Mammary gland development of dairy heifers fed diets containing increasing levels of metabolisable protein: metabolisable energy

Abstract

This study was conducted to evaluate the development of the mammary gland in Holstein heifers subjected to different dietary metabolisable protein (MP): metabolisable energy (ME) ratios. Twenty-five Holstein heifers (initial body weight (BW) 213±13·5 kg and initial average age 7·8±0·5 months) were divided into five treatments. The treatments were designed to provide MP:ME ratios equal to 33, 38, 43, 48, and 53 g of MP per Mcal of ME. All diets were formulated to have the same energy content (2·6 Mcal ME/kg dry matter). Actual MP:ME ratios were 36·2, 40·2, 46·2, 47·1, and 50·8 g MP/Mcal ME. The experiment was conducted in a randomised block design, while considering initial BW as a blocking factor to evaluate pre- and post-pubertal periods. Block effect was not observed for all variables evaluated; hence it was considered that the diets had the same influence both on pre- and post-pubertal phases. Dry matter and nutrient intake did not change between treatments, excepting protein intake and digestibility. Serum concentrations of insulin-like growth factor 1 increased linearly across treatments. Changes in the pixel brightness of mammary gland ultrasound images, which are associated with lipid content, were significantly influenced by MP:ME ratios in the diet of heifers that were subjected to accelerated growth rates. It is not recommended to use diets of less than 38 g MP/Mcal ME in diets to heifers allowed to gain more than 1 kg/d.

Sugarcane bagasse as exclusive roughage for dairy heifers

“…Heifers receiving the 50:50 (roughage:concentrate) treatment gained 0.70 kg d -1 . According to Albino et al (2015), it is not recommended for Holstein heifers to gain more than 1 kg d -1 in the rearing phase to avoid fat accumulation in the mammary gland; however, for crossbred heifers, the maximum gain has not yet been established. According to several authors, the average daily gain around 0.70 kg d -1 (Abeni et al, 2000;Shamay et al, 2005) is ideal to achieve target milk performance.…”

“…In this case, for Holstein heifers gaining more than 1 kg d -1 , it is not recommended (Albino et al, 2015); however, for crossbred heifers, the maximum gain has not yet been established. Thus, we hypothesized that the establishment of a proper roughage to concentrate ratio, using sugarcane bagasse as exclusive roughage for dairy heifers in the rearing phase could promote the anticipation of the first calving.…”

“…According to Albino et al (2015), several authors have reported a greater rate of gain ; phosphorus, 60 g kg…”

Technical note: Mammary gland ultrasonography to evaluate mammary parenchymal composition in prepubertal heifers

“…With the heifer restrained in a standing position, the lubricated micro-convex transducer was applied to the base of each teat at a 45° angle, in a caudal-to-cranial placement ( Figure 1A). This procedure was obtained from Nishimura et al (2011) and adapted (Albino et al, 2015).…”

Post-weaning feeding levels on feeding behavior, growth and development in Holstein dairy heifers

“…However, if heifers are simultaneously provided with an adequate level of protein this may minimize the adverse effects of feeding a high amount of energy. Recently, ALBINO et al (2015) reported that in prepuberal heifers fed to achieve an ADWG of 1000g, using a low dietary metabolisable protein: metabolizable energy ratio induced an excessive fat accumulation in the parenchymal area of mammary gland compared with higher ratios. This may explain why heifers can achieve higher ADWG than those recommended by ZANTON & HEINRICHS (2005) without having an impaired mammary development (SILVA et al, 2002).…”