Effects of dietary starch allocation on feeding behaviors and production performance of dairy cows under various management scenarios
Creators: Haisan, Jennifer L
Publisher: name: University of Alberta Library
Year: 2024

<p>Despite there being a large body of literature evaluating dietary strategies to support the metabolism of lactating cows, optimum dietary starch allocation, and resulting effects on milking performance and feeding behaviour are still unknown. Therefore, the overall objective of this research was to evaluate the effects of starch provision on ruminal fermentation, feeding behavior and performance of lactating dairy cows.In Chapter 2, 88 primi- and multiparous cows were used to evaluate the effects of feeding a control (CON; 14% starch) or high-starch (HI; 26.1%) prepartum diet fed for 28 ± 3 d prepartum, followed by a high-fiber (HF; 33.8% NDF, 25.1% starch) or high-starch (HS; 27.2% NDF, 32.8% starch) postpartum diet fed for 20 ± 2 d. Cows fed HI had greater DMI, concentrations of insulin and glucose before parturition, and greater plasma NEFA concentration and milk fat yield postpartum. Cows fed HS postpartum had lower plasma NEFA concentrations and serum haptoglobin. Feeding HS postpartum tended to increase milk yield compared to HF for cows fed the CON prepartum diet, but not HI. Overall, feeding a high-starch TMR postpartum may decrease fat mobilization and increase milk production, regardless of prepartum dietary treatment.In Chapter 3, 8 ruminally-cannulated mid-lactation cows were used to evaluate the effects of feeding a high-fiber (F; 33.2% NDF) or high-starch (S; 56.8% starch) pellet, at a low (L; 1kg) or high (H; 3kg) amount twice per day alongside a complementary partial mixed ration (PMR) in a 4 × 4 Latin square design. By design there was a difference in pellet intake between L and H, and PMR intake was reduced when H was fed; however, total DMI tended to be increased when H was fed. Within 3 h following PMR delivery, cows offered S (with a high fiber PMR) consumed less PMR than those offered F (with a high starch PMR). When S was fed, the duration that ruminal pH was below 5.8 was reduced compared to F. These findings suggest that when cows are fed PMR complementary to pellet, feed intake patterns and ruminal fermentation appear to be affected by nutrient composition of the PMR.Combining these findings, I aimed to evaluate the effects of concentrate allowance through an AMS immediately postpartum (Chapter 4). Sixty-six primi- and multiparous cows were fed a low starch prepartum diet for 30 ± 3 d and assigned to 1 of 3 pellet allocations through the AMS: low (LP; 3 kg/d) or high allowances (HP; 8 kg/d) increased at a moderateiii(HPM; increased from 3 to 8 kg over 15 d) or rapid (HPR; increased from 3 to 8 kg/d over 5 d) rate. All cows received the same PMR formulated to meet nutrient requirements at the LP allowance and were offered their dietary treatments to 8 wk of lactation. Cows offered LP reached target intakes by wk 2; however, HP cows, regardless of adaptation did not achieve target intake. Intake of PMR was greater for LP for the first 4 wk of lactation as compared to HP, with no difference in total DMI. Cows offered LP had greater milking frequency, milk yield, and yields of milk fat, protein and lactose as compared to HP, with no difference detected between HPM and HPR. From wk 5 to 8, there was no difference in milking frequency however, milk yield was greater for LP as compared to HP. Offering more of a starch-based pellet to early lactation cows, in excess of what the diet is formulated for, may not improve DMI, milkings per day or milk and milk component yield.In conclusion, it may be possible to feed high starch post-partum diets when cows are fed a conventional TMR, however, when cows are managed with component feeding and milked with AMS, offering greater amounts of high starch pellets may not result in improved milk production or animal performance.</p>