Moonsan, Yingluck2022-02-232022-02-232021https://hdl.handle.net/10182/14631New Zealand dairy production is a predominantly pasture-based system, with crops often used as winter feed. Mitigation of N losses to the environment has led to dry cows wintering on low crude protein (CP) crops such as fodder beet (FB), in late gestation. However, there are emerging questions about the low protein offered to late gestation cows fed these crops, which is below recommended feeding standards, that it may have immediate or long term effects on the dam and in particular the in-utero foetus. To address these questions, three experiments were done to evaluate the impact of restricting protein supply to the maternal diet during late gestation on short and long term responses of both dam and offspring. The objective of the first experiment was to examine the effect of restricting protein by up to 45% for 50 days in late gestation on the dam’s performance and the subsequent growth and development of her in-utero foetus. The treatment feeding occurred between week 31 to 38 of gestation, where 190 crossbreed (Holstein x Jersey) non-lactating dairy cows were allocated into two isoenergetic diet treatments; 1) a moderate CP (MCP; 5 kg DM of FB + 5 kg DM of lucerne silage) as a control diet and 2) a low CP (LCP; 5 kg DM of FB + 5 kg DM of maize silage plus straw). Treatment diets offered approximately 120 MJ ME/cow/day at 11.5 MJME/kgDM which provided 7.8 and 13.6% CP to cows in LCP and MCP, respectively. Low CP during late gestation altered the energy/protein balance of the diet but cows apparently consumed 95% (LCP) and 100% (MCP) of ME requirements and were able to maintain BCS throughout the eight-week experiment irrespective of treatment. Serum urea concentration of the MCP cows were higher than the LCP (6.37 vs 1.67 and 5.70 vs 2.41 mmol/L, at week 4 and 8, respectively) (P<0.01) and urinary N excretion was lower in LCP compared with MCP. Low Ca in the LCP diet may result in more health issues during the transition phase and in the subsequent lactation (43 vs 32 interventions for LCP and MCP, respectively, P = NS). There were no evident carryover effects from winter feeding treatments on the consequent milk yield (average 5,147 litres/lactation) or milk composition of the dams. Among the calves, no difference between maternal treatments was observed for average birth LW (33.2±0.66 kg), heart girth (74.1±0.4), neck length (33.8±0.6), spine length (54.4±0.4), wither height (71.0±0.4), hip height (73.1±0.4) and waist circumference (73.2±0.6) (P>0.05). Colostrum composition and colostral IgG level from both treatments were similar. Calf serum protein, albumin, globulin, IgG and EAAs did not differ due to the maternal diet, but early colostrum intake had a significant impact on these parameters. These findings suggest that feeding a low protein supplement with fodder beet during late gestation can be used to reduce urinary N loss without compromising milk yield or calf development. However, any late gestation diet should be used with awareness of mineral requirements to avoid metabolic disorders during the transition phase. The objective of the second experiment was to examine the effect of maternal diet and milk feeding regime on pre-weaning calf response between day 4 and 39 of age, post-weaning growth and first lactation performance. Sixty 4 day old heifer calves from experiment 1 were allocated to a factorial 2 x 2 design, with the first factor being the maternal treatment (LCP and MCP) and the second factor being the milk allowance regime. A commercial calf milk replacer (CMR) was fed twice daily depending on allowances; 1) a conventional regime (CON at the rate of 2 litres/calf/feed or 10% of BW) and 2) high allowance (HA, at the rate of 4 litres/calf/feed or 20% of BW). Calf starter and water were offered ad-lib. Intake of CMR and starter, general health and behaviour and faeces score were recorded daily. There was no significant impact of maternal treatment on pre-weaning growth, stature measurements, weaning weight or average daily growth rate (ADG). Faeces score was not different between maternal or allowance treatment. The HA calves had greater weaning weight (88.0 vs 79.0 kgLW) and overall ADG (0.90 vs 0.75 kg/day) than the CON calves, and these differences were also evident in their stature measurements. There was no carryover benefit from HA on heifer growth rate and ADG after weaning. Fifteen of the 60 heifers continued as replacements in the milking herd, the HA heifers had greater DIM and a tendency for increased milk yield in the 1st lactation compared with CON heifers. There was no effect of maternal treatment on milk yield. These outcomes highlight the importance of pre-weaning nutrition on calf development and long term productivity. There was no evidence of an effect of moderate maternal protein restriction on calf performance. Due to limited numbers of animals in the first and second experiments, the objective of the third experiment was to use a larger database of cows to examine the long term effects of feeding different winter crops, kale or FB, to late gestation cows on the growth and milk production of their offspring. Heifer data from a commercial herd of 300 multiparous dairy cows wintered on kale or FB over three consecutive winters (2012-2014) were collected from Livestock Improvement Corporation’s MINDA™ Live herd-recording software (MINDA) and Livestock Improvement Corporation Ltd (LIC). Effect of maternal diet on heifer growth and production was compared. There was no significant difference between maternal diets on LW of calves which were well managed and, on average, exceeded industry recommended target weights. Overall LW gain of calves from the age of 3 -22 months averaged 0.66±0.006 kg/day and were not affected by the maternal winter feeding regime (P>0.05). The first and second lactation milk yield, milk composition and days in milk of those progeny were also similar across maternal treatments. Average milk yield for the first two lactations was 4,625±59.4 litres with 439.7±4.3 kg milksolids (P>0.05). Percentage of milk protein and fat were similar between treatments at an average of 4.19±0.02 and 4.99±0.04 %, respectively (P>0.05). These results suggest that under conditions of adequate energy, the late gestation feeding regime is unlikely to alter the long term survival, growth and their first two lactation performance of the progeny. Overall, based on the conditions of the present study, feeding FB with low CP supplement to late gestation cows resulted in reduced nitrogen excretion with no apparent adverse effects on either the dam herself or her calf. The cows maintained BCS and achieved high milk yields. There was no significant adverse effect of maternal low protein on short and long term performance of the offspring and passive immunity in colostrum. Also, colostrum management was critical for neonatal survival and later health. A high allowance regime can accelerate pre-weaning ADG and increased weaning LW. These results may suggest that, under the conditions of adequate energy, cows in late gestation have an effective ability to manipulate nutrition to maintain and respond to in-utero foetal requirements. While the small sample size is a limitation of this study, research outcomes in the wider science community support our results that moderate protein restriction of short duration during gestation can be buffered by the dam to avoid lasting negative effects on the progeny.enmaternal nutritionlate gestationcrude proteindairy nutritionfodder beetmaize silagelucerne silagein-utero growthstature measurementsimmunoglobulin Gpassive immunitypre-weaning rearingpost-weaning growthmilk productionrefractometercalf liveweight gaincalvesEffect of feeding high or low protein supplements with fodder beet in late gestation on cow and calf performance : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln UniversityThesisANZSRC::ANSC 701ANZSRC::300301 Animal growth and developmentANZSRC::300303 Animal nutritionhttps://creativecommons.org/licenses/by/4.0/Attribution 4.0 International