolizable protein (MP), demands for maintenance and/or milk increased in G2 when compared with G1 and G0 cows, respectively. However, NE and MP balances were lower in G1 and G2 than G0 cows. Cow BCS at +55 days was greater in G0 than G2 cows and probability of cows cycling during the first month was greater in G0 and G1 than G2 cows. During the postpartum period, non-esterified fatty acids were greater in G1 than G2 and G0 and β-hydroxybutyrate was greater in G1 and G2 than G0 cows. Plasma insulin was greater and insulin-like growth factor (IGF)-I tended to be greater in G0 than G2 cows, leptin was greater in G2 and G0 and adiponectin were greater in G2 cows. Hepatic expression of growth hormonereceptor-1A and IGF1 mRNA decreased while IGF binding proteins 1,2,4,5 and 6 (IGFBP) mRNA as well as mRNA expression of insulin, leptin (LEPRb) and adiponectin-2 receptors increased from pre to postpartum in all cows. However, only hepatic IGFBP6 and LEPRb mRNA were greater in G2 than G0 and G1 cows, respectively.
Metabolic-endocrine profiles of cows with different feeding strategies in early lactation reflected not only changes in milk energy output and energy balance but also in walking and grazing activity. Concentrations of insulin and IGF-I were increased in G0 cows whereas plasma adiponectin and both, insulin and leptin sensitivity were improved G2 cows. Increased NE demands in G2 cows when compared to G1 and G0 cows, implied a metabolic stress that impacted negatively on reproductive function.
在奶牛混合生产系统中，最大化牧草摄入量和全混合日粮（TMR）补充量是用于增加泌乳早期干物质和能量摄入量的管理手段。目的是评估在泌乳早期，自由采食TMR（不放牧）或采用不同放牧策略（一次放牧6小时或分两次放牧共9小时）并结合TMR（干物质摄入量的50%自由采食）和牧草的荷斯坦奶牛的代谢和内分泌特征以及肝脏基因表达。经产奶牛按产犊日期分组，组内按体重和体况评分（BCS）进行区组，从产犊（第0天）到产后60天随机分配到三种饲养策略之一：自由采食TMR的对照奶牛（G0；圈养奶牛，100%采食TMR，无牧草）、一次放牧6小时并补充50%TMR的牧草放牧组（G1）和分两次放牧共9小时并补充50%TMR的组（G2）。
与G1和G0奶牛相比，G2奶牛维持和/或产奶的净能量（NE）需求增加，但可代谢蛋白质（MP）需求未增加。然而，G1和G2组的NE和MP平衡低于G0组奶牛。在+55天时，G0组奶牛的BCS高于G2组奶牛，且G0和G1组奶牛在产后第一个月发情的概率高于G2组奶牛。在产后期间，G1组奶牛的非酯化脂肪酸含量高于G2和G0组，G1和G2组奶牛的β-羟基丁酸含量高于G0组奶牛。G0组奶牛的血浆胰岛素含量更高，胰岛素样生长因子（IGF）-I含量也倾向于更高，G2和G0组的瘦素含量更高，G2组奶牛的脂联素含量更高。从产前到产后，所有奶牛肝脏中生长激素受体-1A和IGF1 mRNA的表达均下降，而IGF结合蛋白1、2、4、5和6（IGFBP）mRNA以及胰岛素、瘦素（LEPRb）和脂联素-2受体的mRNA表达均增加。然而，仅G2组奶牛肝脏中的IGFBP6和LEPRb mRNA分别高于G0和G1组奶牛。
泌乳早期不同饲养策略奶牛的代谢-内分泌特征不仅反映了产奶能量输出和能量平衡的变化，还反映了行走和放牧活动的变化。G0组奶牛的胰岛素和IGF-I浓度升高，而G2组奶牛的血浆脂联素以及胰岛素和瘦素敏感性均得到改善。与G1和G0组奶牛相比，G2组奶牛的NE需求增加，这意味着代谢应激对繁殖功能产生了负面影响。
