Performance and nitrogen use efficiency in mid-lactation dairy cows fed timothy cut in the afternoon or morning

Abstract

Shifting cutting from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates in forages. We hypothesized that, compared with a total mixed ration containing timothy baleage and silage cut in the morning (a.m.-cut TIM), a total mixed ration containing timothy baleage and silage cut in the afternoon (p.m.-cut TIM) would improve animal performance and N use efficiency in mid-lactation Holstein cows due to enhanced supply of ruminal fermentable energy. The objective of this study was to compare the effects of p.m.- versus a.m.-cut TIM on milk yield, concentrations and yields of milk components, ruminal metabolism, and plasma concentrations of AA in mid-lactation Holstein cows. Ten (6 ruminally cannulated) primiparous cows averaging 139±13 d in milk and 550±56 kg of body weight, and 6 (2 ruminally cannulated) multiparous cows averaging 128±11 d in milk and 632±57 kg of body weight at the beginning of the experiment, were used in a crossover design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. The concentration of nonstructural carbohydrates (water-soluble carbohydrates plus starch) was numerically greater in the p.m.- versus the a.m.-cut TIM and averaged 13.2±1.06% and 12.2±1.13%, respectively. Treatment × parity effects were observed for milk urea N, feed efficiency, and milk N efficiency, whereas parity effects were observed for nutrient intake, milk yield, and plasma concentration of several essential and nonessential AA. Intakes of dry matter (19.3 versus 18.6 kg/d) and nonstructural carbohydrates (2.56 versus 2.31 kg/d), and yields of 4% fat-corrected milk (23.1 versus 22.2 kg/d), energy-corrected milk (25.0 versus 24.1 kg/d), milk fat (0.91 versus 0.88 kg/d), and milk protein (0.77 versus 0.73 kg/d) were all greatest with feeding p.m.-cut TIM. Milk yield (23.5 versus 22.7 kg/d) tended to increase in cows fed p.m.-cut TIM. The ruminal fermentation profiles and plasma concentrations of AA were mostly unaffected by treatments. However, ruminal valerate (1.01 versus 1.17 mol/100 mol) and plasma Gly (172 versus 188 µM) were lowest with feeding p.m.-cut TIM. Overall, feeding mid-lactation dairy cows a total mixed ration that consisted of p.m.-cut timothy baleage and silage significantly increased dry matter intake and yields of milk, milk fat, and milk protein.

Effect of increasing dietary metabolizable protein on nitrogen efficiency in Holstein dairy cows

“…The MNE averaged 23% in the present study was comparable to the values of 20.5% and 24.7% observed in the studies of Brito et al [26] and Arndt et al [27], respectively. The decreased MNE with increasing MP supplies were in accordance with previous finding [28].…”

Genetic selection for nonstructural carbohydrates and its impact on other nutritive attributes of alfalfa (Medicago sativa) forage

“…It is therefore noteworthy that divergent NSC selection induced favourable changes in both of these two key traits that could promote better alfalfa protein utilization by ruminants and ultimately more milk production for a given forage intake. This assumption is based on cumulating evidence that increasing NSC to CP ratio optimizes the energy/protein balance in forage diet allowing greater efficiency of microbial protein synthesis, superior animal performance and reduced N losses to the environment (Abberton et al., 2008; Brito et al., ,2009, 2016, da Silva et al, 2014). For instance, increases in WSC to CP ratio in alfalfa‐based forage mixtures (da Silva et al., 2013; Simili da Silva et al., 2014), perennial ryegrass ( L. perenne L.) (Miller et al., 2001; Moorby et al., 2006), and grazed grass‐white clover ( Trifolium repens L.) mixed sward (Parsons et al., 2011) improved dairy cow N use efficiency.…”

“…Forage energy supply includes structural carbohydrates (fibre) with relatively low digestibility and nonstructural carbohydrates (NSC), namely, starch and water‐soluble carbohydrates (WSC), which are highly digestible. A high NSC concentration in forage is important for livestock performance as it drives the energy availability for efficient digestion and microbial protein synthesis in the rumen (Berthiaume et al., 2010; Brito et al., 2009, 2016; Shewmaker et al., 2006) and improves the silage quality by increasing the rate of fermentation (Wilkins & Humphreys, 2003). Feeding a high NSC forage has been shown to increase voluntary intake, improve the efficiency of N utilization by rumen microbial populations, increase milk production and minimize environmental issues associated with excretion of urinal ammonia N (Brito et al., 2009, 2016; Shewmaker et al., 2006).…”

“…A high NSC concentration in forage is important for livestock performance as it drives the energy availability for efficient digestion and microbial protein synthesis in the rumen (Berthiaume et al., 2010; Brito et al., 2009, 2016; Shewmaker et al., 2006) and improves the silage quality by increasing the rate of fermentation (Wilkins & Humphreys, 2003). Feeding a high NSC forage has been shown to increase voluntary intake, improve the efficiency of N utilization by rumen microbial populations, increase milk production and minimize environmental issues associated with excretion of urinal ammonia N (Brito et al., 2009, 2016; Shewmaker et al., 2006). Evidence has also been reported that a high NSC concentration improved forage palatability (Burns et al., 2001) and digestibility (Berthiaume et al., 2010).…”

“…However, significant genotype by environment interaction has been reported for NSC concentration in perennial grasses ( Lolium perenne L.) (Ghesquiere & Baert, 2014; Robins & Lovatt, 2016; Sanada et al., 2007). Consequently, to validate the effectiveness of our method of recurrent selection for improved energy concentration in alfalfa, it was important to evaluate the recurrently selected populations over multiple years and at different harvest periods which are known to have a large impact on energy concentration (Brito et al., 2016). The objectives of this study were to evaluate (1) the direct and indirect effects of one cycle of divergent phenotypic selection for NSC concentration on alfalfa nutritive value and (2) the daily and seasonal stability of this selection criterion for breeding programmes.…”