Relationship between performance, metabolic profile, and feed efficiency of lactating beef cows
2019
Souza, Luana Lelis | Zorzetto, Mariana Furtado | Ricci, Túlio José Terra | Canesin, Roberta Carrilho | Dias e Silva, Nhayandra Christina | Negrão, João Alberto | dos Santos Gonçalves Cyrillo, Joslaine Noely | Mercadante, Maria Eugênia Zerlotti
Twenty-seven Nellore cow-calf pairs were submitted for feed efficiency testing. The animals were weighed every 21 ± 5 days to obtain metabolic body weight (BW⁰.⁷⁵) and average daily gain (ADG). Subcutaneous fat thickness (SFT; at 20, 83, 146, and 176 days post-calving); milk yield and components (63, 85, and 151 days); levels of glucose, cholesterol, triglycerides, β-hydroxybutyrate, albumin, urea, creatinine, calcium, phosphorus, magnesium, insulin, and cortisol (15, 41, 62, and 124 days); and ingestive behavior were evaluated. Residual feed intake was calculated for the first stage (RFI1; 21 to 100 days post-calving) and the second stage of lactation (RFI2; 100 to 188 days post-calving), and the cows were classified based on RFI1 as most efficient (RFI1 < 0) and least efficient (RFI1 > 0). Negative RFI1 cows consumed 1.3 kg/day of dry matter, or 9.77%, less than positive RFI1 cows. Most- and least-efficient cows did not differ in terms of subcutaneous fat thickness traits and milk yield or energy-corrected milk (ECM). Glucose (P = 0.0785), triglycerides (P = 0.0795), and phosphorus (P = 0.0597) concentrations were higher in the first stage of lactation in most-efficient cows. Maternal characteristics such as calf weight at birth and at 205 days and ADG were similar in most- and least-efficient cows. The most-efficient cows are more economic as they consume less feed for the same level of production.
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