Protein nutrition of the transition cow

by

Henning Lyngsø Foged

M. Sc. agricultural science

Milk yields of transition dairy cows are substantially improved by supplementing them with rumen protected amino acids (RPA). Responses on the milk yields are typically in the level of 1.5 - 2.5 kg per cow per day. Methionine and lysine are the most limited amino acids in the dairy cow metabolism and should be supplemented in amounts of about 30 grams and 15 grams per cow per day respectively. There is typically a gap between need and demand in feed intake of transition cows of averagely 20%, which also affects the cows' ability to synthesise aminoa acids via rumen microbes. The negative protein balance of the transition cow in terms of metabilosable protein (MEP) is up to 600 gram per day in the fresh period within the first 3-4 weeks of the lactation. Automated Precision Supplementation (APS) is the practical and economic way to exploit the knowledge we have about protein supply of the transition cow. Protein is typically the most expensive component of a dairy cow feed ration, but by compensating fresh cows with RPA, the protein level can be reduced in the TMR ration as the demand for protein is less than typically given to cows in mid and late lactation stages.

The lactation cycle of a dairy cow - see Figure 1 - is characterised by a period of around calving, typically from 3 weeks before calving and until about 3 months after calving, where the cow is in negative energy balance (NEB). In that period, cows' intake of their ration is averagely about 20% (with variations) under their nutritional needs for their production, estimated on basis of their typical around 10% weight loss in that period. There are more reasons for the NEB. The foetus is growing exponential in the last part of the pregnancy and physically reduces the volumen of the rumen, and after calving, the cow exposed to social stress, changed feed and general feeling unwell after the calving, while the milk production grows steeply.

This undersupply causes a dysfunctional immune response, oxidative stress and an imbalanced energy metabolism among the cows in the critical transition period of the lactation and increases risks for loss-giving health and reproduction problems (Sordillo and Aitken, 2009). Affected cows have increased mortality rates, apart from negative impacts on their milk yields.

Figure 1: There is a gap between need and intake of feed in the critical transition period of about 20%.

Negative protein balance

Wheras cows' can mobilise energy from body depositions, other nutritive needs cannot be met in the same way. This includes the need for protein, or rather amino acids for absorption in the small intestine. Figure 2 shows the calculated metabolisable protein (MEB) balance of dairy cows in the first weeks after calving.

Figure 2: Calculated metabolisable protein (MEP) balance of 80 Holstein cows (From Bell et. al. (2000))

Literature

• Bell, Alan William, Winfield S. Burhans, Thomas R. Overton. 2000. Protein nutrition in late pregnancy, maternal protein reserves and lactation performance in dairy cows. Proceedings of The Nutrition Society 59(1):119-26 DOI: 10.1017/S0029665100000148
• Foged, Henning Lyngsø. 2015. Praksis omkring mineraltildeling kan forbedres (In English: Mineral supplementation practices can be improved). BOVI, October 2015:28-31. https://microfeeder.com/docs/Bovi_october_page_28-31.pdf
• Heinrichs, Jud. 2016. Total Mixed Rations for Dairy Cows. Penn State Extension article published at https://extension.psu.edu/total-mixed-rations-for-dairy-cows .
• Sordillo L. M. & Aitken S. L. 2009. Impact of oxidative stress on the health and immune function of dairy cattle. Vet Immunol Immunopathol. 2009 Mar 15;128(1-3):104-9