The Response of Altering the Ratio of Dietary Protein to Energy on Growth, Feed Efficiency, and Mammary Developmentin Rapidly Growing Prepubertal Heifers

Abstract

This study was conducted to evaluate the effects of increasing the ratio of dietary protein to energy above National Research Council recommendations on average daily gain, feed efficiency, structural growth, and indirect measurements of mammary growth. Forty-five Holstein heifers were randomly assigned to either a low, medium, or high ratio of dietary crude protein (CP) to metabolizable energy of 46:1, 54:1, and 61:1 g/Mcal, respectively. The ratio of dietary protein to energy was altered by adjusting the concentration of CP with a similar amount of energy across all diets. Heifers were individually fed and began the treatment period at 200 kg of body weight and 28 wk of age. During the 3-wk adaptation period and 20-wk treatment period, all heifers were fed for a daily dry matter intake (DMI) of 2.45% of body weight. Body weight was monitored for two consecutive days each week and was used to adjust the dry matter offered on a weekly basis. The high versus low ratio of dietary protein to energy increased feed efficiency 6%, which resulted in larger heifers that were subsequently fed 3% more DMI over the course of the trial. The increased feed efficiency and DMI increased average daily gain by 9% for the high versus low ratio of dietary protein to energy. For the high versus low ratio of dietary protein to energy, hip width, hip height, wither height, and heart girth growth was increased 13, 16, 18, and 12%, respectively. The heifers fed the high ratio of dietary protein to energy had a lower rate of increased body condition score compared with the heifers fed the low ratio of dietary protein to energy. Teat length growth was used as an indirect measurement of mammary ductal development and was increased by 35 to 38% for heifers on the high versus low ratio of dietary protein to energy. Feeding dietary ratios of protein to energy above NRC recommendations improved feed efficiency and increased average daily gain, structural growth, and mammary development while decreasing body condition scores in heifers between 28 and 48 wk of age.

Rearing strategy and optimizing first-calving targets in dairy heifers: a review

“…It could correct the negative effects of pre-pubertal feeding management and heifers might have better results during first lactation than those fed according to recommendations (Park et al, 1989;Lammers and Heinrichs, 2000). Experiments showed that compensatory growth might have a direct effect on the mammary development of dairy heifers and consequently on milk production (Choi et al, 1997;Ford and Park, 2001).…”

Evaluation of protein supplementation for growing cattle fed grass silage-based diets: a meta-analysis

“…A shortage of rumendegradable feed protein (RDP) has been shown to reduce microbial digestion of carbohydrates (Griswold et al, 2003;Klevesahl et al, 2003), reduce synthesis of microbial protein (Martín-Orue et al, 2000;Griswold et al, 2003), decrease feed intake (Wheeler et al, 2002) and decrease weight gain of growing cattle (Zinn et al, 1994 and. A shortage of absorbed AA by cattle, either because of decreased synthesis of microbial protein or less than required intakes of rumen-undegraded protein (RUP), decreases weight gain of growing cattle (Lammers and Heinrichs, 2000). Even though individual studies have examined the influence of protein supplementation on the intake and performance of growing cattle, limitations in the number of observations and basal diet composition do not allow for definitive conclusions.…”

Consumo, digestibilidade, desempenho, desenvolvimento ponderal e economicidade de dietas com polpa cítrica em substituição ao feno de capim-tifton 85 para novilhas leiteiras

“…Este fato pode ser particularmente importante quando se utiliza polpa cítrica na alimentação de animais em crescimento. Lammers & Heinrichs (2000) verificaram, em novilhas, estreita correlação entre a relação proteína:energia das dietas e a redução na produção de leite ao longo da vida produtiva do animal quando submetido a elevadas taxas de crescimento. Segundo o NRC (2001), o requerimento de proteína depende principalmente do peso corporal do animal, do ganho de peso diário e da digestibilidade da proteína da dieta, sendo que a relação proteína:energia requerida pelos animais pode ser maior em novilhas submetidas a maiores taxas de crescimento.…”