Forage inclusion in calf starter has the best outcome when it is supplemented since 21 days after birth in Holstein calves.

To evaluate the optimum age of straw addition to starter diet on growth of calves, 40 Holstein calves (36.7 ± 4.96 kg) were assigned at 3 days of age to 1 of 4 treatments in a completely randomized design. Dietary treatments (% of dry matter) were as follows: control starter without any wheat straw (WS) inclusion until weaning (WS0); 90% calf starter concentrate (CSC) + 10% chopped WS offered from day 3 of age to weaning (WS3); 90% CSC + 10% chopped WS offered from day 21 of age to weaning (WS21); and 90% CSC + 10% chopped WS offered from day 40 of age to weaning (WS40). After weaning at 60 days of age, all calves received the same diet until finished at day 72 of age. Solid feed intake was affected by treatments whereby either pre- or post-weaning starter intake was greater for calves fed WS (P < 0.01), and WS3 fed calves had lower starter intake compared to WS21 and WS40 (P < 0.01). Weaning weight was the greatest for WS21 treatment compared to other groups (P < 0.01), although all forage fed calves were heavier than WS0 (P < 0.01). Accordingly, average daily gain also showed a similar pattern (P < 0.01). Without any difference at post-weaning, pre-weaning glucose was lowest in WS0 calves (P < 0.01). There were no effects of treatment on number of days that calves experienced a negative health criterion. In conclusion, we concluded that WS inclusion at d 21 of age is recommendable based on weaning and final BW.

Temporal changes in milk fatty acid distribution due to feeding different levels of rolled safflower seeds to lactating Holstein cows.

The objective of this experiment was to follow the time-course changes of the milk fatty acids (FA) and particularly conjugated linoleic acid (CLA), n-3, and n-6 FA in response to feeding whole rolled safflower seed (SS). Eighteen cows were blocked by milk production, days in milk, and parity, and randomly assigned to 1 of 3 diets by replacing whole cottonseed with SS. The control diet contained no SS (SS0), whereas the other diets contained 3% of dry matter as SS (SS3) or 6% SS (SS6). The study was conducted for 8 wk. Cows fed SS produced more milk than SS0, with SS3 producing more milk than SS6, but without a change in milk fat yield or milk fat %. Except for C8:0 FA, changes in milk FA were not observed until the third week of SS feeding. The C8:0 began decreasing during wk 1 of SS feeding and continued to decline to wk 8. Short-chain FA (C6:0 to C11:0) and medium-chain FA (C12:0 to C16:1) concentrations decreased in milk when cows were fed SS, whereas long-chain FA (C18:0 and higher) increased after wk 3. The milk long-chain FA increased from wk 3 until wk 5 and then reached a plateau with little difference between SS3 and SS6, whereas the short-chain FA decreased more in milk from cows fed SS6 than SS3. Total CLA increased slightly less than 5× in milk from cows fed SS compared with SS0. Over the same time frame, n-3 FA declined and n-6 FA increased in the milk from cows fed SS, with no difference between SS3 and SS6. This study indicated that SS fed at 3 and 6% of DM had the potential to increase milk production and the CLA in milk, but with a corresponding increase in n-6 FA.

Protein feeding and balancing for amino acids in lactating dairy cattle.

This article summarizes the current literature as regards metabolizable protein (MP) and essential amino acid (EAA) nutrition of dairy cattle. Emphasis has been placed on research since the publication of the National Research Council Nutrient Requirements of Dairy Cattle, Seventh Revised Edition (2001). Postruminal metabolism of EAA is discussed in terms of the effect on requirements. This article suggests methods for practical application of MP and EAA balance in milking dairy cows.