How Divergence for Feed Efficiency Traits Affects Body Measurements and Metabolites in Blood and Ruminal Parameters on Pre-Weaning Dairy Heifers.

The objectives of this study were: (1) to evaluate feed efficiency indexes and their relationships with body measurements and blood and ruminal metabolites in the pre-weaning period; (2) to determine if such measurements can be used as feed-efficiency markers during the pre-weaning period. Holstein-Gyr heifer calves (n = 36), enrolled between 4 and 12 weeks of age, were classified into two residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9), and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed whole milk (6 L/day) and solid feed ad libitum. Body developments were measured weekly and feed intake (milk and solid feed) daily during the whole period. Blood samples were collected at 12 weeks of age and analyzed for glucose, insulin and ß-hydroxybutyrate (BHB). Samples of ruminal content were collected on the same day and analyzed for pH, NH3-N, and volatile fatty acids (VFA). Among the growth characteristics, only the initial hip width differed between the RFI groups, and withers height differed between the RG groups. Concentration of BHB was greater and glucose: insulin ratios tended to be greater in LE-RG animals. Butyric acid proportions were similar among RFI groups, but tended to be greater for HE-RG than for LE-RG. Overall, correlation coefficients between RFI or RG and blood, rumen, or morphometric markers were low. Thus, it is unlikely that measurements of metabolic indicators, per se, will be useful in the early identification of more efficient animals. Understanding the underlying physiological basis for improved feed efficiency in dairy heifers requires further investigation.

Effect of pelleted vs. ground starter with or without hay on preweaned dairy calves.

The objective of this study was to evaluate the effect of the physical form of starter and inclusion of hay in the diet of preweaning dairy calves on performance, digestibility, ruminal development, and mRNA expression of genes involved in ruminal metabolism. Holstein × Gyr crossbred male calves (n = 38 1day old) were assigned to 3 treatments for 9 weeks: Control (n = 13; pellet starter with 4 mm diameter and 18 mm length and 4% steam-flaked corn), Ground (n = 12; same starter of the control but ground pass through a 4.0 mm sieve), or Ground plus 5% chopped Tifton hay GH (n = 13). All calves were fed 4 L/d of whole milk up to 63 d of age and were abruptly weaned at 64 d of age. Water and diets were offered ad libitum. Samples of ruminal contents were obtained from all animals at 30, 45, and 60 d of age to evaluate pH, ammonia nitrogen, and volatile fatty acids (VFA). At 55 d of age, an apparent digestibility assay was performed using 18 animals (n = 6/ treatment). At 65 d of age, the 18 animals were euthanized to evaluate the development of the digestive tract. The physical form of starter and the dietary inclusion of hay did not influence starter intake (Control 326 g/d, Ground 314 g/d and GH 365 g/d), daily weight gain (Control 541g/d, Ground 531g/d and GH 606g/d), feed efficiency, apparent nutrient digestibility, energy partitioning, nitrogen balance, ruminal pH, ammonia nitrogen concentration, VFA, the development of the digestive tract and the mRNA expression of genes involved in AGV metabolism.

Performance of crossbred heifers in different step-down waste milk-feeding strategies.

The aim of this study was to evaluate the consumption, performance, feed efficiency, glucose concentration, and the cost per kilogram of weight gain of crossbred Holstein-Gyr heifers (n = 33) subjected to one of the three waste milk step-down strategies: 6L-30d/4L-60d/2L-90d (T1), 6L-45d/4L-60d/2L-90d (T2), and 8L-30d/6L-60d/3L-90d (T3). Heifers were weaned at the age of 91 days. Water and starter were provided ad libitum. The average waste milk intake was higher in T3 than in T1 and T2 strategies until 30 days and between 60 and 90 days. The starter intake did not differ among the strategies until 45 days, but it was higher in strategy T1 than in strategy T3 between 60 and 90 days. The waste milk step-down strategy did not influence the total dry matter intake, average daily gain, body weight, and feed efficiency. Glucose concentrations in plasma varied within a range that could be considered normal and were similar among the treatments. The average cost per kilogram of weight gain was the lowest in strategy T1 (US$3.0) compared to that in the other strategies (T2, US$3.2, and T3, US$3.6). The 6L-30d/4L-60d/2L-90d waste milk step-down strategy was the most effective, since it increased the starter intake, led to normal glucose concentrations in plasma, and caused similar weight gain compared with the other strategies; however, it had a lower cost per kilogram.

Comportamento ingestivo de vacas alimentadas com torta de macaúba / Ingestive behavior of dairy cows fed with macauba meal

Avaliaram-se os efeitos de diferentes níveis de inclusão (0, 100, 200 e 300g kg-1 de MS) de torta de macaúba (TM) na produção leiteira e no comportamento ingestivo de oito vacas Holandesas, em dois quadrados latinos 4x4, sendo quatro tratamentos e quatro períodos experimentais. O comportamento ingestivo foi determinado mediante observações visuais, ocorridas durante 24 horas, a intervalos de 5 minutos, para determinação do tempo despendido em alimentação, ruminação e ócio. Embora tenha ocorrido redução quadrática no consumo de matéria seca e na produção de leite com a inclusão de TM nas dietas, a eficiência alimentar (gMS h-1 e gFDN h-1) e a eficiência de ruminação (gMS h-1 e gFDN h-1) foram semelhantes em todos os tratamentos. O tempo total de mastigações (min dia-1), o número de bolos ruminados (n° dia-1), o número de mastigações merícicas (n° dia-1 e n° bolo-1) e o tempo de mastigações merícicas por bolo (seg bolo-1) não apresentaram diferenças. Os resultados permitem concluir que a inclusão da torta de TM na dieta de vacas leiteiras não influencia no comportamento ingestivo dos animais, entretanto, compromete o seu desempenho.

The effects of the macauba meal (MM) inclusion (0, 100, 200 and 300g kg-1 of DM) upon daily milk production and ingestive behavior parameters were evaluated in eight Holstein cows. Animals were randomly allocated to treatments according to a replicated latin square design, with four treatments and four experimental periods. The ingestive behavior was determined by observation, during 24 hours with 5 minutes intervals to determine the time spent in feeding, rumination and idleness. There was a quadratic decrease in dry matter intake and daily milk production with MM inclusion. However, no effects were detected in MM inclusion on the feeding efficiency (gDM h-1 and gNDF h-1) and rumination efficiency (gDM h-1 and gNDF h-1). The total chewing time (min day-1), the number of ruminated (boli day-1), the ruminating chews (n. day-1 and n. boli-1) and the time of ruminating chews boli (sec boli-1) did not show any difference. The MM inclusion in the diet did not influence the ingestive behavior, but reduces the performance of animals.