Optimizing dietary rumen-degradable starch to rumen-degradable protein ratio improves lactation performance and nitrogen utilization efficiency in mid-lactating Holstein dairy cows

Panliang Chen; Yan Li; Meimei Wang; Yizhao Shen; Mingchao Liu; Hongjian Xu; Ning Ma; Yufeng Cao; Qiufeng Li; Mahmoud M Abdelsattar; Zhiyuan Wang; Zihan Huo; Shuai Ren; Linqi Hu; Jie Liu; Yanxia Gao; Jianguo Li

doi:10.3389/fvets.2024.1330876

Optimizing dietary rumen-degradable starch to rumen-degradable protein ratio improves lactation performance and nitrogen utilization efficiency in mid-lactating Holstein dairy cows

Front Vet Sci. 2024 Feb 29:11:1330876. doi: 10.3389/fvets.2024.1330876. eCollection 2024.

Authors

Panliang Chen^#^{1

2}, Yan Li^#^{2

3}, Meimei Wang^{1

2

4}, Yizhao Shen^{1

2}, Mingchao Liu^{2

3}, Hongjian Xu^{1

2}, Ning Ma^{2

3}, Yufeng Cao^{1

2}, Qiufeng Li^{1

2}, Mahmoud M Abdelsattar⁵, Zhiyuan Wang^{1

2}, Zihan Huo^{1

2}, Shuai Ren^{1

2}, Linqi Hu^{1

2}, Jie Liu^{1

2}, Yanxia Gao^{1

2

6

7}, Jianguo Li^{1

2

6

7}

Affiliations

¹ College of Animal Science and Technology, Hebei Agricultural University, Baoding, China.
² Key Laboratory of Healthy Breeding in Dairy Cattle (Co-construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Baoding, China.
³ College of Veterinary Medicine, Hebei Agricultural University, Baoding, China.
⁴ Cangzhou Normal University, College of Life Science, Cangzhou, China.
⁵ Department of Animal and Poultry Production, Faculty of Agriculture, South Valley University, Qena, Egypt.
⁶ Hebei Technology Innovation Center of Cattle and Sheep Embryo, Baoding, China.
⁷ Hebei Research Institute of Dairy Industry Technology, Shijiazhuang, China.

^# Contributed equally.

Abstract

The dietary rumen-degradable starch (RDS) to rumen-degradable protein (RDP) ratio, denoted as the RDS-to-RDP ratio (SPR), has been proven to enhance in vitro rumen fermentation. However, the effects of dietary SPR in vivo remain largely unexplored. This study was conducted to investigate the effect of dietary SPR on lactation performance, nutrient digestibility, rumen fermentation patterns, blood indicators, and nitrogen (N) partitioning in mid-lactating Holstein cows. Seventy-two Holstein dairy cows were randomly assigned to three groups (24 head/group), balanced for (mean ± standard deviation) days in milk (116 ± 21.5), parity (2.1 ± 0.8), milk production (42 ± 2.1 kg/d), and body weight (705 ± 52.5 kg). The cows were fed diets with low (2.1, control), medium (2.3), or high (2.5) SPR, formulated to be isoenergetic, isonitrogenous, and iso-starch. The study consisted of a one-week adaptation phase followed by an eight-week experimental period. The results indicated that the high SPR group had a lower dry matter intake compared to the other groups (p < 0.05). A quadratic increase in milk yield and feed efficiency was observed with increasing dietary SPR (p < 0.05), peaking in the medium SPR group. The medium SPR group exhibited a lower milk somatic cell count and a higher blood total antioxidant capacity compared to other groups (p < 0.05). With increasing dietary SPR, there was a quadratic improvement (p < 0.05) in the total tract apparent digestibility of crude protein, ether extract, starch, neutral detergent fiber, and acid detergent fiber. Although no treatment effect was observed in rumen pH, the rumen total volatile fatty acids concentration and microbial crude protein synthesis increased quadratically (p < 0.05) as dietary SPR increased. The molar proportion of propionate linearly increased (p = 0.01), while branched-chain volatile fatty acids linearly decreased (p = 0.01) with increasing dietary SPR. The low SPR group (control) exhibited higher concentration of milk urea N, rumen ammonia N, and blood urea N than other groups (p < 0.05). Despite a linear decrease (p < 0.05) in the proportion of urinary N to N intake, increasing dietary SPR led to a quadratic increase (p = 0.01) in N utilization efficiency and a quadratic decrease (p < 0.05) in the proportion of fecal N to N intake. In conclusion, optimizing dietary SPR has the potential to enhance lactation performance and N utilization efficiency. Based on our findings, a medium dietary SPR (with SPR = 2.3) is recommended for mid-lactating Holstein dairy cows. Nevertheless, further research on rumen microbial composition and metabolites is warranted to elucidate the underlying mechanisms of the observed effects.

Keywords: Holstein dairy cows; lactation performance; nitrogen utilization efficiency; rumen-degradable protein; rumen-degradable starch.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research was financially supported by the earmarked fund for CARS (CARS-36-20, Beijing, China), the Top Talent Project of Hebei Province (6012018, Shijiazhuang, China), Hebei Dairy Cattle Innovation Team of Modern Agro-industry Technology Research System (HBCT2023180207, Shijiazhuang, China), the Key Research and Development Project of Hebei (20326606D, Shijiazhuang, China) and Precision Animal Husbandry Discipline Group Construction Project of Hebei Agricultural University (1090064, Baoding, China).